Triboelectric Nanogenerator Driven Self-Charging and Self-Healing

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Triboelectric Nanogenerator Driven Self-Charging and Self-Healing Flexible Asymmetric Supercapacitor Power Cell for Direct Power Generation Anirban Maitra, Sarbaranjan Paria, Sumanta Kumar Karan, Ranadip Bera, Aswini Bera, Amit Kumar Das, Suman Kumar Si, Lopamudra Halder, Anurima De, and Bhanu Bhusan Khatua ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.8b19044 • Publication Date (Web): 08 Jan 2019 Downloaded from http://pubs.acs.org on January 8, 2019

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ACS Applied Materials & Interfaces

Triboelectric Nanogenerator Driven Self-Charging and Self-Healing Flexible Asymmetric Supercapacitor Power Cell for Direct Power Generation Anirban Maitra, Sarbaranjan Paria#, Sumanta Kumar Karan#, Ranadip Bera, Aswini Bera, Amit Kumar Das, Suman Kumar Si, Lopamudra Halder, Anurima De, and Bhanu Bhusan Khatua* Materials Science Centre, Indian Institute of Technology Kharagpur, Kharagpur-721302, West Bengal, India. # indicates equal contribution of the authors

*Corresponding Author Dr. B. B. Khatua (Email: [email protected]). Materials Science Centre, Indian Institute of Technology, Kharagpur –721302, India. Tel.:+91-3222-283982 1

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ABSTRACT: The expeditious growth of portable electronics has endorsed the researchers to develop self-powered devices that synchronically harvest and store energy. However, it is quite challenging to integrate two distinct phenomena in a single portable device. Here, we emphasize the fabrication of a triboelectric driven self-charging and self-healing asymmetric supercapacitor (SCSHASC) power cell comprised of magnetic cobalt ferrite grown on a stainless steel fabric (CoFe2O4@SS) as positive and iron oxides decorated reduced graphene oxide grown on stainless steel fabric (Fe-RGO@SS) as negative electrodes separated by a KOH soaked self-healing polymer hydrogel electrolyte membrane. The membrane contains Fe3+ cross-linked polyacrylic acid while self-healing carboxylated polyurethane was utilized for encapsulation. Stainless steel fabric (SS) and poly(vinylidene fluoride-cohexafluoropropylene) (PVDF–HFP)/SS impregnated micro-patterned PDMS composite film-strip were employed as positive and negative triboelectric friction layers, accordingly. During mechanical deformation, the SCSHASC harvests electrical energy and subsequently stores it as electrochemical energy for sustainable power supply. The sandwich-type SCSHASC power cell (a supercapacitor unit sandwiched between two parallelly connected high-performance triboelectric nanogenerators) was charged up to 1.6 V within ~ 31 min under periodic compression/stress (F ≈ 17.6 N, f ≈ 3.80 Hz). Furthermore, the SCSHASC# (with two supercapacitor units in series) can instantly powers-up several portable electronic appliances on periodic compression. Thus, the SCSHASC with unique design will be extremely beneficial for self-powered electronics.

KEYWORDS: self-powered; self-charging; self-healing; asymmetric supercapacitor; sandwich-type; triboelectric nanogenerators

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1. INTRODUCTION Cumulative demand for smart portable electronics in the global market has drawn significant research interest in the arena of energy harvesting and storage devices.1-4 Typically, the mechanism of energy harvesting and storage are completely discrete.5 Hence, the concept of integration of two such distinct mechanisms in a single portable device is quite new and challenging. As for energy harvesting and conversion, several harvesting devices have been employed to harvest electricity directly from ambient energies, i.e. solar, mechanical and thermal energies.6-9 Triboelectric and piezoelectric nanogenerators have widely been explored as energy harvesting devices for scavenging mechanical energy.10-15 Triboelectric nanogenerators (TENGs) can scavenge numerous forms of mechanical energies by the coupling effect of contact electrification and electrostatic induction.16-19 The prime benefits of utilizing TENGs are superior output performances, extreme durability, inexpensive and relatively simple design.20 Amongst several approaches to enhance the output of the TENGs, instigation of micro or nanopatterns on the active surface of the triboelectric friction layers,21-23 surface modification of friction layers24 and inclusion of certain dielectric fillers inside the friction layers25 play crucial roles. Conversely, Li-ion batteries26-29 and supercapacitors29-33 are widely employed as energy storage devices where electricity is converted into electrochemical energy for sustainable power supply. Asymmetric supercapacitors (ASCs), one of the auspicious members in the supercapacitor family with immense power densities, wide working potential range and superior cyclic stability, are of great demand in portable electronics.34-36 Also, utilizing high-performance binder-free component electrodes by growing the electroactive materials directly on conductive current collector substrates essentially improves the overall electrical conductivity.37, 38 To mitigate the requirements for flexible electronics, solid–state symmetric and ASCs are employed by sandwiching two flexible supercapacitor electrodes in presence of a solid–state gel electrolyte.39-41 In contrast to liquid electrolytes, solid-state gel electrolytes elude the issues of electrolyte leakage and short-circuit during eternal operations.20, 31

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To integrate the mechanism of energy harvesting and storage, various self-powered systems16, 42-51 have been implemented by scavenging ambient mechanical/bio-mechanical energy to sustainably power-up portable electronics. Currently, researchers are aiming to design flexible and wearable selfpowered devices with improved power density and efficiency by efficaciously integrating flexible energy harvesters with flexible supercapacitors.52 Recently, Wang et al. fabricated a self-charging power unit by integrating stacked TENGs with a supercapacitor unit.53 The device can efficiently convert mechanical energy directly to electrochemical energy. Wen and Sun et al. designed an ultralight and flexible self-charging power unit to scavenge mechanical energy.43 Zhang et al. invented a self-charging power system by integrating flexible supercapacitor and TENG.20 Thus, fabrication of exclusive self-charging power devices has lot of opportunities for advancement. Severe damages during repeated mechanical deformations and electrochemical cycling are the major concern for flexible and wearable self-charging power devices. Particularly, the supercapacitor components permanently fail and reduce the entire device performance over time. This inevitable failure ultimately causes malfunction and diminishes the lifespan of the self-charging power device.54 To evade this limitations, it is worthy to utilize component electrodes, separators that are capable of self-healing or restoring their electrical and mechanical properties inherently after severe damage.55 Nowadays, supercapacitors comprising of self–healable polymer based separators,3 encapsulators56 for easy restoration of mechanical properties and magnetically healable constituent electrodes for the restoration of electrical properties even after several damages are quite significant and promising in flexible and wearable electronics.55 Herein, we demonstrate the facile fabrication of a triboelectric driven self-charging and selfhealing asymmetric supercapacitor (SCSHASC) power cell by judicious integration of a self-healing asymmetric supercapacitor (SHASC) sandwiched between two parallelly connected high-performance triboelectric nanogenerators (HPTENGs). A polished stainless steel fabric (SS) and a poly(vinylidene

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fluoride–co–hexafluoropropylene) (PVDF–HFP)/SS impregnated micro-patterned PDMS composite film-strip have been employed as positive and negative triboelectric friction layers, accordingly, in the HPTENGs. The presence of PVDF–HFP inside the friction layer eventually increases the dielectric constant and surface charge density (SCD) of the composite film while micro-patterned contact surface of the film-strip provides a higher exposed surface area for better friction. Besides, extremely flexible and robust PDMS provides superior output performance even under small extent of deformations.57 As a result, single HPTENG reveals an output voltage (VO) of ~ 274.3 V and a short-circuit current (ISC) of ~ 29.0 µA under periodic compression (F ≈ 17.6 N, f ≈ 3.80 Hz) which are substantially higher than pure PDMS-SS based TENG (VO ≈ 152.3 V; ISC ≈ 8.9 µA at F ≈ 17.6 N, f ≈ 3.80 Hz). On the other hand, the SHASC unit comprised of magnetic cobalt ferrite electrochemically deposited on a polished SS fabric (CoFe2O4@SS) as positive and magnetic iron oxides decorated reduced graphene oxide grown on SS fabric (Fe-RGO@SS) as negative electrodes, separated by a KOH soaked self-healing polymer hydrogel electrolyte membrane comprised of Fe3+ cross-linked polyacrylic acid (Fe3+–PAA). The reason behind choosing spinel CoFe2O4 as positive electrode material are: presence of various oxidation states, improved magnetic properties, excellent electrochemical behavior and cyclic stability.58 Likewise, Fe-RGO (negative electrode) reveals outstanding power density, stability and magnetic behavior owing to the existence of iron oxides (solely Fe3O4 with traces of Fe2O3) in RGO. Later, the entire ASC was encapsulated by self-healing carboxylated polyurethane (CPU). The SHASC exhibits superior electrochemical performance, cyclic stability, flexibility, self-healing features and wide operating voltage window (0–1.6 V). Finally, our SCSHASC power cell instantly converts the applied mechanical energy into electrical energy upon periodic compression and consequently stores it as electrochemical energy for sustainable power generation. Therefore, it reveals dual way charging features i.e. both electrically and mechanically. The SCSHASC can be charged up to ~ 1.6 V within ~ 31 min under periodic compression (F ≈ 17.6 N, f ≈ 3.80 Hz). It can be charged by casual body/limb

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movements (bio-mechanical motions). Furthermore, the SCSHASC# power cell (with two series connected SHASCs sandwiched between two parallelly connected HPTENGs) can instantly power-up portable electronic gadgets upon repetitive compression which is indeed promising for the incessant operation of daily utilized electronics. 2. EXPERIMENTAL SECTION 2.1. Fabrication of PVDF–HFP flakes (Step–I). PVDF–HFP flakes were prepared through a lowcost non-solvent induced phase separation (NIPS) method. At first, 1 g of PVDF–HFP was dissolved in 20 mL DMF and the solution was kept under constant stirring condition for 3 h at a temperature of ~ 70 ºC. Then the PVDF–HFP solution was taken in a syringe (needle dia. ≈ 0.04 mm) and gently sprayed over ~ 15 mL water surface kept in a Petri dish (dia. ≈ 10 cm). During spraying, PVDF–HFP solution rapidly transforms into a thin sponge-type film owing to solvent exchange process in between DMF and water. Finally, the sponge-type PVDF–HFP film was isolated from the Petri dish and dried at ~ 50 ºC for 5 days in hot air oven. The sponge-type film thus obtained was cut into small flakes (area ≈ 0.2 × 0.2 cm2) for fabrication of composite film. 59 2.2. Preparation of (PVDF–HFP)/SS impregnated micro-patterned PDMS composite film-strip and the fabrication of HPTENG (Step–II). A cigarette wrapper (6 × 4 cm2) was adhered inside the cavity (micro-patterned surface/Al-side of the cigarette wrapper was exposed) of an aluminium mould with an inner volume (mould cavity) of ≈ 6 × 4 × 0.2 cm3. The as-prepared PVDF–HFP flakes (~ 3 wt. %) was then uniformly embedded above the patterned surface inside the mould cavity followed by insertion of a polished SS fabric (area ≤ 6 × 4 cm 2) just above the PVDF–HFP flakes. A thin SS wire was connected with SS electrode by soldering. Afterwards, a uniform and transparent mixture of PDMS elastomer and its cross-linker (mixed at 10:1 ratio followed by vacuum-degassing) was gently poured inside the mold cavity under static condition to fill-up the entire mold cavity (including PVDF– HFP and SS electrode) with PDMS mixture, followed by curing in vacuum oven at ~ 90 ºC for 1 h. 6


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Finally, the cured PDMS based composite film (6 × 4 × 0.2 cm3) was peeled-off from the mold. It is noteworthy; the micro-pattern of the cigarette wrapper (Al-side) was replicated on the active surface of the film. This film was referred to as PDMS/PVDF–HFP/SS and employed as negative triboelectric friction layer in HPTENG. On the other hand, a polished SS fabric with an area of 6 × 4 cm2 was directly employed as both the electrode and positive triboelectric friction layer in HPTENG connected with SS wire by soldering. Prior to assembling the two friction layers, the PDMS/PVDF–HFP/SS composite film was bent to an arc shape and attached with a bent transparent polypropylene (PP) sheet (6 × 4 cm2) using adhesive. This arc-shaped structure enhances the performance of HPTENG. Likewise, the SS fabric electrode was attached with a flat PP sheet using adhesive. Finally, the HPTENG device was assembled by merely joining the two PP sheets pre-attached with the respective friction layers and electrodes. The active area of the HPTENG was 6 × 4 cm2 while the gap between the two triboelectric friction layers was 0.6 cm. It is to be stated that each polished SS was washed with de-ionized (DI) water and ethanol for several times using ultrasonication (Model: OSCAR: PR– 250, frequency ≈ 25 kHz, probe tip diameter = 6 mm and power = 250 W), before assimilation. For comparison, similar PDMS based arc-shaped triboelectric nanogenerator (TENG) has been assembled without employing the PVDF–HFP flakes. 2.3. Fabrication of the SHASC and SCSHASC device (Step–III). A quasi-solid-state flexible and self-healable ASC (SHASC) was fabricated by employing magnetic CoFe 2O4@SS (2×2 cm2) as positive and magnetic Fe-RGO@SS (2×2 cm2) as negative electrodes separated by a KOH soaked Fe3+–PAA based self-healing hydrogel electrolyte membrane. The comprehensive preparation of CoFe2O4@SS, Fe-RGO@SS and Fe3+–PAA/KOH hydrogel electrolyte separator are illustrated in section B1 and B2, consequently in Supporting Information. The optimized mass ratio (m+/m) for the positive and negative constituent electrodes was ~ 0.6. Finally, after assembling, the entire system was

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encapsulated by self-healing CPU for protecting the device from abrupt mechanical impacts/shocks and offers good aesthetic appeal. The total thickens of the SHASC was ~ 0.5 cm. The SCSHASC device/power cell was fabricated by assembling a single SHASC unit sandwiched between two parallelly connected HPTENGs. During assembling, the top and the bottom surface of the as-fabricated SHASC unit were adhered to two HPTENGs, where PP sheet protected flat SS electrode sides of the two HPTENGs adhered to both the surfaces of SHASC unit. It is noteworthy; presence of two HPTENGs ultimately improves the triboelectric charging efficiency, while, presence of both CPU and PP layers excludes the possibility of signal interference amongst the SHASC and HPTENGs.20 The complete circuit was made by connecting the two discrete units through a full-wave bridge rectifier. Finally, the entire device was wrapped by a thin layer of PP tape (≈ 0.05 mm thick) without disturbing the actual dimensions of the device. The tape shields the device from malfunctions during abrupt mechanical impacts, abrasions and provides good aesthetic appeal. The dimension of the whole power cell measured under fully compressed state was ~ 6 cm × 4 cm × 0.7 cm. Additionally, another power cell (SCSHASC#) was assembled by efficaciously integrating two SHASC units (connected in series) sandwiched between two parallelly connected HPTENGs to power-up portable electronics. The stepwise preparation/fabrication of the HPTENG unit, SHASC unit and SCSHASC device has been schematically illustrated in Figure 1.

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Figure 1. Schematic for the fabrication of (a) PVDF–HFP flakes (Step–I), (b) HPTENG (Step–II), (c) CoFe2O4@SS, Fe-RGO@SS component electrodes and assembling SCSHASC device (Step–III) for several applications. 9



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3. RESULTS AND DISCUSSION X-ray diffraction (XRD) and X-ray photoelectron spectroscopic (XPS) analyses were employed to determine the crystallographic/structural features of the electroactive materials. The XRD patterns of CoFe2O4@SS, Fe-RGO@SS and blank SS fabric substrate are shown in Figure 2a. As evident, both CoFe2O4@SS (red profile) and Fe-RGO@SS (blue profile) exhibit three intense diffraction peaks at 2θ ≈ 43.5º, 51.0º and 74.5º owing to the presence of (111), (200) and (220) crystal planes of SS (as supported by the black profile).60, 61 In addition, the XRD pattern of CoFe2O4@SS electrode exhibits several moderate to high intensity peaks centered at 2θ ≈ 18.2º, 30.0º, 35.5º, 37.1º, 43.5º, 53.8º, 57.1º, 62.6º, 65.6º, 69.5º, 74.5º, 75.5º and 78.7º corresponds to (111), (220), (311), (222), (400), (422), (511), (440), (531), (620), (533), (622) and (444) crystal planes of spinel cobalt ferrite, accordingly.62, 63 The acquired pattern is well-matched with JCPDS card no. 003–0864. The high intensity peaks suggests crystalline nature of the as-prepared CoFe2O4 grown on SS fabric substrate. In contrast, the diffraction pattern of Fe-RGO@SS reveals several peaks centered at 2θ ≈ 18.5º, 30.1º, 30.2º, 35.2º, 35.5º, 43.7º, 56.9º, 57.4º, 63.1º and 74.5º which are indexed to (011), (112), (200), (121), (103), (004), (231), (321), (224) and (143) planes of Fe3O4, respectively [JCPDS card no. 075–1609]. Additionally, it also displays certain characteristic signatures of Fe2O3 at 2θ ≈ 15.0º, 18.5º and 23.9º indexed to (103), (113) and (203) crystal planes [JCPDS card no. 025–1402]. The intensity of the characteristic peaks for RGO (002) and (100) crystal planes at 2θ ≈ 25.6º and 41.4º are not prominent owing to the existence of high intensity peaks of Fe3O4 which tends to overwhelm the peaks of RGO. The corresponding JCPDS patterns relevant to the electroactive materials are sequentially displayed in Figure 2b. Moreover, the existence of different oxidation states and the chemical composition of as-deposited Fe-RGO have further been explored by employing XPS. The survey scan profile of Fe-RGO (Figure 2c) reveals the co-existence of C 1s (~ 290.9 eV), Fe 2p (~ 710.4 and 724.8 eV), Fe 3p (~ 55.1 eV) and O 1s (537.6 eV). The narrow scan profiles of Fe-RGO (as revealed in Figure S1a-c, Supporting Information) affirm

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the existence of both Fe2+/Fe3+ and O2– ions. Thus, the existence of mixed iron oxides (solely Fe3O4 with trace of Fe2O3) in Fe-RGO is evident. Additionally, the weigh amount of RGO and iron oxides in Fe-RGO have been estimated by employing Thermogravimetric analysis (as displayed in Figure S1d, Supporting Information). It has been perceived that weigh amount of RGO and iron oxides in Fe-RGO (initial wt. = 9.758 mg) were 4.6834 mg (48 %) and 5.0741 mg (52 %), respectively. Comprehensive surface morphologies/microstructures of the SHASC electrodes and the HPTENG components were investigated by field emission scanning electron microscopy (FE-SEM). Figure 2 (d–i) represents the FE-SEM images of the SHASC component electrodes. As displayed in Figure 2d, wrinkled nanoflakes of CoFe2 alloy electrodeposited on SS (before annealing). The edge thickness of the nanoflakes is ~ 20–30 nm. The FE-SEM images of CoFe2O4@SS after annealing are displayed in Figure 2 (e–g) at different magnifications. It can be perceived from Figure 2e (a low magnification FE-SEM image) that uniform layers of CoFe2O4 were grown on SS fabric substrate after annealing. The overall diameter of a single SS fabric yarn becomes ~ 80 µm after complete wrapping by annealed CoFe2O4. Figure 2f, g represents the FE-SEM images of CoFe2O4 (after annealing) at different magnifications. It has been observed that several interconnected microflowers of CoFe2O4 grown on SS and eventually, the microflowers are congregated together to form an array. The wrinkled nanoflakes of CoFe2 alloy grown on SS fabric (after electrodeposition) were converted to microflower arrays after annealing. The high magnification FE-SEM image (Figure 2g) reveals that the microflowers of CoFe2O4 consist of several ultrathin nanopetals with a thickness of ~ 12–14 nm and are assembled to form large number of cavities with different geometries. This unique interconnected architecture eventually provides a large surface area for sufficient electrode-electrolyte interactions and boosts the ion diffusion kinetics.64 The FE-SEM images of Fe-RGO deposited on SS fabric are portrayed in Figure 2h, i where typical crumpled flake-like architecture of RGO decorated with iron oxides are found to be deposited on SS surface. The thickness of a single RGO nanoflake is ~ 16–20 nm and they are often stacked together to

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construct an assembly with an average thickness ~ 130 nm. This stacked architecture of RGO affords enriched electrode-electrolyte interactions (i.e. adequate contact in-between RGO and the electrolytic ions or adsorption of K+ ions on the surface of RGO) while the presence of iron oxides (decorated on the surface of RGO) concurrently provides excellent magnetic property and pseudocapacitive behavior. Enriched electrode-electrolyte interactions also imply enhanced diffusion of the ions within the interior portions of the stacked microstructure of RGO in Fe-RGO. The porous and stacked flakes of RGO acts like electrolytic ion reservoir. During electrolysis, electrolyte penetrates in the void and contours of the micro-structure. Existing iron oxides on the RGO surface eventually restricts the coalescence of RGO stacked flakes during electrolysis. Figure 2j, k displays the FE-SEM images of PVDF–HFP flakes (HPTENG component) surface acquired at different magnifications. As can be seen, the surface of PVDF–HFP flakes are fairly ruff/uneven and consists of several entangled nanofibres with a dia. ~ 150 nm. This distinctive surface architecture usually provides exposed surface area and improved pressure sensitivity which eventually helps to generate more charges on the surface of the negative triboelectric layer. Figure 2l depicts the FE-SEM image of the micro-patterns replicated on the friction surface of PDMS based triboelectric film-strip (HPTENG component). Introduction of such micro-patterns significantly enhance the effective contact in between the two friction layers and hence the triboelectric surface charge density.

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Figure 2. (a) XRD patterns of as-prepared CoFe2 O4@SS, Fe-RGO@SS and SS fabric electrodes. (b) Relevant JCPDS patterns. (c) XPS survey scan spectrum of Fe-RGO. (d–l) FE-SEM images: (d) CoFe2 alloy@SS before annealing, (e, f, g) CoFe2O4@SS after annealing at different magnifications, (h, i) FeRGO@SS at different magnifications, (j, k) PVDF–HFP surface at different magnifications, (l) typical micro-patterns replicated on the friction surface of PDMS based triboelectric film-strip. The co-existence of Co, Fe, O in CoFe2O4 and C, Fe, O, in Fe-RGO has further been confirmed from the acquired selected area elemental mappings and energy dispersive X-ray (EDX) line spectrum

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of the electroactive materials (Figure S2). The microstructures of the component electrodes acquired after 8000 repetitive galvanostatic charge-discharge (GCD) cycles and after periodic deformations (Figure S3) reveal outstanding electrochemical and structural stability/durability under working conditions. Additionally, the Fourier-transformed infrared (FTIR) and Raman spectroscopic analysis of the electroactive materials have been illustrated in section H, Supporting Information. Complete electrochemical analysis such as cyclic voltammetry (CV), GCD, cyclic stability and electrochemical impedance spectroscopic (EIS) analysis of CoFe2O4@SS within 0–0.6 V (as illustrated in section I, Supporting Information) and Fe-RGO@SS within –1–0 V potential window (as illustrated in section J, Supporting Information) were performed using a three-electrode cell arrangement with 1 M KOH electrolyte. As can be realized, both the electrodes reveal outstanding electrochemical performances. It is noteworthy; introducing trace amount of silver nanoparticles (Ag NPs) eventually improves the conductivity and charge transport property of CoFe2O4@SS (as exposed in Figure S5) while the existence of iron oxides in Fe-RGO enhances the rate capability (Figure S6). Besides, the operating voltage window of the SHASC has been estimated from the CV (at 2 mV/s) and GCD (at 1 A/g) profiles of the positive (CoFe2O4@SS) and negative (Fe-RGO@SS) electrodes (Figure S7). As observed, the SHASC can be operated within 0–1.6 V wide potential window. The comprehensive electrochemical performance of the flexible quasi-solid-state SHASC has been demonstrated through CV and GCD analysis at several conditions. Prior to the electrochemical characterizations, the SHASC was subjected to GCD (at 3 A/g) for ~ 100 cycles till a stable specific capacitance (Csp) is achieved. It is to be stated that the charge balance amongst the two component electrodes obeys the relation: q+ = q–, where q+ and q denotes the amount of charge stored in the positive and negative electrodes, accordingly. Likewise, the quantity of charge (q) stored, the optimum mass ratio (m+/m–) of the two respective electroactive materials has been estimated using equations E1 and E2, in Supporting Information and the optimized mass ratio was ~ 0.6. (The mass of CoFe2O4 and

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Fe-RGO on SS was 0.0157 g and 0.0262 g, respectively.) The CV profiles of the SHASC (Figure 3a) under several working potential window at a scan rate of 2 mV/s clearly indicates that the device can be utilized within a wide voltage range (0–1.6 V) without any deterioration of its charge storage and capacitive behavior.65 The CV curves of the SHASC with variable scan rates of 150, 120, 100, 80, 50, 10, 5, and 2 mV/s within 0–1.6 V are shown in Figure 3b. Typical asymmetric nature of the CV curves at all the scan rates eventually illustrates admirable capacitive behavior of the SHASC. Besides, the nature of the CV curves corroborates a combined electrochemical characteristic (combination of electric double layer and Faradaic behaviors) owing to the existence of two dissimilar electrodes. The nature of the curves remains analogous even at high scan rates, signifying superior rate capability of the device. The comparative CV curves of the SHASC studied under several applied pressure (e.g. heel pressing and finger imparting mode at 2 mV/s) are represented in Figure 3c. The flexibility of the SHASC has also been assessed from the CV profiles under twisting and bending modes. As evident, the nature of the CV curves under several applied conditions remains virtually homologous. The area of the CV profiles remains nearly identical under bending and twisting modes while upon finger imparting and heel pressing, the area increases owing to enhanced electrolyte ion transport through the electrolyte membrane. Figure 3d represents the CV curves of the SHASC upon hand/elbow bending, shoe sole pressing and after 8000 successive GCD cycles at 2 mV/s. The area under the CV curves increases apparently upon elbow bending and shoe sole pressing while the area of the CV profile after 8000 GCD cycles remains virtually analogous (compared to the initial state) signifying superior stability of the power cell. Figure 3e describes the CV profiles of the SHASC during bending at different angles (0º, 30º, 45º, 90º and 135º). Likewise, the area under the CV curves marginally expands with increasing bending angles, suggesting admirable flexibility of the SHASC. Figure 3f displays the GCD profiles of the SHASC under different current densities within 0–1.6 V. Typical asymmetric nature accompanied by a distinct plateau region (during discharge) eventually illustrates

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excellent capacitive behavior of the device. Moreover, all the GCD curves exhibits nearly equivalent voltage plateaus ensuring high reversibility of the ongoing redox process.66 A maximum Csp value of ~ 155.8 F/g, specific capacity (Cs) of ~ 69.25 mAh/g at 1 A/g current density and an areal capacitance (CA) of ~ 810 mF/cm2 at 5 mA/cm2 were obtained using the equations E3, E3a and E4, respectively, Supporting Information. As can be seen from Figure 3g, the calculated Csp still remains up to ~ 122.2 F/g (Cs ≈ 54.3 mAh/g) even at a high current density of 20 A/g, revealing superior rate capability of the device. The GCD curves acquired after 1000, 5000 and 8000 GCD cycles at 1 A/g are shown in the inset of Figure 3g. The nature/shape of the curves remains analogous even after 8000 cycles, endorsing superior stability of the SHASC. Figure 3h shows excellent adherence of the as-deposited electroactive materials with SS current collector. As can be seen, the device retains its outstanding electrochemical performance and rate capability under finger imparting, heel pressing, twisted state, and bending at several angles (15º, 30º, 45º and 90º). At 20 A/g, the SHASC retains ~ 80.3%, 82.3%, 76.3%, and 79.5% of its initial Csp value upon finger imparting, heel pressing, twisted state and bending at 90º, accordingly. Figure 3i illustrates the Csp retention (%) of the SHASC cell under repetitive bending at several angles. At 1 A/g, the device retains ~ 99.7%, 99.3%, 98.9%, 97.9% and 96.3% of its initial Csp even after 100 times repetitive bending at 15º, 30º, 45º, 90º and 135º, respectively, demonstrating outstanding flexibility of the SHASC.5 The GCD curves obtained at 1 A/g during bending at several angles are displayed in the inset of Figure 3i. The nature of the curve remains analogous after 100 times repetitive bending at 135º with merely 3.7% loss of initial Csp. This bendability of the SHASC is essential because during mechanical deformation of the SCSHASC power cell, the internal SHASC unit may also suffer bending. All these acquired outcomes suggest the capability of SHASC to uphold its own electrochemical performance against extreme bending applied during practical utility.

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Figure 3. CV profiles of the SHASC: (a) under three different potential windows at 2 mV/s, (b) at several scan rates, (c) at initial condition, under bending mode, twisted mode, heel pressing and finger imparting conditions at 2 mV/s (Inset depicts heel pressing and twisting on the SHASC), (d) Initially, under hand/elbow bending, shoe sole pressing conditions and after 8000 GCD cycles at 2 mV/s (Inset represents hand/elbow bending and shoe sole pressing), (e) at different bending angles (0º, 30º, 45º, 90º and 135º) at 2 mV/s (Inset represents the photo of bent SHASC). (f) GCD profiles at different current density. (g) Variation of Csp with current densities. (Inset denotes the GCD curves after 1000, 5000 and 8000 consecutive GCD cycles). (h) Variation of Csp with current densities at different conditions e.g. 17



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finger imparting, twisting, heel pressing and bending at different angles. (Inset shows finger imparting and twisting of SHASC). (i) % Csp retention vs. bend times at different bending angles. (Inset depicts the GCD curves of SHASC at several bending angles). The variation of CA with the alteration of current density for the SHASC (Figure 4a) also reveals excellent rate capability with ~ 79% of its initial CA retention even at 100 mA/cm2 current density. The light-weight of the device has also been displayed in the inset. Figure 4b illustrates the Nyquist plots or complex plane impedance profiles: initially, after 1000 and after 8000 GCD cycles. The nature of the profiles is analogous. Each profile comprises of a typical semicircular arc at high-frequency followed by a straight line at low-frequency region. The diameter of the semicircular arc signifies the chargetransfer resistance (Rct) while the slope of the straight line at low frequency signifies resistance towards diffusion of electrolyte ions. A smaller semicircle/arc diameter indicates low Rct while a straight line with higher slope suggests lower ion diffusion resistance. At initial state, the SHASC exhibits an Rct value of ~ 9.5 Ω which is smaller than ~ 10.3 Ω (after 1000 cycles) and 12.0 Ω (after 8000 cycles). Moreover, the initial impedance profile shows a more vertical line (higher slope) at low frequency in comparison to the profiles after 1000 and 8000 cycles, respectively. The lower Rct and ion diffusion resistance of the device suggests better reactivity, faster electrolyte ion transport and decent exposure of the component electrodes towards electrolyte at initial state. After 1000 and 8000 cycles, the R ct and ion diffusion resistance slightly increases owing to increased inherent resistance of the component electrodes.5 Likewise, the device exhibits a solution resistance (intersection of the impedance profile with real impedance axis) of ~ 0.90 Ω (initially), 0.96 Ω (after 1000 cycles) and 1.05 Ω (after 8000 cycles). The solution resistance marginally increases owing to sluggish diffusion of electrolytic ions after repetitive cycling. The equivalent circuit diagram fitted to the initial Nyquist plot is shown in the inset. The GCD cyclic stability measurement of the device was performed at 1 A/g for 8000 cycles within 0–1.6 V (Figure 4c). The interconnected microflowers of CoFe2O4 and stacked flakes-like Fe18


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RGO eventually obstruct the volume expansion during vigorous electrochemical cycling (as supported in Figure S3). Thus, the device exhibits long-term stability against repetitive electrochemical cycling with ~ 93 % of initial Csp retention after 8000 GCD cycles. A moderate increment of Csp value (~ 5.9 %) up to ~ 300 GCD cycles can be attributed to gentle release of electrolyte from the hydrogel membrane and time-dependent diffusion of the electrolytic ions through the inner pores of the electroactive materials. This phenomenon suggests complete utilization of the electrodes surface by the electrolyte after 300 cycles. The incessant GCD profile up to 10 successive cycles (at 1 A/g) is shown in the inset. Figure 4d represents the Ragone plot of the SHASC (variation of energy density with power density). Assessment of the energy and power densities is essential for practical utility. Our SHASC provides a maximum gravimetric energy density of ~ 55.4 Wh/kg at a power density of ~ 800 W/Kg at 1 A/g (calculated by using equation E5 and E6, Supporting Information). The energy density (estimated from the GCDs) still remains at ~ 46.5 Wh/kg even at an immense power density of 8000 W/kg (measured at 10 A/g) which manifests the feasibility of our power cell for realistic applications. A 3D Ragone plot demonstrating the simultaneous variation of energy and power densities with current density is depicted in the inset. A concise comparison of the achieved energy and power densities with analogous systems already published in the literature are tabulated in Table S1, Supporting Information. Additionally, the sustainability/lifespan of the SHASC has been demonstrated in Figure 4e. As can be seen, analogous nature of the CV plots (acquired at 2 mV/s) even after 45 days of device assembling with marginal decrease in the area signifying superior stability of the SHASC and the hydrogel electrolyte separator. Moreover, the voltage window can be extended by serially connecting two or more SHASC. The obtained CV plots at 2 mV/s (Figure 4f) and the GCDs at 1 A/g (Figure 4g) of two serially connected SHASC reveal an extended working voltage window of 0–3.2 V without any deterioration of their inherent nature. All these results evidently illustrate the realistic utility of our SHASC in portable and flexible electronics. Besides, the magnetic response (hysteresis

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loop) of the component electroactive materials has been estimated to corroborate the self-joining phenomenon of the electrodes after cutting/ripping. Figure 4h shows the magnetization hysterics loop of CoFe2O4 at room temperature. The loop specifies the existence of ferromagnetic behavior. 67 As evident; CoFe2O4 shows a saturation magnetization (Ms) value of ~ 97 emu/g at 15 kOe magnetic field accompanied by a residual magnetization (Mr) of ~ 24 emu/g and a coercivity (Hc) of ~ 445 Oe. The room temperature hysteresis loop of Fe-RGO (Figure 4i) also exhibits ferromagnetism with Ms, Mr and Hc values of ~ 56.3 emu/g (at 15 kOe), ~ 2.18 emu/g and ~ 21.0 Oe, accordingly.68

Figure 4. (a) Variation of CA with current densities of SHASC. (Inset shows the light-weight of the device). (b) Nyquist plot of the SHASC: initially, after 1000 and 8000 GCD cycles. (Inset represents 20


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the fitted circuit diagram). (c) Csp retention up to 8000 consecutive GCD cycles at 1 A/g. (Inset depicts the sequential GCD from 1st to 10th cycle at 1 A/g). (d) Ragone plot of the SHASC. (Inset shows the variation of energy and power densities with current density). (e) CV curves of the SHASC (at 2 mV/s) after 2, 5, 10, 15, 30 and 45 consecutive days. (f) CV (at 2 mV/s) and (g) GCD (at 1 A/g) of two serially connected SHASC. Magnetic hysteresis curves of: (h) CoFe2O4 and (i) Fe-RGO at RT. Figure 5a–c sequentially demonstrates the self-joining features of CoFe2O4@SS (+Ve) and FeRGO@SS (–Ve) electrodes after sudden cutting/ripping owing to the existence of permanent magnetic behavior. It is noteworthy; the magnetic response of bare SS fabric is negligible. The electroactive materials with permanent magnetic response (as explored previously) anchored on SS ensures adequate magnetic force that assist self-joining/reconnection of the broken electrodes. As displayed in Figure 5c, one part of the ripped electrode could easily lift-up the other one after damage and ensures reconnection. This classic phenomenon helps to restore the electrical conductivity of the electrodes after damage.55 Figure 5d–g demonstrates the self-healing features of the KOH soaked hydrogel membrane/separator. It has been perceived that the membrane still retains its inherent self-healing characteristics even after 6th healing cycles (Figure 5g). The self-healing behavior of Fe3+–PAA hydrogel membrane can be attributed owing to the existence of strong inter-chain bonding amongst macromolecular PAA chains in presence of Fe3+ ions. Numerous immobilized Fe3+ ions affords ionic cross-linking in between the PAA chains and improves the mechanical strength while the free Fe3+ ions has a tendency to diffuse towards the ripped surface and strongly interact with the abundant carboxylate (COO–) moieties present in the PAA backbones of nearest surfaces, after sudden damage. Likewise, strong inter and intra-molecular H-bonding in between the PAA backbones improves the mechanical and healing properties of the membrane.3 Figure 5h–k demonstrates the typical surface morphological features of the Fe3+–PAA hydrogel separator at different stages of self-healing process. As demonstrated in Figure 5h, the surface of the Fe3+–PAA hydrogel membrane is moderately ruff. 21



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Figure 5i portrays the FESEM image of the membrane where a notch has been generated intentionally across the thickness. It has been recognized that the notch has been healed partially after ~ 8 min under mild hand pressure at room temperature (Figure 5j). The time required for complete healing is ~ 13–15 min and evidently the surface gains its initial morphology (as exposed in Figure 5k). To validate the synergistic effect of the self-healing components and magnetic electrodes on the electrochemical performance of the device, CV analysis was performed after different healing cycles at 2 mV/s fixed scan rate within a potential window of 0–1.6 V (Figure 5l). The shape of the CV curves remains virtually unaltered even after 6th healing cycles with a gentle diminution in the curve area suggesting superior electrochemical performance retention of the SHASC after several healing cycles. The redox peak positions are also unaffected after several healing. Figure 5m illustrates the GCD profiles of the device acquired after different healing cycles at 1 A/g within 0–1.6 V. As can be realized, the nature of the GCDs remains almost unaltered even after 6th subsequent healing cycles. Fascinatingly, the device retains ~ 97.1%, 93.5%, 91.8% and 91.1% of its original Csp after 1st, 3rd, 5th and 6th consecutive healing cycles. Figure 5n demonstrates the variation of Csp with the number of self-healing cycles. The SHASC still exhibits a Csp value of ~ 142 F/g (Cs ≈ 63.1 mAh/g) after 6th healing cycles. As a result of reconnection of the broken or ripped electrodes through magnetic force of attraction and self-healing features of the separator/encapsulate, the device retains its intrinsic electrochemical performance after several healing cycles (as revealed in the inset). Besides, the EIS analysis after several self-healing cycles (Figure 5o) was performed within 1 MHz–100 mHz. All the impedance spectra exhibit similar nature. The device displays a solution resistance of ~ 14.1 Ω and Rct of ~ 21.5 Ω after 6th healing cycles. Moderate increments in the Rct and diffusion resistance with the healing cycles are probably owing to the lack of proper reconnection between the ripped electrodes. Additionally, the mechanical properties of the KOH soaked Fe3+–PAA hydrogel membrane before damage/wound and after 1st, 2nd, 4th and 6th self-healing cycles have been demonstrated systematically in Figure 5p. As can be realized,

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the mechanical properties of the membrane have been restored after 6th healing cycles. It exhibits an ultimate tensile strength (UTS) value of ~ 268.2 KPa, elongation at break (EB) of 448.5 % and Young modulus (YM) of ~ 0.53 KPa, initially. Surprisingly, the UTS, EB and YM are well maintained at ~ 59.1 %, ~ 86.7 % and ~ 60.4 %, respectively, even after 6 th healing cycles, suggesting the inherent selfhealing features of the KOH soaked hydrogel membrane. Additionally, the stress vs. strain behavior of KOH soaked Fe3+–PAA after 10 and 30 days (Figure S8a) reveals excellent mechanical durability. The swelling ratio (%) of the Fe3+–PAA membrane in aqueous 1 M KOH (calculated by employing equation E7, in Supporting Information) at different immersing time intervals (Figure S8b) reveals that the membrane can reach its maximum swelling ratio after ~ 18 min of immersion in electrolyte medium. The mechanical properties of the CPU encapsulate before damage and after self-healing have also been demonstrated in Figure 5q. As can be seen, CPU restores its mechanical properties even after 6th healing cycles. It exhibits an UTS value of ~ 0.35 MPa, EB of ~ 753 % and toughness of ~ 211.90 KPa, initially. Remarkably, the UTS, EB and toughness are well sustained at ~ 82.8 %, 95.1 % and ~ 77.5 %, respectively, after 3rd healing. Likewise, ~ 85.6 %, 93.8 % and 69.5 % retention of the initial UTS, EB and toughness, accordingly, after 6th healing cycles ultimately validate the inherent selfhealing features of the CPU encapsulate. This inherent self-healing behavior can be due to the formation of strong and reversible intermolecular H-bonds once the ripped interfaces are brought in contact.55 Figure 5r–v demonstrates the self-healing features of SHASC. Figure 5r displays that a single SHASC can attain ~1.6 V before damage. The instantaneous glow of a single red light-emitting diode (LED) is shown in Figure 5s. Figure 5t depicts that the SHASC has been ripped with no output voltage. After proper healing, the device can further achieve ~1.6 V (Figure 5u) and power-up a single red LED (Figure 5v). All these outcomes eventually authorize the mechanical and electrical healing behavior of the supercapacitor unit. The capability of restoring its original electrical, electrochemical and mechanical properties even after severe damage is essential for self-charging device fabrication.

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Figure 5. (a) Photograph of CoFe2O4@SS (positive) and Fe-RGO@SS (negative) electrodes, initially. (b) Electrodes after cutting/ripping. (c) Self-joining of the two respective electrodes through magnetic 24


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attraction (pull-up by own magnetic forces). Demonstration of the self-healing characteristics of KOH soaked Fe3+–PAA hydrogel membrane: (d) initially, (e) just after cutting, (f and g) after 1 st and 6th healing. FE-SEM images of the surface of Fe3+–PAA: (h) initially, (i) just after cutting, (j) after partial healing and (k) after complete healing. (l and m) CV curves (at 2 mV/s) and GCD profiles (at 1 A/g) of the SHASC: before healing, after 1 st, 2nd, 4th and 6th healing cycles. (n) Variation of Csp with healing cycles (Inset displays the picture of SHASC after creation of wound and after frequent healing). (o) Nyquist plot of the SHASC: before healing, after 2 nd, 4th and 6th consecutive healing cycles. Stress vs. strain curves: (p) KOH soaked Fe3+–PAA membrane and (q) CPU encapsulate after different healing cycles. Photographs of the output voltage of the SHASC: (r) initial state, (t) after ripping and (u) after healing. Photographs of a glowing red LED by the SHASC: (s) before cutting and (v) after healing. The output performances of the as-fabricated arc-shaped HPTENG unit under different periodic compressive force have been investigated methodically. As described earlier, our HPTENG comprises of two triboelectric friction layers: polished SS fabric (+ Ve) and PVDF–HFP/SS impregnated micropatterned PDMS film-strip (– Ve). An average output voltage (VO) of ~ 274.3 V (Figure 6a) and a short-circuit current (ISC) of ~ 29.0 µA (Figure 6b) were generated by a single HPTENG under periodic finger imparting/tapping state at F ≈ 17.6 N, contact pressure (σ) ≈ 7.34 KPa and f ≈ 3.80 Hz. (F and σ values are calculated from equations E8, E9 and E10, accordingly, Supporting Information). When a compressive force/pressure is applied on the arc-shaped HPTENG, the two-component triboelectric friction layers come in contact followed by electron transfer from less electronegative SS surface to the high electronegative PDMS composite film-strip surface (according to the triboelectric series). Upon removal of the force, a positive voltage and current response can be obtained whereas on further pressing; it generates a negative voltage and current response. Thus, the HPTENG instantly generates alternating currents (AC) upon periodic compression. The inset of Figure 6b represents the real image of finger imparting on the arc-shaped HPTENG with an active area of 6 × 4 cm2. Furthermore, a single 25



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HPTENG can instantly produce an average VO of ~ 42.5 V (Figure 6c) and ISC of ~ 4.4 µA (Figure 6d) under repeated heel pressing at F ≈ 13.4 N, f ≈ 2.40 Hz. The inset of Figure 6d signifies heel pressing on HPTENG. The variation of VO with increasing imparting frequency for the HPTENG has been demonstrated in Figure 6e. Evidently, it exhibits admirable output performance within a wide range of applied frequency (2–10.2 Hz) under constant F ≈ 17.6 N. The applied frequency range coincides with the frequency of HPTENG excitation. An instant VO of ~ 191.0, 274.3, 355.0, 368.0 and 378.0 V were produced by HPTENG at f ≈ 2.0, 3.8, 5.4, 8.1 and 10.2 Hz, accordingly. Under elevated magnitude of applied frequency, the VO increases (first abruptly and then moderately) owing to a prompt attainment of equilibrium state by the electrons flowing through external circuit.20 The variation of VO and power densities of HPTENG with the load resistance is shown in Figure 6f. As can be seen, the VO value increases with increasing the electrical load resistance, and ultimately reaches a saturation point (VO ≈ 274.3 V) when the load resistance is 10 MΩ (green curve). Consequently, the instant output power density value (calculated by using equation E11, Supporting Information) reaches a maximum of 313.5 µW/cm2 when the load resistance increases to 10 MΩ (red curve). Thus, the HPTENG is efficacious when the electrical load resistance is noticeably higher. Inset depicts the schematic circuit diagram of HPTENG connected with external load resistance. Besides, an instantaneous VO of ~ 15.4 V was produced by the HPTENG upon repetitive swing machine imparting at f ≈ 4.30 Hz (Figure 6g). To investigate the long-term utility of our HPTENG, durability experiment was executed under repetitive finger tapping (F ≈ 17.6 N, f ≈ 3.80 Hz) and the results are depicted in Figure 6h. It has been perceived that there is no significant loss of VO value (~ 274.3 V) even after 6th week (~ 20 min/week) signifying extreme durability, steady capacitor charging capability and practical utility of the HPTENG. To compare the outcomes of the HPTENG with analogous PDMS based arc-shaped TENG without PVDF–HFP (comprises a polished SS fabric as +Ve and SS impregnated PDMS as –Ve friction layer), the output performance of a single TENG was studied under similar finger tapping condition. An

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average VO of 152.3 V (Figure S9a), ISC of ~ 8.9 µA (Figure S9b) and SCD (QD) value of ~ 5 nC/cm2 (Figure S9c) were generated by a single TENG (6 × 4 cm2) under periodic finger imparting at F ≈ 17.6 N, f ≈ 3.80 Hz. (QD value was calculated by using equation E12, Supporting Information). Similarly, the TENG can produce an average VO of 20.3 V (Figure S9d) and ISC of 3.5 µA (Figure S9e) upon repetitive heel pressing condition at F ≈ 13.4 N, f ≈ 2.40 Hz. The capability of our HPTENG to charge a 22 µF commercial capacitor after rectification through a full-wave bridge rectifier has been revealed in Figure 6i. It is apparent that a single HPTENG can charge the capacitor gently up to 5 V upon continuous 3.5 min of finger tapping (F ≈ 17.6 N, f ≈ 3.80 Hz). The schematic circuit diagram for capacitor charging through a rectifier unit is displayed in the inset. The bridge rectifier converts the harvested alternating current (AC) to direct current (DC) before charging the capacitor.

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Figure 6. (a) Output voltage (VO) generated by single HPTENG upon frequent finger imparting. (Inset represents the magnified signal). (b) Short circuit current (I SC) generated by a single HPTENG upon finger imparting. (Inset shows the photograph of finger imparting on the top of HPTENG). (c) V O and (d) ISC generated by single HPTENG upon frequent heel pressing. (Inset shows the photograph of heel pressing). (e) Output voltage waveforms of a single HPTENG at varying frequencies. (f) Output performances of the HPTENG under various external load resistances. (Inset portrays the schematic circuit diagram). (g) VO generated by the HPTENG upon sewing machine imparting. (Inset shows the photograph of sewing machine imparting). (h) The durability and stability of the HPTENG for several weeks. (i) The charge–discharge profile of a 22 µF commercial capacitor charged by a single HPTENG upon continuous finger imparting. (Inset shows the schematic circuit diagram of capacitor charging). Additionally, a stacked nanogenerator was designed by parallelly connecting two HPTENG units to enhance the output performance. In comparison to a single HPTENG, the stacked device exhibits a higher VO of ~ 419.6 V (Figure 7a), ISC of ~ 51.2 µA (Figure 7b) upon finger imparting at F ≈ 17.6 N, f ≈ 3.80 Hz. The device also exhibits nearly two times higher Q D (32 nC/cm2) than that of a single HPTENG (QD ≈ 17.9 nC/cm2) during finger tapping (Figure S9f). Besides, the influence of PVDF–HFP to enhance the SCD can be estimated by merely comparing Figure S9c and f. A threefold increase in the QD of HPTENG (in comparison to TENG) can be perceived. The VO of the stacked nanogenerator within a frequency range of 2–10.2 Hz under constant F ≈ 17.6 N has been demonstrated in Figure 7c. An instantaneous VO of ~ 371.0, 436.5, 476.0, 490.0 and 495.0 V were generated by the device at f ≈ 2.0, 3.8, 5.4, 8.1 and 10.2 Hz, accordingly. As evident, the V O produced by the device reaches saturation at higher frequency. The switching polarity experiment of a single HPTENG was performed (Figure S10a) to authorize that the V O signals generated solely from HPTENG and not from the measurement unit. The VO signals generated after rectification through a full-wave bridge rectifier have been illustrated in Figure S10b. The HPTENG produces an output DC 28


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voltage of 269 V upon rectification. The variation of VO with increasing applied force for a single HPTENG at a fixed frequency is presented in Figure S10c. An average V O of ~ 185.0, 224.0, 245.0, 267.0 and 274.3 V were produced at F ≈ 9.8, 12.5, 14.6, 16.4 and 17.6 N, accordingly. This phenomenon can be attributed to enhanced contact between two opposite surfaces of the triboelectric friction layers ensuing higher VO upon increasing the magnitude of applied force. Introducing micropatterns on the active surface of the composite film-strip also expands the contact area causing more electrons to flow through external circuit. 69 The capability of our stacked nanogenerator device to charge a 22 µF commercial capacitor after rectification through a full-wave bridge rectifier has been demonstrated in Figure 7d. It is apparent that the stacked device (with two HPTENGs) can efficiently charge the capacitor up to 10 V within ~ 4 min of finger tapping. Since, the quantity of transferred charges is considerably higher in the stacked device (than single HPTENG); it exhibits better charging efficiency. The schematic circuit diagram for capacitor charging through a rectifier unit is displayed in the inset. Thus, the stacked nanogenerator (with two HPTENG units) can efficiently convert ambient mechanical/bio-mechanical energy (e.g. human finger tapping, elbow bending and heel pressing etc.) directly to electricity which can further be utilized to charge the supercapacitors with proper circuit connection.

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Figure 7. (a) VO and (b) ISC generated by the stacked nanogenerator (with two parallelly connected HPTENGs) upon finger imparting. (c) Output voltage waveforms of the stacked nanogenerator at varying frequencies. (d) The charge–discharge profile of a 22 µF commercial capacitor charged by the stacked nanogenerator upon continuous finger imparting. (Inset shows the schematic circuit diagram of capacitor charging). Typical working mechanism of the sandwich-type SCSHASC power cell upon vertical contactseparation has been depicted in Figure S11. The GCD and impedance analysis of SHASC component electrodes after long and repetitive imparting cycles, as illustrated in section P, Supporting Information reveals impressive mechanical stability or durability of the micro-structures of CoFe2O4 and Fe-RGO. The retention of Csp (%) at several bending angles (Figure 8a) of the internal SHASC unit has been investigated. As can be realized, the SHASC retains ~ 99.8%, 99.6%, 99.3%, 99.0%, 98.5%, 98.0% and 97.4% of its initial Csp after 15°, 30°, 45°, 60°, 90°, 120°, and 135° bending, accordingly. Thus, its ability to store charge in bent state can be recognized. The bendability of the SHASC is sequentially 30


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displayed in the inset photographs. It is noteworthy, during mechanical deformation of the SCSHASC through external force/pressure; the internal SHASC unit suffers bending as well. To confirm the stability/bendability of SHASC, we have measured the bending behavior i.e., whether it is capable to maintain its own electrochemical performance against extreme bending/tapping. Figure 8b represents the schematic circuit diagram of SCSHASC power cell employed as sustainable power source. When switch “S1” is turned on and “S2” is off, the device harvest electrical energy on application of repetitive compressive force and consequently utilize the energy to charge the inner SHASC through a rectifier. When switch “S1” turned off and “S2” turned on (after sufficient charge storage) the device acts as sustainable power source to drive portable electronics. Figure 8c and d represent the selfcharging/discharging profiles of the SCSHASC under periodic finger tapping at F ≈ 17.6 N and f ≈ 3.80 Hz. It has been perceived that after ~ 6 min of repetitive tapping, the potential of the device start to rise gently and ultimately reaches to ~ 1.6 V after ~ 31 min of continuous tapping (Figure 8d). It is noteworthy; a bit longer time is required to complete the entire charging process possibly owing to the power limit of the internal HPTENGs and the inherent resistance of the SHASC unit. Upon removal of tapping force, the device discharges steadily and finally discharged back to almost “zero potential” within a discharge time (∆t) of ~ 44 min under ~ 10.5 µA constant discharge current. A tiny plateau region in the discharge profile illustrates the asymmetric nature of the SHASC. Inset photograph reveals power-up of a digital calculator by the device during discharging. The initial self-charging profiles of SCSHASC under varying tapping frequency have been depicted in Figure 8e. As can be seen, the rate of charging increases with increasing of tapping frequency. The device can be charged to ~ 1.35 V within only 16 min under a tapping frequency of 10.2 Hz, signifying outstanding charging efficiency. The effect of varying magnitude of applied force/stress on the charging efficiency of the device under a constant f ≈ 3.80 Hz has been shown in Figure 8f. Upon elevating the magnitude of applied force, the charging time decreases i.e. the device takes lesser time to attain 1.6 V. Besides, the

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initial self-charging profiles under various compressive stresses generated by casual human body movements and sewing machine imparting have collectively been demonstrated in Figure 8g. Profile-I (black) depicts the initial self-charging curve upon repetitive finger tapping at F ≈ 17.6 N and f ≈ 3.80 Hz. The device attains ~ 0.7 V within 17 min under continuous finger tapping. Profile-II (red) and Profile-III (green) show the self-charging curve upon repetitive shoe sole pressing and heel pressing state, individually at F ≈ 13.4 N, f ≈ 2.40 Hz. Upon shoe sole pressing, the device attains 0.5 V while upon heel pressing; it attains ~ 0.42 V within 17 min. Profile-IV (blue) shows the initial self-charging curve upon continuous sewing machine imparting at f ≈ 4.30 Hz. The device attains ~ 0.27 V within 17 min of imparting. Profile-V (brown) depicts the initial self-charging curve upon repeated hand/elbow bending condition. The device attains ~ 0.09 V within 17 min of repeated elbow bending. Insets represent the photographs of finger imparting, shoe sole pressing, heel pressing, elbow bending and sewing machine imparting. To utilize this sandwich-type design especially for high power applications, another power cell (SCSHASC#) has been assembled by integrating two serially connected SHASC sandwiched in between two parallelly connected HPTENGs. Owing to the presence of two internal SHASCs, the SCSHASC# provides higher output voltage. As displayed in Figure 8h, the SCSHASC can be charged up to ~ 1.6 V while the SCSHASC# can be charged up to ~ 2.56 V upon repetitive compression. All these outcomes ultimately corroborate the triboelectric driven self-charging features of the power cell.

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Figure 8. (a) Csp retention (%) of SHASC at different bending angles. (Inset shows the photographs of SHASC bent at several angles). (b) Schematic circuit diagram of the SCSHASC as power source for driving portable electronics. (c, d) Self-charge/discharge profiles of the SCSHASC power cell upon continuous imparting. (Inset photograph reveals power-up of a digital calculator during discharging). Initial charging profiles of the SCSHASC: (e) at different tapping frequencies, (f) under various applied forces, (g) under various compressive stresses produced by human body movements and sewing machine imparting (Insets represent the photos of finger imparting, shoe sole pressing, heel pressing, elbow bending and sewing machine imparting on the device). (h) Self-charging curves of the sandwich-type devices: SCSHASC and SCSHASC# (with two HPTENGs and two SHASC units). (Inset denotes schematic circuit diagram for SCSHASC#). 33



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Figure 9a demonstrates a schematic for the feasible application areas of our SCSHASC. Figure 9b and c represent the photographs of obtained V O by the SCSHASC and SCSHASC# with a rectifier unit (measured by a multimeter). The output power generated by these power cells upon repetitive imparting/compression has been exploited to drive various portable electronic appliances and light-up several commercial LEDs. The SCSHASC# can instantaneously light-up five commercial red LEDs (Figure 9d) and green LEDs (Figure 9e) after repetitive compression. The power cell is also proficient to instantly power-up small electronic display, wrist watch, mobile LED screen and commercial digital calculator (as demonstrated in Figure 9f, g, h, and i). On the basis of these outcomes, it can be inferred that our triboelectrification enabled robust SCSHASC power cell can exert an immense contribution in self-powered multifunctional electronics. The overall features revealed by the SCSHASC# power cell under various applied deformations are demonstrated in three video clips in Supporting Information Videos.

Figure 9. (a) Schematic demonstration for the feasible application areas. (b, c) VO of the SCSHASC and SCSHASC#. (d and e) Instant light-up of five red and green LEDs by the SCSHASC# after 34


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repeated imparting. Instant power-up of several portable electronic gadgets by the power cell: (f) small electronic display, (g) wrist watch, (h) mobile LED screen, and (i) commercial digital calculator. 4. CONCLUSIONS In summary, we propose facile and cost-effective fabrication of a triboelectrification empowered selfcharging power cell that instantly scavenge ambient bio-mechanical energy and thereby store it for sustainable power generation. The sandwich-type power cell consists of two units: one SHASC and two parallelly connected arc-shaped HPTENGs. Owing to the synergistic influence of CoFe2O4@SS and Fe-RGO@SS as positive and negative constituent electrodes with a Fe3+–PAA/KOH self-healing hydrogel electrolyte separator, the SHASC exhibits a wide voltage range (0–1.6 V), Csp of ~ 155.8 F/g (Cs ≈ 69.25 mAh/g) at 1 A/g, energy density of ~ 55.4 Wh/kg, good rate capability and cyclic stability. In addition, the CPU encapsulated internal SHASC unit can rejoin/self-heal even after severe damage/breakage during long and repetitive compressions. On the other hand, both the two parallelly connected HPTENG consists of polished SS fabric as positive and a PVDF–HFP/SS impregnated micro-patterned PDMS film-strip as negative triboelectric friction layers. Owing to the presence of PVDF–HFP inside the composite film-strip and micro-patterns on the friction surface, the QD increases enormously and hence, these robust HPTENGs reveal high output performances upon repetitive compression. Finally, our SCSHASC power cell was charged up to ~ 1.6 V within ~ 31 min of continuous tapping. Intriguingly, the power cell can be charged in dual ways i.e. both electrically and mechanically. The SCSHASC# can instantly powers-up several portable electronic appliances and LEDs. Thus, our eco-friendly, handy and robust SCSHASC power cell with unique design exerts an immense contribution in modern multifunctional electronics.

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ASSOCIATED CONTENTS Supporting Information (SI) Materials details and characterizations, preparation of the asymmetric supercapacitor components and Fe3+–PAA/KOH, utilized equations, XPS and TGA analysis of Fe-RGO, elemental mappings and EDS patterns of CoFe2O4 and Fe-RGO, morphologies of CoFe2O4 @SS and Fe-RGO@SS after 8000 GCD cycles and several finger imparting/tapping cycles, FTIR and Raman spectroscopic analysis, complete electrochemical analysis of CoFe2O4@SS and Fe-RGO@SS, estimation of the working potential range, comparison of Csp, energy/power density of our SHASC with other related outcomes reported in the literatures, mechanical durability and % swelling ratio of Fe3+–PAA/KOH separator, output performances of the TENG upon finger tapping and heel pressing, V O of single HPTENG in reverse connection and rectified condition, working mechanism of the sandwich-type SCSHASC upon vertical contact-separation, GCD and EIS of SHASC component electrodes after repetitive imparting (PDF).

Supporting Information Videos The characteristic self-charging and self-healing features revealed by the SCSHASC# power cell are demonstrated in three video clips (Supporting Video S1, S2 and S3) in Supporting Information Videos. Notes: The authors declare no competing financial interest. ACKNOWLEDGEMENTS We are very much thankful to: 1. Indian Institute of Technology Kharagpur for financial support, 2. Krishnedu Sarkar for his support in current measurements, 3. Sanjeev Kumar Sharma for his support in magnetic measurements and 4. Sayan Ganguly for his support in mechanical property measurements as well.

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List of abbreviations No: (1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12) (13) (14) (15) (16) (17) (18) (19) (20) (21) (22) (23) (24) (25) (26) (27) (28) (29) (30)

Abbreviations Self-charging and self-healing asymmetric supercapacitor Cobalt ferrite grown on a stainless steel fabric Iron oxides decorated reduced graphene oxide grown on stainless steel KOH soaked Fe3+ cross-linked polyacrylic acid Stainless steel fabric Poly(vinylidene fluoride-co-hexafluoropropylene) Polydimethylsiloxane Self-healing asymmetric supercapacitor Carboxylated polyurethane Dimethylformamide Polypropylene Asymmetric supercapacitors High-performance triboelectric nanogenerators Triboelectric nanogenerators Specific capacitance Specific capacity Areal capacity Force Frequency Surface charge density Output voltage Short-circuit current Non-solvent induced phase separation Galvanostatic charge-discharge Silver nanoparticles Saturation magnetization Residual magnetization Coercivity Alternating current Direct current

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Full names SCSHASC CoFe2O4@SS Fe-RGO@SS Fe3+–PAA/KOH SS PVDF–HFP PDMS SHASC CPU DMF PP ASCs HPTENGs TENGs Csp Cs CA F f SCD (QD) VO ISC NIPS GCD Ag NPs Ms Mr Hc AC DC


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REFERENCES (1)

Wang, Y.; Yang, Y.; Wang, Z. L. Triboelectric Nanogenerators as Flexible Power Sources. npj

Flex. Electron. 2017, 1, 10. [DOI:10.1038/s41528-017–0007–8] (2)

Luo, J.; Tang, W.; Fan, F. R.; Liu, C.; Pang, Y.; Cao, G.; Wang, Z. L. Transparent and Flexible

Self-Charging Power Film and Its Application in a Sliding Unlock System in Touchpad Technology. ACS Nano 2016, 10, 8078–8086. (3)

Guo, Y.; Zhou, X.; Tang, Q.; Bao, H.; Wang, G.; Saha, P. A Self-Healable and Easily Recyclable

Supramolecular Hydrogel Electrolyte for Flexible Supercapacitors. J. Mater. Chem. A 2016, 4, 8769– 8776. (4)

Chen, X.; Lin, H.; Chen, P.; Guan, G.; Deng, J.; Peng, H. Smart, Stretchable Supercapacitors.

Adv. Mater. 2014, 26, 4444–4449. (5)

Maitra, A.; Karan, S. K.; Paria, S.; Das, A. K.; Bera, R.; Halder, L.; Si, S. K.; Bera, A.; Khatua,

B. B. Fast Charging Self-Powered Wearable and Flexible Asymmetric Supercapacitor Power Cell with Fish Swim Bladder as an Efficient Natural Bio-Piezoelectric Separator. Nano Energy 2017, 40, 633– 645. (6)

Jeon, N. J.; Noh, J. H.; Yang, W. S.; Kim, Y. C.; Ryu, S.; Seo, J.; Seok, S. I. Compositional

Engineering of Perovskite Materials for High-Performance Solar Cells. Nature 2015, 517, 476–480. (7)

Wu, W.; Wang, L.; Li, Y.; Zhang, F.; Lin, L.; Niu, S.; Chenet, D.; Zhang, X.; Hao, Y.; Heinz, T.

F. Piezoelectricity of Single-Atomic-Layer MoS2 for Energy Conversion and Piezotronics. Nature 2014, 514, 470–474. (8)

Maiti, S.; Karan, S. K.; Lee, J.; Mishra, A. K.; Khatua, B. B.; Kim, J. K. Bio-Waste Onion Skin

as an Innovative Nature-Driven Piezoelectric Material with High Energy Conversion Efficiency. Nano Energy 2017, 42, 282–293. (9)

Yang, Y.; Guo, W.; Pradel, K. C.; Zhu, G.; Zhou, Y.; Zhang, Y.; Hu, Y.; Lin, L.; Wang, Z. L.

Pyroelectric Nanogenerators for Harvesting Thermoelectric Energy. Nano Lett. 2012, 12, 2833–2838. (10) Chun, J.; Ye, B. U.; Lee, J. W.; Choi, D.; Kang, C.-Y.; Kim, S.-W.; Wang, Z. L.; Baik, J. M. Boosted Output Performance of Triboelectric Nanogenerator via Electric Double Layer Effect. Nat. Commun. 2016, 7, 12985. [DOI: 10.1038/ncomms12985] (11) Yang, Y.; Zhou, Y. S.; Zhang, H.; Liu, Y.; Lee, S.; Wang, Z. L. A Single‐Electrode Based Triboelectric Nanogenerator as Self‐Powered Tracking System. Adv. Mater. 2013, 25, 6594–6601.

38


Page 39 of 44 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(12) Wang, Z. L.; Song, J. Piezoelectric Nanogenerators Based on Zinc Oxide Nanowire Arrays. Science 2006, 312, 242–246. (13) Lu, M.-P.; Song, J.; Lu, M.-Y.; Chen, M.-T.; Gao, Y.; Chen, L.-J.; Wang, Z. L. Piezoelectric Nanogenerator Using p-type ZnO Nanowire Arrays. Nano Lett. 2009, 9, 1223–1227. (14) Karan, S. K.; Bera, R.; Paria, S.; Das, A. K.; Maiti, S.; Maitra, A.; Khatua, B. B. An Approach to Design Highly Durable Piezoelectric Nanogenerator Based on Self‐Poled PVDF/AlO‐rGO Flexible Nanocomposite with High Power Density and Energy Conversion Efficiency. Adv. Energy Mater. 2016, 6, 1–12. (15) Paria, S.; Karan, S. K.; Bera, R.; Das, A. K.; Maitra, A.; Khatua, B. B. A Facile Approach To Develop a Highly Stretchable PVC/ZnSnO3 Piezoelectric Nanogenerator with High Output Power Generation for Powering Portable Electronic Devices. Ind. Eng. Chem. Res. 2016, 55, 10671–10680. (16) Zhao, K.; Yang, Y.; Liu, X.; Wang, Z. L. Triboelectrification‐Enabled Self‐Charging Lithium‐Ion Batteries. Adv. Energy Mater. 2017, 7, 1–8. (17) Fan, F.-R.; Tian, Z.-Q.; Wang, Z. L. Flexible Triboelectric Generator. Nano Energy 2012, 1, 328–334. (18) Meng, B.; Tang, W.; Too, Z.-h.; Zhang, X.; Han, M.; Liu, W.; Zhang, H. A Transparent SingleFriction-Surface Triboelectric Generator and Self-Powered Touch Sensor. Energy Environ. Sci. 2013, 6, 3235–3240. (19) Niu, S.; Wang, S.; Lin, L.; Liu, Y.; Zhou, Y. S.; Hu, Y.; Wang, Z. L. Theoretical Study of Contact-Mode Triboelectric Nanogenerators as an Effective Power Source. Energy Environ. Sci. 2013, 6, 3576–3583. (20) Song, Y.; Cheng, X.; Chen, H.; Huang, J.; Chen, X.; Han, M.; Su, Z.; Meng, B.; Song, Z.; Zhang, H. Integrated Self-Charging Power Unit with Flexible Supercapacitor and Triboelectric Nanogenerator. J. Mater. Chem. A 2016, 4, 14298–14306. (21) Zhang, X.-S.; Han, M.-D.; Meng, B.; Zhang, H.-X. High Performance Triboelectric Nanogenerators based on Large-Scale Mass-Fabrication Technologies. Nano Energy 2015, 11, 304– 322. (22) Fan, F.-R.; Lin, L.; Zhu, G.; Wu, W.; Zhang, R.; Wang, Z. L. Transparent Triboelectric Nanogenerators and Self-powered Pressure Sensors based on Micropatterned Plastic Films. Nano Lett. 2012, 12, 3109–3114.

39



Page 40 of 44

(23) Vasandani, P.; Gattu, B.; Wu, J.; Mao, Z. H.; Jia, W.; Sun, M. Triboelectric Nanogenerator Using Microdome‐Patterned PDMS as a Wearable Respiratory Energy Harvester. Adv. Mater. Technol. 2017, 2, 1–9. (24) Han, M.; Yu, B.; Qiu, G.; Chen, H.; Su, Z.; Shi, M.; Meng, B.; Cheng, X.; Zhang, H. Electrification Based Devices with Encapsulated Liquid for Energy Harvesting, Multifunctional Sensing, and Self-Powered Visualized Detection. J.Mater. Chem. A 2015, 3, 7382–7388. (25) Peng, J.; Zhang, H.; Zheng, Q.; Clemons, C. M.; Sabo, R. C.; Gong, S.; Ma, Z.; Turng, L.-S. A Composite Generator Film Impregnated with Cellulose Nanocrystals for Enhanced Triboelectric Performance. Nanoscale 2017, 9, 1428–1433. (26) Dunn, B.; Kamath, H.; Tarascon, J.-M. Electrical Energy Storage for The Grid: A Battery of Choices. Science 2011, 334, 928–935. (27) Thackeray, M. M.; Wolverton, C.; Isaacs, E. D. Electrical Energy Storage for Transportation– Approaching the Limits of, and Going Beyond, Lithium-Ion Batteries. Energy Environ. Sci. 2012, 5, 7854–7863. (28) Balke, N.; Jesse, S.; Morozovska, A.; Eliseev, E.; Chung, D.; Kim, Y.; Adamczyk, L.; Garcia, R.; Dudney, N.; Kalinin, S. Nanoscale Mapping of Ion Diffusion in a Lithium-Ion Battery Cathode. Nat. Nanotechnol. 2010, 5, 749–754. (29) Aricò, A. S.; Bruce, P.; Scrosati, B.; Tarascon, J.-M.; Van Schalkwijk, W. Nanostructured Materials for Advanced Energy Conversion and Storage Devices. Nat. Mater. 2005, 4, 366–377. (30) Simon, P.; Gogotsi, Y. Materials for Electrochemical Capacitors. Nat. Mater. 2008, 7, 845–854. (31) Maitra, A.; Das, A. K.; Bera, R.; Karan, S. K.; Paria, S.; Si, S. K.; Khatua, B. B. An Approach to Fabricate PDMS Encapsulated All-Solid-State Advanced Asymmetric Supercapacitor Device with Vertically Aligned Hierarchical Zn–Fe–Co Ternary Oxide Nanowire and Nitrogen Doped Graphene Nanosheet for High Power Device Applications. ACS Appl. Mater. Interfaces 2017, 9, 5947–5958. (32) Das, A. K.; Bera, R.; Maitra, A.; Karan, S. K.; Paria, S.; Halder, L.; Si, S. K.; Bera, A.; Khatua, B. B. Fabrication of An Advanced Asymmetric Supercapacitor Based on a Microcubical PB@MnO 2 Hybrid and PANI/GNP Composite With Excellent Electrochemical Behaviour. J. Mater. Chem. A 2017, 5, 22242–22254. (33) Sumboja, A.; Foo, C. Y.; Wang, X.; Lee, P. S. Large Areal Mass, Flexible and Free‐Standing Reduced Graphene Oxide/Manganese Dioxide Paper for Asymmetric Supercapacitor Device. Adv. Mater. 2013, 25, 2809–2815.

40


Page 41 of 44 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(34) Wu, Z.-S.; Ren, W.; Wang, D.-W.; Li, F.; Liu, B.; Cheng, H.-M. High-Energy MnO2 Nanowire/Graphene and Graphene Asymmetric Electrochemical Capacitors. ACS Nano 2010, 4, 5835– 5842. (35) Yan, J.; Wang, Q.; Wei, T.; Fan, Z. Recent Advances in Design and Fabrication of Electrochemical Supercapacitors with High Energy Densities. Adv. Energy Mater. 2014, 4. 1–43. (36) Tang, Z.; Tang, C. h.; Gong, H. A High Energy Density Asymmetric Supercapacitor from Nano‐architectured Ni(OH)2/Carbon Nanotube Electrodes. Adv. Funct. Mater. 2012, 22, 1272–1278. (37) Zhang, G. Q.; Wu, H. B.; Hoster, H. E.; Chan-Park, M. B.; Lou, X. W. D. Single-Crystalline NiCo2O4 Nanoneedle Arrays Grown on Conductive Substrates as Binder-Free Electrodes for HighPerformance Supercapacitors. Energy Environ. Sci. 2012, 5, 9453–9456. (38) Pu, J.; Wang, T.; Wang, H.; Tong, Y.; Lu, C.; Kong, W.; Wang, Z. Direct Growth of NiCo 2S4 Nanotube Arrays on Nickel Foam as High‐Performance Binder‐Free Electrodes for Supercapacitors. ChemPlusChem 2014, 79, 577–583. (39) Lu, X.; Yu, M.; Wang, G.; Tong, Y.; Li, Y. Flexible Solid-State Supercapacitors: Design, Fabrication and Applications. Energy Environ. Sci. 2014, 7, 2160–2181. (40) Meng, F.; Ding, Y. Sub‐Micrometer‐Thick All‐Solid‐State Supercapacitors with High Power and Energy Densities. Adv. Mater. 2011, 23, 4098–4102. (41) Wang, X.; Liu, B.; Liu, R.; Wang, Q.; Hou, X.; Chen, D.; Wang, R.; Shen, G. Fiber‐Based Flexible All‐Solid‐State Asymmetric Supercapacitors for Integrated Photodetecting System. Angew. Chem. 2014, 126, 1880–1884. (42) He, X.; Zi, Y.; Yu, H.; Zhang, S. L.; Wang, J.; Ding, W.; Zou, H.; Zhang, W.; Lu, C.; Wang, Z. L. An Ultrathin Paper-Based Self-Powered System for Portable Electronics and Wireless HumanMachine Interaction. Nano Energy 2017, 39, 328–336. (43) Sun, N.; Wen, Z.; Zhao, F.; Yang, Y.; Shao, H.; Zhou, C.; Shen, Q.; Feng, K.; Peng, M.; Li, Y. All Flexible Electrospun Papers Based Self-Charging Power System. Nano Energy 2017, 38, 210–217. (44) Guo, H.; Yeh, M.-H.; Lai, Y.-C.; Zi, Y.; Wu, C.; Wen, Z.; Hu, C.; Wang, Z. L. All-In-One Shape-Adaptive Self-Charging Power Package For Wearable Electronics. ACS Nano 2016, 10, 10580– 10588. (45) Wang, J.; Wen, Z.; Zi, Y.; Lin, L.; Wu, C.; Guo, H.; Xi, Y.; Xu, Y.; Wang, Z. L. Self‐Powered Electrochemical Synthesis of Polypyrrole from the Pulsed Output of a Triboelectric Nanogenerator as a Sustainable Energy System. Adv. Funct. Mater. 2016, 26, 3542–3548.

41



Page 42 of 44

(46) Wang, S.; Lin, Z.-H.; Niu, S.; Lin, L.; Xie, Y.; Pradel, K. C.; Wang, Z. L. Motion Charged Battery as Sustainable Flexible-Power-Unit. ACS Nano 2013, 7, 11263–11271. (47) Luo, J.; Fan, F. R.; Jiang, T.; Wang, Z.; Tang, W.; Zhang, C.; Liu, M.; Cao, G.; Wang, Z. L. Integration of Micro-Supercapacitors with Triboelectric Nanogenerators for a Flexible Self-Charging Power Unit. Nano Res. 2015, 8, 3934–3943. (48) Zou, J.; Zhang, M.; Huang, J.; Bian, J.; Jie, Y.; Willander, M.; Cao, X.; Wang, N.; Wang, Z. L. Coupled Supercapacitor and Triboelectric Nanogenerator Boost Biomimetic Pressure Sensor. Adv. Energy Mater. 2018, 8, 1–8. (49) Dong, K.; Wang, Y.-C.; Deng, J.; Dai, Y.; Zhang, S. L.; Zou, H.; Gu, B.; Sun, B.; Wang, Z. L. A Highly Stretchable and Washable All-Yarn-Based Self-Charging Knitting Power Textile Composed of Fiber Triboelectric Nanogenerators and Supercapacitors. ACS Nano 2017, 11, 9490–9499. (50) Wang, J.; Li, X.; Zi, Y.; Wang, S.; Li, Z.; Zheng, L.; Yi, F.; Li, S.; Wang, Z. L. A Flexible Fiber‐Based Supercapacitor–Triboelectric‐Nanogenerator Power System for Wearable Electronics. Adv. Mater. 2015, 27, 4830–4836. (51) Yi, F.; Wang, J.; Wang, X.; Niu, S.; Li, S.; Liao, Q.; Xu, Y.; You, Z.; Zhang, Y.; Wang, Z. L. Stretchable and Waterproof Self-Charging Power System for Harvesting Energy From Diverse Deformation and Powering Wearable Electronics. ACS Nano 2016, 10, 6519–6525. (52) Pu, X.; Hu, W.; Wang, Z. L. Toward Wearable Self‐Charging Power Systems: The Integration of Energy‐Harvesting and Storage Devices. Small 2018, 14, 1702817. [DOI: 10.1002/smll.201702817] (53) Wang, J.; Wen, Z.; Zi, Y.; Zhou, P.; Lin, J.; Guo, H.; Xu, Y.; Wang, Z. L. All‐Plastic‐Materials Based Self‐Charging Power System Composed of Triboelectric Nanogenerators and Supercapacitors. Adv. Funct. Mater. 2016, 26, 1070–1076. (54) Huang, L.; Yi, N.; Wu, Y.; Zhang, Y.; Zhang, Q.; Huang, Y.; Ma, Y.; Chen, Y. Multichannel and Repeatable Self‐Healing of Mechanical Enhanced Graphene‐Thermoplastic Polyurethane Composites. Adv. Mater. 2013, 25, 2224–2228. (55) Huang, Y.; Huang, Y.; Zhu, M.; Meng, W.; Pei, Z.; Liu, C.; Hu, H.; Zhi, C. Magnetic-Assisted, Self-Healable, Yarn-Based Supercapacitor. ACS Nano 2015, 9, 6242–6251. (56) Wang, S.; Liu, N.; Su, J.; Li, L.; Long, F.; Zou, Z.; Jiang, X.; Gao, Y. Highly Stretchable and Self-Healable Supercapacitor with Reduced Graphene Oxide Based Fiber Springs. ACS Nano 2017, 11, 2066–2074.

42


Page 43 of 44 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(57) Yang, Y.; Zhang, H.; Lin, Z.-H.; Zhou, Y. S.; Jing, Q.; Su, Y.; Yang, J.; Chen, J.; Hu, C.; Wang, Z. L. Human Skin Based Triboelectric Nanogenerators for Harvesting Biomechanical Energy and as Self-Powered Active Tactile Sensor System. ACS Nano 2013, 7, 9213–9222. (58) Sankar, K. V.; Selvan, R. K.; Meyrick, D. Electrochemical Performances of CoFe2O4 Nanoparticles and a rGO based Asymmetric Supercapacitor. RSC Adv. 2015, 5, 99959–99967. (59) Vatanpour, V.; Karami, A.; Sheydaei, M. Central Composite Design Optimization of Rhodamine B Degradation Using TiO2 Nanoparticles/UV/PVDF Process in Continuous Submerged Membrane Photoreactor. Chem. Eng. Process. 2017, 116, 68–75. (60) Xu, Z.; Jiang, D.; Wei, Z.; Chen, J.; Jing, J. Fabrication of Superhydrophobic Nano-Aluminum Films on Stainless Steel Meshes by Electrophoretic Deposition for Oil-Water Separation. Appl. Surf. Sci. 2018, 427, 253–261. (61) Wang, Y.; Northwood, D. O. An Investigation into TiN-Coated 316L Stainless Steel as a Bipolar Plate Material for PEM Fuel Cells. J. Power Sources 2007, 165, 293–298. (62) Liu, L.; Zhang, H.; Mu, Y.; Bai, Y.; Wang, Y. Binary Cobalt Ferrite Nanomesh Arrays as The Advanced Binder-Free Electrode for Applications in Oxygen Evolution Reaction and Supercapacitors. J. Power Sources 2016, 327, 599–609. (63) Xiong,

P.;

Huang,

H.;

Wang,

X.

Design

and

Synthesis

of

Ternary

Cobalt

Ferrite/Graphene/Polyaniline Hierarchical Nanocomposites for High-Performance Supercapacitors. J. Power Sources 2014, 245, 937–946. (64) Gao, Y.; Mi, L.; Wei, W.; Cui, S.; Zheng, Z.; Hou, H.; Chen, W. Double Metal Ions Synergistic Effect in Hierarchical Multiple Sulfide Microflowers for Enhanced Supercapacitor Performance. ACS Appl. Mater. Interfaces 2015, 7, 4311-4319. (65) Sun, S.; Wang, S.; Xia, T.; Li, X.; Jin, Q.; Wu, Q.; Wang, L.; Wei, Z.; Wang, P. Hydrothermal Synthesis of a MnOOH/Three-Dimensional Reduced Graphene Oxide Composite and Its Electrochemical Properties for Supercapacitors. J. Mater. Chem. A 2015, 3, 20944–20951. (66) Wang, Y.; Chen, Z.; Lei, T.; Ai, Y.; Peng, Z.; Yan, X.; Li, H.; Zhang, J.; Wang, Z. M.; Chueh, Y. L. Hollow NiCo2S4 Nanospheres Hybridized with 3D Hierarchical Porous rGO/Fe2O3 Composites Toward High‐Performance Energy Storage Device. Adv. Energy Mater. 2018, 8, 1703453. [DOI: 10.1002/aenm.201703453] (67) Durgaprasad, P.; Hemalatha, J. Magnetoelectric Investigations on Poly (Vinylidene Fluoride)/CoFe2O4 Flexible Electrospun Membranes. J. Magn. Magn. Mater. 2018, 448, 94–99.

43



Page 44 of 44

(68) Zheng, Y.-h.; Cheng, Y.; Bao, F.; Wang, Y.-s. Synthesis and Magnetic Properties of Fe3O4 Nanoparticles. Mater. Res. Bull. 2006, 41, 525–529. (69) Seung, W.; Gupta, M. K.; Lee, K. Y.; Shin, K.-S.; Lee, J.-H.; Kim, T. Y.; Kim, S.; Lin, J.; Kim, J. H.; Kim, S.-W. Nanopatterned Textile-Based Wearable Triboelectric Nanogenerator. ACS Nano 2015, 9, 3501–3509.

TOC (Graphical Abstract)

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Triboelectric Nanogenerator Driven Self-Charging and Self-Healing

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