Flexible Waterproof Rechargeable Hybrid Zinc Batteries Initiated by

Subscriber access provided by University of South Dakota

Article

Flexible Waterproof Rechargeable Hybrid Zinc Batteries Initiated by Multifunctional Oxygen Vacancies-Rich Cobalt Oxide Longtao Ma, Shengmei Chen, Zengxia Pei, Hongfei Li, Zifeng Wang, Zhuoxin Liu, Zijie Tang, Juan Antonio Zapien, and Chunyi Zhi ACS Nano, Just Accepted Manuscript • DOI: 10.1021/acsnano.8b04317 • Publication Date (Web): 24 Jul 2018 Downloaded from http://pubs.acs.org on July 25, 2018

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 30 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

ACS Nano

150x93mm (300 x 300 DPI)

ACS Paragon Plus Environment

ACS Nano 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

Page 2 of 30

Flexible Waterproof Rechargeable Hybrid Zinc Batteries Initiated by Multifunctional Oxygen Vacancies-Rich Cobalt Oxide

Longtao Ma1, Shengmei Chen1, Zengxia Pei1, Hongfei Li1, Zifeng Wang1, Zhuoxin Liu1, Zijie Tang1, Juan Antonio Zapien1, Chunyi Zhi1, 2*

1

Department of Materials Science and Engineering, City University of Hong Kong, 83

Tat Chee Avenue, Kowloon, Hong Kong SAR, PR China. 2

Chengdu Research Institute, City University of Hong Kong, Chengdu, PR China.

*Corresponding Author: Prof. Chunyi Zhi E-mail: [email protected]

1 ACS Paragon Plus Environment

Page 3 of 30 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

ACS Nano

ABSTRACT

Although both are based on Zn, Zn-air battery and Zn-ion battery are good at energy density and power density, respectively. Here, we adopted Ar-plasma to engrave a cobalt oxide with abundant oxygen vacancies (denoted as Co3O4-x). The introduction of oxygen vacancies to cobalt oxide not only promotes its reversible Co-O ↔ Co-O-OH redox reaction, but also leads to good oxygen reduction reaction and oxygen evolution (ORR/OER) performance (a half-wave potential of 0.84 V, four-electron transfer process for ORR and 330 mV over-potential， 58 mV·dec-1 Tafel slope for OER). We then constructed a battery system based on both Zn-Co3O4-x and Zn-air electrochemical reactions. The hybrid battery reveals both a high-power density of 3200 W·kg-1 and highenergy density of 1060 Wh·kg-1. Furthermore, the developed flexible solid-state hybrid battery, demonstrating good waterproof and washable ability (99.2 % capacity retention of after 20 h water soaking test and 93.2 % capacity retention after 1 hour washing test). Interestingly, the fabricated flexible battery can work under water, and after the power is exhausted, the battery can automatically recover electricity output as long as it is exposed to air. The developed device is suitable for wearable applications considering its electrochemical performances, great environmental adaptation and “air recoverability”. In addition, this study underscores the approach to develop hybrid energy-storage technologies through modifying electrode materials.

KEYWORDS: hybrid zinc battery; flexible; multi-roled battery; vacancies-rich; waterproof.


ACS Nano 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

Page 4 of 30

Regarding high-energy conversion efficiency, high-energy density and environmentally friendly warrant attention, Zn-air battery is an important pathway to potable electronics and electric energy infrastructures.1-4 However, low-power density stemming from relative low discharged voltage is one of the major problems of the Zn-air battery system.5-7 The theoretically maximum output voltage for Zn-air battery is only 1.66 V based on electrochemical reaction of zinc oxidation and oxygen reduction in alkaline

8-11 condition (Zn + 4 → (

On + 2 ; + 4 + 2 → 4 .

the other hand, as an “air-battery”, the usage scenarios are also limited.12, 13 For example, as a semi-closed system, it cannot work under oxygen-free environment, such as under water, sealing and vacuum conditions. In view of practical application for portable electrics or other electronic device, the battery system ought to satisfy the requirement of serving in various external conditions,13-16 including the oxygen-free conditions. Among the many Zn-based battery systems, aqueous Zn-Co3O4 battery exhibits highoperating voltage, high capacity and ease of fabrication. More importantly, compared with the Zn-air battery, it can serve in more scenarios, including the oxygen-free environments.

17, 18

Whereas, aqueous Zn-Co3O4 battery is limited by relatively low

energy density and restricted energy release, leading to that the battery cannot continuously power electric device for a long time when charger is not available. To solve these problems, integrating multiple electrochemical reactions in one system has been demonstrated for hybridizing supercapacitor and battery to achieve both high energy and power density.19-25 Considering the fact that Zn-air battery and Zn-Co3O4 battery are complementary in terms of many aspects, including energy density, power density, usage scenario and voltage output, it would be desirable to integrate these two systems. The


Page 5 of 30 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

ACS Nano

resulted hybrid system may simultaneously possess various merits including high energy and power density, high voltage and workability both in air and under water. These merits result from fast Faradaic redox reactions of (Co-O ↔ Co-O-H) in a Zn-Co3O4 battery and reversible ORR/OER in Zn-air battery. However, it is difficult to achieve a single component of electrode material with dual-functions simultaneously (charge storage and catalytic activity). The electrocatalytic activity of Co3O4 is significantly affected by its surface area and electronic states. The surface areas and the electronic states of Co3O4 could be tuned by oxygen vacancies. Therefore, the electrocatalytic activity of Co3O4 can potentially be improved by introduction of oxygen vacancies. In addition, the oxygen vacancies may also enhance the electrochemical performance of ZnCo3O4 battery, owing to a lager surface area for redox reaction. These effects could promote good performances of this hybrid zinc battery. In this contribution, we demonstrate a solid-state rechargeable and washable hybrid Znbattery with high water-retaining polyacrylamide (PAM) hydrogel electrolyte and highefficient dual-functional cathode of oxygen vacancies rich-cobalt oxide of Co3O4-x. The Co3O4-x is produced by Ar plasma-engraving conventional Co3O4 to expose more surface sites and introduce abundant oxygen vacancies. As a result, the Co3O4-x shows good ORR and OER ability, together with an improved redox electrochemical performance. The multifunctional Co3O4-x provides a Zn-based battery with two electrochemical processes: process I, first plateau at 1.92 V from Co-O-H → Co-O Faradaic redox reaction， and process II, second plateau at 1.25 V resulting from ORR reaction. The Zn-Co3O4/-air hybrid battery offers both high voltage of 1.9 V, high-power density of 3200 W·kg-1, high-energy density of 1060 Wh·kg-1 and long-cycling stability of 440 hours for 1500


ACS Nano 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

Page 6 of 30

cycles. More importantly, the solid-state hybrid battery exhibits good safety and wearability,

demonstrating

good

waterproof

and

washable

capability.

The

electrochemical performance maintains above 90 % after soaking in water for 20 h or washing in water for 1 h. The flexible solid-state hybrid battery can work in oxygen-free environments, such as under water (battery mode) or in oxygen-exposure environments (dual mode), exhibiting great environmental adaptation. RESULTS AND DISCUSSION Materials synthesis and characterization Co3O4, although have been used as cathode in Zn-ion batteries, it cannot support ORR and OER, both of which are essential for reversible Zn-air batteries. It has been noted that oxygen vacancies can endow a significant effect on materials’ electrocatalytic activity and electrical conductivity, owing to its role as shallow donors and increased carrier concentration.26-29 Therefore, we intend to create more oxygen vacancies in the prepared Co3O4.30, 31 The Co3O4 with oxygen vacancies (denoted as Co3O4-x) was prepared by Arplasma treatment to hydrothermally synthesized Co3O4 (Figure 1a). The X-ray diffraction (XRD) pattern for the Co3O4-x can be indexed to cubic spinel-Co3O4, in great agreement with JCPDS No. 43-1003 (Figure S1). The XRD results imply that the Ar-plasma treatment didn’t change its pristine crystal structure. Notably, the broad reflection peak at around 26o is assigned to carbon fibre cloth (CFC) substrate. The intensity of this peak is obvious weaker than the features of Co3O4, indicating that the Co3O4 nanorod is well spread on the CFC substrate. The morphology and size of Co3O4 and Co3O4-x were evaluated by scanning electron microscopy (SEM) shown in Figure 1b, c. The nanorods are around 100 nm in diameters and 2-3 µm in length. Intriguingly, several nanorods


Page 7 of 30 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

ACS Nano

assemble to form a bundle and spread on the CFC substrate homogeneously. After the 30-min Ar-plasma treatment, the morphology of nanorod is basically reserved, while a rougher surface with irregular pits is observed (Figure 1c). This is significantly different from the smooth surface of Co3O4 (Figure 1b), indicating the plasma treatment can effectively etch the nanorods. X-ray photoelectron spectroscopy (XPS) was applied to characterize the oxidation of Co atoms and the surface properties of Co3O4 nanorods before and after Ar-plasma treatment. The high-resolution Co 2p spectra are fitted to investigate the electronic states of Co atoms with different valences (Figure 1 d, f).32, 33 The peaks at 779.5 eV is attributed to Co3+ while the peak at 780.8 eV is attributed to Co2+.33, 34 The relative intensities of the Co2+ and Co3+-related peaks are used to calculate the relative atomic ratio of Co2+/Co3 on the surface of Co3O4. After Ar-plasma treatment, the relative atomic ratio of Co2+/Co3+ increases from 1.002 to 1.314 achieved by calculating the area of the fitted curves covered. It manifests more Co2+ in Co3O4-x, suggesting that oxygen vacancies are generated after the Ar-plasma treatment. The fine-scanned O 1s core level spectra further confirms the existence of oxygen vacancies. In O 1s core level spectra, the peaks at 529.8 eV and 531.2 eV are typical for Co-O bonds and hydroxyl species of surface-adsorbed water molecules,35,

36

respectively. While, the peak at 531.8 eV is assign to surface

oxygen defect species induced by Ar-plasma reduction reaction, confirming the existence of oxygen vacancies in Co3O4-x. The ratio of oxygen vacancies is calculated to be 7.51 at. %, according to the calculated changes of the ratio of Co2+-O/Co3+-O in Co3O4-x electrode materials. XPS results attest that Co3+ is partially reduced to Co2+ in process of Ar-plasma treatment, creating abundant oxygen vacancies on the surface of Co3O4-x.


ACS Nano 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

Page 8 of 30

Whereas, the crystal phase of Co3O4-x does not change compared to Co3O4 confirmed by XRD characterization. The abundant oxygen vacancies in Co3O4-x nanorods may create more electrochemically active sites, which could highly enhance electrocatalytic activity of ORR and OER. Meanwhile, previous researches report that defect states of the band gap in Co3O4 derived from oxygen vacancies and the two electrons easily excited on the defect states could highly improve electrical conductivity of Co3O4.37

Figure 1. (a) Schematic illustration of synthesized procedure of oxygen vacancies-rich cobalt oxide. SEM images of (b) pristine Co3O4 and (c) Co3O4-x. High-resolution (d) Co 2p and (e) O 1s XPS spectrum for pristine Co3O4. High-resolution (f) Co 2p and (g) O 1s XPS spectrum for Co3O4-x.


Page 9 of 30 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

ACS Nano

ORR and OER performance The electrochemical performance of Zn-air battery is determined by electrocatalytic activity of the air-electrode. To investigate the electrocatalytic ORR and OER performance of Co3O4-x, the cyclic voltammogram (CV), linear sweep voltammetry (LSV) curves and RRDE measurement were carried out in alkaline medium (0.1 M KOH). To highlight the utility of oxygen vacancies on electrocatalytic activity, the obtained cobalt oxides that are rich (Co3O4-x) or poor (Co3O4) in oxygen vacancies were tested. As required to investigate kinetic process, the active materials were scraped from freestanding electrode for testing. As shown in Figure 2a, the Co3O4 and Co3O4-x show sharp reduction peaks in O2-saturated 0.1 M KOH aqueous solution, suggesting an evident oxygen reduction process. While, the reduction peak for Co3O4-x at 0.81 V (vs. RHE), significantly positive than that of Co3O4 (0.69 V), suggesting stronger ORR capability after introduction of oxygen vacancies. The LSV curve shown in Figure 2b exhibits the catalytic performance of Co3O4-x with a positive onset potential of 0.98 V, a half-wave potential of 0.84 V and the limiting current density of the about 5.85 mV·cm-2 at a 0.2 V potential, which outperforms that of pristine Co3O4 electrocatalyst. The ORR catalytic activity is further evaluated by calculating the electron transfer number and the peroxide yield from RRDE test shown in Figure 2c. The RRDE test for Co3O4-x catalyst show a quasi-four-electron transfer process (above 3.8) and the yield of HO2- is below 10%, demonstrating an essential enhancement of ORR activity by introducing oxygen vacancies in Co3O4-x. A negligible difference can be observed even after 5000 CV cycles (Figure S2), suggesting a long-term cycling stability of Co3O4-x. Therefore, the Ar-plasma


ACS Nano 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

Page 10 of 30

treatment executes evident oxygen deficiencies facilitating catalytic performance of Co3O4-x in terms of limiting currents, potentials, durability and electrons transferred. With regards to the OER electrocatalytic activity shown in Figure 2d, Co3O4-x exhibits a 330 mV over-potential at 10 mA·cm-2, which is much smaller than the pristine Co3O4 (450 mV). The corresponding Tafel slopes shown in Figure 2e were calculated from the polarization curves of Figure 2d to study the OER catalytic kinetics of the electrocatalysts. Co3O4-x exhibits a Tafel slope of 58 mV·dec-1, much lower than that of Co3O4 (220 mV·dec-1), which suggests significantly improved OER kinetics of the Co3O4-x catalyst. In addition, negligible differences can be observed even after 5000 CV cycles (Figure S3), indicating the good durability of the Co3O4-x nanorods. The overall electrocatalytic activities of the electrocatalysts were evaluated by the over-potential of OER at 10 mA·cm-2 and half-wave potential of ORR. As shown in Figure 2f, Co3O4-x catalyst exhibits a low oxygen electrode activity (∇) of about 0.72 V, which is much smaller than pristine Co3O4 (1.0 V). The good electrocatalytic activity is ascribed to abundant catalytically active sites supplied by Co3O4-x and improved conductivity, owing to numerous oxygen vacancies formed in Co3O4-x. The Co3O4-x with more catalytically active sites and improved conductivity is characterized by electrochemical double layer capacitance (Figure S4) and A.C. impedance (Figure S5). The Co3O4-x offers a capacitance of 6.43 mF·cm-2, which is larger than that of Co3O4 (4.41 mF·cm-2). The result suggests that the Co3O4-x possesses larger active surface area, which provides abundant active sites. In addition, the electrochemical impedance spectra (EIS) demonstrate that Co3O4-x possesses better ion and charge transport capability than that of Co3O4.


Page 11 of 30 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

ACS Nano

Figure 2. (a) CV curves of the pristine Co3O4 and Co3O4-x in a N2- and O2-saturated 0.1 M KOH, (b) LSV curves of the pristine Co3O4 and Co3O4-x at 1600 rpm for ORR performance. (c) RRDE measurements for electron transfer number and HO2- yield. (d) LSV curves of the pristine Co3O4 and Co3O4-x in O2-saturated 0.1 M KOH for OER performance tested with 5 mV·s-1 at 1600 rpm, and (e) Tafel plots calculated from (d). (f) LSV curves of pristine Co3O4 and Co3O4-x for overall polarization. All LSV curves are collected with IR-correction.

The electrochemical performance of Zn-Co3O4-x /-air hybrid battery Considering the good ORR and OER performance, together with the redox reaction between Co3+ and Co2+, the Co3O4-x nanorods could be used as cathode in both Zn-air battery and Zn-ion battery. Therefore, a hybrid battery can be expected. Prior to assembly full battery, polypropylene non-woven fabrics decorated by polyethylene and carbon black was applied to furnish Co3O4-x electrode with a waterproof and breathe surface, which endows a hydrophobic surface to assist gas diffusion in/out and meanwhile as a 10 ACS Paragon Plus Environment

ACS Nano 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

Page 12 of 30

barrier to prevent the leakage of electrolyte. The battery shown in Figure 3a was assembled by Co3O4-x-based electrode as cathode, metallic Zn-plate as anode and mixture solution of 6 M KOH and 0.2 M Zn(AC)2 as electrolyte. Subsequently, the electrochemical performance of the battery was evaluated by CV measurement and gavanstatically charge/discharge cycling test. As shown in Figure 3b, the CV curves in N2-saturated medium exhibits apparent anodic/cathodic peaks at 1.95/2.05V, which is associated with reversibly Faradaic redox reaction of Co-O↔Co-O-OH. Surprisingly, in ambient air, strong reduction current appears at the potential less than 1.33 V, oxidation current at the potential more than 2.1 V, which is attributed to ORR and OER process, respectively. Meanwhile, the same anodic/cathodic peaks are still observed, further confirming that the battery enable to reversibly store and deliver charges via double sets of electrochemical reaction (named as ORR and OER in Zn-air battery, Faradaic redox reaction of Co-O/Co-O-OH in Zn-Co3O4-x battery) simultaneously in one battery with Co3O4-x as cathode. Such combination of complementary electrochemical process results in a powerful hybrid battery of Zn-air and Zn-Co3O4-x. As show in Figure 3c, the initial discharge/charge/discharge voltage profiles exhibit a flat plateau at 1.23 V, similar to typical discharge curves of Zn-air batteries. However, in the following charge process, two voltage plateaus at about 1.93 V and 2.0 V are observed, which is evidently different from an individual Zn-air battery. As shown in Figure S7, the plateau at 1.93 V is assigned to Co-O → Co-O-OH oxidation reaction, whereas, the plateau at 2.0 V is attributed to OER process. Correspondingly, a plateau at 1.90 V originating from Co-O-OH → Co-O cation reduction and a voltage plateau at 1.23 V stemming from ORR behavior, present in discharging process. The results are in


Page 13 of 30 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

ACS Nano

agreement with CV curves. To further confirm the galvanodynamic electrochemical process, charge-discharge process of the hybrid battery was conducted at current density from 0 to 80 mA·cm-2 (Figure 3d). The charge profile exhibits two voltage plateaus. The voltage plateau around 1.95 V is ascribed to the oxidation reaction of Co-O → Co-O-OH, while the voltage plateau at about 2.13 V is assigned to OER process. The discharge profile exhibits two apparent voltage plateau as well. The voltage plateau at around 1.92 V is assigned to the reduction reaction of Co-O-OH → Co-O, and the voltage plateau closed to 1.1 V is ascribed to ORR process. The corresponding current density versus power density reveals an enhanced peak power density of 3200 W·kg-1 at 80 mA·cm-2. The Zn-Co3O4-x batteries show high rate electrochemical process (1.68 slope of power density vs. current density), which derive from higher discharge voltage and rapid electrochemical kinetics of Co3O4-x redox reaction compared to lower rate of ORR process (0.89 slope of power density vs. current density) (Figure 3e). Galvanostatic discharge curves of the hybrid zinc battery at 5 and 10 mA·cm-2 demonstrate semblable voltage profiles with a little operating voltage drops and specific capacities with the increase of discharging current density, which is in agreement with Zn-air batteries. The results are attributed to slow ORR kinetics process at high current densities, leading to large over-potentials (Figure 3f). The discharge profile at 10 mA·cm2

still gives competitive discharge voltage plateau of above 1.21 V and specific capacity

of about 800 mAh·g-1. Considering total mass of active cobalt species and the zinc anode used, the gravimetric energy density of the hybrid battery is 1060 Wh·Kg-1, which highlights high energy density of Zn-air battery. As shown in Figure S8, the contributions of zinc-Co3O4-x battery and zinc-air battery at different voltage segments are verified and


ACS Nano 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

Page 14 of 30

the specific capacity is normalized against the geometrical area of electrode. It is observed that when the required voltage is higher than 1.4 V, the capacity is delivered by zinc-Co3O4-x battery. Whereas, the zinc-air batter delivers capacity at 1.23 V. Thus, we can choose different operating systems of hybrid zinc batteries according to our required voltage. Furthermore, the Nyquist plots of A.C. impedance of the zinc-Co3O4-x and zincair battery are carried out, which could be used to evaluate charge transfer resistances (Figure S9). It shows that the charge transport capability of zinc-air battery is poorer than that of zinc-Co3O4-x battery, which is ascribed to the air molecular on the surface of cathode in zinc-air battery. Stability is another important criterion of the batteries for application prospects. The hybrid battery manifests good electrochemical durability with stably delivered capacity and charge/discharge voltage profiles (Figure 3g). After exceeding more 18 days (440 h) of continuous testing (over 1500 cycles), the voltage of redox reaction and ORR/OER remained substantially unchanged. The characteristic two-sets charge/discharge profile is also remained throughout the cycling measurements, as shown by that of selected cycles (Figure 3h). In addition, the electrochemical performance of the Zn-Co3O4-x batteries component in hybrid batteries were tested in N2-satureated medium. The results show that after Ar-plasma treatment, Co3O4-x has higher capacity and faster kinetics compared to pristine Co3O4 (Figure S6a, b). The hybrid batteries based on Co3O4-x in N2-saturated medium delivers good stability of 93.6 % capacity retention after 1600 cycling test at 2 A·g-1 (Figure S6c). To sum up, the oxygen-vacancy-bearing Co3O4-x is electrochemically well-improved in terms of more positive potential, larger current, lower peroxide yield


Page 15 of 30 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

ACS Nano

for the ORR and OER processes, as well as enhanced kinetics for redox reactions of CoO ↔ Co-O-H.

Figure 3. (a) Schematic illustration of Zn-Co3O4-x/Zn-air hybrid battery, (b) CV curves of the hybrid battery with Zn plate as anode and Co3O4-x as cathode in air and N2 atmosphere. (c) Galvanostatic discharge-charge-discharge profile of the cycling measurement (at 5 mA·cm-2, segment I: 5 min discharge; segment II: charge to 1.95 V; segment III: 5 min charge; segment IV: discharging to 1.25 V; segment V: 5 min discharge), elaborating the transformation of the battery from a Zn-air battery to a ZnCo3O4-x/Zn-air hybrid battery. (d) Galvanodynamic charge/discharge voltage behaviors and (e) corresponding power density profile of Zn-Co3O4-x/Zn-air hybrid battery. (f) Full discharging profiles recorded at 5 and 10 mA cm-2. (g) Galvanostatic charge/discharge 14 ACS Paragon Plus Environment

ACS Nano 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

Page 16 of 30

cycling test recorded at 5 mA·cm-2. (h) Galvanostatic charge/discharge voltage profiles achieved at the 1st, 20th, 100th, 500th, and 1500th cycles from cycling test.

Solid-state waterproof and washable hybrid battery Considering various potential operating conditions such as swimming, rainy day, laundry process and outdoor activities without charging power source, the battery is expected to continuously work in any environments.38 The waterproof, washable and rechargeable solid-state hybrid battery was directly assembled using the Co3O4-x cathode, aqueous polyacrylamide (PAM) hydrogel electrolyte,39 deposited-Zn on CFC and waterproofbreathe membrane. Unlike the conventional Zn-air battery disable in oxygen-free environment, the flexible hybrid battery may be used in anaerobic conditions in the ZnCo3O4-x mode (Figure 4a). The observed charge and discharge voltage plateaus are at 1.93 V and 1.9 V, respectively, which is basically consistent with the reported Zn-Co3O4 battery17. As shown in Figure S10a, the hybrid battery delivers reversible capacities of 148 mAh·g-1 at 1 A·g-1. Moreover, it exhibits high discharge capacities of 178, 152, 145, 138, 132 and 129 mAh g-1 at 0.5, 1, 2, 3, 4 and 5 A·g-1, respectively. After cycling back to 0.5 A·g-1, an average discharge capacity recovers to 176 mAh·g-1, which is equal to 98.8 % of the initial capacity (178 mAh g-1). It obviously highlights the good structural adaptability of the hybrid batteries in delivering capacities at various currents (Figure S10b). In addition, the Zn-Co3O4-x/Zn-air hybrid battery displays good stability under oxygen-free conditions (Figure S10c). After 1200 cycling tests at 2 A·g-1, it still retains 90.1 % capacity.


Page 17 of 30 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

ACS Nano

When the sealed solid-state flexible hybrid batteries are exposed to ambient air condition, both Zn-air battery and Zn-Co3O4-x battery automatically start to work simultaneously (Figure 4b). More impressively, the solid-state hybrid battery also delivers a good longterm cycling stability, manifesting an great stability after even 400 cycles over 200 h of 2 mA·cm-2 (Figure 4c). We also simulated an extreme application case, that is, the battery has to provide power for a very long time through a continuous discharge process before a charger is available. That is, the galvanostatic charge/discharge is followed by a longtime continuous discharge (In detail, five cycles followed by 5 h continuous discharge at current density of 2 mA·cm-2 for the cycles), as shown in Figure 4d. Joyfully, after over even 260 h for 40 cycles, it still presents equivalent electrochemical performance with initial test. The exceptional electrochemical performance is attributed to highperformance multifunctional Co3O4-x electrode with all Faradic redox reaction and ORR/OER performances, as well as the high ionic conductivity of PAM hydrogel electrolyte. The results manifest that the solid-state hybrid batteries is promising as a multifunctional, high-performance and long-span life flexible energy storage device. Our flexile hybrid battery is also waterproof and washable, targeting on the wearable applications. To investigate the waterproof performance, we soaked and washed the fabricated hybrid batteries. The solid-state hybrid battery was immersed in a water filled glass vessel (Figure 4e, 4f). It is observed that the hybrid battery works well with the ZnCo3O4-x battery' output under water and the electronic watch works throughout the experiment (insert of Figure 4e and Supplementary video 1). Furthermore, the battery still maintains 98.6% of its initial open-circuit voltage and 99.2% capacity retention, even after continuous soaking for 20 h in water (Figure S11). In contrast, the voltage of a Zn-


ACS Nano 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

Page 18 of 30

air battery utilizing commercial Pt/C as electrocatalyst quickly drops to below 0.1 V and it cannot power the electronic watch under water (Figure S12 and Supplementary video 2). The results indicate that the hybrid battery of Zn-Co3O4-x /Zn-air battery is fully capable to work under water. To simulate washing environment, a high-power magnetic stirrer (500 rpm) rotated the hybrid battery in water (Figure 4g). The battery retained 93.2 % of its initial capacity after 1 h washing, manifesting great waterproof and mechanical properties.

Figure 4. Voltage profile of the initial discharge-charge-discharge of the cycle in (a) oxygen-free (at 2 mA·cm-2, segment I: charge to 1.95 V; segment II: discharge to 0.8 V) and (b) oxygen-exposure conditions (at 2 mA·cm-2, segment I: 5 min discharge; segment II: charge to 1.95 V; segment III: 5 min charge; segment IV: discharging to 1.25 V; 17 ACS Paragon Plus Environment

Page 19 of 30 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

ACS Nano

segment V: 5 min discharge). The insert is a schematic illustration of solid-state ZnCo3O4-x /Zn-air hybrid battery with Co3O4-x as cathode, deposited-Zn as anode and sodium PAM hydrogel as electrolyte working in (a) oxygen-free and (b) oxygen-exposure environments. (c) Galvanostatic charge/discharge cycling tests at 2 mA·cm-2. (d) Galvanostatic charge/discharge cycling, followed by continuous long-term discharge. (e) Voltage profile of the initial charge/discharge of the cycling with the battery in water. (f) Open-circuit voltage of a hybrid battery during continuous soaking test. (g) Electrochemical performance of a hybrid battery during continuous washing test.

Wearable/flexible solid-state hybrid battery for practical application Subsequently, two solid-state hybrid batteries were connected in series to enlarge the operating voltage window. As shown in Figure 5a, no matter the hybrid batteries work as Zn-Co3O4-x battery and Zn-air battery, separately, or work as a hybrid battery, the two-inseries has twice wider voltage window (2.5-4 V) with a quite same discharge time with a single battery. We then dedicate to evaluate the flexibility of hybrid battery working under both aerobic or anaerobic conditions with an emphasis on the two sets of electrochemical reactions in one system. As shown in Figure 5b, a set of light-emitting diodes (LED) can operate when the batteries are sealed up, powered by the Zn-Co3O4-x mode of the flexible hybrid battery. After thirty minutes, the battery is exhausted (Figure 5c). Interestingly, when we open the gas diffusion window, the battery quickly recovered to working status and the LEDs are lightened again in the Zn-air battery mode of the hybrid battery working (Figure 5d and Supplementary video 3). In addition, to demonstrate the practical application of flexible/wearable energy storage device in portable electronics, a wristband 18 ACS Paragon Plus Environment

ACS Nano 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

Page 20 of 30

of electronic watch was designed using the developed flexible hybrid battery (Figure 5ef). The flexible solid-state hybrid battery enables to work as a power source of the watch under either flat or bent condition. These results reveal good flexibility of the Zn-Co3O4x/-air

hybrid battery, which is able to power electronics under various deformations.

Figure 5. (a) Galvanostatic charge/discharge curves of two Zn-Co3O4-x/Zn-air hybrid batteries connected in series. (Segment I. The hybrid batteries work as Zn-Co3O4-x battery in an oxygen-free environment; Segment II. The hybrid batteries work as Zn-air battery for continuous discharge in ambient air; Segment III. The hybrid batteries work as hybrid battery in oxygen-exposure environment). (b) Two batteries are connected in series to


Page 21 of 30 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

ACS Nano

power a set of LEDs. (c) After the hybrid batteries are exhausted, (d) the hybrid batteries automatically recover to work when it was exposed back to ambient air. (e-g) The flexible hybrid batteries power a watch under different deformations.

CONCLUSION By creating abundant oxygen vacancies, we successfully endow cobalt oxide (Co3O4-x) with the ability to carry out multiple electrochemical reactions, including ORR/OER electrocatalysis and Faradic Co-O↔Co-O-OH redox reactions. Taking advantage of this property, a hybrid battery of Zn-Co3O4-x and Zn-air batteries was well constructed. The hybrid battery reveals both remarkably high-power density of 3200 W·kg-1 and energy density of 1060 Wh·kg-1. Impressively, the hybrid battery exhibits high stability of charge/discharge voltage profiles under varied testing conditions (1500 cycles over 18 days at 5 mA·cm-2 for hybrid battery; 1600 cycles at 2 A·g-1 for Zn-Co3O4-x component). Subsequently, a flexible hybrid battery based on solid-state hydrogel electrolyte was fabricated. The device is capable to work both under water and/or in air, demonstrating the great environmental adaption. More interestingly, even when the battery’s electricity runs out in an oxygen-free environment, the hybrid battery can automatically restore itself to output electricity as long as it is exposed to air. We believe the developed device is very attractive for various wearable applications, considering its great electrochemical performances, water-proof ability, washability as well as the air-triggered recoverability. In addition, the developed hybrid energy-storage technologies may be further extended to other materials and fields, enhancing performances and extending usage scenarios of batteries.


ACS Nano 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

Page 22 of 30

METHODS Preparation of freestanding Co3O4-x nanorods The freestanding Co3O4 nanorods on CFC are fabricated according our previous work7 and the details are shown in supporting information. The obtained freestanding Co3O4 nanorods on CFC is directly treated to obtain Co3O4-x by 30 min Ar-plasma (commercial 13.56 MHz RF source)

irradiation with power of 37.8 W and pressure of 500 Pa.

Assembling of zinc-Co3O4-x/zinc-air hybrid battery To achieve a hydrophobic surface that promotes air diffusion and prevents aqueous electrolyte from leakage, the aqueous polytetrafluoroethylene (PTFE) solution (1%) was sprayed on the surface of Co3O4-x nanorods on CFC, meanwhile a waterproof and breathable film was attached on the surface of electrode. The coated electrode was dried at room temperature for 12 hours. Then, considering that the electrode surface contacting with electrolyte requires a hydrophilic surface, the electrode was cleaned using Arplasma for 10 min. The resultant electrodes possess one highly hydrophobic surface and meanwhile a highly hydrophilic surface with well-retained ORR activity. For fabrication of a full battery, the treated freestanding Co3O4-x nanorods on CFC was directly used as cathode, deposited-Zn on CFC was used as anode, aqueous 6 M KOH with 0.2 M Zn(CH3COO)2 additives aqueous solution (aqueous battery) or PAM hydrogel film (solid-state battery) was used as electrolyte to form a sandwich structure. Electrochemical performance of full battery The electrochemical performance is tested using freestanding Co3O4-x nanorods on CFC electrode as cathode, freestanding deposited-Zn nanosheets on CFC as anode and


Page 23 of 30 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

ACS Nano

aqueous solution of 6 M KOH with 0.2 M Zn(CH3COO)2 additives (aqueous battery) or PAM hydrogel (quasi solid-state battery) as electrolyte. Cyclic voltammetry curves (CV) are carried out by using an electrochemical workstation (CHI 760D, Chenhua) at electrochemical voltage window of 0.8-2.1 V. Galvanostatic charge-discharge measurements is conducted with segment I: 5 min discharge; segment II: charge to 1.95 V; segment III: 5 min charge; segment IV: discharging to 1.25 V; segment V: 5 min discharge, by utilizing a land 2001A battery testing system with two-electrode configuration at room temperature. The power density (P) of the battery is calculated by P = I · V, where I is the discharge current density and V is the corresponding voltage. The gravimetric energy density (E) of the hybrid battery is calculated by using the following equation:

= ( /

where t is the time, I is the discharge current, V(t) is the discharge voltage at t, dt is time differential, m is the total mass of the device.

ASSOCIATED CONTENT Supporting Information Available: The supporting information is available free of charge via the Internet at ACS Publications website or from the authors. It includes experimental details of the preparation of Co3O4, Zn electrode, hydrogel electrolyte and electrocatalytic test, and supplementary Figures S1-S12.


ACS Nano 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

Page 24 of 30

The authors declare no competing financial interest.

ACKNOWLEDGEMENT The work is sponsored by the project 2017JY0088 supported by Science & Technology Department of Sichuan Province and the Chengdu Research Institute, City University of Hong Kong (9610372). The work was also partially sponsored by the Science Technology and Innovation Committee of Shenzhen Municipality (the Grant No. JCYJ20170818103435068).


Page 25 of 30 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

ACS Nano

REFERENCES 1. Wang, J.; Huang, Z.; Liu, W.; Chang, C.; Tang, H.; Li, Z.; Chen, W.; Jia, C.; Yao, T.; Wei, S.; Wu, Y.; Li, Y., Design of N-Coordinated Dual-Metal Sites: A Stable and Active Pt-Free Catalyst for Acidic Oxygen Reduction Reaction. J. Am. Chem. Soc. 2017, 139, 17281-17284. 2. Li, Y.; Dai, H., Recent Advances in Zinc-Air Batteries. Chem. Soc. Rev. 2014, 43, 5257-5275. 3. Li, Y.; Gong, M.; Liang, Y.; Feng, J.; Kim, J.; Wang, H.; Hong, G.; Zhang, B.; Dai, H.,

Advanced

Zinc-Air

Batteries

Based

on

High-Performance

Hybrid

Electrocatalysts. Nat. Commun. 2013, 4, 1805-18012. 4. Chen, X.; Liu, B.; Zhong, C.; Liu, Z.; Liu, J.; Ma, L.; Deng, Y.; Han, X.; Wu, T.; Hu, W.; Lu, J., Flexible Batteries: Ultrathin Co3O4 Layers with Large Contact Area on Carbon Fibers as High-Performance Electrode for Flexible Zinc-Air Battery Integrated with Flexible Display. Adv. Energy Mater. 2017, 7, 1700779-1700790. 5. Li, B.; Quan, J.; Loh, A.; Chai, J.; Chen, Y.; Tan, C.; Ge, X.; Hor, T. S. A.; Liu, Z.; Zhang, H.; Zong, Y., A Robust Hybrid Zn-Battery with Ultralong Cycle Life. Nano Lett. 2017, 17, 156-163. 6. Lee, D. U.; Fu, J.; Park, M. G.; Liu, H.; Ghorbani, A.; Chen, Z., Self-Assembled NiO/Ni(OH)2 Nanoflakes as Active Material for High-Power and High-Energy Hybrid Rechargeable Battery. Nano Lett. 2016, 16, 1794-1802. 7. Ma, L.; Chen, S.; Li, H.; Ruan, Z.; Tang, Z.; Liu, Z.; Wang, Z.; Huang, Y.; Pei, Z.; Zapien, J.; Zhi, C., Initiating a Mild Aqueous Electrolyte Co3O4/Zn Battery with 2.2


ACS Nano 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

Page 26 of 30

V-High Voltage and 5000-Cycle Lifespan by a Co(III) Rich-Electrode. Energy Environ. Sci. 2018, DOI:10.1039/C8EE01415A. 8. Zhang, J.; Zhao, Z.; Xia, Z.; Dai, L., A Metal-Free Bifunctional Electrocatalyst for Oxygen Reduction and Oxygen Evolution Reactions. Nat. Nanotechnol. 2015, 10, 444-452. 9. Meng, F.; Zhong, H.; Bao, D.; Yan, J.; Zhang, X., In Situ Coupling of Strung Co4N and Intertwined N-C Fibers toward Free-Standing Bifunctional Cathode for Robust, Efficient, and Flexible Zn-Air Batteries. J. Am.Chem. Soc. 2016, 138, 10226-10231. 10. Pei, Z.; Li, H.; Huang, Y.; Xue, Q.; Huang, Y.; Zhu, M.; Wang, Z.; Zhi, C., Texturing Insitu: N,S-Enriched Hierarchically Porous Carbon as a Highly Active Reversible Oxygen Electrocatalyst. Energy Environ. Sci. 2017, 10, 742-749. 11. Pei, Z.; Gu, J.; Wang, Y.; Tang, Z.; Liu, Z.; Huang, Y.; Huang, Y.; Zhao, J.; Chen, Z.; Zhi, C., Component Matters: Paving the Roadmap toward Enhanced Electrocatalytic Performance of Graphitic C3N4-Based Catalysts via Atomic Tuning. ACS Nano 2017, 11, 6004-6014. 12. Chen, S.; Cheng, J.; Ma, L.; Zhou, S.; Xu, X.; Zhi, C.; Zhang, W.; Zhi, L.; Zapien, J., Light-Weight 3D Co-N-Doped Hollow Carbon Spheres as Efficient Electrocatalysts for Rechargeable Zinc-Air batteries. Nanoscale 2018, 10, 10412-10419. 13. Ma, L.; Chen, S.; Pei, Z.; Huang, Y.; Liang, G.; Mo, F.; Yang, Q.; Su, J.; Gao, Y.; Zapien, J.; Zhi, C., Single-Site Active Iron-Based Bifunctional Oxygen Catalyst for a Compressible and Rechargeable Zinc–Air Battery. ACS Nano 2018, 12, 1949-1958. 14. Li, H.; Han, C.; Huang, Y.; Huang, Y.; Zhu, M.; Pei, Z.; Xue, Q.; Wang, Z.; Liu, Z.; Tang, Z.; Wang, Y.; Kang, F.; Li, B.; Zhi, C., An Extremely Safe and Wearable


Page 27 of 30 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

ACS Nano

Solid-State Zinc Ion Battery Based on a Hierarchical Structured Polymer Electrolyte. Energy Environ. Sci. 2018, 11, 941-951. 15. Liu, Z.; Li, H.; Zhu, M.; Huang, Y.; Tang, Z.; Pei, Z.; Wang, Z.; Shi, Z.; Liu, J.; Huang, Y.; Zhi, C., Towards Wearable Electronic Devices: a Quasi-Solid-State Aqueous Lithium-Ion Battery with Outstanding Stability, Flexibility, Safety and Breathability. Nano Energy 2018, 44, 164-173. 16. Zhu, M.; Huang, Y.; Huang, Y.; Li, H.; Wang, Z.; Pei, Z.; Xue, Q.; Geng, H.; Zhi, C., A Highly Durable, Transferable, and Substrate‐Versatile High‐Performance All‐ Polymer Micro‐Supercapacitor with Plug‐and‐Play Function. Adv. Mater. 2017, 29, 1605137-1605144. 17. Wang, X.; Wang, F.; Wang, L.; Li, M.; Wang, Y.; Chen, B.; Zhu, Y.; Fu, L.; Zha, L.; Zhang, L.; Wu, Y.; Huang, W., An Aqueous Rechargeable Zn//Co3O4 Battery with High Energy Density and Good Cycling Behavior. Adv. Mater. 2016, 28, 4904-4911. 18. Huang, Y.; Ip, W. S.; Lau, Y. Y.; Sun, J.; Zeng, J.; Yeung, N. S. S.; Ng, W. S.; Li, H.; Pei, Z.; Xue, Q.; Wang, Y.; Yu, J.; Hu, H.; Zhi, C., Weavable, Conductive YarnBased NiCo//Zn Textile Battery with High Energy Density and Rate Capability. ACS Nano 2017, 11, 8953-8961. 19. Zhang, F.; Zhang, T.; Yang, X.; Zhang, L.; Leng, K.; Huang, Y.; Chen, Y., A HighPerformance Supercapacitor-Battery Hybrid Energy Storage Device Based on Graphene-Enhanced Electrode Materials with Ultrahigh Energy Density. Energy Environ. Sci. 2013, 6, 1623-1632. 20. Dubal, D.; Ayyad, O.; Ruiz, V.; Gomez, P., Hybrid Energy Storage: the Merging of Battery and Supercapacitor Chemistries. Chem. Soc. Rev. 2015, 44, 1777-1790.


ACS Nano 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

Page 28 of 30

21. Ma, T.; Yang, H.; Lu, L., Development of Hybrid Battery–Supercapacitor Energy Storage for Remote Area Renewable Energy Systems. Appl. Energy 2015, 153, 56-62. 22. Li, R.; Wang, Y.; Zhou, C.; Wang, C.; Ba, X.; Li, Y.; Huang, X.; Liu, J., Carbon‐ Stabilized High‐Capacity Ferroferric Oxide Nanorod Array for Flexible Solid‐State Alkaline Battery-Supercapacitor Hybrid Device with High Environmental Suitability. Adv. Funct. Mater. 2015, 25, 5384-5394. 23. Yu, L.; Guan, B.; Xiao, W.; Lou, X. W., Formation of Yolk‐Shelled Ni-Co Mixed Oxide Nanoprisms with Enhanced Electrochemical Performance for Hybrid Supercapacitors and Lithium Ion Batteries. Adv. Energy Mater. 2015, 5, 15009811500988. 24. Zuo, W.; Li, R.; Zhou, C.; Li, Y.; Xia, J.; Liu, J., Battery‐Supercapacitor Hybrid Devices: Recent Progress and Future Prospects. Adv. Sci. 2017, 4, 1600539-1600560. 25. Zhu, M.; Huang, Y.; Deng, Q.; Zhou, J.; Pei, Z.; Xue, Q.; Huang, Y.; Wang, Z.; Li, H.; Huang, Q.; Zhi, C., Highly Flexible, Freestanding Supercapacitor Electrode with Enhanced Performance Obtained by Hybridizing Polypyrrole Chains with MXene. Adv. Energy Mater. 2016, 6, 1600969-1600978. 26. Dieterle, M.; Weinberg, G.; Mestl, G., Raman Spectroscopy of Molybdenum Oxides Part I. Structural Characterization of Oxygen Defects in MoO3-x by DR UV/VIS, Raman Spectroscopy and X-ray Diffraction. Phys. Chem. Chem. Phys. 2002, 4 (5), 812-821. 27. Wang, G.; Ling, Y.; Li, Y., Oxygen-Deficient Metal Oxide Nanostructures for Photoelectrochemical Water Oxidation and Other Applications. Nanoscale 2012, 4, 6682-6691.


Page 29 of 30 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

ACS Nano

28. Casas-Cabanas, M.; Binotto, G.; Larcher, D.; Lecup, A.; Giordani, V.; Tarascon, J., Defect Chemistry and Catalytic Activity of Nanosized Co3O4. Chem. Mater. 2009, 21, 1939-1947. 29. Wang, H.; Fan, R.; Miao, J.; Chen, J.; Mao, S.; Deng, J.; Wang, Y., Oxygen Vacancies on the Surface of HxWO3−y for Enhanced Charge Storage. J. Mater. Chem. A 2018, 6, 6780-6784. 30. Jia, Y.; Zhang, L.; Gao, G.; Chen, H.; Wang, B.; Zhou, J.; Soo, M. T.; Hong, M.; Yan, X.; Qian, G.; Zou, J.; Du, A.; Yao, X., A Heterostructure Coupling of Exfoliated NiFe Hydroxide Nanosheet and Defective Graphene as a Bifunctional Electrocatalyst for Overall Water Splitting. Adv. Mater. 2017, 29, 1700017-1700025. 31. Kim, H.-S.; Cook, J. B.; Lin, H.; Ko, Jesse S.; Tolbert, H.; Ozolins, V.; Dunn, B., Oxygen Vacancies Enhance Pseudocapacitive Charge Storage Properties of MoO3-x. Nat. Mater. 2016, 16, 454-460. 32. Xu, L.; Jiang, Q.; Xiao, Z.; Li, X.; Huo, J.; Wang, S.; Dai, L., Plasma-Engraved Co3O4 Nanosheets with Oxygen Vacancies and High Surface Area for the Oxygen Evolution Reaction. Angew. Chem. Int. Ed. 2016, 128, 5363-5367. 33. Bao, J.; Zhang, X.; Fan, B.; Zhang, J.; Zhou, M.; Yang, W.; Hu, X.; Wang, H.; Pan, B.; Xie, Y., Ultrathin Spinel-Structured Nanosheets Rich in Oxygen Deficiencies for Enhanced Electrocatalytic Water Oxidation. Angew. Chem. Int. Ed. 2015, 127, 75077512. 34. Zhu, J.; Kailasam, K.; Fischer, A.; Thomas, A., Supported Cobalt Oxide Nanoparticles As Catalyst for Aerobic Oxidation of Alcohols in Liquid Phase. ACS Catal. 2011, 1, 342-347.


ACS Nano 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

Page 30 of 30

35. Ma, L.; Fan, H.; Fu, K.; Lei, S.; Hu, Q.; Huang, H.; He, G., Protonation of Graphitic Carbon Nitride (g-C3N4) for an Electrostatically Self-Assembling Carbon@g-C3N4 Core-Shell Nanostructure toward High Hydrogen Evolution. ACS Sustain. Chem. Eng. 2017, 5, 7093-7103. 36. Ma, L.; Fan, H.; Tian, H.; Fang, J.; Qian, X., The n-ZnO/n-In2O3 Heterojunction Formed by a Surface-Modification and their Potential Barrier-Control in Methanal Gas Sensing. Sensors Actuat. B: Chem. 2016, 222, 508-516. 37. Wang, Y.; Zhou, T.; Jiang, K.; Da, P.; Peng, Z.; Tang, J.; Kong, B.; Cai, W.; Yang, Z.; Zheng, G., Reduced Mesoporous Co3O4 Nanowires as Efficient Water Oxidation Electrocatalysts and Supercapacitor Electrodes. Adv. Energy Mater. 2014, 4, 1400696-1400705. 38. Wang, H.; Deng, J.; Xu, C.; Chen, Y.; Xu, F.; Wang, J.; Wang, Y., Ultramicroporous Carbon Cloth for Flexible Energy Storage with High Areal Capacitance. Energy Storage Mater. 2017, 7, 216-221. 39. Huang, Y.; Zhong, M.; Shi, F.; Liu, X.; Tang, Z.; Wang, Y.; Huang, Y.; Hou, H.; Xie, X.; Zhi, C., An Intrinsically Stretchable and Compressible Supercapacitor Containing a Polyacrylamide Hydrogel Electrolyte. Angew. Chem. Int. Ed. 2017, 56, 9141-9145.


Flexible Waterproof Rechargeable Hybrid Zinc Batteries Initiated by

Recommend Documents