as High-Performance Anode in Sodium I - ACS Publications

Jan 16, 2018 - favorable nanocrystal facets.38 Wu et al. fabricated a porous binary-phase ..... (11) Ni, Q.; Bai, Y.; Wu, F.; Wu, C. Polyanion-Type El...
0 downloads 0 Views 6MB Size
Subscriber access provided by READING UNIV

Article

Remarkable effect of sodium alginate aqueous binder on anatase TiO2 as high-performance anode in sodium ion batteries Liming Ling, Ying Bai, Zhaohua Wang, Qiao Ni, Guanghai Chen, Zhiming Zhou, and Chuan Wu ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.7b17659 • Publication Date (Web): 16 Jan 2018 Downloaded from http://pubs.acs.org on January 17, 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 free 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 accessible to all readers and 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.

ACS Applied Materials & Interfaces 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 29 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 Applied Materials & Interfaces

Remarkable Effect of Sodium Alginate Aqueous Binder on Anatase TiO2 as High-Performance Anode in Sodium Ion Batteries Liming Ling,†,‡ Ying Bai,*,†,§Zhaohua Wang,† Qiao Ni,† Guanghai Chen,† Zhiming Zhou,‡ and Chuan Wu*,†,§ †

Beijing Key Laboratory of Environmental Science and Engineering, School of

Materials Science and Engineering, Beijing Institute of Technology, Beijing 100081, China ‡

School of Chemistry and Chemical Engineering, Beijing Institute of Technology, Beijing 100081, P. R. China

§

Collaborative Innovation Center of Electric Vehicles in Beijing, Beijing 100081, China

ABSTRACT: Sodium alginate (SA) is investigated as the aqueous binder to fabricate high performance, low cost and environmental-friendly durable TiO2 anode in sodium-ion batteries (SIBs) for the first time. Compared to the conventional polyvinylidene difluoride (PVDF) binder, electrodes using SA as the binder exhibit significant promotion of electrochemical performances. The initial coulombic efficiency is as high as 62% at 0.1 C. A remarkable capacity of 180 mAh g-1 is achieved with no decay after 500 cycles at 1 C. Even at 10 C (3.4 A g-1), it remains 82 mAh g-1 after 3600 cycles with approximate 100% coulombic efficiency. TiO2 electrodes with SA binder display less electrolyte decomposition and side reaction, high electrochemistry reaction activity, effective suppression of polarization, and good electrode morphology, which is ascribed to the rich carboxylic groups, high Young’s modulus, and good electrochemical stability of SA binder. KEYWORDS: sodium alginate, binder, anatase TiO2, durable, sodium ion batteries ACS Paragon Plus Environment

ACS Applied Materials & Interfaces 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

1. INTRODUCTION Nowadays, lithium-ion batteries (LIBs) are quite attractive as power sources applied to smart grids, transportation systems and other electric energy storage devices.1,2 Compared to their high energy and power densities, the major concerns of LIBs are deficiency and unevenly distribution of lithium source.3 Taking into account the growing demand and market, these disadvantages will greatly restrict the application for future large-scale energy storage. While, sodium ion batteries (SIBs) have received growing interest owing to the abundant and available advantages of sodium as an alternative to LIBs for large-scale energy storage.4 However, the larger ion radius (1.02 Å) of sodium than that of lithium (0.76 Å) affects the phase stability, reaction kinetics, and interphase formation. Therefore, the search for a suitable SIBs electrode material with low cost and high performance remains an obstacle.5 Recently, various materials have attracted great interest as SIBs cathode,6–16 such as layer transition metal oxides and polyanion-type compounds. Meanwhile, a variety of potential anode materials for SIBs has also been reported; for instance, carbonaceous, metal oxide, metal sulfide, metal alloy, and organic composite materials.17–25 Titanium-based oxides attract particularly extensive attention as SIBs and LIBs anode because of the reasonable cost, stability, nontoxicity, and suitable operation voltage.26–31 As for SIBs anode, titanium dioxides (TiO2) with several polymorphs have been investigated successively.4 Among them, with respect to anatase TiO2, the calculated activation energy for Na+ insertion into the host structure is 0.52 eV, which is comparable to that of Li+ (0.60 eV).32,33 Thus, most works were reported using

ACS Paragon Plus Environment

Page 2 of 29

Page 3 of 29 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 Applied Materials & Interfaces

anatase TiO2, focusing on the studies of sodium storage mechanism and the improvements of electrochemical performance.34–36 Recently, Zhang et al. reported the nitrogen doped/carbon tuning yolk-like TiO2, resulting in fast electron transfer.37 Longoni et al. demonstrated the role of different exposed crystal facets on the sodium storage properties, thus overcoming the intrinsic limits of anatase transport properties by exposing the most favorable nanocrystal facets.38 Wu et al. fabricated a porous binary-phase anatase-TiO2-rutile-TiO2 composite with high grain-boundary density, offering more interfaces for a novel interfacial storage.39 Overall, these studies are almost based on the synthesis and modification of active material with the single or multi-strategy, only improving the intrinsically low electrical conductivity of TiO2 by the elements doping, surface coating, composites constructing, nanomaterials/hierarchical structure design, and facet/phase optimizing. However, these methods are complicated in synthetic routes, sensitive to experiment conditions, the high cost, low reproducibility and undesirable scalability. Moreover, the batteries with TiO2 obtained by the methods above suffer from a low initial coulombic efficiency of less than 50%, resulting in the large loss of irreversible capacity. In fact, the battery performances can be promoted using excellent binder with appropriate swelling property, good electrochemical stability, high affinity, and homogeneous distribution of particles inside the electrode40–43. The binder is the key inactive component, which can greatly affect the contact between the active materials and the current collector, as well as the inter-particles contact. Unfortunately, the effect of the binders on the sodium storage performance of TiO2 has never been

ACS Paragon Plus Environment

ACS Applied Materials & Interfaces 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

reported to the best of my knowledge. Here, for the first time, we adopted sodium alginate (SA) as the binder to study their effect on the sodium storage performance of TiO2. SA is chosen due to its rich carboxylic groups, high Young’s modulus, good electrochemical stability, low cost, and nontoxicity.44 Compared to the conventional PVDF binder, electrodes using SA as the binder exhibit significant promotion of the initial coulombic efficiency, rate capability and cycling stability. The initial coulombic efficiency is as high as 62% at 0.1 C. A remarkable capacity of 180 mAh g-1 is achieved with no decay after 500 cycles at 1 C. Even at 10 C (3.4 A g-1), it remains 82 mAh g-1 after 3600 cycles with approximate 100% coulombic efficiency.

2. EXPERIMENTAL SECTION 2.1. Materials. The anatase TiO2 microparticles were synthesized via a solvothermal method. Typically, tetrabutyl titanate (TBOT, 0.25 ml) was added dropwise into acetic acid (HAc, 50 ml) under stirring. Then the white suspension was transferred to a 100-ml sealed Teflon reactor and heated to 210 °C for 24 hours. After collected by centrifugation, washed with deionized (DI) water and ethanol for several times, the obtained powder was dried at 60 °C for 24 hours, and finally calcined at 400 °C for 30 min in air. The polyvinylidene fluoride (PVDF, -(-CH2-CF2-)n-) and sodium alginate (SA, (C6H7O6Na)n) were acquired from ARKEMA, FRA and ALADDIN, CHN, respectively. The two kinds of polymer binders were used in the form of solution. PVDF solution was obtained by directly dissolving PVDF powder (5 wt. %) in NMP.

ACS Paragon Plus Environment

Page 4 of 29

Page 5 of 29 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 Applied Materials & Interfaces

SA solution was attained by dissolving SA powder (3 wt. %) in DI water. Super-P was used as the carbon additive. The electrolyte was 1 M solution of NaClO4 dissolved in ethylene carbonate (EC) and propylene carbonate (PC) (1:1 v/v). 2.2 Cells. To prepare the working electrode, TiO2 microparticles, Super-P, and the binder (PVDF or SA) were mixed in a 7:2:1 wt. ratio. Then the obtained uniform slurry was coated on Cu foil, dried under vacuum at 120 °C for 24 hours, and pressed at the pressure of 2 MPa. Two-electrode coin cells (CR2025) employing sodium metal as counter electrodes and glass fiber as separators were assembled in an Ar-filled glovebox. 2.3 Characterization. Crystallographic information was analyzed in the 2θ range from 10° to 90° by Rigaku2400 powder X-ray diffraction (XRD) with Cu Kα radiation source. The morphologies were characterized by a S-4800 field-emission scanning electron microscope (FE-SEM) and a Tecnai G2 F20 high-resolution transmission electron microscope (HR-TEM). Fourier transform infrared (FTIR) spectroscopy measurements were performed using a Nicolet iS50 (Thermo Fisher Scientific Inc, USA). Galvanostatic measurements were carried out on a LAND-CT2001A instrument, with 1 C = 335 mA g-1. The cyclic voltammetry (CV) experiments were conducted with a CHI660e electrochemical workstation. CV curves were recorded at a constant scan rate of 0.1 mV s-1 between 0.02-2.5 V vs Na/Na+. Alternating current (AC) impedance measurements were performed over the frequency ranging from 0.1 Hz to 100 kHz using a small perturbation of ± 5 mV.

ACS Paragon Plus Environment

ACS Applied Materials & Interfaces 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

2.4 Calculation. We carried out first-principles calculations in the framework of density functional theory (DFT) as implemented in the Cambridge Sequential Total Energy Package (CASTEP). The generalized gradient approximation (GGA) as formulated by Perdew−Burke−Ernzerhof (PBE) has been used for exchange and correlation contributions. A plane-wave basis set with an energy cutoff of 500 eV was used in the calculations with sufficient Monkhorst–Pack sampled k points 3×3×1. The convergence criterion of the self-consistent field calculations was set to 5×10-6 eV/atom for the total energy. All structures were fully relaxed until the final force on each atom becomes less than 0.01 eV/Å. To prevent spurious interaction between isolated monolayers, a vacuum spacing of at least 15 Å was introduced and pressure on the supercell was decreased to values less than 0.02 Gpa.

3. RESULTS AND DISCUSSION The chemical structure of SA is shown in Scheme 1, along with that of PVDF for comparison. These structures were studied by Fourier transform infrared spectroscopy (FTIR) (Figure 1a). For SA binder, the main absorbance bands at ~1598, 1410, 1300 and 1028 cm-1 are related to O-C-O (carboxylate) asymmetric vibrations, O-C-O symmetric vibrations, C-C-H (and O-C-H) deformation of pyranose rings and C-O-C asymmetric vibrations.45 In contrast to SA, the FTIR spectrum of PVDF shows the characteristic peaks at 1180 and 870 cm-1, which are ascribed to the stretching frequencies of CF2. Figure 1b shows the XRD patterns of these binders. PVDF binder displays the obvious diffraction peak at 20°, while SA presents no strong peaks, which reveals the better crystallinity of PVDF resulting from its semi crystalline polymer

ACS Paragon Plus Environment

Page 6 of 29

Page 7 of 29 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 Applied Materials & Interfaces

with a polymorphism.46 XRD pattern also confirms the anatase phase of the as-prepared TiO2 sample, showing no impurities (Figure 1b). The TiO2 sample is composed of microparticles without uniform shape and ordered structure (Figure 2a). High-resolution transmission electron microscopy (HR-TEM) displays the lattice fringes with an interplanar spacing of d = 0.35 nm, which correspond to the (101) planes (Figure 2b).

Scheme 1. Schematic Diagram of the interactions of the binder (PVDF or SA) with the Cu foil, TiO2 active materials, and the electrolyte.

ACS Paragon Plus Environment

ACS Applied Materials & Interfaces 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

Figure 1 (a) FTIR spectra of PVDF and SA. (b) XRD patterns of PVDF, SA and TiO2. The black vertical line is the standard spectrum of anatase TiO2 (JCPDS, card no: 04-0477). The FTIR characteristic peaks of PVDF and SA are marked with red and blue asterisks, respectively.

ACS Paragon Plus Environment

Page 8 of 29

Page 9 of 29 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 Applied Materials & Interfaces

Figure 2 SEM (a) and HR-TEM (b) images of TiO2 sample. SEM images of TiO2 electrodes using different binders: (c) PVDF, (d) SA.

The PVDF or SA solution was attained by dissolving PVDF powder (Figure 3a) in NMP or SA powder (Figure 3b) in DI water, respectively. Both solutions in uniform distributions are translucent (Figures 3c-d). The TiO2 electrodes were prepared by using these binders, carbon additive and TiO2 particles. As shown in Figure 3e, the prepared electrode slices show the same appearances. Scanning electron microscopy (SEM) studies further reveal that the distribution of materials is homogenous and there are no visible cracks (Figures 2c-d). Moreover, as the energy dispersive X-ray (EDX) mapping shows in Figure S1, the existence of PVDF or SA is confirmed by their special element of F or Na, respectively. It also further demonstrates the homogenous distribution of PVDF or SA.

ACS Paragon Plus Environment

ACS Applied Materials & Interfaces 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

Figure 3 Digital images of PVDF (a) and SA (b) powders; PVDF (c) and SA (d) solutions; electrode slices using PVDF or SA binder (e).

Figures 4a and 4b show the discharge/charge curves of the cell using PVDF or SA binder at 0.1 C. Although the initial discharge capacities of TiO2/PVDF and TiO2/SA electrode are almost the same with ~390 mAh g-1, TiO2/PVDF and TiO2/SA electrodes display the initial charge capacities of 161 and 241 mAh g-1, respectively. Thus, the initial coulombic efficiency of TiO2/SA electrode is 62%, which is much

ACS Paragon Plus Environment

Page 10 of 29

Page 11 of 29 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 Applied Materials & Interfaces

higher than that of TiO2/PVDF electrode (41.5%) and the previous studies (Table 1). For subsequent cycles, TiO2/PVDF electrode delivers obvious capacity decay and voltage changes, which are significantly different from TiO2/SA electrode. As shown in Figure 4c, the capacity retention of TiO2/PVDF electrode after 100 cycles at 0.1 C is only 43.5%, which is much lower than that of TiO2/SA electrode and shows poor cycling stability. To further reveal the voltage changes, the average discharge/charge voltage was calculated. Figure 4d displays the calculated differences in the average charge and discharge voltage at 0.1 C during cycling. Generally, the calculated voltage difference of TiO2/PVDF electrode increases and the voltage difference of TiO2/SA electrode decreases. The 100th average voltage is 0.37 and 1.28 V for the discharge and charge process of cell using PVDF binder, respectively. Nevertheless, the average voltage becomes 0.78 and 0.91 V for the discharge and charge process with TiO2/SA electrode, respectively. In contrast to PVDF binder, the SA binder plays a key effect in enhancing the initial coulombic efficiency, cycling stability and suppressing the polarization of anatase TiO2.

ACS Paragon Plus Environment

ACS Applied Materials & Interfaces 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 29

Figure 4 The galvanostatic curves at 0.1 C for TiO2/PVDF (a) and TiO2/SA (b) anode. (c) The cycling stability at 0.1 C. (d) The differences in the average charge and discharge voltage at 0.1 C. Table 1 The initial coulombic efficiency of previous studies on anatase TiO2 as SIB anode Reference Ref47 Ref50 Ref53 Ref56

Initial efficiency 36.3% ~ 40% ~ 30% ~ 50%

Reference

Initial efficiency

Reference

Initial efficiency

Ref48 Ref51 Ref54 Ref57

< 30% 38% 46.1% ~ 40%

Ref49 Ref52 Ref55 Ref58

46% 31.4% 38.2% ~ 35%

The dQ/dV plots often contain sharp features and are more informative. Therefore, the dQ/dV plots at 0.1 C are provided in Figure 5. In the 1st discharge process, TiO2/PVDF electrode displays the two clear reduction peaks at 0.97 and 0.62 V, which disappear in the subsequent cycles (Figures 5a-b). It is mainly ascribed to the electrolyte decomposition thus the formation of solid electrolyte interface (SEI) and some side reactions.53,59,60 The strong peak at 0.05 V in Figure 5a was

ACS Paragon Plus Environment

Page 13 of 29 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 Applied Materials & Interfaces

demonstrated to be the irreversible phase transition of anatase TiO2 during initial discharge.50 In contrast, TiO2/SA electrode mainly shows the stronger peak at 0.23 V in 1st discharge cycle related to the irreversible phase transition (Figure 5c), which is consistent with the obvious voltage plateau around 0.2 V (Figure 4b) and will vanish in the subsequent cycles. The formation of SEI films is less according to the weak peak at 0.59 V (Figure 5d). The electrolyte decomposition and side reactions can be inhibited by using SA as binder. Thus TiO2/SA electrode displays higher initial charge capacity and coulombic efficiency (Figures 4a-b). For subsequent dQ/dV plots of TiO2/PVDF electrode (Figure 5b), obvious voltage change at the cathodic/anodic peaks is observed, which is similar with the trends of average voltage change as revealed in Figure 4d. Additionally, during the cycling, the absolute value of peak intensity gradually decreases when using PVDF as the binder; the absolute value of peak intensity almost remains unchanged for TiO2/SA electrode. It is consistent with the cycling stability differences of cells using PVDF and SA as the binder.

ACS Paragon Plus Environment

ACS Applied Materials & Interfaces 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

Figure 5 The dQ/dV plots obtained from the galvanostatic curves at 0.1 C for TiO2/PVDF (a-b) or TiO2/SA (c-d) anode. Figures (a) and (c) are the overall curves. Figures (b) and (d) are the enlarged curves of (a) and (c), respectively. The peaks of electrolyte decomposition and side reactions are marked with black asterisks. The peaks of irreversible phase transition are marked with red asterisks. The red arrows reveal the changes at the cathodic/anodic peaks.

The differences in the electrochemical performance using PVDF or SA as the binder were evaluated in detail (Figure 6). The rate capability of the samples was tested from 0.1 to 20 C (Figure 6a). Even at 20 C, TiO2 anode with SA binder exhibits high capacity of 82 mAh g-1. In contrast, the cell using traditional PVDF binder delivers significantly lower capacities of only 8 mAh g-1 at 20 C. In particularly, TiO2 anode with SA binder exhibits a satisfactory capacity of 180 mAh g-1 with no decay after 500 cycles at 1 C (Figure 6b). However, TiO2/PVDF anode shows poor stability and

ACS Paragon Plus Environment

Page 14 of 29

Page 15 of 29 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 Applied Materials & Interfaces

capacity (Figure 6b). Moreover, at a high rate of 10 C, the cell using SA binder displays high capacity of 82 mAh g-1 even after 3600 cycles (Figure 6c). The average coulombic efficiency is up to 99.97%. Clearly, the TiO2 electrode using SA as the binder shows the excellent sodium storage capacity and super durable stability at high rates.

Figure 6 (a) Rate performance at the different rates and (b) Cycling stability at 1 C of TiO2/PVDF or TiO2/SA anode. (c) Cycling stability at 10 C of cell using SA binder. The cells of (b) and (c) were tested after activated at 0.1 C for three cycles.

To investigate the effect of the binders on the electrode morphology, the electrodes were disassembled after cycling. We can observe the significant morphologies difference of the TiO2/PVDF and TiO2/SA electrodes after cycling (Figure 7). Compared to the pristine electrodes (Figure 2c), the whole surface of TiO2/PVDF electrode is covered by a clearly visible film (Figure 7a). It demonstrates the formation of solid electrolyte interface (SEI) films, causing the extra electrolyte

ACS Paragon Plus Environment

ACS Applied Materials & Interfaces 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

decomposition and large capacity loss. What’s more, such a thick and densely closed membranous layer will greatly affect the Na+ ions migration within the SEI film, thus degrading the electrochemical performance. Specially, there are some obvious cracks (Figure 7b) on its surface, indicating the weak adhesion between particles and finally giving rise to a poor stability.61 Nevertheless, the morphologies of TiO2/SA electrode can still be maintained well after cycling, indicating an excellent structural stability (Figures 7c-d). Obviously, the TiO2/PVDF anode suffers from severe changes during the cycling.

Figure 7 SEM images of the TiO2/PVDF (a, b) and TiO2/SA (c, d) electrodes after cycling.

Besides, Figure 8 presents the cross-section images of the electrodes for TiO2/PVDF and TiO2/SA. When PVDF was used as the binder, a small gap is found between the electrode layer and the current collector (Figure 8a). The gap largely expands after cycling, causing current collector to detach (Figure 8b). However, the

ACS Paragon Plus Environment

Page 16 of 29

Page 17 of 29 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 Applied Materials & Interfaces

TiO2/SA electrode layer on the pristine electrode slice displays good adherence to the current collector (Figure 8c), and tightly connected even after 500 cycles at 1 C (Figure 8d). We also calculated the binding energy of the binder with Cu foil. As shown in Scheme 1, the binding energy of SA binder with Cu foil is 13.07 eV, which is much higher than EPVDF-Cu (only 5.95 eV). It demonstrates the strong binding effect of SA binder with Cu foil, thus showing a favorable TiO2/SA electrode morphology.

Figure 8 Cross-sections morphologies of the pristine TiO2/PVDF (a) and TiO2/SA (c) electrodes. Cross-sections morphologies of the TiO2/PVDF (b) and TiO2/SA (d) electrodes after 500 cycles at 1 C. The layer of electrode materials is marked with the red arrow.

To get insight into the robustness of the rate capability for TiO2/SA electrode, cyclic voltammetry (CV) was performed as shown in Figure 9a. The cells were cycled for 3 times at 0.1 C before the CV test. A pair of peaks at 0.85 V (anodic) and 0.55 V

ACS Paragon Plus Environment

ACS Applied Materials & Interfaces 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

(cathodic) is detected for TiO2/PVDF electrode, while these respective strong peaks are at 0.85 V (anodic) and 0.65 V (cathodic) for TiO2/SA electrode. It corresponds to the reversible sodium ions storage in the TiO2 material with the Ti3+/Ti4+ redox. The current of TiO2/SA electrode is much higher than the TiO2/PVDF electrode. TiO2/SA electrode also displays the sharper peak shape and the lower voltage difference (0.2 V) in the oxidation reduction peak. It demonstrates the high electrochemical reaction activity, good reversibility and small polarization of TiO2 anode using SA as the binder.62 Electrochemical impedance spectroscopy is applied to reveal the detailed interfacial kinetics and polarization types of the electrode with PVDF or SA binder. Figures 9b-c show the Nyquist plots of TiO2/PVDF and TiO2/SA electrodes after the 5th cycles. An intercept at the Z' axis at high frequency indicates the ohmic resistance of the tested battery (Rs). Both Nyquist plots display two depressed semi-circles in the high and medium frequency region, showing similar shapes but obvious differences in the impedance values. The first semicircle corresponds to SEI surface impedance (RSEI) and constant phase element (CPE). The second depressed semicircle is associated with the Na ions transport through the interfacial charge transfer reaction (Rct) combined with the double-layer capacitance across the surface (Cdl). In addition, an approximately 45° slope line is found in the low-frequency region for the two electrodes, standing for the Warburg impedance (ZW) related to the solid-state Na ions diffusion in the bulk of the active materials.

ACS Paragon Plus Environment

Page 18 of 29

Page 19 of 29 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 Applied Materials & Interfaces

Figure 9 (a) CV measurements of TiO2/PVDF and TiO2/SA electrodes with the 0.1 mV s-1 scan rate and the 0.02-2.5 V (versus Na/Na+) voltage range. The overall (b) and the enlarged (c) Nyquist plot of TiO2 electrode using PVDF or SA as the binder. (d) The Z’ vs. ω-1/2 plots in the low frequency region. (e) Equivalent circuit that is used to fit the experimental data.

Figure 9e illustrates the typical equivalent model, which fits and interprets well to the impedance spectra for the electrodes after discharge.63 The CPE, Cdl, and Cint are constant phase element, double-layer capacitance, and the interaction capacitance, respectively. The fitted impedance parameters are listed in Table 2. The TiO2/SA electrode exhibits rather lower impedance than TiO2/PVDF including the Rs, RSEI and Rct. Therefore, SA can greatly enhance the SEI surface conductivity and

ACS Paragon Plus Environment

ACS Applied Materials & Interfaces 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 29

electrochemical reactivity at the surface/interface region. SA plays a positive role in the charge transfer process, thus lowering the polarization of the TiO2 anodes.

Table 2 Properties of the TiO2/PVDF and TiO2/SA electrodes from EIS spectra Electrode

Rs (Ω)

RSEI (Ω)

Rct (Ω)

DNa (cm2 s-1)

TiO2/PVDF TiO2/SA

5.4 3.4

77.8 34.3

457.4 24.8

4.44×10-15 5.5×10-13

The apparent sodium diffusion coefficient, D (cm2 s-1), can be calculated from the inclined

 =

lines

in

the

Warburg

region

using

the

following

equation,

2 2 2 2 , where R is the gas constant, T is the absolute temperature, A is 2 4 4 2

the surface area of the electrode, n is the charge-transfer number, F is the Faraday constant (96485 C mol-1), C is the concentration of Na ions in the solid (0.01625 mol cm-3), and σ is the Warburg factor that can be obtained by plotting in the complex plane ’  =  / against ω-1/2, where ω is angular frequency (Figure 9d). The DNa of TiO2/SA electrode is calculated to be 5.5×10-13 cm2 s-1, which is beyond 100 times significantly higher than TiO2/PVDF (4.44×10-15 cm2 s-1). Here, since the diffusion depends on the concentration gradient, the apparent diffusion coefficient can be influenced by the different interfacial behaviors.64 The obvious differences in the electrochemistry performance can be ascribed to the two orders of magnitude increase of TiO2/SA electrode in apparent diffusion coefficient, along with the less charge transfer resistance and the decreasing resistance from the SEI layer. As revealed above, the sodium storage performance of anatase TiO2 has been greatly promoted by using SA as the binder. The potential reasons are analyzed as

ACS Paragon Plus Environment

Page 21 of 29 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 Applied Materials & Interfaces

follows and depicted in Scheme 1: (a) In a dry or wet (impregnated with electrolyte solvent) state, SA binder demonstrates to be a higher Young’s modulus, showing negligibly small swellability and weak polymer/electrolyte interaction44, which contributes to preventing undesirable access of electrolyte liquid to the binder/TiO2 interface, leading to the super durable stability. In contrast, during cycling, more and more PVDF binder will dissolve in the electrolytes, which causes the gelation of PVDF and electrolyte, and then leads to continuously covering on the electrode.65 A membranous layer is so thick that it will greatly affect the Na+ ions migration within the SEI film, thus degrading the electrochemical performance. (b) SA binder possesses the carboxylic groups with high concentration, uniform distribution and strong polarity in the polymer chain. The polar group can react with the hydroxyl groups on the surfaces of TiO2 microparticales, forming the hydrogen bonding and thus strong adhesion.66 As the FTIR spectra of SA binder shows, the 1300 cm-1 peak is related to pyranose-ring deformation vibrations.45 After electrode formation with TiO2, its relative intensity obviously decreases (Figure S2), indicating a chemical interaction between SA and TiO2 particles.67 However, for PVDF binder, the very weak hydrogen bond force with F and TiO2 surface, and the weak Van der Waals force result in relatively weak adhesion.68 Furthermore, the high crystallinity of PVDF originated from its part bundled main chains can decrease the amount of PVDF binding site with TiO2, thus further lowering the adhesion.69 The differences in molecular structures can highly influence the binding abilities of different binders, thus resulting in different changes in the electrode morphologies. (c) The polar hydrogen bonds between

ACS Paragon Plus Environment

ACS Applied Materials & Interfaces 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

carboxyl groups of SA and the hydroxylated surface of TiO2 also potentially contribute to forming the thin and stable SEI films, promoting a high CE and long cycle life.70

4. CONCLUSION In this work, for the first time, we developed a facile and scalable strategy utilizing SA as the

binder to fabricate

high-performance, low-cost and

eco-friendliness durable TiO2 anode for SIBs. The SA binder plays the key role of a functional agent in enhancing the initial coulombic efficiency, rate capability and cycling stability. TiO2 anode with SA binder exhibits a remarkable capacity of 180 mAh g-1 with no decay after 500 cycles at 1 C. Even at 10 C (3.4 A g-1), it remains a capacity of 82 mAh g-1 after 3600 cycles with 99.97% average coulombic efficiency, which are attributed to the larger apparent diffusion coefficient, the less charge transfer resistance and the decreasing resistance from the SEI layer. In contrast, the cell using PVDF as the binder displays poor performance. Less electrolyte decomposition and side reaction, high electrochemistry reaction activity, effective suppression of polarization, and good electrode morphology depend on the special structure and characteristic of SA binder with rich carboxylic groups, high Young’s modulus, and good electrochemical stability. Our work not only proves that sodium alginate is effective and significant binder in TiO2 anode, but also delivers a new idea for improving electrochemical performances of SIBs.

ACS Paragon Plus Environment

Page 22 of 29

Page 23 of 29 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 Applied Materials & Interfaces

Supporting Information

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acsami.******. Energy dispersive X-ray (EDX) mapping of pristine TiO2 electrodes, and FTIR spectra of SA/TiO2 electrode (PDF)

AUTHOR INFORMATION Corresponding Author *E-mail: [email protected] (Y. Bai); [email protected] (C. Wu).

NOTES The authors declare no competing financial interest.

ACKNOWLEDGMENTS The present work is supported by the National Basic Research Program of China (Grant No. 2015CB251100).

REFERENCES (1) (2)

(3) (4) (5) (6) (7)

Dunn, B.; Kamath, H.; Tarascon, J.-M. Electrical Energy Storage for the Grid: A Battery of Choices. Science 2011, 334, 928–935. Luo, W.; Chen, X. Q.; Xia, Y.; Chen, M.; Wang, L. J.; Wang, Q. Q.; Li, W.; Yang, J. P. Surface and Interface Engineering of Silicon-Based Anode Materials for Lithium-Ion Batteries. Adv. Energy Mater. 2017, 7, 1701083–1701110. Tarascon, J.-M. Is Lithium the New Gold? Nat. Chem. 2010, 2, 510–510. Jy, H.; St, M.; Yk, S. Sodium-Ion Batteries: Present and Future. Chem. Soc. Rev. 2017, 46, 3529–3614. Hong, S. Y.; Kim, Y.; Park, Y.; Choi, A.; Choi, N.-S.; Lee, K. T. Charge Carriers in Rechargeable Batteries: Na Ions vs. Li Ions. Energy Environ. Sci. 2013, 6, 2067–2081. Han, M. H.; Gonzalo, E.; Singh, G.; Rojo, T. A Comprehensive Review of Sodium Layered Oxides: Powerful Cathodes for Na-Ion Batteries. Energy Environ. Sci. 2015, 8, 81–102. Xiang, X. D.; Zhang, K.; Chen, J. Recent Advances and Prospects of Cathode Materials for Sodium-Ion Batteries. Adv. Mater. 2015, 27, 5343–5364.

ACS Paragon Plus Environment

ACS Applied Materials & Interfaces 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

(8)

(9)

(10)

(11) (12) (13)

(14)

(15)

(16)

(17) (18) (19)

(20)

(21)

(22)

(23)

Fang, C.; Huang, Y. H.; Zhang, W. X.; Han, J. T.; Deng, Z.; Cao, Y. L.; Yang, H. X. Routes to High Energy Cathodes of Sodium-Ion Batteries. Adv. Energy Mater. 2016, 6, 1501727– 1501744. Li, H.; Bai, Y.; Wu, F.; Ni, Q.; Wu, C. Na-Rich Na3+xV2-xNix(PO4)3/C for Sodium Ion Batteries: Controlling the Doping Site and Improving the Electrochemical Performances. ACS Appl. Mater. Interfaces 2016, 8, 27779–27787. Bai, Y.; Zhao, L. X.; Wu, C.; Li, H.; Li, Y.; Wu, F. Enhanced Sodium Ion Storage Behavior of P2-Type Na2/3Fe1/2Mn1/2O2 Synthesized via a Chelating Agent Assisted Route. ACS Appl. Mater. Interfaces 2016, 8, 2857–2865. Ni, Q.; Bai, Y.; Wu, F.; Wu, C. Polyanion-Type Electrode Materials for Sodium-Ion Batteries. Adv. Sci. 2017, 4, 1600275–1600298. Li, H.; Wu, C.; Bai, Y.; Wu, F.; Wang, M. Z. Controllable Synthesis of High-Rate and Long Cycle-Life Na3V2(PO4)3 for Sodium-Ion Batteries. J. Power Sources 2016, 326, 14–22. Li, H.; Yu, X. Q.; Bai, Y.; Wu, F.; Wu, C.; Liu, L. Y.; Yang, X. Q. Effects of Mg Doping on the Remarkably Enhanced Electrochemical Performance of Na3V2(PO4)3 Cathode Materials for Sodium Ion Batteries. J. Mater. Chem. A 2015, 3, 9578–9586. Li, H.; Bi, X. X.; Bai, Y.; Yuan, Y. F.; Shahbazian-Yassar, R.; Wu, C.; Wu, F.; Lu, J.; Amine, K. High-Rate, Durable Sodium-Ion Battery Cathode Enabled by Carbon-Coated Micro-Sized Na3V2(PO4)3 Particles with Interconnected Vertical Nanowalls. Adv. Mater. Interfaces 2016, 3, 1500740–1500747. Fang, Y. J.; Xiao, L. F.; Ai, X. P.; Cao, Y. L.; Yang, H. X. Hierarchical Carbon Framework Wrapped Na3V2(PO4)3 as a Superior High-Rate and Extended Lifespan Cathode for Sodium-Ion Batteries. Adv. Mater. 2015, 27, 5895–5900. Wang, Y. S.; Xiao, R. J.; Hu, Y.-S.; Avdeev, M. X.; Chen, L. Q. P2-Na0.6[Cr0.6Ti0.4]O2 Cation-Disordered Electrode for High-Rate Symmetric Rechargeable Sodium-Ion Batteries. Nat. Commun. 2015, 6, 6954–6962. Luo, W.; Shen, F.; Bommier, C.; Zhu, H.; Ji, X.; Hu, L. Na-Ion Battery Anodes: Materials and Electrochemistry. Acc. Chem. Res. 2016, 49, 231–240. Bommier, C.; Ji, X. Recent Development on Anodes for Na-Ion Batteries. Isr. J. Chem. 2015, 55, 486–507. Bai, Y.; Wang, Z.; Wu, C.; Xu, R.; Wu, F.; Liu, Y. C.; Li, H.; Li, Y.; Lu, J.; Amine, K. Hard Carbon Originated from Polyvinyl Chloride Nanofibers As High-Performance Anode Material for Na-Ion Battery. ACS Appl. Mater. Interfaces 2015, 7, 5598–5604. Bai, Y.; Liu, Y. C.; Li, Y.; Ling, L. M.; Wu, F.; Wu, C. Mille-Feuille Shaped Hard Carbons Derived from Polyvinylpyrrolidone via Environmentally Friendly Electrostatic Spinning for Sodium Ion Battery Anodes. RSC Adv. 2017, 7, 5519–5527. Fang, Y. J.; Xiao, L. F.; Qian, J. F.; Cao, Y. L.; Ai, X. P.; Huang, Y. H.; Yang, H. X. 3D Graphene Decorated NaTi2(PO4)3 Microspheres as a Superior High-Rate and Ultracycle-Stable Anode Material for Sodium Ion Batteries. Adv. Energy Mater. 2016, 6, 1502197–1502204. Qiu, S.; Xiao, L. F.; Sushko, M. L.; Han, K. S.; Shao, Y. Y.; Yan, M. Y.; Liang, X. M.; Mai, L. Q.; Feng, J. W.; Cao, Y. L.; Ai, X. P.; Yang, H. X.; Liu, J. Manipulating Adsorption–Insertion Mechanisms in Nanostructured Carbon Materials for High-Efficiency Sodium Ion Storage. Adv. Energy Mater. 2017, 7, 1700403–1700413. Luo, W.; Bommier, C.; Jian, Z. L.; Li, X.; Carter, R.; Vail, S.; Lu, Y. H.; Lee, J.-J.; Ji, X. L.

ACS Paragon Plus Environment

Page 24 of 29

Page 25 of 29 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 Applied Materials & Interfaces

(24) (25)

(26) (27)

(28)

(29)

(30)

(31)

(32)

(33) (34)

(35)

(36)

(37)

(38)

Low-Surface-Area Hard Carbon Anode for Na-Ion Batteries via Graphene Oxide as a Dehydration Agent. Acs Appl. Mater. Interfaces 2015, 7, 2626–2631. Sun, N.; Liu, H.; Xu, B. Facile Synthesis of High Performance Hard Carbon Anode Materials for Sodium Ion Batteries. J. Mater. Chem. A 2015, 3, 20560–20566. Wang, Q. D.; Zhao, C. L.; Lu, Y. X.; Li, Y. M.; Zheng, Y. H.; Qi, Y. R.; Rong, X. H.; Jiang, L. W.; Qi, X. G.; Shao, Y. J.; Pan, D.; Li, B. H.; Hu, Y.-S.; Chen, L. Q. Advanced Nanostructured Anode Materials for Sodium-Ion Batteries. Small 2017, 13, 1701835–1701866. Aravindan, V.; Lee, Y.-S.; Yazami, R.; Madhavi, S. TiO2 Polymorphs in “rocking-Chair” Li-Ion Batteries. Mater. Today 2015, 18, 345–351. Cao, K. Z.; Jiao, L. F.; Pang, W. K.; Liu, H. Q.; Zhou, T. F.; Guo, Z. P.; Wang, Y. J.; Yuan, H. T. Na2Ti6O13 Nanorods with Dominant Large Interlayer Spacing Exposed Facet for High-Performance Na-Ion Batteries. Small 2016, 12, 2991–2997. Chen, C. J.; Xu, H. H.; Zhou, T. F.; Guo, Z. P.; Chen, L. N.; Yan, M. Y.; Mai, L. Q.; Hu, P.; Cheng, S. J.; Huang, Y. H.; Xie, J. Integrated Intercalation-Based and Interfacial Sodium Storage in Graphene-Wrapped Porous Li4Ti5O12 Nanofibers Composite Aerogel. Adv. Energy Mater. 2016, 6, 1600322–1600329. Luo, W.; Wang, Y. X.; Wang, L. J.; Jiang, W.; Chou, S.-L.; Dou, S. X.; Liu, H. K.; Yang, J. P. Silicon/Mesoporous Carbon/Crystalline TiO2 Nanoparticles for Highly Stable Lithium Storage. ACS Nano 2016, 10, 10524–10532. Yang, J. P.; Wang, Y. X.; Li, W.; Wang, L. J.; Fan, Y. C.; Jiang, W.; Luo, W.; Wang, Y.; Kong, B.; Selomulya, C.; Liu, H. K.; Dou, S. X.; Zhao, D. Y. Amorphous TiO2 Shells: A Vital Elastic Buffering Layer on Silicon Nanoparticles for High-Performance and Safe Lithium Storage. Adv. Mater. 2017, 29, 1700523–1700529. Zhou, T. F.; Zheng, Y.; Gao, H.; Min, S. D.; Li, S.; Liu, H. K.; Guo, Z. P. Surface Engineering and Design Strategy for Surface-Amorphized TiO2@Graphene Hybrids for High Power Li-Ion Battery Electrodes. Adv. Sci. 2015, 2, 1500027–1500034. Lunell S.; Stashans A.; Ojamäe L.; Lindström H.; Hagfeldt, A. Li and Na Diffusion in TiO2 from Quantum Chemical Theory versus Electrochemical Experiment. J. Am. Chem. Soc. 1997, 119, 7374–7380. Su, D. W.; Dou, S. X.; Wang, G. X. Anatase TiO2: Better Anode Material than Amorphous and Rutile Phases of TiO2 for Na-Ion Batteries. Chem. Mater. 2015, 27, 6022–6029. Xiong, Y.; Qian, J. F.; Cao, Y. L.; Ai, X. P.; Yang, H. X. Electrospun TiO2/C Nanofibers As a High-Capacity and Cycle-Stable Anode for Sodium-Ion Batteries. ACS Appl. Mater. Interfaces 2016, 8, 16684–16689. Wang, B. F.; Zhao, F.; Du, G. D.; Porter, S.; Liu, Y.; Zhang, P.; Cheng, Z. X.; Liu, H. K.; Huang, Z. G. Boron-Doped Anatase TiO2 as a High-Performance Anode Material for Sodium-Ion Batteries. ACS Appl. Mater. Interfaces 2016, 8, 16009–16015. Liu, H.; Cao, K.; Xu, X.; Jiao, L.; Wang, Y.; Yuan, H. Ultrasmall TiO2 Nanoparticles in Situ Growth on Graphene Hybrid as Superior Anode Material for Sodium/Lithium Ion Batteries. ACS Appl. Mater. Interfaces 2015, 7, 11239–11245. Zhang, Y.; Wang, C. W.; Hou, H. S.; Zou, G. Q.; Ji, X. B. Nitrogen Doped/Carbon Tuning Yolk-Like TiO2 and Its Remarkable Impact on Sodium Storage Performances. Adv. Energy Mater. 2017, 7, 1600173–1600184. Longoni, G.; Pena Cabrera, R. L.; Polizzi, S.; D’Arienzo, M.; Mari, C. M.; Cui, Y.; Ruffo, R.

ACS Paragon Plus Environment

ACS Applied Materials & Interfaces 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

(39)

(40)

(41)

(42)

(43)

(44)

(45)

(46)

(47)

(48)

(49)

(50)

(51)

(52)

Shape-Controlled TiO2 Nanocrystals for Na-Ion Battery Electrodes: The Role of Different Exposed Crystal Facets on the Electrochemical Properties. Nano Lett. 2017, 17, 992–1000. Wu, Y.; Jiang, Y.; Shi, J.; Gu, L.; Yu, Y. Multichannel Porous TiO2 Hollow Nanofibers with Rich Oxygen Vacancies and High Grain Boundary Density Enabling Superior Sodium Storage Performance. Small 2017, 13, 1700129–1700136. Yan, X.; Zhang, Y. Q.; Zhu, K.; Gao, Y.; Zhang, D.; Chen, G.; Wang, C. Z.; Wei, Y. J. Enhanced Electrochemical Properties of TiO2(B) Nanoribbons Using the Styrene Butadiene Rubber and Sodium Carboxyl Methyl Cellulose Water Binder. J. Power Sources 2014, 246, 95–102. Han, Z.-J.; Yabuuchi, N.; Shimomura, K.; Murase, M.; Yui, H.; Komaba, S. High-Capacity Si– graphite Composite Electrodes with a Self-Formed Porous Structure by a Partially Neutralized Polyacrylate for Li-Ion Batteries. Energy Environ. Sci. 2012, 5, 9014–9020. Koo, B.; Kim, H.; Cho, Y.; Lee, K. T.; Choi, N.-S.; Cho, J. A Highly Cross-Linked Polymeric Binder for High-Performance Silicon Negative Electrodes in Lithium Ion Batteries. Angew. Chem. Int. Ed. 2012, 51, 8762–8767. Liu, Y. J.; Tai, Z. X.; Zhou, T. F.; Sencadas, V.; Zhang, J.; Zhang, L.; Konstantinov, K.; Guo, Z. P.; Liu, H. K. An All-Integrated Anode via Interlinked Chemical Bonding between Double-Shelled–Yolk-Structured Silicon and Binder for Lithium-Ion Batteries. Adv. Mater. 2017, 29, 1703028–1703038. Kovalenko, I.; Zdyrko, B.; Magasinski, A.; Hertzberg, B.; Milicev, Z.; Burtovyy, R.; Luzinov, I.; Yushin, G. A Major Constituent of Brown Algae for Use in High-Capacity Li-Ion Batteries. Science 2011, 334, 75–79. Fenoradosoa, T. A.; Ali, G.; Delattre, C.; Laroche, C.; Petit, E.; Wadouachi, A.; Michaud, P. Extraction and Characterization of an Alginate from the Brown Seaweed Sargassum Turbinarioides Grunow. J. Appl. Phycol. 2010, 22, 131–137. Han, P.; Fan, J.; Jing, M.; Zhu, L.; Shen, X.; Pan, T. Effects of Reduced Graphene on Crystallization Behavior, Thermal Conductivity and Tribological Properties of Poly(vinylidene Fluoride). J. Compos. Mater. 2013, 48, 659–666. Xu, Y.; Memarzadeh Lotfabad, E.; Wang, H.; Farbod, B.; Xu, Z.; Kohandehghan, A.; Mitlin, D. Nanocrystalline Anatase TiO2: A New Anode Material for Rechargeable Sodium Ion Batteries. Chem. Commun. 2013, 49, 8973–8975. Kim, K.-T.; Ali, G.; Chung, K. Y.; Yoon, C. S.; Yashiro, H.; Sun, Y.-K.; Lu, J.; Amine, K.; Myung, S.-T. Anatase Titania Nanorods as an Intercalation Anode Material for Rechargeable Sodium Batteries. Nano Lett. 2014, 14, 416–422. Oh, S.-M.; Hwang, J.-Y.; Yoon, C. S.; Lu, J.; Amine, K.; Belharouak, I.; Sun, Y.-K. High Electrochemical Performances of Microsphere C-TiO2 Anode for Sodium-Ion Battery. ACS Appl. Mater. Interfaces 2014, 6, 11295–11301. Wu, L. M.; Bresser, D.; Buchholz, D.; Giffin, G. A.; Castro, C. R.; Ochel, A.; Passerini, S. Unfolding the Mechanism of Sodium Insertion in Anatase TiO2 Nanoparticles. Adv. Energy Mater. 2015, 5, 1401142–1401152. Yang, X. M.; Wang, C.; Yang, Y. C.; Zhang, Y.; Jia, X. N.; Chen, J.; Ji, X. B. Anatase TiO2 Nanocubes for Fast and Durable Sodium Ion Battery Anodes. J. Mater. Chem. A 2015, 3, 8800–8807. Chen, C. J.; Wen, Y. W.; Hu, X. L.; Ji, X. L.; Yan, M. Y.; Mai, L. Q.; Hu, P.; Shan, B.; Huang, Y. H. Na+ Intercalation Pseudocapacitance in Graphene-Coupled Titanium Oxide Enabling

ACS Paragon Plus Environment

Page 26 of 29

Page 27 of 29 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 Applied Materials & Interfaces

(53)

(54) (55)

(56)

(57)

(58)

(59)

(60)

(61)

(62)

(63) (64)

(65)

(66)

(67)

Ultra-Fast Sodium Storage and Long-Term Cycling. Nat. Commun. 2015, 6, 6929–6936. Xu, Y.; Zhou, M.; Wen, L. Y.; Wang, C. L.; Zhao, H. P.; Mi, Y.; Liang, L. Y.; Fu, Q.; Wu, M. H.; Lei, Y. Highly Ordered Three-Dimensional Ni-TiO2 Nanoarrays as Sodium Ion Battery Anodes. Chem. Mater. 2015, 27, 4274–4280. Hong, Z.; Zhou, K.; Huang, Z.; Wei, M. Iso-Oriented Anatase TiO2 Mesocages as a High Performance Anode Material for Sodium-Ion Storage. Sci. Rep. 2015, 5, 11960–11969. Tahir, M. N.; Oschmann, B.; Buchholz, D.; Dou, X. W.; Lieberwirth, I.; Panthöfer, M.; Tremel, W.; Zentel, R.; Passerini, S. Extraordinary Performance of Carbon-Coated Anatase TiO2 as Sodium-Ion Anode. Adv. Energy Mater. 2016, 6, 1501489–1501497. Ni, J. F.; Fu, S. D.; Wu, C.; Maier, J.; Yu, Y.; Li, L. Self-Supported Nanotube Arrays of Sulfur-Doped TiO2 Enabling Ultrastable and Robust Sodium Storage. Adv. Mater. 2016, 28, 2259–2265. Wu, Y.; Liu, X. W.; Yang, Z. Z.; Gu, L.; Yu, Y. Nitrogen-Doped Ordered Mesoporous Anatase TiO2 Nanofibers as Anode Materials for High Performance Sodium-Ion Batteries. Small 2016, 12, 3522–3529. Zhang, W. F.; Lan, T. B.; Ding, T. L.; Wu, N.-L.; Wei, M. D. Carbon Coated Anatase TiO2 Mesocrystals Enabling Ultrastable and Robust Sodium Storage. J. Power Sources 2017, 359, 64–70. Reeve, Z. E. M.; Franko, C. J.; Harris, K. J.; Yadegari, H.; Sun, X.; Goward, G. R. Detection of Electrochemical Reaction Products from the Sodium-Oxygen Cell with Solid-State Na-23 NMR Spectroscopy. J. Am. Chem. Soc. 2017, 139, 595–598. Xu, B.; Choi, J.; Borca, C. N.; Dowben, P. A.; Sorokin, A. V.; Palto, S. P.; Petukhova, N. N.; Yudin, S. G. Comparison of Aluminum and Sodium Doped Poly(vinylidene Fluoride-Trifluoroethylene) Copolymers by X-Ray Photoemission Spectroscopy. Appl. Phys. Lett. 2001, 78, 448–450. Ming, J.; Ming, H.; Kwak, W. J.; Shin, C. D.; Zheng, J. W.; Sun, Y.-K. The Binder Effect on an Oxide-Based Anode in Lithium and Sodium-Ion Battery Applications: The Fastest Way to Ultrahigh Performance. Chem. Commun. 2014, 50, 13307–13310. Wei, Q. L.; An, Q. Y.; Chen, D. D.; Mai, L. Q.; Chen, S. Y.; Zhao, Y. L.; Hercule, K. M.; Xu, L.; Minhas-Khan, A.; Zhang, Q. J. One-Pot Synthesized Bicontinuous Hierarchical Li3V2(PO4)3/C Mesoporous Nanowires for High-Rate and Ultralong-Life Lithium-Ion Batteries. Nano Lett. 2014, 14, 1042–1048. Li, L.; Raji, A.-R. O.; Tour, J. M. Graphene-Wrapped MnO2-Graphene Nanoribbons as Anode Materials for High-Performance Lithium Ion Batteries. Adv. Mater. 2013, 25, 6298–6302. Kim, D. J.; Ponraj, R.; Kannan, A. G.; Lee, H.-W.; Fathi, R.; Ruffo, R.; Mari, C. M.; Kim, D. K. Diffusion Behavior of Sodium Ions in Na0.44MnO2 in Aqueous and Non-Aqueous Electrolytes. J. Power Sources 2013, 244, 758–763. Buqa, H.; Holzapfel, M.; Krumeich, F.; Veit, C.; Novák, P. Study of Styrene Butadiene Rubber and Sodium Methyl Cellulose as Binder for Negative Electrodes in Lithium-Ion Batteries. J. Power Sources 2006, 161, 617–622. Komaba, S.; Shimomura, K.; Yabuuchi, N.; Ozeki, T.; Yui, H.; Konno, K. Study on Polymer Binders for High-Capacity SiO Negative Electrode of Li-Ion Batteries. J. Phys. Chem. C 2011, 115, 13487–13495. Papageorgiou, S. K.; Kouvelos, E. P.; Favvas, E. P.; Sapalidis, A. A.; Romanos, G. E.; Katsaros,

ACS Paragon Plus Environment

ACS Applied Materials & Interfaces 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

(68) (69)

(70)

F. K. Metal–carboxylate Interactions in Metal–alginate Complexes Studied with FTIR Spectroscopy. Carbohydr. Res. 2010, 345, 469–473. Gong, L. Y.; Nguyen, M. H. T.; Oh, E.-S. High Polar Polyacrylonitrile as a Potential Binder for Negative Electrodes in Lithium Ion Batteries. Electrochem. Commun. 2013, 29, 45–47. Yabuuchi, N.; Shimomura, K.; Shimbe, Y.; Ozeki, T.; Son, J.-Y.; Oji, H.; Katayama, Y.; Miura, T.; Komaba, S. Graphite-Silicon-Polyacrylate Negative Electrodes in Ionic Liquid Electrolyte for Safer Rechargeable Li-Ion Batteries. Adv. Energy Mater. 2011, 1, 759–765. Wu, H.; Chan, G.; Choi, J. W.; Ryu, I.; Yao, Y.; Mcdowell, M. T.; Lee, S. W.; Jackson, A.; Yang, Y.; Hu, L. Stable Cycling of Double-Walled Silicon Nanotube Battery Anodes through Solid-Electrolyte Interphase Control. Nat. Nanotechnol. 2012, 7, 310–315.

ACS Paragon Plus Environment

Page 28 of 29

Page 29 of 29 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 Applied Materials & Interfaces

ACS Paragon Plus Environment