C Nanofibers As a High-Capacity and Cycle-Stable

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Electrospun TiO2/C nanofibers as a high-capacity and cycle-stable anode for sodium ion batteries Ya Xiong, Jiangfeng Qian, Yuliang Cao, Xinping Ai, and Hanxi Yang ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.6b03757 • Publication Date (Web): 17 Jun 2016 Downloaded from http://pubs.acs.org on June 21, 2016

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ACS Applied Materials & Interfaces

Electrospun TiO2/C nanofibers as a high-capacity and cycle-stable anode for sodium ion batteries Ya Xiong, Jiangfeng Qian, Yuliang Cao, Xinping Ai, Hanxi Yang* * College of Chemistry and Molecular Sciences, Wuhan University, Wuhan 430072, China.

ABSTRACT: Nanosized TiO2 is now actively developed as a low-cost and potentially high capacity anode material of Na-ion batteries, but its poor capacity utilization and insufficient cyclability remains an obstacle for battery applications. To overcome these drawbacks, we synthesized electrospun TiO2/C nanofibers, where anatase TiO2 nanocrystals with a diameter of ~12 nm were densely embedded in the conductive carbon fibers, thus preventing them from aggregating and attacking by electrolyte. Due to its abundant active surfaces of well-dispersed TiO2 nanocrytals and high electronic conductivity of the carbon matrix, the TiO2/C anode shows a high redox capacity of ~302.4 mA h g-1 and a hiogh-rate capability of 164.9 mAh g-1 at a very high current of 2000 mA g-1. More significantly, this TiO2/C anode can be cycled with nearly 100% capacity retention over 1000 cycles, showing a sufficiently long cycle life for battery applications. The nanofibrous architecture of the TiO2/C composite and its superior electrochemical performance may provide new insights for development of better host materials for practical Na-ion batteries.

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KEYWORDS: TiO2/C nanofibers; Electrospinning synthesis; Na-insertion anode; Sodium ion batteries; Long cycle life. INTRODUCTION Low cost and long life rechargeable batteries are now in great demand for ever-increasing electric storage applications.1-3 Though lithium ion batteries have successfully used for powering electric vehicles and tested for distributed power stations, their large-scale applications is still a serious concern about the high costs and limited resources of Li reserves on earth. In fact, sodium ion batteries (SIBs) have similar electrochemical performance but potentially much lower cost to their lithium counterparts because of the widespread availability of sodium resources, thus making them a competitive candidate for electric storage applications.4-5 In recent years, a great effort has been devoted to find suitable materials for Na-storage reaction and a variety of cathodic hosts, such as transition-metal oxides,6-8 polyanionic phosphates9-11 and Prussian blue analogues,12 have been revealed to deliver acceptable Na+-insertion capacity with certain cyclability. In contrast, only few of anode materials are reported to have decent Nastorage performance up to data. Despite a few of hard carbons were revealed to have considerable Na-storage capability, their low potential and large polarization are a severe concern for battery application.13 Quite a large array of alloy compounds such as Sn, Sb and their sulfides and phosphides have shown high reversible capacities for Na-storage anodes,14-19 However, the structural instability due to their large volume change during charge-discharge cycles is still a big obstacle as in the case of Li-insertion electrodes.20-21 Therefore, it is still a challenge to search for low cost and cycling-stable anode materials for development of practically viable SIBs.


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Titanium dioxide (TiO2), a low cost, structurally stable and environmentally benign anode material, has been recently proved to be a promising Na(Li)-insertion anode with adequately high reversible capacity and good cyclability.22-24 Several polymorphs of TiO2, such as amorphous,25-26 anatase,27-29 rutile,30-31 TiO2(B)32-33 and TiO2 (H),34 have been proposed as anode hosts for SIBs; however, these materials exhibited a large diversity in the electrochemical Nastorage performance. Recently, Wang et al. reported electrochemical properties of different phases of TiO2 nanospheres and found that anatase TiO2 has a better Na-storage capability than mixed anatase/rutile or amorphous TiO2.35 Several groups have combined the nanoarchitectural design with conductive composite engineering to improve the capacity utilization of TiO2.36-37 However, most of the nanostructured TiO2/C composites reported so far have a limited reversible capacity less than 200 mA h g-1 35, 38 and only a few of them can deliver a higher capacity of 250 mA h g-1 at low rates.

39-40

Nevertheless, all the pioneering works seem to suggest that one-

dimensional nanosized anatase TiO2 is advantageous for achieving higher capacity utilization and rate capability as a Na-insertion anode. 41-43 In this work, we report the synthesis of anatase TiO2/carbon nanofibers (TiO2/C) through an electrospinning process and the electrochemical performance of this material as a Na+ insertion anode. Due to the one-dimensional confinement of nanosized TiO2 in carbon nanofibers, the TiO2/C nanofibers has a shortened Na+ diffusion path and the enhanced electronic conductivity, which greatly facilitate Na-insertion reaction. Meanwhile, the nanofiber morphology also offers abundant electrochemically active surface sites, enabling a high utilization of the TiO2 nanoparticles. As expected, The TiO2/C anode exhibits a high capacity of 302.4 mA h g-1 1 with excellent capacity retention of ~100% over 1000 cycles, offering a promising alternative anode for constructing low cost and high capacity Na-ion batteries.


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EXPERIMENTAL SECTION Materials synthesis. A single-nozzle electrospinning technique was employed to synthesize the TiO2/carbon nanofibers. The precursor solution for electrospinning process was prepared by dissolving 1.7 g tetrabutyl titanate (Ti(OC4H9)4, 97%, ) and 0.8 g polyvinylpyrrolidone (PVP, Mw =1,300,000, Aldrich) in 9.2 g ethanol (≥99.9% ) at vigorous stirring for 12 hours. Typically, 0.8 g polyvinylpyrrolidone (PVP, Mw =1,300,000, Aldrich) and 1.7 g tetrabutyl titanate (Ti(OC4H9)4, 97%, ) were dissolved in 9.2 g ethanol (≥99.9% ) at for 12 hours. Next, the precursor solution was loaded into a 10 mL syringe equipped with a size nine needle and the flow rate of solution was set to 8.5 mL h-1 by a syringe pump (Model LSP01-1A, Shanghai, China). A high voltage power supply (Model DW-N503-1A CDF, Tianjin, China) was connected to the needle in order to apply a voltage of 10 kV between the needle and the collecting aluminum plate for the formation of nanofibers. Heat-treatment of the as-collected nanofibers was carried out in a tube furnace at 550 ºC in Ar atmosphere for 3 h at a heating rate of 5 ºC min1

.) Structural characterizations. Scanning electron microscopy (SEM, ZEISS Merlin Compact)

and transmission electron microscopy (TEM, JEOL, JEM-2010-FEF) were employed to characterize the morphologies of the TiO2/C nanofibers. The crystalline structure of the TiO2/C nanofibers was evaluated by X-ray diffraction spectrometry (XRD) on a Shimadzu XRD-6000 machine. Thermogravimetric measurement (TGA) was conducted on a TGA Q500 thermogravimetric analyzer (TA Instruments, USA). The X-ray photoelectron spectrometry was used to identify the valence states of the TiO2/C electrodes cycled at different charge/discharge


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depths using a Thermo Scientific spectrometer (ESCLAB 250 Xi) equipped with an Al Kα achromatic X-ray source (1486.68 eV). Electrochemical measurements. To prepare the TiO2/C anode, 80 wt% TiO2/C nanofibers, 10 wt% super P, and 10 wt% polyacrylic acid (PAA, 25 wt %) were gently mixed to form a slurry, and then the slurry was coated onto a copper foil to form an anode film. After drying under vacuum at 80 ºC for 12 h, the anode film was cut into small disks with 1 cm diameter. The loading weight of the active material in the anode film was 1.5 mg cm-2. The CR2016-type half cells were assembled in a glove box filled with highly pure argon gas (O2 and H2O levels < 0.5 ppm) by sandwiching a glass-fiber separator (Whatman) between the anode film and a metallic sodium disk and then filling an electrolyte solution of 1 M NaClO4 in propylene carbonate (PC)/ ethylene carbonate (EC) (PC:EC = 1:1, in volume). Electrochemical performances of the TiO2/C anode were evaluated by galvanostatic charge/discharge on a LAND cycler (Wuhan Kingnuo Electronic Co., China) and cyclic voltammetry on a CHI 660c electrochemical workstation (ChenHua Instruments Co., China).)

RESULTS AND DISCUSSION The preparation process and synthetic chemistry of the TiO2/C nanofibers are schematically illustrated in Figure S1 (Supporting information, SI). In the electrospinning process, the precursor solution was extruded from the syringe needle under electrostatic drive to form the nanofiber precursor, which were converted into the TiO2/C composite nanofibers at subsequent heat treatment through the thermal carbonization of PVP polymer and simultaneous hydrolysis of Ti(OC4H9)4. Based on the weight losses in TGA measurement (Figure 1a), the total TiO2 content


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in the composite was determined to be 81%, which is in agreement with the expected value from complete carbonization and hydrolysis reactions of the precursor materials. The structural and morphological features of the TiO2/C nanofibers were examined by XRD, TGA, SEM and TEM spectrometry. As shown in Figure 1b, all the XRD peaks can be indexed to the (101), (200), (105)/(211) and (204) diffractions of a tetragonal phase, corresponding to anatase TiO2 (JCPDS No. 021-1272), space group I41/amd, a = 3.785 Å, and c = 9.514 Å). The weak intensities of the XRD signals were attributed to the nanosized TiO2 embedded in amorphous carbon matrix and no any diffraction was detected from other phases, suggesting the high purity of the as-synthesized TiO2 crystallites. N2 adsorption–desorption isotherms were measured todetermine the Brunauer-Emmett-Teller (BET) surface area and pore size distribution, as shown in Figure 1c,d. The BET surface area and the average pore width of TiO2/C nanofibers were determined to be 15.7 m2 g−1 and 14.7 nm, respectively.


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Figure 1. Physical characterizations of the TiO2/C nanofibers: (a). TGA curve; (b). XRD spectra; (c). N2 adsorption-desorption isotherm and (d) Pore size distribution Figure 2a-d shows the morphologies of the electrospun TiO2/C fibers after the thermal treatment. In the SEM images (Figure 2a, b), the sample appears as well-dispersed but mutually connected nanofibers with a uniformly distributed diameter of ~120 nm, forming a fibrous network. The surfaces of the nanofibers are very rough with densely distributed TiO2 nanoparticles, which may lead to high active surface areas for the Na-insertion reaction. The EDX element mapping image in Figure S2 indicates that both carbon and TiO2 are homogeneously distributed in the composite nanofibers. In the magnified TEM image (Figure 2c), it is clearly visualized that the TiO2 nanoparticles have an average size of ~12 nm and are dispersed throughout the carbon fibers. The lattice fringes in the high-resolution TEM image (Figure 2d) has a spacing of 0.35 nm, corresponding to the (101) planes of anatase TiO2. The amorphous regions around the lattice fringes reflect the disordered carbon phase.


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Figure 2. Morphological characterization of the TiO2/C nanofibers: (a) and (b). SEM images; (c). TEM image; and (d). High resolution TEM image. Na insertion performance of the TiO2/C anode were studied by cyclic voltammetry (CV) and galvanostatic charge-discharge measurements. As demonstrated in Figure 3a, a large and broad cathodic band appears at the potential region of 1.8 V to 0 V during first negative scan, which considerably decreases its intensity during subsequent cycles, suggesting that the formation of a solid electrolyte interface (SEI) by decomposition of electrolyte was involved in the initial sodiation reaction of the TiO2/C nanofibers. At subsequent scans, the pair of cathodic and anodic current bands kept their shapes and intensities almost unchanged, implying stable and reversible redox reactions of the material. Figure 3b shows galvanostatic charge/discharge profiles of the TiO2/C electrode, cycled at a constant current of 20 mA g−1 in the voltage interval of 3.0-0.01 V. Similar to its CV features, the TiO2/C electrode displays sloped charge/discharge profiles


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without distinct plateaus, suggesting a homogeneous Na insertion into the TiO2 lattice. The TiO2/C electrode shows initial charge/discharge capacities of 391/227.5 mA h g-1, corresponding to a coulombic efficiency of 58% at the first cycle. This low coulombic efficiency was also frequently encountered for the non-graphite Li+-insertion anodes due to the formation of a SEI film by the electrolyte decomposition and this problem can be well solved by a prelithiation technique for practical battery applications.44 During subsequent cycles, the reversible capacity remained stably at 212 mA h g-1, showing a remarkable cycling stability. Taking into account of the possible capacity contributions of the carbon components to the TiO2/C anode, we also measured the Na-storage capacities of the carbon fibers and conductive super P carbon powder and found that these carbons contributed only a few tens of milliampere hours (~31.5 mAh g-1) (Figure S3) in the total capacity. Nevertheless, the Na-insertion capacity of the TiO2 crystallites in the anode reached to 302.4 mA h g-1 at a moderate rate of 20 mA g-1, corresponding to 1 Na+ insertion into per TiO2 unit. This capacity is possibly the highest among the TiO2 materials for Na+-insertion anodes. The TiO2/C nanofibers also exhibit remarkable long-term cyclability and high-rate performance. As displayed in Figure 3c, the TiO2/C anode can deliver a high capacity of 240.4 mA h g-1 at a quite high current of 200 mA g-1 after a few cycles of initial activation and then keep this capacity almost constant at 237.1 mA h g-1 over 1000 cycles, suggesting a very reversible Na+ insertion reaction in the structurally stable TiO2 lattice. To provide further evidence for the structural stability of the TiO2/C nanofibers, SEM and TEM images of the TiO2/C nanofibers were taken from the cycled electrode, as shown in Figure S4. It can be seen from Figure S4 that the fibrous morphology of the TiO2/C nanofibers remains intact after 150


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and 200 cycles and is still distinguishable even after 1000 cycles, indicating a strong tolerance of the material to the volumetric change during Na+-insertion/extraction cycles. The rate performances of the TiO2/C nanofibers are further evaluated at various chargedischarge rates from 50 mA g-1 to 2000 mA g-1. As shown in Figure 3d, the reversible capacity is slightly decreased from 254.5 mA h g-1 to 241.3, 227.7 and 203.8 mA h g-1 with increasing current rates from 50 mA g-1 to100, 200 and 500 mA g-1, respectively. Even when the current rate was raised up to very high rates of 1000 and 2000 mA g-1, this anode can still remain 185.3 and 164.9 mA h g-1, respectively, indicating a rapid reaction process for Na+- insertion process. This superior rate performance is apparently ascribed to the nanoarchitectural design of the TiO2/C composite, where the well-dispersed TiO2 nanoparticles provide abundant active sites for Na+-insertion and meanwhile their surrounding carbon matrix offers high electric conduction paths for fast electron transport.


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Figure 3. Electrochemical behaviors of the TiO2/C nanofiber anode: (a). CV curves scanned at 0.1 mV s-1; (b). Charge/discharge profiles measured at a constant current of 20 mA g-1; (c). Cycling performance at a constant current of 200 mA g-1; and (d). Rate capability at changing current rates from 50 mA g-1 to 2000 mA g-1. To confirm the Na-insertion mechanism, we disassembled the test cells and characterized the structural changes of the TiO2/C anodes cycled at different states of charge/discharge by ex-situ XRD technique. Figure 4a shows the XRD patterns of the TiO2/C anodes charged and discharged at different depths. During the discharge process, all the XRD peaks kept their positions and decreased their intensities with increasing the depth of discharge, as expected from a Nainsertion reaction. When fully discharged to 0.01 V, the whole XRD pattern became indistinct, representing an amorphous state of the sodiated TiO2. This progressive amorphourization reaction is obviously brought about by the insertion of Na+ ion into the TiO2 lattice during discharge, which leads to a decrease of the lattice symmetry of the material. Once reversely charged to 3V (Figure 4 a), the XRD peaks reemerged at their original positions with a slightly weakened

intensities,

demonstrating

a

highly

reversible

structural

change

during

charge/discharge reactions. Since no traceable XRD signals from Ti0 and Na2O phases could be detected, the charge/discharge mechanism of the TiO2 nanofibers can only be assigned to Na+insertion/extraction reactions. To further confirm this reaction mechanism, the changes in the oxidation state of Ti element were calibrated by XPS analysis of the cycled TiO2/C anodes. As shown in Figure 4 b, the pristine TiO2/C anode shows two XPS peaks at 458.9 eV and 464.6 eV, corresponding to the binding energies of Ti+4 2p 3/2 and Ti+4 2p 1/2, respectively. When discharged to 0.01 V, these binding energies negatively shifted to 457.8 eV and 463.4 eV, respectively, suggesting that all the Ti+4 ions in the TiO2 lattice were reduced to Ti+3 ions. After a


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reversed charge to 3.0 V, the binding energies recovered to their original values, indicating a reversible conversion of Ti+3 into Ti+4 ions in the TiO2 lattice. This XPS evidence combining with XRD analysis reveal a completely chemical and structural reversibility of the Na+-insertion reaction in the TiO2 host.

Figure 4. (a) Left: A typical charge/discharge profile of the TiO2-nanofiber anode, on which arabic characters denote the sampling potential, right: XRD patterns of the TiO2 nanofiber anode at different charge/discharge depths; (b) Ti 2p spectra of the TiO2 nanofiber anode at a. open circuit and d. discharged to 0.01V and g. recharged to 3V. To test its practical feasibility for battery applications, we assembled a full Na-ion battery using the TiO2/C anode coupled with a Na-rich Na2FeFe(CN)6 cathode. The construction and electrochemical performance of the TiO2/Na2FeFe(CN)6 full cell are described in Supporting information (Figure S5). As expected from the potential difference between the TiO2 and Na2FeFe(CN)6 couple, this full Na-ion battery give an open circuit voltage of 3.2 V and an average discharge voltage of ＞2.0 V. Derived from the charge/discharge curves of the full cells, the TiO2/C anode can deliver a discharge capacity of 235.9 mA h g-1, fully utilizing its reversible capacity in a practical Na-ion battery.


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CONCLUSIONS In summary, anatase TiO2/C nanofibers were successfully synthesized by a single-nozzle electrospinning method followed with subsequent heat treatment. Benefiting from a combination of the large active surfaces of well-dispersed TiO2 nanocrytals and the high electronic conductivity of the carbon fibers, the TiO2/C nanofiber electrode demonstrated a high reversible capacity of ~302.4 mA h g-1 and a strong rate capability with 164.9 mA h g-1 at a very high current of 2000 mA g-1. Particularly because of being dispersively embedded in the carbon matrix, the TiO2 nanocrystals were prevented from aggregating and attacking by electrolyte, therefore exhibiting a remarkably long-term cycling stability with nearly 100% capacity retention over 1000 cycles. Such superior electrochemical performances described above make the TiO2/C nanofibers a promising anode material for constructing low cost and high capacity Na-ion batteries.

ASSOCIATED CONTENT Supporting Information. Schematic illustration of the preparation process for the TiO2/C nanofibers, EDX element mapping characterization of the TiO2/C nanofibers, Na-storage capacities of the carbon fibers and conductive super P carbon powder, morphological characterization of the TiO2/C nanofibers after cycling and charge/discharge performance of the TiO2/Na2FeFe(CN)6 full cell were included in supporting information. This material is available free of charge via the Internet at http://pubs.acs.org/. AUTHOR INFORMATION Corresponding Author


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* E-mail: [email protected]. Tel: 86-027-68754526. Notes The authors declare no competing financial interest. ACKNOWLEDGMENTS The authors appreciate the financial support for this work by National Science Foundation of China (No. 21333007) and the 973 project of China (No. 2015CB251100).

REFERENCES (1). Yang, Z.; Zhang, J.; Kintner-Meyer, M. C. W.; Lu, X.; Choi, D.; Lemmon, J. P.; Liu, J., Electrochemical Energy Storage for Green Grid. Chem. Rev. 2011, 111, 3577-3613. (2). Pan, H.; Hu, Y.-S.; Chen, L., Room-Temperature Stationary Sodium-Ion Batteries for Large-Scale Electric Energy Storage. Energy Environ. Sci. 2013, 6, 2338-2360. (3). Palomares, V.; Serras, P.; Villaluenga, I.; Hueso, K. B.; Carretero-Gonzalez, J.; Rojo, T., Na-Ion Batteries, Recent Advances and Present Challenges to Become Low Cost Energy Storage Systems. Energy Environ. Sci. 2012, 5, 5884-5901. (4). 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. (5). Fang, C.; Huang, Y.; Zhang, W.; Han, J.; Deng, Z.; Cao, Y.; Yang, H., Routes to High Energy Cathodes of Sodium-Ion Batteries. Adv. Energy Mater. 2016, 6, 1507127.


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Page 15 of 21

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(6). Wang, Y.; Xiao, R.; Hu, Y.-S.; Avdeev, M.; Chen, L., P2-Na0.6Cr0.6Ti0.4O2 CationDisordered Electrode for High-Rate Symmetric Rechargeable Sodium-Ion Batteries. Nat. Commun. 2015, 6, 6954. (7). Talaie, E.; Duffort, V.; Smith, H. L.; Fultz, B.; Nazar, L. F., Structure of The High Voltage Phase of Layered P2-Na2/3-z[Mn1/2Fe1/2]O2 and The Positive Effect of Ni Substitution on Its Stability. Energy Environ. Sci. 2015, 8, 2512-2523. (8). Yuan, D.; Liang, X.; Wu, L.; Cao, Y.; Ai, X.; Feng, J.; Yang, H., A Honeycomb-Layered Na3Ni2SbO6: A High-Rate and Cycle-Stable Cathode for Sodium-Ion Batteries. Adv. Mater. 2014, 26, 6301-6306. (9). Fang, Y.; Xiao, L.; Ai, X.; Cao, Y.; Yang, H., 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. (10). Wood, S. M.; Eames, C.; Kendrick, E.; Islam, M. S., Sodium Ion Diffusion and Voltage Trends in Phosphates Na4M3(PO4)2P2O7 (M = Fe, Mn, Co, Ni) for Possible High-Rate Cathodes. J. Phys. Chem. C 2015, 119, 15935-15941. (11). Zhao, J.; Mu, L.; Qi, Y.; Hu, Y.-S.; Liu, H.; Dai, S., A Phase-Transfer Assisted SolvoThermal Strategy for Low-Temperature Synthesis of Na3(VO1-xPO4)2F1+2x Cathodes for SodiumIon Batteries. Chem. Commun. 2015, 51, 7160-7163. (12). Wu, X.; Deng, W.; Qian, J.; Cao, Y.; Ai, X.; Yang, H., Single-Crystal FeFe(CN)6 Nanoparticles: A High Capacity and High Rate Cathode for Na-Ion Batteries. J. Mater. Chem. A 2013, 1, 10130-10134.


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Page 16 of 21

(13). Xiao, L.; Cao, Y.; Henderson, W. A.; Sushko, M. L.; Shao, Y.; Xiao, J.; Wang, W.; Engelhard, M. H.; Nie, Z.; Liu, J., Hard Carbon Nanoparticles as High-Capacity, High-Stability Anodic Materials for Na-Ion Batteries. Nano Energy 2016, 19, 279-288. (14). Xu, Y.; Zhu, Y.; Liu, Y.; Wang, C., Electrochemical Performance of Porous Carbon/Tin Composite Anodes for Sodium-Ion and Lithium-Ion Batteries. Adv. Energy Mater. 2013, 3, 128133. (15). Xie, X.; Kretschmer, K.; Zhang, J.; Sun, B.; Su, D.; Wang, G., Sn@CNT Nanopillars Grown Perpendicularly on Carbon Paper: A Novel Free-Standing Anode for Sodium Ion Batteries. Nano Energy 2015, 13, 208-217. (16). Wu, L.; Hu, X.; Qian, J.; Pei, F.; Wu, F.; Mao, R.; Ai, X.; Yang, H.; Cao, Y., Sb-C Nanofibers with Long Cycle Life as An Anode Material for High-Performance Sodium-Ion Batteries. Energy Environ. Sci. 2014, 7, 323-328. (17). Wu, L.; Lu, H.; Xiao, L.; Ai, X.; Yang, H.; Cao, Y., Improved Sodium-Storage Performance of Stannous Sulfide@Reduced Graphene Oxide Composite as High Capacity Anodes for Sodium-Ion Batteries. J. Power Sources 2015, 293, 784-789. (18). Qian, J.; Wu, X.; Cao, Y.; Ai, X.; Yang, H., High Capacity and Rate Capability of Amorphous Phosphorus for Sodium Ion Batteries. Angew. Chem., Int. Ed. 2013, 52, 4633-4636. (19). Qian, J.; Xiong, Y.; Cao, Y.; Ai, X.; Yang, H., Synergistic Na-Storage Reactions in Sn4P3 as a High-Capacity, Cycle-stable Anode of Na-Ion Batteries. Nano Lett. 2014, 14, 1865-1869.


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(20). Liu, X.; Du, Y.; Xu, X.; Zhou, X.; Dai, Z.; Bao, J., Enhancing the Anode Performance of Antimony through Nitrogen-Doped Carbon and Carbon Nanotubes. J. Phys. Chem. C 2016, 120, 3214-3220. (21). Zhou, X.; Dai, Z.; Liu, S.; Bao, J.; Guo, Y.-G., Ultra-Uniform SnOx/Carbon Nanohybrids toward Advanced Lithium-Ion Battery Anodes. Adv. Mater. 2014, 26, 3943-3949. (22). Cao, F.-F.; Guo, Y.-G.; Zheng, S.-F.; Wu, X.-L.; Jiang, L.-Y.; Bi, R.-R.; Wan, L.-J.; Maier, J., Symbiotic Coaxial Nanocables: Facile Synthesis and an Efficient and Elegant Morphological Solution to the Lithium Storage Problem. Chem. Mater. 2010, 22, 1908-1914. (23). Cao, F.-F.; Wu, X.-L.; Xin, S.; Guo, Y.-G.; Wan, L.-J., Facile Synthesis of Mesoporous TiO2−C Nanosphere as an Improved Anode Material for Superior High Rate 1.5 V Rechargeable Li Ion Batteries Containing LiFePO4-C Cathode. J. Phys. Chem. C 2010, 114, 10308-10313. (24). Ding, C.; Nohira, T.; Hagiwara, R., A High-Capacity TiO2/C Negative Electrode for Sodium Secondary Batteries with an Ionic Liquid Electrolyte. J. Mater. Chem. A 2015, 3, 2076720771. (25). Xiong, H.; Slater, M. D.; Balasubramanian, M.; Johnson, C. S.; Rajh, T., Amorphous TiO2 Nanotube Anode for Rechargeable Sodium Ion Batteries. J. Phys. Chem. Lett. 2011, 2, 2560-2565. (26). Bi, Z.; Paranthaman, M. P.; Menchhofer, P. A.; Dehoff, R. R.; Bridges, C. A.; Chi, M.; Guo, B.; Sun, X.-G.; Dai, S., Self-Organized Amorphous TiO2 Nanotube Arrays on Porous Ti Foam for Rechargeable Lithium and Sodium Ion Batteries. J. Power Sources 2013, 222, 461466.


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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 21

(27). 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. (28). Wu, L.; Buchholz, D.; Bresser, D.; Gomes Chagas, L.; Passerini, S., Anatase TiO2 Nanoparticles for High Power Sodium-Ion Anodes. J. Power Sources 2014, 251, 379-385. (29). Yang, X.; Wang, C.; Yang, Y.; Zhang, Y.; Jia, X.; Chen, J.; Ji, X., Anatase TiO2 Nanocubes for Fast and Durable Sodium Ion Battery Anodes. J. Mater. Chem. A 2015, 3, 88008807. (30). Zhang, Y.; Pu, X.; Yang, Y.; Zhu, Y.; Hou, H.; Jing, M.; Yang, X.; Chen, J.; Ji, X., An Electrochemical Investigation of Rutile TiO2 Microspheres Anchored by Nanoneedle Clusters for Sodium Storage. Phys. Chem. Chem. Phys. 2015, 17, 15764-15770. (31). Hong, Z.; Zhou, K.; Zhang, J.; Huang, Z.; Wei, M., Facile Synthesis of Rutile TiO2 Mesocrystals with Enhanced Sodium Storage Properties. J. Mater. Chem. A 2015, 3, 1741217416. (32). Sondergaard, M.; Dalgaard, K. J.; Bojesen, E. D.; Wonsyld, K.; Dahl, S.; Iversen, B. B., In Situ Monitoring of TiO2(B)/Anatase Nanoparticle Formation and Application in Li-Ion and Na-Ion Batteries. J. Mater. Chem. A 2015, 3, 18667-18674. (33). Huang, J. P.; Yuan, D. D.; Zhang, H. Z.; Cao, Y. L.; Li, G. R.; Yang, H. X.; Gao, X. P., Electrochemical Sodium Storage of TiO2(B) Nanotubes for Sodium Ion Batteries. RSC Adv. 2013, 3, 12593-12597.


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Page 19 of 21

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


(34). Perez-Flores, J. C.; Baehtz, C.; Kuhn, A.; Garcia-Alvarado, F., Hollandite-Type TiO2: A New Negative Electrode Material for Sodium-Ion Batteries. J. Mater. Chem. A 2014, 2, 18251833. (35). Su, D.; Dou, S.; Wang, G., Anatase TiO2: Better Anode Material Than Amorphous and Rutile Phases of TiO2 for Na-Ion Batteries. Chem. Mater. 2015, 27, 6022-6029. (36). 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. (37). Lee, J.; Chen, Y.-M.; Zhu, Y.; Vogt, B. D., Fabrication of Porous Carbon/TiO2 Composites through Polymerization-Induced Phase Separation and Use As an Anode for Na-Ion Batteries. ACS Appl. Mater. Interfaces 2014, 6, 21011-21018. (38). Zhang, Y.; Yang, Y.; Hou, H.; Yang, X.; Chen, J.; Jing, M.; Jia, X.; Ji, X., Enhanced Sodium Storage Behavior of Carbon Coated Anatase TiO2 Hollow Spheres. J. Mater. Chem. A 2015, 3, 18944-18952. (39). Chen, C.; Wen, Y.; Hu, X.; Ji, X.; Yan, M.; Mai, L.; Hu, P.; Shan, B.; Huang, Y., Na+ Intercalation Pseudocapacitance in Graphene-Coupled Titanium Oxide Enabling Ultra-Fast Sodium Storage and Long-Term Cycling. Nat. Commun. 2015, 6, 6929. (40). 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.


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(41). Ge, Y.; Zhu, J.; Lu, Y.; Chen, C.; Qiu, Y.; Zhang, X., The Study on Structure and Electrochemical Sodiation of One-Dimensional Nanocrystalline TiO2@C Nanofiber Composites. Electrochim. Acta 2015, 176, 989-996. (42). Yeo, Y.; Jung, J.-W.; Park, K.; Kim, I.-D., Graphene-Wrapped Anatase TiO2 Nanofibers as High-Rate and Long-Cycle-Life Anode Material for Sodium Ion Batteries. Sci. Rep. 2015, 5, 13862. (43). 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. (44). Zhao, J.; Lu, Z.; Wang, H.; Liu, W.; Lee, H.-W.; Yan, K.; Zhuo, D.; Lin, D.; Liu, N.; Cui, Y., Artificial Solid Electrolyte Interphase-Protected LixSi Nanoparticles: An Efficient and Stable Prelithiation Reagent for Lithium-Ion Batteries. J. Am. Chem. Soc. 2015, 137, 8372-8375.


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Table of Contents Graphic 260x102mm (150 x 150 DPI)


C Nanofibers As a High-Capacity and Cycle-Stable

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