High-Performance Silicon Battery Anodes Enabled by Engineering

Aug 25, 2015 - Robust Micron-Sized Silicon Secondary Particles Anchored by ...... Dai-Huo Liu , Hong-Yan Lü , Xing-Long Wu , Jie Wang , Xin Yan , Jin...
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Letter pubs.acs.org/NanoLett

High-Performance Silicon Battery Anodes Enabled by Engineering Graphene Assemblies Min Zhou,†,‡ Xianglong Li,*,† Bin Wang,† Yunbo Zhang,† Jing Ning,† Zhichang Xiao,† Xinghao Zhang,† Yanhong Chang,‡ and Linjie Zhi† †

CAS Key Laboratory of Nanosystem and Hierarchical Fabrication, National Center for Nanoscience and Technology, Beijing 100190, China ‡ Department of Environmental Engineering, University of Science and Technology of Beijing, Beijing 100083, China

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S Supporting Information *

ABSTRACT: We propose a novel material/electrode design formula and develop an engineered self-supporting electrode configuration, namely, silicon nanoparticle impregnated assemblies of templated carbon-bridged oriented graphene. We have demonstrated their use as binder-free lithium-ion battery anodes with exceptional lithium storage performances, simultaneously attaining high gravimetric capacity (1390 mAh g−1 at 2 A g−1 with respect to the total electrode weight), high volumetric capacity (1807 mAh cm−3 that is more than three times that of graphite anodes), remarkable rate capability (900 mAh g−1 at 8 A g−1), excellent cyclic stability (0.025% decay per cycle over 200 cycles), and competing areal capacity (as high as 4 and 6 mAh cm−2 at 15 and 3 mA cm−2, respectively). Such combined level of performance is attributed to the templated carbon bridged oriented graphene assemblies involved. This engineered graphene bulk assemblies not only create a robust bicontinuous network for rapid transport of both electrons and lithium ions throughout the electrode even at high material mass loading but also allow achieving a substantially high material tap density (1.3 g cm−3). Coupled with a simple and flexible fabrication protocol as well as practically scalable raw materials (e.g., silicon nanoparticles and graphene oxide), the material/electrode design developed would propagate new and viable battery material/electrode design principles and opportunities for energy storage systems with high-energy and high-power characteristics. KEYWORDS: graphene, assembly, self-supporting, silicon anode, lithium-ion battery

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remains an unmet goal to harness the potential of silicon in LIB anodes, specifically in terms of gravimetric capacity, volumetric capacity, areal capacity, rate capability, and cyclic stability at the same time. Graphene, a single-layer carbon sheet with a hexagonal packed lattice structure, has been touted to be a remarkable carbonaceous structural platform to afford the exertion of various functional nanostructured materials, on account of its unique two-dimensional structure, excellent electronic conductivity, superior mechanical flexibility, good chemical stability, and high theoretical surface area.20−26 To date, numerous novel approaches have been explored to utilize graphene to address the challenges of silicon anodes and, thus, to improve their lithium storage capabilities. Most of them are based on the hybridization of graphene sheets and nanostructured silicon of different dimensionalities at the materials unit scale.27−36 However, the thus-resulted hybrids always

here is an ever increasing demand for making lithium-ion batteries (LIBs) with larger gravimetric (specific) and volumetric capacities, higher power density, and longer cycle life for various technological applications, including portable electronics, electric vehicles, and renewable energy integration.1−3 Silicon (Si) is believed to be a promising candidate anode material for future LIBs on account of its high theoretical capacity (3579 mAh g−1 for Li15Si4) and relatively low working potential.4−8 Yet, the Si anodes suffer from rapid decay of capacity upon cycling; this can be attributed to the structural degradation, loss of electrical contact, and the unstable solid electrolyte interphase (SEI) on the silicon surface caused by the dramatic volume change of Si (∼300%) during lithiationdelithiation cycling.4,8 To address these issues, one popular and effective tactic is to couple nanostructured silicon with a second phase (e.g., carbon).9−19 The core of this strategy is fundamentally to create effective and robust three-dimensional transport networks for both electrons and lithium ions. As the exciting materials formulations and electrode prototypes developed based upon elaborately designed carbonaceous matrices have contributed to significant improvements in some properties of silicon anodes at low mass loadings, it © XXXX American Chemical Society

Received: July 8, 2015 Revised: August 18, 2015

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Figure 1. Electrode design and fabrication. (a) Schematic of the configuration of silicon nanoparticle-impregnated assemblies of templated carbon bridged oriented graphene (TCG-Si). (b) Schematic illustration showing the structure of TCG obtained by removing the Si template from the TCGSi. (c) Schematic illustration of the fabrication process for TCG-Si, where bovine serum albumin (BSA)-coated silicon nanoparticles and graphene oxide (GO) are assembled via electrostatic interactions during vacuum filtration, thus enabling the successful fabrication of TCG-Si.

active materials and consequently unacceptable volumetric energy density, which fatally hinders their deployment in viable LIBs.7,8,11−13,50−52 Therefore, it is highly desirable to exploit new material/electrode design principles to combine graphene and silicon, so as to overcome the above-mentioned challenges of silicon anodes. We believe that the similar circumstances hold as well for building the systems of graphene and other electrode materials encountering large volume changes. In this report, we propose a novel material/electrode design formula, and develop an engineered self-supporting electrode configuration where, graphene sheets (G) are oriented and bridged by silicon nanoparticle-templated carbon (TC) hinges, thus forming silicon nanoparticle-impregnated assemblies of templated carbon bridged oriented graphene (denoted as TCGSi) (Figure 1a). In the designed TCG-Si, the templated carbon bridged oriented graphene assemblies (TCG) involved form a robust bicontinuous network to facilitate the electron and lithium ion transport throughout the electrode even at high areal mass loadings (Figure 1b); meanwhile, the TCG assemblies feature the compact characteristic allowing for achievement of a substantially high tap density of Si impregnated. As a result, the TCG-Si exhibits exceptional lithium storage performance when being used directly as the LIB electrode, attaining high gravimetric capacity (1390 mAh g−1 at 2 A g−1 with respect to the total electrode weight), high volumetric capacity (1807 mAh cm−3 which is more than three times that of graphite anodes), superior rate capability (900 mAh g−1 at 8 A g−1), excellent cyclic stability (0.025% decay per cycle over 200 cycles), and competing areal capacity (up to 4 and 6 mAh cm−2 at 15 and 3 mA cm−2, respectively) that approaches the level of commercial lithium-ion batteries. We note that a Si anode with this combined level of performance

require additional components (e.g., binders and conductive additives) that are required in constructing a conventional electrode. The substantial need of such extra substances not only adversely affects the designated electrochemical properties of the hybrids but also unfavorably dilutes the electrode performance including both volumetric capacity and gravimetric capacity, as the total weight and volume of the electrode must be counted from a practical viewpoint.37 The electrodescale construction of self-supporting binder-free hybrid films/ membranes of aligned graphene sheets and nanostructured silicon, for example, via vacuum filtration, has been demonstrated to be a very attractive approach to propel the direct utilization of such hybridized nanomaterials as highpacking-density LIB electrodes, as well as to enable the exertion and performance enhancement of silicon embedded.38−42 However, the restacking of edge portions of aligned graphene sheets generally results in the creation of an electrode-scale continuum featuring poor cross-plane lithium-ion diffusivity, thus restricting performance enhancement of the hybrid films/ membranes especially at high charge/discharge rates. This situation can be alleviated by employing graphene sheets with a great deal of nanoscale in-plane carbon vacancies,43 but it recurs due to limited penetration of the electrolyte into the electrode interior as the areal material mass loading and also the electrode thickness increase with respect to practical applications.8,18,44 The integration of nanostructured silicon into macroscopic randomly structured graphene foams45 has been developed to confer rapid and robust transport pathways for both electrons and lithium ions throughout the whole electrode, representing a promising way to improve the performance of silicon anodes.46−49 Unfortunately, these porous hybrid foams suffer from new challenges such as low tap (packing) density of the B

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are indeed interconnected through their neighboring silicon nanoparticle-containing TC hinges (TC-Si). This scenario is significantly different from that of the G-Si control sample prepared by vacuum filtration of a simple mixture of GO and silicon nanoparticles (Supporting Information Figure S1; see details in Experimental Section). In the latter, graphene sheets constitute completely continuous interlayers sandwiching silicon nanoparticles due to the intersheet stacking of oriented graphene sheets during vacuum filtration, which resembles the morphologies of other graphene-based self-supporting membranes fabricated via vacuum filtration.41−43 It can be presumed that this intersheet stacking has been effectively screened by the assembled TC-Si in the case of TCG-Si, because BSA-coated silicon nanoparticles prefer to settle at the functional group sites existing both on the surface and at the periphery of GO sheets upon electrostatic interaction. After removing the impregnated silicon nanoparticles from TCG-Si by sodium hydroxide (NaOH), the resultant TCG assemblies remain selfsupporting and the involved graphene sheets maintain their originally oriented morphology (Figure 2d and e), reflecting the interconnecting nature of segregated oriented graphene sheets. The high magnification SEM image further reveals that the TC hinges possess an interlinked shell-like structure (Figure 2f), for which the difference observed can result from the various aggregation states of silicon nanoparticles acting as the template. The TEM images of TCG-Si (Figure 3a and b) show that individual silicon nanoparticles (average diameter: 100 nm) as well as their small aggregates are homogeneously anchored on graphene sheets. The high-resolution TEM image (Figure 3c) further discloses that the anchored silicon nanoparticles are fastened on graphene via a layer of 3−5 nm thick carbon that indeed constitutes the TC hinges bridging graphene sheets. Moreover, the few-layer characteristic of graphene sheets can be distinguished, as well as the crystalline structure of silicon nanoparticles can be identified, which reveals the structural conservation of silicon nanoparticles upon our thermal annealing processing. In agreement with the above TEM results, the XRD pattern of TCG-Si displays typical peaks of crystalline silicon, confirming the structural preservation of silicon nanoparticles in the TCG-Si (Supporting Information Figure S2). This is also the case for the G-Si control sample. In addition, the N 1s peak can be observed in the XPS spectrum of TCG-Si (Supporting Information Figure S3), indicating the existence of nitrogen; the high-resolution N 1s XPS spectrum (Figure 3e) depicts that three distinct N configurations coexist, including pyridinic N (∼398.4 eV), pyrrolic N (∼400.2 eV), and quaternary N (∼401.1 eV). This is probably favorable for the electrochemical performance, because the nitrogen doping has been demonstrated to greatly enhance the electronic conductivity as well as charge transfer at the interface.55 Notably, the nitrogen originates from the BSA precursor on silicon nanoparticles; that is, the composition and structure of the resultant TC hinges may be tailored for different applications, for example, by employing diverse proteins or other positively charged polymers as the precursor. The elemental mapping images (Figure 3d) further indicate the homogeneous distribution of carbon and nitrogen in the coating layer (that is, TC) on silicon nanoparticles as the template. Figure 3f depicts the Raman spectra of TCG-Si and G-Si. The peak appeared at ca. 520 cm−1 can be assignable as the characteristic band of crystalline silicon in both cases, consistent with the above TEM and XRD results. Besides, two

has rarely been described. This study expands the potential of graphene in improving silicon anode performances and will propagate new and viable battery material/electrode design formulas and opportunities for energy storage systems with high-energy and high-power characteristics. The fabrication of TCG-Si mainly involves a modified vacuum filtration process followed by thermal annealing, during which bovine serum albumin (BSA)-coated silicon nanoparticles and graphene oxide (GO) sheets are assembled via electrostatic interactions (Figure 1c; see Methods in Supporting Information). As most reported nanostructured silicon-based anodes inevitably require either extremely hazardous silicon precursors or complex and costly procedures for the synthesis of structured silicon, in this work, we directly used commercial silicon nanoparticles, which have been studied as a scalable candidate anode material. Besides, graphene oxide sheets were synthesized based on the literature,42 which is a reliable and scalable precursor of graphene. Under acidic conditions, BSAcoated silicon nanoparticles are positively charged,53 whereas graphene oxide sheets are negatively charged. In view of this scenario, electrostatic assembly between BSA-coated silicon nanoparticles and GO sheets has been successfully conducted during the vacuum filtration process toward the fabrication of TCG-Si assemblies. As exhibited in Figure 1c, the resultant TCG-Si assemblies are mechanically robust and free-standing. This characteristic enables their direct use as LIB electrodes without introducing any supplementary components. The morphology and structure of TCG-Si assemblies were characterized by means of transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and Raman spectroscopy. Figure 2a exhibits the typical SEM image of 14 μm thick TCG-Si assemblies, indicating its self-supporting nature and the thickness uniformity. As shown in Figure 2b and c, the graphene sheets are oriented upon a directional flow during filtration;54 surprisingly, they are segregated from each other. Notably, the high magnification SEM image (Figure 2c) further reveals that these segregated oriented graphene sheets

Figure 2. The morphology of TCG-Si. (a−c) SEM images at different magnifications of TCG-Si. (d−f) SEM images at different magnifications of TCG obtained by removing the silicon from the TCG-Si. C

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Figure 3. The structure of TCG-Si. (a,b) TEM images of TCG-Si. (c) High-resolution TEM image of TCG-Si. (d) Elemental mapping images of TCG-Si. (e) High-resolution N 1s XPS spectrum of TCG-Si. (f) Raman spectra of TCG-Si and G-Si.

Figure 4. Electrochemical characteristics. (a) Gravimetric capacity and Coulombic efficiency of the TCG-Si and control electrodes (G-Si, SiNP). The current rate is 0.2 A g−1 for the first cycle and 2 A g−1 for later cycles; all the gravimetric capacities reported are on the basis of the total electrode weight. (b) Volumetric capacity achievable at the annotated current rates and cycles for the TCG-Si and G-Si electrodes comparing with some representative Si anodes reported in the literatures as noted. Their respective gravimetric capacity based on the total electrode weight is superimposed with gray columns as well. (c) Rate capabilities for the TCG-Si electrodes of different thicknesses (6−28 μm), as well as a 5 μm thick G-Si electrode. (d) Areal capacities of the TCG-Si electrodes with different areal mass loadings (0.8−3.7 mg cm−2), where the annotated current rates are used for testing.

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materials.8,56 Furthermore, the observed variation in the firstcycle Coulombic efficiency for the TCG-Si electrode and the GSi electrode (72% and 62%, respectively) may be associated with the difference in the carbon component of the electrodes, although the detailed origin needs to be further investigated. The volumetric capacity is a critical parameter dominating the deployment of Si anodes, which strongly depends on the gravimetric capacity achieved and the packing density of the material. For our TCG-Si electrodes, the unique electrode configuration affords high gravimetric capacities with regard to the total electrode weight, as well as high packing density of materials up to ∼1.3 g cm−3, a distinct characteristic of the graphene bulk prepared by filtration.54 As depicted in Figure 4b, the volumetric capacity of the TCG-Si electrode is quite remarkable; specifically, the TCG-Si electrode delivers a high volumetric capacity of 1807 mAh cm−3 after 200 cycles, which is more than three times that (440−600 mAh cm−3) of commercialized graphite anodes.56 Remarkably, the volumetric capacity and capacity retention of the TCG-Si electrodes achieved are among or even surpass the best of the reported Si anodes.7,8,11,15,17,19,37,46,56 To the contrary, the quite low volumetric capacity (280 mAh cm−3) of the G-Si control electrode is obtained after 200 cycles. This can be mainly due to continuous fading of the gravimetric capacity of the G-Si electrode. Besides, the TCG-Si electrodes demonstrate superior rate capability (Figure 4c; Supporting Information Figure S9). As an example, at a rate of 8 A g−1, the 6 μm thick TCG-Si electrode exhibits a reversible capacity of 900 mAh g−1 with respect to the total electrode weight, which is comparable to, if not higher than, the capacity of other reported high-power-characteristic silicon anodes.36,43 For the same current rate, the G-Si control electrode with a comparable thickness (5 μm) only shows a reversible capacity of around 350 mAh g−1. The poor rate capability of the G-Si electrode is associated with the relatively poor electrical conductivity (Supporting Information Figure S10), as well as the extremely high width-to-thickness aspect ratio of graphene sheets and their intersheet stacking, which are rather unfavorable for ion transport as discussed elsewhere.42,43 By contrast, the superior rate capability of the TCG-Si electrode can be attributable to their designed configuration, in which the TCG assemblies function as a robust uninterrupted three-dimensional network to facilitate the electron and lithium ion transport across the whole electrode, thus enabling the functioning of silicon impregnated even at high current rates. More interestingly, such high rate capability of the TCG-Si electrodes can be almost constantly achieved as the electrode thickens up to 28 μm. This distinct character is further verified by the electrochemical impedance spectroscopy spectra (Supporting Information Figure S10) showing that charge-transfer characteristics are less dependent on the thickness of the TCG-Si electrodes. Moreover, even after cycling at high charge/discharge rates, the capacities for all the TCG-Si electrodes of different thicknesses can be recovered as verified by the case at 2 A g−1, further indicating the reversibility of storage capacity. From the practical viewpoint, it is generally recognized that areal mass loading is highly required for high-performance electrodes. On the basis of the flexibility of our TCG-Si fabrication process in increasing electrode thickness (up to 28 μm) and thus areal mass loading, we then tested the TCG-Si electrodes, in which the material areal mass loading is up to 3.7 mg cm−2 (Figure 4d). When being cycled at a rate of 0.8 A g−1

predominant peaks appear at approximately 1350 and 1594 cm−1, which can be assigned to the D band deriving from disordered carbon, and G band originating from sp2 hybridized carbon, respectively. Both bands come from graphene in the case of G-Si; for the TCG-Si, they can originate from both TC and graphene. The intensity ratio (0.91) of D band to G band (ID/IG) for the TCG-Si is relatively higher than that (0.74) for the G-Si, which is primarily associated with the defects or disordered structures of nitrogen-containing TC in the TCG-Si. Unless otherwise noted, the silicon content in the TCG-Si is adjusted to be around 62 wt % as confirmed by thermogravimetric analysis (TGA) (Supporting Information Figure S4). To investigate the electrochemical properties of the TCG-Si electrodes and also the control electrodes, coin-type cells (CR2032) were fabricated by using lithium foil as the counter electrodes. As shown in Figure 4a, the reversible capacity of the TCG-Si electrode reaches 2170 mAh g−1 at a rate of 0.2 A g−1. If not specified, all reported capacity values here are on the basis of the total electrode weight. Considering the silicon content of 62 wt %, the capacity relative to silicon alone is up to 3500 mAh g−1, nearly approaching the theoretical value of silicon. Such a substantially high capacity value reflects high accessibility of the impregnated silicon for the reaction with Li in the designed assemblies. From the 2nd to 200th cycle at 2 A g−1, the capacity retention is as high as 95%. The capacity remains to be approximately 1390 mAh g−1 after 200 cycles, which is almost four times the theoretical value of graphite. It is noteworthy that the achieved capacities can mainly originate from the Si in the TCG-Si since the low content (38 wt %) of TCG and its low capacity (75 mAh g−1 at 2 A g−1) under the same testing conditions (Supporting Information Figure S5). This scenario is also consistent with the voltage profiles and the cyclic voltammetry (CV) results for the TCG-Si electrode (Supporting Information Figure S6, Figure S7). The achieved cyclic stability (0.025% decay per cycle) is outstanding as compared with that of existing silicon anodes with such level of mass loadings so far. The excellent cyclic stability of the TCGSi electrodes can be mainly attributed to their high structural stability (Supporting Information Figure S8), where the TCG assemblies allow for better accommodation of the volume variation of silicon impregnated, creation of efficient bicontinuous channels for the transport of both electrons and lithium ions, as well as improvement of the Si interface. Under the same conditions, it is evident that the G-Si control electrode demonstrates fast capacity fade after 30 cycles, delivering only 29% of its initial value at 2 A g−1 after 200 cycles; the SiNP electrode decays even more quickly. We note that the relatively low first-cycle Coulombic efficiency (72%) of the TCG-Si electrodes is attributed to the side reactions on the electrode surfaces and interfaces, as well as to the SEI formation. This disadvantage may be diminished by prelithiation as reported elsewhere.18 For subsequent cycles, the average Coulombic efficiency of the TCG-Si electrode is as high as 99%, reflecting the reversibility of the electrode reaction. The high Coulombic efficiency may originate from the presence of TC on silicon and the addition of electrolyte additive (fluoroethylene carbonate, FEC) that is known to help form stable SEI layers on silicon. It must be pointed out that this value should be further improved from the practical viewpoint, for example, by creating more stable SEI layers without sacrificing the simplicity of the material/electrode fabrication process, whereas the impressively high Coulombic efficiency (e.g., 99.9%) has been achieved by elaborately engineering the voids in silicon/carbon core−shell E

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(∼3 mA cm−2), the reversible areal capacity of above 6 mAh cm−2 is achieved, which significantly exceeds the capacity (4 mAh cm−2) of a commercial lithium-ion battery cell with graphite as the anode. Even at a much higher rate of 4 A g−1 (equal to ∼15 mA cm−2), the areal capacity is still above 4 mAh cm−2 and remains stable over 100 cycles. In the cases of slightly lower material mass loadings of 0.8 and 1.9 mg cm−2, the achieved areal capacity (∼1 and ∼2.6 mAh cm−2 at 3.2 and 3.8 mA cm−2, respectively) along with stable cycling over 200 cycles is quite competitive as well. The high areal capacity and capacity retention, which are obtained at such high current rates (3−15 mA cm−2) as well as at a mass loading level 1 order of magnitude higher than that of many reported silicon anodes, have rarely been described for silicon anodes. In principle, stable cycling of an electrode with high material mass loading requires structural uniformity throughout the whole electrode because even small changes evoked by local inhomogeneity could accumulate across the thickness of the electrode and degrade the electrode.8 The outstanding performance at high mass loadings achieved further manifests the successful design of the TCG-Si, as well as high flexibility of the involved fabrication protocol that is desirable for different application requirements. In conclusion, silicon nanoparticle impregnated assemblies of templated carbon bridged oriented graphene, as a novel material/electrode design formula, has been proposed and developed by a modified vacuum filtration process followed by thermal treatment. We have demonstrated their direct use as LIB anodes with exceptional lithium storage performances, including high gravimetric capacity (1390 mAh g−1 at 2 A g−1 with respect to the total electrode weight), high volumetric capacity (1807 mAh cm−3), superior rate capability (900 mAh g−1 at 8 A g−1), excellent cyclic stability (0.025% decay per cycle over 200 cycles), and competing areal capacity (as high as 4 and 6 mAh cm−2 at 15 and 3 mA cm−2, respectively). Such combined level of performance can be attributed to the templated carbon bridged oriented graphene assemblies involved. This engineered graphene bulk assemblies not only create a robust bicontinuous network for rapid transport of both electrons and lithium ions throughout the electrode even at high material mass loading but also allow achieving a substantially high material tap density. Combined with a simple and flexible fabrication protocol as well as practically scalable raw materials (e.g., silicon nanoparticles and graphene oxide), the material/electrode design developed opens up new avenues for high-performance Si-based electrodes practically applicable to future lithium-ion batteries. Generally, this study expands the exceptional potential of graphene in improving performances of silicon and also other newly emerging electrode materials, and we expect the new bulk hybrid architecture pioneered to have potential applications in the other areas such as energy conversion and sensing.



Letter

AUTHOR INFORMATION

Corresponding Author

* E-mail: [email protected]. Notes

The authors declare no competing financial interest.



ACKNOWLEDGMENTS The authors acknowledge support from the National Natural Science Foundation of China (Grant No. 21173057, 51302045), the Ministry of Science and Technology of China (2012CB933403), and CAS Key Laboratory of Nanosystem and Hierarchical Fabrication.



REFERENCES

(1) Chiang, Y.-M. Science 2010, 330, 1485−1486. (2) Tarascon, J. M.; Armand, M. Nature 2001, 414, 359−367. (3) Choi, N.-S.; Chen, Z.; Freunberger, S. A.; Ji, X.; Sun, Y. K.; Amine, K.; Yushin, G.; Nazar, L. F.; Cho, J.; Bruce, P. G. Angew. Chem., Int. Ed. 2012, 51, 9994−10024. (4) Kasavajjula, U.; Wang, C. S.; Appleby, A. J. J. Power Sources 2007, 163, 1003−1039. (5) Li, H.; Huang, X.; Chen, L.; Wu, Z.; Liang, Y. Electrochem. SolidState Lett. 1999, 2, 547−549. (6) Chan, C. K.; Peng, H. L.; Liu, G.; McIlwrath, K.; Zhang, X. F.; Huggins, R. A.; Cui, Y. Nat. Nanotechnol. 2008, 3, 31−35. (7) Magasinski, A.; Dixon, P.; Hertzberg, B.; Kvit, A.; Ayala, J.; Yushin, G. Nat. Mater. 2010, 9, 353−358. (8) Liu, N.; Lu, Z.; Zhao, J.; McDowell, M.; Lee, H.; Zhao, W.; Cui, Y. Nat. Nanotechnol. 2014, 9, 187−192. (9) Hu, Y.-S.; Demir-Cakan, R.; Titirici, M.-M.; Müller, J.-O.; Schlögl, R.; Antonietti, M.; Maier, J. Angew. Chem., Int. Ed. 2008, 47, 1645− 1649. (10) Yoo, J.-K.; Kim, J.; Jung, Y. S.; Kang, K. Adv. Mater. 2012, 24, 5452−5456. (11) Wang, B.; Li, X.; Qiu, T.; Luo, B.; Ning, J.; Li, J.; Zhang, X.; Liang, M.; Zhi, L. Nano Lett. 2013, 13, 5578−5584. (12) Yi, R.; Dai, F.; Gordin, M. L.; Chen, S.; Wang, D. Adv. Energy Mater. 2013, 3, 295−300. (13) Jung, D. S.; Hwang, T. H.; Park, S. B.; Choi, J. W. Nano Lett. 2013, 13, 2092−2097. (14) Liu, B.; Soares, P.; Checkles, C.; Zhao, Y.; Yu, G. Nano Lett. 2013, 13, 3414−3419. (15) Ge, M.; Lu, Y.; Erius, P.; Rong, J.; Fang, X.; Mecklenburg, M.; Zhou, C. W. Nano Lett. 2014, 14, 261−268. (16) Hassan, F. M.; Chabot, V.; Elsayed, A. R.; Xiao, X.; Chen, Z. Nano Lett. 2014, 14, 277−283. (17) Zhang, R.; Du, Y.; Li, D.; Shen, D.; Yang, J.; Guo, Z.; Liu, H. K.; Elzatahry, A. A.; Zhao, D. Adv. Mater. 2014, 26, 6749−6755. (18) Li, X.; Gu, M.; Hu, S.; Kennard, R.; Yan, P.; Chen, X.; Wang, C.; Sailor, M. J.; Zhang, J.-G.; Liu, J. Nat. Commun. 2014, 5, 4105. (19) Sun, C.-F.; Zhu, H.; Okada, M.; Gaskell, K.; Inoue, Y.; Hu, L.; Wang, Y. Nano Lett. 2015, 15, 703−708. (20) Bai, H.; Li, C.; Shi, G. Adv. Mater. 2011, 23, 1089−1115. (21) Huang, X.; Qi, X.; Boey, F.; Zhang, H. Chem. Soc. Rev. 2012, 41, 666−686. (22) Wang, H.; Dai, H. Chem. Soc. Rev. 2013, 42, 3088−3113. (23) Han, S.; Wu, D.; Li, S.; Zhang, F.; Feng, X. Small 2013, 9, 1173−1187. (24) Xia, B.; Yan, Y.; Wang, X.; Lou, X. W. Mater. Horiz. 2014, 1, 379−399. (25) Nguyen, K. T.; Zhao, Y. Nanoscale 2014, 6, 6245−6266. (26) Xie, J. L.; Guo, C. X.; Li, C. M. Energy Environ. Sci. 2014, 7, 2559−2579. (27) Evanoff, K.; Magasinski, A.; Yang, J. B.; Yushin, G. Adv. Energy Mater. 2011, 1, 495−498. (28) He, Y.-S.; Gao, P.; Chen, J.; Yang, X.; Liao, X.; Yang, J.; Ma, Z.F. RSC Adv. 2011, 1, 958−960.

ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.nanolett.5b02697. Additional information for the detailed synthesis and characterization of the samples, and Figure S1−S10. (PDF) F

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Nano Letters (29) Luo, J. Y.; Zhao, X.; Wu, J. S.; Jang, H. D.; Kung, H. H.; Huang, J. X. J. Phys. Chem. Lett. 2012, 3, 1824−1829. (30) Zhou, X.; Yin, Y.; Wan, L.-J.; Guo, Y.-G. Adv. Energy Mater. 2012, 2, 1086−1090. (31) Xin, X.; Zhou, X.; Wang, F.; Yao, X.; Xu, X.; Zhu, Y.; Liu, Z. J. Mater. Chem. 2012, 22, 7724−7730. (32) Wen, Y.; Zhu, Y.; Langrock, A.; Manivannan, A.; Ehrman, S. H.; Wang, C. Small 2013, 9, 2810−2816. (33) Zhou, M.; Cai, T.; Pu, F.; Chen, H.; Wang, Z.; Zhang, H.; Guan, S. ACS Appl. Mater. Interfaces 2013, 5, 3449−3455. (34) Zhu, Y.; Liu, W.; Zhang, X.; He, J.; Chen, J.; Wang, Y.; Cao, T. Langmuir 2013, 29, 744−749. (35) Ko, M.; Chae, S.; Jeong, S.; Oh, P.; Cho, J. ACS Nano 2014, 8, 8591−8599. (36) Wang, B.; Li, X.; Luo, B.; Hao, L.; Zhou, M.; Zhang, X.; Fan, Z.; Zhi, L. Adv. Mater. 2015, 27, 1526−1532. (37) Kovalenko, I.; Zdyrko, B.; Magasinski, A.; Hertzberg, B.; Milicev, Z.; Burtovyy, R.; Luzinov, I.; Yushin, G. Science 2011, 334, 75−79. (38) Wang, J.-Z.; Zhong, C.; Chou, S.-L.; Liu, H.-K. Electrochem. Commun. 2010, 12, 1467−1470. (39) Lee, J. K.; Smith, K. B.; Hayner, C. M.; Kung, H. H. Chem. Commun. 2010, 46, 2025−2027. (40) Zhou, X.; Cao, A.; Wan, L.-J.; Guo, Y.-G. Nano Res. 2012, 5, 845−853. (41) Wang, B.; Li, X.; Luo, B.; Jia, Y.; Zhi, L. Nanoscale 2013, 5, 1470−1474. (42) Wang, B.; Li, X.; Zhang, X.; Luo, B.; Jin, M.; Liang, M.; Dayeh, S. A.; Picraux, S. T.; Zhi, L. ACS Nano 2013, 7, 1437−1445. (43) Zhao, X.; Hayner, C. M.; Kung, M. C.; Kung, H. H. Adv. Energy Mater. 2011, 1, 1079−1084. (44) De Volder, M. F. L.; Tawfick, S. H.; Baughman, R. H.; Hart, A. J. Science 2013, 339, 535−539. (45) Li, N.; Chen, Z.; Ren, W.; Li, F.; Cheng, H.-M. Proc. Natl. Acad. Sci. U. S. A. 2012, 109, 17360−17365. (46) Ji, J.; Ji, H.; Zhang, L.; Zhao, X.; Bai, X.; Fan, X.; Zhang, F.; Ruoff, R. S. Adv. Mater. 2013, 25, 4673−4677. (47) Chang, J.; Huang, X.; Zhou, G.; Cui, S.; Hallac, P. B.; Jiang, J.; Hurley, P. T.; Chen, J. Adv. Mater. 2014, 26, 758−764. (48) Jing, S.; Jiang, H.; Hu, Y.; Li, C. J. Mater. Chem. A 2014, 2, 16360−16364. (49) Chen, S.; Bao, P.; Huang, X.; Sun, B.; Wang, G. Nano Res. 2014, 7, 85−94. (50) Whittingham, M. S. MRS Bull. 2008, 33, 411−419. (51) Gogotsi, Y.; Simon, P. Science 2011, 334, 917−918. (52) Zhang, C.; Lv, W.; Tao, Y.; Yang, Q.-H. Energy Environ. Sci. 2015, 8, 1390−1403. (53) Yun, Y. J.; Hong, W. G.; Kim, W.-J.; Jun, Y.; Kim, B. H. Adv. Mater. 2013, 25, 5701−5705. (54) Yang, X.; Cheng, C.; Wang, Y.; Qiu, L.; Li, D. Science 2013, 341, 534−537. (55) Liu, N.; Wu, H.; McDowell, M. T.; Yao, Y.; Wang, C.; Cui, Y. Nano Lett. 2012, 12, 3315−3321. (56) Wang, B.; Li, X.; Zhang, X.; Luo, B.; Zhang, Y.; Zhi, L. Adv. Mater. 2013, 25, 3560−3565. (57) Jeong, S.; Lee, J.-P.; Ko, M.; Kim, G.; Park, S.; Cho, J. Nano Lett. 2013, 13, 3403−3407.

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DOI: 10.1021/acs.nanolett.5b02697 Nano Lett. XXXX, XXX, XXX−XXX