Double-Network Gel-Enabled Uniform Incorporation of Metallic

Subscriber access provided by Iowa State University | Library

Article

Double-Network Gel-Enabled Uniform Incorporation of Metallic Matrices with Silicon Anodes Realizing Enhanced Lithium Storage Feng Li, Zhuangzhuang Wang, Weiqi Liu, Tao Yan, Chuanxin Zhai, Ping Wu, and Yiming Zhou ACS Appl. Energy Mater., Just Accepted Manuscript • DOI: 10.1021/acsaem.9b00069 • Publication Date (Web): 04 Feb 2019 Downloaded from http://pubs.acs.org on February 5, 2019

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

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

Page 1 of 20 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 Energy Materials

Double-Network Gel-Enabled Uniform Incorporation of Metallic Matrices with Silicon Anodes Realizing Enhanced Lithium Storage Feng Li,† Zhuangzhuang Wang,† Weiqi Liu,† Tao Yan,‡ Chuanxin Zhai,‡ Ping Wu*,† and Yiming Zhou*,† †Jiangsu

Key Laboratory of New Power Batteries, Jiangsu Collaborative Innovation Center of

Biomedical Functional Materials, School of Chemistry and Materials Science, Nanjing Normal University, Nanjing 210023, PR China. ‡Amprius

(Wuxi) Co. Ltd., Wuxi, 214000, PR China.

Abstract Silicon–metal (Si–M) binary materials manifest high tap densities, areal capacities, and desirable Listorage behavior benefiting from metallic matrices, and thus have been regarded as promising anodic choices in next-generation Li-ion batteries. To fully realize the hybridization merits, the uniform incorporation of metallic components with silicon is a prerequisite, yet remains a significant challenge via facile and economic routes. Herein, we develop an all-inorganic double-network gel-enabled methodology for the uniform incorporation of metallic matrices with silicon anodes. Taking Si–Ti binary materials as an example, the simultaneous gelation reaction for both SiO2 and TiO2 gel networks ensures the formation of integrative SiO2–TiO2 double-network gels, guaranteeing the uniform incorporation of metallic titanium with nanoporous silicon framework via subsequent magnesiothermic coreduction process. Thanks to the unique structural and compositional features, the as-prepared Si–Ti binary framework exhibits long cycle life (1161 mA h g-1 after 100 cycles at 0.5 A g-1) and high rate capability (1405 and 1190 mA h g-1 at 1 and 2 A g-1, respectively). KEYWORDS: Li-ion batteries, silicon–metal binary anodes, interconnected framework structure, double-network gels, magnesiothermic coreduction route

ACS Paragon Plus Environment

1

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

Page 2 of 20

1. INTRODUCTION Among various high-capacity alloying-type anodes for Li-ion batteries (LIBs), silicon is the most promising one to replace conventional graphite due to its ultrahigh reversible capacity at room temperature (3578 mA h g-1 for Li15Si4) and proper redox potential (~0.4 V vs. Li/Li+).1-4 However, the drastic volume expansion (290% for Li15Si4) during Li insertion/extraction leads to prominent electrode pulverization and poor cycling performance, and meanwhile, the low intrinsic electrical conductivity (10-5–10-3 S cm-1) and Li+ diffusion coefficient (10-14–10-13 cm2 s-1) result in sluggish charge-transfer capability and undesirable rate performance.5,6 To realize robust and fast lithium storage, hybridizing silicon with carbon components has proved to be a general and effective strategy since carbon can accommodate volume variations and increase charge-transport capability to a large extent.1,7-9 Besides these buffering and conducting merits, metallic components possess additional advantages as hybridization matrices for silicon anodes, in comparison with carbon counterparts. First, silicon–metal (Si–M) binary anodes generally exhibit higher tap densities and areal capacities than Si–C binary materials.10,11 Second, metallic species especially transition metals minimize the solid-electrolyteinterface (SEI) layer formation and other irreversible side reactions from native SiOx layer and active adsorption hetero-atoms/groups (–OH, –O–, and –H), enabling high initial Coulombic efficiencies.12,13 Last, metallic components can act as diffusion barriers to limit the full lithiation of silicon to form crystalline Li15Si4 phase, and the inhibition of such amorphous/crystalline phase transition greatly improve their structural stability and cyclic life.13-17 To fully realize these hybridization effects, the uniform incorporation of metallic matrices with silicon is a prerequisite, yet remains a significant challenge through facile and economic procedures. With respect to synthetic routes, magnesiothermic reduction methodology converts silica directly to Si at a moderate temperature, and has been considered as one of the promising and practical processes owing to its short reaction time, low cost, and energy consumption.18-20 Recently, magnesiothermic coreduction route has been further adopted to synthesize Si–M binary anodes using the nanocomposites of SiO2 and metal oxides as precursors.21-23 However, silicon and metal oxides are introduced into the oxide precursors in separate steps, leading to core-shell structured rather than homogeneous oxide ACS Paragon Plus Environment

2

Page 3 of 20 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


precursors and Si–M binary products.21-23 In this regards, exploring new approaches based on magnesiothermic coreduction for synthesizing homogeneous Si–M binary anodes is highly desirable so as to fully utilize the hybridization merits from metallic matrices. As inspired, we develop an all-inorganic double-network gel-enabled methodology for the uniform incorporation of metallic matrices with silicon anodes. Taking Si–Ti binary materials as an example, oxygen-bridged SiO2 and TiO2 inorganic polymer hydrogels have been selected to construct SiO2–TiO2 double-network hydrogel, acting as a decent precursor in this gel-enabled route. The simultaneous gelation reaction (hydrolysis–condensation reaction) for both SiO2 and TiO2 gel networks ensures the formation of integrative SiO2–TiO2 double-network gels. As shown in Figure 1, the highly intertwined SiO2 and TiO2 networks are concurrent reduced via a magnesiothermic reduction process, and as a result, metallic titanium is uniformly distributed within three-dimensional (3D) nanoporous silicon framework, yielding the final Si–Ti binary framework. When studied as an anode material in LIBs, the Si–Ti binary framework manifests greatly enhanced lithium storage performances in terms of reversible capacity, cycling life, and rate capability in comparison with single Si framework.

Figure 1 Schematic illustration of the synthetic procedure of the Si–Ti binary framework.

2. EXPERIMENTAL SECTION Preparation of the SiO2–TiO2 double-network aerogel. The SiO2–TiO2 double-network hydrogel was prepared by a facile sol-gel method. First, 2 mL tetraethyl orthossilicate (TEOS) and 2.8 mL 2 M HNO3 aqueous solution were mixed and stirred at 50 oC for 0.5 h. Then, 0.2 mL titanium butoxide (TBOT) was added slowly into the above solution, and this mixed solution was stirred for 2 h to form ACS Paragon Plus Environment

3


Page 4 of 20

SiO2–TiO2 double-network hydrogel. Subsequently, this hydrogel was sealed and kept in an oven at 50 oC

for 24 h to strengthen the gel structure. Finally, the as-formed hydrogel was freeze-dried to obtain the

SiO2–TiO2 double-network aerogel. Preparation of the Si–Ti binary framework. The as-prepared double-network aerogel and Mg powder were mixed together in a mass ratio of 1:1 and then heated in a tube furnace at 700 oC for 6 h under 5% H2/Ar atmosphere. The resulting powder was etched in a 1 M HCl aqueous solution for 6 h to remove byproducts (MgO and small amount of Mg2Si), yielding the final Si–Ti binary framework. Characterization. The morphology, composition, and structure of the the as-synthesized samples were characterized by X-ray powder diffraction (XRD, Rigaku D/max 2500/PC), scanning electron microscopy (SEM, Hitachi SU8220), transmission electron microscopy (TEM, Hitachi H-7650) and high-resolution transmission electron microscopy (HRTEM, JEOL JEM-2010F) coupled with an energy-dispersive X-ray spectrometer (EDS, Thermo Fisher Scientific). The Fourier transform infrared (FTIR) spectra were carried out on a Bruker Tensor 27 spectrometer. Nitrogen adsorption/desorption tests were performed at 77 K using a Micromeritics ASAP 2050 analyzer, and their specific surface area, pore volume, and pore size distribution were obtained using Brunauer–Emmett–Teller (BET) and Barrett–Joyner–Halenda (BJH) methods, respectively. Electrochemical measurement. Electrochemical measurements were conducted by 2025-type half coin cells (20 mm in diameter, 2.5 mm in thickness) with copper foil as the current collectors. The working electodes were constructed as follows: 70 wt% active material (e.g., Si–Ti binary framrwork), 15% conductive material (Super P), and 15% binder (carboxyl methyl cellulose) in a water solvent. The slurry was pasted on a copper foil at room temperature and dried under vacuum at 120 oC for 12 h. The loading density of the active materials on copper foils was about 1.5 mg cm-2. The coin cells were assembled with lithium foil as the counter electrode, 1 M LiPF6 dissolved in ethylene carbonate (EC)/dimethyl carbonate (DMC) (EC/DMC, 1:1 in volume) containing fluoroethylene carbonate (FEC) additive (5 vol%) as the electrolyte. The coin cells were assembled in an argon-filled glove box (Innovative Technology, IL-2GB). The cycling performances of the products were measured on a LANHE CT2001A battery tester in the potential range of 0.01-1.2 V (0.1 A g-1 for the first cycle and 0.1 ACS Paragon Plus Environment

4

Page 5 of 20 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


to 2 A g-1 for subsequent cycles). The cyclic voltammetry (CV) measurements were conducted on a CHI 660B electrochemical workstation in the potential range of 0-1.2 V versus Li/Li+ at a scan rate of 0.1 mV s−1. The electrochemical impedance spectroscopy (EIS) data were recorded on a CHI 660B electrochemical workstation with the frequency ranging from 100 kHz to 0.01 Hz.

3. RESULTS AND DISCUSSION Nanostructured hydrogels usually possess large surface area, highly nanoporous structure, tunable physicochemical properties, and mixed pathways for both charge and mass, and thus these gel systems and their derivatives have been widely used in energy-related applications.24-39 Double-network hydrogels, containing two kinds of 3D intertwined gel networks, combine the compositional merits of each network and might yield intriguing synergistic effects, thus becoming more promising materials in energy storage and conversion areas.28-32 Here, we develop an all-inorganic double-network gel-enabled methodology for the uniform incorporation of metallic titanium with silicon anodes. The simultaneous hydrolysis–condensation reactions of TEOS and TBOT generate a uniform and light-yellow SiO2−TiO2 double-network hydrogel, as shown in Figure 2a. After freeze-drying, the double-network aerogel inherits the structural characteristics of hydrogel precursor and exists in the form of 3D nanoporous structure (Figure 2b). The HRTEM image and XRD pattern suggest the amorphous nature of this SiO2−TiO2 aerogel (Figure 2c and S1). Additionally, the Si, Ti, and O elemental peaks can be clearly observed from its EDS spectrum (Figure 2d). The atomic ratio of Si:Ti is 13.9:1, very close to its feeding ratio of TEOS/TBOT. The physical and chemical interactions of SiO2 and TiO2 networks in the double-network gel have been further examined by elemental mappings and FTIR. The scanning transmission electron microscopy (STEM) and corresponding elemental mappings reveal the homogeneous distribution of Si, Ti, and O signals within the entire gel framework, demonstrating that single Si- and Ti-based networks are highly intertwined in a physical state in the double-network product (Figure 2e). Figure 2f shows the FTIR spectrum of the SiO2−TiO2 aerogel. Besides the characteristic vibrations of Si–O–Si and Ti–O–Ti from single SiO2 and TiO2 networks, an obvious peak at 956 cm-1 can be assigned to the stretching ACS Paragon Plus Environment

5


Page 6 of 20

vibration of Si–O–Ti, indicating the SiO2 and TiO2 networks are chemically bonded in the doublenetwork aerogel.40,41 These results confirm that SiO2 and TiO2 gel networks are physical-intertwined and chemical-binded in the double-network gels.

Figure 2 (a) Photograph of the SiO2–TiO2 double-network hydrogel. (b) TEM image, (c) HRTEM image, (d) EDS spectrum, (e) STEM-EDS elemental mappings, and (f) FTIR spectrum of the SiO2–TiO2 double-network aerogel. Insets in (a-c) are their model, TEM image with a lower magnification, and SAED pattern, respectively.

In this double-network gel-enabled route, the construction of such integrative gel precursors is a prerequisite of subsequently uniform incorporation of metallic matrices with silicon anodes for boosting energy storage. During the magnesiothermic step, the SiO2 and TiO2 gel networks were co-reduced to metallic Si and Ti, and Ti component further reacted with adjacent Si to form intermetallic TiSi2, which can be described by the following equations: SiO2 + 2Mg → 2MgO+ Si

(1)

TiO2 + 2Mg → 2MgO + Ti

(2)

Ti + Si → TiSi2

(3)


6

Page 7 of 20 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


Such magnesiothermic coreduction processes have been confirmed by the XRD pattern of the asformed Si−Ti binary framework (Figure 3c). As illustrated, the three sets of diffraction peaks could be well indexed to Si (JCPDS no. 27-1402), TiSi2 (JCPDS no. 31-1405) and metastable TiSi2 (MS TiSi2), respectively, noting that the metastable phase cannot be totally converted into stable TiSi2 under 800 oC and its atomic configuration is assumed in reference to ZrSi2 of a Cmcm space group.42,43 Figure 3a and b show the TEM images of the Si−Ti binary framework. As clearly seen, this Si−Ti binary product possesses the mutual structure features of gel-derived materials and maintains a 3D framework structure.24-30 The selected-area electron diffraction (SAED) pattern shows the diffraction rings from Si, TiSi2, and metastable TiSi2 (Inset in Figure 3b), consistent with its XRD pattern. Moreover, the Si and TiSi2 nanocrystals are interconnected rather than aggregated within the binary framework, as clearly revealed by its structural model (Inset in Figure 3a) and SEM images (Figure S2). The interconnected framework structure accompanied by abundant mesopores has been further confirmed and highlighted by red dotted lines in its HRTEM image (Figure 3d), and could provide mixed conducting pathways for both electron and ions, ensuring the enhanced charge-transport capability and rate performance toward lithium storage.31,34 Additionally, the observed three kinds of lattice fringes with interlayer distances of 0.31, 0.23, and 0.22 nm from the HRTEM image can be ascribed to (111) plane from Si, (311) plane from TiSi2, and (131) plane from MS TiSi2, respectively, suggesting the homogeneous integration of metallic titanium with silicon in this local interconnected region. Meanwhile, the uniform incorporation of Ti with Si in the entire framework has been confirmed by its STEM-EDS elemental mappings, which shows uniformly distributed Si and Ti elemental signals (Figure 3e). Additionally, the atomic ratio of Si:Ti in the binary framework is 13.0:1 (Figure S3), slightly lower than the value in the SiO2−TiO2 double-network aerogel (13.9:1). The decrease of Si:Ti atomic ratio is due to the formation of small amount of Mg2Si during magnesiothermic coreduction process, as revealed by the XRD pattern of the annealing product before acid etching process (Figure S4). The nanoporous characteristics of the Si−Ti binary framework has been further demonstrated by nitrogen adsorption and desorption test (Figure 3f), and the determined large surface area (162.7 m2 g-1), high pore volume (0.73 cm3 g-1), and uniform


7


Page 8 of 20

mesopores with average size of 18.1 nm accelerate electrode-electrolyte contact and facilitate stress release of this binary anode during cycling.31-36

Figure 3 Compositional and structural characteristics of the Si–Ti binary framework: (a,b) TEM images, (c) XRD pattern, (d) HRTEM image, (e) STEM-EDS elemental mappings, and (f) nitrogen adsorption/desorption isotherms and pore-size distribution. Inset in (a) is its model. Inset in (b) is its SAED pattern.

To explore the hybridization merits from metallic matrix, we took Si−Ti binary framework as a typical example and examined its electrochemical performance toward lithium storage. For comparison, single Si framework has been prepared by reducing SiO2 gel rather than double-network gel (Figure S5). Figure 4a and Figure S6 show the initial five CV curves of the Si−Ti binary framework and single Si framework (0-1.2 V, 0.1 mV s-1). As can be seen, these CV profiles are both characteristic of alloyingtype Li-storage mechanisms,44,45 contributed by silicon nanoparticles, whereas TiSi2 nanocrystals are inert toward lithium storage.14,46 Specifically, the cathodic peaks below 0.3 V could be assigned to the formation of LixSi alloys, and the corresponding anodic peaks at about 0.37 and 0.55 V correspond to stepwise Li-extraction processes from LixSi alloys.12,47 It is worth of mentioning that these peak ACS Paragon Plus Environment

8

Page 9 of 20 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


intensities increase gradually during testing, which might be due to the phase transition from Si nanocrystals to amorphous nanoparticles together with electrode-activation processes in silicon anodes.48 Figure 4b displays the cycling stability for the Si−Ti binary framwork compared with single Si framework. As observed, the binary framework product manifests maredly enhanced cyclic life and thus higher reversible capacities. The average capacity fading for Si−Ti binary framework is 0.21% per cycle from 2 to 100 cycles (0.5 A g-1), much lower than the value of Si framework (0.80%). Thus, the Si−Ti binary product is able to exhibit a high discharge capacity of 1161 mA h g-1 at the 100th cycle, much higher than that of Si framework (576 mA h g-1) and the theoretical capacity of graphite (372 mA h g-1). Moreover, even at a high current density of 2 A g-1, the Si−Ti binary framework manifests a reversible capacity of 789 mA h g-1 after 200 cycles (Figure 4d), with an average capacity fading of 0.09% per cycle from 2 to 200 cycles. Ti-enabled remarkable structural stability can be responsible for the improved cyclic life, and the detailed mechanisms have been revealed by electrochemical performance comparison of Si−Ti binary frameworks with different Si:Ti molar ratios (13.0:1 and 7.8:1) and single Si framework (Figure S7). The reversible capacities in the second cycle for these three samples have been chosen to compare with their theoretical capacities considering that TiSi2 is inactive (Figure 4c). As observed, integration of Ti with Si decreases the reversible capacity of the Si-based anodes, and moreover, the gap between the experimental and theoretical capacities becomes larger and larger with the increased Ti contents. This phenomenon might be explained by the Ti-enabled inhibition of full lithiation

from

amorphous

LixSi

to

crystalline

Li15Si4,

and

the

suppression

of

such

amorphous−crystalline phase transition plays a critical role in the structural stability and cyclic life of Si-based anodes.13-16 The rate capability of the Si−Ti binary framework and single Si framework has been further examined (Figure 4e). As can be seen, the discharge capacities of the Si−Ti product are much higher than those of Si sample at current densities from 0.2 to 2 A g-1, and the binary framework is able to exhibit high average capacities of 1623, 1512, 1405, and 1190 mA h g-1 at 0.2, 0.5, 1, and 2 A g-1, respectively. Moreover, the average capacity retention at 2 A g-1 vs 0.2 A g-1 is 73% for the binary framework, much higher than those of single Si framework (19%). Ti-enabled fast charge-transport ACS Paragon Plus Environment

9


Page 10 of 20

kinetics can be responsible for the enhanced rate capability, and has been further revealed by EIS tests. Figure 4f shows the Nyquist plots of the Si−Ti and Si framework after five cycles. The semicircle diameter for the binary framework in high frequency region is much smaller than that of single Si product, demonstrating Ti-enabled lower charge-transfer resistance. Specifically, these impedance plots are fitted with an equivalent circuit model (Figure S8), and the fitted charge-transfer resistance (RCT) of the Si−Ti framework is only 27 Ω, much lower than that of Si framework (88 Ω, Table S1).

Figure 4 Lithium storage performance of the Si–Ti binary framework compared with single Si framework: (a) CV curves, (b,d) cycling stability, (c) theoretical and experimental capacity with respect to Si content, (e) rate capability, and (f) Nyquist plots.

The cyclic and rate performances of the Si−Ti binary framework are comparable to those of state-ofthe-art silicon–metal (Si–M) anodes, as listed in Table S2. The uniform incorporation of titanium with silicon together with the interconnected framework structure is the key factor for the Si−Ti binary anode to demonstrate remarkable structural stability and enhanced charge-transport capability. Such compositional and structural merits have been schematically illustrated by the lithiation/delithiation processes of the Si−Ti binary framework (Figure 5a). Specifically, the hierarchical 0D to 3D framework structure, with large surface area and high pore volume, accommodates volume variations and ACS Paragon Plus Environment

10

Page 11 of 20 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


suppresses electrode pulverization to a large extent,24-29 and meanwhile, the uniform-distributed inactive TiSi2 nanocrystals further buffer volume expansion and inhibit the full lithiation from amorphous LixSi to crystalline Li15Si4,13-17 leading to remarkable structural stability and long-term cyclic life of the Si−Ti binary framework. Moreover, the interconnected framework offers continuous 0D to 3D pathways for electrons, and the internally abundant mesopores facilitate the electrode-electrolyte contact.24-29 Such 3D mixed conducting networks for electron/Li-ion ensure the greatly enhanced charge-transport capability and high-rate performance.26,31,34-36 The lithium-storage behavior and remarkable structural stability of the Si−Ti binary framework have been further confirmed by its electron microscope characterizations after cycling. Figure 5b-e shows the structural and compositional features of the binary anode in a fully delithiated state after 100 cycles. As observed, the 3D framework structure is well preserved (Figure 5b), and the HRTEM view displays that the delithiated product also exists in the form of interconnected 0D to 3D structure (Figure 5c). Additionally, the HRTEM image and SAED pattern confirm the phase transition from Si nanocrystals to amorphous nanoparticles upon cycling and the inert nature of TiSi2 nanocrystals toward lithium storage (Figure 5c and inset in Figure 5b). Also, the Raman spectra of the uncycled Si–Ti binary framework and its fully de-lithiated products after 5, 20, and 100 cycles indicates a gradual transformation process from crystalline Si to amorphous counterparts upon repeated Li insertion/extraction (Figure S9).49,50 Moreover, the STEM-EDS elemental mappings reveal the homogeneous distribution of Si and Ti signals within the delithiated binary framework (Figure 5d and e). These results verify that the agglomeration and pulverization of the binary anode can be effectively restricted upon repeated Liinsertion/extraction, and the Si−Ti binary framework is therefore able to manifest remarkable structural stability and lithium-storage performance especially long-term cycling stability.


11


Page 12 of 20

Figure 5 (a) Schematic illustration of the lithiation/delithiation processes for Si–Ti binary framework and (b-e) microscopic structural features of the Si–Ti binary framework in a fully de-lithiated state after 100 cycles: (b) TEM image, (c) HRTEM image, and (d, e) STEM-EDS elemental mappings.

4. CONCLUSION To summarize, we propose a magnesiothermic coreduction route for the uniform incorporation of metallic matrices with silicon anodes using double-network hydrogels as precursors. The simultaneous gelation reaction (hydrolysis–condensation reaction) for both SiO2 and TiO2 gel networks ensures the ACS Paragon Plus Environment

12

Page 13 of 20 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


formation of integrative SiO2–TiO2 double-network gels, which is a prerequisite of subsequently integrating metallic titanium into nanoporous silicon framework effectively and uniformly. As a proofof-concept demonstration of the hybridization merits from titanium, the Si–Ti binary framework manifests greatly enhanced lithium storage performances in terms of reversible capacity, cyclic life, and rate capability in comparison with single Si framework. Moreover, this work provides new insight into uniformly incorporating of metallic matrices with silicon anodes for boosting lithium storage.

ASSOCIATED CONTENT Supporting Information The Supporting Information is available free of charge on the ACS Publications website. XRD patterns, SEM images, EDS spectrum, TEM images, HRTEM image, CV curves, cycling performance, equivalent circuit model and fitting results, Raman spectra, and comparison of lithium storage performance.

AUTHOR INFORMATION Corresponding Authors *E-mail: [email protected]; [email protected]

Notes The authors declare no competing financial interest.

ACKNOWLEDGMENTS The authors appreciate the financial supports from National Natural Science Foundation of China (51401110), Natural Science Foundation of Jiangsu Higher Education Institutions of China (16KJB150023), and a project funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions. ACS Paragon Plus Environment

13


Page 14 of 20

REFERENCES (1) Luo, F.; Liu, B.; Zheng, J.; Chu, G.; Zhong, K.; Li, H.; Huang, X.; Chen, L. Review—NanoSilicon/Carbon Composite Anode Materials Towards Practical Application for Next Generation Li-Ion Batteries. J. Electrochem. Soc., 2015, 162, A2509–A2528. (2) Jin, Y.; Zhu, B.; Lu, Z.; Liu, N.; Zhu, J. Challenges and Recent Progress in the Development of Si Anodes for Lithium-Ion Battery. Adv. Energy Mater., 2017, 7, 1700715. (3) Zuo, X.; Zhu, J.; Müller-Buschbaum, P.; Cheng, Y. J. Silicon Based Lithium-Ion Battery Anodes: A Chronicle Perspective Review. Nano Energy, 2017, 31, 113–143. (4) Ryu, J.; Hong, D.; Lee, H. W.; Park, S. Practical Considerations of Si-Based Anodes for LithiumIon Battery Applications. Nano Res., 2017, 10, 3970–4002. (5) Du, F. H.; Wang, K. X.; Chen, J. S. Strategies to Succeed In Improving The Lithium-Ion Storage Properties of Silicon Nanomaterials. J. Mater. Chem. A, 2016, 4, 32–50. (6) Liu, L.; Lyu, J.; Li, T.; Zhao, T. Well-Constructed Silicon-Based Materials as High-Performance Lithium-Ion Battery Anodes. Nanoscale, 2016, 8, 701–722. (7) Terranova, M. L.; Orlanducci, S.; Tamburri, E.; Guglielmotti, V.; Rossi, M. Si/C Hybrid Nanostructures for Li-Ion Anodes: An Overview. J. Power Sources, 2014, 246, 167–177. (8) Shoorideh, G,; Ko, B.; Berry, A.; Divvela, M. J.; Kim, Y. S.; Li, Z.; Patel, B.; Chakrapani, S.; Joo, Y. L. Harvesting Interconductivity and Intraconductivity of Graphene Nanoribbons for a Directly Deposited, High-Rate Silicon-Based Anode for Li-Ion Batteries. ACS Appl. Energy Mater., 2018, 1, 1106−1115. (9) Fu, R.; Nie, P.; Shi, M.; Wang, J.; Jiang, J.; Zhang, Y.; Wu, Y.; Fang, S.; Dou, H.; Zhang, X. Rigid Polyimide Buffering Layer Enabling Silicon Nanoparticles Prolonged Cycling Life for Lithium Storage. ACS Appl. Energy Mater., 2018, 1, 948−955. (10) Chae, S.; Ko, M.; Park, S.; Kim, N.; Ma, J.; Cho, J. Micron-Sized Fe–Cu–Si Ternary Composite Anodes for High Energy Li-ion Batteries. Energy Environ. Sci., 2016, 9, 1251–1257.


14

Page 15 of 20 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


(11) Kim, S. O.; Manthiram, A. A Facile, Low-Cost Synthesis of High-Performance Silicon-Based Composite Anodes with High Tap Density for Lithium-Ion Batteries. J. Mater. Chem. A, 2015, 3, 2399– 2406. (12) Zhou, X.; Ren, Y.;Yang, J.; Ding, J.; Zhang, J.; Hu, T.; Tang, J. Si Nanoflake-Assembled Blocks Towards High Initial Coulombic Efficiency Anodes for Lithium-Ion Batteries. Chem. Commun., 2018, 54, 12214–12217. (13) Lee, P. K.; Tahmasebi, M. H.; Ran, S.; Boles, S. T.; Yu, D. Y. W. Leveraging Titanium to Enable Silicon Anodes in Lithium-Ion Batteries. Small, 2018, 14, 1802051. (14) Wang, Y.; Cao, S.; Kalinina, M.; Zheng, L.; Li, L.; Zhu, M.; Obrovac, M. N. Lithium Insertion in Nanostructured Si1-xTix Alloys. J. Electrochem. Soc., 2017, 164, A3006–A3010. (15) Du, Z.; Liu, H.; Ellis, S. N.; Dunlap, R. A.; Zhu, M.; Obrovac, M. N. Electrochemistry of CuxSi1−x Alloys in Li Cells. J. Electrochem. Soc., 2016, 163, A1275–A1279. (16) Du, Z.; Hatchard, T. D.; Bissonnette, P.; Dunlap, R. A.; Obrovac, M. N. Electrochemical Activity of Nano-NiSi2 in Li Cells. J. Electrochem. Soc., 2016, 163, A2456–A2460. (17) Du. Z.; Dunlap, R. A.; Obrovac, M. N. Structural and Electrochemical Investigation of FexSi1-x Thin Films in Li Cells. J. Electrochem. Soc., 2016, 163, A2011–A2016. (18) Bao, Z.; Weatherspoon, M.; Shian, S.; Cai, Y.; Graham, P.; Allan, S.; Ahmad, G.; Dickerson, M.; Church, B.; Kang, Z.; Abernathy, H.; Abernathy III.; Summers, C.; Liu, M.; Sandhage, K. Chemical Reduction of Three-Dimensional Silica Micro-Assemblies into Microporous Silicon Replicas. Nature, 2007, 446, 172–175. (19) Zhang, X.; Qiu, X.; Kong, D.; Zhou, L.; Li, Z.; Li, X.; Zhi, L. Silicene Flowers: A Dual Stabilized Silicon Building Block for High-Performance Lithium Battery Anodes. ACS Nano, 2017, 11, 7476– 7484. (20) Zuo, X.; Xia, Y.; Ji, Q.; Gao, X.; Yin, S.; Wang, M.; Wang, X.; Qiu, B.; Wei, A.; Sun, Z.; Liu, Z.; Zhu, J.; Cheng, Y. J. Self-Templating Construction of 3D Hierarchical Macro-/Mesoporous Silicon from 0D Silica Nanoparticles. ACS Nano, 2017, 11, 889–899.


15


Page 16 of 20

(21) Wu, L.; Yang, J.; Zhou, X.; Tang, J.; Ren, Y.; Nie, Y. Enhanced Electrochemical Performance of Heterogeneous Si/MoSi2 Anodes Prepared by a Magnesiothermic Reduction. ACS Appl. Mater. Interfaces, 2016, 8, 16862–16868. (22) Meng, X.; Deng D. Core−Shell Ti@Si Coaxial Nanorod Arrays Formed Directly on Current Collectors for Lithium-Ion Batteries. ACS Appl. Mater. Interfaces, 2015, 7, 6867–6874. (23) Adpakpang, K.; Park, J.; Oh, S. M.; Kim, S. J.; Hwang, S. J. A. Magnesiothermic Route to Multicomponent Nanocomposites of FeSi2@Si@graphene and FeSi2@Si with Promising Anode Performance. Electrochim. Acta, 2014, 136, 483–492. (24) Zhao, F.; Bae, J.; Zhou, X.; Guo, Y.; Yu, G. Nanostructured Functional Hydrogels as an Emerging Platform for Advanced Energy Technologies. Adv. Mater., 2018, 30, 1801796. (25) Zhao, F.; Shi, Y.; Pan, L.; Yu, G. Multifunctional Nanostructured Conductive Polymer Gels: Synthesis, Properties, and Applications. Acc. Chem. Res, 2017, 50, 1734–1743. (26) Shi, Y.; Zhang, J.; Pan, L.; Shi, Y.; Yu, G. Energy gels: A Bio-Inspired Material Platform for Advanced Energy Applications. Nano Today, 2016, 11, 738–762. (27) Shi, Y.; Yu, G. Designing Hierarchically Nanostructured Conductive Polymer Gels for Electrochemical Energy Storage and Conversion. Chem. Mater., 2016, 28, 2466–2477. (28) Ma, C.; Shi, Y.; Pena, D. A.; Peng, L.; Yu, G. Thermally Responsive Hydrogel Blends: A General Drug Carrier Model for Controlled Drug Release. Angew. Chem. Int. Ed., 2015, 54, 1–6. (29) Shi, Y.; Ma, C.; Peng, L.; Yu, G. Conductive “Smart” Hybrid Hydrogels with PNIPAM and Nanostructured Conductive Polymers. Adv. Funct. Mater., 2015, 25, 1219–1225. (30) Qiu, L.; Liu, D.; Wang, Y.; Cheng, C.; Zhou, K.; Ding, J.; Truong, V. T.; Li, D. Mechanically Robust, Electrically Conductive and Stimuli-Responsive Binary Network Hydrogels Enabled by Superelastic Graphene Aerogels. Adv. Mater., 2014, 26,3333–3337. (31) Shi, H.; Fang, Z.; Zhang, X.; Li, F.; Tang, Y.; Zhou, Y.; Wu, P.; Yu, G. Double-Network Nanostructured Hydrogel-Derived Ultrafine Sn−Fe Alloy in Three-Dimensional Carbon Framework for Enhanced Lithium Storage. Nano Lett., 2018, 18, 3193–3198.


16

Page 17 of 20 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


(32) Zhang, W.; Xu, X.; Zhang, C.; Yu, Z.; Zhou, Y.; Tang, Y.; Wu, P.; Guo, S. 3D Space-Confined Pyrolysis of Double-Network Aerogels Containing In–Fe Cyanogel and Polyaniline: A New Approach to Hierarchically Porous Carbon with Exclusive Fe–Nx Active Sites for Oxygen Reduction Catalysis. Small Methods, 2017, 1, 1700167. (33) Wu, P.; Zhang, A.; Peng, L.; Zhao, F.; Tang, Y.; Zhou, Y.; Yu, G. Cyanogel-Enabled Homogeneous Sb−Ni−C Ternary Framework Electrodes for Enhanced Sodium Storage. ACS Nano, 2018, 12, 759–767. (34) Shi, H.; Zhang, A.; Zhang, X.; Yin, H.; Wang, S.; Tang, Y.; Zhou, Y.; Wu, P. Pyrolysis of CyanoBridged Hetero-Metallic Aerogels: A General Route to Immobilize Sn–M (M=Fe, Ni) Alloys within Carbon Matrix for Stable and Fast Lithium Storage. Nanoscale, 2018, 10, 4962–4968. (35) Zhang, W.; Zhu, X.; Chen, X.; Zhou, Y.; Tang, Y.; Ding, L.; Wu, P. Cyano-Bridged Coordination Polymer Hydrogelderived Sn–Fe Binary Oxide Nanohybrids with Structural Diversity: From 3D, 2D, to 2D/1D and Enhanced Lithium-Storage Performance. Nanoscale, 2016, 8, 9828–9836. (36) Cheng, X.; Zhang, W.; Liu, T.; Zhou, Y.; Tang, Y.; Wu, P. Hydrogel-Derived Nanoporous Sn–In– Ni Ternary Alloy Network for High-Performance Lithium-Storage. Electrochim. Acta, 2016, 210, 530– 538. (37) Zhang, J.; Zhong, H.; Zheng, C.; Xia, Y.; Liang, C.; Huang, H.; Gan, Y.; Tao, X.; Zhang, W. AllSolid-State Batteries with Slurry Coated LiNi0.8Co0.1Mn0.1O2 Composite Cathode and Li6PS5Cl Electrolyte: Effect of Binder Content. J. Power Sources, 2018, 391, 73–79. (38) Zhang, J.; Zheng, Chao.; Lou, J.; Xia, Y.; Liang, C.; Huang, H.; Gan, Y.; Tao, X.; Zhang, W. Poly(Ethylene Oxide) Reinforced Li6PS5Cl Composite Solid Slectrolyte for All-Solid-State Lithium Battery: Enhanced Electrochemical Performance, Mechanical Poperty and Interfacial Stability. J. Power Sources, 2019, 412, 78–85. (39) Zhang, J.; Shi, Y.; Ding, Y.; Peng, L.; Zhang, W.; Yu, G. A Conductive Molecular Framework Derived Li2S/N,P-Codoped Carbon Cathode for Advanced Lithium–Sulfur Batteries. Adv. Energy Mater., 2017, 14, 1602876.


17


Page 18 of 20

(40) Yu, Y.; Zhu, M.; Liang, W.; Rhodes, S.; Fang, J. Synthesis of Silica–Titania Composite Aerogel Beads for the Removal of Rhodamine B in Water. RSC Adv., 2015, 5, 72437–72443. (41) Zu, G.; Shen, J.; Wang, W.; Zou, L.; Lian, Y.; Zhang, Z. Silica−Titania Composite Aerogel Photocatalysts by Chemical Liquid Deposition of Titania onto Nanoporous Silica Scaffolds. ACS Appl. Mater. Interfaces, 2015, 7, 5400–5409. (42) Shin, M. S.; Lee, T. W.; Park, J. B.; Lim, S. H.; Lee, S. M. Post-annealing Effects on the Electrochemical Performance of a Si/TiSi2 Heteronanostructured Anode Material Prepared by Mechanical Alloying. J. Power Sources, 2017, 344, 152–159. (43) Kaneko, Y.; Nagumo, M. Intermediate Phase in Synthesis of TiSi2 by Mechanical Alloying and Annealing. Mater. Sci. Eng., 2004, 375, 825–828. (44) Chen, Q.; Zhu, R.; Liu, S.; Wu, D.; Fu, H.; Zhu, J.; He, H. Self-Templating Synthesis of Silicon Nanorods from Natural Sepiolite for High-Performance Lithium-Ion Battery Anodes. J. Mater. Chem. A, 2018, 6, 6356–6362. (45) Kim, Y. M.; Ahn, J.; Yu, S. H.; Chung, D. Y.; Lee, K. J.; Lee, J. K.; Sung, Y. E. Titanium Silicide Coated Porous Silicon Nanospheres as Anode Materials for Lithium Ion Batteries. Electrochim. Acta, 2015, 151, 256–262. (46) Zhou, S.; Liu, X.; Wang, D. Si/TiSi2 Heteronanostructures as High Capacity Anode Material for Li Ion Batteries. Nano Lett., 2010, 10, 860–863. (47) Su, J.; Zhao, J.; Li, L.; Zhang, C.; Chen, C.; Huang, T.; Yu, A. Three-Dimensional Porous Si and SiO2 with In Situ Decorated Carbon Nanotubes As Anode Materials for Li-ion Batteries. ACS Appl. Mater. Interfaces, 2017, 9, 17808–17813. (48) Ren, Y.; Zhou, X.; Zhou, H.; Yang, J.; Chen, S.; Wu, L.; Nie, Y.; Wang, B. Zn-Assisted Magnesiothermic Reduction for the Preparation of Ultra-Fine Silicon Nanocrystals for Lithium Ion Batteries. Chem. Eng. J., 2017, 328, 691–696. (49) Tardif, S.; Paclenko, E.; Quazuguel, L.; Boniface, M.; Maréchal, M.; Micha, J. S.; Gonon, L.; Mareau, V.; Gebel, G.; Bayle-Guillemaud, P.; Rieutord, F.; Lyonnard, S. Operando Raman


18

Page 19 of 20 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


Spectroscopy and Synchrotron X-ray Diffraction of Lithiation/Delithiation in Silicon Nanoparticle Anodes. ACS Nano, 2017, 11, 11306–11316. (50) Schott, T.; Robert, R.; Benito, S. P.; Ulmann, P. A.; Lanz, P.; Zürcher, S.; Spahr, M. E.; Novák, P.; Trabesinger, S. Cycling Behavior of Silicon-Containing Graphite Electrodes, Part B: Effect of the Silicon Source. J. Phys. Chem. C, 2017, 121, 25718–25728.


19


Page 20 of 20

TOC Graphic


20

Double-Network Gel-Enabled Uniform Incorporation of Metallic

Recommend Documents