Electrochemical Performance Of Si Research Articles

Design Strategies of Si/C Composite Anode for Lithium-Ion Batteries.

Silicon-based materials that have higher theoretical specific capacity than other conventional anodes, such as carbon materials, Li2 TiO3 materials and Sn-based materials, become a hot topic in research of lithium-ion battery (LIB). However, the low conductivity and large volume expansion of silicon-based materials hinders the commercialization of silicon-based materials. Until recent years, these issues are alleviated by the combination of carbon-based materials. In this review, the preparation of Si/C materials by different synthetic methods in the past decade is reviewed along with their respective advantages and disadvantages. In addition, Si/C materials formed by silicon and different carbon-based materials is summarized, where the influences of carbons on the electrochemical performance of silicon are emphasized. Lastly, future research direction in the material design and optimization of Si/C materials is proposed to fill the current gap in the development of efficient Si/C anode for LIBs.

Sputtered titanium nitride films on nanowires Si substrate as pseudocapacitive electrode for supercapacitors

Titanium nitride (TiN) is widely used in electrode materials in fast charging/discharging supercapacitors (SCs) due to its outstanding conductivity. However, the low capacitance of the TiN electrode limits its further application in the SCs. Therefore, the reasonable design of the TiN electrode with high electrochemical and mechanical properties is still a challenge. In this paper, the silicon nanowires/titanium nitride electrode (Si NWs/TiN) is prepared by depositing TiN onto the etched Si nanowires by direct current magnetron sputtering. The Si NWs are prepared by etching silicon in 4.8 M HF/0.02 M AgNO3 aqueous solution for different times (5 min, 15 min, 30 min, 60 min). The mechanism of the effect of etched silicon substrate morphology on the electrochemical performance of Si NWs/TiN electrode was studied. As the etching time increases, the differences of the TiN surface structure, lattice defects and surface chemical composition will change the capacitance performance and charge storage mechanism of the Si NWs/TiN electrode. The prepared Si30 NWs/TiN electrode exhibits an outstanding specific capacitance as high as 113.55 F g−1 at a scan rate of 5 mV s−1 with 0.5 M H2SO4 solution as electrolyte. The specific capacitance of the Si30 NWs/TiN electrode is as high as 7.5 times that of the electrode without etching at 100 mV s−1. The Si30 NWs/TiN electrode has an excellent cyclic stability performance, which the electrode has a decay rate of 12.4% after 2000 cycles. This indicates that the electrode has reliable stability. The electrode of the supercapacitor prepared by this method can open up a new way to expand the specific surface area of other transition metal nitride.

Boosting Lithium-Ion Transport Kinetics by Increasing the Local Lithium-Ion Concentration Gradient in Composite Anodes of Lithium-Ion Batteries.

Constructing composite electrodes is considered to be a feasible way to realize high-specific-capacity Li-ion batteries. The core-double-shell-structured Si@C@TiO2 would be an ideal design for such batteries, considering that carbon (C) can buffer the volume change and TiO2 can constrain the structural deformation of Si. Although the electrochemical performance of the shells themselves is relatively clear, the complexity of the multishell heterointerface always results in an ambiguous understanding about the influence of the heterointerface on the electrochemical properties of the core material. In this work, a multilayer film model that can simplify and simultaneously expand the area of the heterointerface is used to study the heterointerfacial behavior. First, a multilayer film TiO2/C with different numbers of TiO2/C heterointerfaces is studied. It shows that the electrochemical performance is enhanced apparently by increasing the number of TiO2/C heterointerfaces. On the one hand, the TiO2/C heterointerface exhibits a strong lithium-ion storage capacity. On the other hand, the TiO2/C heterointerface appears to effectively promote the local Li-ion concentration gradient and thus boost the Li-ion transport kinetics. Then, TiO2/C is combined with Si to construct a composite anode Si/C/TiO2. An obvious advantage of TiO2/C over single TiO2 and C is observed. The utilization rate of Si is greatly improved in the first cycle and reaches up to 98% in Si/C/TiO2. The results suggest that the electrochemical performance of Si can be greatly manipulated by the heterointerface between the multishells.

TiO2 shielded Si nano-composite anode for high energy Li-ion batteries: The morphological and structural study of electrodes after charge-discharge process

Many efforts are being done to commercialize silicon (Si) as a high energy application anode for Li-ion batteries. However, still improvements are required at various levels from structural modification to fabrication process for commercializing Si as single anode material. In the present study, we report high improvement in the electrochemical performance of Si by shielding its surface with nano TiO2 particles. A layer of TiO2 nano particles is deposited on the surface of carbon coated nano Si by hydrothermal process to prevent the volume expansion during charge-discharge process. The sample is designated as Si/C–TiO2. The composite shows discharge capacity of 781 mAh g−1 after 200 cycles which was much higher than the capacity of pristine Si (23 mAh g−1) and carbon coated Si (Si/C) (215 mAh g−1) after 200 cycles. The Si/C–TiO2 composite has also shown higher capacity at all current rates from 100 mA g−1 to 2 A g−1 and a stable cycle life up to 200 cycles. The work also provides the morphological and structural study of electrodes after charge-discharge cycles conducted by field emission scanning electron microscopy, X-ray diffraction and X-ray photon spectroscopy techniques.

Synthesis of porous Si/C by pyrolyzing toluene as anode in lithium-ion batteries with excellent lithium storage performance

Silicon (Si) has attracted researchers’ attention because of the high theoretical capacity of 4200 mAh g−1. However, the electrochemical performance of Si is often worsened by the structure deterioration originated from the huge volume variation during charge/discharge process. To improve the electrochemical performance, the porous structure is initially fabricated in Si by removing aluminum from Si-Al alloy powder with HCl solution, and then a carbon layer coats on the surface of porous Si by pyrolyzing toluene at 700 °C under nitrogen atmosphere, forming porous Si/C composite. In this composite, carbon helps greatly to transfer electrons and stabilize the structure of Si, resulting in an enhanced charge/discharge performance in comparison with porous Si. Porous Si/C presents an enhanced Li-storage performance; at 200 mA g−1, porous Si/C can deliver 1402 mAh g−1 after 100 charge/discharge cycles, but only 585.3 mAh g−1 for porous Si; and at 3200 mA g−1, the reversible specific capacity of Si/C is 505.1 mA h g−1, while that for porous Si is 41.7 mAh g−1.

Nanostructured silicon spheres prepared by a controllable magnesiothermic reduction as anode for lithium ion batteries

In this work, nanostructured, monodisperse Si spheres have been prepared by a facile, controllable magnesiothermic reduction method using monodisperse SiO2 spheres as the precursor. The reaction conditions for magnesiothermic reduction have been optimized, yielding desired product and byproduct. Carbon coating on Si nanocrystals is performed by an easy chemical vapor deposition (CVD) method. The effect of carbon coating on electrochemical performance of Si is investigated. The results show that the original monodisperse spheric morphology of SiO2 can be preserved during magnesiothermic reduction and the cycling stability of Si can be enhanced by carbon coating. This work provides a facile, scalable method to synthesize nanostructured Si and Si/C composites.

Effect of Interface between Si Thin Film Anode and Current Collector Substrate on the Electrochemical Performance of Si

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Effect of Interface between Si Thin Film Anode and Current Collector on the Electrochemical Performance of Si

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Carbon-Coated Si as a Lithium-Ion Battery Anode Material

Carbon-coated Si has been prepared by a thermal vapor decomposition method. Its electrochemical performance has been investigated by charge/discharge tests, cyclic voltammetric experiments, differential scanning calorimetry, and -nuclear magnetic resonance, etc. This kind of material demonstrates good electrochemical performance as an anode material for lithium-ion batteries. The improvement in the electrochemical performance of Si is mainly attributed to the effect of carbon coating. © 2002 The Electrochemical Society. All rights reserved.