Design and Optimization of 3DSi Electrode for Li-Ion Battery Applications
Lithium ion batteries are revolutionized today's information-rich e-society due to their light weight and high energy density. Despite their great success in portable electronic devices at the present time, interest is continued in advancing new and improved electrode materials for lithium ion batteries with higher energy capacity and longer cycle life. Silicon is one of the most promising anode materials for lithium batteries, as it appeals with highest theoretical specific capacity (4200 mAh/g) among known materials, relatively low cost, and environmental benignity. However, silicon anodes suffering from huge volume change associated with the insertion and extraction of lithium during charge-discharge process. Such an unavoidable volume changes result to cracking and pulverization of the anode, which leads to a loss of electrical contact and eventual fading of capacity upon cycling. Herein, we report a porous three-dimensional framework of current collectors to form 3DSi nanostructure to provide continuous electron transport network and accommodate the volume expansion of Si particles.
3D porous Ni current collectors are prepared by galvanostatic electrodeposition with tuning its experimental parameters such as deposition current and pH of bath solution etc. Silicon is deposited conformally by plasma enhanced chemical vapor deposition (PECVD) technique. During PECVD process, parameters such as time, flow rate of the silane gas (SiH4), pressure and power are optimized to ensure uniform conformal coating of Si to form desired three-dimensional silicon structure. X-ray diffraction and Microscopy analysis revealed the formation of 3DNi current collectors by electrodeposition and conformal coating of Si by PECVD. Electrochemical studies such as cyclic voltammetry, electrochemical impedance spectroscopy and charge-discharge studies have been carried out to understand the influence of 3D structure on silicon capacity and cycle life properties. Such a 3D Si electrodes exhibit capacity of 2600 mAh/g with an excellent columbic efficiency at 0.2 C rate for 100 cycles. Further, full cell configuration has been fabricated using LiFePO4/C cathode to demonstrate feasibility of presently designed 3D Si electrode for high capacity Li-ion battery applications.
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