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Nanostructured Silicon as potential anode material for Li-ion batteries

The success of Li-ion batteries in the early 1960s took years of research and contribution of many scientists and engineers. Since then there are several electronic revolutions and still lithium-ion (Li-ion) cells are the most widely used as rechargeable battery system for portable electronic devices and electrical vehicles. It has many advantages like high energy density, long storage life, small volume, light weight, low self-discharge efficiency and non-memory effect. The most widely used anode is graphite whose lithiated compounds have stable phases up to the LiC6 stoichiometry corresponding to a theoretical specific capacity of 372 mAh / g[1]. In contrast, silicon possesses a very high theoretical capacity of 4200 mAh / g and can intercalate 4.4 Li into Si at high temperature to form Li15Si4[2]. Silicon also features a working potential around 0.4 V vs. Li+/Li which is safer than operating potential of graphite (0.05 V vs. Li+/Li). Although silicon possesses all of these advantages, silicon based anodes suffer from huge volume expansion upon cycling (≈400%) causing electrode fracture and electrical isolation during repeated cycling [3]. Continuous volume changes cause the breaking-reformation of the solid electrolyte interphase (SEI) film which leads to consumption of lithium-ions and electrolyte. Exhaustion of the electrolyte causes the degradation of conductivity and induces fast capacity loss. The porous structure can provide lithium-ion transport from electrolyte to silicon. The commercial micrometer silicon (Si) powder, ball-milled Si powder, and silicon nanowires generated by metal-assisted chemical etching method were investigated as a potential anode materials for Li-ion batteries.

silicon ; ball-milling ; chemical etching ; porosity ; anode ; battery ; electrochemical performance

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