(Invited) Si Materials for Li-ion Battery Negative Electrode Applications

Abstract

Silicon is an attractive candidate for lithium-ion batteries negative electrode materials because it delivers 10 times greater theoretical (~4200 mAh/g) specific capacity than that of traditional graphite anode (~370 mAh/g). However, the widespread application of silicon materials has remained to be a significant challenge, originating from large volume changes during lithium insertion and extraction processes and excessive surface reaction with electrolyte. This large volume change causes cracking and pulverization of silicon, leading to loss of the electrical contact in the electrode. The Si volume change coupled with excessive electrolyte surface reaction, leads to drastic capacity fading. To address the large volume change, new electrode fabrication approaches have been developed such as nano-Si materials assembly and new binder development. New functional binders with electronic conductivity, adhesive functional groups, and crosslinking functional groups are the recent research focuses. To address the excessive surface reactions of Si with electrolyte, electrolyte additives of different chemistry has been developed and tested. Fluorocarbon additives such as FEC have demonstrated as an effective SEI formation additive for Si materials. Electrolyte additives for Si materials has been a very active area of research. Electrolyte additives with due functionalities have attract major interest lately. Si particle coatings such carbon coating as an electric conductive medium and electrolyte insulating buffering layer have been widely used to encapsulate the silicon particles and prevent electrolyte reaction. There are many different carbon precursors for performing the carbon coating, which produce carbon coatings with different chemical and morphological carbon coatings. The Si materials with highly graphitized and dense coating is able to not only deliver higher gravimetric capacity and stable cycling compared to that of the Si with disordered carbon coating, but also alter the Si materials bulk transformation. A comprehensive discussion of the Si materials coating, electrode design and electrolyte additives and its electrochemical performance will be presented.