Multi-functionalities of Natural Polysaccharide for the Next Generation Lithium-Ion Batteries

Abstract

In this study, environmentally friendly aqueous binder for high capacity anode materials and high performance silicon/hard carbon anode materials are successfully synthesized using natural polysaccharides. Aqueous binder using natural polysaccharides has excellent binding property as well as makes stable solid-electrolyte-interface layer on silicon particles so that the electrodes containing the aqueous binder can maintain stable cycle retention. Si-based anodes with this aqueous binder exhibit significantly improved electrochemical properties which show a high specific capacity (2010 mAh g-1) after 80 cycles. High performance silicon/hard carbon anode materials derived from natural polysaccharide show remarkable discharge/charge capability at a high current density. Nanocrystalline Si (c-Si) dispersed in amorphous Si (a-Si) encapsulating hard carbon (HC) has been synthesized as an anode material for fast chargeable lithium-ion batteries. The HC derived from natural polysaccharide was coated by thin a-Si layer through chemical vapor deposition (CVD) using silane (SiH4) as a precursor gas. The HC@c-Si@a-Si anodes showed excellent cycle retention of 97.8 % even after 200 cycles at a 1 C discharge/charge rate. Furthermore, high capacity retention of ~54 % of its initial reversible capacity at 0.2 C rate was obtained at a high discharge/charge rate of 5 C. Moreover, LiCoO2/HC@c-Si@a-Si full-cell showed excellent rate capability and very stable long-term cycle. Even at a rate of 10 C discharge/charge, the capacity retention of the LiCoO2/HC@c-Si@a-Si full-cell was 50.8% of its capacity at a rate of 1 C discharge/charge and showed superior cycle retention of 80 % after 160 cycles at a rate of 1 C discharge/charge.