Electrochemical Performance of Graphite-Silicon Alloy Composite Anodes Using Cross-Linked Poly(vinyl alcohol) Binder for Lithium-Ion Batteries

Abstract

The growing demand for rechargeable batteries requires a great improvement in the energy density of current lithium-ion batteries. In order to increase the energy density of lithium-ion batteries, silicon anode materials have been actively studied, because they exhibit a high theoretical capacity, a low reduction potential, are environmentally benign and are low cost.1 However, they suffer from substantial volume changes during cycling, which are highly detrimental to the cycling stability of lithium-ion batteries. The mechanical stresses caused by repeated volume changes can fracture the electrode, which results in poor electrical contacts between the active materials, electronic conductors and current collector. To solve these problems, many studies have been carried out by different approaches such as controlling the particle size and morphology, alloying with inert metals, embedding silicon in a conductive material, and applying several functional binders. In order to obtain the silicon-based composite anodes with high capacity and good cycling stability, we synthesized silicon alloy that was composed of silicon nanoparticles embedded in Al-Fe-Ti-Ni matrix phases. Using these silicon alloy material, we prepared the composite electrodes composed of graphite powder and silicon alloy particles. In these composite anodes, poly(vinyl alcohol) (PVA)s with different degree of cross-linking were employed as polymer binders. The effect of degree of cross-linking on interfacial adhesion and cycling performance of the composite electrodes was investigated to identify optimum processing condition. A systematic study demonstrated that the appropriate cross-linking of PVA made the electrodes mechanically strong and remarkably improved the cycling stability of the electrodes.