Microstructures and electrochemical properties of rapidly solidified Si-Cu-X alloys as anode for Li-ion batteries

H.J. Kwon, J-J Song, S.M. Bae, K.Y. Sohn, W-W Park
Inje University, KR

Keywords: Si/Cu alloy, silicon anode, melt spinning, lithium-ion battery

Summary:

Silicon anodes in Li-ion secondary batteries have received attention because of their high capacity. However, Si shows a drastic volume expansion/contraction during Li+ insertion/extraction, which leads to stress that broke the weak ionic bond of silicon, resulting in cracking of electrode. This causes fracturing of the lithium and loosing electrical contact between Si particles and current collector. One method to resolve this problem is to refine the microstructure of anode materials, which can be achieved by taking advantage of rapid solidification process. The other approach is to form buffering matrix phases to suppress and accommodate the large volume changes of the active host materials. It can alleviate the stress by absorbing the lattice stress during the cycle. Among the buffer materials, Cu is a possible candidate to support the silicon particles. Firstly, Cu element can enhance the elasticity and the electrical conductivity of anode electrode by compensating Si element. Secondly, the high thermal conductivity of cupper can increase the cooling rate of molten alloys in that the heat can be easily released during the rapid solidification process. It restrains the growth of silicon, thus lattice stress during the cycle is reduced. The objective of this work is to investigate the effect of relative volume fraction of Cu-based matrix to silicon and the effect of Ti, Ni addition on the microstructures and electrochemical behavior in rapidly solidified Si-Cu base anode alloys.