Effect of Heat Treatment on Si Electrodes Using Polyvinylidene Fluoride Binder

Abstract

The electrochemical performance of Si electrodes using polyvinylidene fluoride (PVDF) binder heated at different temperatures ranging from 150°C to 350°C was investigated. Compared to unheated electrodes that have no capacity after the first formation cycle, the heat treated electrodes show an increasingly improved cycling performance as the heating temperature increases from 150°C to 300°C. In particular, Si electrodes heated at 300°C retain a specific capacity of about 600 mAh/g for 50 cycles with a lower cutoff potential of 0.170 V vs Li/Li+. The reasons for such improvements are considered based on results from thermal analysis, optical microscopy and adhesion tests. It is suggested that heat treatment improves the binder distribution, the adhesion to the Si particles and to the substrate, thereby leading to a better cycling performance. 2Introduction The ever-increasing demand for energy density has driven lithium ion battery researchers to new generation electrode materials with high energy density. One of the approaches is to replace the conventional carbonaceous negative electrode material by a