Xylitol-Maleic Anhydride as Small-Molecule Binders for Silicon Anodes in Lithium-Ion Batteries

Abstract

The theoretical capacity (∼4200 mAh g−1) of silicon (Si) electrode is almost tenfold higher than that of commercially available graphite. However, the cycle-life performance of the Si electrode is poor. Herein, small molecules, sugar alcohol (xylitol) and maleic anhydride, are used as an aqueous binder to obtain high-performance Si electrodes. The xylitol-maleic anhydride (X-MA) binder is in situ polymerized by esterification of maleic anhydride with xylitol and oxa-Michael addition of an α,β-unsaturated ester with hydroxyl groups of xylitol during the preparation of slurry and the drying of electrode. The X-MA binder is characterized by Fourier-transform infrared and solid-state 13C nuclear magnetic resonance spectroscopy, confirming that the esterification and oxa-Michael addition reactions occur during the fabrication of Si electrodes. The results of thermogravimetric analysis and differential scanning calorimetry show that X-MA has good thermal stability and is an elastomer. The 180° peeling test results indicate that the presence of hydroxyl groups in the xylitol moiety results in a strong interaction between the binder and Si nanoparticles, improving the mechanical properties of the Si electrode. Furthermore, the Si electrode with the X-MA binder exhibits a high energy capacity of 4012 mAh g−1 at 0.1 C, enhanced C-rate performance, and good cycle-life performance.