Carboxymethyl Three-Dimensional Cross-Linked Biopolymer Binder for High-Performance Silicon Anodes in Lithium-Ion Batteries

Abstract

Dramatic volume changes of silicon anode materials lead to the pulverization and shedding of active materials, which hinders their further practical application. Silicon binders can greatly relieve the volumetric expansion issue and improve the cycle life. Herein, a natural three-dimensional cross-linked biopolymer gum, Sa-son seed gum (SG), is modified by carboxymethylation and applied to silicon anodes as a binder to implement long-term stable cycling. The modified Sa-son seed gum (CMSG) provides a strong interfacial binding force with silicon particles to adapt to the volume change due to their rich carboxyl and hydroxyl groups. Meanwhile, the introduction of the carboxymethyl group of the binder increases the water solubility resulting in a feasible process for a uniform electrode. The CMSG binder exhibits high mechanical strength and long-lasting interfacial adhesivity to stabilize the electrode integrity of silicon anodes. The Si@CMSG electrode shows a high initial Coulombic efficiency (ICE) of 89.67% and a reversible capacity of 2060 mAh/g after 240 cycles at a current density of 0.84 A/g. Furthermore, electrochemical impedance spectroscopy (EIS) indicates that the CMSG binder can effectively reduce interfacial impedance, increase the ion diffusion rate, and reduce electrode polarization.