A Gradient-Distributed Binder with High Energy Dissipation for Stable Silicon Anode

Abstract

Silicon is considered as a promising alternative to traditional graphite anode for lithium-ion batteries. Due to the dramatic volume expansion of silicon anode generated from the insertion of Li+ ions, the binder with the ability to suppress the severe volume changes and repeated massive stress impact during cycling are strongly required. Herein, we design a gradient-distributed two-component binder (GE-PAA) to achieve excellent cyclic stability, revealing the mechanism of high energy dissipative binder stabilizing silicon electrodes. The inner layer of the electrode is a polyacrylic acid polymer (PAA) with high Young's modulus, which is used as skeleton binder to stabilize the silicon particle interface and electrode structure. The outer layer is a gel electrolyte polymer (GE) with lower Young's modulus, which effectively releases the stress generated during lithiation and de-lithiation processes, achieving high structural stability at the molecular level and silicon particles. Due to the synergistic effect of the gradient binder design, the silicon electrode still retains a reversible capacity of 1557.4 mAh g-1 after 200 cycles at a current density of 0.5 C and 1539.2 mAh g-1 at a high rate of 1.8 C. This work provides a novel binder design strategy of the Si anode toward achieving long-cycling stability.

Keywords: binder, Si anode, gradient distribution, energy dissipation, Lithium-ion battery