An electrochemically transformed multifunctional binder network simultaneously strengthens the interphase stability and mechanical integrity of silicon anodes

Silicon (Si) is a promising alternative anode material for lithium-ion batteries due to its ultra-high theoretical capacity and suitable voltage platform. However, its practical application is limited by the rapid capacity fading caused by the instability of the solid electrolyte interphase (SEI) film, the collapse of Si particle structure and the mechanical failure of Si electrodes. Herein, we develop a multifunctional composite binder (denoted as PS) composed of multi-hydroxyl polyvinyl alcohol (PVA) and electroactive squaric acid (SA). The complete binder network derived from the efficient crosslinking reactions between SA and PVA chains, as well as the beneficial electrochemical synergistic decomposition reactions between SA and fluoroethylene carbonate additive, can effectively stabilize the macro- and micro-structures of Si electrodes, induce the beneficial decomposition components of electrolytes to build a robust SEI film, and promote the Li+ transport rate. Based on these beneficial effects, the optimized PS61-based Si anode exhibits higher initial coulombic efficiency (89.8 %), much improved rate performance (2041.5 mAh g−1 at 10 C), and better cycling stability (1582.1 mAh g−1 after 400 cycles) than that of the PVA-based Si anode. Furthermore, the NCM523//Si (PS61) full cell achieved a high reversible capacity of 140.8 mAh g−1 after 300 cycles, demonstrating the positive function of PS binder on promoting the practical application of Si anodes.