Water-based polyimide binders with dual functional groups for enhanced electrochemical performance of silicon anodes

Abstract

Silicon-based anodes are promising materials for next-generation lithium-ion batteries due to their high theoretical capacity. However, their practical application is hindered by drastic volume expansion during cycling, which leads to particle fracture, capacity fading, and instability of the electrode structure. In addition, most conventional binders require toxic organic solvents, raising environmental and safety concerns. To address these issues, a water-based polyimide binder with high mechanical robustness was synthesized through an aqueous process by combining 3,5-diaminobenzoic acid (DABA) and 4,7,10-trioxa-1,13-tridecanediamine (TTDDA) in different ratios. The –COOH groups in DABA enhanced adhesion and structural stability, while the –O– linkages in TTDDA improved flexibility and Li+ transport. Among the synthesized binders, D8T2-PI exhibited the best balance between mechanical strength and elasticity, achieving superior cycling performance and higher capacity compared with conventional PAA and CMC binders. The flexible polymer network improved electrode–electrolyte interfacial contact and facilitated Li+ diffusion, thereby enhancing electrochemical performance. These results demonstrate that a sustainable, water-processable polyimide binder can effectively enhance both the mechanical and electrochemical stability of silicon anodes, providing a practical and design strategy for high-performance lithium-ion batteries.