Design and development of a high-performance epoxidized polyvinyl alcohol/chitosan dual cross-linked composite binder for the effective suppression of Si anode volume expansion

Silicon (Si) is a promising anode material for next-generation high-energy-density lithium-ion batteries (LIBs), but its practical use is limited by the severe volume expansion (>300 %) during lithiation/delithiation. To address this, we developed a dual-crosslinked binder using epoxidized polyvinyl alcohol (EPVA) and chitosan (CTS), where EPVA acted as the soft segment and CTS as the rigid segment. By optimizing their mass ratio, the EC55 binder (EPVA: CTS = 5: 5) was achieved, exhibiting high tensile strength (46.65 MPa) and the highest crosslinking density (1.77 × 10 −3  mol cm −3 ). This structure provided reversible elasticity, evenly distributing the stress from Si's volumetric changes and preserving electrode integrity. Consequently, the EC55@Si half-cell, with a Si: binder: Super P ratio of 6: 2: 2, retained 2008.4 mAh g −1 specific capacity after 300 cycles at 1000 mA g −1 . This study also explored the effect of binder content on the electrochemical performance of Si anodes, offering insights into the design of high-performance Si-based LIB binders for future applications.