Borate-enhanced CMC binder for silicon anodes in lithium-ion batteries

Silicon is recognized as the most promising anode material for lithium ion batteries (LIBs) due to its high theoretical specific capacity (4200 mAh g −1 ). However, the significant volume expansion of Si during cycling restricts its practical application in LIBs. The binder is critical in mitigating the volume expansion stress of Si. This study discusses a new binder, CMC-SB, synthesized by linking sodium tetraborate (SB) with carboxymethyl cellulose sodium (CMC) via borate ester bonds, which enhances the flexibility of the binder. After being folded and subjected to a 200-g load, the CMC-SB film remains intact without breakage, indicating superior flexibility compared to CMC. When used as a binder for Si anodes, CMC-SB significantly improves battery stability during long-term cycling.