Self-Healing SA@Borax Binder for In Situ Tuning of the Solid Electrolyte Interfaces for Silicon Anodes

Silicon is a promising anode material for next-generation lithium-ion batteries due to its high specific capacity of 4200 mAh g^–1, environmental friendliness, and wide availability. However, its significant volume expansion during lithiation/delithiation cycles leads to issues such as material crushing, electrical isolation, delamination, and unstable solid electrolyte interface (SEI) film formation, ultimately degrading the electrochemical performance and reducing the cycle life. This study focuses on developing a sodium alginate and borax composite (SA@Borax) binder for silicon-based anodes. Sodium alginate (SA) provides deformability and self-healing properties through chain sliding and hydrogen bond recombination, while the incorporation of boron–oxygen bonds forms a robust three-dimensional network. This network enhances mechanical stability, accommodates the volume changes of silicon nanoparticles, and maintains electrode integrity during cycling. Furthermore, the SA@Borax binder efficiently regulates the SEI film composition, promoting beneficial components that stabilize the SEI film and improve the lithium-ion diffusion rates. Electrochemical tests demonstrate that the Si anode with SA@Borax binder maintains a discharge specific capacity of 1655.80 mAh g^–1 after 500 cycles at a current density of 0.5 A g^–1, showcasing excellent long-term cycle stability. This research presents a viable strategy for developing high-performance binders for the next generation of lithium-ion batteries.