Sustainable Binder System: Cross-Linked Tamarind Gum-Polyacrylic Acid for Silicon-Graphite Anodes in Future Lithium-Ion Batteries

Silicon (Si), with high theoretical specific capacity, the most promising anode material to replace graphite in lithium-ion battery (LIB) systems, is studied. The large volume changes during cycling cause cracking, fragmentation of Si, and electrical isolation of the Si active material from the current collector. The combined use of Si and graphite (Si-Gr) provides the best option to achieve high energy densities in commercial LIB systems. The different physical and chemical surface properties of silicon and graphite necessitate designing a binder capable of restraining volume changes. The present study focuses on the effectiveness of crosslinking naturally abundant and water-soluble tamarind gum (TG) with polyacrylic acid (PAA) as binder. Crosslinking of TG and PAA, confirmed by FTIR, has aided an optimum balance between the binding strength, swelling, and better electrode integrity during the cycling than PAA-based anodes. It exhibits an initial specific capacity of 872 mAh/g and coulombic efficiency of 70%. The capacity retention is ≈60% at the end of 900 cycles. The crosslinked TG-PAA binder facilitates Li⁺ transportation there by maintaining rate capability in the anode. The results provide a promising avenue for pursuing environment-friendly processing of high-capacity LIBs with an extended cycle life using crosslinked biopolymer as binder.