Dynamic Cross-Linked Binder for Stabilizing MoS2 Anodes with Enhanced Sodium-Ion Storage Kinetics

Enhancing the durability of Molybdenum disulfide (MoS2) anodes in sodium-ion batteries (SIBs) requires not only structural optimization of active materials but also rational design of the binder system. In this work, a polymeric sodium alginate-graft-polyacrylamide binder modified with 5 wt % boric acid (SP/5Ba) is developed via graft copolymerization, introducing boric acid-mediated dynamic cross-linking and hydrogen-bond-assisted interactions into the polymer framework. This adaptable network structure enables effective stress dissipation during repeated sodiation/desodiation, thereby contributing to maintaining electrode integrity. Meanwhile, the incorporation of polar functional groups and reversible cross-linking sites facilitates Na+ transport and improves reaction kinetics. Benefiting from these features, the MoS2-SP/5Ba electrode delivers a high reversible discharge specific capacity of 438.4 mAh g-1 after 305 cycles at 0.5 A g-1 with a capacity retention of 98.3%, and maintains 288.1 mAh g-1 after 300 cycles at 1 A g-1. Stable rate capability is also achieved, with reversible discharge specific capacities of 286.1 mAh g-1 at 5 A g-1 and 208.8 mAh g-1 at 10 A g-1 over extended cycling. Compared with conventional SA and the grafted SP binders, the proposed system demonstrates improved electrochemical stability and kinetics. This study provides a practical strategy for binder engineering toward high-performance SIBs.