PEO-SA-NaTFSI-Based Binder with Enhanced Adhesion, Fast Ion Transport, and Robust Solid-Electrolyte Interphase for Sn Anodes Enabling High-Performance Sodium-Ion Batteries.

Sodium-ion batteries (SIBs) are promising for large-scale energy storage due to their high cost-effectiveness and safety. Alloy anodes exhibit significantly higher specific capacities compared to those of carbonaceous anode materials, holding great promise for enhancing the energy density of SIBs. However, their practical application is severely hindered by substantial volume expansion, sluggish reaction kinetics, and continuous fracture reformation of the solid-electrolyte interphase (SEI). Here, a multifunctional composite binder system was designed for the Sn anode, which was composed of poly(ethylene oxide) (PEO), sodium alginate (SA), and sodium bis(trifluoromethylsulfonyl)imide (NaTFSI). The PEO-SA-NaTFSI (PSN) binder integrates ternary synergistic functions: robust adhesion between the active material and current collector, enhanced Na transport kinetics, and formation of a stable NaF-rich SEI. Therefore, the Sn-PSN anode achieves an outstanding sodium storage performance with a high capacity of 583.4 mA h g at a current density of 10 A g and 77% capacity retention after 1500 cycles. In addition, the Sn-PSN||NaV(PO) full battery can maintain 81% capacity after 200 cycles with an electrode energy density of 169.0 W h kg. This work provides a multifunctional binder design strategy with broad application prospects for high-performance anodes of SIBs.