L-Cysteine Cross-Linked Sodium Alginate as a Binder with Strong Binding Force on Copper Foils To Enhance Sodium Storage Performance

Molybdenum disulfide (MoS2) is a promising anode material for sodium-ion batteries (SIBs) due to its large layer spacing and high theoretical specific capacity. However, its electrochemical performance is hampered by large volume changes and poor ion diffusivity. Herein, a new water-based binder, sodium alginate-L-cysteine (SA-LCy), with a three-dimensional (3D) network cross-linked structure is prepared, which can effectively encapsulate the MoS2 anode materials to mitigate their pulverization. Meanwhile, the CuxS anchor, resulting from the reaction of the SA-LCy binder and the copper foil, can further enhance the binding force between electrode materials and copper foils. Owing to the advantages of the SA-LCy binder, the electrochemical performance of the MoS2 anode is significantly improved. The specific capacity of 370.8 mAh g–1 can be achieved at 0.2 A g–1 after 220 cycles, corresponding to a capacity retention of 95%. Moreover, a high reversible specific capacity of 345.3 mAh g–1 can be obtained at 10 A g–1. As for the MoS2//Na3V2(PO4)3/C-PVDF full cell, the specific capacity of 80.9 mAh g–1 can still be maintained at 0.5 A g–1 after 50 cycles. Hence, we confirm that SA-LCy is a promising binder for high-performance SIBs.