Cross‐Linked Sodium Alginate as A Multifunctional Binder to Achieve High‐Rate and Long‐Cycle Stability for Sodium‐Ion Batteries

Sodium-ion batteries (SIBs) hold great promise owing to the naturally abundant sodium resource and high safety. The research focus of SIBs is usually directed toward electrode materials, while the binder as an important component is rarely investigated. Herein, a cross-linked sodium alginate (SA)/graphene oxide (GO) binder is judiciously designed to serve as a robust artificial interphase on the surface of both anode and cathode of SIBs. Benefiting from the cross-linking continuous network structure as well as the highly hydrophilic nature, the SA-GO binder possesses a large tensile strength of 197.7 Mpa and a high ionic conductivity of 0.136 mS cm-1 , superior to pure SA (93.8 Mpa, 0.025 mS cm-1 ). Moreover, the structural design of SA-GO binder exhibits a strong binding ability to guarantee structural integrity during cycling. To demonstrate its effectiveness, polyanion-type phosphates (e.g., Na3 (VO)2 (PO4 )2 F) and chalcogenides (e.g., MoS2 , VS2 ) are adopted as cathode and anode materials of SIBs, respectively. As compared to traditional binders (e.g., PVDF, SA), electrodes with the SA-GO binder exhibits significantly increased rate capability and cycling stability, such as Na3 (VO)2 (PO4 )2 F (40 C fast-charge, 84% capacity retention after 1000 cycles). This work highlights the role of novel aqueous-based binders in developing next-generation sodium-storage devices.