Dextran Sulfate Sodium as Multifunctional Aqueous Binder Stabilizes Spinel LiMn2O4 for Lithium Ion Batteries

Spinel LiMn2O4 (LMO) has several beneficial properties for utilization as a cathode material for lithium-ion batteries, including a high operating voltage, thermal stability, low cost, and eco-friendliness. However, its application is limited by capacity fading due to structural transformation and manganese dissolution upon cycling. A method is proposed to resolve these two issues, using dextran sulfate sodium (DSS) as an aqueous binder to coat the LMO surface. DSS stabilizes the surface/interface structure of LMO by incorporating Na into the interstitial 16c sites, creating a uniform surface coating layer and promoting the formation of a homogeneous and stable cathode-electrolyte interphase derived from the sulfate groups in DSS and enriched with LiF/LiSOxF. The aqueous DSS binder effectively suppresses the surface degradation and Mn dissolution of spinel LMO. The LMO electrode based on DSS exhibits superior cycling stability and rate performance compared with those of electrodes using the conventional poly(vinylidene difluoride) binder. These findings demonstrate the potential value of DSS as a multifunctional aqueous binder in stabilizing spinel LMO for lithium-ion batteries.