Deep Eutectic Solvent Binder Facilitating Reaction Kinetics of Lithium Sulfur Batteries

Existing binders fail to integrate all designed functionalities, including the polysulfide shuttle effect, sluggish kinetic transformation, electrode volume variation, slow Li⁺ transfer, and flammable characteristics. Herein, the microwave irradiation method is used to prepare deep eutectic solvent (DES) binder; with the rapid conduction and full utilization of energy, citric acid and betaine (CB) binder is formed in a flash. Intramolecular and intermolecular hydrogen bonds between C and B provide robust adhesion, self-healing capability, and flame-retardant properties. More importantly, Li⁺ flux is directly improved by hydrogen bond acceptor (B) of DES rather than introducing additional segments or chemical treatment; then the redox kinetics are significantly promoted and the polysulfide shuttle is further suppressed. The types and dynamics of the hydrogen bonds are observed via Raman and dynamic mechanical analysis, while effective LiPS adsorption capability is confirmed through theoretical calculations and in situ Raman measurements. Furthermore, rapid LiPS conversion is verified by nucleation/dissolution experiments of Li2S and distribution of relaxation times (DRTs) analysis, and nucleation transformation ratio (NTR) calculation shows the similar result. Benefiting from the superior merits of the DES binder, lithium-sulfur (Li─S) battery presents stable cycling at 5 C with 61.3% capacity retention after 300 cycles.