Regulated Li+ Solvation via Competitive Coordination Mechanism of Organic Cations for High Voltage and Fast Charging Lithium Metal Batteries

Abstract

Li⁺ solvation exerted a decisive effect on electrolyte physicochemical properties. Suitable tuning for Li⁺ solvation enabled batteries to achieve unexpected performance. Here, we introduced inert organic cations to compete with Li⁺ for combining electrolyte molecules to modulate Li⁺ coordination in the electrolyte. The relevance between the number of cationic sites in organic cations and the competitive solvation ability was explored. The organic cations with multiple cationic sites attracted solvent molecules and anions away from Li⁺ to form new solvated shell, improving the Li⁺ transport kinetics and desolvation process in electrolyte while enhancing electrolyte oxidation tolerance. Moreover, electrostatic shielding provided by organic cations and anion-derived robust SEI promoted uniform and rapid Li⁺ deposition on Li electrodes. With the positive effect of organic cations, Li||LiCoO₂ (LCO) batteries showed high specific capacity (136.46 mAh g⁻¹) at high charge/discharge rate (10 C). Furthermore, Li||LCO batteries exhibited good capacity retention (70 % after 500 cycles) at 4.6 V charge cut-off voltage. This work provides fresh insights for the optimization of electrolytes and battery performance.