Anion-cation coupled electrolyte additive enhancing the performance of lithium-oxygen batteries

Abstract

The rational design of electrolyte via introducing additive is an efficient strategy to improve the electrochemical performance of lithium-oxygen batteries (LOBs). In this work, coupling LiCl and Sn(TFSI)₂ as the anion-cation electrolyte additive achieved the high-performance of LOBs by promoting the oxygen electrode reactions, regulating the Li⁺ solvation structure, and inducing the growth of the SEI protective layer. Specifically, Cl⁻ with strong coordination affinity to Li⁺ could weaken the binding between Li⁺ and TEGDME solvent molecules, leading to the formation of an anion-dominant Li⁺ solvation structure, which facilitates the diffusion of Li⁺ in the electrolyte bulk and electrolyte/electrode interface. On the other hand, Sn²⁺ can serve as a redox mediator to catalyze ORR on the cathode and participate in the growth of smooth and dense SEI protective layer on Li metal anode surface, thus effectively promoting the oxygen electrode reaction kinetics and suppressing the corrosion of Li anode. As a consequence, the LOBs with coupled LiCl and Sn(TFSI)₂ additive exhibited a ultra-high discharge capacity of 21517.1 mA h g⁻¹ and an excellent cycling life of 334 cycles. This work provides a deep understanding for designing efficient electrolyte with additive for LOBs.