Coordination shell complexing of superoxide anion for stable lithium air battery

Abstract

Superoxide anion is the most critical electrochemical intermediate in lithium air batteries, closely associated with the sluggish oxygen reduction/evolution reaction and undesired parasitic side reactions. Herein, a coordination shell complexing strategy is proposed to concurrently improve the solubility and stability of superoxide anions by adding SnCl₂ in a LiTFSI – DMSO electrolyte. That modifies the solvent sheath to facilitate incorporating superoxide anion into the primary coordination shells of metal cations to form stable complexes in electrolyte, as identified by electron spin resonance spectra in coupling with quantum chemical calculations. The formation of stable superoxide-related complexes boosts solution-phase growth of lithium peroxide and alleviate side products of singlet oxygen, dimethyl sulfone and Li₂CO₃, leading to super-high full discharge capacity of 96,013 mAhg^-1_carbon and long duration over 350 cycles. These findings could shed light on the acceleration of the development of advanced lithium air battery and other emergent technology involving oxygen chemistry.