A rechargeable Li–CO2 battery based on the preservation of dimethyl sulfoxide

Abstract

Tetraethylene glycol dimethyl ether (TEGDME) with low Li-ion conductivity is widely used as an electrolyte in Li–CO₂ batteries because of its high boiling point and low evaporation loss in an open environment. Meanwhile, dimethyl sulfoxide (DMSO) with five-fold higher Li-ion conductivity has been widely used as an electrolyte in Li–CO₂ batteries, with the drawback of lasting depletion via evaporation and side reactions. In this work, high-concentration LiTFSI (DMSO) is used as an electrolyte and a polytetrafluoroethylene (PTFE) membrane is inserted between the open cathode cap and cathode, with Ni foam used as a bifunctional current collector to achieve stable 600-cycle cycling at high current densities of 2 and 4 A g⁻¹, which is a record for Li–CO₂ batteries to the best of our knowledge. In detail, the effects of the solvated Li-ion size on discharge voltage, the effects of Ni-coordinated Li₂C₂O₄ on the charge voltage, the effects of CO₂–TFSI⁻ interactions on the discharge reaction route, and the effects of PTFE and the electrolyte on the evaporation of free DMSO molecules are systematically studied via spectroscopic, electrochemical, and computational characterization techniques.