Fig. 2: DMF-based electrolytes with enhanced battery kinetics and interfacial instability in Li-CO₂ batteries.

All electrolytes contain 1 M LiFSI salt, all the tests were performed at room temperature. a Viscosity of TEGDME, DMSO, and DMF solvents. b Ionic conductivity of various electrolytes (1 M LiFSI/solvent). c Structures and binding energies of Li⁺-TEGDME, Li⁺-DMSO, and Li⁺-DMF. Color scheme of molecules: Li, green; C, light blue; O, red; S, yellow; N, navy; H, white. d Long-term voltage-time profiles at 0.1 A g⁻¹ with a cut-off specific capacity of 500 mA h g⁻¹. Two insets show the cycling profiles of the DMF cell during the first 10 cycles and the last 4 cycles, respectively. The DMF cell suddenly failed at the 73rd cycle. e Comparison of battery overpotential based on the cycling performance. f Rate performance at various current densities from 0.1 to 2 A g^–1. g Ex-situ FTIR spectra observed on the fresh positive electrode before cycling and the positive electrode discharged and recharged in the DMF cell. The discharge product Li₂CO₃ is marked by blue shading. The side products (HCO₂Li/CH₃CO₂Li), marked with red asterisk (*), result from the irreversible side reaction between DMF and the intermediate CO₂²⁻ radicals during discharge. The detailed reaction mechanism is illustrated in figure h. h The mechanism for side reactions between DMF and CO₂²⁻ during discharge¹⁹.