Gel electrolyte with dimethyl sulfoxide confined in a polymer matrix for Li-air batteries operable at sub-zero temperature

Abstract

The instability of the electrolyte and insufficient ionic conductivity are considered the main problems that adversely affect applications of Li-air batteries (LABs) at sub-zero temperatures. In this study, a polymer-confined gel (PCG) electrolyte suitable for low-temperature LABs is developed by confining high donor number dimethyl sulfoxide (DMSO) within an in situ polymerized 4,4′-bis(stearoylamino)diphenyl ether (BSDE) matrix. The strong hydrogen bonds between the BSDE framework and DMSO molecules has destroyed the frozen structure of DMSO, thus the ionic conductivity at lower temperature has thus been improved. Furthermore, a local high-concentration electrolyte is constructed using DMSO as a solvent to dissolve the Li salt. The ionic conductivity of PCG in the fabricated electrolyte at −20 °C is maintained at 0.15 mS cm−1, which is 5.5 times higher than the corresponding liquid DMSO electrolyte. As a result, the LABs equipped with PCG display a long cycle life of 450 h (−20 °C) and 760 h (25 °C), whereas the LABs with a liquid DMSO electrolyte fail at −20 °C and can only operate for 40 h at 25 °C. This study provides a feasible but facile strategy for the design of gel electrolytes suitable for low-temperature LABs, and this strategy can be extended to other energy-storage systems.