Regulating the weak solvation structure in electrolyte for high-rate Li-metal batteries at low temperature

Abstract

The rate performance of lithium metal batteries (LMBs) is greatly reduced at low temperature (LT), which is mainly caused by the sluggish Li⁺ transport kinetics. To address these issues, a weak solvation electrolyte with enhanced Li⁺ de-solvation and uniform Li deposition is designed by introducing the soft solvent isoxazole (IZ). IZ could significantly improve the ionic conductivity of the electrolyte at LT. And its small dipole moment also facilitates the acceleration of Li⁺ de-solvation. Moreover, the electrolyte with a weak solvation structure exhibits uniform Li deposition and a LiF-rich solid-electrolyte interphase (SEI), which is conducive to Li⁺ through the SEI. Consequently, the optimal electrolyte significantly improves cycle life and C-rate performance of NCM811‖Li cells at −40 °C, showing high specific capacity (118.4 mA h g⁻¹) and high capacity retention (96.5%) after 70 cycles at 2C. Moreover, the corresponding pouch battery displays high energy density (302.6 W h kg⁻¹) at −30 °C. The synergistic regulation of weak solvation electrolyte enables fast ion transport and a stable interface, probably providing a promising direction for high-rate and stable LMBs at LT.