High-voltage dilute ether electrolytes enabled by regulating interfacial structure

Abstract

Poor oxidation stability of ether solvents at the cathode restricts the use of dilute ether electrolytes with conventional concentrations around 1 M in high-voltage lithium metal batteries. Here we develop an anion-adsorption approach to altering the ether solvent environment within the electrical double layer (EDL) at the cathode, by adding a small amount of nitrate, so that the oxidation tolerance of nitrate-containing dilute ether electrolytes is enhanced up to 4.4 V (versus Li/Li+), leading to complete compatibility with high-voltage cathodes and exhibiting superior cycling stability. Constant-potential molecular dynamics simulations reveal that ether molecules are mostly excluded from the cathode because of nitrate occupation in the inner layer of the EDL, thus suppressing ether oxidative decomposition. This work highlights that regulating the interfacial structure by adding surface adsorbates, rather than passivating cathode-electrolyte interphase or changing ion solvation, can help to enhance the oxidation stability of ether solvents. It also provides design criteria for adsorption-type additives to achieve high-voltage dilute ether electrolytes.