Design of localized high-concentration electrolytes: dual-anion assisted construction of high-energy-density lithium-metal batteries with wide temperature range

Abstract

The development of high energy density lithium batteries and their use under extreme temperatures present significant challenges for commercial carbonate-based electrolytes. This study reports a local high-concentration electrolyte based on ethyl acetate (EA)/fluoroethylene carbonate (FEC), with lithium difluoro(oxalato)borate (LiDFOB) as the primary lithium salt. By adjusting the lithium salt concentration and adding lithium difluorophosphate (LiPO₂F₂) to regulate the solvation structure of lithium ions, the desolvation process of Li⁺ is accelerated, resulting in a well-formed electrode/electrolyte interface. The formulated electrolyte enables the Li/Lithium Cobalt Oxide (LCO) battery to stably cycle at a high cutoff voltage of 4.5 V. After 800 cycles at a rate of 1C, the capacity retention is 81.2 %. Even under high-rate cycling at 10C, the initial capacity can be maintained at around 85.0 %.Additionally, it exhibits good conductivity at low temperatures, with batteries using this electrolyte demonstrating excellent low-temperature performance even at −40 °C. At a rate of 0.1C, it provides an initial capacity of 173 mAh g⁻¹, with a capacity retention of 94.2 % after 200 cycles. This work enables high-voltage, fast-charging, and low-temperature capabilities in lithium batteries through optimized electrolyte formulation and artificial construction of solid electrolyte interfaces, presenting innovative strategies for electrolyte design across multi-scenario applications.