ETPTA polymer network confined amide-based eutectic electrolyte for safe and long- life lithium metal battery

Serious safety issues and uncontrollable lithium dendrites hinder the commercial application of high-voltage lithium metal batteries (LMBs) that employ carbonate-based electrolytes. Herein, we propose a eutectogel electrolyte, an amide-based eutectic electrolyte consisting of lithium bis (trifluoromethyl sulfonyl) imide (LiTFSI) and N-methyl-2,2,2-trifluoroacetamide (3F-NMA) confined by trimethylolpropane ethoxylate triacrylate (ETPTA) polymer network. Compared with the carbonate-based electrolyte, the non-flammable eutectogel electrolyte facilitates the formation of LiF/Li_xN-rich solid electrolyte interfaces, therefore expands the electrochemical window, enhances the interfacial compatibility, and improves the cycling stability of LMB. Besides, it shows a high lithium-ion transference number of 0.63 and a stable long-term lithium stripping/plating (>2300 h) in a Li||Li symmetric cell, at a current density of 0.2 mA cm⁻². Additionally, the Li||LiFePO₄ full cell with eutectogel electrolyte exhibits a commendable cycling stability, achieving a capacity retention of 77.4 % after 1000 cycles at 5 C (30 °C) and maintaining 82 % capacity following 400 cycles at 1 C (60 °C). When used as the electrolyte in Li||LiCoO₂ full cell, it renders the battery appealing performance including a notable initial discharge capacity of 170.3 mAh g⁻¹ and a retained capacity of 86.3 % after 300 cycles, at a high charge voltage of 4.45 V. This research may provide insight into the design of eutectogel electrolytes for high-performance lithium metal batteries.