Constructing the Non‐Flammable Anion Acceptor‐Containing Deep Eutectics‐Based Gel Polymer Electrolyte for High‐Performance Li‐Metal Batteries

Abstract Polymer electrolytes have attracted wide attention for Li metal batteries (LMBs) due to their good interfacial compatibility and facile preparation, but the low ionic conductivity, poor Li + transport efficiency and insufficient safety still inhibit their further application. Herein, a non‐flammable anion acceptor‐containing deep eutectic‐based gel polymer electrolyte (NFAA‐DGPE) is prepared by in situ polymerization of poly(ethylene glycol) diacrylate (PEGDA) in the presence of trimethyl phosphate (TMP) and allylboronic acid pinacol ester (AAPE) additives. TMP coupled with deep eutectic ensures superior non‐flammability of NFAA‐DGPE, while deep eutectic‐based PEGDA matrix provides high oxidation resistance (>5.25 V) and sufficient ion‐transport pathways. Additionally, synergistic effect between AAPE and DEE realizes excellent ionic conductivity of 3.22 mS cm −1 and high Li⁺ transference number of 0.79 in NFAA‐DGPE by promoting Li‐salt dissociation and anchoring the anions. NFAA‐DGPE‐based symmetric batteries exhibit superior stability, maintaining a voltage hysteresis of only ≈70 mV for 7300 h at 0.1 mA cm −2 . Therefore, Li|NFAA‐DGPE|LiFePO 4 batteries deliver stable cycling over 1000 cycles with 86% capacity retention. Moreover, Li|NFAA‐DGPE|LiNi 0.8 Mn 0.1 Co 0.1 O 2 cells retain 84% of their initial capacity after 300 cycles and exhibit stable cycling performance even under a wide voltage window (2.7–4.5 V) or a high cathode mass loading of ≈15 mg cm −2 .