Design of Cross‐linked Polymer Deep Eutectic Electrolytes for High‐voltage Long‐Cycle Lithium Metal Batteries via Solvation Regulation of Polymerizable Deep Eutectic Solvent Monomers

ABSTRACT Traditional polymer deep eutectic electrolytes (PDEEs) have been limited in their widespread application in lithium metal batteries (LMBs) due to issues such as high‐voltage stability and interfacial side reactions. Here, N‐(2‐Hydroxyethyl) acrylamide (HEAA) as a hydrogen bond donor, into deep eutectic solvent (DES) composed of succinonitrile (SN) and lithium bis (trifluoroethane sulfonyl) imide (LiTFSI) to obtain polymerizable deep eutectic solvent (PDES) monomer. The hydrogen bonding between the monomer (─OH/─NH─) and TFSI − further induces LiTFSI dissociation. More importantly, PDEE constructed from PDES monomers based on a unique solvation structure improves interfacial compatibility with electrodes. Furthermore, experiments confirmed that using ethoxylated trimethylolpropane triacrylate (ETPTA) as crosslinking agent to enhance polymer network crosslinking density improves the stable operation of the electrolyte under high voltage. The Poly(PDES)‐CL electrolyte (ETPTA abbreviated as CL) exhibits high ionic conductivity (σ = 1.65 mS cm −1 ), high safety (non‐flammable), broad electrochemical stability (5.3 V vs. Li/Li + ), and a high Li + migration number ( t Li+ = 0.66). Li||Poly(PDES)‐CL‐3||LiFePO 4 (LFP) cell maintained over 90.0% capacity retention after 2000 cycles at 2 C and 5 C. Li||Poly(PDES)‐CL‐3||LiCoO 2 (LCO) batteries achieved 84.3% capacity retention after 300 cycles at 0.5 C under high voltage (4.6 V). This novel PDEE paves the way for LMB applications.