Constructing Localized-Anion Gel-Electrolyte with Poly(Ethyl Acrylate/Acrylic Acid Lithium) for Flame-Retardant Lithium Metal Batteries

Abstract

The existing electrolytes suffer from the uncontrolled Li+ deposition, flammability, and limited ionic conductivity problems. The gel-electrolyte are a core technology for the lithium metal batteries as they offer diverse tools for constructing unique solvent structure and suppress the uncontrolled growth of lithium dendrites. Here, a localized-anion gel-electrolyte with poly(ethyl acrylate/acrylic acid lithium) is reported to achieve a dendrite-free lithium deposition with the stable solid-electrolyte interphase. The flame-retardant triethyl phosphate are engaged in gel-electrolyte as a plasticizer with a solution casting method, which improves the safety of Li metal batteries. The TFSI- is localized by anionphilic -COOLi in the vicinity of polymers, which maintains the uniform lithium flux and suppresses the deposition to achieve the smooth lithium growth. The lithiophilic -COOR group homogenized the Li+ flow at the electrode/electrolyte interface and alleviated the local lithium-ion flow. The LFP//Li cells assembled with the gel-electrolyte can still maintain a coulombic efficiency of 99% and capacity retention of 96% after 320 cycles at 1 C. And the NCM811//Li cells assembled with the gel-electrolyte can maintain about 90% coulombic efficiency and 88% capacity retention after 120 cycles at 0.5 C. In summary, this work provides an effective strategy for the application of next-generation high-safety lithium metal batteries.

Keywords: Poly(ethyl acrylate/acrylic acid lithium), localized-anion, solvation cluster, flame retardant, gel-electrolyte