Solvation‐Competing Nitrile Polymer Gel Electrolyte for High‐Voltage Quasi Solid State Lithium Metal Batteries

Abstract The search for Li‐ion batteries offering increased energy, power, and safety has led researchers to develop solid‐state Li batteries (ASSB) and more recently, quasi‐solid electrolytes (QSEs) prepared by in situ polymerization to accelerate their practical implementation. A complex challenge with QSEs arises in designing polymer matrices having high ionic conductivity that are stable against oxidation, safe and scalable. Herein, we developed a novel QSE through in situ polymerization of butyl acrylate monomer in adiponitrile (ADN)‐based electrolyte. Benefiting from a solvation‐competing mechanism, polybutyl acrylate (PBA) expels the nitrile solvent from the Li + solvation shell, which significantly inhibits side reactions between ADN and Li metal, thereby forming a robust solid electrolyte interface (SEI). The PBA in the QSE also contributes to an enhanced lithium‐ion transference number (tLi+ = 0.87) and minimized concentration polarization. As a result, the QSE‐based LCO||Li cell retains 78% of its capacity after 1000 cycles at 4.45 V, along with outstanding rate performance. The excellent performance and safety are also validated in a 250 Wh kg −1 pouch cell. This work provides new insights for the development of high‐energy‐density, safe, and practical quasi‐solid‐state pouch cells offering immediate promise to battery manufacturers.