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

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.