In Situ Fabricated Quasi-Solid Polymer Electrolyte for High-Energy-Density Lithium Metal Battery Capable of Subzero Operation

Solid-state batteries (SSBs) are an emerging technology for safe and high-energy-density electrochemical energy storage. Unfortunately, SSBs suffer from inadequate ionic conductivity and sluggish interfacial transport at subzero temperatures, which limit their widespread application. Herein, a flexible, stable, and highly conductive quasi-solid polymer electrolyte (QSPE) for SSBs is developed that allows low-temperature (LT) operation. The in situ polymerized QSPE has an integrated battery structure, outstanding ionic conductivity (e.g., 1.0 mS cm −1 at −30 °C), and exhibits favorable compatibility with Li metal (>2000 h in Li|QSPE|Li). Li|QSPE|LiFePO 4 and high-voltage Li|QSPE|LiNi 0.8 Mn 0.1 Co 0.1 O 2 batteries demonstrate excellent long-term stability (>2000 cycles at room temperature) and can operate effectively at LT (e.g., −30 °C). Furthermore, pouch cells with a LiNi 0.8 Mn 0.1 Co 0.1 O 2 (14.5 mg cm −2 ) cathode show flexibility, safety, and high capacity. The high performance of this QSPE is ascribed to its unique multilayer solvation structure that provides fast Li + transport and excellent interfacial stability. Thus, the newly developed electrolyte chemistry enables practical high-voltage, LT solid-state Li batteries.