Monolithic Task‐Specific Ionogel Electrolyte Membrane Enables High‐Performance Solid‐State Lithium‐Metal Batteries in Wide Temperature Range

Abstract Monolithic ionogel electrolyte membranes (IGEMs) based on gelling scaffolds and ionic liquids have aroused intensive interest because of their broad processing compatibility, nonflammability, and favorable thermal and electrochemical features. However, the absence of functional scaffolds that concurrently enable high mechanical strength and Li + transportability of IGEMs constrains the battery power and safety. Herein, a task‐specific IGEM monolith featuring high Li + conductivity and outstanding thermal stability is demonstrated, whereby electrospun positively charged poly(ionic liquid) nanofibers serve as a thermotolerant scaffold for the IGEM. Regulating the Li + environment in the IGEM enables the shift from the sluggish vehicular to fast structural Li‐ion transport mode. With the unique IGEM, the solid‐state Li||LiFePO 4 cells achieve improved rate capability and good cyclability in a wide temperature range from 0 to 90 °C. Furthermore, practical solid‐state Li||LiFePO 4 pouch cells with a cathode capacity of ≈2 mAh cm −2 have also been demonstrated.