Asymmetric ionogel electrolyte with an ultrathin metal–organic framework layer for lithium dendrite inhibition in solid-state lithium-metal batteries

Solid-state electrolytes (SSEs) are used to prevent internal short circuits caused by the growth of lithium dendrites in solid-state lithium-metal batteries (SSLMBs). Ionogel electrolytes are new polymeric SSEs with outstanding processability, excellent flexibility, and superior ionic conductivity. Lithium-ion transport in ionogel electrolytes depends on ionic liquid (IL) content; however, increasing the IL content improves ionic conductivity but sharply decreases mechanical properties, thus limiting the ability to resist lithium dendrites. Thus, ionogel electrolytes must strike a balance between ionic conductivity and mechanical properties. Herein, we adopt a new strategy to suppress the growth of lithium dendrites by in situ polymerizing an ultrathin metal–organic framework (MOF) layer (9.8 μm) onto a highly ionic conductive ionogel electrolyte. The ionogel electrolyte provides an asymmetric SSE (ASSE) with a remarkable ionic conductivity of 4.8 × 10−4 S cm−1 (30 °C), whereas the ultrathin MOF layer regulates uniform dissolution/deposition of lithium and inhibits lithium dendrite growth, thereby increasing critical current density of the ASSE to 0.65 mA cm−2. An SSLMB assembled with the ASSE and LiFePO4 exhibits excellent performance and cycling stability, maintaining a specific capacity of 125.4 mAh g−1 after 500 cycles at 0.3C.