Stable Quasi‐Solid‐State Aluminum Batteries

Abstract Nonaqueous rechargeable aluminum batteries (RABs) of low cost and high safety are promising for next‐generation energy storage. With the presence of ionic liquid (IL) electrolytes, their high moisture sensitivity and poor stability would lead to critical issues in liquid RABs, including undesirable gas production, irreversible activity loss, and an unstable electrode interface, undermining the operation stability. To address such issues, herein, a stable quasi‐solid‐state electrolyte is developed via encapsulating a small amount of an IL into a metal–organic framework, which not only protects the IL from moisture, but creates sufficient ionic transport network between the active materials and the electrolyte. Owing to the generated stable states at both positive‐electrode–electrolyte and negative‐electrode–electrolyte interfaces, the as‐assembled quasi‐solid‐state Al–graphite batteries deliver specific capacity of ≈75 mA h g⁻¹ (with positive electrode material loading ≈9 mg cm⁻², much higher than that in the conventional liquid systems). The batteries present a long‐term cycling stability beyond 2000 cycles, with great stability even upon exposure to air within 2 h and under flame combustion tests. Such technology opens a new platform of designing highly safe rechargeable Al batteries for stable energy storage.