Long‐Lasting Solid‐State Aluminum Battery with High‐Areal‐Capacity Enabled by In Situ Polymerization Strategy

Abstract Nonaqueous rechargeable aluminum batteries (RABs) attract intense interest due to their low‐cost, high‐capacity, and high‐safety using nonflammable chloroaluminate ionic liquid electrolytes (ILEs). However, Al dendrite growth, interface degradation, and corrosiveness remain challenges in these ILEs. Herein, an ultrastable solid‐state aluminum battery (SAB) based on a cross‐linked polymer solid‐state electrolyte (PSE) and a PSE‐encapsulated graphite (PG) cathode is constructed via an in situ polymerization strategy, which maintains battery safety and realizes a synergy of interface compatibility between PSE/PG and PSE/Al interfaces. The PSE has a high room temperature ionic conductivity of 4.15 × 10⁻³ S cm⁻¹ and a low corrosiveness to Al anode, ensuring rapid and continuous transportation of chloroaluminate ions and homogeneous plating/stripping of metallic Al. In addition, the volume expansion of the PG cathode is almost negligible owing to the confinement effect of graphite within the cross‐linked polymer skeleton. As a consequence, the assembled SAB demonstrates high areal capacity (0.67 mAh cm⁻² at 0.1 mA cm⁻²), good rate performance, and impressive cycling stability (no capacity attenuation after 10 000 cycles). Such in situ polymerization strategy shows a broader promise for the development of safe and stable RABs in energy storage applications.