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

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.