Benzoquinone‐Lubricated Intercalation in Manganese Oxide for High‐Capacity and High‐Rate Aqueous Aluminum‐Ion Battery

Abstract Aqueous aluminum‐ion batteries are attractive post‐lithium battery technologies for large‐scale energy storage in virtue of abundant and low‐cost Al metal anode offering ultrahigh capacity via a three‐electron redox reaction. However, state‐of‐the‐art cathode materials are of low practical capacity, poor rate capability, and inadequate cycle life, substantially impeding their practical use. Here layered manganese oxide that is pre‐intercalated with benzoquinone‐coordinated aluminum ions (BQ‐Al x MnO 2 ) as a high‐performance cathode material of rechargeable aqueous aluminum‐ion batteries is reported. The coordination of benzoquinone with aluminum ions not only extends interlayer spacing of layered MnO 2 framework but reduces the effective charge of trivalent aluminum ions to diminish their electrostatic interactions, substantially boosting intercalation/deintercalation kinetics of guest aluminum ions and improving structural reversibility and stability. When coupled with Zn 50 Al 50 alloy anode in 2 m Al(OTf) 3 aqueous electrolyte, the BQ‐Al x MnO 2 exhibits superior rate capability and cycling stability. At 1 A g −1 , the specific capacity of BQ‐Al x MnO 2 reaches ≈300 mAh g −1 and retains ≈90% of the initial value for more than 800 cycles, along with the Coulombic efficiency of as high as ≈99%, outperforming the Al x MnO 2 without BQ co‐incorporation.