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

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_xMnO₂) 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 MnO₂ 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 Zn₅₀Al₅₀ alloy anode in 2 m Al(OTf)₃ aqueous electrolyte, the BQ-Al_xMnO₂ exhibits superior rate capability and cycling stability. At 1 A g^-1, the specific capacity of BQ-Al_xMnO₂ 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_xMnO₂ without BQ co-incorporation.