A polyarylimide covalent organic frameworks anode with ultralong discharge platform boosts high energy density Rocking-Chair Zn ion batteries

Traditional Zn metal anode in aqueous Zn ion batteries (AZIBs) involved the reversible plating/stripping of Zn2+ suffers from dendrite growth, hydrogen evolution reaction (HER), and surface corrosion. Developing organic anode to pair with cathode material is an effective strategy to avoid above challenges. However, the organic anode that hosts the reversible Zn2+ storage has been restrained by low energy density (-30-60 Wh kg-1) and unstable operated voltage. Herein, for the first time, we report a new polyarylimide covalent organic framework (HKCO-DANT-COF) as organic anode with rich redox active centers, well-ordered pore channels, and extraordinary structural stability, that delivers a considerable specific capacity (256 mAh g-1 at 0.1 A g-1), high-rate performance (147 mAh g-1 even at 10 A g-1) and long cycling stability (over 16,000 cycles). Impressively, 94.4 % of capacity is contributed from its ultralong discharged plateau. The in/ex-situ characterizations and theory calculation are employed to reveal Zn2+/H+ co-storage behavior and stable discharge configuration. More importantly, the rocking-chair AZIBs assembled by HKCO-DANT-COF anode and MnO2 cathode deliver a superior energy density of 93.8 Wh kg-1 (based on the total active mass of cathode and anode), which is better than the most reported rocking-chair AZIBs.