Unlocking the Critical Role of Cations Doping in MnO 2 Cathode with Enhanced Reaction Kinetics for Aqueous Zinc Ion Batteries

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Abstract MnO 2 ‐based cathode aqueous rechargeable zinc‐ion batteries (ZIBs) have favorable sustainability characteristics and are considered potential candidates for low‐cost effective, high‐safety energy storage systems. Nevertheless, the development of them has been hampered by unstable electrode structures and ambiguous charge storage mechanisms. Herein, the role of doping Fe 3+ and Co 2+ into δ‐MnO 2 cathode materials (FMO, CMO) is comprehensively probed and the working mechanism of Zn//FMO, Zn//CMO batteries are studied using in situ and ex situ characterization, electrochemical analysis, and theoretical calculations. Metal cations can partially replace Mn to form M─O bonds and enhance the structural stability as well as redox activity of MnO 2 . It is found that Fe doping effectively modulates the interaction between Zn 2+ /H + and the MnO 2 structure and inhibits the formation of ZnMn 2 O 4 (ZMO) by‐products and Co doping confers the fast diffusion ability of Zn 2+ . The charge storage reactions of FMO and CMO are mainly via H + /Zn 2+ intercalation/deintercalation accompanied by OTF‐base‐like double hydroxide Zn x (OTF) y (OH) 2x‐y ‐nH 2 O (Z‐LDH) deposition/dissolution. This research enriches the fundamental comprehension of rechargeable ZIBs and reveals the way to modify electrodes for performance enhancement.

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