Manganese‐Based Proton Reservoir Trigger Proton Diversion Effect for Ultrahigh‐Capacity Aqueous Zinc‐Ion Batteries

Abstract

ABSTRACT MnO 2 , a prominent manganese‐based cathode material, has been used extensively in aqueous zinc‐ion batteries (ZIBs). However, Zn 2+ intercalation in MnO 2 faces multiple obstacles, primarily due to the electrostatic interaction between Zn 2+ and the skeleton, the coverage of by‐product Zn 4 SO 4 (OH) 6 ·xH 2 O (ZSH) on the cathode, and the preferential occupation by H + of the active sites. Here, we introduce MnOOH into K + ‐doped α‐MnO 2 (KMO) to produce an ultrahigh‐capacity KMO‐MnOOH cathode. The MnOOH can transform into the active material β‐MnO 2 via the in situ release of protons. The β‐MnO 2 with the 1 * 1 tunnel structure shows the strong adsorption for H + and unique tunnels that allow for rapid migration of H + , resulting in the diversion of protons originally intercalated into KMO. This “proton diversion effect” leads to sufficient active sites in KMO that accelerate Zn 2+ transport kinetics. The released protons from MnOOH can reduce the by‐products ZSH, facilitating rapid Zn 2+ migration and deep Zn 2+ intercalation. Accordingly, the KMO‐MnOOH cathode exhibits an ultrahigh specific capacity (645.6 mA h g −1 at 0.3 A g −1 ) and an excellent cycling stability (239.3 mA h g −1 at 2 A g −1 after 950 cycles). This work provides new insights into the regulation of H + /Zn 2+ intercalation for high‐performance Zn//MnO 2 batteries.