MnO2, a prominent manganese-based cathode material, has been used extensively in aqueous zinc-ion batteries (ZIBs). However, Zn2+ intercalation in MnO2 faces multiple obstacles, primarily due to the electrostatic interaction between Zn2+ and the skeleton, the coverage of by-product Zn4SO4 (OH)6·xH2O (ZSH) on the cathode, and the preferential occupation by H+ of the active sites. Here, we introduce MnOOH into K+-doped α-MnO2 (KMO) to produce an ultrahigh-capacity KMO-MnOOH cathode. The MnOOH can transform into the active material β-MnO2 via the in situ release of protons. The β-MnO2 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 Zn2+ transport kinetics. The released protons from MnOOH can reduce the by-products ZSH, facilitating rapid Zn2+ migration and deep Zn2+ 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+/Zn2+ intercalation for high-performance Zn//MnO2 batteries.
Zhao et al. (Mon,) studied this question.