H+ intercalation, as a critical battery chemistry, enables electrodes’ high rate performance due to the fast diffusion kinetics of H+. In this work, more water molecules are introduced into δ-MnO2 by the protonation of δ-MnO2 with abundant oxygen vacancies. Benefiting from the structure with a close arrangement of water molecules in interlayers, the Grotthuss transport of proton is achieved in the energy storage of the δ-MnO2 cathode. As a result, the δ-MnO2 cathode exhibits an ultrahigh rate performance with a capacity of 368.1 mAh g–1 at 0.5 A g–1 and 83.4 mAh g–1 at 50 A g–1, which has a capacity retention of 73% after 1100 cycles at 10 A g–1. The study of the storage mechanism reveals that the Grotthuss intercalation of proton predominates the storage process, which empowers the cathode with high rate performance.

The MnO2 cathode has attracted extensive attention in aqueous zinc ion battery research due to its environmental benignity, low cost, and high capacity. However, sluggish kinetics of hydrated zinc ion and manganese dissolution lead to insufficient rate and cycle performances. In this study, a manganese phosphate nanolayer synthesized in situ on a MnO2 cathode can be transformed into a δ-MnO2 nanolayer interphase after activation upon cycling, endowing the interphase with abundant interlayer water. As a result, the δ-MnO2 nanolayer interphase with the function of H+ topochemistry significantly enhances H+ (de)insertion in the MnO2 cathode, which leads to a kinetics conversion from Zn2+-dominated (de)insertion to H+-dominated (de)insertion, thus endowing the MnO2 cathode with superior rate and cycle performances (85.9% capacity retention after 1000 cycles at 10 A g–1). This strategy can be highly scalable for other manganese-based cathodes and provides an insight for developing high-performance aqueous zinc ion batteries.

No abstract

The dissolution of active material in aqueous batteries can lead to a rapid deterioration in capacity, and the presence of free water can also accelerate the dissolution and trigger some side reactions that affect the service life of aqueous batteries. In this study, a MnWO4 cathode electrolyte interphase (CEI) layer is constructed on a δ-MnO2 cathode by cyclic voltammetry, which is effective in inhibiting the dissolution of Mn and improving the reaction kinetics. As a result, the CEI layer enables the δ-MnO2 cathode to produce a better cycling performance, with the capacity maintained at 98.2% (vs. activated capacity at 500 cycles) after 2000 cycles at 10 A g−1. In comparison, the capacity retention rate is merely 33.4% for pristine samples in the same state, indicating that this MnWO4 CEI layer constructed by using a simple and general electrochemical method can promote the development of MnO2 cathodes for aqueous zinc ion batteries.