Boosted H⁺ Intercalation Enables Ultrahigh Rate Performance of the δ-MnO₂ Cathode for Aqueous Zinc Batteries

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.