Ion Pre-Embedding Engineering of δ-MnO₂ for Chemically Self-Charging Aqueous Zinc Ions Batteries

Aqueous zinc ion batteries (ZIBs), especially those with self-charging properties, have been promisingly developed in recent years. Yet, most inorganic materials feature high redox potential, which limit their development in the self-charging field. To achieve this target, by pre-embedding potassium ions into δ-MnO₂ to reduce the energy barrier in oxygen adsorption, the first application of MnO₂ in self-charging ZIBs is realized. The design features a facile two-electrode configuration with no excessively complex component to allow for energy storage and conversion. Due to the voltage difference between the oxygen in the air and the discharge products, a redox reaction can be carried out spontaneously to realize the self-charging process. After the chemical self-charging process, the Zn-K_0.37 MnO₂ ·0.54H₂ O/C cell achieves an open circuit voltage of around 1.42 V and a discharge capacity of 201 mAh g^-1 , reflecting the promising self-charging capability. Besides, the chemically self-charging ZIBs operate well in multiple modes of constant current charge/discharge/chemical charging. And decent cycling capability can also be achieved at extreme temperatures and high mass loading. This work promotes the development of ZIBs and further broadens the application of inorganic metal oxides in the self-charging systems.