Tunable Electrochemistry via Controlling Lattice Water in Layered Oxides of Sodium-Ion Batteries.

Layered oxides based on abundant elements have been extensively studied as cathodes of sodium-ion batteries. Among them, birnessite-type sodium manganese oxide containing lattice water meets the low-cost and high-performance requirement for stationary batteries. Herein, we for the first time present the controllable states of lattice water via adjusting the cutoff voltages, effectively enhancing the reversible capacity, cycling stability, and rate ability of the materials. The current investigation not only highlights the significance of intercalated lattice water for reversible Na (de)insertion of birnessite as well as other similar compounds, but also opens up new opportunities for advanced cathode materials for sodium storage.