Low-Strain Reticular Sodium Manganese Oxide as an Ultrastable Cathode for Sodium-Ion Batteries

Sodium-ion batteries (SIBs) are recognized as attractive alternatives for grid-scale electrochemical energy storage applications. Transition metal oxide cathodes represent one of the most dynamic materials for industrialization among the various cathodes for SIBs. Here, a cation-doped cathode Na_0.44Mn_0.89Ti_0.11O₂ with a tunnel structure is introduced, which undergoes a lowered volume change of only 5.26% during the Na⁺ insertion/extraction process. Moreover, the average Na⁺ diffusion coefficients are enhanced by more than 3-fold upon the doping of the Ti cation. The obtained cathode delivers a practically usable capacity of 119 mAh g^-1 at 0.1 C as well as an enhanced discharge capacity of 96 mAh g^-1 at 5 C. Durability is demonstrated by the retained 71 mAh g^-1 after 1000 cycles, corresponding to a capacity retention of 74%. This work demonstrates that the reticular Na_0.44Mn_0.89Ti_0.11O₂ is a promising ultrastable cathode material for the development of long-life sodium-ion batteries.