Na+/vacancy disordered manganese-based oxide cathode with ultralow strain enabled by tuning charge distribution

Abstract

Layered manganese-based oxide cathodes have attracted extensive attention in sodium-ion batteries (SIBs) due to their low cost and high volumetric energy density. However, Na⁺/vacancy ordering destabilizes the host structure and retards Na⁺ diffusion. Herein, we report that this issue can be solved by introducing the highly electropositive Sn⁴⁺ to tune charge distribution and then reduce electron delocalization as well as in-plane Na⁺–Na⁺ electrostatic repulsions. The disordered Na vacancy arrangement and suppressed P′2 ↔ P2 phase transition enable P′2-Na_0.67Mn_0.95Sn_0.05O₂ with fast Na⁺ migration and ultralow strain (<1%) during cycles. Thus, high reversible capacity of 131.2 mA h g⁻¹ and coulombic efficiency of 99.77% are achieved at 50 mA g⁻¹ after 200 cycles. Besides, based on a low reaction energy barrier, the electrode exhibits high Na-storage activity in a wide temperature range of −20 to 70 °C. These observations provide an effective strategy for designing high-performance cathode materials in rechargeable SIBs and beyond.