Moisture-Resistant, Expansive, and Disordered Interlayer Microenvironment-Enabled Robust Sodium Oxide Cathodes

Layered transition metal oxides are some of the most attractive cathode candidates for sodium-ion batteries (SIBs). The main challenge of achieving superior storage performance is to simultaneously boost the ion diffusion kinetics and restrain the undesirable OP4 phase transition upon long-term cycling. In this report, a step-by-step molecule-ion exchange approach is presented to design the high air-stability disordered Ca_0.065Na_0.55MnO_2.05 (CNMO-1) cathode functionalized with an expansive and disordered interlayer microenvironment. Theoretical and experimental investigations revealed that water mediation and ion exchange enhance ion diffusion, while Ca ions stabilize the alkali metal layer, preventing phase transition and manganese (Mn) migration during high-voltage cycling. It exhibits a high specific capacity of 135.4 mA h g^-1 at 0.2 A g^-1. Beyond that, it can also deliver 81.3 mA h g^-1 at the harsh condition of 5 A g^-1 with a high 93.3% retention even after 2000 cycles, surpassing most previous achievements. This proposed strategy can be extended to other K⁺, Zn²⁺, and La³⁺ cases, showing an innovative method for designing robust cathodes that enhance the performance of SIBs.