Ultrafast lattice engineering for high energy density and high-rate sodium-ion layered oxide cathodes

Abstract

Sodium-ion batteries attract significant interest for large-scale energy storage owing to abundant sodium reserves, while challenges remain in the high synthesis energy consumption, long synthesis period, and poor electrochemical performance of sodium-ion layered oxide materials. This study presents a general high-temperature thermal shock (HTS) strategy to synthesize and optimize sodium-ion layered oxides. The rapid ramping, sintering, and cooling processes minimize volatile sodium loss during HTS, facilitating the improvement of phase purity and effectively optimizing the microstructure of materials in a non-equilibrium state. As a proof of concept, Mn-based Na_0.67MnO₂ treated with HTS (NMOHTS) suppresses Mn ion vacancy within transition material layers, thereby increasing the redox centers and lowering the Mn 3d orbital energy level. Besides, the formation of transition metal layer stacking faults mitigates the structural transformation and Na⁺-vacancies ordering arrangement during cycling. Consequently, the energy density of the NMOHTS increases by 21.5 % to 559 Wh kg^-1, with an outstanding rate capability of 108 mAh g^-1 at 10C and an impressive capacity retention of 93.7 % after 300 cycles at 1C. In addition, we demonstrate the universality of HTS in synthesizing various other sodium-ion layered oxides, including nickel-based and iron-based cathodes, as well as in activating degraded materials.