Stress Regulation through Precursor Chemistry: From Synthesis to Cycling Stability in O3‐Type Layered Oxide Cathodes

Abstract

ABSTRACT Layered oxide cathode materials have broad application prospects in sodium‐ion batteries. However, conventional oxide solid‐state synthesis route, transition metal oxides slowly participate in the reaction step by step, causing residual stress accumulation and cycling degradation. Herein, a synthesis strategy utilizing low‐melting‐point metal salt precursors is proposed. Leveraging their synchronous decomposition and liquid‐like characteristics, a uniform chemical environment is generated, fundamentally suppressing the uneven accumulation of residual stress. Thermal analysis and kinetic calculations demonstrated that the reaction activation energy of the metal salt system (NFM‐A) was significantly reduced and exhibited a more stable variation profile. This effectively circumvented the asynchronous reaction process caused by diffusion kinetic differences inherent to the traditional oxide route (NFM‐O). Multiple experimental characterizations consistently confirmed that the residual stress of NFM‐A was low and uniformly distributed. After prolonged cycling, NFM‐A maintained a uniform lattice strain distribution with complete and dense particle morphology, while continuous stress concentration, interlayer slip, and particle cracking occurred in NFM‐O. Combined with in situ XRD and finite element simulations, the critical role of the initial stress distribution in maintaining structural integrity during electrochemical cycling is revealed. This establishes stress regulation as a key criterion for designing layered oxide cathode materials with high structural stability.