NaCu_0.2Fe_0.3Mn_0.5O₂ (NCFM) cathode material was synthesized using a simple solid-state reaction, and the effect of calcination temperature on its interlayer spacing and oxygen vacancies concentration was investigated. Through electrochemical testing and material characterizations, higher calcination temperatures increase the electrostatic repulsion between oxygen atoms in adjacent layers, resulting in an expansion of Na layer spacing. This structural change enhances the diffusion kinetics of Na⁺, thereby significantly improving the rate performance of NCFM. Furthermore, elevated calcination temperatures facilitate the reduction of oxygen vacancies, leading to improved crystallinity. This enhancement in crystallinity mitigates structural strain during phase transitions, contributing to improved cyclic stability. Consequently, the optimized NCFM shows an initial discharge specific capacity of 143.3 mA·h/g at 0.1C, with a capacity retention rate of 79.28% after 100 cycles at 1C.