Cu 치환을 통한 Fe-Mn 기반 P2형 나트륨이온전지 양극재의구조 안정화 및 전기화학적 성능 개선

초록

Sodium-ion batteries (SIBs) have emerged as a promising alternative to lithium-ion batteries due tothe abundance and low cost of sodium resources. Among various cathode candidates, P2-type layered transitionmetal oxides have attracted considerable attention because of their high energy density and fast Na⁺ diffusionpathways. In this study, P2-type Na0.7Fe0.5Mn0.5O2 (pristine) and Cu-substituted Na0.7Fe0.4Mn0.5Cu0.1O2 (Fe-sitesubstitution) and Na0.7Fe0.5Mn0.4Cu0.1O2 (Mn-site substitution) were synthesized via a solid-state reaction toinvestigate the influence of Cu incorporation on electrochemical performance. Structural analyses using X-raydiffraction confirmed that all samples retained the P2 layered phase without impurity formation, while Cu substitutionslightly modified lattice parameters, implying changes in local electronic environments. Electrochemicaltesting demonstrated that Cu doping enhanced structural stability during cycling and improved Na⁺diffusion kinetics. Especially, Fe-site Cu substitution exhibited higher discharge capacity and better capacityretention compared to the pristine material, attributed to suppressed phase transition and more reversible redox activity. Moreover, impedance and rate-capability analyses indicated reduced charge-transfer resistance andfaster ion transport. These results suggest that partial Cu substitution effectively stabilizes the Fe/Mn redoxcouple and tunes Na⁺ occupancy, leading to improved electrochemical stability. This study provides valuableinsights into the design of Fe-Mn-based P2 layered oxides for high-performance and durable sodium-ion batteries.

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