A layered-spinel heterostructure 0.5NaMnO2–0.5Li0.5Mn2O4 cathode for advanced lithium ion batteries

Abstract

Heterostructure NaMnO₂–Li_0.5Mn₂O₄ cathode materials were prepared by adjusting the molar ratio of sodium in the materials by a solid phase method. X-ray diffraction (XRD) analysis showed that the prepared samples were a layered-spinel heterostructure NaMnO₂–Li_0.5Mn₂O₄. The lattice fingerprint region of NaMnO₂–Li_0.5Mn₂O₄ was studied by electron microscopy, and the results showed the (111) plane of Li_0.5Mn₂O₄ and the (001) plane of NaMnO₂. The heterostructure 0.5NaMnO₂–0.5Li_0.5Mn₂O₄ exhibits superior high-rate capability and excellent cycling performance. The proposed heterostructure 0.5NaMnO₂–0.5Li_0.5Mn₂O₄ cathode is investigated by in situ XRD and impedance analysis. The rate of discharge of heterostructure 0.5NaMnO₂–0.5Li_0.5Mn₂O₄ was 108.8 mA h g⁻¹ at 500 mA g⁻¹. The initial discharge of 0.5NaMnO₂–0.5Li_0.5Mn₂O₄ was 61.69 mA h g⁻¹, and after 1000 cycles the discharge capacity remained 51.13 mA h g⁻¹ at a current of 2 A g⁻¹. The heterogeneous structure combines the advantages of high capacity of the layered structure NaMnO₂ and the structural stability of the spinel Li_0.5Mn₂O₄, which exert a synergistic effect and improve the electrochemical performance of the lithium-free layered NaMnO₂ cathode material.