Preparation and electrochemical performance of LiNi0.5Mn1.5O4 spinels with different particle sizes and surface orientations as cathode materials for lithium-ion battery

Abstract

LiNi0.5Mn1.5O4 hierarchical microspheres composed of primary particles with different sizes and surface orientations are synthesized by high-temperature calcination based on different Ni–Mn oxides pre-sintered at different temperatures. The effects of pre-sintering temperature on the microstructure, morphology, and electrochemical properties of materials are investigated. The results show that pre-sintering temperature has a significant effect on the composition of Ni–Mn oxides, whereas all LiNi0.5Mn1.5O4 products have phase-pure spinel structure. SEM shows that pre-sintering temperature exerts a great influence on the primary particles’ size and surface orientations. With pre-sintering temperature increasing, primary particle size increases gradually, and particle morphology changes from octahedron with {111} surface to truncated polyhedron with extra {100} and/or {110} surfaces. Electrochemical properties are investigated in LiNi0.5Mn1.5O4/Li half-cell and LiNi0.5Mn1.5O4/Li4Ti5O12 full-cell. It is found that the particle size and surface orientation have great influence on the electrochemical performance of LiNi0.5Mn1.5O4. Among them, the LiNi0.5Mn1.5O4 sample synthesized with Ni–Mn oxide pre-sintered at 600 °C shows better rate and cycling performances. This can be ascribed to the synergistic effect of exposed {111} surface and smaller primary particle size, which improves interfacial stability and reduces Li+ ion diffusion distance. The particle size and surface orientation can be tailored to meet different applications of LiNi0.5Mn1.5O4 material.