Electrochemical properties of high-voltage LiNi0.5Mn1.5O4 synthesized by a solid-state method

Abstract

LiNi_0.5Mn_1.5O₄ cathode material has been synthesized by a solid-state reaction designedly using industrial raw materials (Li₂CO₃, NiO and electrolytic MnO₂) in bulk scale, which are all used without further purification. The aim is to find the optimal preparation process of LiNi_0.5Mn_1.5O₄ material for commercial application. The synthesis temperatures are adjusted to form a disordered Fdm structure at 800–950 °C for 12 h and then at 600 °C for 6 h. Meanwhile, some powders have also been calcined at 850 °C for 8–14 h and next annealed at 600 °C for 6 h. XRD patterns, SEM micrographs and distribution curves of particle size shows that the LiNi_0.5Mn_1.5O₄ cathode material calcined at 850 °C for 12 h and then annealed at 600 °C for 6 h exhibits the best crystallinity, crystal shape as well as the best normal distribution. Electrochemical tests show that the LiNi_0.5Mn_1.5O₄ material synthesized at 850 °C for 12 h and then annealed at 600 °C for 6 h has the highest capacity and excellent rate capability. After 200 cycles, the capacity retentions of the sample at 1, 2 and 5 C are as high as 97.8%, 98.5% and 98.0% of its initial capacities (120.8, 118.1 and 111.2 mA h g⁻¹), respectively. The fundamental findings in this work can be applied to guide the synthesis of spinel LiNi_0.5Mn_1.5O₄ as high performance electrode materials for lithium ion batteries, especially for industry.