Synthesis and performance of hollow LiNi0.5Mn1.5O4 with different particle sizes for lithium-ion batteries

Abstract

High voltage spinel LiNi_0.5Mn_1.5O₄ is a promising cathode material for next generation lithium ion batteries. A simple method of synthesizing hollow LiNi_0.5Mn_1.5O₄ spinel using MnCO₃ as the manganese resource is presented. The hollow structure forms during the calcination process at 850 °C. The transformation from MnCO₃ to manganese oxide and inter-diffusion of Mn and Ni atoms are excluded as reasons for the formation of the hollow structure. Four hollow LiNi_0.5Mn_1.5O₄ samples with different particle sizes were synthesized by controlling the reactant concentration. The effects of particle size on the electrochemical performance of hollow LiNi_0.5Mn_1.5O₄ have been investigated in detail. The hollow LiNi_0.5Mn_1.5O₄ samples with particle size less than 1 μm and some small broken particles of about 200 nm show poor rate capability and cycling performance due to their poor contact with conductive additive and high interface resistance. The hollow LiNi_0.5Mn_1.5O₄ samples with diameters of 2 or 6 μm exhibit better rate capability and cycling performance. This is because most of the micro-sized particles can make direct contact with the conductive additive and have low interface resistance; moreover, the hollow structure also decreases the Li⁺ ion and electron diffusion distance.