Preparation of Spheroidal Spinel LiMn2O4 and Its High Temperature Performance

Abstract

In view of the high temperature instability of spinel LiMn2O4, a combination of elemental doping, material coating and morphology controlling was designed to improve its high temperature performance in this paper. The spherical MnO2 intermediate was prepared by the action of organic polyvinylpyrrolidone and ethylene glycol. Then, under the coating and doping of graphene and Al, a spheroidal LiMn2O4 material was obtained. The obtained materials were characterized by XRD, SEM, particle size analysis and electrochemical performance test. The results show that the introduction of graphene and Al can reduce the unit cell volume of LiMn2O4, shorten the interplanar spacing of each crystal plane, improve the stability of the unit cell and maintain its spherical structure. Amongst which, Al doping can greatly reduce the particle size. The electrochemical performance test at 55°C shows that simultaneous Al doping and graphene coating can not only maintain the spheroidal structure of LiMn2O4 cathode material, but also make it have good electrochemical properties: the initial discharge capacity can be up to 123.4 mAh.g−1 at 0.2 C rate and there is a discharge capacity of 101.2 mAh g−1 after 100 cycles. The sample with only graphene coating has a capacity of 91.7 mAh.g−1 after 100 cycles, while the sample without Al doping and graphene coating has a capacity of only 22.4 mAh.g−1 after 100 cycles.