Electrochemical performances discharged to lower potential for LiNi0.5Mn1.5O4 cathode material synthesized by PAA-assisted co-precipitation method

The cathode material LiNi0.5Mn1.5O4 with cubic spinel structure was prepared by co-precipitation process using LiCl, NiCl2·6H2O and MnCl2·4H2O as raw materials, oxalate as a precipitant, polyacrylic acid(PAA) as a dispersant agent. The synthesized materials were analyzed and characterized by X-ray diffraction(XRD), scanning electron microscopy(SEM). It was found that all of the samples had cubic spinel structure without undesired impurities. According to the SEM, the powder had uniform particle size and its aggregations was reduced because of the assistance of polyacrylic acid. Moreover, on the basis of the electrochemical performances tests, it could be found that the initial discharge capacity discharged to lower potential for the samples with PAA addition were higher than the theoretical capacity of the spinel LiNi0.5Mn1.5O4. All the samples synthesized by PAA-assisted method possess good capacity retention and rate performance, compared to the sample without PAA addition. The discharge capacity for 3wt% sample was significantly enhanced about 87.5% at 1C, 39.4% at 2C and 43.5% at 5C with respect to the sample without PAA. The great enhancement could be attributed to an effectively shortened Li-ion diffusion path way.