Study On The Improvement Of LiNi_0.6Co_0.2Mn_0.2O₂ Battery Performance By Surfactants

In this paper,the high-nickel ternary layered oxide LiNi_0.6Co_0.2Mn_0.2O₂cathode material is taken as the research object.Aimed at the problems of LiNi_0.6Co_0.2Mn_0.2O₂cathode materials of lower actual charging-discharge capacity than theoretical specific capacity,poor cycling stability and poor rate performance,this work intended to improve the properties of materials by introducing different types of surfactants in the process of hydrothermal synthesis.The specific research contents and results are as follows:（1）Gemini,which is a double-cationic surfactant with high activity,was selected to modify the LiNi_0.6Co_0.2Mn_0.2O₂materials.It can be found from the SEM analysis that with the increase of surfactant,the size of material particles is greatly reduced and the distribution of particles is more uniform,which are conducive to the diffusion of lithium ions and the processing technology of materials.The electrochemical performance test results show that the introduction of Gemini can indeed improve the electrochemical performance of lithium ion batteries.When the addition amount of Gemini is 2.5 wt.%,the electrochemical performance of LiNi_0.6Co_0.2Mn_0.2O₂is the best.（2）The effect of PVP that a sort of non-ionic surfactant with long chain on the morphology and electrochemical properties of LiNi_0.6Co_0.2Mn_0.2O₂cathode material were investigated.XRD and SEM results imply that the positive electrode materials prepared by adding PVP have higher crystallinity,better layer structure and lower degree of Li⁺/Ni²⁺mixing.Through the analysis of electrochemical performance,it can be found that the addition of PVP improves the diffusion coefficient of lithium ion,reduces the polarization degree and charge transfer impedance of the battery,thus then improves the electrochemical performance of the materials.When 2.5 wt.%PVP surfactant is added,the electrochemical performance of LiNi_0.6Co_0.2Mn_0.2O₂cathode material is obviously improved.（3）The low-cost anionic surfactant SDBS was also introduced to regulate the morphology and properties of LiNi_0.6Co_0.2Mn_0.2O₂cathodes.SEM results demonstrate that the addition of SDBS can reduce particle size and increase particle dense degree.It can be seen from the electrochemical performance test that when adding amount of SDBS is 2.5 wt.%,the specific discharge capacity at 0.2 C rate increased by about 40 mAh g^-1,and the comprehensive electrochemical performances are significantly better than the cathode material prepared by adding the other two surfactants.