Preparation And Modification Of LiNi_0.6Co_0.2Mn_0.2O₂ Ternary Cathode Material For Lithium-ion Batteries

In recent years,the excessive consumption of fossil fuels has become an urgent issue need to be addressed.As an energy storage device,lithium-ion batteries are extensively applied various fileds.Although LiNi_0.6Co_0.2Mn_0.2O₂ has been proved to be a suitable cathode material,it still faces numerous problems that need to be improved,such as large loss of discharge capacity in first cycle,severe storage requirements,and poor thermal stability,which limit their service life.In this work,the ternary cathode material LiNi_0.6Co_0.2Mn_0.2O₂ is selected as primary material,modified by Mg and Al doping and microscopic morphology design,and investigated their electrochemical properties.The specific research results are as follows:（1）LiNi_0.6Co_0.2Mn_0.2O₂ was successfully prepared by hydrothermal method and high-temperature calcination,and the successful synthesis of the material was verified by a series of characterization means.The precursors obtained during the synthesis process were square-shaped primary particles assembled as secondary particles,and the final product after high-temperature calcination inherited the morphology of the precursors and was able to alleviate the volume expansion problem.It shows good electrochemical performance,the initial discharge specific capacity was 161.3 m Ah g^-1 at 50 m A g^-1 and 127.5 m Ah g^-1 after200 cycles,indicating that the hydrothermal synthesis of ternary cathode has good application prospects.（2）The LiNi_0.6Co_0.2Mn_0.2O₂ cathode material was investigated by Mg and Al doping.The results showed that the discharge specific capacity was 157.2 m Ah g^-1 for NCM-Mg in the first cycle and 168.5 m Ah g^-1 for NCM-Al.After 200 cycles,the discharge specific capacity was 135.2 m Ah g^-1 for NCM-Mg and 141.2 m Ah g^-1 for NCM-Al.The ion diffusion rate was calculated using cyclic voltammetry,and the results showed that NCM-Al has a larger ion diffusion rate.Al doping can effectively improve the electrochemical properties of the electrode materials because Al can not only increase the layer spacing and reduce the effect of harmful phase transitions,but also inhibit the dissolution of transition metals and hinder the extension of microcracks.（3）Single-crystal ternary cathode materials（SC-NCM）with Al doping（SC-NCMAl）were synthesized and compared for the performance differences between them.The initial discharge specific capacity of SC-NCMAl was 155.5 m Ah g^-1 at 50 m A g^-1,and 145.5 m Ah g^-1 after 100 cycles.The single crystal material is able to ignore the influence on grain boundaries and also to comply with strong volume changes,thus effectively releasing anisotropic microscopic stresses and thus reducing crack formation,while doping also effectively improves the performance of the material,which brings a new way to the development of next-generation lithium-ion batteries and cathode materials.