Preparation And Modification Research Of High Voltage Single Crystal LiNi_0.5Co_0.2Mn_0.3O₂ Cathode Material

LiNi_xCo_yMn_zO₂ with high energy density,high security,high cycle performance,and low cost,is a very promising cathode.This subject mainly research on the fabrication of LiNi_0.5Co_0.2Mn_0.3O₂ used as a single crystal cathode,and it is mainly used in the filed of new energy passenger vehicles.Ni_0.5Co_0.2Mn_0.3?OH?₂ precursor was first synthesized in the subject.NiSO₄,CoSO₄,MnSO₄ were used as raw materials.NH₃ and NaOH were used as complexing agent and precipitating agent,respectively.the as-prepared Ni_0.5Co_0.2Mn_0.3?OH?₂precursor with the mean particle size 4.5?m can meet the fabrication requirement of single crystal cathode,when the molar ration of NH₃/MeSO₄ is 0.4,and the pH of solution is 11.5.Lithium hydroxide was mixed with the precursor,and single crystal LiNi_0.5Co_0.2Mn_0.3O₂ was fabricated by multi-step sintering.The electrochemical performance of LiNi_0.5Co_0.2Mn_0.3O₂ have been investigated.The effect of sinter temperature,sinter time and the molar ration of Li/Me on electrochemical performance were studied.The single crystal cathode can meet the requirments when sintered at 980?for 12h with 9%mol excessive lithium.The mean particle size of the cathode is 5.0?m.The first discharge capacity is 185.5mAh/g in the voltage range of 3.0-4.5V and the capacity retention is 96.7%after 50 cycles.The single crystal cathode was coated with TiO₂ to improve the electrochemical performance under a high voltage?HV?.Used four isopropyl titanate as raw material,when the TiO₂ coating amount is 0.6%,the initial discharge specific capacity of the coated material is as high as 186.3 mAh/g,and the capacity retention rate is 98.3%after 50 cycles,which is 1.6%higher than that without coating.