Research On The Synthesis And Modification Of LiNi_0.8Co_0.1Mn_0.1O₂ Cathode Material For Lithium Ion Battery

Great advantages in energy density and reliability of Li-ion batteries have resulted in successful applications in the field of consumer electronics.The ratio of cathode material to the manufacturing cost of lithium ion batteries is 30 to 40%.The physical and chemical properties of the cathode materials affect the performance indexes of the lithium ion batteries’ cycling life,safety and energy density.The layered ternary material LiNi_xCo_yMn_1-x-yO₂（NCM）,through the synergistic reaction of Ni-Co-Mn,exhibits advantageous mechanistic activity wherein the Ni is partially substituted by Co and Mn in the high nickel layered ternary material.This phenomenon enables the production of cathode material which combines the advantages of many desirable battery material characteristics.Good performance of LiCoO₂,high specific capacity of Li NiO₂,high safety performance,and low cost of LiMnO₂ are qualities of this ternary material which endows superior overall performance when compared with any other single material.In this study,we assemble button-type half cells with lithium chips as the counter electrode to examine electrochemical properties of LiNi_0.8Co_0.1Mn_0.1O₂ cathode material and investigate interface modification technology used to alter the surface of the NCM material.The work herein aims to overcome the inherent shortcomings of nickel-rich materials,such as weak water absorbency,poor surface stability and so on.And comprehensively improve the scope of commercialized applications in lithium ion batteries.The following summary points list the focus of the main work content:（1）Using NaOH as a precipitating agent and ammonia as complexing agents,the high Nickel LiNi_0.8Co_0.1Mn_0.1O₂ cathode materials with good layered structure were prepared by continuous hydroxide co-precipitation method.The influence of precursor preparation conditions and sintering temperature on the properties of products were studied.（2）The Li₂O-2B₂O₃（LBO）glass is uniformly coated on the surface of NCM which acts as a protective layer increasing durability.By preventing direct contact between the NCM electrode and the electrolyte,it effectively resists corrosion of the HF,inhibiting the dissolution of the transition metal ions,and stabilizing the structural stability of the NCM material.（3）We demonstrate a facile approach to modify the surface of NCM with B-containing molecules.Via condensation between the diol groups of 4-vinylbenzeneboronic acid（4-VBBA）and hydroxy residues on NCM,a layer of 4-VBBA can be covalently bonded on NCM to alter the surface properties of NCM.Improving the material’s problematic water absorption in actual production is achieved and elucidated.It is demonstrated that the4-VBBA layer has a great effect on the formation behavior of the SEI film,leading to an improved electrochemical performance of the Ni-rich material.