Study On The Preparation And Modification Of Nickel-rich Ternary Cathode Materials

Nickel-rich ternary cathode material LiNiXCoYMn1-X-YO2(X>0.6)is considered to be an ideal lithium ion battery cathode material because of its high reversible specific capacity,excellent rate performance and environmental friendliness.However,the shortcomings of low specific discharge capacity at high current,poor stability and thermal stability limit its further application and development.In this paper,the synthesis and optimization of material LiNiXCoYMn1-X-YO2(X>0.6)were carried out,and mechanism about its were investigated.Firstly,the rheological phase method was used to prepare LiNi0.8Co0.1Mn0.1O2 cathode material,trace amounts of zirconium(Zr)have been adopted to modify the material to obtain Zr/LiNi0.8Co0.1Mn0.1O2 material.Physical and chemical characterization and electrochemical performance tests were carried out respectively.The results show that the Zr-modified LiNi0.8Co0.1Mn0.1O2 material exhibits excellent electrochemical performance.The Zr-modified LiNi0.8Co0.1Mn0.1O2 is capable of delivering a discharge capacity of 107 mAh/g at a 10C rate,much higher than 28 mAh/g delivered by pristine materials.In addition,during cycling at 1C,the Zr-modified LiNi0.8Co0.1Mn0.1O2 shows an improved capacity retention of 92%after 100 cycles,higher than 75%for pristine LiNi0.8Co0.1Mn0.1O2.Then the LiNi0.68Co0.10Mn0.22O2 cathode material was prepared by coprecipitation method through optimizes the transition metal atoms of Ni,Co and Mn.The optimal synthesis conditions were investigated from the sintering temperature,sintering time and excess lithium amount.The results indicate that a sintering temperature of 780? with a sintering time of 16 h and an excess lithium amount of 5 wt%could achieve a more stable and lower cation mixing degree LiNi0.68Co0.10Mn0.22O2 cathode.It delivers a reversible discharge capacity as high as 197.4 mAh/g at C/10,and exhibits a capacity retention of 90.2%and 83.5%at 1C and 3C after 200 cycles,respectively.Finally,a layer thick Al2O3 material was coated on the surface of LiNi0.68Co0.10Mn0.22O2 cathode material by atomic deposition method.And the LiNi0.68Co0.10Mn0.22O2@Al2O3 composite was obtained by high temperature sintering.Physical and chemical characterization and electrochemical performance tests under different conditions were carried out.The results show that Al2O3 can be uniformly coated on the surface of LiNi0.68Co0.10Mn0.22O2 cathode material,and showed excellent performance much higher than pristine material under rule,high temperature and high voltage test conditions.The solid electrolyte interphase(RSEI)resistance of LiNi0.68Co0.10Mn0.22O2 cathode material increased from 30.45 ? to 137.1 ? after 50 cycles of 1C,which is much higher than LiNi0.68Co0.10Mn0.22O2@Al2O3(22.16?27.83 ?)that under the same conditions.These indicated that LiNi0.68Co0.10Mn0.22O2@Al2O3 material will have a good application prospect.