Synthesis And Modification Of LiNi_xCo_yMn_zO₂Cathode Material For Lithium Battery

LiNi_xCo_yMn_zO₂has attracted numerous researchers’ interest for its highspecific capacity, high tap tensity and excellent high temperature performance,and becomes one of the best systems of cathode materials for lithium battery.LiNi_xCo_yMn_zO₂is usually produced via hydroxide co-precipation method inindustrial process.At the present days, the relative mature production incommercial of this system areLiNi_1/3Co_1/3Mn_1/3O₂,LiNi_0.4Co_0.2Mn_0.4O₂,LiNi_0.5Co_0.2Mn_0.3O₂. The dischargecapacity of these materials can reach160¹70mAh/g, but there still exists ahuge disparity compared to the theory specific capacity of material.The capacity of high Ni content LiNi_0.8Co_0.1Mn_0.1O₂is close to its theoryspecific capacity.However, due to its poor structure stability, the high capacitypotential is hard to fully exploited.So the modification of LiNi_0.8Co_0.1Mn_0.1O₂becomes a hot research topic.What’s more, due to the intense corrosion effect ofHF decomposed from LiPF6, which is a main constitute of electrolyte, thedischarge capacity performance of LiNi_xCo_yMn_zO₂at high rate is poor. Thisproblem could be reduced through surface modification, which can play a roleof protecting and stabling strcture. This passage adopts LiNi_0.4Co_0.2Mn_0.4O₂asexample, proving proper surface modification can improve the performance ofLiNi_0.4Co_0.2Mn_0.4O₂at high rate.Experiment part of the passage is consisted of two main parts: synthsis ofLi[Ni_0.8Co_0.1Mn（0.1）]_0.4[Ni_0.5Co_0.2Mn_0.3]_0.6O₂(denoted by LiNi_0.62Co_0.16Mn_0.22O₂)with a core-shell structure and the surface modification of LiNi_0.4Co_0.2Mn_0.4O₂.First part mainly narratives the synthsis of precuesors vie the hydroxiteco-precititation. The sintering process is definited through TG test. Aftersintered with lithium resource, we obtained the aimedmaterial-LiNi_0.62Co_0.16Mn_0.22O₂, the electrochemical performance of whichimproved a lot compared with pure LiNi_0.8Co_0.1Mn_0.1O₂. The second part ismainly focused on the surface modification of LiNi_0.4Co_0.2Mn_0.4O₂usingSiO₂/SnO₂, seperately. The best coating amount is definited through electrochemical experiment. The high rate performance of LiNi_0.4Co_0.2Mn_0.4O₂is greatly improved after coating0.5wt%SiO₂.