LiNi_0.95-xyCo_xMn_yAl_0.05O_{2 High Nickel Cathode Material For Lithium Ion Batteries} Exploration Of Low Cobaltization

LiNi_0.8Co_0.15Al_0.05O₂(or LNCA)cathode material has a very high specific capacity,a feature that would greatly improve the range of pure electric vehicles if it were used in vehicle batteries.The expensive transition metal cobalt(Co)is limiting the development of LNCA cathode materials,so researchers are working to find other metals to reduce the cobalt content in LNCA materials to synthesize high nickel quaternary materials,or even replace Co to synthesize new high nickel and cobalt-free materials to reduce costs.In order to investigate the feasibility of replacing cobalt with manganese(Mn)as a transition metal,and to consider the contribution of nickel content to the capacity of high nickel materials,two elements,Ni and Mn,were selected to replace Co in the synthesis of high nickel quaternary materials composed of different nickel-cobalt and nickel-manganese elements,and the properties of each were investigated and compared.(1)LiNi_0.8Mn_0.15Al_0.05O₂ materials were prepared by oxalic acid co-precipitation.The effects of the molar concentration dosage ratio of oxalic acid/metal salt in the oxalic acid co-precipitation reaction system on the morphology of the oxalate precursors and the effects of the pre-sintering time and sintering time on the electrochemical properties and structure of the end products were investigated.The best performance of the Li Ni_0.8Mn_0.15Al_0.05O₂ material was investigated by comparing the structural characteristics and electrochemical properties of each sample when the molar concentration of oxalic acid/metal salt was 1.4,the pre-sintering time of the precursor was 4 h and the sintering time was 21 h.The LNCA and Li Ni_0.8Mn_0.15Al_0.05O₂materials were then prepared using the optimal process conditions and compared with commercial LNCA materials in terms of cycling and multiplicity performance.The results show that although the oxalic acid co-precipitation method and the corresponding preparation conditions are feasible,the cycling and multiplicity performance of Li Ni_0.8Mn_0.15Al_0.05O₂ is not as good as that of LNCA.(2)On the premise of determining the composition ratio of Ni and Al,the effects of lowering Co and raising Mn on four different Co/Mn ratios of Li Ni_0.8Co_0.15-xMn_xAl_0.05O₂(x=0,0.05,0.1,0.15)materials were investigated by lowering the Co content and raising the Mn content and an attempt was made to find out the reasons for the difference in performance between Li Ni_0.8Co_0.15Al_0.05O₂ and Li Ni_0.8Mn_0.15Al_0.05O₂ materials.The experimental results show that although it is feasible to use Mn to replace Co in the synthesis of high nickel-free ternary materials,some of the properties,such as the first coulombic efficiency and discharge specific capacity,need to be sacrificed;in a comprehensive view,the best performance among the four materials is a small amount of Mn substituted quaternary Li Ni_0.8Co_0.10Mn_0.05Al_0.05O₂material.On this basis,the range of Co/Mn ratios was narrowed down and four different Co/Mn ratios of high nickel quaternary Li Ni_0.8Co_0.10-yMn_0.05+yAl_0.05O₂(0.01?y?0.04)materials were prepared to find out the best elemental composition ratio of high nickel quaternary materials with the best performance while minimizing the amount of Co.(3)On the basis of the experiments in the previous section,considering that the Ni content determines the capacity and energy density of the high nickel materials,we investigated the effect of lowering Co and raising Ni on the high nickel quaternary Li Ni_0.8+zCo_0.10-zMn_0.05Al_0.05O₂(z=0.01,0.03,0.05)by lowering the Co content and raising the Ni content under the premise of determining the composition ratio of Mn and Al materials and identify the composition ratios of the best performing high nickel quaternary materials.The experimental results show that among the three Li Ni_0.8+zCo_0.10-zMn_0.05Al_0.05O₂ materials with different Ni and Co contents,the Li Ni_0.83Co_0.07Mn_0.05Al_0.05O₂ material has the best performance.