Preparation And Performance Of Nickel-rich Ternary Cathode Materials LiNi_0.8Co_0.1Mn_0.1O₂ For Lithium Ion Batteries

LiNi_1-x-yCo_xMn_yO₂（0.6≤1-x-y≤1.0）,a high-nickel ternary cathode materials for lithium-ion batteries,has high reversible specific capacity and low cost,and is considered to be a promising cathode materials for lithium-ion batteries.The higher the Ni content in LiNi_1-x-yCo_xMn_yO₂,the higher the reversible specific capacity.Therefore,LiNi_0.8Co_0.1Mn_0.1O₂ cathode materials has become a current research hotspot and has received extensive attention from industry and researchers.However,the LiNi_0.8Co_0.1Mn_0.1O₂ cathode materials has serious problems of lithium-nickel mixing and high residual lithium at the interface,resulting in poor cycle stability and storage performance.In this paper,starting from the preparation of LiNi_0.8Co_0.1Mn_0.1O₂ cathode materials,the influence of materials preparation technology and storage conditions on electrochemical performance was studied.On this basis,a performance restoration scheme for the stored LiNi_0.8Co_0.1Mn_0.1O₂cathode materials was proposed,which provides an important theoretical and practical basis for its industrial application.Specific research contents include:（1）Research on the preparation process of high nickel ternary cathode materials LiNi_0.8Co_0.1Mn_0.1O₂.Using Ni_0.8Co_0.1Mn_0.1（OH）₂ as precursor and Li OH·H₂O as lithium source,LiNi_0.8Co_0.1Mn_0.1O₂ cathode materials was prepared by high temperature solid-phase method.The effects of different lithium content,calcination temperature and calcination time on the materials structure and electrochemical properties were systematically studied,and the best preparation process conditions were obtained:The molar ratio of Ni_0.8Co_0.1Mn_0.1（OH）₂/Li OH·H₂O was 1/1.05,the calcination temperature was 750°C,and the calcination time was 15 hours.The prepared LiNi_0.8Co_0.1Mn_0.1O₂ cathode materials has a good layered structure and a low degree of lithium-nickel mixing,showing excellent electrochemical performance.In the voltage range of 2.8～4.5 V and the current density of 0.1 C,the initial discharge capacity is 223 m Ah g^-1,and the first cycle Coulomb efficiency is 91.5%;after 150 cycles at 1 C,the discharge capacity still remains 138 m Ah g^-1.（2）Research on the storage performance of high nickel ternary cathode materials LiNi_0.8Co_0.1Mn_0.1O₂.The effects of different storage conditions（room temperature air and dry carbon dioxide environment）on the structure and electrochemical performance of high-nickel ternary cathode materials were investigated.The results show that the LiNi_0.8Co_0.1Mn_0.1O₂ sample stored in air for 30 days is completely covered by a carbonate impurity layer with a thickness of～150 nm,and the discharge capacity at 0.2 C decays severely and is only 29 m Ah g^-1;However,the LiNi_0.8Co_0.1Mn_0.1O₂ samples stored in dry carbon dioxide for 30 days only had granular carbonate impurities on the surface,and the discharge capacity at 0.2 C did not decay significantly,still 178 m Ah g^-1.The results show that moisture in the storage ambient air is the main factor promoting the formation of carbonate impurities and electrochemical decay on the surface of high-nickel ternary materials.On this basis,a performance restoration scheme of LiNi_0.8Co_0.1Mn_0.1O₂ cathode materials was proposed.It was found that the electrochemical performance of the stored LiNi_0.8Co_0.1Mn_0.1O₂ could be restored by a simple heat treatment,the restored LiNi_0.8Co_0.1Mn_0.1O₂ after heat treatment at 600°C showed an initial discharge capacity of 191 m Ah g^-1 at a voltage range of 2.8–4.3 V and a current density of 0.1 C;the discharge capacities remained 173 and 155 m Ah g^-1 after 50 cycles at 0.2 C and 1C,respectively,which were basically consistent with the original LiNi_0.8Co_0.1Mn_0.1O₂ samples without deterioration.