Research Of LiNi_0.8Co_0.1Mn_0.1O₂ Cathode Material Preparation And Properties With Large Primary Particle

Cathode materials restrict the application of lithium-ion batteries.The specific capacity,voltage and cycle performance of lithium-ion batteries are limited by the existing cathode material preparation technology.The nickel rich LiNi_0.8Co_0.1Mn_0.1O₂?NCM811?cathode material requires a high oxygen content environment in the high temperature process to ensure an orderly layered structure.Suitable sintering atmosphere process is conducive to the preparation of high-performance cathode material and cost saving.NCM811 material with primary particle size up to micron and no agglomeration has higher compaction density than current mainstream secondary spherical particle material,which is conducive to improving the volume specific energy of the battery and suitable for power batteries.At present,there are few reports on the preparation methods of NCM811 cathode materials with large primary particle.Using commercial precursors,this paper researches the relationship between sintering atmosphere process and material structure and properties from the aspects of gas velocity and reactive oxygen concentration in sintering process.Too high a gas flow rate can take away too many lithium sources,leading to insufficient reactants.Excessive and insufficient oxygen content environment will lead to the degradation of material properties.NCM811 cathode material with high electrochemical properties can be prepared under the conditions of 0.2 L min^-1 gas flow rate,15 h high temperature sintering process and 50%oxygen content atmosphere.Under 93%oxygen content atmosphere,the 0.1C specific capacity of the cathode material can reach 204.1 mAh g^-1,and after 300 cycles of 1C,the capacity retention rate is 86.1%.According to the atmosphere process,high-temperature solid phase method was used to research the preparation of high-performance NCM811 cathode material with large primary particle morphology from three aspects:lithium content,sintering temperature and sintering time.The amount of lithium,sintering temperature and insulation time interact with each other on the morphology and performance of materials.Excessive lithium source,high temperature and extended sintering time are all conducive to primary particle growth,but the mismatch of the three conditions will lead to material structure chaos and performance decline.At the same temperature,with the increase of lithium content,the performance of the samples firstly rise and then fall,but the trend changes are not synchronous at different temperatures.At 830?,the performance of 1.10 lithium samples is the best,while when the temperature rises to 850?,the performance of 1.15 lithium samples is the best.With the same amount of lithium,increasing sintering temperature will increase the performance of the sample,but overfiring will occur when the temperature is too high.And high temperature is conducive to improving the phenomenon of primary particle agglomeration of the sample.With the extension of sintering time,the properties of the samples firstly increase and then decrease,and the long-term high temperature environment is conducive to the uniform growth of primary particles.Excess 15%of lithium source,sintering at 850?for 16 h can produce NCM811cathode material with no agglomeration,uniform and larger than 1?m primary particles.