Study On Preparation And Surface Modification Of Lithium-rich Cathode Materials

Owe to high specific capacity,low cost,and high safety,lithium-rich layered cathode materials enjoy broad prospects in the application for lithium ion batteries.However,the structure of lithium-rich cathode materials is relatively complicated,and there are a series of problems in electrochemical performance,such as the first irreversible capacity loss,cycle capacity loss,and discharge voltage attenuation.All this properties stand in its further application.Therefore,there is great value in the study of the preparation and modification of lithium-rich layered cathode materials.To this end,the sol-gel method was used to prepare the lithium-rich layered cathode material.The process parameters of the optimized sintering temperature has improved,and the Al₂O₃coating is modified by the improved uniform precipitation method to improve electrochemical performance such as the first Coulomb efficiency,cycle performance,etc.of the cathode material.The sol-gel method was used to prepare the precursor,which gave possibility to a lithium-rich cathode material with a small particle size and a uniform distribution by optimizing the sintering process.The cathode material performs high purity and good crystallinity.Meanwhile,the degree of the cation mixing has reduced.Lithium-rich cathode materials prepared with 775°C sintering temperature parameters exhibited better electrochemical performance.Tested at 0.1 C,2.0?4.8 V,such materials exhibit the following performance:the first cycle discharge specific capacity is 213.6 m Ah/g,the first Coulomb efficiency is 71.8%,the 100th cycle discharge specific capacity is181.6 m Ah/g,and the capacity retention rate is 84.9%,together with a median voltage attenuation,electrochemical impedance,and cyclic voltammetry.The liquid-phase uniform precipitation coating method was used to modify the Al₂O₃coating on the lithium-rich cathode material,which was applied to explore the effect and mechanism of the Al₂O₃coating amount on the electrochemical performance.Al₂O₃is evenly coated on the surface of the material particles to form a nano-scale coating layer.The coated material still maintains the original layered structure.Meanwhile,the cation mixing is reduced.Tested electrochemically at 0.1 C,2.0?4.8 V,the performance of the lithium-rich cathode material with an Al₂O₃coating of 0.7wt.%.are as follows:the first cycle discharge specific capacity is 251.3 m A·h/g,the first Coulomb efficiency can reach 76.1%,and the capacity remains more after 100 cycles with a rate of 92.9%.At the same time,the coating also effectively suppresses the voltage decay during the cycle.It could be concluded that appropriate amount of Al₂O₃coating improves the electrochemical performance of the cathode material.