Study On The Coated Modification Of LiNi_0.5Co_0.2Mn_0.3O₂ Cathode Material For Lithium-ion Battery

In the cathode materials of lithium ion batteries,materials are widely accepted by the market because of their advantages such as low cost,high capacity and high safety.However,in LiNi1-x-yCoxMnyO₂ materials' long-term-use process,in their contact with electrolyte and in the intercalation-deintercalation process of lithium ions in the material,there will be irreversible phase transition and other side effects such as dissolution of transition metal ions in the surface area where LiNi1-x-yCoxMnyO₂ material and electrolyte contact.These side effects will lead to an increase in the impedance of the electrode reaction,and reducing the cycle performance of the material.In order to solve this problems,we coated a layer of more stable material on the surface of the LiNi1-x-yCoxMnyO₂ material to reduce the contact area of the material with electrolyte,thus enhancing the material cycling performance.In his paper,we coated SnO₂,Al2O3 and PEDOT:PSS?poly 3,4-ethylenedioxythiophene:poly Styrene sulfonic acid?particles on the surface of commercialized LiNi0.5Co0.2Mn0.3O₂ materials by wet method.The X-ray diffraction,scanning electron microscopy,energy dispersive spectroscopy,cyclic voltammetry,impedance spectroscopy,and cyclic performance curves were employed to characterize and test electrochemical properties of the coated LiNi0.5Co0.2Mn0.3O₂ materials.And we determine effects of coated for morphology and electrochemical properties of materials.In the SnO₂ coating experiments,we studied the effects of coating amount,calcination temperature and calcination time on performance of materials,And determinded that the samples with 0.5%of coating amount,8h of calcination time and calcined at the temperature of 600? have the best electrochemical performance.Compared to the uncoated sample,It had 144.25mAh/g initial specific discharge capacity and 132.37mAh/g after test 50 cycles,which remains 91.17%of its capacity,This resuit is better than uncoated coated samples which 140.59mAh/g initial specific discharge capacity and 132.27mAh/g after test 50 cycles,remains 86.03%of its capacity.In the experiment of Al2O3 coated LiNi0.5Co0.2Mn0.3O₂ materials,the effects of coating amount,calcination temperature on performance of material were studied.And it's clear that samples with 0.5%Al2O3 coating amount,6h of calcination time and calcined at the temperature of 500? demonstrated the best electrochemical performance.Similarly,we compared to the uncoated sample's 145.89mAh/g.initial specific discharge capacity and 122.72mAh/g,after 50 cycles,which remains 84.11%of its capacity,the figure for coated samples were142.75mAh/g,138.35mAh/g and 96.91%,respectively.In the experiment of PEDOT:PSS coated LiNi0.5Co0.2Mn0.3O₂ materials,we only studied effect of coating amount on performance of material.And we determinded when coating amount was 1%,the material has the best electrochemical performance.The specific discharge capacity of the first cycle was 130.05mAh/.Aafter 50 ycles,the figure was 126.29mAh/g and the capacity retention rate was 97.10%.