Improve The Interface Problem In All-solid-state Lithium Batteries By Surface Coating Of The Cathode Material

Due to the increasing aggravation of the energy crisis and environmental crisis,the golden age of electric vehicle development is coming.As a core component of electric vehicles,lithium battery has attracted a lot of attention.some relevant scholars have suggested that all-solid-state lithium battery will be used as the next-generation power battery to meet the future demand for lithium battery.However,if all-solid-state lithium battery want to realize large-scale commercial application,it is necessary to overcome the interfacial problem between electrode material and solid-state electrolyte.In this paper,we coated cathode material with ETPTA-PEG or PANI-PEG to improve the interfacial problem between it and solid-state electrolyte,thus improving the overall performance of the battery.In this paper,the EPTTA-PEG coating layer was successfully formed on the surface of the ternary material（NCM811）by using ultraviolet irradiation method,and the existence of the coating layer was verified by SEM,TEM and FTIR tests.The subsequent electrochemical tests showed 4%is the best coating amount.The capacity retention rate of 4%coated NCM after 100 cycles reaches 84.2%,which is much higher than 64.5%of uncoated materials.In addition,the results of CV test,galvanostatic charge/discharge measurement,rate test and EIS test show that the coating layer can effectively reduce the polarization of NCM,suppress the interfacial side reactions and improve the physical contact between the cathode material and the solid-state electrolyte.Then,wet chemical method was used to coat NCM811 with PANI-PEG,and the existence of the coating layer was confirmed by SEM,EDS,and FTIR tests.Electrochemical tests showed that 5%is the optimal coating amount,the capacity retention rate of 5%coated NCM was 80.0%after 100 cycles.In addition,PANI is a good electronic conductor,thereby the rate performance of the coated material is much better than that of the uncoated material.At 2 C,the discharge capacity of 5%coated NCM is 62.7 m A h g^-1,and the discharge capacity of uncoated NCM is 1.5 m A h g^-1.CV test,galvanostatic charge/discharge measurement and EIS test show that the coating layer can effectively reduce polarization and improve the interfacial problems.