Research On Structural Modification And Electrochemical Performance Of Li₂ZnTi₃O₈

The negative electrode material Li₂ZnTi₃O₈ for lithium ion batteries has attracted more and more attention in recent years due to its excellent electrochemical performance.In order to improve its electrochemical performance,this paper explores the influence of technological process and modification methods on its electrochemical performance through the optimization and modification of synthetic processes.（1）Li₂ZnTi₃O₈ was prepared by molten salt method.Process research was conducted from three aspects:calcination temperature,calcination time,and molar ratio of titanium source to molten salt.The results show that the sample obtained when the molar ratio of titanium source to molten salt is 1:4 and calcined at 750℃for 5h has the best electrochemical performance.After cycling 5 times at 1C,3C,5C,12C and 18C ratios,the specific discharge capacity is 199.8,187.3,183.2,174 and169.1mAh?g^-1;After 60 cycles at 3C rate,the specific discharge capacity was192.9mAh?g^-1.（2）Using H₂-Ar mixed gas（H₂ volume content 5%）as reducing gas,prepare Li₂ZnTi₃O₈ with certain oxygen vacancies,and optimize its calcination conditions.The results show that the oxygen-vacuum Li₂ZnTi₃O₈ prepared by calcining at 750℃for 5h has the best electrochemical performance.After 5 cycles of 2C,5C,10C,15C and 20C,the specific discharge capacity can reach 221.2,205.4,193.6,187.5 and 176.5mAh?g^-1,respectively.Compared with pure phase Li₂ZnTi₃O₈,the presence of oxygen vacancies does not significantly change the crystal structure and morphology of Li₂ZnTi₃O₈,but it has better rate performance and cycle performance.After 400 cycles at 3C rate,the discharge specific capacity is still 197.3mAh?g^-1,the capacity retention rate is 96%.（3）Using urea（CO（NH₂）₂）as the N-doped carbon source to prepare C&N-coated Li₂ZnTi₃O₈,and the phase characterization and electrochemical performance analysis of the C&N-coated Li₂ZnTi₃O₈.The results showed that the C&N layer coated on the surface of Li₂ZnTi₃O₈ did not significantly affect its crystal structure.After 400 cycles at6.61C(1.5A?g^-1),the discharge specific capacity of C&N-coated Li₂ZnTi₃O₈ remained at 229.2mAh?g^-1,much higher than that of pure phase Li₂ZnTi₃O₈(95.7mAh?g^-1).This may be because the coating of the C&N layer enhances the electronic conductivity of the material,accelerates the electron migration on the surface of Li₂ZnTi₃O₈,and improves the cycling performance of Li₂ZnTi₃O₈.