Preparation And Modification Of Na₂Ti₃O₇ Anode Material

Titanium-based compounds are potentially suitable electrode materials for high-rate lithium-ion batteries due to small volume expansion during lithium insertion and deintercalation,and a higher operating voltage compared to Li+/Li redox couple,allowing them to avoid lithium dendrites during charge/discharge cycles,and therefore exhibit excellent cycling stability and safety properties at high currents.This paper addresses the problem of low electron/ion conductivity of alkali metal titanate(Na2Ti3O7),which affects the high-rate performance of electrode materials and proposes to improve the material performance and investigate the effect of different morphologies on the battery performance,starting from both coating modification and morphology control.Pure Na2Ti3O7 anode material was prepared by solvent evaporation,the surface was coated(0,1,3 and 5 wt.%)Li4Ti5O12 and La2O3(0,1,3 and 5 wt.%)form the Na2Ti3O7@Li4Ti5O12 and Na2Ti3O@La2O3 composites by chemical deposition methods.Based on the characterization of the structure and morphology of the composites and the analysis of the electrochemical test results,the optimal coating amount was determined and the influence of the coating layer on the material properties was discussed.The results show that surface coating can effectively inhibit the corrosion of electrode materials by electrolyte,which is beneficial to improve the diffusion kinetics of lithium ions and improve the electrochemical performance of active substances.Moreover,the appropriate coating amount is helpful for the active material to show better electrochemical performance.The 3wt.%Li4Ti5O12 and La2O3 composite materials have relatively good cycling performance and faster lithium-ion diffusion ability.In order to study the influence of the special morphology on its electrochemical performance,the paper prepared sphere-like Na2Ti3O7 by a simple solvothermal method and successfully prepared sea urchin-shaped Na2Ti3O7 with different spike lengths by adjusting the acidity of the solution.The results show that the material morphology can be optimized and materials with larger specific surface area can be prepared by regulating the solution pH.The sea urchin-like Na2Ti3O7 has a larger specific surface area and better structural stability,which is conducive to better contact of the material with the electrolyte,so that lithium ions and electrons have shorter diffusion paths and the material shows better electrochemical properties.After 1000 cycles at a 1 C rate,the specific capacity of NTO maintains at 70%.Even at a 5 C rate,NTO-2 delivers a discharge capacity of 71.5 mAh g-1 after 1000 cycles.The above results indicate that both surface coating and morphology control can effectively improve the electrochemical performance of electrode materials.