Research On Synthesis And Electrochemical Of Lithium Zinc Titanate As Anode Material For Lithium-ion Batteries

Li₂ZnTi₃O₈ has attracted much attention by the researchers and is expected to become a next-generation anode material for lithium-ion battery,because of its low cost,abundant raw materials,environment-friendly,excellent cycle stability,high safety performance.Li₂ZnTi₃O₈ has poor electrochemical performance because of its low conductivity.In order to solve the instability of the electrochemical performance of pure phase zinc zinc titanate,a research route from the appearance and size,surface coating to ion doping of synthetic Li₂ZnTi₃O₈ was designed.In this paper,porous spherical Li₂ZnTi₃O₈ was synthesized,and then Li₂ZnTi₃O₈/C and Li₂ZnTi₃O₈/CN were synthesized to reserch the properties of carbon coating and carbon-nitrogen Co-coating.Finally,the modification methods of compound doping and ion doping were studied.Firstly,the macro-morphology of Li₂ZnTi₃O₈ was studied.The effects of two different titanium sources,different NaCl additions and different surfactants?PVP,CTAB and SDBS?on the morphology,phase and electrochemical properties of Li₂ZnTi₃O₈ were investigated by high temperature solid-phase method.The optimum conditions are as follows:heat treatment temperature 750?,heat treatment time 6 h,0.1 mol/L NaCl solution addition 1.5 mL assisted sample preparation at 100 mA/g current density,first discharge specific capacity 283.4 mAh/g,first irreversible efficiency 91.21%,and obvious charging and discharging platform.The specific capacity is still 150 mAh/g after 100 cycles at 500 mA/g current density.Then The effects of the amount of carbon coating on Li₂ZnTi₃O₈ surface,the uniformity of coating and the types of coating on the electrochemical properties of Li₂ZnTi₃O₈ were investigated.Firstly,glucose and Cetyltrimethylammonium Bromide?CTAB?were used as carbon and nitrogen sources to study the effects of different carbon content on the morphology,phase and electrochemical properties of the materials.The optimum conditions are as follows:heat treatment temperature 750?,heat treatment time 6 h,the first discharge capacity 267.8 mAh/g and the Coulomb efficiency 100.43%for the sample with 6%glucose coating at 100 mA/g current density.The specific capacity is 226.2 mAh/g after 100 cycles at 500 mA/g current density.Finally,the effects of compound addition and ion doping on the material were investigated.Firstly,a mixture of TiO₂ and Li₂ZnTi₃O₈ was prepared by excess of titanium source TiO₂,and the effects of different TiO2 additions on the properties of the materials were investigated.By forming a supersaturated defect in the crystal arrangement by excess TiO₂,the conductivity of the material is improved,thereby improving the electrochemical performance of the material.Next,the aluminum-doped raw material was used to investigate the effect of different Al³⁺doping amounts on the electrochemical performance of the prepared Li₂ZnTi₃O₈.The preferred conditions are heat treatment temperature of 750°C,heat treatment time of 6 h,and the sample with TiO₂ addition of 10 wt.%at a current density of 100 mA/g,the first discharge specific capacity is 218 mAh/g,and the irreversible efficiency is 79.27%.The specific capacity is 195.2 mAh/g after 100 cycles at 500 mA/g current density.