Study On The Preparation And Modification Of Anode Material Li₄Ti₅O₁₂ For Lithium-ion Batteries

The spinel Li₄Ti₅O₁₂as a“zero strain”material has become a research highlightamong various anode materials. In order to improve the rate performance of Li₄Ti₅O₁₂by modification,in this thesis, Synthesis, improvements structural characterization,surface morphology and electrochemical products of spinel Li₄Ti₅O₁₂were analyzed byX-ray diffractometry, scanning electron microscopy, galvanostatic charge-discharge,electrochemical impedance spectroscopy and cyclic voltammeter testIn the first chapter, gives a brief introduction about the structure and workingmechanism of lithium-ion batteries, the current survey on the spinel Li₄Ti₅O₁₂materialwas introduced and the methods of Spinel Li₄Ti₅O₁₂synthesis and a improve the rateperformance of Li₄Ti₅O₁₂．In the second chapter, we introduce the experimental material and methodes. Thedetailed procedure of coin cell assembling in laboratory is described, as well as thegeneral characterization methods of materials and electrochemical analysis.In the third chapter, the anode materials spinel Li₄Ti₅O₁₂for lithium-ion batterywere synthesized by high temperature solid-state method and triethanolamine assistedsol-gel method. The result shows that Li₄Ti₅O₁₂prepared by the two methods hadperfect spinel structure.When the chemical molar ratio of TEA and titanium was0.8,Li₄Ti₅O₁₂exhibited a relatively good rate capability and cycling stability.At thecharge-discharge rate of1.0C, its discharge capacities were153.03mAh·g-1, respectively.After35cycles, its discharge capacity remained at139.94mAh·g-1and the capacityretention was91.45%.In Chapter4, in order to improve the ionic conductivity of lithium iron phosphatelithium, Li₄Ti₅O₁₂/Ag was synthesized by an electroless deposition method combinedwith thermal decomposition of a mixture of AgNO₃. The results showed that surfacecoating of Ag on Li₄Ti₅O₁₂particle improved its electronic conductivity and thereforeenhanced the performance of the circulation. The discharge capacity of the compositewere137.2mAh·g-1at0.3C rate after35cycles, and the corresponding capacityretention were88.3%, respectively. EIS test proved that surface coating of Ag onLi₄Ti₅O₁₂particle could decrease its charge transfer resistance greatly. In Chapter5, a new composite material Li₄Ti₅O₁₂/Li_1.3Al_0.3Ti_1.7（PO₄）₃was wassynthesized by sol-gel method to enhance the low electronic and ironic conductivity,take advantage of the higher ionic conductivity and lower activation energy ofLi_1.3Al_0.3Ti_1.7（PO₄）₃and the unique advantages of Li₄Ti₅O₁₂. The results show that thesynthesized material is pure spinel phase. The doping with Li_1.3Al_0.3Ti_1.7（PO₄）₃couldincrease the conductivity of the synthesized anode material, decrease Li+diffusionresistance, and dramatically increase the electrochemical performance. The optimaldoping amount in a mass of ratio was3%The Li₄Ti₅O₁₂/Li_1.3Al_0.3Ti_1.7（PO₄）₃sample hada low charge transfer resistance （159.7）, The initial discharge specific capacity is186mAh·g^-1at0.1C,158mAh·g^-1at1C, showing that it has good cycling behavior.