Research On The Preparation And Electrochemical Performance Of Titanium-based Anode Material

Lithium titanate battery has the advantages of better safety and stability than other lithium batteries,excellent fast charging performance,long cycle life,good wide temperature resistance,etc.,and can meet the requirements of high safety and long cycle energy storage devices.However,its low capacitance(theoretical capacity 175 m Ah g^-1)and electrical conductivity hinder the large-scale commercial application of lithium titanate batteries,so it is imperative to improve its performance such as capacity.Usually,the modification of material properties is most prominent and effective through doping.In this paper,lithium titanate anode materials were prepared by different methods,the influencing factors in the preparation process were further optimized,and the optimized lithium titanate samples were doped with different elements such as Zr,Cr,Co,etc.The optimal doping element for graphene oxide coating treatment was studied,which effectively improved the electrochemical performance of lithium titanate anode material.The main research contents and results are as follows:（1）By comparing the phase structure,microstructure and electrochemical performance under different preparation methods,it is concluded that the LTO samples calcined for 12h by freeze-drying method（HNO₃）with Li/Ti ratio of 0.840 at 800℃show the best crystallinity and electrochemical performance.In the microscopic morphology,the particle size is small,the distribution is uniform,and the hierarchical characteristics.The first charge and discharge capacity and the first coulomb efficiency are 173.8/182.6 m Ah g^-1 and 95.2%,respectively,while the rate performance at 0.1C,1C,2C,5C,10C and then back to 1C are178.7,172.5,156.4,142.6,123.1 and 171.2 m Ah g^-1.The reversible capacity of 170.3 m Ah g^-1can still be maintained after 100 cycles at 1C.（2）The lithium titanate prepared in the optimal state was doped with Zr,Cr and Co elements.After doping,part of Ti⁴⁺in LTO was reduced to Ti³⁺,and oxygen defect sites appeared.The concentration of electron holes increased,which improved the conductivity of the material.at 0.5C,1C,2C,5C,10C and 20C,the reversible capacities of LTO-0.1Zr are286.8,258.5,235.4,196.2,151.5 and 119.6 m Ah g^-1,respectively,and the reversible capacities at 1C are 257.6 m Ah g^-1.The LTO-0.1Zr,LTO-0.075Cr,LTO-0.125Co and pure LTO of 500 cycles at 10C are 145.7/137.8,129.9/121.1,133.2/125.1 and 127.8/98.8 m Ah g^-1.The capacity retention rates were 94.6%,93.4%,93.9%and 79.8%,respectively.（3）In order to further modify the conductivity of LTO material,the single doped Zr element with the best performance in the previous chapter was coated with graphene oxide.According to the analysis of the results,the rate capacities of LTO-0.1Zr@GO composites at0.5,1,2,5,10C and back to 1C are 396.5,347.6,330.2,295.4,263.6 m Ah g^-1 and 370.2m Ah g^-1,respectively.In addition,the specific capacities of LTO-0.1Zr@GO,LTO-0.1Zr and pure LTO are 327.6,252.6 and 160.2 m Ah g^-1,respectively,after 200 cycles at 1C.The specific capacities of LTO-0.1Zr@GO,LTO-0.1Zr and LTO after 1000 cycles at 5C are310.2,185.8 and 147.8 m Ah g^-1,respectively.The results show that the electrochemical properties of the materials can be effectively improved by doping and coating.