Study On The Hydrothermal Synthesis Of Lithium Titanate Electrode Materials And Their Doping Modificatio

Li₄Ti₅O₁₂ material has a cubic spinel structure,low lithium intercalation potential（about 1.56V）,three-dimensional ion diffusion channels,and almost no strain during lithium ion de intercalation.It is a"zero strain"electrode material with broad application prospects.However,this material also has a low theoretical specific capacity（about 175 mAh/g）and poor charging and discharging performance at high magnification.Therefore,this paper conducts modification research on the above shortcomings of the material,and the experimental results show that after modification,the theoretical specific capacity and cyclic performance of Li₄Ti₅O₁₂ material are significantly improved.The main research content and achievements of this article are as follows:（1）Sr-doped Li₄Ti₅O₁₂ material was prepared with Sr element doping amounts of 0.025,0.05,and 0.075（moral ratio,marked as 25-Sr,50-Sr,and-75 Sr,respectively）.The research results indicate that Sr element successfully doped into the lattice of Li₄Ti₅O₁₂ material and improved the electrochemical performance of the material（especially the first charge discharge specific capacity）.At 0.2 C,the first discharge capacity of 25-Sr reached 215.08 mAh/g,much higher than the discharge capacity of Li₄Ti₅O₁₂ under the same conditions（163.17 mAh/g）;While increasing the first discharge capacity,doping also improves the cycling performance of the material:at a1C rate,the capacity retention rate after 100 cycles of 25-Sr is 92.70%;At a high magnification of 10C,the capacity retention rates for 200 and 500 cycles of 25-Sr are92.32%and 80.02%,respectively.（2）The F-doped Li₄Ti₅O₁₂ material was prepared with hydrothermal method,and the F-doped amounts were 0.1,0.2,0.3（moral ratio,labeled as F-01,F-02 and F-03,respectively.）The test results showed that the F-doped Li₄Ti₅O₁₂ material entered the lattice interior,while introducing rutile TiO₂ heterophase.The electrochemical performance of the doped material has been improved,among which F-01 has the best electrochemical performance,with a specific capacity of 218.88 mAh/g at 1C.After200 cycles,there is still 204.15 mAg/g,with a capacity retention rate of 93.27%,which is higher than 85.40%of pure LTO;Cycling 500 times at a high magnification of 10C resulted in a capacity retention rate of 88.74%,which is higher than 66.16%of pure LTO.Subsequent EIS impedance tests showed that F-doping reduced the charge transfer resistance of the material,increased the lithium-ion diffusion rate,and improved the electrochemical performance of the material.（3）Sr²⁺-Mg²⁺co-doped Li₄Ti₅O₁₂ material was prepared with hydrothermal method.Based on a fixed Sr doping amount of 0.05,the Mg doping amounts were0.01,0.02,0.03（moral ratio,labeled as Sr-Mg 1,Sr-Mg 2,Sr-Mg 3,respectively）,with the doping site at the 8a site of Li.The co doping of double cation ions promotes the improvement of the electrochemical performance of the material,among which the Sr-Mg 2 sample has the best electrochemical performance,with a charge discharge capacity of 214.21 mAh/g at a rate of 0.5C.After rate testing,the capacity is 206.21mAh/g,and the capacity retention rate is 96.26%;Cyclic testing was conducted at a high magnification of 5C,and its initial specific capacity was 184.92 mAh/g.After 500cycles,it can still maintain 164.19 mAh/g,with a capacity retention rate of 88.71%.Subsequent EIS tests showed that co doping reduced the charge transfer impedance（Rct）of the material,increased the lithium ion diffusion rate,and played a key role in improving the electrochemical performance of the material.