Preparation And Electrochemical Performance Of Heteroatom-doped Li₄Ti₅O₁₂ Base Anode Materials For Lithium Ion Batteries

Spinel lithium titanate(Li₄Ti₅O₁₂)as a structural stable anode lithium ion battery material,has become one of the hottest of anode materials due to its zero strain during the electrochemical reaction process.However,Li₄Ti₅O₁₂2 exhibits low electronic conductivity and low lithium-ion diffusion coefficient limit its act as large-scale energy storage application.In this dissertation,Ce/La doped Li₄Ti₅O₁₂ nanosheets and N-Li₄Ti₅O₁₂/Anatase/Rutile three-phase nanocomposites that owns much grain boundary and structure defects which calcined under NH₃ atmosphere were prepared via a one-step simple hydrothermal method and followed by moderate heat treatment,and research the impact of structure defects and multiphase in regard to the electrochemical performance of Li₄Ti₅O₁₂through different characterization methods and electrochemical performance tests,the main research contents are as follows:Ce/La doped Li₄Ti₅O₁₂ nanosheets have been successfully prepared via a simple hydrothermal method and followed by heat treatment,using titanium tetraisopropoxide as titanium source and LiOH·H₂O as lithium source,while CeCl₃·7H₂O or LaCl₃·7H₂O as dopants.When use Ce/La doped Li₄Ti₅O₁₂ as anode lithium-ion battery materials,studied the lithium storage properties where both in Li-half and Li₄Ti₅O₁₂/LiFePO₄ Full cell.And it also exhibits super rate capability and cycle performance.It found that the rare earth elements doped into Li₄Ti₅O₁₂2 lattice can improve the intrinsic conductivity and lithium-ion diffusion coefficient.Therefore,the electrochemical performance showed that Ce/La doped Li₄Ti₅O₁₂ can deliver a specific capacity of 123 and 113 mAh g^-1,respectively.Even at the high current density of 20 A g^-1.In addition,the cycle retention rate of the two samples is about 86%,when cycles 1000 times within the current density of 5 A g^-1.N-Li₄Ti₅O₁₂/Anatase/Rutile Ternary-phase nanocomposites（denoted as N-LTO/A/R）and A-Li₄Ti₅O₁₂/Anatase/Rutile Ternary-phase nanocomposites（denoted as A-LTO/A/R）have been obtained via nonstonichiometric ratio of lithium reaction and optimized heat treatment,using titanium tetraisopropoxide as titanium source and LiOH·H₂O as lithium source.The electrochemical performance shown that it can deliver a specific capacity of150 mAh g^-1 at the current density of 10 A g^-1.Meanwhile,it also found that the more and more grain boundaries not only provide lithium storage sites,but also provide a faster Li⁺transport channel.Finally,when assembled the Li-matched N-LTO/A/R vs.LiFePO₄ as a full cell battery.It has a flat and high smooth discharge voltage platform and excellent rate performance(delivered a specific capacity of 124 mAh g^-1 at 1 A g^-1).