Preparation, Structure And Electrochemical Properties Of Lithium Titanate Cathode Materials

Rechargeable lithium-ion battery（LIB） has been generally regarded as one of the most promising power batteries for electric vehicles（EVs） and hybrid electric vehicles（HEVs） or energy storages for portable electric devices due to its high energy density.Developing anode materials with high safety and excellent electrochemical performance is important challenges for lithium-ion batteries.In particular, Li₄Ti₅O₁₂ has been considered as one of the most promising alternatives for the commercial anode materials owning to its high potential plateau（around 1.5 V vs. Li/Li+）, high structural stability, and excellent cycling performance. Unfortunately, Li₄Ti₅O₁₂ itself also has the obvious shortcomings,its high rate application was limited by the poor electric conductivity（about 10-13 S·cm-1） and low Li-ion diffusion ability.In this paper, based on the first-principles calculations, the thermodynamic stabilities, electronicproperties, intercalation kinetic and surface morphologiesof spinel Li₄Ti₅O₁₂ were investigated in detail.Pure Li₄Ti₅O₁₂ materials have been synthesized by solid-state method and hydrothermal synthesis to investigate into preparation factors-dependent physical and chemical properties. By solid-state method, nanowires LTO-S-4 powers fabricated with precursor of B-TiO2 showed superior high rate characteristic. It is represented by adischarge capacity of 189.1mAh g-1at a high rate of 10 C. By hydrothermal synthesis, nanoparticle LTO-L-1 prepared with ethanol solution as solvent reveals a higher capacity of 220 mAh g-1 at a charge-discharge rate of 0.5C.We have predicted that NaLiTi₃O₇ can provide a high-speed channel of lithium ions for Li₄Ti₅O₁₂ and optimize the crystal structure of Li₄Ti₅O₁₂, thereby improving the electrochemical performance by calculating the energy of lithium ions transport of NaLiTi₃O₇ and Li₄Ti₅O₁₂. Li₄Ti₅O₁₂-NaLiTi₃O₇ composites were successfully synthesized by hydrothermal method. Compared with pure Li₄Ti₅O₁₂, Li₄Ti₅O₁₂-NaLiTi₃O₇ composites related to improve electronic conductivity and lithium ion diffusivity. Li₄Ti₅O₁₂-NaLiTi₃O₇ composites materials achieves discharge capacities of 218mAh·g-1 and the capacity retention reached as high as 90% after 100 cycles at 10 C rate.