Nano-sized Li₄Ti₅O₁₂ Anode Material Prepared By Solid State Reaction And Its Electrochemical Performance

As one of the most promising anode materials for lithium-ion batteries, spinel Li4Ti5O12has been widely studied recently. Researches showed that the high-rate charge/discharge properties of nano-sized electrode materials Li4Ti5O12will get improved through optimized synthesis method or selecting appropriate titanium source and lithium source as reagent. This work concentrates on the influence of different titanium sources to its synthesis conditions during solid-state reaction and electrochemical performance. This thesis mainly includes two aspects:(1) Titanium sources (TiO2) of different morphology and size was synthesized by solvothermal method. Through the analysis of XRD and SEM, we have prepared samples of different crystal phases and morphology from the combined impact of the amount of tetrabutyl titanate (Ti(OC4H9)4) and reaction time. The samples’morphology changed from no special morphology to flower-like ball structure, ended as axiolitic structure with the increasing of reaction time. The flower-like ball structure, which was formed during the reaction, was unstable in hot solvent. The unstable flower-like ball structure dissolves slowly as the reaction goes. Stable axiolitic structure was the final morphology of samples. The existing time of lower-like ball structure was determined by the adding amount of Ti(OC4H9)4, and the less the adding amount of Ti(OC4H9)4, the longer it exists. The flower-like ball structure TiO2was assembled by thin nanosheets, which assembled by the rod structural framework with asymmetrical grown nanoparticle on the surface. High-resolution SEM analysis proved that the rough surface of final axiolitic structure TiO2was packaging by mini-sized nanocrystal, and the pore structure formatied during the packaging of nanocrystal.(2) Nanosized spinel Li4Ti5O12electrode materials was synthesized by axiolitic structure titanium dioxide (A-TiO2) synthesized in our lab and commercial titanium dioxide (C-TiO2) though solid-state reaction. The results indicated that the particle size and microstructure of titanium source TiO2influence the synthesis condition and the final particle size of Li4Ti5O12-Pure spinel A-Li4Ti5O12-800with particle size180nm was synthesized by special structure,150nm sized A-TiO2as titanium source and unexcessive lithium carbonate (Li2CO3) as lithium source at800℃. The corresponding initial capacity were164.0and129.6mAh/g at1and10C and it remains95.1%at1C after100cycles. The ratio characteristics and cycle stability are better than the Li4Ti5O12anode materials with larger particle size. After the test of repeatedly cycling and high ratio charge/discharge, the complex interior boundary and electrode polarization formed, which will increase the impedance. Combined with the view of energy and the analysis of the electrochemical test, we came to a conclude that the increased impedance was the main reason for the decrease of specific capacity for Li4Ti5O12as anode material of lithium-ion battery.