Preparation And Electrochemical Properties Of Li₄Ti₅O₁₂as A Kind Of New Energy Materials

As a new generation green battery, lithium ion battery has been widely used inportable electron apparatus and vehicles since1990s, due to its promising features,such as high voltage, low self-discharge rate, little volume/light weight and nomemory effect. State-of-the-art lithium secondary batteries compose of agraphite/carbon-related anode, which has serious safety problems for large-sizeapplications. Due to the low lithium intercalating voltage of approximately100mV（vs. Li/Li⁺）, highly reactive metallic lithium forms easily under fast charge rate, whichwill deposition the surface of electrode and bring the high risk to react with theelectrolyte or highly charged cathodes.Recently, new energy material Li₄Ti₅O₁₂has attracted the intensive investigationsbecause it is a “zero strain” material with low price, good cycle performance,extremely flat charge and discharge plateaus, and so on. Spinel Li₄Ti₅O₁₂has a hightheoretical capacity （175mAh/g） and voltage （about1.5V vs. Li/Li⁺）, which has beendemonstrated to be one of the most potential anode materials.In the present work, Li₄Ti₅O₁₂powders were first successfully synthesized by asol–gel method using citric acid as a chelating agent and fuel. The effect of amount ofchelating agent, calcination temperature and time on the electrochemical performanceof as-prepared product was systematically investigated. Results showed that thesample synthesized at700℃for8h with oxalic acid to lithium molar ratio R=1.0yielded the optimum condition to give the best performance. The as-prepared samplewas well-crystallized single-phase and well dispersed with the particle size from10to200nm. On the charge/discharge procedure of0.5C，the initial specific dischargecapacity of such sample was155.4mAh/g and could keep131.1mAh/g after50cycles, resulting the retention rate in discharge capacity was84.4%. Furthermore, twice hydrothermal ion exchange method was also used tosynthesize spinel Li₄Ti₅O₁₂. The TEM observations show that the as-prepared samplehas nanolayer structure. The galvanostatic charge-discharge test showed that samplescalcined at400,500,600,700and750℃, had the discharge capacities of108.4,129.1,136.9,160.3and148.7mAh/g for the first cycle，respectively. For thesample calcined at700, the capacity retention were90.6%,90.0%,93.4%,95%at0.1,0.2,1,2after20cycles, and the corresponding discharge capacitywere174.2,167.7,155.8and149.1mAh/g.