Modification Research And Application Of Li₄Ti₅O₁₂

In this paper, the orthogonal experiment method was used to investigate the "Two-Step" solid state synthesis of Li4Ti5O12/graphene,"Two-Step" microwave solid state synthesis of Li4Ti5O12/graphene and "One-Step" solid state synthesis of Li4Ti5O12/C composites. To characterize the composites, the TG-DTA, XRD, SEM, particle size analysis, room temperature constant current charging and discharging, AC impedance and cyclic voltammetry were used. After all of these, the composites were used as anode materials of lithium ion batteries, and investigated the best experimental conditions to promote the electrochemical performance of the materials.At the first in this study, the orthogonal experiment method was used to investigate the "Two-Step" solid state synthesis of Li4Ti5O12/graphene and to explore the best synthesis process. The final results show that the optimum process:the precursor was calcined at800℃for6h in N2atmosphere to form Li4Ti5O12microspheres, and then5g of Li4Ti5O12microspheres was mixed with10mg of graphene, and then calcined at800℃for2h in N2atmosphere. The initial discharge capacity of the resulting material was229.8mAh/g and the capacity retention remain96.6%after10charge-discharge cycles under the0.1C magnification.In addition, the "Two-Step" microwave solid state synthesis of Li4Ti5O12/graphene was used and the best condition was explored by experiment method. The final results show that the optimum process:the precursor was calcined at900℃for4h in N2atmosphere to form Li4Ti5O12microspheres, and then5g of Li4Ti5O12microspheres was mixed with30mg of graphene, and then calcined at800℃for2h in N2atmosphere. The initial discharge capacity of the resulting material was152.3mAh/g and the capacity retention remain95.5%after10charge-discharge cycles under the0.1C magnification.Finally, I used the "One-Step" solid state reaction to synthesis Li4Ti5O12/graphene composites and optimized the experimental conditions. The optimum process was given as: the precursor was mixed with citric acid as a carbon source with carbon content of10%, then the mixture was calcined at800℃for8h in N2atmosphere. The initial discharge capacity of the resulting material was162mAh/g and the capacity retention remain97.5%after10charge-discharge cycles under the0.1C magnification.This contribution utilizes solid-phase microwave method to integrate Li4Ti5O12/graphene, the integrated material have larger particle size, less discharge volume and poorer recycle performance than material integrated in traditional way, but the proposed technique can save plenty of time and energy, which make the method have a lot of potential with respected to cost and development.Comparing three kinds of integrated material, we can conclude that "Two-Step" solid state synthesis of Li4Ti5O12/graphene outperforms others regarding to Electrochemical properties and stability of the product,"Two-Step" microwave solid state synthesis of Li4Ti5O12/graphene has poor electrochemical properties and large particle size and "One-Step" solid state synthesis of Li4Ti5O12/graphene has unstable electrochemical properties and obvious difference in electrochemical properties.