Preparation And Properties Of Li-ion Battery Anode Materials Lithium Titanate

As the lithium ion batteries are widely used in the widespread portableelectrical devices, and almost all the commercial anode materials are carbonmaterials. However, the irreversible capacity of carbon is considerable, and thereare also potential dangers of carbon anode. Spinel type lithium titanate (Li₄Ti₅O₁₂)is the most attractive candidate for anode of lithium ion batteries. When used asanode, the structural change of lithium titanate after Li+insertion is negligible,because the lattice parameters of this change are less than0.5%. Comparing withcarbon anode, the Li₄Ti₅O₁₂possess a very long life, a very flat charge-dischargevoltage platform and also a high safety.Pure lithium titanate and the modified ones were synthesized by solid statecomposition in this thesis. And sorts of properties of the Li₄Ti₅O₁₂and modifiedones were tested. Concretely, the temperature and time of composition, theparameters of ball milling and different lithium sources of the pure lithium titanatewere studied in detail, then doping and composition were introduced to modify thepure Li₄Ti₅O₁₂. The experiment focused on the relation between the experimentalconditions and the properties of the final products. The crystal structure ofLi₄Ti₅O₁₂was described by XRD and the morphology was studied via SEM, thenthe size distribution of Li₄Ti₅O₁₂particle was analyzed by a laser particle sizeanalyzer. Furthermore, the electrochemical performances were researched in detailby the battery test system. The results were as follows:1. The results of the electrochemical test of the pure lithium titanate showedthat the influences of the temperature and time of the sintering were notable. Andthe product which presintered at750℃for6h and then sintered at850℃for18hpossessed the best performance. A higher or lower temperature would lead toimpure products and disappointed performances. And also the time and the kind ofdispersant played very important roles in the ball milling. And the product whichball milled with deionized water as dispersant for12h did the best.2. AgNO3, TiO2and Li2CO3were used as raw materials to composite the Agdoped lithium titanate at first. The first discharge capacities of the doped productswere promoted, the performance of the one which doping quantity was0.5wt%wasthe best among the doped products, and the first discharge capacity at0.5C of it was153.6mAh/g. The doping is very simple and practicable, and the only changewas the AgNO3as additive to the raw materials.3. The Li₄Ti₅O₁₂and Ag composite was realized through the compositionwhich used the Li₄Ti₅O₁₂of the most excellent synthesis and AgNO3as startmaterials and co-sintering at450℃for4h to get the Li₄Ti₅O₁₂/Ag products. Sincethe addition of Ag, the conductivity of the products was promoted intensively, andalso the electrochemical performances at high currents. The most attractive productwas the one whose content of AgNO3in the raw materials was8wt%, the firstdischarge capacity of it at0.5C was191.6mAh/g, and the first discharge capacity at10C was142.5mAh/g.4. In order to promote the capacity of Li₄Ti₅O₁₂, SnO₂was introduced tocomposite with pure Li₄Ti₅O₁₂by solid state composition. Comparing the series ofLi₄Ti₅O₁₂/SnO₂, the one of which SnO₂was15wt%of the weight of raw materialhad the best performance, the first discharge capacity at0.5C of Li₄Ti₅O₁₂/SnO₂（15wt%） was442mAh/g, and the capacity maintained at220mAh/g after10charge-discharge cycles at this current, that meant the modification was effective.