Preparation And Performance Research Of Co（OH）₂/Co₃O₄and Li₄Ti₅O₁₂ Anode Materials For Li-ion Batteries

It is becoming more and more critical for the need of sustainable and clean energystorage owing to the applications of electric vehicles and variety of portable electronicdevices. Li-ion battery, with high energy density, has been widely applied. Currently,most of the commercial anode material is graphite, however, the main disadvantage oflow lithium storage ability has restrict its energy density. Moreover, it can form thelithium dendrite on the electrode surface when it is overcharged, which can makeserious security problems. In this paper, we studied a kind of transformationmechanism anode materials, comparing with the intercalation reaction compounds,transformation mechanism anode materials have higher capacities. The preparation ofnanostructured electrode materials can also improve the electrochemical performance.Spinel lithium titanate is a kind of zero strain material which has long cycle life, thereversible lithium intercalation/deintercalation can almost reach100%. We havesynthesized using different methods, and their electrochemical performances havebeen characterized.We have synthesized Co（OH）₂nanosheets （NSs） and Co3O4nanoparticles （NPs）composite by a facile hydrothermal strategy. The composition, morphology andmicrostructure of the hybrid can be tuned by the reaction time. In this hybrid,Co（OH）₂NSs form a flower-like structure and the Co3O4NPs embedded on theinterlayer surfaces of the Co（OH）₂NSs which could prevent the Co（OH）₂nanosheetsfrom stacking and buffer the local volume changes during cycling. Meanwhile, thisstructure enables a significant reduction of the Li+diffusion path and thus canexpedite the ion transport, facilitates the infiltration between electroactive materialsand electrolyte. The ordered nanostructure of Co（OH）₂NSs/Co3O4NPs hybridmanifests significantly enhanced Li storage properties, including long cycle life andsuperior rate performance. When it is tested at58mA g-1, the capacity can reach1452mAh g-1, and the capacity reduces slightly after40cyles. We have synthesized Li₄Ti₅O₁₂using liquid-phase method and solid-state method,through the carbon doped or coating methods to improve the electric conductivity.PVP was used to modify the materials morphology and graphitic oxide was used toimprove the electric conductivity, then the transportation of ions and electrons wasaccelerated. In the solid-state method, carbon was used to coat on the surface of TiO2,then the high temperature sintering was employed. The coating layer can not onlyimprove the electric conductivity, but also alleviate the growth of the particles in theprocess of heat treatment. After1000charging and discharging cycles, the capacityretention can reach to82.2%.