Metal Oxide Materials For Lithium-ion Batteries:Synthesis And Electrochemical Performance

Limited by its low theoretical capacity and charge/discharge rate,traditional commercial carbon anode materials are becoming more and moredifficult to meet the needs of battery industry, and metal oxide are consideredto be a very promising alternative. Previous research shows that metal oxideshave good electrical activity and two or three times larger theoretical capacitythan carbon anode materials, so they have attracted more and more interest inboth fundamental and practical research. However, there are still manychallenges in their practical application, such as the large change in volume,the serious aggregation or pulverization of active particles duringcharge–discharge, and the poor conductivity of the transition metal oxides.In this thesis, to solve the above problems, three methods including themagesiation, different metal oxide composition, and morphology control havebeen used to improve target materials electrochemical performance. Therelative mechanisms of the improvement have also been studied. Theseattempts will contribute to the study of metal oxide used in lithium batteries.1． Facile Synthesis of Magnesiated α-MoO3and its ElectrochemicalPerformance in Li-ion Batteries.A facile approach to prepare magnesiated α-MoO3was developed by aprecipitation method. The magnesiated α-MoO3cathodes had higherdischarge/charge capacity, good capacity retention and high-rate performancecompared to non-magnesiated α-MoO3cathodes. This could be attributed toits enlarged layer structure, a larger materials/electrolyte contact area, strainaccommodation induced by the volume change, and a good path way for Liion insertion/deinsertion. The results showed that the Mg ion treatmentmethod would be a promising way to improve the performance enhancementof cathode materials in high-power Li-ion batteries.2．NiO/Co3O4Composite Nanosheets as High Performance Li-ion BatteryAnode Materials. NiO/Co3O4nanosheets have been synthesized at low temperature for thefirst time. By controlling the ratio of NiO, not only the size of the nanosheetscan be controlled, the electrode’s conductivity and stability have been greatlyimproved. The material showed stable capacity retention during cycling evenat large current rate. The novel NiO/Co3O4might be promising candidateanode materials in high performance Li-ion batteries.3．Preparation of Flower-like SnO2Nanostructures and their Applicationsin Lithium Storage.Hierarchical flower-like SnO2nanospheres have been prepared by onestep hydrothermal reaction with surfactant-free. A possible growth mechanismis proposed. The flower-like SnO2nanostructures were used as anodematerials for Li-ion battery and had achieved great results. The high specificsurface area of the flower-like SnO2nanospheres can provide moreelectrochemical active sites for Li storage, and the3D nanostructured filmscomposed of this nanostructure facilitate the diffusion of electrolyte.Furthermore, the short rods on the nanospheres may provide a buffer toalleviate volume change during the alloying and dealloying reactions betweenSn and Li. The superior properties achieved here suggest that the as-preparedhierarchical flower-like SnO2nanostructures have potential application inLi-ion battery.