Synthesis Of Zn₂Ti₃O₈ And NiTiO₃ Anode Materials For Lithium Ion Batteries

In recent years, titanium-based materials have been extensively studied as promising anode materials for lithium-ion batteries due to their structural stability during lithium insertion/extraction and high safety. Among Ti-based materials, Li₄Ti₅O₁₂ was successfully used as anode material for its excellent cycling stability and high rate discharge performance. However, the theoretical capacity of Li₄Ti₅O₁₂ is only 175 mAhg-1, other titanates have drawn more and more attention in order to satisfy the demands of high energy density, high rate performance and desirable safety for electric vehicles, while general poor electrical conductivity of titanates limit their electrochemical performance during charge/discharge. In this paper we resport the preparation of zinc titanate, nickel titanate and their application in lithium ion battery by introduction of oxygen vacancies and carbon-coating in suit.1. Pure zinc titanate with face centered structure was synthesized via molten salt method. The main affecting factors of product structure such as molten salt species, titanium zinc ratio and calcination temperature were investigated. It has been found that the product structure can be effectively controlled by changing molten salt species. Zinc titanate prepared from NaCl with KCl have simple cubic structure, while the products obtained from MgCl₂.6H₂O with KCl and Li Cl with KCl have hexagonal structure and face centered cubic structure. How the titanium zinc ratio influenced crystal structure inner defect of product and electrochemical performance were studied. The optimal ratio is 1:1 in which case manifested the best electrochemical performance. How calcination temperature influenced crystallinity, particle size and agglomeration, further influenced electrochemical performance were also studied, the optimal calcination temperature is 600 in which case manifested the best electrochemical performance.2. The introduction of oxygen vacancies?Vo.? has proved to be one of the most promising methods to improve the electronic conductivity and regulate the Li-ion transport and storage performance, Our previous results demonstrated that large amounts of single electron trapped oxygen vacancy and Ti³⁺ formed during the high-temperature dehydration of NTA, in this section we researched the effect of oxygen vacancy on the structure and electrochemical performance of zinc titanate by use NTA as precursor, the results revealed that the zinc titanate sample contains a large amount of single electron trapped oxygen vacancy and Ti³⁺ in the bulk and its surface remains the stoichiometric structure, while no oxygen vacancy exists when use P25-TiO₂ as precursor. The introduction of oxygen vacancies and Ti³⁺ can significantly improve the intrinsic conductivity, it delivers stable specific capacities of 246, 222, 181, 156, 127, and 88 mAh g-1 at a current destiny of 0.1, 0.2, 0.5, 1, 2 and 5A/g and maintains specific capacity of 236 mAh g-1 after 500 cycles at charge/discharge current density of 0.1 A/g. On the basis of introducing oxygen vacancy to improve zinc titanate internal conductive, coating high conductivity carbon can further improve zinc titanate surface conductivity, in order to alleviate carbon exists in discrete state when use additional carbon resources, we use zinc acetylacetonate both as zinc sources and carbon sources for carbon-coating in suit to reduce contact resistance among particles, its specific capacity reached 300 mAh g-1 at charge/discharge current density of 0.1 A/g.3. Pure NiTiO₃ was prepared by hydrothermal and then solid state method, simple solid phase reaction need at least calcination temperature of 1000?, through hydrothermal process at first reduced calcination temperature to 750, thus promote controlling of particle size and morphology. Since electrode materials of LIBs have a high request of crystallinity, morphology and dispersion, we use molten salt as solvent to reduce calcination temperature and shorten the calcination time for controlling the morphology of nickel titanate, due to the limitation of electrical conductivity and grain size of nickel titanate causing obvious fading of its discharge capacity, it delivers specific capacities of 657.5, 228.3, 179, 156.4 and 141 mAh g-1 for first five cycles at a current destiny of 0.1 A/g.