Step In The Hydrolysis Of Synthetic Spinel Li <sub> 4 </ Sub> The Ti <sub> 5 </ Sub> O <sub> 12 </ Sub> Lithium-ion Battery Anode Material

As the Zero-strain lithiation and lithiation/de-lithiation material, the spinel Li₄Ti₅O₁₂ shows excellent electrochemical properties, such as stable structure, good cycle performance, long working life, safe and non-pollution. Thus, it has become one of the most prospective Li-ion battery anode materials. In this paper, the well-crystalized spinel Li₄Ti₅O₁₂ with good performance was synthesized using hydrolysis method. The conditions for the synthesis of the Li₄Ti₅O₁₂ were optimized and the prepared samples were characterized by means of XRD, DSC-TGA, SEM, etc., for the purpose of improving the performance of the materials.The standard Gibbs free energies of formation of Li₂Ti₃O₇,Li₄Ti₅O₁₂ and Li₄TiO₄ were estimated using double parameter model and congeneric linearity rule. Theφ-pH diagrams of Ti-H₂O and Li-Ti-H₂O system for different concentrations were drawn at 298.15K. The results showed that from the view of thermodynamics, Li₄Ti₅O₁₂ has comparative lager thermal stable area in aqueous solution, indicating the feasibility of the synthesis of Li₄Ti₅O₁₂ by hydrolysis from TiCl₄ solution.A precursor of Li₄Ti₅O₁₂ in which Li and Ti were chemically combined was successfully synthesized using by one-step hydrolysis method to TiCl₄ and LiOH·H₂O were used as raw materials. The samples were subsequently subjected to heat treatment. The effect of hydrolysis and heat treatment parameters on the samples' structure and electrical performance were studied. The results showed that pure spinel Li₄Ti₅O₁₂ can be obtained from the precursor synthesized with 1.0-3.0mol·L^-1 initial LiOH solution by hydrolysis precipitation following fully washing. The feeding Li/Ti molar ratio was 4.8. The hydrolysis was carried out at 50-90℃for 1-3h; The heat treatment was conducted at 800℃for 6h. The synthesized sample has pure phase, homogeneous composition, and uniform particle size. The average particle size is approximately 1 urn.The electrochemical tests showed that the material obtained has stable charge and discharge voltage around 1.55V and excellent cycle performance, as typical spinel Li₄Ti₅O₁₂ shows. The sample obtained from the precursor synthesized with a 1.0 initial LiOH solution at 70℃for 3h has the highest first reversible specific capacity of 130.1 mAh·g^-1. After 50 cycles at 0.1C rate, the specific capacity maintained at 109.7 mAh·g^-1. At a higher rate of 0.5C, the specific capacity is 99.0 mAh·g^-1 with current efficiency of 100.4% after 100 cycles. It was approved that one-step hydrolysis is a prospective method for the synthesis of spinel Li₄Ti₅O₁₂ with an atomically homogeneous distribution of elements.