Lithium Titanate Was Prepared Directly From Ilmenite

Spinel Li4Ti5O12 is a"zero-strain" material, which has been demonstrated to be one of the most promising next-generation electrode materials for its flat charge-discharge plateaus, good cycle performance and low cost. Recently, the main source of titanium for preparation of lithium titanate material is rutile TiO2 and titanium organic compounds. In this paper, we used ilmenite as raw materials to prepare Li4Ti5O12 material, innovatively, realizing the integration of concentrate-materials, shortening the process. The status of titanium resources in China and the acid treatment process, mechanical activation were described in this paper briefly; on the base of the summary of lithium-ion battery and its negative electrode materials, we introduced the structure, properties and preparation methods. Li4Ti5O12 was synthesized by solid-state reaction at high temperature. The related properties of anode materials were investigated by using various electrochemical methods in combination with modern physical testing techniques such as SEM, XRD, and EDS analysis.In recent years, mechanical activation technique is widely used in the enhancement of leaching of minerals. When the minerals is treated by the mechanical forces, the refinement, lattice distortion, lattice disorder and even the non-qualitative occurs, at the same time the activation energy decreases. This work introduced the mechanical activation of ilmenite to the acid leaching, and studied the process of acid leaching ilmenite which was activated by mechanical milling. The results showed that when the ball/ilmenite ratio is 20:1 and the milling time is 2h, the activation is best, resulting in small size, large surface area, increased surface activity and enhanced leaching. Hydrochloric acid was used to leach activated ilmenite and the best leaching conditiona is that the hydrochloric acid concentration is 20wt.%, leaching temperature is 100℃, the ratio of acid and ore is 1.2:1 and leaching time is 2h. Under these conditions, the main elements of Ti, Fe, Mg, Al, Mn, Ca are well separated; Ti and Si were enriched in slag, and Fe, Mg, Al, Mn and Ca in leaching solution. In the process of alkali leaching Ti-rich slag, amorphous SiO2 reacted with NaOH and generated Na2Si03 into solution; when pH value was higher than 14, Si mainly exsits in the form of SiO32- which is highly soluble in water. The best conditions in the first step leaching silicon using sodium hydroxide were that reaction temperature was 110℃, alkali excess coefficient 2.67, reaction time 2h and alkali cincentration 40g/L Under these conditions, Ti and Si elements were well separated and Ti does not dissolve in alkaline solution and existed in solid phase,90.5% of Si into filtrate. After second step leaching, the total leaching rate of Si was 98.7% and achieved a well separation; the second step leaching filtrate returned to the first step leaching which achieved the recycling of resources.We used Li2CO3 as lithium source (lithium salt excess of 2%) Ti-rich slag and the solid material containing titanium after alkaline leaching as titanium source to synthesize spinel Li4Ti5O12 anode material under 850℃for 16h. We comparatively studyed the properties of Li4Ti5O12 anode material sythesised with different sources of titanium. The results showed that the material sythesised with Ti-rich slag contained impurities of rutile TiO2 and Li2(TiSi05); the electrochemical performance was poor but the cycle performance was good; at the rate of 0.1 C and 1C, the reversible specific capacity was 105.1 mAh/g and 76.5 mAh/g, respectively. The material synthesised with the solid material containing titanium after alkaline leaching had a single pure phase of Li4Ti5O12, good crystallization and better electrochemical performance with good cycle performance; at the rate of 0.1 C and 1C, the reversible specific capacity was 138.3 mAh/g and 126.8 mAh/g, respectively. The material synthesised with rutile TiO2 had the reversible specific capacity 163.5mAh/g and 134.3 mAh/g, respectively, at the rate of 0.1 C and 1C. The properties of the material synthesised with the solid material containing titanium after alkaline leaching was not as good as those synthesised with rutile TiO2. The reasons may be that the the former also contains trace silicon and iron impurities and has a coarser grain size.