Study On Synthesis Of ?-LiFeO₂ Cathode Material For Lithium-ion Batteries By Hydrothermal Stripping Method

The continuous development of new energy is the important foundation of human sustainable development. Due to its so many advantages, lithium-ion battery has received considerable attention. The cathode materials play a crucial role in improving battery performance and reducing the cost. Because of possessing rock salt structure similar to that of LiCoO₂, rich sources of raw materials, environmental protection?non-toxicity and high theoretical specific capacity?282 mAh·g-1?, the LiFeO₂ has attracted widespread attention. Li FeO₂ has a variety of structures, one of which is a kind of ?-Li FeO₂ with cubic rocksalt structure. The ?-Li Fe O₂ synthesized via different synthesis methods displays different electrochemical performance. Synthesizing nano-sized materials is an important method to improve the electrochemical performance.In this paper, we develop a novel method based on hydrothermal stripping according to coupling principle, and have successfully synthesized nano-?-LiFeO₂. The samples were directly synthesized by hydrothermal stripping method between organic phase, which prepared with industrial naphthenic acid and iron salts and aqueous containing Li OH. The samples were detailedly studied by X-ray diffraction?XRD?, scanning electron microscopy?SEM?, transmission electron microscope?TEM?, laser particle size analyzer. The results show that the molar ratio of Li/Fe in reaction, the stripping temperature, the stripping time and the amount of different surfactant all have important influence on the structure, composition, morphology and particle size of the samples. The main contents and results are as follows:Target samples were synthesized starting with iron???-loaded organic phase and lithium hydroxide aqueous solution via hydrothermal stripping technology. Studies show that the final product greatly depends on the molar ratio of Li/Fe in reaction system, only Li/Fe higher than 29 can synthesize pure phase ?-Li Fe O₂. The product was also greatly influenced by the stripping temperature, and when the temperature is above 230 °C, the samples were pure phase ?-LiFeO₂ without impurity. Reaction time has an obvious effect on the morphology of the product, and with the extension of reaction time, the product eventually forms a quadrangle crystal. The optimal reaction condition is that Li/Fe is 29, reaction time is 2 h under 230 °C and heat preservation time is 5 h under 80 °C. The product synthesized under optimal condition is pure nano-?-LiFeO₂ particle of 150 nm around, which has high crystallinity and good dispersion.Herein, we study the effect of surfactants on ?-LiFeO₂ synthesized by hydrothermal stripping method, which were CTAB and SDBS. The results show that cationic surfactant CTAB can control the particle size of ?-LiFeO₂ and when adding 2 mmol/L CTAB to the reaction system, the particle size of ?-Li FeO₂ is about 130 nm around, lower than that of non-added CTAB samples and the degree of crystallinity of the sample was also enhanced; in the experimental concentration range, anion surfactant SDBS has no obvious influence on the morphology and particle size of the products.