Preparation And Research Of LiV₃O₈ Cathode Materials Appliedin Lithium-ion Batteries

Advanced rechargeable lithium ion batteries are regards the best selection of the consumer electronics because of a favorable combination of voltage, energy density, cycling performance. Cathode material as an important component of the lithium ion battery plays an important role in electrochemistry performance of lithium ion batteries. Layered type LiV3O8 are attracting widespread attention, due to the low cost, large specific capacity, high discharge rate and long cycle life. The electrochemical properties of LiV3O8, such as specific capacity, rate capability and cycling efficiency are strongly influenced by preparation method. In this paper, LiV3O8 was synthesized by hydrothermal process and sol-gel method, and LiV3O8 coated by ZnO achieved by a simple and easy way. The main work of paper are as follows:Hydrothermal process is a chemical reaction, which is under certain temperature and pressure in aqueous solution. The material prepared by this methods are pure and fine. LiV3O8 was prepared by hydrothermal process. Based on the experimental results, the effects of aqueous ammonia in this work have been proved. The influence of heat treatment temperature and hydrothermal process temperature on structure, morphology and electrochemical properties has also been studied. Experimental results manifest the products prepared at 200℃ in hydrothermal process and followed by 400℃ heat treatment exhibits a better electrochemical behavior than its counterpart prepared at other condition. Its initial discharge capacity is 258.3 mAh·g-1, and still maintains 180.4 mAh·g-1 after 30 cycles at 0.1C at the voltage range of 1.8-4.0V.LiV3O8 was prepared by sol-gel method with H2O2 and oxalic acid respectively. This methods are controllable and the products are uniform. Based on the experimental results, the effects of hydrogen peroxide and oxalic acid in this work are discussed. The influence of heat treatment temperature and carrier on structure, morphology and electrochemical properties has also been studied. Experimental results show the products was prepared by sol-gel method with oxalic acid are better than hydrogen peroxide, exhibits a better electrochemical cycle stability. In the preparation of LiV3O8 by sol-gel method with oxalic acid, we must avoid the heat treatment temperature near 450℃. The experimental results manifest the products prepared a by sol-gel method with oxalic acid and followed by 500℃ heat treatment exhibits a better electrochemical behavior than its counterpart prepared at other condition. Its initial discharge capacity is 196.2 mAh·g-1, and still maintains 192.7 mAh·g-1 after 30 cycles at 0.1C at the voltage range of 1.8-4.0V. The retention rate of discharge capacity are 98% after 30 cycles.LiV3O8 coated by ZnO achieved with the process of hydrolysis and thermal decomposition of zinc acetate. The forming process, existence form and distribution of ZnO are discussed. The influence of heat treatment temperature and percentage of ZnO on structure, morphology and electrochemical properties has also been studied. Experimental results indicates the proper percentage of ZnO could improve the charge and discharge cycle stability of LiV3O8, and the products coated with 10 wt.% ZnO exhibits a better electrochemical behavior than its counterpart prepared at other condition. Its initial discharge capacity is 215.8 mAh·g-1, and still maintains 158.3 mAh·g-1 after 30 cycles at 0.1C at the voltage range of 1.8-4.0V.