Application Of Vacuum Sintering Method In Preparation Of Lithium Ion Battery

Owing to its advantages of high energy density, low price, low self-discharge, no pollution and no memory effect, Lithium ion battery is widely used in in practice and obtain great success in business.In this paper, on the basis of reading a large number of literature, LiFePO4 and Li4Ti5O12 materials were synthesized by vacuum sintering method, respectively. The two kinds of materials were characterized by X-ray Diffraction(XRD), Scan electron microscope(SEM) and investigated by constant current charge/discharge test, and then we examined the different synthetic conditions on the physicochemical properties and electrochemical properties of the two kinds of synthetic materials.First, we compared the differences of LiFePO4/C composite materials prepared by the traditional solid-state reaction method and the vacuum sintering method. The LiFePO4/C was synthesized by two kinds of sintering method with dry ball-milling, Li2CO3, FeC2O4·2H2O NH4H2PO4 and citric acid were used as raw materials. By changing calcine time and calcine temperature and so on, the best synthesis condition has been found. The experiment results showed that samples prepared under vacuum and argon atmosphere both represent a single olive crystal structures, but the LiFePO4/C under vacuum delivered a higher discharge capacity, moreover, the particles is smaller and more uniform, which indicated that the LFP synthesized by sintering under vacuum is more feasible and better.And dry ball-milling 6 houres and calcine 12 hours under vacuum with the temperature of 650℃.In this way, the discharge capcity of 0.1C is 144.4mAh/g, even after cycling 20 times at 2C, LiFePO4/C material prepared under vacuum can still provide discharge specific capacity of 123.5 mAh/g.Then, Li4Ti5O12/C anode materials were synthesized by vacuum sintering method with Li2CO3, TiO2, citric acid as the raw materials. The results demonstrated that the characteristic of Li source, sinter temperature and the situation of doped carbon or undoped had important influence on the electrochemical properties of the materials. The experiment results showed that the best synthesis condition is:When lithium is excessed less than 5% and 10% carbon dopped, Li4Ti5O12 material exhibits the best performance which is prepared by vacuum sintering method with 600℃ for 3h.Battery electrodes are manufactured by sintering molding method. The sintered electrodes need high porosity and good uniformity, to increase uniform impregnated active substances. The obtained electrodes have a high capacity and stable performance. Because vacuum sintering furnace contains few oxygen nitrogen and hydrogen, it’s very hard to form surface oxidization problems such as carburization, brittle interlayer, oxidization and so on. The combination of grain boundary will be more solid; Vacuum sintering method also has many advantages, such as low temperature sintering, short sintering time, low gas consumption, less pollution and so on, so vacuum sintering method has become a preferred method of electrodes sintering molding.