Integral conductive in-situ C / Bi / BiF3 composite bismuth fluoride lithium ion battery positive electrode material and preparation method thereof

Abstract

The invention discloses an integral conductive in-situ C / Bi / BiF3 composite bismuth fluoride lithium ion battery positive electrode material and a preparation method thereof. According to the preparation method of the integral conductive in-situ C / Bi / BiF3 composite bismuth fluoride lithium ion battery positive electrode material, the bismuth nitrate is fixed on a highly conductive continuous carbon film with a void and interspace structure through the drying process at a low temperature and high vacuum condition and the heat treatment process; meanwhile, a certain amount of metallic bismuth is reduced on the surface of the bismuth fluoride particles during the heat treatment process, therefore, a homogeneous crystalline core is provided for the discharge of the electrode materials, and the kinetics barrier to the formation of new phases is reduced; and the formation of the side reaction products such as a variety of the complex salt of bismuth fluoride in a liquid phase reaction is avoided by the immobilization of the reaction raw materials, and the electrochemical performance is excellent.

Description

technical field [0001] The invention relates to the technical field of a manufacturing method for a high-performance bismuth fluoride composite lithium battery positive electrode material. Background technique [0002] Lithium-ion secondary batteries have the absolute advantages of high volume, high weight-to-energy ratio, high voltage, low self-discharge rate, no memory effect, long cycle life, and high power density. Gradually grow at a rate of over 10%. Especially in recent years, with the gradual exhaustion of fossil energy, new energy sources such as solar energy, wind energy, and biomass energy have gradually become alternatives to traditional energy sources. Among them, wind energy and solar energy are intermittent, and in order to meet the needs of continuous power supply, a large number of Energy storage batteries; the urban air quality problem caused by automobile exhaust is becoming more and more serious, and the vigorous advocacy and development of electric vehi...

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Problems solved by technology

The conventional synthesis method of bismuth fluoride is to react with hydrogen fluoride gas and metal oxide / hydroxide or fluorine gas and metal element at high temperature. The process conditions are harsh, the equipment requirements are very high, and the energy consumption is high, so the price is very expensive.

However, the preparation of bismuth fluoride by liquid phase reaction is often unable to be used as a positive electrode material because the content of by-products is too high. At the same time, the dilute nitric acid added to inhibit the hydrolysis of bismuth nitrate in water has the risk of producing highly toxic hydrogen fluoride by reacting with ammonium fluoride.

Bismuth fluoride, as a cathode material for lithium-ion secondary batteries, also has a negative characteristic that its electronic conductivity is extremely low, so it will cause a high polarization voltage during charge and discharge.

Although some researchers have used carbon black mixed with ball milling to increase the electrical conductivity of the material, it is still difficult for granular carbon black to form a complete conductive link, which greatly improves its electronic conductivity.

Finally, the material produces a new phase of metal bismuth and lithium fluoride during discharge, and the small particles of the new phase are kinetically disadvantaged in the initial stage of formation, so the maintenance of the subsequent charge and discharge capacity, discharge potential, and charge and discharge capacity ability to adversely affect

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