Continuous conducting liquid-phase synthetic C/Ag and BiF3 composite bismuth fluoride cathode material for lithium-ion battery and preparation method thereof

Abstract

The invention discloses a continuous conducting liquid-phase synthetic C / Ag and BiF3 composite bismuth fluoride cathode material for a lithium-ion battery and a preparation method thereof. According to the method, through the design on the mixing way of reactive raw materials bismuth nitrate pentahydrate and ammonium fluoride and the addition way and the addition rate of water, the addition of dilute nitric acid inhibiting hydrolysis is avoided; the existence of the risk that the dilute nitric acid acts with the ammonium fluoride to generate high-toxicity hydrogen fluoride is avoided; meanwhile, a high-conductivity continuous carbon film which is of a structure with holes and gaps is formed through a drying process in low-temperature and high-vacuum conditions and a subsequent heat treatment process; certain amounts of bismuth and metal silver are reduced out in situ on the surface of a bismuth fluoride particle; a homogeneous crystallization nucleus is provided for an electrode material while discharging; the formation kinetic blockage of a novel phase is decreased; the improvement of a discharging reaction rate is facilitated; the generation of reaction by-products of multiple double salts of the bismuth fluoride, and the like, in a liquid-phase reaction is avoided; the cathode material has excellent electrochemical performance.

Description

technical field [0001] The invention relates to the technical field of a method for manufacturing a high-performance bismuth fluoride composite lithium battery cathode material. Background technique [0002] Lithium-ion secondary batteries have the absolute advantages of high volume, weight-to-energy ratio, high voltage, low self-discharge rate, no memory effect, long cycle life, and high power density. Currently, the global mobile power market has an annual share of more than 30 billion US dollars and Gradually grow at a rate of more than 10%. Especially in recent years, with the gradual depletion 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 a large amount of energy is used simultaneously to meet the needs of continuous power supply. Energy storage batteries; urban air quality problems caused by autom...

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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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