Non-acid system liquid phase synthesized C/Bi/BiF3 composite bismuth fluoride lithium ion battery positive electrode material and preparation method thereof

Abstract

The invention relates to a non-acid system liquid phase synthesized C / Bi / BiF3 composite bismuth fluoride lithium ion battery positive electrode material and a preparation method thereof. According to the method, the addition of dilute nitric acid for suppressing hydrolysis is omitted by designing a mixing mode of raw materials of bismuth nitrate pentahydrate and ammonium fluoride and an addition mode and addition rate of water, and a risk that high-toxicity hydrogen fluoride is generated by an effect of the dilute nitric acid and the ammonia fluoride is prevented; moreover, a certain amount of high-conductivity carbon and metal bismuth are reduced on surfaces of bismuth fluoride particles in an in-situ way, metal bismuth provides a homogeneous crystal core for an electrode material during discharging, and dynamics blocking formed by a new phase is reduced; and during the reaction process, side-reaction products such as various compound salts of the bismuth fluoride in liquid phase reaction are prevented, and the 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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