Continuous conduction in-situ C/Ag, metal solid solution/Mg<2+> doped BiF3 positive electrode and preparation method

Abstract

The invention discloses a continuous conduction in-situ C / Ag, metal solid solution / Mg<2+> doped BiF3 composite bismuth fluoride lithium ion battery positive electrode material and a preparation method. According to the method, in the drying process under low-temperature and high-vacuum conditions and the carbonization and in-situ reduction process under gas protection, a continuous carbon film of a hole and gap structure is formed, bismuth fluoride is fixedly formed on the carbon film and a certain amount of metal solid solution and silver are reduced in situ on the surfaces of bismuth fluoride particles, so that the electronic conductivity of the composite material is greatly improved; a homogeneous crystallization core is provided for the electrode material during discharging, and the kinetic blockage of new phase formation is reduced; the discharge ration rate is improved; Mg<2+> doping is further beneficial for reducing the crystal granularity of the discharge product; and moreover, various side reaction products such as double salts of bismuth fluoride are further prevented from being generated in a liquid-phase reaction, 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

In addition, ion doping is also an effective way to adjust the microstructure of the lattice and change the electron and ion transport characteristics of the lattice. However, the mechanism of ion doping or even multi-ion synergistic doping on the matrix is ​​very complicated, and the effect is often Unpredictable

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