Method for preparation and purifying lithium difluoroborate

Abstract

The invention relates to a novel method for preparation and purifying an electrolyte lithium salt LiDFOB for a lithium ion battery, which belongs to the technical fields of novel energy materials and preparation. The method comprises the following specific steps of: (1) dissolving anhydrous dry NaBF4 and LiCl into an organic solvent; (2) adding a catalyst, heating, stirring and reflowing at the temperature of 30-80 DEG C, and fully reacting for 4-12 hours; (3) filtering, separating a solid from a liquid to obtain an organic solution of LiBF4, adding H2C2O4 and a catalyst in an inertial atmosphere, performing a magnetic stirring reaction at the temperature of 30-120 DEG C for 4-12 hours till no gas is generated, and ending reaction; and (4), filtering, evaporating a filtrate with a rotary evaporimeter till white solid particles are just formed, adding a non-polar solvent into the white solid particles, recrystallizing at a low temperature, filtering, and drying in vacuum at the temperature of 60 DEG C to obtain a high-purity LiDFOB product. The LiDFOB synthesizing method is simple, used raw materials are safe and nontoxic, an intermediate, i.e., LiBF4 is not required to be separated from a solvent, and the process flow is simplified. The LiDFOB prepared by using the process has superior performance, has a good application prospect in the field of power batteries, and is convenient to industrialize.

Description

technical field [0001] The invention relates to a new method for preparing and purifying lithium difluorooxalate lithium borate, an electrolyte lithium salt for lithium ion batteries, and belongs to the field of new energy materials and preparation technologies. Background technique [0002] In the past 10 years, lithium-ion batteries have been widely used in electronic communication fields such as mobile phones, notebook computers, and cameras, and have occupied a dominant position. With the rapid growth of new energy vehicles, the application of lithium-ion batteries in the field of power vehicles has become a research hotspot all over the world. The development of power vehicles has put forward higher requirements for lithium-ion batteries. [0003] Electrolyte is one of the four key materials of lithium-ion batteries (positive electrode, negative electrode, diaphragm, and electrolyte). increase. The electrolyte is responsible for the charge transfer between the positi...

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Problems solved by technology

And solid LiPF 6 The thermal stability of LiF is poor, and it starts to decompose when heated to 60°C, forming LiF and PF 5

Lithium tetrafluoroborate (LiBF 4 ) has advantages in moisture, temperature sensitivity and safety performance, etc., but the salt has low ion conductivity and cannot form a stable SEI film on the carbon negative electrode. It cannot be used alone in the electrolyte system of lithium-ion batteries. It must be combined with other lithium Lithium bisoxalate borate (LiBOB) is a new type of lithium salt, which has good film-forming properties and thermal stability, but still has the disadvantages of low solubility, low ionic conductivity, and poor low-temperature performance, and its Applied research is in its infancy

However, in these patents, toxic boron trifluoride is used as a raw material, and the synthesis conditions are harsh, and highly corrosive and toxic gas HF is easily generated when it meets water.

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