Efficient preparation method of high-purity lithium oxalyldifluoroborate (LiODFB)

Abstract

The invention discloses an efficient preparation method of high-purity lithium oxalyldifluoroborate (LiODFB). The method comprises the steps of firstly, synthesizing a high-crystallinity and high-activity needle-shaped mixed crystal A by taking Li2CO3 and H2C2O4.2H2O as raw materials, wherein the needle-shaped mixed crystal A is formed by co-crystallizing lithium oxalate and lithium hydrogenoxalate which are taken as main phases; adding the mixed crystal A into a closed container filled with an organic solvent, then adding a BF3.X complex, at least one of oxamide, oxamic acid, anhydrous oxalic acid and ammonium oxalate as well as a certain amount of initiator, continuously stirring for 30min to obtain an emulsion solution B, and filtering to obtain a clear and transparent solution C; removing the solvent of the solution C under the conditions of certain temperature and pressure to obtain a LiODFB product with the purity of 99% or above. A high-purity LiODFB product with the purity of 99.9% or above is obtained by carrying out recrystallization on the organic solvent for removing impurities at a time. After the preparation method is adopted, the LiODFB product with the purity of 99% or above can be directly obtained by means of a synthetic reaction. The defects of low yield, high cost and long period which are caused by repeated recrystallization are avoided. Furthermore, the preparation method is simple, easy to operate, short in period and easy in realization of industrial production, thus having very good application prospect.

Description

technical field [0001] The invention relates to a new method for preparing an electrolyte lithium salt lithium difluorooxalate borate (LiODFB), which belongs to the field of new energy materials and preparation technology. Background technique [0002] Lithium difluorooxalate borate (LiODFB) was first reported as a new type of lithium salt. Due to its superior comprehensive performance, it has attracted extensive attention from researchers in the past ten years. It has been reported by a large number of studies and has been considered to be the most likely to replace LiPF. 6 new lithium salts. Existing research mainly focuses on the stability and electrochemical performance of LiODFB, but there are few reports on the preparation and purification of LiODFB, especially the research on industrial scale. Although the performance of LiODFB is excellent, due to various reasons, including: the high cost of raw materials, the complexity of the synthesis process is difficult to cont...

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Problems solved by technology

[0003] Regarding the report on the synthesis of LiODFB, in 2002, the patent US6485868B1 reported the synthesis method of LiODFB. 4 、CH(CF 3 ) 2 OLi and H 2 C 2 o 4 As a raw material, polar aprotic solutions such as carbonate or acetonitrile (AN) are used as reaction media, but the purity of the resulting product is low, and LiBF 4 Content greater than 15%

In 2006, Zhang, C, C et al reported in the literature Electrochemistry Communications 8 (2006) 1423–1428 that boron trifluoride ether and lithium oxalate (molar ratio 1:1) were used as raw materials in dimethyl carbonate (DMC) reaction, LiODFB crude product was prepared, using DMC or other aprotic solvents to carry out multiple recrystallization of LiODFB crude product can obtain relatively pure product, but the yield of this method is low and easy to produce insoluble impurities, and the production cost is high

However, since the reaction needs to be carried out at low temperature, the raw material LiBF used 4 The price is high, and several recrystallizations are still required to obtain a relatively pure LiODFB product, so the application value is not great

In 2013, Li et al reported the synthesis method of LiODFB in the literature Electrochimica Acta 91 (2013) 282– 292, using boron trifluoride ether, lithium oxalate and diethyl carbonate (DEC) (molar ratio 2:1:4) Synthetic experiments were carried out as raw materials to obtain LiODFB and LiBF in equimolar ratio 4 , multiple recrystallizations (more than 7 times) through DMC to obtain LiODFB products with high purity, but the yield of this method is low, the direct yield is only 10%, the cost is high, and it is difficult to apply on a large scale

[0004] The existing public reports mainly use lithium oxalate and lithium tetrafluoroborate as raw materials for reaction synthesis in terms of raw material lithium salt selection, all of which have relatively large defects

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