Research Progress in the Preparation of New Lithium Salt Lithium Difluoroxalate Borate
Jun 24, 2022
Introduction
Electrolyte salt is an important part of lithium ion battery, and its research and development is very important to the performance and development of lithium ion secondary battery.
At present, lithium salts such as lithium hexafluorophosphate (LiPF6), Lithium tetrafluoroborate (LiBF4), lithium bis-oxalate borate (Li-BOB), and lithium difluorooxalate borate (LiDFOB) are mainly developed.
As a new type of lithium salt, lithium difluorooxalate borate (LiDFOB). It has half the structure of lithium tetrafluoroborate and lithium bis-oxalate borate, so it combines the advantages of two lithium salts, not only the high temperature performance of LiBOB, but also the low temperature performance of LiBF4, and the use of a wide temperature range.
Preparation of CAS 409071-16-5 | Lithium Difluoro(oxalato)borate
1) Solid Phase Method
Compounds containing fluorine, boron, lithium and oxalate are mixed in a certain proportion, and after ball milling and high-temperature heat treatment, the product is purified by organic solvent for several times to obtain lithium difluorooxalate borate product.
Lithium oxalate and boron trifluoride ether are added into a dry spherical ink tank in a ratio of 1: 1 to 1: 3, and ball-milled at 30-90 ° C for 2-24 h; then the ball-milled reaction product is dissolved in In an organic solvent at 30-90 °C, the solid phase by-products and unreacted lithium oxalate are removed by filtration to obtain a solution containing LiODFB. Then crystallize at a low temperature of -20-10 °C to obtain LiODFB crystals, and vacuum dry at 40-100 °C for 10-48 h to obtain pure LiODFB solids.
2) Water phase method
Under the hydrofluoric acid solution system, the lithium-containing compound, the boron-containing compound and the oxalate-containing compound are added for one-step reaction to obtain a crude product aqueous solution, and then an organic solvent is added, concentrated and purified to obtain a lithium difluorooxalate borate product.
The concentration of 20% hydrofluoric acid, lithium oxalate, and diboron trioxide were fully stirred at 20 to 80 °C for 2 to 24 h in a closed environment, and then filtered to remove the by-product lithium fluoride, and concentrated by evaporation under reduced pressure.
A concentrated solution of lithium difluorooxalate borate is obtained; an organic solution containing thionyl chloride is slowly added, and the product of lithium difluorooxalate borate is obtained by filtration after purification.
3) Organic solvent method (lithium tetrafluoroborate method)
Using lithium tetrafluoroborate, oxalic acid, ethyl acetate and auxiliary anhydrous aluminum chloride as raw materials, the reaction temperature is 10 ℃, the reaction time is 4 h, the ratio of reactants is 1:1, the crystallization temperature is -20 ℃, The crystallization time is 4 h, the purity of the prepared LiODFB can reach 99.97%, and the yield can reach 95.9%.
