Process for synthesizing lithium difluoro(oxalate)borate from lithium bis(oxalate)borate

Abstract

The invention discloses a process for synthesizing lithium difluoro(oxalate)borate from lithium bis(oxalate)borate. The process comprises the following steps: mixing lithium bis(oxalate)borate with a compound containing fluorine, boron and lithium; carrying out a reaction in a solvent system at a temperature of 0 to 150 DEG C and a reaction pressure of 101 kpa and 150 kpa to produce a product; and carrying out a reaction at a certain temperature and then carrying out crystallization and vacuum drying so as to obtain battery-grade lithium difluoro(oxalate)borate. The process provided by the invention is novel in process and mild in conditions and can prepare high-purity battery-grade lithium difluoro(oxalate)borate.

Description

technical field [0001] The invention relates to a synthesis process of an electrolyte lithium salt used in the lithium ion battery industry, in particular to a synthesis process of lithium difluorooxalate borate. technical background [0002] Electrolyte salt is an important part of lithium-ion batteries, and its research and development is very important to the performance and development of lithium-ion secondary batteries. At present, the electrolyte of commonly used lithium-ion batteries is mainly lithium hexafluorophosphate (LiPF 6 ), lithium bisoxalate borate (LiBOB), lithium tetrafluoroborate (LiBF 4 )Wait. [0003] LiPF 6 The thermal stability of carbon dioxide is poor, easy to deliquescence, and must be used with ethylene carbonate (EC) to form a stable solid electrolyte interface (SEI) film on the surface of the carbon negative electrode; while the melting point of EC is 37 ° C, which will affect the low temperature performance. influences. LiBF 4 The charge t...

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Problems solved by technology

[0006] The typical preparation method of lithium difluorooxalate borate mainly contains LiBF in European Patent EP1195834A2 by Tsujioka.S et al. 4 、CH(CF 3 ) 2 OLi, H 2 C 2 o 4 , the reaction medium is a polar aprotic solvent such as carbonate or acetonitrile for synthesis, unreacted LiBF 4 Up to more than 15%; Tsujioka.S and others in the European patent EP1308449A2 with H 2 C 2 o 4 、LiBF 4 and AlCl 3 or SiCl 4 Synthesis of lithium difluorooxalate borate in dimethyl carbonate; HerzigT, ShchreinerC, GerhardD, et al. J Fluorine Chem, 2007, 128: 612-618 using H 2 C 2 o 4 and LiBF 4 AlCl in carbonate or acetonitrile 3 or SiCl 4 Synthesis under the action of additives, the above methods all have the characteristics of high requirements for reaction equipment, a large amount of hydrochloric acid gas and silicon tetrafluoride gas are emitted during the reaction, and it is easy to produce by-products that are not easy to separate or difficult to filter insolubles in the reaction mixture.

To overcome the above shortcomings, ZhangSS.Electrochem.Commun, 2006, 8: 1423-1428; Uno AKIRA, Uchiyama Hatsuo, Kawaswa Yoshio.JP59-50018, 1984 used BF 3 (CH 2 CH 3 ) 2 with Li 2 C 2 o 4 Synthesis of lithium difluorooxalate borate products in DMC, the process is simple, the cost is low, but at the same time there is a by-product LiBF 4 Formed and difficult to separate, resulting in low reaction yield

In recent years, Chinese published patents such as "CN101643481A", "CN102260282A", "CN1031113396A", "CN105399761A" and other published patents are similar to the above-mentioned patents. The purity of the LiODFB samples obtained is relatively low, and the generated by-product LiBF4 is difficult to separate. Purified before it can be used as an electrolyte for lithium-ion batteries

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