WO2012069554A1

WO2012069554A1 - Process for preparing organic lithium salts

Info

Publication number: WO2012069554A1
Application number: PCT/EP2011/070859
Authority: WO
Inventors: Miriam Kunze; Alexandra Lex-Balducci; Sascha Nowak; Stefano Passerini; Raphael Wilhelm Schmitz; Martin Winter
Original assignee: Westfälische Wilhelms-Universität Münster
Priority date: 2010-11-24
Filing date: 2011-11-23
Publication date: 2012-05-31
Also published as: DE102010060770A1

Abstract

The invention relates to a process for preparing a lithium salt with an organic borate and/or phosphate anion by reacting a fluorinated lithium salt with an organic lithium borate or lithium phosphate salt selected from the group comprising oxalates, malonates, glycolates, salicylates, lactates, catecholates, succinates and/or mixtures thereof in an aprotic solvent or solvent mixture.

Description

Process for the preparation of organic lithium salts

The invention relates to a process for the preparation of lithium salts with organic borate and / or phosphate anion. Due to their high energy and power density, lithium-ion batteries are now the favorite among energy storage devices, especially for portable applications

Electronics. Lithium-ion batteries comprise two electrodes, which are spatially separated by a separator. The charge transport takes place via an electrolyte. During the charging process, positively charged lithium ions migrate through the electrolyte from the positive to the negative electrode, while the charging current supplies the electrons via the external circuit. When unloading, the reverse process takes place. The electrolyte is a lithium salt dissolved in a mixture of nonaqueous solvent. Conducting salts are, for example, lithium hexafluorophosphate (LiPF ₆ ), lithium perchlorate (L1CIO ₄ ) or lithium borate salts, for example lithium tetrafluoroborate (L1BF ₄ ), lithium bis (oxalato) borate (LiBOB) and, more recently, lithium difluoroxalatoborate (LiDFOB). In particular, the lithium difluorooxalatoborat is characterized by very good temperature resistance and good SEI (Solid Electrolyte Interphase) -bildungseigenschaften.

Various processes for the preparation of lithium difluorooxalatoborate (LiDFOB) are known in the prior art. For example, the synthesis of LiDFOB by reaction of BF ₃ · Et ₂ O, a complex of boron trifluoride with diethyl ether as solvate, and L12C2O4 known. In known synthesis methods, for example, S1CI4 is used as a reaction auxiliary.

A disadvantage of these synthesis methods is that handling starting materials such as trifluoroborate etherate or silicon tetrachloride is cumbersome or dangerous. Furthermore, HCl is released during the synthesis and chloride or HCl partly remain in the product. This leads to serious problems. On the one hand, the product reacts acidly and on the other hand contains chloride impurities, which are particularly troublesome for the application, since this causes corrosion problems, especially in electrochemical applications. For the production of acid-poor lithium borate salts, document WO 2009/004059 discloses a purification by removal of acids or water by mixing with lithium hydride.

Therefore, there is a need for alternative synthetic methods for lithium salts with organic borate and / or phosphate anion.

The present invention was therefore based on the object to provide a method which overcomes at least one of the aforementioned disadvantages of the prior art. In particular, the present invention was based on the object to provide a method that allows production without impurities.

This object is achieved by a process for preparing a lithium salt with organic borate and / or phosphate anion by reacting a fluorinated lithium salt with an organic lithium borate or lithium phosphate salt selected from the group comprising oxalates, malonates, glycolates, salicylates, lactates, catecholates, succinates and / or mixtures thereof in an aprotic solvent or solvent mixture.

Further advantageous embodiments of the invention will become apparent from the dependent claims. Surprisingly, it has been found that the process according to the invention allows the preparation of lithium salts with organic borate and / or phosphate anion without

Reaction aids such as S1CI4 need to be used. In an advantageous manner, this does not cause any impurities.

In particular, the reaction product of the process of the invention contains no chloride impurities. The inventive method thus does not require separation of impurities. The preparation according to the invention of a lithium salt with organic borate and / or phosphate anion is thus a process wherein no purification is necessary to remove acids or water, for example by reaction with lithium hydride. The process step of drying and / or deacidifying a crude electrolyte with lithium hydride required in known processes is thus advantageously unnecessary. It provides a significant advantage that the reaction product need not be reacted with lithium hydride. As a result, advantageously no further purification or separation steps are required to remove excess lithium hydride and its reaction products. The process according to the invention can therefore, in particular, provide a one-step preparation of lithium salts with organic borate and / or phosphate anion.

It is of particular advantage that the process according to the invention can be carried out as a simple one-step synthesis. As a result, the cost of the synthesis can be significantly reduced and the conditions can be significantly simplified. Another great advantage is that only the reactants and reaction products are present in the reaction mixture.

Preferably, pure or very pure fluorinated lithium salts and organic

Lithium borate or lithium phosphate salts used as starting materials. Furthermore, preference is given to the use of aprotic solvents of a purity which can be used in lithium-ion batteries. As a result, time-consuming and expensive cleaning of the produced lithium salts with organic borate and / or phosphate anion can be avoided.

Preferably, the starting materials, fluorinated lithium salts and organic lithium borate or lithium phosphate salts are used in equimolar amounts. This can do that

Reaction equilibrium, for example, the reaction LiBF ₄ + LiBOB-► LiBFOB using lithium tetrafluoroborate and lithium bis (oxalato) borate favorably influenced product.

In preferred embodiments of the process according to the invention, use is made of a fluorinated lithium salt selected from the group comprising lithium hexafluorophosphate (LiPF ₆ ), lithium tetrafluoroborate (LiBF ₄ ), lithium hexafluoroarsenate (LiAsF ₆ ),

Lithium hexafluorostannate (LiSnF ₆ ) and / or lithium hexafluorotanatalate (LiTaF ₆ ).

These have the advantage of being good fluorinating agents for the reaction. In particularly preferred embodiments, the fluorinated lithium salt is

Lithium tetrafluoroborate (LiBF ₄ ).

In preferred embodiments, use is made of an organic lithium borate or lithium phosphate salt selected from the group comprising lithium bis (oxalato) borate (LiBOB), lithium bis (malonato) borate (LiBMB), lithium malonato oxalate borate (LiMOB), lithium glycolato oxalato borate (LiGOB ), Lithium salicylatooxalatoborate (LiSOB), lithium lactatooxalatoborate (LiLOB), lithium catecholatoalatoborate (LiBZOB), lithium bis (succinato) borate (LiBSB) and / or lithium tris (oxalato) phosphate (LiTOP).

Organic lithium borate and lithium phosphate salts as starting materials of

Process according to the invention can be obtained or produced in a simple manner and on an industrial scale. For example, Lithiumoxalatoboratsalze by Implementation of an oxide boron compound such as boric acid, boron oxide or

Boric acid ester can be prepared with oxalic acid or an oxalic acid salt. In particularly preferred embodiments, the organic lithium borate is lithium bis (oxalato) borate (LiBOB).

The yield of the process according to the invention can be favorably influenced by varying the aprotic solvent or the ratio of the solvents of a solvent mixture, the reaction temperature and / or the reaction time. Preferred aprotic solvents are selected from the group comprising cyclic carbonates, preferably ethylene carbonate (EC) and / or propylene carbonate (PC), linear carbonates, preferably diethyl carbonate (DEC), dimethyl carbonate (DMC) and / or ethyl methyl carbonate (EMC), nitriles, preferably acetonitrile (AN) , Dinitriles preferably glutaronitrile (GLN), adiponitrile (ADN) and / or pimelonitrile (PIN), and / or lactones preferably gamma-butyrolactone (GBL) and / or gamma-valerolactone (GVL).

By using aprotic solvents, it is possible to prevent the lithium salts from decomposing as in the presence of protic solvents. In particular, ethylene carbonate (EC) is preferably usable as the sole solvent or as a constituent of a solvent mixture.

In preferred embodiments, the aprotic solvent mixture used is a mixture of ethylene carbonate (EC) with at least one further aprotic solvent selected from the group comprising cyclic carbonates, preferably propylene carbonate (PC), linear carbonates, preferably diethyl carbonate (DEC), dimethyl carbonate (DMC) and / or ethyl methyl carbonate (EMC), nitriles preferably acetonitrile (AN), dinitriles preferably glutaronitrile (GLN), adiponitrile (ADN) and / or pimelonitrile (PIN), and / or lactones preferably gamma-butyrolactone (GBL) and / or gamma-valerolactone (GVL) , In preferred embodiments, the reaction is carried out in an aprotic solvent mixture of ethylene carbonate (EC) with another aprotic

Solvent selected from the group comprising cyclic carbonates, preferably propylene carbonate (PC), linear carbonates, preferably diethyl carbonate (DEC),

Dimethyl carbonate (DMC) and / or ethyl methyl carbonate (EMC), nitriles preferably acetonitrile (AN), dinitriles preferably glutaronitrile (GLN), adiponitrile (ADN) and / or pimelonitrile (PIN), and / or lactones preferably gamma-butyrolactone (GBL) and or gamma-valerolactone (GVL) having a molar ratio of ethylene carbonate to the at least one further aprotic solvent in the range of> 1: 9 to <9: 1, preferably in the range of> 3: 7 to <7: 3, preferably Range from> 3: 7 to <1: 1, by.

A molar ratio of ethylene carbonate to the at least one further aprotic solvent in the range of> 1: 9 to <9: 1 is preferably suitable. In an advantageous manner, in particular with a molar ratio of ethylene carbonate to the

at least one further aprotic solvent in the range of> 3: 7 to <7: 3, preferably in the range of> 3: 7 to <1: 1, the reaction to a good yield

Product be influenced. In preferred embodiments of the method according to the invention leads to the

Reaction at temperatures in the range of> 45 ° C to <120 ° C, preferably in the range of> 60 ° C to <100 ° C, preferably at temperatures in the range of> 65 ° C to <95 ° C, by.

Good yields result in an advantageous manner in a range of> 45 ° C to <120 ° C. Particularly good yields result in a range of> 60 ° C to <100 ° C, especially at temperatures in the range of> 65 ° C to <95 ° C. Preferably, the reaction is carried out in a period in the range of> 48 h to <180 h, preferably in the range of> 65 h to <170 h, preferably in the range of> 110 h to <165 h, by. In an advantageous manner, particularly good yields were obtained over a period in the range from> 65 h to <170 h, preferably in the range from> 110 h to <165 h.

The lithium salt with organic borate and / or phosphate anion is preferably selected from the group consisting of lithium difluorooxalatoborate (LiDFOB), lithium difluoromalonato borate, lithium difluoroglycolate borate, lithium difluorosalicylatoborate, lithium difluorolactatoborate, lithium difluoro-catechinatoborate and / or lithium tetrafluoro (oxalato) phosphate (LTFOP).

In particular, lithium difluorooxalatoborate (LiDFOB) is useful in lithium-ion batteries. The process of the invention comprises reacting a fluorinated lithium salt with an organic lithium borate or lithium phosphate salt. The fluorinated lithium salt, for example, lithium tetrafluoroborate, may be the organic lithium borate or

Fluoride lithium phosphate salt. The process according to the invention is therefore in particular a process for the preparation of a lithium salt with fluorinated organic borate and / or phosphate anion. Of the lithium salts with fluorinated organic borate and / or

Phosphate anion selected from the group comprising lithium difluorooxalatoborat, lithium difluoromalonatoborat, lithium difluoroglycolatoborat, lithium difluorosalicylatoborat, lithium difluorolactatoborat, lithium difluoro-catecholate and / or lithium tetrafluoro (oxalato) phosphate is lithium difluorooxalatoborat particularly preferred.

In particularly preferred embodiments, the process for the preparation of lithium difluorooxalatoborat (LiDFOB) by reacting lithium tetrafluoroborate (L1BF ₄ ) with lithium bis (oxalato) borate (LiBOB). The reaction mixture can be separated by chromatography or by fractional crystallization. Preferably, the organic lithium fluoro salt is purified

chromatographically from the reaction mixture. In particular, it is advantageous that unreacted purified starting materials can be recycled to a new reaction.

Another object of the invention relates to lithium salts with organic borate and / or phosphate anion produced by the novel process. In particular, the invention relates to lithium salts with fluorinated organic borate and / or phosphate anion prepared by the process according to the invention.

Another object of the invention relates to the use of a lithium salt with organic borate and / or phosphate anion produced by the novel process as a lithium-ion electrolyte in primary and secondary electrochemical energy storage, in particular in lithium-ion batteries. In particular, the

The invention relates to the use of a lithium salts with fluorinated organic borate and / or phosphate anion produced by the novel process in primary and secondary electrochemical energy storage, in particular in lithium-ion batteries. Examples which serve to illustrate the present invention are given below.

example 1

Synthesis of lithium difluorooxalatoborate by reaction of LiBF ₄ with

Lithium bisoxalatoborate (LiBOB)

With 0.94 g (0.01 mol) LiBF ₄ (Sigma Aldrich) and 1.93 g (0.01 mol) LiBOB (Chemetal), 10 mL of a 1 M standard solution with an ethylene carbonate (EC, Ferro, 30 wt. %) / Diethyl carbonate (DEC, Ferro, 70 wt.%) Mixture created. 200 μL of the 1 M LiBF ₄ solution and the 1 M LiBOB solution were added to a NMR tube in a glove box (MBraun) with a water and oxygen content of <Ippm. The NMR tube was then evacuated, cooled with liquid nitrogen and sealed with a propane gas burner. Subsequently, the reaction solution was kept for 162 h in an oven (ED 53, BINDER GmbH) at a temperature of 95 ° C. The NMR tube was cooled and the reaction yield determined by ^U B NMR (Bruker Avance 3, 400 MHz, liquid broadband probe, at 22 ° C-23 ° C). In the ^U B spectrum only LiDFOB (8.6%), LiBOB (40.7%) and LiBF ₄ (50.7%) were found.

Example 2

With 0.94 g (0.01 mol) LiBF (Sigma Aldrich) and 1.93 g (0.01 mol) LiBOB (Chemetal), 10 mL of a 1 M standard solution with an ethylene carbonate (EC, Ferro, 30% by weight). ) / Diethyl carbonate (DEC, Ferro, 70% by weight) mixture. 200 μL of the 1 M LiBF solution and the 1 M LiBOB solution were placed in a glove box (MBraun) with a water and oxygen content of <Ippm in an NMR tube. The NMR tube was then evacuated, cooled with liquid nitrogen and sealed with a propane gas burner. Subsequently, the reaction solution was kept at a temperature of 95 ° C. for 113 h in an oven (ED 53, BINDER GmbH). The NMR tube was cooled and the reaction yield determined by ^U B NMR (Bruker Avance 3, 400 MHz, liquid broadband probe, at 22 ° C-23 ° C). In the ^U B spectrum only LiDFOB (7, 1%), LiBOB (41.2%) and LiBF (52.7%) were found.

Example 3

With 0.94 g (0.01 mol) LiBF (Sigma Aldrich) and 1.93 g (0.01 mol) LiBOB (Chemetal), 10 mL of a 1 M standard solution with an ethylene carbonate (EC, Ferro, 50% by weight). ) / Diethyl carbonate (DEC, Ferro, 50% by weight) mixture. 200 μL of the 1 M LiBF solution and the 1 M LiBOB solution were mixed in a glove box (MBraun) with a Water and oxygen content of <Ippm in an NMR tube. The NMR tube was then evacuated, cooled with liquid nitrogen and sealed with a propane gas burner. Subsequently, the reaction solution was kept for 162 h in an oven (ED 53, BINDER GmbH) at a temperature of 95 ° C. The NMR tube was cooled and the reaction yield determined by ^U B NMR (Bruker Avance 3, 400 MHz, liquid broadband probe, at 22 ° C-23 ° C). In the ^U B spectrum only LiDFOB (7.5%), LiBOB (40.6%) and LiBF ₄ (51.9%) were found.

Example 4

Synthesis of lithium difluorooxalatoborat by reaction of LiBF ₄ with

Lithium bisoxalatoborate (LiBOB)

With 0.94 g (0.01 mol) LiBF (Sigma Aldrich) and 1.93 g (0.01 mol) LiBOB (Chemetal), 10 mL of a 1 M standard solution with an ethylene carbonate (EC, Ferro, 50% by weight). ) / Diethyl carbonate (DEC, Ferro, 50% by weight) mixture. 200 μL each · 1 M LiBF -

Solution and the 1 M LiBOB solution were placed in a glove box (MBraun) with a water and oxygen content of <Ippm in an NMR tube. The NMR tube was then evacuated, cooled with liquid nitrogen and sealed with a propane gas burner. Subsequently, the reaction solution was kept at a temperature of 95 ° C. for 113 h in an oven (ED 53, BINDER GmbH). The NMR tube was cooled and the reaction yield determined by ^U B NMR (Bruker Avance 3, 400 MHz, liquid broadband probe, at 22 ° C-23 ° C). In the ^U B spectrum only LiDFOB (5.8%), LiBOB (41.4%) and LiBF (52.8%) were found. Example 5

Synthesis of lithium difluorooxalatoborate by reaction of LiBF with

Lithium bisoxalatoborate (LiBOB) With 0.94 g (0.01 mol) LiBF ₄ (Sigma Aldrich) and 1.93 g (0.01 mol) LiBOB (Chemetal), 10 mL of a 1 M standard solution with an ethylene carbonate (EC, Ferro, 50 wt. %) / Adiponitrile (ADN, Sigma Aldrich, 50% by weight) mixture. 200 μL of the 1 M LiBF ₄ solution and the 1 M LiBOB solution were added to an NMR tube in a glove box (MBraun) with a water and oxygen content of <lppm. The NMR tube was then evacuated, cooled with liquid nitrogen and sealed with a propane gas burner. Subsequently, the reaction solution was kept for 162 h in an oven (ED 53, BINDER GmbH) at a temperature of 95 ° C. The NMR tube was cooled and the reaction yield determined by ^U B NMR (Bruker Avance 3, 400 MHz, liquid broadband probe, at 22 ° C-23 ° C). In the ^U B spectrum only LiDFOB (2.8%), LiBOB (44.9%) and LiBF (52.3%) were found.

Further reactions of LiBF with lithium bisoxalatoborate (LiBOB) are summarized in the following Table 1:

Table 1

Example solvent, temperature time LiDFOB

Ratio [° C] [h] [% yield]

6 EC / DEC 3/7 95 65 4.5

7 EC / DEC 1/1 95 65 3.0

8 EC / ADN 1/1 95 113 1.7

9 EC / DEC 3/7 60 162 1.0

Claims

PATENT CLAIMS

1. A process for the preparation of a lithium salt with organic borate and / or phosphate anion by reacting a fluorinated lithium salt with an organic lithium borate or lithium phosphate salt selected from the group comprising oxalates, malonates, glycolates, salicylates, lactates, catecholates, succinates and / or mixtures thereof in an aprotic solvent or solvent mixture.

2. The method according to claim 1, characterized in that the fluorinated lithium salt is selected from the group comprising lithium hexafluorophosphate, lithium tetrafluoroborate,

Lithium hexafluoroarsenate, lithium hexafluorostannate and / or lithium hexafluorotanatalate.

3. The method according to claim 1 or 2, characterized in that the organic lithium borate or lithium phosphate salt is selected from the group comprising lithium bis (oxalato) borate, lithium bis (malonato) borate, lithium malonato oxalatoborat, lithium glykolatooxalatoborat, lithium salicylatooxalatoborate, lithium lactatooxalatoborate, lithium catecholato oxatoborate, lithium bis (succinato) borate and / or lithium tris (oxalato) phosphate.

4. The method according to any one of the preceding claims, characterized in that the aprotic solvent is selected from the group comprising cyclic carbonates, preferably ethylene carbonate and / or propylene carbonate, linear carbonates, preferably diethyl carbonate, dimethyl carbonate and / or ethylmethylcarbonate, nitriles, preferably acetonitrile, dinitriles, preferably glutaronitrile, Adiponitrile and / or pimelonitrile, and / or lactones, preferably gamma-butyrolactone and / or gamma-valerolactone.

5. The method according to any one of the preceding claims, characterized in that the aprotic solvent mixture is a mixture of ethylene carbonate with at least one further aprotic solvent selected from the group comprising cyclic

Carbonates are preferably propylene carbonate, linear carbonates preferably diethyl carbonate, dimethyl carbonate and / or ethylmethyl carbonate, nitriles preferably acetonitrile, dinitriles preferably glutaronitrile, adiponitrile and / or pimelonitrile, and / or lactones preferably gamma-butyrolactone and / or gamma- valerolactone.

6. The method according to any one of the preceding claims, characterized in that reacting in an aprotic solvent mixture of ethylene carbonate with a further aprotic solvent selected from the group comprising cyclic

Carbonates preferably propylene carbonate, linear carbonates preferably diethyl carbonate, dimethyl carbonate and / or ethylmethylcarbonate, nitriles preferably acetonitrile, dinitriles preferably glutaronitrile, adiponitrile and / or pimelonitrile, and / or lactones preferably gamma-butyrolactone and / or gamma- valerolactone with a molar ratio of ethylene carbonate to the at least one further aprotic solvent in the range of> 1: 9 to <9: 1, preferably in the range of> 3: 7 to <7: 3, preferably in the range of> 3: 7 to <1: 1, performed.

7. The method according to any one of the preceding claims, characterized in that reacting at temperatures in the range of> 45 ° C to <120 ° C, preferably in the range of> 60 ° C to <100 ° C, preferably at temperatures in the range from> 65 ° C to <95 ° C.

8. The method according to any one of the preceding claims, characterized in that the reaction in a period in the range of> 48 h to <180 h, preferably in the range of> 65 h to <170 h, preferably in the range of> 110 h to <165 h, performs.

9. The method according to any one of the preceding claims, characterized in that the lithium salt with organic borate and / or phosphate anion is selected from the group comprising lithium difluorooxalatoborat, Lithiumdifluoromalonatoborat, lithium difluoroglycolatoborate, lithium difluorosalicylatoborat, lithium difluorolactatoborat, lithium difluoro-catecholate and / or lithium tetrafluoro (oxalato) phosphate.

10. Lithium salt with organic borate and / or phosphate anion prepared by a process according to one of the preceding claims.

11. Use of a lithium salt with organic borate and / or phosphate anion prepared by a process according to one of the preceding claims as a lithium-ion electrolyte in primary and secondary electrochemical energy storage.