KR102164920B1 - Process for Preparing Lithium Difluorobis(oxalato)phosphate - Google Patents

Abstract

The present invention relates to a method for producing lithium difluorobis (oxalato) phosphate. According to the manufacturing method of the present invention, by adding methyltrichlorosilane (MeSiCl ₃ ) to lithium hexafluorophosphate and oxalic acid and reacting, the chemical selectivity to LDFOP is very high, and high purity LDFOP can be efficiently and industrially manufactured. In addition, it is easy to remove by-products generated during the reaction.

Description

Method for producing lithium difluorobis(oxalato)phosphate {Process for Preparing Lithium Difluorobis(oxalato)phosphate}

The present invention relates to a method for producing lithium difluorobis (oxalato) phosphate, and more particularly, to a high purity lithium difluorobis (oxalato) phosphate used as a non-aqueous electrolyte additive for lithium secondary batteries. It relates to a method of manufacturing industrially.

Lithium difluorobis (oxalato) phosphate (LDFOP) and lithium tetrafluoro (oxalato) phosphate (LTFOP) represented by the following formulas 1 and 2, respectively, improve the performance of lithium secondary batteries and lithium ion capacitors. It is used as a non-aqueous electrolyte additive for [Reference: US Patent No. 6,783,896, International Patent Publication No. WO 2009/066559].

[Formula 1]

[Formula 2]

A method of manufacturing the LDFOP and LTFOP is disclosed in Korean Patent Publication No. 2011-0086102. Specifically, lithium hexafluorophosphate (LiPF ₆ ) and silicon tetrachloride (SiCl ₄ ) are added dropwise to oxalic acid and then reacted at elevated temperature to obtain an LDFOP/LTFOP mixture solution, and an LDFOP/LTFOP mixture solution with less chlorine compounds or free acids It is stated to provide However, the above manufacturing method has a problem that only LDFOP cannot be chemically selectively manufactured. In addition, the above manufacturing method can be removed by decompressing HCl and SiF ₄ (bp -86°C), which are by-products remaining in the reaction solution, but their boiling point (bp) is mostly low and trapping. There is also a problem in that it is not easy to completely remove it so that it is not discharged into the atmosphere through.

It is known that the role of additives such as LDFOP in the composition of a non-aqueous electrolyte is very important to improve the performance of lithium secondary batteries. In general, it is reported that the purity of the additive greatly affects the performance of the battery. Therefore, when manufacturing high-purity additives, the chemical selectivity for LDFOP is very important.If the selectivity is poor, the mixture of LDFOP and LTFOP is used as the current chemical process technology. It is very difficult to separate and purify.

As another manufacturing method, U.S. Patent Publication No. 2010/0267984 discloses a method of using lithium oxalate, of which LiPF ₆ is heated to a high temperature to generate PF ₅ gas and reacted with lithium oxalate is difficult to industrialize. It is difficult to control the ratio of, and the method of mixing lithium oxalate and LiPF ₆ in a solid state, milling and then heating it to a high temperature, also has a problem that it is difficult to industrialize.

U.S. Patent No. 6,783,896 International Patent Publication No. WO 2009/066559 Korean Patent Publication No. 2011-0086102 US Patent Publication No. 2010/0267984

The present inventors studied intensively to solve the above problems in the production of lithium difluorobis (oxalato) phosphate (LDFOP), and as a result, methyl trichlorosilane (MeSiCl ₃ ) in lithium hexafluorophosphate and oxalic acid By adding and reacting, the chemoselectivity for LDFOP is very high, so that high-purity LDFOP can be mass-produced more efficiently, and the boiling point (bp) of the produced by-products is relatively high, so it is easy to remove by collection. , Has completed the present invention.

Accordingly, an object of the present invention is to provide a method for efficiently and industrially producing high purity lithium difluorobis(oxalato)phosphate.

In one embodiment of the present invention, lithium difluorobis (oxalato) phosphate comprising the step of reacting by adding methyl trichlorosilane (MeSiCl ₃ ) to lithium hexafluorophosphate (LiPF ₆ ) and oxalic acid ( LDFOP) to a manufacturing method.

According to the manufacturing method of the present invention, by controlling the molar ratio of oxalic acid and/or methyltrichlorosilane (MeSiCl ₃ ) to lithium hexafluorophosphate, and/or the reaction temperature, high-purity LDFOP can be chemically selectively prepared in high yield. I can.

In one embodiment of the present invention, the molar ratio of lithium hexafluorophosphate and oxalic acid may be 1:1.8 to 1:2.2, preferably 1:1.95 to 1:2.1. When the molar ratio of lithium hexafluorophosphate and oxalic acid satisfies the above range, the yield and chemical selectivity of LDFOP are excellent.

In one embodiment of the present invention, the molar ratio of lithium hexafluorophosphate and methyl trichlorosilane (MeSiCl ₃ ) may be 1:1.2 to 1:2.5, preferably 1:1.8 to 1:2.0. When the molar ratio of lithium hexafluorophosphate and methyltrichlorosilane satisfies the above range, the yield and chemical selectivity of LDFOP are excellent.

The molar ratio of lithium hexafluorophosphate and oxalic acid suitable for preparing LDFOP with 100% chemical selectivity is 1:1.95 to 1:2.1, and the molar ratio of lithium hexafluorophosphate and methyltrichlorosilane (MeSiCl ₃ ) is 1 :1.8 to 1:2.0.

In the production method of the present invention, the reaction temperature may preferably be in the range of 20 to 70°C. If it is out of the above range, the yield and/or chemical selectivity of LDFOP may deteriorate.

Preferably, LDFOP can be prepared with 100% chemical selectivity by reacting by reacting in the range of 20 to 45°C and then raising the temperature in the range of 50 to 70°C.

The oxalic acid used in the present invention can be used by drying a commercially available dihydrate, and the drying method is not particularly limited, but a method such as heating or vacuum drying can be used.

In one embodiment of the present invention, the reaction may be carried out in a non-aqueous solvent.

As the non-aqueous solvent, at least one solvent selected from the group consisting of cyclic carbonate, chain carbonate, chain nitrile, cyclic ester, chain ester, and chain halogenated solvent may be used. For example, cyclic carbonates such as propylene carbonate, ethylene carbonate, butylene carbonate, chain carbonates such as diethyl carbonate, dimethyl carbonate, and ethylmethyl carbonate, chain nitriles such as acetonitrile and propionitrile, butyrolactone, valero Cyclic esters such as lactone, chain esters such as ethyl acetate and ethyl propionate, and chain halogenated solvents such as dichloromethane and 1,2-dichloroethane may be used, but are not limited thereto.

It is preferable to use a dehydrated one of these non-aqueous solvents, and the moisture concentration in the non-aqueous solvent used in the present invention is preferably 100 ppm by weight or less. If the moisture concentration exceeds 100 ppm by weight, LiPF ₆ , LTFOP and LDFOP are hydrolyzed, which is not preferable.

The concentration of LiPF ₆ in the non-aqueous solvent used in the present invention is not particularly limited and may be any concentration, but the lower limit is preferably 1% by weight, more preferably 5% by weight, and the upper limit is preferably 40% by weight. %, more preferably 20 to 30% by weight. If the concentration is less than 1% by weight, the concentration of the obtained LDFOP solution is too low. Therefore, it is not economical because a product sensitive to moisture must be concentrated over a long period of time in order to be used as an electrolyte for a nonaqueous electrolyte battery. On the other hand, when the concentration exceeds 40% by weight, it is difficult to perform the reaction smoothly due to an increase in the viscosity of the solution, and the filtration rate of the reaction solution is lowered, which is not preferable.

The manufacturing method according to an embodiment of the present invention may include the step of obtaining a LDFOP solution of a desired concentration, preferably 10 to 30 wt% by performing the reaction in a non-aqueous solvent, and then removing or adding a part of the non-aqueous solvent. have.

In the production method of the present invention, since the product LDFOP or LDFOP/LTFOP mixture is hydrolyzed by moisture, it is preferable to perform the reaction in an atmosphere that does not contain moisture. For example, it is preferable to carry out the reaction in an inert gas atmosphere such as nitrogen and argon.

In one embodiment of the present invention, by-products generated during the reaction may be completely removed by trapping.

Specifically, the collection may be performed by first passing excess water cooled with an ice bath, and then passing through a -50°C low temperature trap.

The main by-products are methyltrifluorosilane (MeSiF ₃ ) (bp -30°C) compound and HCl, and can be removed together by the above trapping method.

According to the manufacturing method of the present invention, by adding methyltrichlorosilane (MeSiCl ₃ ) to lithium hexafluorophosphate and oxalic acid and reacting, the chemoselectivity for LDFOP can be improved by 80% or more, especially up to 100%. Therefore, it is possible to manufacture high-purity LDFOP more efficiently and industrially, and the boiling point (bp) of methyltrifluorosilane (MeSiF ₃ ), a major by-product generated during the reaction, is higher than -30°C, making it easy to collect. There is an advantage.

Methyl trichlorosilane (MeSiCl ₃ ) used in the manufacturing method of the present invention shows excellent chemical selectivity for LDFOP compared to silicon tetrachloride (SiCl ₄ ) used in the past, and also has a similar chemical structure that does not generate LDFOP at all. It can be seen that it has excellent reactivity compared to dimethyldichlorosilane (Me ₂ SiCl ₂ ).

The method of preparing the electrolyte for a non-aqueous electrolyte battery using LDFOP or LDFOP/LTFOP prepared according to the present invention is not particularly limited, but the non-aqueous solvent, main electrolyte, And other additives can be added to obtain a desired electrolyte for a non-aqueous electrolyte battery.

Main electrolytes include LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , LiSbF ₆ , LiCF ₃ SO ₃ , LiN(SO ₂ CF ₃ ) ₂ , LiN(SO ₂ C ₂ F ₅ ) ₂ , LiN(SO ₂ CF ₃ ) Electrolytic lithium salt represented by (SO ₂ C ₄ F ₉ ), LiC(SO ₂ CF ₃ ) ₃ , LiPF ₃ (C ₃ F ₇ ) ₃ , LiB(CF ₃ ) ₄ , LiBF ₃ (C ₂ F ₅ ), etc. You can use

In addition, other additives include lithium difluoro(oxalato)borate, cyclohexyl benzene, t-butyl benzene, vinylene carbonate, vinylethylene carbonate, difluoroanisole, fluoroethylene carbonate, propane sultone, dimethylvinylene carbonate. Compounds having an overcharge prevention effect, negative electrode film formation effect, positive electrode protection effect, etc. can be used.

According to the manufacturing method of the present invention, by adding methyltrichlorosilane (MeSiCl ₃ ) to lithium hexafluorophosphate and oxalic acid and reacting, the chemical selectivity to LDFOP is very high, and high purity LDFOP can be efficiently and industrially manufactured. In addition, it is easy to remove by-products generated during the reaction.

1 is a ¹⁹ F NMR analysis result of the product obtained in Example 1.
2 is a ¹⁹ F NMR analysis result of the product obtained in Comparative Example 1.

Hereinafter, the present invention will be described in more detail by examples. It will be apparent to those skilled in the art that these examples are for illustrative purposes only, and that the scope of the present invention is not limited to these examples.

Example 1: Preparation of lithium difluorobis (oxalato) phosphate (LDFOP) solid

Lithium hexafluorophosphate (LiPF ₆ ) 26 g (0.171 mol) was added to a 500 ml three-neck double jacketed reactor with a magnetic stirrer in a glove box, and 174 g of anhydrous ethyl methyl carbonate was dissolved while sufficiently stirring, and then 30.8 g of anhydrous oxalic acid was added. . The molar ratio of lithium hexafluorophosphate and oxalic acid was 1.00:2.00. The double jacketed reactor was taken out to the outside of the gloss box, and the circulator was connected to the double jacketed reactor, and then the internal temperature was set to 40°C to increase the internal temperature, and a magnetic stirrer was installed underneath and sufficiently stirred.

Then, 51.2 g of methyltrichlorosilane was added dropwise to the mixture of LiPF ₆ , oxalic acid and ethyl methyl carbonate over 1 hour through a dropping funnel. The molar ratio of lithium hexafluorophosphate and methyltrichlorosilane was 1.00:2.00. MeSiF ₃ and HCl gas were generated simultaneously with the initiation of dropping. After the addition was completed, the temperature of the circulator was raised to 50° C., and stirring was continued for an additional 2 hours to complete the reaction. After completion of the reaction, a transparent colorless filtrate was obtained.

The main by-products, MeSiF ₃ and HCl gas, were first passed through 500 g of water cooled with an ice bath and then additionally passed through a -50°C low temperature trap.

It was heated within 50 to 55° C. and dried for 3 hours with a vacuum pump to obtain 37.5 g (yield 87%) of an off-white target. As a result of measuring ¹⁹ F NMR by dissolving in acetonitrile-d ₃ , as shown in FIG. 1, the LDFOP/LTFOP molar ratio was 100:0, showing a chemoselectivity of 100.0%.

Example 2: Preparation of lithium difluorobis (oxalato) phosphate (LDFOP) solution

65.0 g (0.428 mol) of lithium hexafluorophosphate (LiPF ₆ ) was added to a 1000 ml three-neck double jacketed reactor with a magnetic stirrer in a glove box, 435 g of anhydrous ethyl methyl carbonate was added, dissolved with sufficient stirring, and 90.0 g of anhydrous oxalic acid was added. I did. The molar ratio of lithium hexafluorophosphate and oxalic acid was 1.00:2.00. The double jacketed reactor was taken out to the outside of the gloss box, and the circulator was connected to the double jacketed reactor, and then the internal temperature was set to 40°C to increase the internal temperature, and a magnetic stirrer was installed underneath and sufficiently stirred.

Then, 127.9 g of methyl trichlorosilane was added dropwise to the mixture of LiPF ₆ , oxalic acid and ethyl methyl carbonate over 1 hour through a dropping funnel. The molar ratio of lithium hexafluorophosphate and methyltrichlorosilane was 1.00:2.00. MeSiF ₃ and HCl gas were generated simultaneously with the initiation of dropping. After the addition was completed, the temperature of the circulator was raised to 50° C., and stirring was continued for an additional 2 hours to complete the reaction. After completion of the reaction, a transparent colorless filtrate was obtained.

The main by-products, MeSiF ₃ and HCl gas, were first passed through 2000 g of water cooled with an ice bath and then additionally passed through a -50°C low temperature trap.

After cooling the reaction solution to room temperature, it was dried with a vacuum pump to remove about 20 g of residual by-products and ethyl methyl carbonate solvent to obtain 507 g of the target product in a solution state. Take 2.02 g of the target substance in solution, add 51.4 mg of the internal standard, dissolve in acetonitrile-d ₃ , and measure ¹⁹ F NMR. As a result, the concentration of LDFOP was 18.6 wt% and the yield was calculated as 87.6%. The LDFOP/LTFOP molar ratio was 100:0, which showed a chemoselectivity of 100.0%.

Example 3: Preparation of lithium difluorobis(oxalato)phosphate (LDFOP) solid

Lithium hexafluorophosphate 26 g (0.171 mol) was added to a 500 ml three-neck double jacketed reactor with a magnetic stirrer in a glove box, and 174 g of anhydrous ethyl methyl carbonate was dissolved while sufficiently stirring, and then 30.8 g of oxalic anhydride was added. The molar ratio of lithium hexafluorophosphate and oxalic acid was 1.00:2.00. The double jacketed reactor was taken out to the outside of the gloss box, and the circulator was connected to the double jacketed reactor, and the internal temperature was set to 40°C to increase the internal temperature, and a magnetic stirrer was installed at the bottom to sufficiently stir.

Then, 46.1 g of methyl trichlorosilane was added dropwise over 1 hour to the mixture of LiPF ₆ , oxalic acid and ethyl methyl carbonate through a dropping funnel. The molar ratio of lithium hexafluorophosphate and methyltrichlorosilane was 1.00:1.80. MeSiF ₃ and HCl gas were generated simultaneously with the initiation of dropping. After the addition was completed, the temperature of the circulator was raised to 50° C., and stirring was continued for an additional 2 hours to complete the reaction. After completion of the reaction, a transparent colorless filtrate was obtained.

The main by-products, MeSiF ₃ and HCl gas, were first passed through 500 g of water cooled with an ice bath and then additionally passed through a -50°C low temperature trap.

It was further dried for 3 hours with a vacuum pump while heating within 50 to 55° C. to obtain 36.8 g (yield 85.3%) of an off-white target. As a result of dissolving in acetonitrile-d ₃ and measuring ¹⁹ F NMR, the LDFOP/LTFOP molar ratio was 100:0, showing a chemoselectivity of 100.0%.

Example 4: Preparation of lithium difluorobis(oxalato)phosphate (LDFOP) solid

Lithium hexafluorophosphate 26 g (0.171 mol) was added to a 500 ml three-neck double jacketed reactor with a magnetic stirrer in a glove box, and 174 g of anhydrous ethyl methyl carbonate was dissolved while sufficiently stirring, and then 30.8 g of anhydrous oxalic acid was added. The molar ratio of lithium hexafluorophosphate and oxalic acid was 1.00:2.00. The double jacketed reactor was taken out to the outside of the gloss box, and the circulator was connected to the double jacketed reactor, and the internal temperature was set to 40°C to increase the internal temperature, and a magnetic stirrer was installed at the bottom to sufficiently stir.

Then, 40.9 g of methyl trichlorosilane was added dropwise over 1 hour to the mixture of LiPF ₆ , oxalic acid and ethyl methyl carbonate through a dropping funnel. The molar ratio of lithium hexafluorophosphate and methyltrichlorosilane was 1.00:1.60. MeSiF ₃ and HCl gas were generated simultaneously with the initiation of dropping. After the addition was completed, the temperature of the circulator was raised to 50° C., and stirring was continued for an additional 2 hours to complete the reaction. After completion of the reaction, a transparent colorless filtrate was obtained.

The main by-products, MeSiF ₃ and HCl gas, were first passed through 500 g of water cooled with an ice bath and then additionally passed through a -50°C low temperature trap.

While heating within 50 to 55° C., it was further dried with a vacuum pump for 3 hours to obtain 37.0 g (yield 85.8%) of an off-white target. As a result of dissolving in acetonitrile-d ₃ and measuring ¹⁹ F NMR, the LDFOP/LTFOP molar ratio was 21.0:1, showing a chemoselectivity of 95.5%.

Example 5: Preparation of lithium difluorobis(oxalato)phosphate (LDFOP) solid

Lithium hexafluorophosphate 26 g (0.171 mol) was added to a 500 ml three-neck double jacketed reactor with a magnetic stirrer in a glove box, and 174 g of anhydrous ethyl methyl carbonate was dissolved while sufficiently stirring, and then 30.8 g of anhydrous oxalic acid was added. The molar ratio of lithium hexafluorophosphate and oxalic acid was 1.00:2.00. The double jacketed reactor was taken out to the outside of the gloss box, and the circulator was connected to the double jacketed reactor, and the internal temperature was set to 40°C to increase the internal temperature, and a magnetic stirrer was installed at the bottom to sufficiently stir.

Then, 35.8 g of methyl trichlorosilane was added dropwise over 1 hour to the mixture of LiPF ₆ , oxalic acid and ethyl methyl carbonate through a dropping funnel. The molar ratio of lithium hexafluorophosphate and methyltrichlorosilane was 1.00:1.40. MeSiF ₃ and HCl gas were generated simultaneously with the initiation of dropping. After completion of the addition, the circulator temperature was raised to 50° C., and the reaction was terminated by continuing to stir for an additional 2 hours. After completion of the reaction, a transparent colorless filtrate was obtained.

The main by-products, MeSiF ₃ and HCl gas, were first passed through 500 g of water cooled with an ice bath and then additionally passed through a -50°C low temperature trap.

It was further dried for 3 hours with a vacuum pump while heating within 50 to 55° C. to obtain 37.2 g (yield 86.3%) of an off-white target. As a result of measuring ¹⁹ F NMR by dissolving in acetonitrile-d ₃ , the LDFOP/LTFOP molar ratio was 8.4:1, showing a chemoselectivity of 89.4%.

Example 6: Preparation of lithium difluorobis(oxalato)phosphate (LDFOP) solid

Lithium hexafluorophosphate 26 g (0.171 mol) was added to a 500 ml three-neck double jacketed reactor with a magnetic stirrer in a glove box, and 174 g of anhydrous ethyl methyl carbonate was dissolved while sufficiently stirring, and then 30.8 g of anhydrous oxalic acid was added. The molar ratio of lithium hexafluorophosphate and oxalic acid was 1.00:2.00. The double jacketed reactor was taken out of the gloss box, and the circulator was connected to the double jacketed reactor and then set to 25°C, and a magnetic stirrer was installed underneath, followed by sufficiently stirring.

Then, 51.2 g of methyl trichlorosilane was added dropwise over 1 hour to the mixture of LiPF ₆ , oxalic acid and ethyl methyl carbonate through a dropping funnel. The molar ratio of lithium hexafluorophosphate and methyltrichlorosilane was 1.00:2.00. MeSiF ₃ and HCl gas were generated simultaneously with the initiation of dropping. After the addition was completed, stirring was continued for 3 hours while maintaining the circulator temperature at 25°C to terminate the reaction. After completion of the reaction, a transparent colorless filtrate was obtained.

The main by-products, MeSiF ₃ and HCl gas, were first passed through 500 g of water cooled with an ice bath and then additionally passed through a -50°C low temperature trap.

It was heated within 50 to 55° C. and dried for 3 hours with a vacuum pump to obtain 37.5 g (yield 87%) of an off-white target. As a result of dissolving in acetonitrile-d ₃ and measuring ¹⁹ F NMR, the LDFOP/LTFOP molar ratio was 16.7:1, showing a chemoselectivity of 94.4%.

Example 7: Preparation of lithium difluorobis(oxalato)phosphate (LDFOP) solid

Lithium hexafluorophosphate 26 g (0.171 mol) was added to a 500 ml three-neck double jacketed reactor with a magnetic stirrer in a glove box, and 174 g of anhydrous ethyl methyl carbonate was dissolved while sufficiently stirring, and then 30 g of anhydrous oxalic acid was added. The molar ratio of lithium hexafluorophosphate and oxalic acid was 1.00:1.95. The double jacketed reactor was taken out to the outside of the gloss box, and the circulator was connected to the double jacketed reactor, and the internal temperature was set to 40°C to increase the internal temperature, and a magnetic stirrer was installed at the bottom to sufficiently stir.

Then, 51.2 g of methyl trichlorosilane was added dropwise over 1 hour to the mixture of LiPF ₆ , oxalic acid and ethyl methyl carbonate through a dropping funnel. The molar ratio of lithium hexafluorophosphate and methyltrichlorosilane was 1.00:2.00. MeSiF ₃ and HCl gas were generated simultaneously with the initiation of dropping. After completion of the addition, the circulator temperature was raised to 50° C., and the reaction was terminated by continuing to stir for an additional 2 hours. After completion of the reaction, a transparent colorless filtrate was obtained.

The main by-products, MeSiF ₃ and HCl gas, were first passed through 500 g of water cooled with an ice bath and then additionally passed through a -50°C low temperature trap.

While heating within 50 to 55° C., it was further dried with a vacuum pump for 3 hours to obtain 36.3 g (yield 84.2%) of an off-white target. As a result of dissolving in acetonitrile-d ₃ and measuring ¹⁹ F NMR, the LDFOP/LTFOP molar ratio was 100:0, showing a chemoselectivity of 100.0%.

Example 8: Preparation of lithium difluorobis(oxalato)phosphate (LDFOP) solid

Lithium hexafluorophosphate 26 g (0.171 mol) was added to a 500 ml three-neck double jacketed reactor with a magnetic stirrer in a glove box, and 174 g of anhydrous ethyl methyl carbonate was dissolved while sufficiently stirring, and then 32.4 g of anhydrous oxalic acid was added. The molar ratio of lithium hexafluorophosphate and oxalic acid was 1.00:2.1. The double jacketed reactor was taken out to the outside of the gloss box, and the circulator was connected to the double jacketed reactor, and the internal temperature was set to 40°C to increase the internal temperature, and a magnetic stirrer was installed at the bottom to sufficiently stir.

Then, 51.2 g of methyl trichlorosilane was added dropwise over 1 hour to the mixture of LiPF ₆ , oxalic acid and ethyl methyl carbonate through a dropping funnel. The molar ratio of lithium hexafluorophosphate and methyltrichlorosilane was 1.00:2.00. MeSiF ₃ and HCl gas were generated simultaneously with the initiation of dropping. After completion of the addition, the circulator temperature was raised to 50° C., and the reaction was terminated by continuing to stir for an additional 2 hours. After completion of the reaction, a transparent colorless filtrate was obtained.

The main by-products, MeSiF ₃ and HCl gas, were first passed through 500 g of water cooled with an ice bath and then additionally passed through a -50°C low temperature trap.

It was further dried for 3 hours with a vacuum pump while heating within 50 to 55°C to obtain 37.4 g (yield 86.7%) of an off-white target. As a result of dissolving in acetonitrile-d ₃ and measuring ¹⁹ F NMR, the LDFOP/LTFOP molar ratio was 100:0, showing a chemoselectivity of 100.0%.

Comparative Example 1: Preparation of lithium difluorobis (oxalato) phosphate (LDFOP) solid using silicon tetrachloride

Lithium hexafluorophosphate 26 g (0.171 mol) was added to a 500 ml three-neck double jacketed reactor with a magnetic stirrer in a glove box, and 174 g of diethyl carbonate was added to dissolve while sufficiently stirring, and then 30.8 g of anhydrous oxalic acid was added. The molar ratio of lithium hexafluorophosphate and oxalic acid was 1.00:2.00. The double jacketed reactor was taken out to the outside of the gloss box, and the circulator was connected to the double jacketed reactor, and the internal temperature was set to 40°C to increase the internal temperature, and a magnetic stirrer was installed at the bottom to sufficiently stir.

Then, 29.96 g of silicon tetrachloride (SiCl ₄ ) was added dropwise over 1 hour to the mixture of LiPF ₆ , oxalic acid and diethyl carbonate through a dropping funnel. The molar ratio of lithium hexafluorophosphate and silicon tetrachloride was 1.00:1.03. Simultaneously with the initiation of dropping, SiF ₄ and HCl gases were generated. After completion of the addition, stirring was continued for 2 hours while maintaining the circulator temperature at 40° C. to terminate the reaction. After completion of the reaction, a transparent colorless filtrate was obtained.

The main by-products, SiF ₄ and HCl gas, were collected by passing 500 g of a 30% NaOH aqueous solution cooled with an ice bath.

While heating within 50 to 55° C., it was further dried with a vacuum pump for 3 hours to obtain 36.3 g (yield 84.2%) of an off-white target. As a result of measuring ¹⁹ F NMR by dissolving in acetonitrile-d ₃ , as shown in FIG. 2, the LDFOP/LTFOP molar ratio was 3.24:1, showing a chemoselectivity of 76.4%.

Comparative Example 2: Preparation of lithium difluorobis (oxalato) phosphate (LDFOP) using dimethyldichlorosilane

Synthesis was carried out using dimethyldichlorosilane (Me ₂ SiCl ₂ ) instead of methyl trichlorosilane (MeSiCl ₃ ) under the same conditions as in Example 1. Me ₂ SiCl ₂ After dropwise addition, the solid in the reaction solution did not dissolve, and even when the reaction temperature was raised to 50° C. and stirred overnight, the solid remained as it was. A part of the reaction solution was taken, filtered, and dissolved in acetonitrile-d ₃ to measure ¹⁹ F NMR. As a result, lithium hexafluorophosphate remained almost as it was, and LDFOP or LTFOP was not observed.

Claims (11)

Including the step of reacting by adding methyl trichlorosilane (MeSiCl ₃ ) to lithium hexafluorophosphate (LiPF ₆ ) and oxalic acid,
The molar ratio of the lithium hexafluorophosphate and oxalic acid is 1:1.8 to 1:2.2,
The molar ratio of the lithium hexafluorophosphate and methyl trichlorosilane is 1:1.2 to 1:2.5,
Method for producing lithium difluorobis (oxalato) phosphate (LDFOP) wherein the reaction temperature is in the range of 20 to 70°C. delete delete The method of claim 1, wherein the molar ratio of lithium hexafluorophosphate and oxalic acid is 1:1.95 to 1:2.1, the molar ratio of lithium hexafluorophosphate and methyltrichlorosilane is 1:1.8 to 1:2.0, and lithium di A manufacturing method, characterized in that the fluorobis (oxalato) phosphate (LDFOP) is chemically selectively produced. delete The method of claim 1, wherein the reaction is carried out in the range of 20 to 45°C, and then the temperature is raised to the range of 50 to 70°C to react. The production method according to any one of claims 1, 4 and 6, wherein the reaction is performed in a non-aqueous solvent. The method according to claim 7, wherein the non-aqueous solvent is at least one solvent selected from the group consisting of cyclic carbonates, chain carbonates, chain nitriles, cyclic esters, chain esters, and chain halogenated solvents. The method of claim 1, wherein lithium difluorobis(oxalato)phosphate (LDFOP) is produced with a chemoselectivity of 80% or more. The method of claim 1, wherein lithium difluorobis (oxalato) phosphate (LDFOP) is produced with 100% chemoselectivity. The method of claim 7, comprising the step of obtaining 10 to 30 wt% lithium difluorobis (oxalato) phosphate (LDFOP) solution by removing or adding a part of the non-aqueous solvent after performing the reaction in a non-aqueous solvent. Manufacturing method.

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