KR101684377B1 - Process for preparing lithium difluorophosphate - Google Patents

Abstract

The present invention relates to a process for producing lithium difluorophosphate (LiPO ₂ F ₂ ) comprising reacting lithium hexafluorophosphate (LiPF ₆ ) and a silane compound together with water. According to the production method of the present invention, it is possible to economically and industrially produce lithium difluorophosphate used as a non-aqueous electrolyte additive for a lithium secondary battery in a comparatively short time.

Description

The present invention relates to a process for preparing lithium difluorophosphate,

The present invention relates to a process for economically and industrially producing lithium difluorophosphate which is used as a non-aqueous electrolyte additive for lithium secondary batteries.

2. Description of the Related Art Recently, the demand for secondary batteries has been rapidly increasing. In particular, portable electronic devices such as mobile phones, notebooks, and PCs are rapidly spreading, and thus demand for lightweight and high performance batteries for driving them is continuously increasing. In addition, it is expected to be utilized as a secondary battery for automobiles in addition to small-sized applications. Among them, lithium ion batteries are attracting attention as high-performance batteries satisfying such market demands.

A non-aqueous electrolyte is mainly used for such a lithium ion battery. It has been reported that when lithium difluorophosphate represented by the following formula (1) is added to an electrolytic solution, it acts on the electrode interface to improve high-temperature cycle characteristics (Japanese Patent Laid- -067279].

[Chemical Formula 1]

LiPO ₂ F ₂

The lithium difluorophosphate of Formula 1 is known to be prepared by various methods. First, Japanese Patent Application Laid-Open No. 2005-219994 discloses a method for producing lithium difluorophosphate by reacting LiPF ₆ with silicon dioxide as shown in Reaction Scheme 1 below. However, the above method has a problem that it takes 72 hours to complete the reaction at a reaction temperature of 50 ° C.

[Reaction Scheme 1]

U.S. Patent No. 8,980,214 discloses a process for producing lithium difluorophosphate by reacting lithium carbonate and LiPF ₆ in a nonaqueous solvent as shown in Reaction Scheme 2 below. However, this method also requires a long reaction time at 72 ° C for 72 hours at a reaction temperature of 50 ° C. The process also requires an additional process to remove the lithium fluoride produced as a by-product.

[Reaction Scheme 2]

Japanese Patent Laid-Open No. 11-067279 Japanese Patent Application Laid-Open No. 2005-219994 U.S. Patent No. 8,980,214

The present invention has been made to solve the above problems, and an object of the present invention is to provide a method for easily and economically and industrially producing lithium difluorophosphate from a raw material which is easy to purchase and economical.

Another object of the present invention is to provide a method for producing lithium difluorophosphate in a relatively short time in a high yield.

The present invention relates to a process for producing lithium difluorophosphate (LiPO ₂ F ₂ ) comprising reacting lithium hexafluorophosphate (LiPF ₆ ) with a silane compound represented by the following formula (2), (3) ≪ / RTI >

(2)

(3)

[Chemical Formula 4]

In this formula,

R ₁ , R ₂ and R ₃ are each independently hydrogen, a C ₁ -C ₆ alkyl group or a C ₂ -C ₆ alkenyl group, preferably hydrogen, methyl, ethyl or vinyl, more preferably methyl, R ₁ and R ₂ are methyl and R ₃ is vinyl,

X is halogen, preferably chloro, bromo or iodo, more preferably chloro.

In the present specification, the C ₁ -C ₆ alkyl group means a linear or branched hydrocarbon group having 1 to 6 carbon atoms, and includes, for example, methyl, ethyl, n-propyl, It is not.

As used herein, a C ₂ -C ₆ alkenyl group means a straight or branched unsaturated hydrocarbon having 2 to 6 carbon atoms having at least one carbon-carbon double bond, such as vinyl, 1-propenyl, 2 - propenyl, and the like.

The silane compounds of the formulas 2 to 4, such as haloalkylsilane and haloalkylalkenylsilane, particularly chlorotrimethylsilane, dichlorodimethylsilane, methyltrichlorosilane and chlorodimethylvinylsilane, which are used in the present invention, are commercially available Do.

According to the production process of the present invention, LiPF ₆ as a reactant; A compound represented by Formula 2, Formula 3 or Formula 4; And water, a lithium difluorophosphate can be produced with a high yield of 70% or more within a short reaction time of 5 hours or less, for example, 2 hours to 2 hours 30 minutes (see Examples 1 to 4) .

In one embodiment of the present invention, the molar ratio of the compound represented by the general formula (2) to lithium hexafluorophosphate (LiPF ₆ ) is 1: 3.8 to 4.2, preferably 1: 3.9 to 4.1, to be.

The molar ratio of the compound represented by the formula (3) or (4) to lithium hexafluorophosphate (LiPF ₆ ) is 1: 1.8 to 2.2, preferably 1: 1.9 to 2.1, more preferably 1: 2.

In one embodiment of the present invention, the molar ratio of water to lithium hexafluorophosphate (LiPF ₆ ) is 1: 1.8 to 2.2, preferably 1: 1.9 to 2.1, more preferably 1: 2.

The production method according to one embodiment of the present invention may include a step of dissolving LiPF ₆ in a nonaqueous solvent and reacting it with a silane compound represented by the general formula (2), (3) or (4) and water.

As the non-aqueous solvent used in the present invention, at least one solvent selected from the group consisting of cyclic carbonates, chain carbonates, chain nitriles, cyclic esters, chain esters, cyclic ethers, chain ethers and chain halogenated solvents can be used. Examples of the solvent include cyclic carbonates such as propylene carbonate, ethylene carbonate and butylene carbonate, chain carbonates such as diethyl carbonate, dimethyl carbonate and ethyl methyl carbonate, chain nitriles such as acetonitrile and propionitrile, Cyclic esters such as lactone, chain esters such as ethyl acetate and ethyl propionate, cyclic ethers such as 2-methyltetrahydrofuran and tetrahydrofuran, dibutyl ether, 1,2-dimethoxyethane, 1,2-diethoxyethane , Ethoxymethoxyethane and the like, and chain halogenating solvents such as dichloromethane and 1,2-dichloroethane, but the present invention is not limited thereto.

It is preferable to use dehydrated these non-aqueous solvents, and the water concentration in the non-aqueous solvent used in the present invention is preferably 500 ppm by weight or less. When the water concentration exceeds 500 ppm by weight, LiPF ₆ and LiPO ₂ F ₂ are not preferable because they are hydrolyzed.

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 wt%, more preferably 5 wt%, and the upper limit is preferably 40 wt% %, More preferably 30% by weight. If the concentration is less than 1% by weight, the reaction rate is slow and the solvent amount is increased, which is not economical. On the other hand, if the concentration exceeds 40% by weight, the viscosity of the solution may increase and it may be difficult to perform the reaction smoothly.

In one embodiment of the present invention, the reaction temperature is usually in the range of 5 to 60 ° C, preferably in the range of 10 to 30 ° C. If the reaction temperature is less than 5 ° C, the reaction time becomes long and is not economical. If the reaction temperature exceeds 60 ° C, the byproducts such as decomposition of the product and the raw material LiPF ₆ may be increased and adverse effects may be caused.

The reaction byproducts produced in the production process of the present invention can be removed using an effective gas trapping device because they have a low boiling point or can be easily removed in a gaseous state. By increasing the reaction temperature, the fluorinated silane compound and the hydrogen halide such as hydrochloric acid gas, which are produced by-products, can be removed, but can be more effectively removed by reduced pressure (10 to 50 mmHg).

In the production method of the present invention, it is preferable that the reaction is carried out in an atmosphere containing no water other than the water used for the reaction, because lithium difluorophosphate is hydrolyzed by moisture. For example, it is preferable to carry out the reaction in an atmosphere of an inert gas such as nitrogen or argon.

The method for preparing the electrolyte for the non-aqueous electrolyte cell using the lithium difluorophosphate produced according to the present invention is not particularly limited, but it is preferable that the non-aqueous solvent, the main electrolyte, and the other additives such as lithium difluorophosphate An electrolyte solution for a desired non-aqueous electrolyte cell can be obtained.

As the main electrolyte _{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) _{(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) an electrolyte lithium salt, represented by such as Can be used.

Examples of other additives include lithium salts such as lithium difluorobis (oxalato) phosphate, lithium tetrafluoro (oxalato) phosphate, lithium difluoro (oxalato) borate, cyclohexylbenzene, biphenyl, (Negative electrode) film-forming effect, a compound having a positive electrode (protective) effect, etc., for example, an overcharge preventing effect such as vinylene carbonate, vinyl ethylene carbonate, difluoroanisole, fluoroethylene carbonate, propane sultone, dimethylvinylene carbonate Can be used.

According to the production method of the present invention, lithium difluorophosphate, which is used as an effective additive for improving the performance of a non-aqueous electrolyte cell, can be economically produced from LiPF _{6 in} a short time by using a silane compound and water, It can be industrially produced.

Hereinafter, the present invention will be described in more detail with reference to Examples. It should be apparent to those skilled in the art that these embodiments are for illustrative purpose only and that the scope of the present invention is not limited to these embodiments.

Example  One: Chlorotrimethylsilane  Used Of lithium difluorophosphate  Produce

To a 500 mL three-neck round bottom (RB) PFA flask connected to a gas collector was added 60.0 g of a 30% LiPF ₆ dimethyl carbonate solution in an argon atmosphere. The mixture was cooled to 5 占 폚 and 4.27 g of water and 54.1 g of chlorotrimethylsilane were added. The mixture was heated to 20 DEG C and stirred for 2 hours, and then the glassy gas was removed under reduced pressure (20 mmHg). The mixture was cooled to 10 DEG C, stirred for 1 hour and filtered. The solid obtained by filtration was vacuum-dried at 60 DEG C for 12 hours to obtain 12.4 g (yield: 97%) of the target compound.

¹⁹ F-NMR 400 MHz (Acetone-d6, ppm): -83.52 (s), -85.98 (s)

FT-IR (cm ^-1 ): 1263, 1145, 926, 879, 536, 495

Example  2: Dichlorodimethylsilane  Used Of lithium difluorophosphate  Produce

To a 500 mL three-necked round bottom (RB) PFA flask connected to a gas collector was added 100.0 g of a 13% LiPF ₆ ethylmethyl carbonate solution in an argon atmosphere. After cooling to 5 캜, 3.08 g of water and 23.2 g of dichlorodimethylsilane were added. The mixture was heated to 20 DEG C, stirred for 2 hours, and stirred at 30 DEG C for 30 minutes. The glassy gas was removed under reduced pressure (20 mmHg). The mixture was cooled to 10 DEG C, stirred for 1 hour and filtered. The solid obtained by filtration was vacuum-dried at 60 DEG C for 12 hours to obtain 8.0 g (yield: 87%) of the target compound.

¹⁹ F-NMR 400 MHz (Acetone-d6, ppm): -83.52 (s), -85.98 (s)

FT-IR (cm ^-1 ): 1264, 1145, 926, 879, 535, 495

Example  3: Methyl trichlorosilane  Used Of lithium difluorophosphate  Produce

A 500 mL three-necked round bottom (RB) PFA flask connected to a gas collector was charged with 120.0 g of a 15% LiPF ₆ dimethyl carbonate solution in an argon atmosphere. The mixture was cooled to 5 DEG C, and 4.27 g of water and 26.6 g of methyltrichlorosilane were added. The mixture was heated to 20 DEG C, stirred for 2 hours, and stirred at 30 DEG C for 30 minutes. The glassy gas was removed under reduced pressure (20 mmHg). The mixture was cooled to 10 DEG C, stirred for 1 hour and filtered. The solid obtained by filtration was vacuum-dried at 60 DEG C for 12 hours to obtain 8.9 g (yield 70%) of the target compound.

¹⁹ F-NMR 400 MHz (Acetone-d6, ppm): -83.39 (s), -85.85 (s)

FT-IR (cm ^-1 ): 1263, 1146, 927, 880, 535, 496

Example  4: Chlorodimethylvinylsilane  Used Of lithium difluorophosphate  Produce

A 500 mL 3-neck round bottom (RB) PFA flask connected to a gas collector was charged with 45.0 g of a 13% LiPF ₆ ethylmethyl carbonate solution in an argon atmosphere. The mixture was cooled to 5 占 폚 and 1.39 g of water and 19.5 g of chlorodimethylvinylsilane were added. The mixture was heated to 20 DEG C and stirred for 2 hours, and then the glassy gas was removed under reduced pressure (20 mmHg). The mixture was cooled to 10 DEG C, stirred for 1 hour and filtered. The solid obtained by filtration was vacuum-dried at 60 DEG C for 12 hours to obtain 3.9 g (yield: 94%) of the target compound.

¹⁹ F-NMR 400 MHz (Acetone-d6, ppm): -83.52 (s), -85.98 (s)

FT-IR (cm ^-1 ): 1263, 1145, 926, 879, 536, 495

Claims (12)

Reacting lithium hexafluorophosphate (LiPF ₆ ) with a silane compound represented by the following formula (2), (3) or (4) with water; And
Method of manufacturing a lithium phosphate lithium phosphate (LiPO ₂ F ₂₎ difluoro comprises a filtration (LiPO ₂ F ₂₎ in the difluoro solid from the reaction product:
(2)

(3)

[Chemical Formula 4]

In this formula,
R ₁ , R ₂ and R ₃ are each independently a C ₁ -C ₆ alkyl group or a C ₂ -C ₆ alkenyl group,
X is halogen. The process according to claim ₁ , wherein R ₁ , R ₂ and R ₃ are each independently hydrogen, methyl, ethyl or vinyl. The method of claim 1, wherein, R _1, R ₂ and R ₃ is a process for producing both methyl. The process according to claim 1, wherein R ₁ and R ₂ are methyl and R ₃ is vinyl. 2. The process according to claim 1, wherein X is chloro. The process according to claim 1, wherein the molar ratio of the compound represented by the general formula (2) to lithium hexafluorophosphate (LiPF ₆ ) is 1: 3.8 to 4.2. The production method according to claim 1, wherein the molar ratio of the compound represented by Formula (3) or (4) to lithium hexafluorophosphate (LiPF ₆ ) is 1: 1.8 to 2.2. The process according to claim 1, wherein the molar ratio of water to lithium hexafluorophosphate (LiPF ₆ ) is 1: 1.8 to 2.2. The process according to any one of claims 1 to 8, wherein the reaction is carried out in a non-aqueous solvent. The process according to claim 9, wherein the nonaqueous solvent is at least one solvent selected from the group consisting of cyclic carbonates, chain carbonates, chain nitriles, cyclic esters, chain esters, cyclic ethers, chain ethers and chain halogenated solvents. The process according to any one of claims 1 to 8, wherein the reaction temperature is from 5 to 60 캜. 9. The process according to any one of claims 1 to 8, further comprising depressurizing and removing the reaction byproduct.