Method for producing lithium difluorophosphate for lithium secondary battery

Abstract

The present invention relates to a method for producing lithium difluorophosphate salt in high yield using low-cost raw materials. In particular, it relates to a method for producing high-purity and high-yield lithium difluorophosphate salt without using lithium hexafluorophosphate salt. Therefore, the lithium difluorophosphate salt produced by the present invention can be used in an electrolyte for a lithium secondary battery, and when used in an electrolyte for a lithium secondary battery, it has effects such as electrochemical characteristics, output, and gas reduction.

Description

Technical Field

[0001] The present invention relates to a method for producing lithium difluorophosphate salt in high yield using low-cost raw materials. The present invention also relates to lithium difluorophosphate salt with reduced impurities. In particular, the present invention relates to a method for producing lithium difluorophosphate salt with high purity and high yield without using lithium hexafluorophosphate salt, and to the high-purity lithium difluorophosphate salt produced therefrom. The lithium difluorophosphate salt produced by the present invention can be used in electrolytes for lithium secondary batteries, and when used in electrolytes for lithium secondary batteries, it has effects such as improvement of electrochemical characteristics, provision of high output, and reduction of gas.

Background Art

[0002] Lithium secondary batteries are widely used in the fields of small and advanced electronic devices such as mobile devices and notebook personal computers. With the popularization of electric vehicles (EVs), the development of medium and large-sized lithium secondary batteries with high capacity and electrochemical stability has also been carried out.

[0003] With the increasing demand for medium and large-sized lithium secondary batteries, the need for high-performance lithium secondary batteries has increased, and secondary batteries having performances such as high output, high energy density, gas reduction effect, and improved life have become necessary. Therefore, there is a need for the development of electrolytes suitable for such secondary batteries, and multifunctional additives for improving the functions of electrolytes have begun to attract attention. In particular, it has been known that lithium difluorophosphate salt is useful for improving the functions of electrolytes. Due to such market influences, the development of high-purity lithium difluorophosphate salt that can improve the battery life while having a low production cost is an urgent situation.

Summary of the Invention

Problems to be Solved by the Invention

[0004] As a conventional method for producing lithium difluorophosphate salt, LiPF 6The method using it is widely known and, schematically, is as shown in the following Reaction Formula 1. [Reaction Formula 1] [Chemical Formula]

[0005] The above reaction is a method of production using lithium hexafluorophosphate salt (LiPF 6 ) and various forms of siloxane, characterized by being produced without using water. However, the above method has the drawback that it generates fluorinated silane (SiF 2 (CH 3 ) 2 ) gas, which is a toxic substance, as a by-product, and a large amount of acidic by-products remain in the product, lithium difluorophosphate salt. Further, the above method has the drawback of high production cost because it uses expensive raw materials such as lithium hexafluorophosphate salt (LiPF 3 ) 2 which is also used as a lithium secondary battery electrolyte together with siloxane (-Si(CH 6 ). Therefore, there is an urgent need for a new method of producing lithium difluorophosphate salt that is more economical than the conventional production method and is environmentally friendly without generating toxic by-products.

[0006] Therefore, an object of the present invention is to provide a new production method for producing lithium difluorophosphate salt in an environmentally friendly and economical manner without using expensive siloxane and lithium hexafluorophosphate salt (LiPF 6 ) and without generating toxic fluorinated silane gas.

[0007] Another object of the present invention is to provide high-purity lithium difluorophosphate salt. [Means for Solving the Problems]

[0008] To solve the above problems, the present invention Step 1) Phosphoryl halide (POX of the following Chemical Formula 23 ) Reacting a compound, an oxidizing agent of the following Chemical Formula 3, and a lithium salt to produce a lithium dihalophosphate salt of the following Chemical Formula 4; and Step 2) Reacting the lithium dihalophosphate salt of Chemical Formula 4 with a fluoride salt of the following Chemical Formula 5 to produce a lithium difluorophosphate salt (LiPO 2 X 2 ); A method for producing a lithium difluorophosphate salt is provided, which includes the above steps.

[0009] [Chemical Formula 2] [Chemical Structure]

[0010] [Chemical Formula 3] [Chemical Structure]

[0011] [Chemical Formula 4] [Chemical Structure]

[0012] [Chemical Formula 5] MF n

[0013] [Chemical Formula 1] [Chemical Structure]

[0014] In the above chemical formulas X is Cl, Br or I, R1 and R2 are each independently H, a C1-10 alkyl group, a phenyl group, OH, OR3, NH 2 , NHR4, NR5R6, ONa, OK or ONH 4 , R3, R4, R5 and R6 are each independently a C1-10 alkyl group or a phenyl group, Both R1 and R2 can form a ring having 2 to 5 carbon atoms which may contain one or more hetero elements of O or N. M is H, Li, Na, K, Ca, Zn, Sb, Rb, Cs or an onium ion. n is 1 or 2.

[0015] The present invention also provides Step 1') reacting a phosphoryl halide (POX 3 ) compound of the following Chemical Formula 2, an oxidizing agent of the following Chemical Formula 3, and a fluoride salt of the following Chemical Formula 5 to produce a difluorophosphate (MPO 2 F 2 ) of the following Chemical Formula 6; and Step 2') reacting the difluorophosphate of Chemical Formula 6 with a lithium salt to produce a lithium difluorophosphate salt of the following Chemical Formula 1; A method for producing a lithium difluorophosphate salt (LiPO 2 F 2 ) is provided.

[0016] [Chemical Formula 2]

Chemical Formula

[0017] [Chemical Formula 3]

Chemical Formula

[0018] [Chemical Formula 5] MF n

[0019] [Chemical Formula 6]

Chemical Formula

[0020] [Chemical Formula 1]

Chemical Formula

[0021] In the above chemical formula X is Cl, Br or I, R1 and R2 are each independently H, a C1-10 alkyl group, a phenyl group, OH, OR3, NH 2 , NHR4, NR5R6, ONa, OK or ONH 4 wherein R3, R4, R5, and R6 are each independently a C1-10 alkyl group or a phenyl group, R1 and R2 can together form a ring having 2 to 5 carbon atoms which can contain one or more hetero elements of O or N, M is H, Li, Na, K, Ca, Zn, Sb, Rb, Cs or an onium ion, n is 1 or 2.

[0022] The present invention also provides a method for producing lithium difluorophosphate (LiPO 3 F 2 ) by reacting a phosphoryl fluoride (POF 2 ) compound of the following chemical formula 7, an oxidizing agent (R1R2C=O) of the following chemical formula 3, and a lithium salt.

[0023] [Chemical formula 7] [Chem.]

[0024] [Chemical formula 3] [Chem.]

[0025] [Chemical formula 1] [Chem.]

[0026] In the above chemical formula R1 and R2 are each independently H, a C1-10 alkyl group, a phenyl group, OH, OR3, NH 2 , NHR4, NR5R6, ONa, OK or ONH 4 wherein R3, R4, R5 and R6 are each independently a C1-10 alkyl group or a phenyl group, R1 and R2 can form a ring having 2 to 5 carbon atoms which can contain one or more hetero elements of O or N together.

[0027] The present invention also provides a lithium difluorophosphate salt containing 0 to 500 ppm by weight of F - , 0 to 500 ppm by weight of Cl - , 0 to 500 ppm by weight of SO 4 2― or 0 to 500 ppm by weight of PO 4 3- .

Advantages of the Invention

[0028] The production method according to the present invention has the advantage of excellent economy by not using expensive lithium hexafluorophosphate salt (LiPF 6 ). Further, the production method according to the present invention is environmentally friendly as no toxic fluorinated silane gas is generated, and can produce lithium difluorophosphate salt with a high purity of 97% or more and a high yield of 80% or more by a relatively simple production method. The lithium difluorophosphate salt of the present invention has the advantage that the contents of metal ion impurities and acidic ions such as hydrofluoric acid, hydrochloric acid, sulfuric acid, and phosphoric acid are extremely low, and when used in an electrolyte for a lithium secondary battery, the electrical characteristics, output, and gas reduction characteristics can be improved.

Modes for Carrying Out the Invention

[0029] The following is a more detailed description of the present invention. Terms and words used in this specification and the claims should not be construed as limited to their ordinary or dictionary meanings. In accordance with the principle that the inventor can appropriately define the concept of the terms in order to explain his own invention in the best way, they should be construed in a meaning and concept consistent with the technical idea of the present invention.

[0030] The conventional method for commercially producing lithium difluorophosphate (LiPO 2 F 2 ) is to use lithium hexafluorophosphate (LiPF 6 ). In most of the processes using lithium hexafluorophosphate (LiPF 6 ), toxic gases such as hydrofluoric acid or fluorinated silane are generated, so it is essential to construct separate purification facilities. Also, it is not only difficult to completely remove hydrofluoric acid and fluorinated silane generated as by-products in the manufacturing method using lithium difluorophosphate (LiPO 2 F 2 ), but when producing, storing, and distributing electrolytes with lithium difluorophosphate containing such impurities, side reactions occur over time, generating more impurities and causing a secondary problem of reducing purity. One of the by-products generated at this time is hydrofluoric acid, which may cause problems such as oxidizing the electrodes in the battery and the packaging container of the metal battery when dissolved in the electrolyte and injected into the battery.

[0031] In addition, lithium hexafluorophosphate (LiPF 6 ) is always used in lithium secondary battery electrolytes and is the most widely used material. Therefore, as the demand for lithium secondary batteries increases, there is a problem that its cost becomes higher. Therefore, in order to manufacture lithium difluorophosphate (LiPO 2 F 2 ) at a competitive price and high purity, the development of manufacturing technologies that do not use lithium hexafluorophosphate (LiPF 6 ) is an urgent situation.

[0032] Therefore, in the process of trying to develop a new, environmentally friendly and economical manufacturing method that does not use expensive siloxane and lithium hexafluorophosphate salt (LiPF 6 ) and does not generate toxic fluorinated silane gas, the inventors have developed a method using phosphoryl halide (POX 3 ) compounds, which are inexpensive and easily purchasable starting materials, and completed the present invention. That is, the present invention can easily and economically produce lithium difluorophosphate salt with high purity and high yield by preparing phosphoryl halide using an oxidizing agent containing a carbonyl group (C=O).

[0033] The present invention Step 1) reacting a phosphoryl halide compound of the following Chemical Formula 2, an oxidizing agent of the following Chemical Formula 3, and a lithium salt to produce a lithium dihalophosphate salt of the following Chemical Formula 4; and Step 2) reacting the lithium dihalophosphate salt of Chemical Formula 4 with a fluoride salt of the following Chemical Formula 5 to produce a lithium difluorophosphate salt of the following Chemical Formula 1; provides a method for producing a lithium difluorophosphate salt.

[0034] [Chemical Formula 2] [Chemical Formula 3]

[0035] [Chemical Formula 4] [Chemical Formula 5]

[0036] [Chemical Formula 4] [Chemical Formula 5]

[0037] [Chemical Formula 5] MF n

[0038] [Chemical Formula 1] [Chem.]

[0039] In the above chemical formula X is Cl, Br or I, R1 and R2 are each independently H, a C1-10 alkyl group, a phenyl group, OH, OR3, NH 2 , NHR4, NR5R6, ONa, OK or ONH 4 and R3, R4, R5 and R6 are each independently a C1-10 alkyl group or a phenyl group, R1 and R2 can together form a ring having 2 to 5 carbon atoms that can contain one or more hetero elements of O or N, M is H, Li, Na, K, Ca, Zn, Sb, Rb, Cs or an onium ion, n is 1 or 2.

[0040] When the method of the present invention is illustrated by a reaction formula, it is as shown in Reaction Formula 2. [Reaction Formula 2] [Chem.]

[0041] The present invention also Step 1') reacting a phosphoryl halide (POX 3 ) compound of the following Chemical Formula 2, an oxidizing agent of the following Chemical Formula 3, and a fluoride salt of the following Chemical Formula 5 to produce a difluorophosphate of the following Chemical Formula 6; and Step 2') reacting the difluorophosphate of Chemical Formula 6 with a lithium salt to produce a lithium difluorophosphate salt of the following Chemical Formula 1; A method for producing a lithium difluorophosphate salt is provided, which includes

[0042] [Chemical Formula 2] [Chem.]

[0043] [Chemical Formula 3]

Chem.

[0044] [Chemical Formula 5] MF n

[0045] [Chemical Formula 6]

Chem.

[0046] [Chemical Formula 1]

Chem.

[0047] In the above chemical formula X is Cl, Br or I, R1 and R2 are each independently H, a C1-10 alkyl group, a phenyl group, OH, OR3, NH 2 , NHR4, NR5R6, ONa, OK or ONH 4 and R3, R4, R5, and R6 are each independently a C1-10 alkyl group or a phenyl group, R1 and R2 can together form a ring having 2 to 5 carbon atoms that can contain one or more hetero elements of O or N, M is H, Li, Na, K, Ca, Zn, Sb, Rb, Cs or an onium ion, n is 1 or 2.

[0048] When the method of the present invention is illustrated by a reaction formula, it is as shown in the following Reaction Formula 3. [Reaction Formula 3]

Chem.

[0049] The present invention also reacts a phosphoryl fluoride (POF 3 ) compound of the following Chemical Formula 7, an oxidizing agent of the following Chemical Formula 3, and a lithium salt to produce a lithium difluorophosphate salt of the following Chemical Formula 1.

[0050] [Chemical Formula 7]

Chem.

[0051] [Chemical Formula 3]

Chem.

[0052] [Chemical Formula 1]

Chem.

[0053] In the above chemical formulas R1 and R2 are each independently H, a C1-10 alkyl group, a phenyl group, OH, OR3, NH 2 , NHR4, NR5R6, ONa, OK or ONH 4 , and R3, R4, R5 and R6 are each independently a C1-10 alkyl group or a phenyl group, R1 and R2 can together form a ring having 2 to 5 carbon atoms which can contain one or more hetero elements of O or N.

[0054] When the method of the present invention is diagrammed by a reaction formula, it is as shown in Reaction Formula 4. [Reaction Formula 4]

Chem.

[0055] The present invention relates to a lithium hexafluorophosphate salt (LiPF 6Without using (), a lithium difluorophosphate salt is produced using phosphoryl halide (POX 3 ). By suppressing the generation of hydrofluoric acid or fluorinated silane and not causing side reactions, a high-purity lithium difluorophosphate salt (LiPO 2 F 2 ) can be produced.

[0056] Conventionally, a method of producing a lithium difluorophosphate salt by oxidizing a lithium hexafluorophosphate salt (LiPF 6 ) typically uses expensive siloxane as an oxidizing agent. This method has the drawback of requiring the use of expensive reactants, and there are drawbacks such as the generation of hydrofluoric acid and fluorinated silane as by-products and their remaining in the lithium difluorophosphate. Finally, a large amount of yield loss occurs in the process of removing the remaining by-products such as hydrofluoric acid and fluorinated silane. In addition, a separate purification process is required to remove the unreacted siloxane. That is, the conventional method for producing lithium difluorophosphate has problems in terms of economy and the generation of toxic by-products and the associated purification treatment cost issues, while the present invention has the advantage of not having such problems.

[0057] The present invention uses phosphoryl halide instead of lithium hexafluorophosphate salt and uses a compound having a carbonyl group (C=O) as an oxidizing agent, thereby having the advantage of being able to stably produce high-purity lithium difluorophosphate without generating fluorinated silane by-products and without side reactions.

[0058] In the reaction formula 2, the step of reacting a phosphoryl halide (POX 3 ) compound, a compound having a carbonyl group (C=O) as an oxidizing agent, and a lithium salt, and the step of reacting the lithium dihalophosphate salt, which is the product of the above step, with a fluoride salt may be carried out by an in situ reaction, or may be carried out by a method of recovering the lithium dihalophosphate salt, which is an intermediate product, and then reacting it with a fluoride salt.

[0059] In the reaction formula 3, the step of reacting a phosphoryl halide (POX 3 ) compound with a compound having a carbonyl group (C=O) as an oxidizing agent and a fluoride salt, and the step of reacting the resulting difluorophosphate salt with a lithium salt may be carried out by an in-situ reaction, or may be carried out by a method of recovering the intermediate product difluorophosphate salt and then reacting it with a lithium salt.

[0060] The halide (X) of the phosphoryl halide (POX 3 ) compound used in the present invention is any one selected from chloride (Cl), bromide (Br), and iodide (I), and all of them can be used. The phosphoryl halide (POX 3 ) compound is preferably phosphoryl chloride.

[0061] The compound of Chemical Formula 3 in the present invention is a substance that oxidizes phosphoryl halide (POX 3 ) or phosphoryl fluoride (POF 3 ), has a carbonyl group (C=O), and is not limited as long as it can oxidize phosphoryl halide (POX 3 ) or phosphoryl fluoride (POF 3 ). Preferably, formaldehyde, formic acid, acetic acid, methyl acetate, ethyl acetate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, dimethylformamide, methylphenylformamide, acetamide, dimethylacetamide, cyanuric acid, and cyanuric chloride can be mentioned.

[0062] In the present invention, the lithium salt is a substance that generates a lithium salt of dihalophosphoric acid or a lithium salt of difluorophosphoric acid, and is one or more selected from the group consisting of lithium acetate, lithium azide, lithium bicarbonate, lithium bisulfate, lithium carbonate, lithium fluoride, lithium chloride, lithium bromide, lithium iodide, lithium cyanide, lithium dodecaborate, lithium hydride, lithium hydroxide, lithium nitrate, lithium oxalate, lithium oxide, lithium perchlorate, lithium sulfate, lithium sulfide or lithium amide, and mixtures thereof. The lithium salt is preferably lithium carbonate and / or lithium chloride.

[0063] In the present invention, MF of Chemical Formula 5 n The compound is a fluorinating agent that substitutes the halogen of phosphoryl halide (POX 3 ) or dihalophosphate with F, M is H, Li, Na, K, Ca, Zn, Sb, Rb, Cs or an onium ion, and n is 1 or 2.

[0064] The onium ion is an onium ion containing N or S.

[0065] The onium ion is preferably an ammonium ion.

[0066] The production of lithium difluorophosphate of the present invention may be carried out in a solvent.

[0067] Preferably, the solvent may be one or more selected from toluene, haloalkane-based, nitrile-based, ether-based, alcohol-based, ester-based, and carbonate-based solvents. Specifically, the solvent may include dimethoxyethane, ethyl acetate, butyl acetate, toluene, chloroform, dichloromethane, dichloroethane, tetrahydrofuran, acetonitrile, and the like.

[0068] The production of lithium difluorophosphate of the present invention may be carried out at 30 to 100 °C, and may also be carried out in an inert gas atmosphere of nitrogen or argon. After mixing the reactants, the production of lithium difluorophosphate may preferably be carried out with stirring for 5 to 20 hours.

[0069] For the production of lithium difluorophosphate of the present invention, with respect to 1 equivalent of phosphoryl halide or phosphoryl fluoride, the lithium salt may be reacted in an amount of 1 to 1.5 equivalents. With respect to 1 equivalent of phosphoryl halide or phosphoryl fluoride, the oxidizing agent may be reacted in an amount of 1 to 1.5 equivalents. When the lithium salt and the oxidizing agent are used in the above contents, lithium difluorophosphate can be produced in high yield and high purity. For the production of high-purity lithium difluorophosphate, the present invention can react MF of Chemical Formula 5 in an amount of 2 to 8 equivalents with respect to 1 equivalent of phosphoryl halide. n can be reacted.

[0070] The step of obtaining the product after the step-by-step reaction may be a step of filtering the reaction solution to remove the reaction solvent, or may be a step of partially removing the reaction solvent and adding a poor solvent to the product to obtain crystals.

[0071] The present invention provides 0 to 500 weight ppm of F - 0 to 500 weight ppm of Cl - 0 to 500 weight ppm of SO 4 2―or 0 to 500 ppm by weight of PO 4 3- Provided is a lithium difluorophosphate salt containing

[0072] Conventional lithium difluorophosphate salts are produced using lithium hexafluorophosphate salt and siloxane, and thus contain a large amount of various acidic impurities.

[0073] In contrast, the lithium difluorophosphate salt of the present invention is produced by a production method that does not generate acidic by-products and is produced by a relatively mild method, so that the final product is a lithium difluorophosphate salt with acidic impurities, particularly F - , Cl - , SO 4 2- or PO 4 3- ions may each be contained at 0 to 500 ppm by weight. The lithium difluorophosphate salt of the present invention preferably contains F - , Cl - , SO 4 2- or PO 4 3- ions each at 0 to 200 ppm by weight, more preferably each at 0 to 100 ppm by weight, and even more preferably each at 0 to 50 ppm by weight. The lithium difluorophosphate salt of the present invention preferably has a total content of F - , Cl - , SO 4 2- and PO 4 3- ions of more than 0 to 200 ppm by weight or less, more preferably more than 0 to 150 ppm by weight or less.

[0074] When the lithium difluorophosphate salt with reduced impurities is used in an electrolyte for a lithium secondary battery, it has the advantage of being able to improve electrical characteristics, output, and gas reduction characteristics.

[0075] Embodiment The preferred embodiments of the present invention are described in detail below. However, the present invention is not limited thereto. Hereinafter, ppm is ppm by weight.

Example

[0076] Example 1. Step-by-step LiPO production using formic acid 2 F 2 Production 1. Production of LiPO using formic acid (Formic acid) 2 Cl 2 Production 300 g of dimethoxyethane and 50 g (326 mmol) of phosphoryl chloride were quantitatively charged into a flask equipped with a stirrer, a condenser, and a thermometer under a nitrogen atmosphere, and the internal temperature was cooled to 5°C and stirred. Subsequently, 14.5 g (342 mmol) of lithium chloride was added and stirred at a low temperature. Then, 15.7 g (341 mmol) of formic acid was gradually added dropwise, the temperature was raised to 45°C, and the reaction was carried out for 5 hours. After the reaction was completed, the reaction solution was filtered and the solution was concentrated. 150 g of hexane was added to the crude concentrated solution, the precipitated crystals were filtered, and the filtered solid was dried to obtain 43.6 g (310 mmol) of white powder lithium dichlorophosphate. (Yield 95%)

[0077] 2. Production of LiPO using LiPO 2 Cl 2 for the production of LiPO 2 F 2 Production 300 g of dimethoxyethane and 43.6 g (310 mmol) of lithium dichlorophosphate were charged into a flask equipped with a stirrer, a condenser and a thermometer under a nitrogen atmosphere, and stirred at room temperature. Subsequently, 45.8 g (1,237 mmol) of ammonium fluoride was added, and the temperature was gradually raised to 80 °C and additional reaction was carried out for 8 hours. After the reaction was completed, the reaction solution was filtered and the solution was concentrated. 150 g of toluene was added to the concentrated solution in the crude state, the precipitated crystals were filtered, and the filtered solid was dried to obtain 30 g (279 mmol) of lithium difluorophosphate as a white powder. (Yield 90%, purity 99%, impurity anion content: F 18.4 ppm, Cl 4.4 ppm, SO 4 18.4 ppm, PO 4 12.2 ppm)

[0078] Example 2. In-situ LiPO prepared using formic acid 2 F 2 Production 300 g of dimethoxyethane and 50 g (326 mmol) of phosphoryl chloride were quantitatively charged into a flask equipped with a stirrer, a condenser and a thermometer under a nitrogen atmosphere, and the internal temperature was cooled to 5 °C and stirred. Subsequently, 14.5 g (342 mmol) of lithium chloride was added and stirred at low temperature. Then, 15.7 g (341 mmol) of formic acid was gradually added dropwise and the temperature was raised to 45 °C and reacted for 5 hours. After confirming that the generation of bubbles had ended, 45.8 g (1,237 mmol) of ammonium fluoride was added, and the temperature was gradually raised to 80 °C and additional reaction was carried out for 8 hours. After the reaction was completed, the reaction solution was filtered and the solution was concentrated. 150 g of toluene was added to the concentrated solution in the crude state, the precipitated crystals were filtered, and the filtered solid was dried to obtain 30.6 g (284 mmol) of lithium difluorophosphate as a white powder. (Yield 87%, purity 99%, impurity anion content: F 20.3 ppm, Cl 5.2 ppm, SO 4 23.6 ppm, PO 4 15.1 ppm)

[0079] Example 3. Stepwise LiPO prepared using dimethylformamide 2 F2 Manufacturing 1. NH using dimethylformamide 4 PO 2 F 2 Manufacturing 300g of dimethoxyethane, 24g (328mmol) of dimethylformamide, and 48g (1,296mmol) of ammonium fluoride were weighed and added to a flask equipped with a stirrer, condenser, and thermometer under a nitrogen atmosphere, and the internal temperature was raised to 40℃ and stirred. 50g (326mmol) of phosphoryl chloride was then slowly added dropwise, and the temperature was raised to 50℃ and reacted for 18 hours. After the reaction was completed, the reaction solution was cooled to room temperature, filtered, and the solution was concentrated. 150g of hexane was added to the crude concentrate, and the precipitated crystals were filtered. The filtered solid was dried to obtain 36.1g (303mmol) of white powder ammonium difluorophosphate. (Yield 93%)

[0080] 2.NH 4 PO 2 F 2 Using LiPO 2 F 2 Manufacturing 300g of dimethoxyethane, 36.1g (303mmol) of ammonium difluorophosphate, 15.6g (211mmol) of lithium carbonate, and 5.1g (121mmol) of lithium chloride were weighed and charged into a flask equipped with a stirrer, a condenser, and a thermometer under a nitrogen atmosphere, and the mixture was heated to 50°C and reacted for 3 hours. After the reaction was completed, the mixture was cooled to room temperature, filtered, and the solution was concentrated. 150g of toluene was added to the crude concentrate, and the precipitated crystals were filtered. The filtered solid was dried to obtain 29.8g (276mmol) of white powder lithium difluorophosphate. (Yield 91%, purity 98%, impurity anion content: F 21.3ppm, Cl 6.0ppm, SO 4 24.6ppm, PO 4 13.9 ppm)

[0081] Example 4. In situ LiPO using dimethylformamide2 F 2 Production of 300 g of dimethoxyethane, 24 g (328 mmol) of dimethylformamide, and 48 g (1,296 mmol) of ammonium fluoride were quantitatively charged into a flask equipped with a stirrer, a condenser, and a thermometer under a nitrogen atmosphere, and the internal temperature was raised to 40 °C and stirred. Subsequently, 50 g (326 mmol) of phosphoryl chloride was gradually added dropwise, and the temperature was raised to 50 °C and reacted for 18 hours. When the primary reaction was completed, 15.6 g (211 mmol) of lithium carbonate and 5.1 g (121 mmol) of lithium chloride were quantitatively charged and stirred while maintaining the temperature at 50 °C for 3 hours. When the secondary reaction was completed, after cooling to room temperature, the reaction solution was filtered and the solution was concentrated. 150 g of hexane was added to the crude concentrate, the precipitated crystals were filtered, and the filtered solid was dried to obtain 29.9 g (277 mmol) of lithium difluorophosphate as a white powder. (Yield 85%, purity 99%, impurity anion content: F 24.7 ppm, Cl 6.1 ppm, SO 4 28.4 ppm, PO 4 14.3 ppm)

[0082] Example 5. Step-by-step LiPO using acetamide 2 F 2 Production of 1. Production of NH 4 PO 2 F 2 using acetamide 300 g of dimethoxyethane, 19.4 g (328 mmol) of acetamide, and 48 g (1,296 mmol) of ammonium fluoride were quantitatively added to a flask equipped with a stirrer, a condenser, and a thermometer under a nitrogen atmosphere, and the internal temperature was raised to 40 °C and stirred. Subsequently, 50 g (326 mmol) of phosphoryl chloride was gradually added dropwise, and the temperature was raised to 50 °C and reacted for 18 hours. After the reaction was completed, it was cooled to room temperature, and then the reaction solution was filtered and the solution was concentrated. 150 g of hexane was added to the concentrated solution in the crude state, and the precipitated crystals were filtered, and the filtered solid was dried to obtain 35.3 g (297 mmol) of ammonium difluorophosphate as a white powder. (Yield 91%)

[0083] 2.NH 4 PO 2 F 2 The production of LiPO 2 F 2 using 300 g of dimethoxyethane, 35.3 g (297 mmol) of ammonium difluorophosphate, 15.6 g (211 mmol) of lithium carbonate, and 5.1 g (121 mmol) of lithium chloride were quantitatively added to a flask equipped with a stirrer, a condenser, and a thermometer under a nitrogen atmosphere, and the temperature was raised to 50 °C and reacted for 3 hours. After the reaction was completed, it was cooled to room temperature, and then the reaction solution was filtered and the solution was concentrated. 150 g of toluene was added to the concentrated solution in the crude state, and the precipitated crystals were filtered, and the filtered solid was dried to obtain 28.8 g (267 mmol) of lithium difluorophosphate as a white powder. (Yield 90%, purity 98%, impurity anion content: F 27.4 ppm, Cl 6.9 ppm, SO 4 29.1 ppm, PO 4 15.5 ppm)

[0084] Example 6. In-situ production of LiPO 2 F 2 using acetamide 300 g of dimethoxyethane, 19.4 g (328 mmol) of acetamide, and 48 g (1,296 mmol) of ammonium fluoride were quantitatively added to a flask equipped with a stirrer, a condenser, and a thermometer under a nitrogen atmosphere, and the internal temperature was raised to 40 °C and stirred. Subsequently, 50 g (326 mmol) of phosphoryl chloride was gradually added dropwise, and the temperature was raised to 50 °C and reacted for 18 hours. When the primary reaction was completed, 15.6 g (211 mmol) of lithium carbonate and 5.1 g (121 mmol) of lithium chloride were quantitatively added and stirred while maintaining the temperature at 50 °C for 3 hours. When the secondary reaction was completed, after cooling to room temperature, the reaction solution was filtered and the solution was concentrated. 150 g of hexane was added to the crude concentrated solution, the precipitated crystals were filtered, and the filtered solid was dried to obtain 28.8 g (267 mmol) of white powder lithium difluorophosphate. (Yield 82%, purity 97%, impurity anion content: F 32.4 ppm, Cl 7.4 ppm, SO 4 35.6 ppm, PO 4 16.8 ppm)

[0085] Example 7. Step-by-step LiPO 2 F 2 production 1. Production of NH 4 PO 2 F 2 using dimethylacetamide 300 g of dimethoxyethane, 28.6 g (328 mmol) of dimethylacetamide, and 48 g (1,296 mmol) of ammonium fluoride were quantitatively added to a flask equipped with a stirrer, a condenser, and a thermometer under a nitrogen atmosphere, and the internal temperature was raised to 40 °C and stirred. Subsequently, 50 g (326 mmol) of phosphoryl chloride was gradually added dropwise, and the temperature was raised to 50 °C and reacted for 18 hours. After the reaction was completed, after cooling to room temperature, the reaction solution was filtered and the solution was concentrated. 150 g of hexane was added to the crude concentrated solution, the precipitated crystals were filtered, and the filtered solid was dried to obtain 33.7 g (283 mmol) of white powder ammonium difluorophosphate. (Yield 87%)

[0086] 2.NH 4 PO 2 F 2 Utilization of LiPO 2 F 2 Production 300 g of dimethoxyethane, 33.7 g (283 mmol) of ammonium difluorophosphate, 15.6 g (211 mmol) of lithium carbonate, and 5.1 g (121 mmol) of lithium chloride were quantitatively charged into a flask equipped with a stirrer, a condenser, and a thermometer under a nitrogen atmosphere, heated to 50 °C, and reacted for 3 hours. After the reaction was completed, it was cooled to room temperature, and then the reaction solution was filtered and the solution was concentrated. 150 g of toluene was added to the crude concentrated solution, the precipitated crystals were filtered, and the filtered solid was dried to obtain 27.5 g (254 mmol) of white powder lithium difluorophosphate. (Yield 92%, purity 97%, impurity anion content: F 35.3 ppm, Cl 7.6 ppm, SO 4 34.8 ppm, PO 4 21.1 ppm)

[0087] Example 8. In-situ LiPO 2 F 2 Production 300 g of dimethoxyethane, 28.6 g (328 mmol) of dimethylacetamide, and 48 g (1,296 mmol) of ammonium fluoride were quantitatively charged into a flask equipped with a stirrer, a condenser, and a thermometer under a nitrogen atmosphere, and the internal temperature was raised to 40 °C and stirred. Subsequently, 50 g (326 mmol) of phosphoryl chloride was gradually added dropwise, and the temperature was raised to 50 °C and reacted for 18 hours. When the primary reaction was completed, 15.6 g (211 mmol) of lithium carbonate and 5.1 g (121 mmol) of lithium chloride were quantitatively charged and stirred while maintaining the temperature at 50 °C for 3 hours. After the secondary reaction was completed, the reaction mixture was cooled to room temperature, and then the reaction solution was filtered and the solution was concentrated. 150 g of hexane was added to the crude concentrated solution, the precipitated crystals were filtered, and the filtered solid was dried to obtain 28.1 g (260 mmol) of white powder lithium difluorophosphate. (Yield 80%, purity 98%, impurity anion content: F 42.2 ppm, Cl 8.5 ppm, SO 4 41.9 ppm, PO 4 23.3 ppm)

[0088] Example 9. Preparation of LiPO 2 F 2 using phosphoryl fluoride and formic acid 300 g of dimethoxyethane and 50 g (481 mmol) of phosphoryl fluoride were quantitatively charged into a flask equipped with a stirrer, a condenser, and a thermometer under a nitrogen atmosphere, and the internal temperature was cooled to 5 °C and stirred. Subsequently, 13.1 g (505 mmol) of lithium fluoride was added and stirred at low temperature. Then, 23.2 g (505 mmol) of formic acid was gradually added dropwise, and the temperature was raised to 45 °C and reacted for 5 hours. After the reaction was completed, the reaction solution was filtered and the solution was concentrated. 150 g of hexane was added to the crude concentrated solution, the precipitated crystals were filtered, and the filtered solid was dried to obtain 46.7 g (433 mmol) of white powder lithium difluorophosphate. (Yield 90%, purity 99%, impurity anion content: F 16.2 ppm, Cl 2.1 ppm, SO 4 13.3 ppm, PO 4 10.5 ppm)

[0089]

Table 1

Industrial Applicability

[0090] The present invention relates to a method for producing lithium difluorophosphate salt with high purity and high yield without using lithium hexafluorophosphate salt. According to the present invention, lithium difluorophosphate salt can be produced economically. Further, the present invention provides a high-purity lithium difluorophosphate salt with reduced impurities. When this is used in an electrolyte for a lithium secondary battery, it can improve electrochemical characteristics, provide high output, and reduce gas generation, etc.

Claims

1. Step 1) Reacting a phosphoryl halide (POX ３ ) compound of the following chemical formula 2, an oxidizing agent of the following chemical formula 3, and a lithium salt to produce a lithium dihalophosphate salt of the following chemical formula 4; and Step 2) reacting the lithium dihalophosphate salt of Chemical Formula 4 with the fluoride salt of Chemical Formula 5 below to produce the lithium difluorophosphate salt of Chemical Formula 1 below; comprising A method for producing a lithium difluorophosphate salt: [Chemical Formula 2] 【Chemical 1】 [Chemical Formula 3] [Chemical Formula 2] [Chemical Formula 4] [Chemical Formula 3] [Chemical Formula 5] MF ｎ [Chemical Formula 1] 【Chemical 4】 In the above chemical formulas X is Cl, Br or I; R1 and R2 are each independently H, a C1-10 alkyl group, a phenyl group, OH, OR3, NH ２ , NHR4, NR5R6, NaO, KO or ONH ４ and R3, R4, R5 and R6 are each independently a C1-10 alkyl group or a phenyl group; R1 and R2 together can form a ring having 2 to 5 carbon atoms that can contain one or more hetero elements of O or N; M is H, Li, Na, K, Ca, Zn, Sb, Rb, Cs or an onium ion; n is 1 or 2.

2. Step 1') Reacting a phosphoryl halide (POX ３ ) compound of the following chemical formula 2, an oxidizing agent of the following chemical formula 3, and a fluoride salt of the following chemical formula 5 to produce a difluorophosphate of the following chemical formula 6; and Step 2') reacting the difluorophosphate salt of Chemical Formula 6 with a lithium salt to produce the lithium difluorophosphate salt of Chemical Formula 1 below; A method for producing a lithium difluorophosphate salt, comprising: [Chemical Formula 2] 【Chemical Formula 5】 [Chemical Formula 3] 【Chemical Formula 6】 [Chemical Formula 5] MF ｎ [Chemical Formula 6] 【Chemical Formula 7】 [Chemical Formula 1] 【Chemical 8】 In the above chemical formulas X is Cl, Br or I; R1 and R2 are each independently H, a C1-10 alkyl group, a phenyl group, OH, OR3, NH ２ , NHR4, NR5R6, NaO, KO or ONH ４ and R3, R4, R5, and R6 are each independently a C1-10 alkyl group or a phenyl group; R1 and R2 together can form a ring having 2 to 5 carbon atoms that can contain one or more hetero elements of O or N; M is H, Li, Na, K, Ca, Zn, Sb, Rb, Cs or an onium ion; n is 1 or 2.

3. Phosphoryl fluoride (POF) of the following chemical formula 7 ３ ), a compound, an oxidizing agent of the following chemical formula 3, and a lithium salt are reacted to produce a lithium difluorophosphate salt of the following chemical formula 1, a method for producing a lithium difluorophosphate salt: [Chemical Formula 7] 【Chemical Formula 9】 [Chemical Formula 3] 【Chemical Formula 10】 [Chemical Formula 1] 【Chemical 11】 In the above chemical formulas R1 and R2 are each independently H, a C1-10 alkyl group, a phenyl group, OH, OR3, NH ２ , NHR4, NR5R6, ONa, OK or ONH ４ and R3, R4, R5 and R6 are each independently a C1-10 alkyl group or a phenyl group; R1 and R2 together can form a ring having 2 to 5 carbon atoms that can contain one or more hetero elements of O or N.

4. The oxidizing agent of Chemical Formula 3 is one or more selected from the group consisting of formaldehyde, formic acid, acetic acid, methyl acetate, ethyl acetate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, dimethylformamide, methylphenylformamide, acetamide, dimethylacetamide, cyanuric acid, and cyanuric chloride. The method for producing a lithium difluorophosphate salt according to Claim 1, 2 or 3, characterized in that.

5. The lithium salt is one or more selected from the group consisting of lithium acetate, lithium azide, lithium bicarbonate, lithium bisulfate, lithium carbonate, lithium fluoride, lithium chloride, lithium bromide, lithium iodide, lithium cyanide, lithium dodecaborate, lithium hydride, lithium hydroxide, lithium nitrate, lithium oxalate, lithium oxide, lithium perchlorate, lithium sulfate, lithium sulfide, or lithium amide, and mixtures thereof. The method for producing a lithium difluorophosphate salt according to claim 1, 2, or 3, characterized in that it is such.

6. The method for producing lithium difluorophosphate according to claim 1, 2, or 3, characterized in that the production of lithium difluorophosphate is carried out in a solvent.

7. The method for producing a lithium difluorophosphate salt according to claim 6, characterized in that the solvent is one or more selected from the group consisting of toluene, haloalkane-based, nitrile-based, ether-based, alcohol-based, ester-based, and carbonate-based.

8. The method for producing a lithium difluorophosphate salt according to claim 1 or 2, characterized in that 1 to 1.5 equivalents of the lithium salt are reacted with 1 equivalent of phosphoryl halide.

9. The method for producing a lithium difluorophosphate salt according to claim 3, characterized in that 1 to 1.5 equivalents of the lithium salt are reacted with 1 equivalent of phosphoryl fluoride.

10. The method for producing lithium difluorophosphate according to claim 1 or 2, characterized in that 1 to 1.5 equivalents of an oxidizing agent are reacted with 1 equivalent of phosphoryl halide.

11. The method for producing lithium difluorophosphate according to claim 3, characterized in that 1 to 1.5 equivalents of an oxidizing agent are reacted with 1 equivalent of phosphoryl fluoride.

12. React 2 to 8 equivalents of MF with 1 equivalent of phosphoryl halide. ｎ The method for producing a lithium difluorophosphate salt according to claim 1 or 2, characterized by the above.

13. Lithium difluorophosphate salt containing 0 to 500 ppm by weight of F － 、0 to 500 ppm by weight of Cl － 、0 to 500 ppm by weight of SO ４ ２― or 0 to 500 ppm by weight of PO ４ ３－ 。

14. F － , Cl － , SO ４ ２－ and PO ４ ３－ The lithium difluorophosphate salt according to claim 13, wherein the total sum of the contents of F － , Cl － , SO ４ ２－ and PO ４ ３－ ions exceeds 0 and is 200 ppm by weight or less.

Images