Method for producing lithium difluorophosphate salt for lithium secondary batteries
A novel method for producing lithium difluorophosphate salts using phosphoryl halides and oxidizing agents addresses the issues of toxic byproducts and high costs in conventional methods, achieving high-purity and high-yield production suitable for lithium secondary battery electrolytes.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Patents
- Current Assignee / Owner
- EP CHEMTECH CO LTD
- Filing Date
- 2023-05-26
- Publication Date
- 2026-05-27
AI Technical Summary
Conventional methods for producing lithium difluorophosphate salts using lithium hexafluorophosphate and siloxane result in the generation of toxic fluorinated silane gas and high production costs, with significant impurity levels and yield loss due to the use of expensive raw materials and subsequent purification challenges.
A novel method involving the reaction of phosphoryl halide compounds with an oxidizing agent and a fluoride salt to produce lithium difluorophosphate, avoiding the use of lithium hexafluorophosphate and siloxane, thereby eliminating toxic byproducts and reducing production costs.
The method achieves high-purity lithium difluorophosphate with reduced impurities, improving electrochemical properties and output when used in electrolytes for lithium secondary batteries, while being environmentally friendly and economically viable.
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Abstract
Description
[Technical Field]
[0001] This invention relates to a method for producing lithium difluorophosphate salts in high yield using low-cost raw materials. Furthermore, this invention relates to lithium difluorophosphate salts with reduced impurities. In particular, it relates to a method for producing lithium difluorophosphate salts in high purity and high yield without using lithium hexafluoride phosphate, and to the high-purity lithium difluorophosphate salts produced therefrom. The lithium difluorophosphate salts produced by this invention can be used in electrolytes for lithium secondary batteries, and when used in such electrolytes, they provide effects such as improved electrochemical properties, higher output, and reduced gas emissions. [Background technology]
[0002] Lithium-ion batteries are widely used in small, advanced electronic devices such as mobile devices and notebook / pancomputers. With the spread of electric vehicles (EVs), development is also underway on medium and large lithium-ion batteries that are electrochemically stable while maintaining high capacity.
[0003] With the increasing demand for medium and large lithium secondary batteries, the need for high-performance lithium secondary batteries has grown, requiring secondary batteries with high output, high energy density, gas reduction effects, and improved lifespan. Therefore, there is a demand for the development of electrolytes suitable for such secondary batteries, and multi-functional additives to improve electrolyte function have begun to attract attention. In particular, lithium difluorophosphate salts have been found to be useful in improving electrolyte function. Due to these market influences, there is a pressing need for the development of high-purity lithium difluorophosphate salts that can improve battery life while maintaining low manufacturing costs. [Overview of the Initiative] [Problems that the invention aims to solve]
[0004] A widely known conventional method for producing lithium difluorophosphate salts involves the use of LiPF6, and the reaction is illustrated in the following reaction equation 1. [Reaction Equation 1] [ka]
[0005] The aforementioned reaction is a method for producing lithium difluorophosphate using lithium hexafluoride phosphate (LiPF6) and various forms of siloxane, and is characterized by the fact that it does not use water. However, this method has the disadvantage of generating fluorinated silane (SiF2(CH3)2) gas, a toxic substance, as a byproduct, and a large amount of acidic byproduct remains in the product, lithium difluorophosphate. Furthermore, this method has the disadvantage of high production costs because it uses expensive raw materials such as lithium hexafluoride phosphate (LiPF6), which is also used as an electrolyte in lithium secondary batteries along with siloxane (-Si(CH3)2O-). Therefore, there is an urgent need for a new method for producing lithium difluorophosphate that is more economical than conventional methods, does not produce toxic byproducts, and is environmentally friendly.
[0006] Therefore, the object of the present invention is to provide a novel manufacturing method for lithium difluorophosphate that does not use expensive siloxanes and lithium hexafluoride phosphate (LiPF6), and does not generate toxic fluorinated silane gas, in an environmentally friendly and economical manner.
[0007] Another object of the present invention is to provide a high-purity lithium difluorophosphate salt. [Means for solving the problem]
[0008] To solve the aforementioned problems, the present invention provides Step 1) A step of reacting a phosphoryl halide (POX3) compound of chemical formula 2 below, an oxidizing agent of chemical formula 3 below, and a lithium salt to produce a lithium dihalophosphate salt of chemical formula 4 below; 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 (LiPO2X2) of Chemical Formula 1 below; A method for producing a lithium difluorophosphate salt is provided, which includes this step.
[0009] [Chemical Formula 2] [Chem.]
[0010] [Chemical Formula 3] [Chem.]
[0011] [Chemical Formula 4] [Chem.]
[0012] [Chemical Formula 5] MF , ,
[0014] , , <0000
[0015] The present invention also Step 1') The step of reacting a phosphoryl halide (POX3) compound of chemical formula 2 below, an oxidizing agent of chemical formula 3 below, and a fluoride salt of chemical formula 5 below to produce a difluorophosphate (MPO2F2) of chemical formula 6 below; and The present invention provides a method for producing lithium difluorophosphate (LiPO2F2), comprising the step 2') reacting a difluorophosphate of chemical formula 6 with a lithium salt to produce a lithium difluorophosphate of chemical formula 1 below;
[0016] [Chemical formula 2] [ka]
[0017] [Chemical formula 3] [ka]
[0018] [Chemical formula 5] MF n
[0019] [Chemical formula 6] [ka]
[0020] [Chemical formula 1] [ka]
[0021] In the above chemical formula X is Cl, Br, or I. R1 and R2 are independently H, a C1-10 alkyl group, a phenyl group, OH, OR3, NH2, NHR4, NR5R6, ONa, OK, or ONH4. R3, R4, R5, and R6 are each independently a C1-10 alkyl group or phenyl group. Both R1 and R2 can form rings with 2 to 5 carbon atoms, each containing one or more heterogeneous elements such as O or N. M is H, Li, Na, K, Ca, Zn, Sb, Rb, Cs, or onium ions. n is either 1 or 2.
[0022] The present invention also This invention provides a method for producing lithium difluorophosphate salt (LiPO2F2) of the following chemical formula 1 by reacting a phosphoryl fluoride (POF3) 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] [ka]
[0024] [Chemical formula 3] [ka]
[0025] [Chemical formula 1] [ka]
[0026] In the above chemical formula R1 and R2 are independently H, a C1-10 alkyl group, a phenyl group, OH, OR3, NH2, NHR4, NR5R6, ONa, OK, or ONH4. R3, R4, R5, and R6 are each independently a C1-10 alkyl group or phenyl group. Both R1 and R2 can form rings with 2 to 5 carbon atoms, each containing one or more heterogeneous elements, such as O or N.
[0027] This invention also provides F at 0-500 ppm by weight. - , 0-500 ppm by weight of Cl - , SO4 0-500 ppm by weight 2― Or PO4 at 0-500 ppm by weight 3- The present invention provides lithium difluorophosphate salts containing the above. [Effects of the Invention]
[0028] The manufacturing method according to the present invention has the advantage of being economically efficient because it does not use expensive lithium hexafluoride phosphate (LiPF6) and siloxane. Furthermore, the manufacturing method according to the present invention is environmentally friendly as it does not generate toxic fluorinated silane gas, and it has the effect of producing lithium difluorophosphate with a high purity of 97% or more and a high yield of 80% or more using a relatively simple manufacturing method. The lithium difluorophosphate of the present invention has the advantage of having extremely low levels of metal ion impurities and acidic ions such as hydrofluoric acid, hydrochloric acid, sulfuric acid, and phosphoric acid, and when used in electrolytes for lithium secondary batteries, it can improve electrical characteristics, output, and gas reduction characteristics. [Modes for carrying out the invention]
[0029] The present invention will be described in more detail below. Terms and words used in this specification and claims should not be interpreted to be limited to their ordinary or dictionary meanings, but rather to be interpreted in a way that is consistent with the technical idea of the present invention, in accordance with the principle that inventors may appropriately define the concepts of terms in order to best describe their invention.
[0030] Conventional methods for commercially producing lithium difluorophosphate (LiPO2F2) involve using lithium hexafluoride phosphate (LiPF6). Most processes using lithium hexafluoride phosphate (LiPF6) generate toxic gases such as hydrofluoric acid or fluorinated silane, making the construction of separate purification facilities essential. Furthermore, it is difficult to completely remove hydrofluoric acid and fluorinated silane, which are byproducts in the production method using lithium difluorophosphate (LiPO2F2). Moreover, when electrolytes are produced, stored, and distributed using lithium difluorophosphate containing such impurities, a secondary problem arises: over time, side reactions occur, generating even more impurities and reducing purity. One of these byproducts is hydrofluoric acid, which, when dissolved in the electrolyte and injected into batteries, can cause problems such as oxidation of the battery electrodes and the metal battery packaging.
[0031] Furthermore, lithium hexafluoride phosphate (LiPF6) is an essential and widely used material in lithium secondary battery electrolytes, and as the demand for lithium secondary batteries increases, its cost rises. Therefore, in order to produce lithium difluorophosphate (LiPO2F2) at a competitive price and with high purity, the development of manufacturing technologies that do not use lithium hexafluoride phosphate (LiPF6) is urgently needed.
[0032] Therefore, in the process of striving to develop a novel manufacturing method that is environmentally friendly and economical, does not use expensive siloxanes and lithium hexafluoride phosphate (LiPF6), and does not generate toxic fluorinated silane gas, the inventors developed a method using phosphoryl halide (POX3) compounds, which can be easily purchased at low cost as starting materials, and thus completed the present invention. In other words, the present invention allows for the easy production of phosphoryl halides using an oxidizing agent containing a carbonyl group (C=O), and enables the production of lithium difluorophosphate in a simple, economical, environmentally friendly manner with high purity and high yield.
[0033] This invention Step 1) A step of reacting a phosphoryl halide compound of chemical formula 2 below, an oxidizing agent of chemical formula 3 below, and a lithium salt to produce a lithium dihalophosphate salt of chemical formula 4 below; and The present invention provides a method for producing lithium difluorophosphate, comprising step 2) reacting a lithium dihalophosphate salt of chemical formula 4 with a fluoride salt of chemical formula 5 to produce a lithium difluorophosphate salt of chemical formula 1.
[0034] [Chemical formula 2] [ka]
[0035] [Chemical formula 3] [ka]
[0036] [Chemical formula 4] [ka]
[0037] [Chemical formula 5] MF n
[0038] [Chemical formula 1] [ka]
[0039] In the above chemical formula X is Cl, Br, or I. R1 and R2 are independently H, a C1-10 alkyl group, a phenyl group, OH, OR3, NH2, NHR4, NR5R6, ONa, OK, or ONH4. R3, R4, R5, and R6 are each independently a C1-10 alkyl group or phenyl group. Both R1 and R2 can form rings with 2 to 5 carbon atoms, each containing one or more heterogeneous elements such as O or N. M is H, Li, Na, K, Ca, Zn, Sb, Rb, Cs, or onium ions. n is either 1 or 2.
[0040] The method of the present invention can be illustrated with a reaction equation as shown in Reaction Equation 2. [Reaction Equation 2] [ka]
[0041] The present invention also Step 1') The step of reacting a phosphoryl halide (POX3) compound of chemical formula 2 below, an oxidizing agent of chemical formula 3 below, and a fluoride salt of chemical formula 5 below to produce a difluorophosphate of chemical formula 6 below; and The present invention provides a method for producing lithium difluorophosphate, comprising step 2') reacting a difluorophosphate of chemical formula 6 with a lithium salt to produce a lithium difluorophosphate of chemical formula 1 below.
[0042] [Chemical formula 2] [ka]
[0043] [Chemical formula 3] [ka]
[0044] [Chemical formula 5] MF n
[0045] [Chemical formula 6] [ka]
[0046] [Chemical formula 1] [ka]
[0047] In the above chemical formula X is Cl, Br, or I. R1 and R2 are independently H, a C1-10 alkyl group, a phenyl group, OH, OR3, NH2, NHR4, NR5R6, ONa, OK, or ONH4. R3, R4, R5, and R6 are each independently a C1-10 alkyl group or phenyl group. Both R1 and R2 can form rings with 2 to 5 carbon atoms, each containing one or more heterogeneous elements such as O or N. M is H, Li, Na, K, Ca, Zn, Sb, Rb, Cs, or onium ions. n is either 1 or 2.
[0048] The method of the present invention described above can be illustrated with the following reaction equation 3. [Reaction Equation 3] [ka]
[0049] The present invention also This invention provides a method for producing a lithium difluorophosphate salt of the following chemical formula 1 by reacting a phosphoryl fluoride (POF3) compound of the following chemical formula 7, an oxidizing agent of the following chemical formula 3, and a lithium salt.
[0050] [Chemical formula 7] [ka]
[0051] [Chemical formula 3] [ka]
[0052] [Chemical formula 1] [ka]
[0053] In the above chemical formula R1 and R2 are independently H, a C1-10 alkyl group, a phenyl group, OH, OR3, NH2, NHR4, NR5R6, ONa, OK, or ONH4. R3, R4, R5, and R6 are each independently a C1-10 alkyl group or phenyl group. Both R1 and R2 can form rings with 2 to 5 carbon atoms, each containing one or more heterogeneous elements, such as O or N.
[0054] The method of the present invention described above can be illustrated with a reaction equation as shown in reaction equation 4. [Reaction Equation 4] [ka]
[0055] This invention produces lithium difluorophosphate (LiPO2F2) using phosphoryl halide (POX3) instead of lithium hexafluoride phosphate (LiPF6), thereby suppressing the generation of hydrofluoric acid or fluorinated silane and preventing side reactions.
[0056] Conventionally, the method of producing lithium difluorophosphate by oxidizing lithium hexafluoride phosphate (LiPF6) typically involves using expensive siloxane as the oxidizing agent. This method has the disadvantage of requiring expensive reactants and generating hydrofluoric acid and fluorinated silane as byproducts that remain in the lithium difluorophosphate. Finally, the process of removing these residual byproducts, hydrofluoric acid and fluorinated silane, results in significant yield loss. Furthermore, a separate purification process is required to remove unreacted siloxane. In other words, conventional methods for producing lithium difluorophosphate have problems in terms of economics and the generation of toxic byproducts and the associated purification costs, whereas the present invention has the advantage of not having these problems.
[0057] The present invention has the advantage of being able to stably produce high-purity lithium difluorophosphate without generating fluorinated silane byproducts or side reactions, by using phosphoryl halide instead of lithium hexafluoride phosphate and using a compound having a carbonyl group (C=O) as an oxidizing agent.
[0058] In reaction formula 2, the steps of reacting a phosphoryl halide (POX3) compound with an oxidizing agent, a compound having a carbonyl group (C=O), and a lithium salt, and reacting the product of the above step, lithium dihalophosphate, with a fluoride salt, may be carried out in a situ reaction, or they may be carried out by recovering the intermediate product, lithium dihalophosphate, and then reacting it with a fluoride salt.
[0059] In reaction formula 3, the steps of reacting a phosphoryl halide (POX3) compound with an oxidizing agent, a compound having a carbonyl group (C=O), and a fluoride salt, and reacting the product of the above step, difluorophosphate, with a lithium salt, may be carried out in a situ reaction, or they may be carried out by recovering the intermediate product, difluorophosphate, and then reacting it with the lithium salt.
[0060] The phosphoryl halide (X) in the phosphoryl halide (POX3) compound used in this invention can be any one of chloride (Cl), bromide (Br), and iodide (I), and any of these can be used. The phosphoryl halide (POX3) compound is preferably a phosphoryl chloride.
[0061] In the present invention, the compound of chemical formula 3 is a substance that oxidizes phosphoryl halide (POX3) or phosphoryl fluoride (POF3), and is not limited as long as it has a carbonyl group (C=O) and can oxidize phosphoryl halide (POX3) or phosphoryl fluoride (POF3). Preferably, examples include 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.
[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, the MF of Chemical Formula 5 n compound is a fluorinating agent that substitutes the halogen of phosphoryl halide (POX3) 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 according to the present invention may be carried out under solvent conditions.
[0067] The solvent may preferably be one or more selected from toluene, haloalkane, nitrile, ether, alcohol, ester, and carbonate solvents. Specific examples of the solvent include dimethoxyethane, ethyl acetate, butyl acetate, toluene, chloroform, dichloromethane, dichloroethane, tetrahydrofuran, and acetonitrile.
[0068] The production of lithium difluorophosphate according to the present invention may be carried out at 30 to 100°C and under an inert gas atmosphere of nitrogen or argon. The production of lithium difluorophosphate may be carried out by stirring for 5 to 20 hours after mixing the reactants.
[0069] For the production of lithium difluorophosphate according to the present invention, a lithium salt may be reacted in an amount of 1 to 1.5 equivalents per equivalent of phosphoryl halide or phosphoryl fluoride. An oxidizing agent may be reacted in an amount of 1 to 1.5 equivalents per equivalent of the phosphoryl halide or phosphoryl fluoride. When the lithium salt and oxidizing agent are used in the above proportions, lithium difluorophosphate can be produced in high yield and high purity. For the production of high-purity lithium difluorophosphate according to the present invention, a lithium salt of chemical formula 5 is reacted in an amount of 1 to 1.5 equivalents per equivalent of phosphoryl halide. n It is possible to react 2 to 8 equivalents of this substance.
[0070] The step of obtaining the product after the aforementioned step-by-step reactions may be a step of filtering the reaction solution to remove the reaction solvent, or a step of partially removing the reaction solvent and adding a poor solvent to the product to obtain it as crystals.
[0071] This invention relates to F at 0-500 ppm by weight. - , 0-500 ppm by weight of Cl - , SO4 0-500 ppm by weight 2― Or PO4 at 0-500 ppm by weight3- The present invention provides lithium difluorophosphate salts containing the present invention.
[0072] Conventional lithium difluorophosphate salts are manufactured using lithium hexafluoride phosphate and siloxane, resulting in the presence of a large amount of various acidic impurities.
[0073] In contrast, the lithium difluorophosphate salt of the present invention is manufactured using a relatively mild method that does not generate acidic byproducts, so that the final product is lithium difluorophosphate salt free from acidic impurities, especially F - Cl - SO4 2- or PO4 3- The ions may be present in concentrations of 0 to 500 ppm by weight. The lithium difluorophosphate salt of the present invention is preferably F - Cl - SO4 2- or PO4 3- Each ion contains 0 to 200 ppm by weight, more preferably 0 to 100 ppm by weight, and even more preferably 0 to 50 ppm by weight. The lithium difluorophosphate salt of the present invention preferably contains F - Cl - SO4 2- and PO4 3- The total ion content is characterized by being greater than 0 to 200 ppm by weight or less, more preferably greater than 0 to 150 ppm by weight or less.
[0074] When the aforementioned lithium difluorophosphate salt with reduced impurities is used as an electrolyte for lithium secondary batteries, it has the advantage of improving electrical characteristics, output, and gas reduction characteristics.
[0075] Embodiment Preferred embodiments of the present invention will be described in detail below. However, the present invention is not limited thereto. Hereinafter, ppm refers to ppm by weight. [Examples]
[0076] Example 1. Stepwise production of LiPO2F2 using formic acid 1. Production of LiPO2Cl2 using formic acid In a flask equipped with a stirrer, condenser, and thermometer, 300 g of dimethoxyethane and 50 g (326 mmol) of phosphoryl chloride were added under a nitrogen atmosphere, and the mixture was cooled to 5°C and stirred. Subsequently, 14.5 g (342 mmol) of lithium chloride was added, and the mixture was stirred at a low temperature. Then, 15.7 g (341 mmol) of formic acid was gradually added dropwise, and the temperature was raised to 45°C, where the reaction was carried out for 5 hours. After the reaction was complete, the reaction mixture 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 43.6 g (310 mmol) of white powdered lithium dichlorophosphate. (Yield 95%)
[0077] 2. Manufacturing of LiPO2F2 using LiPO2Cl2 In a flask equipped with a stirrer, condenser, and thermometer, 300 g of dimethoxyethane and 43.6 g (310 mmol) of lithium dichlorophosphate were added 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 slowly raised to 80°C for an additional 8 hours of reaction. After the reaction was complete, the reaction mixture was filtered and the solution was concentrated. 150 g of toluene was added to the crude concentrate, the precipitated crystals were filtered, and the filtered solid was dried to obtain 30 g (279 mmol) of white powdered lithium difluorophosphate. (Yield 90%, purity 99%, impurity anion content: F 18.4 ppm, Cl 4.4 ppm, SO4 18.4 ppm, PO4 12.2 ppm)
[0078] Example 2. In situ production of LiPO2F2 using formic acid. In a flask equipped with a stirrer, condenser, and thermometer, 300 g of dimethoxyethane and 50 g (326 mmol) of phosphoryl chloride were quantitatively added under a nitrogen atmosphere, and the mixture was cooled to 5°C and stirred. Subsequently, 14.5 g (342 mmol) of lithium chloride was added and the mixture was stirred at a low temperature. Then, 15.7 g (341 mmol) of formic acid was gradually added dropwise, and the temperature was raised to 45°C and the reaction was carried out for 5 hours. After confirming that the formation of bubbles had stopped, 45.8 g (1,237 mmol) of ammonium fluoride was added, and the temperature was slowly raised to 80°C and the reaction was carried out for an additional 8 hours. After the reaction was complete, the reaction mixture was filtered and the solution was concentrated. 150 g of toluene was added to the crude concentrate, the precipitated crystals were filtered, and the filtered solid was dried to obtain 30.6 g (284 mmol) of white powdered lithium difluorophosphate. (Yield 87%, purity 99%, impurity anion content: F 20.3 ppm, Cl 5.2 ppm, SO4 23.6 ppm, PO4 15.1 ppm)
[0079] Example 3. Stepwise production of LiPO2F2 using dimethylformamide 1. Production of NH4PO2F2 using dimethylformamide In a flask equipped with a stirrer, condenser, and thermometer, 300 g of dimethoxyethane, 24 g (328 mmol) of dimethylformamide, and 48 g (1,296 mmol) of ammonium fluoride were quantitatively added under a nitrogen atmosphere. The internal temperature was raised to 40°C and the mixture was stirred. Subsequently, 50 g (326 mmol) of phosphoryl chloride was gradually added dropwise, and the mixture was reacted for 18 hours at a temperature of 50°C. After the reaction was complete, the mixture was cooled to room temperature, 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 36.1 g (303 mmol) of white powdered ammonium difluorophosphate. (Yield 93%)
[0080] 2. Manufacturing of LiPO2F2 using NH4PO2F2 In a flask equipped with a stirrer, condenser, and thermometer, 300 g of dimethoxyethane, 36.1 g (303 mmol) of ammonium difluorophosphate, 15.6 g (211 mmol) of lithium carbonate, and 5.1 g (121 mmol) of lithium chloride were quantitatively added under a nitrogen atmosphere. The mixture was heated to 50°C and reacted for 3 hours. After the reaction was complete, the mixture was cooled to room temperature, filtered, and the solution was concentrated. 150 g of toluene was added to the crude concentrate, the precipitated crystals were filtered, and the filtered solid was dried to obtain 29.8 g (276 mmol) of white powdered lithium difluorophosphate. (Yield 91%, purity 98%, impurity anion content: F 21.3 ppm, Cl 6.0 ppm, SO4 24.6 ppm, PO4 13.9 ppm)
[0081] Example 4. Production of in situ LiPO2F2 using dimethylformamide In a flask equipped with a stirrer, condenser, and thermometer, 300 g of dimethoxyethane, 24 g (328 mmol) of dimethylformamide, and 48 g (1,296 mmol) of ammonium fluoride were added 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 the reaction was carried out for 18 hours. After the first reaction was complete, 15.6 g (211 mmol) of lithium carbonate and 5.1 g (121 mmol) of lithium chloride were added, and the mixture was stirred while maintaining a temperature of 50°C for 3 hours. After the second reaction was complete, the mixture was cooled to room temperature, and the reaction solution was filtered to concentrate it. 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 white powdered lithium difluorophosphate. (Yield 85%, purity 99%, impurity anion content: F 24.7 ppm, Cl 6.1 ppm, SO4 28.4 ppm, PO4 14.3 ppm)
[0082] Example 5. Stepwise production of LiPO2F2 using acetamide 1. Production of NH4PO2F2 using acetamide In a flask equipped with a stirrer, condenser, and thermometer, 300 g of dimethoxyethane, 19.4 g (328 mmol) of acetamide, and 48 g (1,296 mmol) of ammonium fluoride were quantitatively added under a nitrogen atmosphere. The internal temperature was raised to 40°C and the mixture was stirred. Subsequently, 50 g (326 mmol) of phosphoryl chloride was gradually added dropwise, and the mixture was reacted at 50°C for 18 hours. After the reaction was complete, the mixture was cooled to room temperature, filtered, and the solution was concentrated. 150 g of hexane was added to the crude concentrate, and the precipitated crystals were filtered. The filtered solid was dried to obtain 35.3 g (297 mmol) of white powdered ammonium difluorophosphate. (Yield 91%)
[0083] 2. Manufacturing of LiPO2F2 using NH4PO2F2 In a flask equipped with a stirrer, condenser, and thermometer, 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 under a nitrogen atmosphere. The mixture was heated to 50°C and reacted for 3 hours. After the reaction was complete, the mixture was cooled to room temperature, filtered, and the solution was concentrated. 150 g of toluene was added to the crude concentrate, the precipitated crystals were filtered, and the filtered solid was dried to obtain 28.8 g (267 mmol) of white powdered lithium difluorophosphate. (Yield 90%, purity 98%, impurity anion content: F 27.4 ppm, Cl 6.9 ppm, SO4 29.1 ppm, PO4 15.5 ppm)
[0084] Example 6. Production of in situ LiPO2F2 using acetamide In a flask equipped with a stirrer, condenser, and thermometer, 300 g of dimethoxyethane, 19.4 g (328 mmol) of acetamide, and 48 g (1,296 mmol) of ammonium fluoride were quantitatively added 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 the reaction was carried out for 18 hours. After the first reaction was complete, 15.6 g (211 mmol) of lithium carbonate and 5.1 g (121 mmol) of lithium chloride were quantitatively added, and the mixture was stirred while maintaining the temperature at 50°C for 3 hours. After the second reaction was complete, the mixture was cooled to room temperature, and the reaction solution was filtered to concentrate it. 150 g of hexane was added to the crude concentrate, the precipitated crystals were filtered, and the filtered solid was dried to obtain 28.8 g (267 mmol) of white powdered lithium difluorophosphate. (Yield 82%, purity 97%, impurity anion content: F 32.4 ppm, Cl 7.4 ppm, SO4 35.6 ppm, PO4 16.8 ppm)
[0085] Example 7. Stepwise production of LiPO2F2 using dimethylacetamide 1. Production of NH4PO2F2 using dimethylacetamide In a flask equipped with a stirrer, condenser, and thermometer, 300 g of dimethoxyethane, 28.6 g (328 mmol) of dimethylacetamide, and 48 g (1,296 mmol) of ammonium fluoride were quantitatively added under a nitrogen atmosphere. The internal temperature was raised to 40°C and the mixture was stirred. Subsequently, 50 g (326 mmol) of phosphoryl chloride was gradually added dropwise, and the mixture was heated to 50°C and reacted for 18 hours. After the reaction was complete, the mixture was cooled to room temperature, and the reaction solution was filtered to concentrate it. 150 g of hexane was added to the crude concentrate, the precipitated crystals were filtered, and the filtered solid was dried to obtain 33.7 g (283 mmol) of white powdered ammonium difluorophosphate. (Yield 87%)
[0086] 2. Manufacturing of LiPO2F2 using NH4PO2F2 In a flask equipped with a stirrer, condenser, and thermometer, 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 added under a nitrogen atmosphere. The mixture was heated to 50°C and reacted for 3 hours. After the reaction was complete, the mixture was cooled to room temperature, and the reaction solution was filtered to concentrate it. 150 g of toluene was added to the crude concentrate, the precipitated crystals were filtered, and the filtered solid was dried to obtain 27.5 g (254 mmol) of white powdered lithium difluorophosphate. (Yield 92%, purity 97%, impurity anion content: F 35.3 ppm, Cl 7.6 ppm, SO4 34.8 ppm, PO4 21.1 ppm)
[0087] Example 8. Production of in situ LiPO2F2 using dimethylacetamide In a flask equipped with a stirrer, condenser, and thermometer, 300 g of dimethoxyethane, 28.6 g (328 mmol) of dimethylacetamide, and 48 g (1,296 mmol) of ammonium fluoride were added 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 the reaction was carried out for 18 hours. After the first reaction was complete, 15.6 g (211 mmol) of lithium carbonate and 5.1 g (121 mmol) of lithium chloride were added, and the mixture was stirred while maintaining the temperature at 50°C for 3 hours. After the second reaction was complete, the mixture was cooled to room temperature, and the reaction solution was filtered to concentrate it. 150 g of hexane was added to the crude concentrate, the precipitated crystals were filtered, and the filtered solid was dried to obtain 28.1 g (260 mmol) of white powdered lithium difluorophosphate. (Yield 80%, purity 98%, impurity anion content: F 42.2 ppm, Cl 8.5 ppm, SO4 41.9 ppm, PO4 23.3 ppm)
[0088] Example 9. Production of LiPO2F2 using phosphoryl fluoride and formic acid In a flask equipped with a stirrer, condenser, and thermometer, 300 g of dimethoxyethane and 50 g (481 mmol) of phosphoryl fluoride were added under a nitrogen atmosphere, and the mixture was stirred while the internal temperature was cooled to 5°C. Subsequently, 13.1 g (505 mmol) of lithium fluoride was added, and the mixture was stirred at a low temperature. Then, 23.2 g (505 mmol) of formic acid was gradually added dropwise, and the temperature was raised to 45°C and the reaction was carried out for 5 hours. After the reaction was complete, the reaction mixture 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 46.7 g (433 mmol) of white powdered lithium difluorophosphate. (Yield 90%, purity 99%, impurity anion content: F 16.2 ppm, Cl 2.1 ppm, SO4 13.3 ppm, PO4 10.5 ppm)
[0089] [Table 1] [Industrial applicability]
[0090] This invention relates to a method for producing lithium difluorophosphate salt in high purity and high yield without using lithium hexafluoride phosphate, and according to this invention, lithium difluorophosphate salt can be produced economically. Furthermore, this invention provides a high-purity lithium difluorophosphate salt with reduced impurities, and when used in an electrolyte for lithium secondary batteries, it can improve electrochemical properties, provide high output, and reduce gas emissions.
Claims
1. Step 1) Phosphoryl halide (POX) of the following chemical formula 2 ３ ) A step of 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) The step of 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; Method for producing lithium difluorophosphate salt: [Chemical formula 2] 【Chemistry 1】 [Chemical formula 3] 【Chemistry 2】 [Chemical formula 4] 【Transformation 3】 [Chemical formula 5] MF ｎ [Chemical formula 1] 【Chemistry 4】 In the above chemical formula X is Cl, Br, or I. R1 and R2 are independently H, C1-10 alkyl group, phenyl group, OH, OR3, and 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. Both R1 and R2 can form a ring with 2 to 5 carbon atoms, which can contain one or more heterogeneous elements, O or N. M is H, Li, Na, K, Ca, Zn, Sb, Rb, Cs, or an onium ion. n is either 1 or 2.
2. Step 1') Phosphoryl halide of the following chemical formula 2 (POX ３ ) A step of reacting a compound, 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') A step in which the difluorophosphate of chemical formula 6 is reacted with a lithium salt to produce the lithium difluorophosphate of chemical formula 1 shown below; A method for producing lithium difluorophosphate salts, including: [Chemical formula 2] 【Transformation 5】 [Chemical formula 3] 【Transformation 6】 [Chemical formula 5] MF ｎ [Chemical formula 6] 【Transformation 7】 [Chemical formula 1] 【Transformation 8】 In the above chemical formula X is Cl, Br, or I. R1 and R2 are independently H, C1-10 alkyl group, phenyl group, OH, OR3, and NH. ２ NHR4, NR5R6, ONa, OK or ONH ４ And, R3, R4, R5, and R6 are each independently a C1-10 alkyl group or phenyl group. Both R1 and R2 can form a ring with 2 to 5 carbon atoms, which can contain one or more heterogeneous elements, O or N. M is H, Li, Na, K, Ca, Zn, Sb, Rb, Cs, or an onium ion. n is either 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 comprising the step of: [Chemical formula 7] 【Chemistry 9】 [Chemical formula 3] 【Chemistry 10】 [Chemical formula 1] 【Chemistry 11】 In the above chemical formula R1 and R2 are independently H, C1-10 alkyl group, phenyl group, OH, OR3, and 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. Both R1 and R2 can form rings with 2 to 5 carbon atoms, each containing one or more heterogeneous elements, such as O or N.
4. A method for producing lithium difluorophosphate salt according to claim 1, 2, or 3, characterized in that 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.
5. Lithium salts include lithium acetate, lithium azide, lithium bicarbonate, lithium bisulfate, lithium carbonate, lithium fluoride, lithium chloride, lithium bromide, lithium iodide, lithium cyanide, lithium dodecaborate, lithium hydride, and lithium hydroxide. A method for producing a lithium difluorophosphate salt according to claim 1, 2, or 3, characterized in that the selected material is one or more selected from the group consisting of hydroxyl, lithium nitrate, lithium oxalate, lithium oxide, lithium perchlorate, lithium sulfate, lithium sulfide, lithium sulfide, lithium amide, and mixtures thereof.
6. A method for producing lithium difluorophosphate according to claim 1, 2, or 3, characterized in that the production of lithium difluorophosphate is carried out under solvent conditions.
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, haloalkanes, nitriles, ethers, alcohols, esters, and carbonates.
8. A method for producing a lithium difluorophosphate salt according to claim 1 or 2, characterized by reacting 1 to 1.5 equivalents of a lithium salt with 1 equivalent of a phosphoryl halide.
9. A method for producing lithium difluorophosphate salt according to claim 3, characterized in that 1 to 1.5 equivalents of lithium salt are reacted with 1 equivalent of phosphoryl fluoride.
10. A method for producing a lithium difluorophosphate salt according to claim 1 or 2, characterized by reacting 1 to 1.5 equivalents of an oxidizing agent with 1 equivalent of phosphoryl halide.
11. A method for producing lithium difluorophosphate salt 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. For every 1 equivalent of phosphoryl halide, MF ｎ A method for producing a lithium difluorophosphate salt according to claim 1 or 2, characterized by reacting 2 to 8 equivalents of the ingredients.