Deacidification method of electrolyte material, deacidified electrolyte material and application

Abstract

The invention provides a deacidification method of an electrolyte material, the deacidified electrolyte material and application. The deacidification method comprises the following steps: adding lithium chloride into an acid-containing electrolyte material, carrying out deacidification reaction, and carrying out solid-liquid separation to obtain a deacidified electrolyte material; wherein degassing is carried out in the process of the deacidification reaction, or degassing is carried out between the step of deacidification reaction and the step of solid-liquid separation. According to the invention, lithium chloride is used as an acid removing agent, and can react with acid in the acid-containing electrolyte material, so that the acid in the acid-containing electrolyte material can be removed, and the acidity is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of battery manufacturing, and relates to a method for deacidifying an electrolyte material, an electrolyte material after deacidification, and an application thereof. Background Art

[0002] With the rapid development of electric vehicles, lithium-ion batteries have become the main type of power batteries. High-performance lithium-ion batteries have many advantages such as high energy density, high operating voltage, wide operating temperature range, high number of cycles, no memory and safety, and are also key core technologies in the production, storage and use of new energy. The electrolyte is the soul and core technology of lithium-ion batteries, which plays a role in transporting charges. The performance of the electrolyte determines the performance indicators of lithium-ion batteries such as storage capacity, electrochemical properties, safety and environmental protection, and is a key factor affecting the performance of lithium-ion batteries.

[0003] The raw materials for preparing the electrolyte include lithium salt concentrate and solvent. As an electrolyte material, lithium salt concentrate inevitably contains acid, such as hydrogen fluoride or oxalic acid, which makes it have a higher acidity. However, electrolyte materials with high acidity are not suitable for preparing electrolytes and will affect performance.

[0004] Therefore, how to reduce the acidity of electrolyte materials is a technical problem that needs to be solved urgently. Summary of the invention

[0005] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a method for deacidifying an electrolyte material, an electrolyte material after deacidification, and an application thereof. The present invention uses lithium chloride as an acid scavenger, and lithium chloride can react with the acid in the acid-containing electrolyte material, thereby removing the acid in the acid-containing electrolyte material and reducing the acidity; after lithium chloride reacts with the acid, HCl and lithium-containing precipitates are generated, and the generated HCl can be removed by degassing, that is, HCl is discharged from the electrolyte material in the form of gas, thereby avoiding HCl from affecting the acidity of the electrolyte material, and the lithium-containing precipitate can be removed by the solid-liquid separation step; in summary, the deacidification method of the present invention can effectively reduce the acidity of the acid-containing electrolyte material.

[0006] To achieve this object, the present invention adopts the following technical solutions:

[0007] In a first aspect, the present invention provides a method for removing acid from an electrolyte material, the method comprising:

[0008] Adding lithium chloride to an acid-containing electrolyte material to perform an acid removal reaction, and obtaining an acid-removed electrolyte material after solid-liquid separation;

[0009] Wherein, degassing is performed during the deacidification reaction, or degassing is performed between the deacidification reaction and the solid-liquid separation step.

[0010] The deacidification method for an electrolyte material provided by the present invention has simple steps. Lithium chloride is used as an acid scavenger. The lithium chloride can react with the acid in the acid-containing electrolyte material, thereby removing the acid in the acid-containing electrolyte material and reducing the acidity. After the lithium chloride reacts with the acid, HCl and lithium-containing precipitates are generated. The generated HCl can be removed by degassing, that is, HCl is discharged from the electrolyte material in the form of gas, thereby preventing HCl from affecting the acidity of the electrolyte material, and the lithium-containing precipitates can be removed by a solid-liquid separation step. In summary, the deacidification method of the present invention can effectively reduce the acidity of the acid-containing electrolyte material.

[0011] The present invention preferably performs degassing during the acid removal reaction because degassing during the acid removal reaction can promote the positive direction of the acid removal reaction and facilitate the removal of acid; and solid-liquid separation can be performed directly after the reaction is completed, which can save time and improve efficiency.

[0012] Preferably, the water content of the lithium chloride is ≤500ppm, for example, it can be 500ppm, 450ppm, 400ppm, 350ppm, 300ppm, 250ppm, 200ppm, 100ppm or 50ppm, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0013] In the present invention, dry lithium chloride, i.e. lithium chloride with a water content of ≤500 ppm, is required to be used for the deacidification reaction, because HCl generated by the deacidification reaction cannot be discharged by degassing after being dissolved in water.

[0014] Preferably, the lithium chloride is in powder form.

[0015] Preferably, the amount of lithium chloride added is 0.1 to 4.0 times the theoretical mass of lithium chloride required to completely remove the acid in the acid-containing electrolyte material, for example, it can be 0.1 times, 0.2 times, 0.3 times, 0.45 times, 0.5 times, 0.6 times, 0.8 times, 1.0 times, 1.5 times, 2.0 times, 2.5 times, 3.0 times, 3.5 times or 4.0 times, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable, preferably 0.45 to 2.5 times.

[0016] It should be noted that the calculation formula for the theoretical mass of lithium chloride required to completely remove the acid in the acid-containing electrolyte material in the present invention is as follows:

[0017]

[0018] Among them, m (理论LiCl) is the theoretical mass of lithium chloride, in g; m (溶液) is the total mass of the acid electrolyte material, in g; C (酸度)M is the acidity of the acid-containing electrolyte material (the acidity is calculated in HF, the same below), unit: ppm; (LiCl) is the molar mass of lithium chloride, in g / mol; M (HF) is the molar mass of hydrogen fluoride, in g / mol.

[0019] In the present invention, when the input amount of lithium chloride is 0.1 to 4.0 times the theoretical mass of lithium chloride required to completely remove the acid in the acid-containing electrolyte material, the acidity of the electrolyte material can be effectively reduced; further, when the input amount of lithium chloride meets the preferred range of 0.45 to 2.5 times, the acidity of the electrolyte material can be further reduced.

[0020] Preferably, the acid in the acid-containing electrolyte material includes hydrogen fluoride (HF) and / or oxalic acid (H2C2O4).

[0021] In the present invention, the reaction equation of hydrogen fluoride and lithium chloride is as follows: HF+LiCl=LiF↓+HCl↑.

[0022] The reaction equation of oxalic acid and lithium chloride is as follows: H2C2O4+2LiCl=Li2C2O4↓+2HCl↑.

[0023] Preferably, the acid-containing electrolyte material further comprises lithium salt and aprotic solvent, that is, the acid-containing electrolyte material is a lithium salt concentrate, which is used to provide lithium salt for the electrolyte.

[0024] In the present invention, when the solvent in the acid-containing electrolyte material is an aprotic solvent, the solubility of HCl in the electrolyte material is very low and can be removed by degassing.

[0025] Preferably, the lithium salt includes any one of lithium hexafluorophosphate, lithium difluorooxalatoborate or lithium difluorobisoxalatophosphate, or a combination of at least two thereof.

[0026] In the present invention, when the lithium salt is lithium hexafluorophosphate, the acid in the acid-containing electrolyte material is hydrogen fluoride; when the lithium salt is lithium difluorooxalatoborate and / or lithium difluorobisoxalatophosphate, the acid in the acid-containing electrolyte material is oxalic acid.

[0027] Preferably, the aprotic solvent includes any one of diethyl carbonate, ethyl methyl carbonate, ethylene carbonate or propylene carbonate, or a combination of at least two thereof.

[0028] Preferably, the water content of the acid-containing electrolyte material is ≤50ppm, for example, it can be 50ppm, 45ppm, 40ppm, 35ppm, 30ppm, 20ppm or 10ppm, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0029] The deacidification method of the present invention is suitable for acid-containing electrolyte materials with low water content. This is to avoid the problem that HCl generated by the deacidification reaction cannot be discharged through degassing after dissolving in water. The present invention controls the water content of the acid-containing electrolyte material to ≤50ppm. Within this range, HCl can be normally discharged through degassing.

[0030] Preferably, the temperature of the deacidification reaction is 0-60°C, for example, it can be 0°C, 5°C, 10°C, 20°C, 30°C, 40°C, 50°C or 60°C, but is not limited to the listed values. Other unlisted values ​​within the numerical range are also applicable, preferably 20-45°C.

[0031] In the present invention, when the acid removal reaction temperature is too low, the reaction rate will be affected; when the acid removal reaction temperature is too high, it is easy to cause decomposition of the electrolyte material.

[0032] Preferably, the deacidification reaction time is 3 to 16 hours, for example, it can be 3 hours, 4 hours, 5 hours, 8 hours, 10 hours, 12 hours, 14 hours or 16 hours, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0033] In the present invention, under the acid removal reaction time of 3 to 16 hours, it can be ensured that the acid removal agent reacts more fully with the acid in the acid-containing electrolyte material.

[0034] Preferably, the degassing method includes degassing under reduced pressure.

[0035] Preferably, the absolute pressure of the reduced pressure degassing is ≤1000Pa, for example, it can be 1000Pa, 900Pa, 800Pa, 600Pa, 500Pa, 400Pa or 300Pa, but is not limited to the listed values. Other unlisted values ​​within the numerical range are also applicable, preferably ≤800Pa.

[0036] In the present invention, when the absolute pressure of the reduced pressure degassing is too high, the corresponding vacuum degree will be too small, which will affect the removal of HCl and cause the acidity to be high.

[0037] Preferably, when the degassing is carried out between the deacidification reaction and the solid-liquid separation steps, the degassing temperature is 0 to 60°C, for example, it can be 0°C, 5°C, 10°C, 20°C, 30°C, 40°C, 50°C or 60°C, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable, preferably 20 to 45°C.

[0038] In the present invention, when the degassing is performed between the deacidification reaction and the solid-liquid separation step, the degassing temperature is controlled within the above-defined range, which can increase the HCl removal rate. When the degassing temperature is too low, the rate will be affected; when the degassing temperature is too high, it is easy to cause the decomposition of the electrolyte material.

[0039] It should be noted that in the deacidification method of the present invention, when degassing is performed during the deacidification reaction, the temperature of the deacidification reaction is the degassing temperature.

[0040] Preferably, the solid-liquid separation method includes filtration.

[0041] Preferably, the acid removal method is carried out under a dry atmosphere.

[0042] In a second aspect, the present invention provides a deacidified electrolyte material, wherein the deacidified electrolyte material is prepared by the deacidification method described in the first aspect.

[0043] Preferably, the acidity of the electrolyte material after acid removal is ≤100ppm, for example, it can be 100ppm, 90ppm, 80ppm, 70ppm, 60ppm, 50ppm, 40ppm, 30ppm, 20ppm or 10ppm, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable, preferably ≤50ppm.

[0044] In a third aspect, the present invention provides an electrolyte, wherein the electrolyte contains the deacidified electrolyte material described in the second aspect.

[0045] In a fourth aspect, the present invention provides a secondary battery, wherein the secondary battery comprises the electrolyte described in the third aspect. The secondary battery may be, for example, a lithium secondary battery.

[0046] The numerical range described in the present invention not only includes the point values ​​listed above, but also includes any point values ​​between the above numerical ranges that are not listed. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0047] Compared with the prior art, the present invention has the following beneficial effects:

[0048] The deacidification method for an electrolyte material provided by the present invention has simple steps. Lithium chloride is used as an acid scavenger. The lithium chloride can react with the acid in the acid-containing electrolyte material, thereby removing the acid in the acid-containing electrolyte material and reducing the acidity. After the lithium chloride reacts with the acid, HCl and lithium-containing precipitates are generated. The generated HCl can be removed by degassing, that is, HCl is discharged from the electrolyte material in the form of gas, thereby preventing HCl from affecting the acidity of the electrolyte material, and the lithium-containing precipitates can be removed by a solid-liquid separation step. In summary, the deacidification method of the present invention can effectively reduce the acidity of the acid-containing electrolyte material. DETAILED DESCRIPTION

[0049] The technical solution of the present invention is further illustrated below through specific implementation methods.

[0050] Example 1

[0051] This embodiment provides a method for deacidifying an electrolyte material, wherein the electrolyte material is a lithium difluorooxalatoborate concentrate, the concentrate containing lithium difluorooxalatoborate, ethyl methyl carbonate, oxalic acid and water, and the water content of the concentrate is 46 ppm; the deacidifying method comprises the following steps:

[0052] (1) drying LiCl in a vacuum oven at 105° C. for 24 h, and then grinding the LiCl into a powder with a particle size D50 of 360 μm for later use;

[0053] (2) In a dry nitrogen atmosphere, 105 g of an electrolyte material with an acidity of 365 ppm was weighed and added to a reaction bottle, and then 0.12 g of LiCl powder with a water content of 100 ppm was added, and the mixture was stirred at 25° C. for a deacidification reaction for 12 h. During the reaction, degassing was continuously performed under reduced pressure, and the absolute pressure of the degassing was 780 Pa. The deacidified electrolyte material was then filtered.

[0054] The acidity of the electrolyte material after deacidification was tested by acid-base titration and was 21 ppm.

[0055] Example 2

[0056] This embodiment provides a method for removing acid from an electrolyte material, wherein the electrolyte material is a lithium difluorobisoxalate phosphate concentrate, the concentrate containing lithium difluorobisoxalate phosphate, ethyl methyl carbonate, oxalic acid and water, and the water content of the concentrate is 32 ppm; the method comprises the following steps:

[0057] (1) drying LiCl in a vacuum oven at 110° C. for 24 h, and then grinding the LiCl into a powder with a particle size D50 of 460 μm for later use;

[0058] (2) In a dry nitrogen atmosphere, 110 g of an electrolyte material with an acidity of 1102 ppm was weighed and added to a reaction bottle, and then 0.26 g of LiCl powder with a water content of 124 ppm was added, and a deacidification reaction was carried out at 45° C. for 6 h. After the reaction was completed, the reduced pressure degassing was carried out at a temperature of 45° C. and an absolute pressure of 710 Pa for 5 h, and then the deacidified electrolyte material was obtained by filtration.

[0059] Using the same testing method as in Example 1, the acidity of the electrolyte material after acid removal was measured to be 47 ppm.

[0060] Example 3

[0061] This embodiment provides a method for removing acid from an electrolyte material, wherein the electrolyte material is a lithium hexafluorophosphate concentrate, the concentrate contains lithium hexafluorophosphate, ethyl methyl carbonate, hydrogen fluoride and water, and the water content of the concentrate is 21 ppm; the method comprises the following steps:

[0062] (1) drying LiCl in a vacuum oven at 110° C. for 12 h, and then grinding the LiCl into a powder with a particle size D50 of 360 μm for later use;

[0063] (2) In a dry nitrogen atmosphere, 500 g of an electrolyte material with an acidity of 237 ppm was weighed and added to a reaction bottle, and then 0.2 g of LiCl powder with a water content of 200 ppm was added. The mixture was stirred at 35° C. for a deacidification reaction for 6 h. During the reaction, degassing was continuously performed under reduced pressure, and the absolute pressure of the degassing was 780 Pa. The deacidified electrolyte material was then filtered.

[0064] Using the same testing method as in Example 1, the acidity of the electrolyte material after acid removal was measured to be 28 ppm.

[0065] Example 4

[0066] The difference between this embodiment and embodiment 1 is that the amount of LiCl powder added in step (2) is 0.02 g. The other parameters are the same as those in embodiment 1.

[0067] Using the same testing method as in Example 1, the acidity of the electrolyte material after acid removal was measured to be 97 ppm.

[0068] Example 5

[0069] The difference between this embodiment and embodiment 1 is that the amount of LiCl powder added in step (2) is 0.40 g. The other parameters are the same as those in embodiment 1.

[0070] Using the same testing method as in Example 1, the acidity of the electrolyte material after acid removal was measured to be 18 ppm.

[0071] It can be seen from Examples 1-5 that the acidity of the electrolyte material after deacidification obtained by the method of the present invention is ≤100ppm; further, in Examples 1-3, lithium chloride is added according to a preferred ratio, that is, the input amount of lithium chloride is 0.45 to 2.5 times the theoretical mass of lithium chloride required to completely remove the acid in the acid-containing electrolyte material, and the acidity of the electrolyte material after deacidification is ≤50ppm. It can be seen from Examples 1 and 4 that when the amount of acid scavenger LiCl added is on the small side, the acidity decreases less. It can be seen from Examples 1 and 5 that when the amount of acid scavenger LiCl added is on the large side, it is difficult to further improve the acid reduction effect.

[0072] Example 6

[0073] The difference between this embodiment and embodiment 1 is that the vacuum oven drying time is adjusted so that the water content of the LiCl powder added in step (2) is 3120 ppm. The other parameters are the same as those in embodiment 1.

[0074] Using the same testing method as in Example 1, the acidity of the electrolyte material after acid removal was measured to be 219 ppm.

[0075] It can be seen from Examples 1 and 6 that when the water content of the acid scavenger LiCl is too high, there is too much water in the reaction system, and part of the HCl generated by the acid scavenging reaction is dissolved in water and cannot be discharged by degassing, resulting in a higher acidity of the electrolyte material after acid scavenging.

[0076] Example 7

[0077] The difference between this embodiment and embodiment 1 is that the absolute pressure of the reduced pressure degassing in step (2) is 2200 Pa. The other parameters are the same as those in embodiment 1.

[0078] Using the same testing method as in Example 1, the acidity of the electrolyte material after acid removal was measured to be 233 ppm.

[0079] It can be seen from Example 1 and Example 7 that when the absolute pressure of the reduced pressure degassing is too high, the corresponding vacuum degree will be too small, which will affect the removal of HCl and cause high acidity.

[0080] The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention are within the protection scope and disclosure scope of the present invention.

Claims

1. A method for removing acid from electrolyte materials, characterized in that: The acid removal method comprises: Adding lithium chloride to an acid-containing electrolyte material to perform an acid removal reaction, and obtaining an acid-removed electrolyte material after solid-liquid separation; Wherein, degassing is performed during the deacidification reaction, or degassing is performed between the deacidification reaction and the solid-liquid separation step.

2. The acid removal method according to claim 1, characterized in that: The water content of the lithium chloride is ≤500ppm; Preferably, the lithium chloride is in powder form.

3. The deacidification method according to claim 1 or 2, characterized in that: The input amount of the lithium chloride is 0.1 to 4.0 times, preferably 0.45 to 2.5 times, the theoretical mass of lithium chloride required to completely remove the acid in the acid-containing electrolyte material.

4. The deacidification method according to any one of claims 1 to 3, characterized in that: The acid in the acid-containing electrolyte material includes hydrogen fluoride and / or oxalic acid; Preferably, the acid-containing electrolyte material further includes a lithium salt and an aprotic solvent; Preferably, the lithium salt includes any one of lithium hexafluorophosphate, lithium difluorooxalatoborate or lithium difluorobisoxalatophosphate, or a combination of at least two thereof; Preferably, the aprotic solvent includes any one of diethyl carbonate, ethyl methyl carbonate, ethylene carbonate or propylene carbonate, or a combination of at least two thereof.

5. The acid removal method according to any one of claims 1 to 4, characterized in that: The water content of the acid-containing electrolyte material is ≤50ppm.

6. The acid removal method according to any one of claims 1 to 5, characterized in that: The temperature of the acid removal reaction is 0 to 60°C, preferably 20 to 45°C; Preferably, the acid removal reaction time is 3 to 16 hours.

7. The acid removal method according to any one of claims 1 to 6, characterized in that: The degassing method includes decompression degassing; Preferably, the absolute pressure of the reduced pressure degassing is ≤1000Pa; Preferably, when the degassing is performed between the deacidification reaction and the solid-liquid separation step, the degassing temperature is 0 to 60° C., preferably 20 to 45° C.; Preferably, the solid-liquid separation method includes filtration; Preferably, the acid removal method is carried out under a dry atmosphere.

8. A deacidified electrolyte material, characterized in that: The deacidified electrolyte material is prepared by the deacidification method according to any one of claims 1 to 7; Preferably, the acidity of the electrolyte material after acid removal is ≤100 ppm, preferably ≤50 ppm.

9. An electrolyte, characterized in that: The electrolyte contains the deacidified electrolyte material according to claim 8.

10. A secondary battery, characterized in that: The secondary battery includes the electrolyte according to claim 9.

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