A method for preparing an electrolyte
Through the combination technology of multi-stage ceramic membrane and molecular sieve filtration, the problem of high loss of precision filter element in electrolyte preparation is solved, and the low color preparation of electrolyte is achieved, reducing production costs and improving production efficiency.
Patent Information
- Application Number
- CN202210936517.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2022-08-05
- Publication Date
- 2024-12-20
- Estimated Expiration
- 2042-08-05
AI Technical Summary
In the existing electrolyte preparation process, the filter element loss rate of precision filters is high, resulting in increased production costs and reduced production efficiency, and it is impossible to fundamentally solve the problem of electrolyte impurities.
The combination of multi-stage ceramic membrane module and molecular sieve filter is adopted to reduce the color of the electrolyte by centrifugation, temperature adjustment and multi-stage ceramic membrane filtration, avoid the use of precision filters, and reduce filter element losses.
It effectively reduces the color of the electrolyte, reduces the frequency of use of precision filters, saves the cost of filter element materials, improves production efficiency, and improves product stability and safety.
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of lithium batteries, in particular to a method for preparing an electrolyte. Background Art
[0002] Lithium-ion batteries are widely used in various electrical appliances, among which the electrolyte bears the heavy responsibility of conducting ions and electrons, and is the key to the high performance of lithium-ion batteries. The electrolyte generally contains raw materials such as organic solvents, active lithium salts, stabilizers, and other necessary additives. When preparing, different raw materials need to be mixed evenly in a liquid phase environment under certain conditions and in a certain proportion. Since different raw materials carry more or less impurities, and the mixing equipment cannot be completely free of other substances, the mixed coarse material obtained in the preparation process contains more impurities. These impurities will consume electrical energy during the battery charging and discharging process, greatly reducing the voltage stability and safety of the battery, so they must be removed.
[0003] In the existing electrolyte production process, the mixed coarse electrolyte material is filtered through a precision filter. The pore size of the precision filter is very small, which can remove fine impurities, so as to meet the quality inspection requirements of the electrolyte. However, it is precisely because the pore size of the precision filter is very small that the filter element is easily clogged. After filtering one or two batches of electrolyte coarse material, it is often necessary to stop the machine and replace the filter element. Such high filter element loss brings great production burden to the enterprise.
[0004] Patent application CN111082137A discloses a method for preparing a low-turbidity lithium-ion battery electrolyte, comprising S1, adding diethyl carbonate-ethylene carbonate-ethyl methyl carbonate to a mixing tank in sequence according to corresponding weight portions, starting a stirrer in the mixing tank to mix the above-mentioned raw material liquids evenly to form a primary electrolyte; S2, adding lithium hexafluorophosphate to the primary electrolyte in accordance with corresponding weight portions; S3, adding propylene carbonate-vinyl carbonate to the intermediate electrolyte in sequence according to corresponding weight portions, and propylene carbonate and vinylene carbonate are filtered during the flow process; in the present invention, lithium hexafluorophosphate is added before propylene carbonate, so that lithium hexafluorophosphate can be fully dissolved and reacted before propylene carbonate is added, and when propylene carbonate is added, the impurities inside it will no longer react, thereby not affecting the turbidity problem of the final product, thereby ensuring the product quality. This solution optimizes the order of adding materials by adjusting the production steps to avoid reactions between coherent raw materials, but it can only be used in lithium hexafluorophosphate systems. Even after the preparation is completed according to the above steps, it is still necessary to use precision filters to further reduce the turbidity, which cannot fundamentally solve the problem. Summary of the invention
[0005] The purpose of the present invention is to overcome the problem of high loss rate of precision filter elements in the existing electrolyte preparation technology, and to provide a method for preparing an electrolyte. By coordinating process steps, the chromaticity of the electrolyte can be reduced to below 30 degrees, thereby eliminating the need for precision filters, thereby greatly saving filter element loss and reducing production costs.
[0006] The specific plan is as follows:
[0007] A method for preparing an electrolyte comprises the following steps:
[0008] 1) obtaining a crude electrolyte material, centrifuging the crude electrolyte material, and collecting a centrifuge;
[0009] 2) adjusting the temperature of the centrifuge liquid, and then sending it to a primary ceramic membrane for separation, wherein the pore size of the primary ceramic membrane is 20-40 nm, and the obtained primary dialysate is sent to a molecular sieve filter to collect the primary filtrate;
[0010] 3) sending the primary filtrate into a magnetic filter to remove ferromagnetic impurities and then sending it into a secondary ceramic membrane, wherein the secondary ceramic membrane is a rotating ceramic membrane with a pore size of 1-10 nm; collecting the secondary dialysate to obtain an electrolyte.
[0011] Furthermore, the electrolyte coarse material in step 1) is a mixed composition of raw materials for preparing the electrolyte and has not been filtered. Preferably, the electrolyte has an impurity mass content of 0.01-20%, including solid impurities, ferromagnetic impurities, water and aluminum hydroxide.
[0012] Furthermore, the centrifugal speed in step 1) is 25000-50000 r / min, and the time is 5-10 min.
[0013] Furthermore, in step 2), the temperature of the centrifuge is adjusted to 10°C-30°C.
[0014] Furthermore, the molecular sieve filter in step 2) is of 3A grade and has a size of 3-5 mm.
[0015] Furthermore, the method also includes step 4) sending the secondary dialysate into a precision filter for filtration to obtain an electrolyte.
[0016] Furthermore, the filtration pore size of the precision filter in step 4) is 0.1-5μm, and the filter element loss rate is less than 1 piece / ton of material. Preferably, the filtration pore size of the precision filter is 0.1-1μm, and the filter element of the precision filter is a dead-end filtration method. The retained substances during the filtration process will form a filter cake layer on the surface of the filter element, thereby improving the filtration accuracy.
[0017] Furthermore, the chromaticity of the electrolyte does not exceed 30 degrees.
[0018] Furthermore, after the primary ceramic membrane has been running for a period of time, nitrogen is used for backwashing, and the concentrated liquid of the primary ceramic membrane is combined with the coarse electrolyte material for circulation.
[0019] Furthermore, the concentrated liquid of the secondary ceramic membrane is merged into the primary dialysate for reflux treatment.
[0020] Beneficial effects:
[0021] The method for preparing the electrolyte of the present invention is applicable to the preparation process of most lithium ion electrolytes. The chromaticity of the electrolyte can be reduced to a required range by the method, and the battery can be directly filled without the need for a precision filter. The precision filter can be used as an emergency device.
[0022] Furthermore, the preparation method of the electrolyte of the present invention adjusts the temperature of the centrifuge liquid before feeding it into the separation component in view of the presence of volatile components in the electrolyte, thereby avoiding component loss, reducing component content fluctuations, and improving product stability.
[0023] Furthermore, the electrolyte in the present invention contains organic solvents that corrode the equipment, and the polymer material membrane assembly is intolerant to organic solvents. Therefore, a two-stage ceramic membrane assembly of inorganic materials is selected for filtration, wherein the primary ceramic membrane is used to filter slightly larger particles, and the pore size is 20-40nm. The secondary ceramic membrane has a pore size of 1-10nm and is used to filter slightly smaller particles. If a ceramic membrane with a pore size of 1-10nm is directly used to filter the centrifuge liquid, the same problem as the precision filter will be faced, that is, frequent membrane clogging. The use of two-stage ceramic membrane assemblies in series, combined with a molecular sieve filter, can reduce the processing pressure of the terminal ceramic membrane, and at the same time combine the self-cleaning ability of the selected ceramic membrane to ensure the normal operation of the entire set of equipment. DETAILED DESCRIPTION
[0024] The preferred embodiments of the present invention will be described in more detail below. Although the preferred embodiments of the present invention are described below, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein. In the examples, those without specifying specific techniques or conditions are carried out according to the techniques or conditions described in the literature in this area or according to the product specification. Those without specifying the manufacturer of reagents or instruments used are all conventional products that can be obtained commercially. In the following examples, if not clearly stated, "%" refers to weight percentage.
[0025] Example 1
[0026] A method for preparing an electrolyte comprises the following steps:
[0027] 1) Obtain 100 L of electrolyte rough material, the main components of which are: lithium hexafluorophosphate or LiFSI (lithium bis(fluorosulfonyl)imide), ethyl methyl carbonate, ethylene carbonate film-forming additive, conductive additive, flame retardant additive, overcharge protection additive, etc.
[0028] The electrolyte coarse material is centrifuged at a speed of 28000 r / min for 5 min, and the centrifuge liquid is collected.
[0029] 2) The centrifugal liquid is sent to a heat exchanger, the temperature of the centrifugal liquid is adjusted to 25°C, and then sent to a primary ceramic membrane for separation, the pore size of the primary ceramic membrane is 20-30nm, and the obtained primary dialysate is sent to a molecular sieve filter to collect the primary filtrate. The molecular sieve is 3A grade and has a size of 3-5mm.
[0030] 3) The primary filtrate is sent to a magnetic filter to remove ferromagnetic impurities and then sent to a secondary ceramic membrane to collect the secondary dialysate to obtain an electrolyte. The secondary ceramic membrane is a rotating ceramic membrane with a pore size of 1-5 nm. The chromaticity of the obtained secondary dialysate is below 30 degrees, which meets the chromaticity requirements and can be directly filled.
[0031] Example 2
[0032] A method for preparing an electrolyte comprises the following steps:
[0033] 1) Obtain 100 L of electrolyte crude material, the main components of which include lithium hexafluorophosphate or LiFSI (lithium bis(fluorosulfonyl)imide), diethyl carbonate, ethyl methyl carbonate, film-forming additives, conductive additives, flame retardant additives, overcharge protection additives, etc. Centrifuge the electrolyte crude material at a speed of 25,000 r / min for 5 min, and collect the centrifuge liquid.
[0034] 2) The centrifugal liquid is sent to a heat exchanger, the temperature of the centrifugal liquid is adjusted to 25°C, and then sent to a primary ceramic membrane for separation, the pore size of the primary ceramic membrane is 20-30nm, and the obtained primary dialysate is sent to a molecular sieve filter to collect the primary filtrate. The molecular sieve is 3A grade and has a size of 3-5mm.
[0035] 3) The primary filtrate is sent to a magnetic filter to remove ferromagnetic impurities and then sent to a secondary ceramic membrane to collect the secondary dialysate. The secondary ceramic membrane is a rotating ceramic membrane with a pore size of 10 nm. The secondary dialysate is then subjected to the next step;
[0036] 4) Send the secondary dialysate to a precision filter for filtration. The filter pore size is 0.1 μm. The filter element of the precision filter is a dead-end filtration method. The filtrate is collected. If the chromaticity is below 30 degrees, it can be directly filled.
[0037] One ton of material was processed continuously according to the above process, and the filter element was not blocked.
[0038] Example 3
[0039] A method for preparing an electrolyte comprises the following steps:
[0040] 100 L of electrolyte rough material was obtained, and the electrolyte rough material mainly consisted of lithium hexafluorophosphate or LiFSI (lithium bis(fluorosulfonyl)imide), diethyl carbonate, ethyl methyl carbonate, film-forming additives, conductive additives, flame retardant additives, overcharge protection additives, etc. The electrolyte rough material was centrifuged at a speed of 40,000 r / min for 5 min, and the centrifuge was collected.
[0041] 2) The centrifugal liquid is sent to a heat exchanger, the temperature of the centrifugal liquid is adjusted to 30°C, and then sent to a primary ceramic membrane for separation, the pore size of the primary ceramic membrane is 30-40nm, and the obtained primary dialysate is sent to a molecular sieve filter to collect the primary filtrate. The molecular sieve is 3A grade and has a size of 3-5mm.
[0042] 3) The primary filtrate is sent to a magnetic filter to remove ferromagnetic impurities and then sent to a secondary ceramic membrane to collect the secondary dialysate. The secondary ceramic membrane is a rotating ceramic membrane with a pore size of 5-8 nm. The secondary dialysate is then sent to the next step;
[0043] 4) Send the secondary dialysate to a precision filter for filtration. The filter pore size is 1 μm. The filter element of the precision filter is a dead-end filtration method. The filtrate is collected. If the chromaticity is below 30 degrees, it can be directly filled.
[0044] One ton of material was processed continuously according to the above process, and the filter element was not blocked.
[0045] Example 4
[0046] A method for preparing an electrolyte comprises the following steps:
[0047] 100 L of electrolyte rough material was obtained, and the electrolyte rough material mainly consisted of lithium hexafluorophosphate or LiFSI (lithium bis(fluorosulfonyl)imide), diethyl carbonate, ethyl methyl carbonate, film-forming additives, conductive additives, flame retardant additives, overcharge protection additives, etc. The electrolyte rough material was centrifuged at a speed of 30,000 r / min for 10 min, and the centrifuge was collected.
[0048] 2) The centrifuge liquid is sent to a heat exchanger, the temperature of the centrifuge liquid is adjusted to 25°C, and then sent to a primary ceramic membrane for separation, the pore size of the primary ceramic membrane is 25-30nm, and the obtained primary dialysate is sent to a molecular sieve filter to collect the primary filtrate. The molecular sieve is 3A grade and has a size of 3-5mm.
[0049] 3) The primary filtrate is sent to a magnetic filter to remove ferromagnetic impurities and then sent to a secondary ceramic membrane to collect the secondary dialysate. The secondary ceramic membrane is a rotating ceramic membrane with a pore size of 10 nm. The secondary dialysate is then subjected to the next step;
[0050] 4) Send the secondary dialysate to a precision filter for filtration. The filter pore size is 0.1 μm. The filter element of the precision filter is a dead-end filtration method. The filtrate is collected. If the chromaticity is below 30 degrees, it can be directly filled.
[0051] One ton of material was processed continuously according to the above process, and the filter element was not blocked.
[0052] Comparative Example 1
[0053] Take 100L of the electrolyte coarse material in Example 1 and send it into the precision filter in Example 2. The filter element loss rate is: 5 pieces / ton of material.
[0054] Using the method in Example 1 of the present invention, the investment cost of setting up the equipment is about 4-4.5 million. According to the market price of the filter element of 80-90 yuan, based on an annual output of 20,000 tons of electrolyte, the cost of replacing the filter element is about 8-9 million.
[0055] It can be seen that the method of the present invention can save 8-9 million filter element material costs for enterprises every year, with a small one-time investment and convenient equipment maintenance. It can avoid production stoppages caused by stopping work to replace filter elements, and can greatly improve production efficiency.
[0056] Comparative Example 2
[0057] Referring to Example 1, only a primary ceramic membrane is used. Specifically, the preparation method of the electrolyte comprises the following steps:
[0058] 100 L of electrolyte rough material was obtained, the main components of which were lithium hexafluorophosphate or LiFSI (lithium bis(fluorosulfonyl)imide), ethyl methyl carbonate, ethylene carbonate film-forming additive, conductive additive, flame retardant additive, overcharge protection additive, etc., which were from the same batch as in Example 1.
[0059] The electrolyte coarse material is centrifuged at a speed of 28000 r / min for 5 min, and the centrifuge liquid is collected.
[0060] 2) The centrifugal liquid is sent to a heat exchanger, the temperature of the centrifugal liquid is adjusted to 25°C, and then sent to a primary ceramic membrane for separation, the pore size of the primary ceramic membrane is 20-30nm, and the obtained primary dialysate is sent to a molecular sieve filter to collect the primary filtrate. The molecular sieve is 3A grade and has a size of 3-5mm.
[0061] 3) The primary filtrate is sent to a magnetic filter to remove ferromagnetic impurities. However, the chromaticity does not meet the requirements of qualified products and the filling operation cannot be performed.
[0062] The filtrate after removing ferromagnetic impurities was sent to a precision filter for filtration. The filter pore size was 0.1 μm and the filter element of the precision filter was a dead-end filtration method. It was found that the electrolyte had a greater impact on the precision filter element and the filter element was severely damaged. This may be because some organic solvents in the filtrate damaged the filter element of the precision filter.
[0063] Comparative Example 3
[0064] Referring to Example 2, the secondary ceramic membrane adopts a conventional honeycomb ceramic membrane. Specifically, the preparation method of the electrolyte includes the following steps:
[0065] 1) Obtain 100 L of electrolyte rough material, the electrolyte rough material mainly comprising lithium hexafluorophosphate or LiFSI (lithium bis(fluorosulfonyl)imide), diethyl carbonate, ethyl methyl carbonate, film-forming additives, conductive additives, flame retardant additives, overcharge protection additives, etc., which are the same batch as Example 2.
[0066] The electrolyte coarse material is centrifuged at a speed of 25000 r / min for 5 min, and the centrifuge liquid is collected.
[0067] 2) The centrifugal liquid is sent to a heat exchanger, the temperature of the centrifugal liquid is adjusted to 25°C, and then sent to a primary ceramic membrane for separation, the pore size of the primary ceramic membrane is 20-30nm, and the obtained primary dialysate is sent to a molecular sieve filter to collect the primary filtrate. The molecular sieve is 3A grade and has a size of 3-5mm.
[0068] 3) The primary filtrate is sent to a magnetic filter to remove ferromagnetic impurities and then sent to a secondary ceramic membrane to collect the secondary dialysate. The secondary ceramic membrane adopts a honeycomb ceramic membrane with a pore size of 10 nm. It was found that the overall flux of the honeycomb ceramic membrane with the same precision is lower than that of the rotating ceramic membrane. This is because the primary ceramic membrane coarsely filters the electrolyte containing many fine impurities, which greatly pollutes the honeycomb membrane core. The rotating ceramic membrane is a dynamic ceramic membrane, which can use the rotation method to reduce the pollution of the primary ceramic membrane coarsely filters the electrolyte and play a self-cleaning role.
[0069] Due to the low flux of the honeycomb ceramic membrane, the efficiency of treating the feed solution in step 3) decreases by about 50%, and a longer operation time is consumed.
[0070] 4) Send the secondary dialysate to a precision filter for filtration. The filter pore size is 0.1 μm. The filter element of the precision filter is a dead-end filtration method. The filtrate is collected. If the chromaticity is below 30 degrees, it can be directly filled.
[0071] The preferred embodiments of the present invention are described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, a variety of simple modifications can be made to the technical solution of the present invention, and these simple modifications all belong to the protection scope of the present invention.
[0072] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.
[0073] In addition, various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.
Claims
1. A method for preparing an electrolyte, characterized in that: The following steps are involved: 1) obtaining a crude electrolyte material, wherein the crude electrolyte material is a mixture of raw materials for preparing an electrolyte and has not been filtered, and the crude electrolyte material is centrifuged to collect a centrifuge; 2) adjusting the temperature of the centrifuge liquid, and then sending it to a primary ceramic membrane for separation, wherein the pore size of the primary ceramic membrane is 20-40 nm, and the obtained primary dialysate is sent to a molecular sieve filter to collect the primary filtrate; 3) sending the primary filtrate into a magnetic filter to remove ferromagnetic impurities and then sending it into a secondary ceramic membrane, wherein the secondary ceramic membrane is a rotating ceramic membrane with a pore size of 1-10 nm; The secondary dialysate is collected to obtain the electrolyte.
2. The method for preparing the electrolyte according to claim 1, characterized in that: The impurity mass content of the electrolyte in step 1) is 0.01-20%, including solid impurities, ferromagnetic impurities, water and aluminum hydroxide.
3. The method for preparing the electrolyte according to claim 1 or 2, characterized in that: The centrifugal speed in step 1) is 25000-50000 r / min, and the time is 5-10 min.
4. The method for preparing the electrolyte according to claim 1, characterized in that: In step 2), the temperature of the centrifuge is adjusted to 10°C-30°C.
5. The method for preparing the electrolyte according to claim 1 or 4, characterized in that: The molecular sieve filter in step 2) is of 3A grade and has a size of 3-5 mm.
6. The method for preparing the electrolyte according to claim 1, characterized in that: The method also includes step 4) sending the secondary dialysate into a precision filter for filtration to obtain an electrolyte.
7. The method for preparing the electrolyte according to claim 6, characterized in that: The filtration pore size of the precision filter in step 4) is 0.1-5 μm, and the filter element loss rate is less than 1 piece / ton of material.
8. The method for preparing the electrolyte according to claim 7, characterized in that: The filtration pore size of the precision filter is 0.1-1 μm.
9. The method for preparing the electrolyte according to any one of claims 6 to 8, characterized in that: The chromaticity of the electrolyte does not exceed 30 degrees.
10. The method for preparing the electrolyte according to claim 1, characterized in that: After the primary ceramic membrane has been running for a period of time, nitrogen is used for backwashing, and the concentrated liquid of the primary ceramic membrane is combined with the electrolyte coarse material for circulation.
11. The method for preparing the electrolyte according to claim 1, characterized in that: The concentrated liquid from the secondary ceramic membrane is merged into the primary dialysate for reflux treatment.