A degassing device for liquid lithium hexafluorophosphate and a degassing method thereof

Abstract

The application discloses a kind of liquid lithium hexafluorophosphate degassing device and its degassing method, including scraper evaporator E201, concentrated collection tank V301 after degassing, condenser E202, solvent collection tank V303 and vacuum pump P103, wherein, the scraper evaporator E201 is connected with the delivery pipeline of liquid lithium hexafluorophosphate raw material, and the liquid lithium hexafluorophosphate raw material is under the action of heating and rotating centrifugal force of the scraper evaporator E201, part liquid produces vaporization, and the material of vaporization is transported to the condenser E202, and the liquid that is not vaporized is transported to the concentrated collection tank V301 after degassing;The output end of the condenser E202 is connected with the solvent collection tank V303, and the gas phase output end of the solvent collection tank V303 is connected with the vacuum pump P103;The application realizes high-efficiency excellent degassing effect, and finally ensures that the hydrogen chloride content of liquid lithium hexafluorophosphate after degassing treatment by the application is less than 10ppm, reliably guarantees its performance as lithium ion battery electrolyte.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery electrolytes, specifically relating to a degassing device and method for liquid lithium hexafluorophosphate. Background Technology

[0002] The synthesis of liquid lithium hexafluorophosphate usually involves reacting lithium fluoride suspended in carbonate with phosphorus pentafluoride / hydrogen chloride gas. Therefore, the resulting liquid lithium hexafluorophosphate will contain a certain proportion of dissolved hydrogen chloride gas. Hydrogen chloride gas is an impurity of liquid lithium salt and needs to be removed to purify and remove impurities from the liquid lithium hexafluorophosphate material system. Then, the purified and impurity-removed liquid lithium hexafluorophosphate is used in the electrolyte formulation of lithium-ion batteries to replace solid lithium hexafluorophosphate.

[0003] Furthermore, due to the polarization effect of lithium hexafluorophosphate in the solvent, the solubility of gaseous hydrogen chloride in the solvent increases. According to the applicant's tests, the content of lithium hexafluorophosphate in liquid lithium hexafluorophosphate is 28-30%, the content of hydrogen chloride is 5-6%, and the remaining components are trace amounts of hydrogen fluoride and solvent. When it is used as an electrolyte for lithium-ion batteries, it will significantly affect the working performance of lithium-ion batteries. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a degassing device and method for liquid lithium hexafluorophosphate, which achieves a highly efficient and excellent degassing effect, and ultimately ensures that the hydrogen chloride content of the liquid lithium hexafluorophosphate after degassing treatment is less than 10 ppm, thus reliably guaranteeing its performance when used as an electrolyte in lithium-ion batteries.

[0005] The technical solution adopted in this invention is as follows:

[0006] A degassing device for liquid lithium hexafluorophosphate includes a scraped evaporator, a degassing concentration and collection tank, a condenser, a solvent collection tank, and a vacuum pump, wherein...

[0007] The scraped evaporator is connected to the pipeline for conveying liquid lithium hexafluorophosphate raw material. Under the action of heating and centrifugal force of the scraped evaporator, part of the liquid lithium hexafluorophosphate raw material vaporizes. The vaporized material is conveyed to the condenser, and the unvaporized liquid is conveyed to the degassing concentration and collection tank.

[0008] The output end of the condenser is connected to the solvent collection tank, and the gas phase output end of the solvent collection tank is connected to the vacuum pump.

[0009] Preferably, the outer wall of the scraped evaporator is provided with a heat medium jacket for providing heat, and the inner wall is provided with scrapers. At the same time, the interior of the scraped evaporator is provided with a driveable rotating stirring shaft, which is connected to the scrapers to enable the scrapers to rotate along the inner wall of the scraped evaporator.

[0010] Preferably, a stirring frame is provided between the stirring shaft and the scraper, and the stirring frame is provided with a movable hinge.

[0011] Preferably, a heat medium is introduced into the heat medium jacket to provide heat to the interior of the scraped evaporator; the liquid lithium hexafluorophosphate raw material liquid located inside the scraped evaporator is vaporized by the centrifugal force of the rotating scraper.

[0012] Preferably, the temperature range of the heat medium in the heat medium jacket is 20-90℃, and more preferably 30-60℃.

[0013] Preferably, the rotational speed of the stirring shaft is 30-200 rpm, more preferably 50-100 rpm; and / or the feed flow rate of the liquid lithium hexafluorophosphate feedstock to the scraped evaporator is 1.8-2.2 kg / h, more preferably 1.9-2.1 kg / h; and / or the operating pressure range of the scraped evaporator is set to -0.8 to 0.1 MPaG, more preferably -0.092 to -0.099 MPaG.

[0014] Preferably, a metering pump and a first mass flow meter are installed on the pipeline for conveying the liquid lithium hexafluorophosphate feedstock; a second mass flow meter is installed on the pipeline between the unvaporized liquid and the degassing concentration collection tank; the output end of the degassing concentration collection tank is connected to a first conveying pump, which then delivers the liquid to the deacidification section.

[0015] Preferably, a demister and a third mass flow meter are installed on the conveying pipeline between the vaporized material and the condenser.

[0016] Preferably, the vaporized material enters the heat exchange tube of the condenser, and is cooled by a refrigerant located outside the heat exchange tube to form liquid carbonate and hydrogen chloride gas, which then enter the interior of the solvent collection tank. The liquid carbonate is then pumped to the solvent refining section via a second transfer pump, and the hydrogen chloride gas is pumped to the tail gas treatment section via a vacuum pump.

[0017] Preferably, a degassing method for liquid lithium hexafluorophosphate employs the liquid lithium hexafluorophosphate degassing device described above; under the heating and centrifugal force of the scraped evaporator (E201), a portion of the liquid lithium hexafluorophosphate raw material is vaporized; the vaporized material is conveyed to the condenser (E202), and the unvaporized liquid is conveyed to the degassing concentration and collection tank (V301); the degassing concentration and collection tank (V301) outputs degassed liquid lithium hexafluorophosphate, and ion chromatography analysis shows that the hydrogen chloride content in the degassed liquid lithium hexafluorophosphate is less than 10 ppm.

[0018] This invention provides a dedicated degassing device for liquid lithium hexafluorophosphate feedstock. Specifically, a scraped evaporator is used to degas the liquid lithium hexafluorophosphate feedstock. During operation, under the heating and centrifugal force of the scraped evaporator, a portion of the liquid (i.e., the liquid carbonate and dissolved hydrogen chloride in the liquid lithium hexafluorophosphate feedstock) vaporizes, thereby achieving a highly efficient and excellent degassing effect. Ultimately, this ensures that the hydrogen chloride content of the liquid lithium hexafluorophosphate after degassing is less than 10 ppm, reliably guaranteeing its performance when used as a lithium-ion battery electrolyte. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the degassing device for liquid lithium hexafluorophosphate according to a specific embodiment of the present invention;

[0020] Figure 2 This is a schematic diagram of the scraper evaporator E201 in a specific embodiment of the present invention. Detailed Implementation

[0021] Please see Figure 1 and Figure 2 As shown, this embodiment provides a degassing device for liquid lithium hexafluorophosphate, including a scraped evaporator E201, a degassing concentration and collection tank V301, a condenser E202, a solvent collection tank V303, and a vacuum pump P103. The scraped evaporator E201 is connected to the conveying pipeline of the liquid lithium hexafluorophosphate raw material. Under the heating and centrifugal force of the scraped evaporator E201, part of the liquid lithium hexafluorophosphate raw material vaporizes. The vaporized material is conveyed to the condenser E202, and the unvaporized liquid is conveyed to the degassing concentration and collection tank V301. The output end of the condenser E202 is connected to the solvent collection tank V303, and the gas phase output end of the solvent collection tank V303 is connected to the vacuum pump P103.

[0022] Preferably, in this embodiment, the outer wall E21a of the scraped evaporator E201 is provided with a heat medium jacket 22 for providing heat, and the inner wall is provided with a scraper 23. At the same time, the interior of the scraped evaporator E201 is provided with a rotatable stirring shaft 24 (driven rotation is achieved by a stirring motor M). The stirring shaft 24 is connected to the scraper 23 to enable the scraper 23 to rotate along the inner wall E21b of the scraped evaporator E201. More preferably, in order to facilitate installation, in this embodiment, a stirring frame 25 is provided between the stirring shaft 24 and the scraper 23, and a movable hinge 26 is provided on the stirring frame 25.

[0023] Preferably, in this embodiment, a heat medium is introduced into the heat medium jacket 22 to provide heat to the interior of the scraped evaporator; the liquid lithium hexafluorophosphate feed liquid inside the scraped evaporator E201 is vaporized by the centrifugal force of the rotating scraper; more preferably, in this embodiment, the temperature range of the heat medium in the heat medium jacket 22 is 20-90℃, preferably 30-60℃; the rotation speed range of the stirring shaft 24 is 30-200rpm, preferably 50-100rpm; and / or preferably, in this embodiment, the feed flow rate of the liquid lithium hexafluorophosphate feed liquid to the scraped evaporator E201 is 1.8-2.2kg / h, preferably 1.9-2.1kg / h; and / or preferably, in this embodiment, the operating pressure range of the scraped evaporator E201 is set to -0.8 to 0.1 MPaG, preferably -0.092 to -0.099 MPaG; note that MPaG in this application refers to gauge pressure.

[0024] Preferably, in this embodiment, a metering pump P100 and a first mass flow meter M401 are sequentially installed on the conveying pipelines S501, S502, and S503 for the liquid lithium hexafluorophosphate feedstock; a second mass flow meter M402 is installed on the conveying pipeline S504 between the unvaporized liquid and the degassed concentration collection tank V301; the output end of the degassed concentration collection tank V301 is connected to the first conveying pump P101 through the conveying pipeline S505, and is sent to the deacidification section through the first conveying pump P101 and the conveying pipeline S506.

[0025] Preferably, to further ensure degassing efficiency, in this embodiment, a demister V302 and a third mass flow meter M403 are respectively installed on the conveying pipelines S507 and S508 between the vaporized material and the condenser E202. The vaporized material enters the heat exchange tubes of the condenser E202, and is cooled by the refrigerant located outside the heat exchange tubes to form liquid carbonate and hydrogen chloride gas, which enter the interior of the solvent collection tank V303 together. The liquid carbonate is sent to the solvent refining section through the conveying pipeline S510, the second conveying pump P102 and the conveying pipeline S511. The hydrogen chloride gas is sent to the tail gas treatment section through the conveying pipeline S512, the vacuum pump P103 and the conveying pipeline S513.

[0026] Preferably, this embodiment also provides a degassing method for liquid lithium hexafluorophosphate, which uses the above-mentioned degassing device for liquid lithium hexafluorophosphate to carry out degassing; under the heating and centrifugal force of the scraped evaporator E201, part of the liquid lithium hexafluorophosphate raw material is vaporized; the vaporized material is transported to the condenser E202, and the unvaporized liquid is transported to the degassing concentration and collection tank V301; the degassing concentration and collection tank V301 outputs degassed liquid lithium hexafluorophosphate, and the hydrogen chloride content in the degassed liquid lithium hexafluorophosphate is less than 10 ppm as detected by ion chromatography.

[0027] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this invention.

[0028] Based on the above-described implementation scheme, this application further proposes the following specific embodiments 1 and 2: Example

[0029] The synthesized liquid lithium hexafluorophosphate feed solution was analyzed by ion chromatography, and after conversion, it was found that the content of lithium hexafluorophosphate in the liquid lithium hexafluorophosphate feed solution was 28.5%, the content of hydrogen chloride was 4.5%, and the content of hydrogen fluoride was 0.08%; and the content of methyl ethyl carbonate in the liquid lithium hexafluorophosphate feed solution was 99.92% by gas chromatography.

[0030] In this embodiment 1, the above-mentioned liquid lithium hexafluorophosphate feed solution is degassed using the degassing device provided in this embodiment as follows:

[0031] The heat medium enters the heat medium jacket 22 of the scraped evaporator E201 through the regulating valve FV601 and its pipeline. The first temperature gauge T801 displays the temperature entering the jacket, specifically 52℃; the second temperature gauge T802 displays the jacket temperature, specifically 48℃.

[0032] Step 2: Start vacuum pump P103 to evacuate the system. Pressure gauge P701 of scraped evaporator E201 shows that the operating pressure of scraped evaporator E201 is -0.098 MPaG.

[0033] Step 3: Start the stirring motor M of the scraper evaporator E201 and adjust the speed of the stirring shaft 24 to 85 rpm;

[0034] Step 4: Introduce refrigerant into the refrigerant side of condenser E202. The incoming refrigerant temperature is -15℃.

[0035] Step 5: The liquid lithium hexafluorophosphate feed solution is fed through metering pump P100 and first mass flow meter M401 to adjust the feed flow rate, which is set to 2 kg / h. After the liquid lithium hexafluorophosphate feed solution enters the scraped evaporator E201, the liquid is evenly scraped by scraper 23 to form a film on the inner wall E21b of the scraped evaporator E201, and exchanges heat with the heat medium located in the heat medium jacket 22 to obtain heat. The hydrogen chloride and methyl ethyl carbonate in the liquid are rapidly vaporized and escape from the liquid, rising and entering the demister V302 through the conveying pipeline S507. The function of the demister V302 is to capture the liquid droplets in the gas and make them coalesce, so as not to enter the gas phase pipeline and reduce the entrainment of the solute lithium hexafluorophosphate.

[0036] Step 6: By interlocking the automatic control valve FV601 with the third mass flow meter M403, the gas flow rate is adjusted. The third mass flow meter M403 displays a mass flow rate of 0.16 kg / h (that is, the mass flow rate of the vaporized material). At the same time, the liquid product flow rate (that is, the mass flow rate of the unvaporized material) is displayed as 1.84 kg / h on the second mass flow meter M402. The degassed liquid lithium hexafluorophosphate enters the degassed concentration collection tank V301 through the conveying pipeline S504 and the second mass flow meter M402, and then is sent to the deacidification section through the first conveying pump P101.

[0037] The degassed liquid lithium hexafluorophosphate (i.e., degassed liquid lithium hexafluorophosphate) was analyzed by ion chromatography. The results showed that the content of lithium hexafluorophosphate in the degassed liquid lithium hexafluorophosphate obtained in this example was 30.97%, the content of hydrogen fluoride was 0.06%, and the content of hydrogen chloride was 0.0008% (less than 10 ppm).

[0038] The gaseous products (i.e., the vaporized material) from the scraped evaporator E201 are cooled by the condenser E202 (which is equipped with the third thermometer T803 and the fourth thermometer T804 respectively). The fourth thermometer T804 shows 2.5℃. The non-condensable hydrogen chloride is sent to the tail gas treatment section through the outlet of the vacuum pump P103. Ethyl methyl carbonate is collected in the solvent collection tank V303 and sent to the solvent refining section through the second transfer pump P102 for refining and reuse. Example

[0039] The synthesized liquid lithium hexafluorophosphate feed solution was analyzed by ion chromatography, and after conversion, it was found that the content of lithium hexafluorophosphate in the liquid lithium hexafluorophosphate feed solution was 28.8%, the content of hydrogen chloride was 4.3%, and the content of hydrogen fluoride was 0.078%; and the content of methyl ethyl carbonate in the liquid lithium hexafluorophosphate feed solution was 99.91% by gas chromatography.

[0040] In Example 2, the above-mentioned liquid lithium hexafluorophosphate feed solution is degassed using the degassing device provided in this example as follows:

[0041] The heat medium enters the heat medium jacket 22 of the scraped evaporator E201 through the regulating valve FV601 and its pipeline. The first temperature gauge T801 displays the temperature entering the jacket, specifically 51℃; the second temperature gauge T802 displays the jacket temperature, specifically 46℃.

[0042] Step 2: Start vacuum pump P103 to evacuate the system. Pressure gauge P701 of scraped evaporator E201 shows that the operating pressure of scraped evaporator E201 is -0.094 MPaG.

[0043] Step 3: Start the stirring motor M of the scraper evaporator E201 and adjust the speed of the stirring shaft 24 to 90 rpm;

[0044] Step 4: Introduce refrigerant into the refrigerant side of condenser E202. The incoming refrigerant temperature should be 5℃.

[0045] Step 5: The liquid lithium hexafluorophosphate feed solution is fed through metering pump P100 and first mass flow meter M401 to adjust the feed flow rate, which is set to 2.2 kg / h. After the liquid lithium hexafluorophosphate feed solution enters the scraped evaporator E201, the liquid is evenly scraped by scraper 23 to form a film on the inner wall E21b of the scraped evaporator E201, and exchanges heat with the heat medium located in the heat medium jacket 22 to obtain heat. The hydrogen chloride and methyl ethyl carbonate in the liquid are rapidly vaporized and escape from the liquid, rising and entering the demister V302 through the conveying pipeline S507. The function of the demister V302 is to capture the liquid droplets in the gas and make them coalesce, so as not to enter the gas phase pipeline and reduce the entrainment of the solute lithium hexafluorophosphate.

[0046] Step 6: By interlocking the automatic control valve FV601 with the third mass flow meter M403, the gas flow rate is adjusted. The third mass flow meter M403 displays a mass flow rate of 0.17 kg / h (that is, the mass flow rate of the vaporized material). At the same time, the liquid product flow rate (that is, the mass flow rate of the unvaporized material) is displayed as 1.85 kg / h on the second mass flow meter M402. The degassed liquid lithium hexafluorophosphate enters the degassed concentration collection tank V301 through the conveying pipeline S504 and the second mass flow meter M402, and then is sent to the deacidification section through the first conveying pump P101.

[0047] The degassed liquid lithium hexafluorophosphate (i.e., degassed liquid lithium hexafluorophosphate) was analyzed by ion chromatography. The results showed that the content of lithium hexafluorophosphate in the degassed liquid lithium hexafluorophosphate obtained in this example was 30.97%, the content of hydrogen fluoride was 0.054%, and the content of hydrogen chloride was 0.0006% (less than 10 ppm).

[0048] The gaseous products (i.e., the vaporized material) from the scraped evaporator E201 are cooled by the condenser E202 (which is equipped with the third thermometer T803 and the fourth thermometer T804 respectively). The fourth thermometer T804 shows 2.5℃. The non-condensable hydrogen chloride is sent to the tail gas treatment section through the outlet of the vacuum pump P103. Ethyl methyl carbonate is collected in the solvent collection tank V303 and sent to the solvent refining section through the second transfer pump P102 for refining and reuse.

[0049] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0050] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for degassing liquid lithium hexafluorophosphate, characterized in that, It includes a scraped evaporator (E201), a degassed concentration and collection tank (V301), a condenser (E202), a solvent collection tank (V303), and a vacuum pump (P103), among which, The scraped evaporator (E201) is connected to the pipeline for conveying liquid lithium hexafluorophosphate feedstock. Under the heating and centrifugal force of the scraped evaporator (E201), part of the liquid lithium hexafluorophosphate feedstock vaporizes and is conveyed to the condenser (E202). The unvaporized liquid is conveyed to the degassing concentration collection tank (V301). The outer wall (E21a) of the scraped evaporator (E201) is provided with a heat medium jacket (22) for providing heat, and the inner wall is provided with scrapers (23). At the same time, the scraped evaporator (E201) is provided with a driveable rotating stirring shaft (24) inside. The stirring shaft (24) is connected to the scrapers (23) to enable the scrapers (23) to rotate along the inner wall (E21b) of the scraped evaporator (E201). The temperature range of the heat medium in the heat medium jacket (22) is 20-90℃. The rotation speed range of the stirring shaft (24) is 30-200rpm. The feed flow rate of liquid lithium hexafluorophosphate raw material liquid to the scraped evaporator (E201) is 1.8-2.2kg / h. The operating pressure range of the scraped evaporator (E201) is set to -0.092 to -0.099MPaG. The output end of the condenser (E202) is connected to the solvent collection tank (V303), and the gas phase output end of the solvent collection tank (V303) is connected to the vacuum pump (P103). The vaporized material enters the heat exchange tubes of the condenser (E202), where it is cooled by a refrigerant located outside the heat exchange tubes to form liquid carbonate and hydrogen chloride gas, which then enter the solvent collection tank (V303). The liquid carbonate is then pumped to the solvent refining section via a second transfer pump (P102), and the hydrogen chloride gas is pumped to the tail gas treatment section via a vacuum pump (P103). The degassed liquid lithium hexafluorophosphate output from the degassed concentration and collection tank (V301) is detected by ion chromatography, and the hydrogen chloride content in the degassed liquid lithium hexafluorophosphate is less than 10 ppm.

2. The degassing method for liquid lithium hexafluorophosphate according to claim 1, characterized in that, A stirring frame (25) is provided between the stirring shaft (24) and the scraper (23), and a movable hinge (26) is provided on the stirring frame (25).

3. The degassing method for liquid lithium hexafluorophosphate according to claim 1, characterized in that, The heat medium is introduced into the heat medium jacket (22) to provide heat to the interior of the scraped evaporator; the liquid lithium hexafluorophosphate raw material liquid inside the scraped evaporator (E201) is vaporized by the centrifugal force of the rotating scraper.

4. The degassing method for liquid lithium hexafluorophosphate according to claim 1, characterized in that, The temperature range of the heat medium in the heat medium jacket (22) is 30-60℃.

5. The degassing method for liquid lithium hexafluorophosphate according to claim 1, characterized in that, The rotational speed of the stirring shaft (24) is 50-100 rpm; and / or the feed flow rate of the liquid lithium hexafluorophosphate feedstock to the scraped evaporator (E201) is 1.9-2.1 kg / h.

6. The degassing method for liquid lithium hexafluorophosphate according to claim 1, characterized in that, A metering pump (P100) and a first mass flow meter (M401) are installed on the pipeline for conveying the liquid lithium hexafluorophosphate feedstock; a second mass flow meter (M402) is installed on the pipeline between the unvaporized liquid and the degassing concentration collection tank (V301); the output end of the degassing concentration collection tank (V301) is connected to the first delivery pump (P101), and the liquid is sent to the deacidification section through the first delivery pump (P101).

7. The degassing method for liquid lithium hexafluorophosphate according to claim 1, characterized in that, A demister (V302) and a third mass flow meter (M403) are installed on the conveying pipeline between the vaporized material and the condenser (E202).

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