Method for removing Ba < 2 + > and Ca < 2 + > in LiCl-KCl electrolyte

Abstract

The invention discloses a method for removing Ba < 2 + > and Ca < 2 + > in LiCl-KCl electrolyte, and belongs to the technical field of high-temperature molten salt impurity removal. The method comprises the following steps: adding a curing agent into a LiCl-KCl electrolyte containing one or two ions of Ba < 2 + > and Ca < 2 + > in a molten state for reaction to generate a high-melting-point salt solid, and removing the contained Ba < 2 + > and Ca < 2 + > through solid-liquid separation to realize purification of the electrolyte. The method is simple in treatment process, short in time consumption and low in treatment cost; in addition, according to the method, treatment can be directly carried out in original production equipment, the treated electrolyte can be directly used for production, and additional treatment equipment is not needed.

Description

Technical Field

[0001] The present invention relates to the technical field of high temperature molten salt impurity removal, and in particular to a method for removing Ba from LiCl-KCl electrolyte. 2+ , Ca 2+ method. Background Art

[0002] With the development of new energy in recent years, the market demand for lithium and related products has gradually increased. The status of lithium and its compounds in the battery field has become increasingly important. Among them, metallic lithium is widely used in energy storage, chemical industry, medicine, metallurgy, electronics industry and other fields. The production methods of metallic lithium include vacuum thermal reduction method and molten salt electrolysis method. Among them, molten salt electrolysis method is more commonly used in industry. Molten lithium chloride and potassium chloride are used as raw materials for electrolysis to prepare metallic lithium. In the production process of molten salt electrolysis, with the continuous electrolysis production, the content of metal cation impurities in the molten salt is also getting higher and higher, mainly Ba 2+ Mg 2+ , Ca 2+ 、Na + Since the decomposition voltage of BaCl2 is higher than that of LiCl and KCl, as the electrolysis proceeds, the impurity Ba 2+ Gradually enriched; the decomposition voltage of CaCl2 is very close to that of LiCl, and a small amount of Ca 2+ If the electrolyte is not treated, the Ba in the electrolyte 2+ , Ca 2+ When enriched to a certain concentration, it will affect the quality of electrolytic lithium metal and reduce the efficiency of electrolytic current.

[0003] At present, the following methods are generally used to remove barium ions from LiCl-KCl electrolyte:

[0004] ① Replacement method: replace the molten salt electrolyte;

[0005] ② Dilution method: Mix new electrolyte and old electrolyte to dilute the impurities;

[0006] ③ Wet purification: After the molten electrolyte is cooled, it is dissolved in water to obtain an electrolyte solution. According to different impurity ions, corresponding impurity removers are added. After sedimentation / filter pressure / centrifugation, the purified electrolyte solution is obtained. Finally, the purified electrolyte is obtained by crystallization and drying.

[0007] ④ Pre-electrolysis de-impurization: Utilize the different decomposition voltages between substances in the electrolyte to preferentially electrolyze the impurities in the electrolyte, thereby separating the impurities.

[0008] Among them, the replacement and dilution methods cannot remove the barium ions in the electrolyte and are costly; the wet method has a better impurity removal effect, but the treatment process is long, the cost is high, and an additional wet treatment line is required; because the decomposition voltages of BaCl2 and CaCl2 are higher and closer to LiCl and KCl, respectively, pre-electrolysis cannot preferentially electrolyze BaCl2, CaCl2, etc. 2+ There are also some remnants.

[0009] In view of this, the present invention is proposed. Summary of the invention

[0010] The object of the present invention is to provide a method for removing Ba from LiCl-KCl electrolyte. 2+ , Ca 2+ method to solve or improve the above technical problems.

[0011] The present invention can be implemented like this:

[0012] In a first aspect, the present invention provides a method for removing Ba from LiCl-KCl electrolyte. 2+ , Ca 2+ The method comprises the following steps: adding Ba 2+ , Ca 2+ A curing agent is added to the LiCl-KCl electrolyte containing one or two ions to react and generate a high melting point salt solid. The Ba contained in the solid-liquid separation is then removed. 2+ , Ca 2+ .

[0013] In an optional embodiment, the actual amount of curing agent added is 90% to 110% of the theoretical amount added.

[0014] In an optional embodiment, the curing agent includes at least one of potassium sulfate, lithium sulfate, sodium sulfate and sodium phosphate.

[0015] In an alternative embodiment, a curing agent is added to the LiCl-KCl electrolyte at a temperature of 400°C to 500°C.

[0016] In an optional embodiment, the reaction temperature of the LiCl-KCl electrolyte and the curing agent is not less than 400°C.

[0017] In an optional embodiment, when the curing agent is at least one of potassium sulfate, lithium sulfate and sodium sulfate, the reaction temperature of the LiCl-KCl electrolyte and the curing agent is 400°C to 1000°C.

[0018] In an optional embodiment, when the curing agent is sodium phosphate, the reaction temperature of the LiCl-KCl electrolyte and the curing agent is 400°C to 500°C.

[0019] In an optional embodiment, the reaction time of the LiCl-KCl electrolyte and the curing agent is 1 h to 5 h.

[0020] In an optional embodiment, the reaction system is cooled to 400° C. to 500° C. after the reaction is completed, followed by solid-liquid separation.

[0021] In an optional embodiment, the solid-liquid separation is performed by filtration.

[0022] In an optional embodiment, the filtration method includes any one of natural filtration, vacuum filtration and pressure filtration.

[0023] The beneficial effects of the present invention include:

[0024] By forming a high melting point barium salt and / or calcium salt precipitate with the curing agent and the barium ions and / or calcium ions contained in the LiCl-KCl electrolyte, and then performing solid-liquid separation, the purpose of removing barium and / or calcium ions can be achieved, and the electrolyte can be purified. The method has a simple treatment process, short time consumption, low treatment cost, and does not generate wastewater and waste gas during the treatment process; in addition, the method can be directly processed in the original production equipment, and the treated electrolyte can be directly used in production without the need for additional treatment equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0026] Figure 1 The present invention provides a method for removing Ba from LiCl-KCl electrolyte. 2+ , Ca 2+ Process flow chart of the method. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the technical scheme in the embodiments of the present invention will be described clearly and completely below. If the specific conditions are not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be purchased commercially.

[0028] The present invention provides a method for removing Ba from LiCl-KCl electrolyte. 2+ , Ca 2+ The method is described in detail.

[0029] The present invention proposes a method for removing Ba from LiCl-KCl electrolyte. 2+ , Ca 2+ Please combine the method Figure 1 , comprising the following steps: adding Ba to a molten state 2+ , Ca 2+ A curing agent is added to the LiCl-KCl electrolyte containing one or two ions to react and generate a high melting point salt solid. The Ba contained in the solid-liquid separation is then removed. 2+ , Ca 2+ .

[0030] By mixing the curing agent with Ba in the electrolyte 2+ , Ca 2+ The formation of high melting point salt precipitation, followed by solid-liquid separation, can achieve the purpose of removing barium ions and calcium ions, and realize the purification of electrolytes. This method has a simple treatment process, short time consumption, low treatment cost, no wastewater and waste gas are generated during the treatment process, and basically no other cationic impurities are introduced; in addition, this method can be directly processed in the original production equipment, and the treated electrolyte can be directly used in production without the need for additional treatment equipment.

[0031] In some optional embodiments, the curing agent may illustratively include at least one of potassium sulfate, lithium sulfate, sodium sulfate and sodium phosphate.

[0032] Correspondingly, the curing agents react with Ba in LiCl-KCl electrolyte. 2+ , Ca 2+ The reaction equation is as follows:

[0033] BaCl2+K2SO4=BaSO4↓+2KCl;

[0034] BaCl2+Li2SO4=BaSO4↓+2LiCl;

[0035] BaCl2+Na2SO4=BaSO4↓+2NaCl;

[0036] 3BaCl2+2Na3PO4=Ba3(PO4)2↓+6NaCl;

[0037] CaCl2+K2SO4=CaSO4↓+2KCl;

[0038] CaCl2+Li2SO4=CaSO4↓+2LiCl;

[0039] CaCl2+Na2SO4=CaSO4↓+2NaCl;

[0040] 3CaCl2+2Na3PO4=Ca3(PO4)2↓+6NaCl;

[0041] In some optional embodiments, the actual amount of curing agent added can be 90% to 110% of the theoretical amount, such as 90%, 95%, 100%, 105% or 110%, etc., or other values ​​within the range of 90% to 110%. In some more typical embodiments, the actual amount of curing agent added is 100% to 110% of the theoretical amount.

[0042] For reference, the theoretical addition amount of the above curing agent can be calculated as follows: Theoretical addition amount of sodium phosphate curing agent = (molecular mass of curing agent × mass of LiCl-KCl electrolyte × content of barium in the mass of LiCl-KCl electrolyte) / (1.5 × atomic mass of barium × purity of curing agent) + (molecular mass of curing agent × mass of LiCl-KCl electrolyte × content of calcium in the mass of LiCl-KCl electrolyte) / (1.5 × atomic mass of calcium × purity of curing agent). Among them, 1.5 is obtained according to the valence state of barium ion and phosphate ion and the corresponding molar ratio; Theoretical addition amount of sulfate curing agent = (molecular mass of curing agent × mass of LiCl-KCl electrolyte × content of barium in the mass of LiCl-KCl electrolyte) / (atomic mass of barium × purity of curing agent) + (molecular mass of curing agent × mass of LiCl-KCl electrolyte × content of calcium in the mass of LiCl-KCl electrolyte) / (atomic mass of calcium × purity of curing agent).

[0043] It should be noted that the addition amount of curing agent reaches 90% of the theoretical amount to achieve a better Ba 2+ , Ca 2+ Removal rate; the higher the amount of curing agent added, the greater the effect of curing agent on Ba 2+ , Ca 2+ The removal effect is better; however, if the amount of curing agent added is too high, additional impurities may be introduced.

[0044] In some optional embodiments, a curing agent is added to a LiCl-KCl electrolyte at a temperature of 400° C. to 500° C. (such as 400° C., 420° C., 440° C., 460° C., 480° C. or 500° C.). The reaction temperature of the LiCl-KCl electrolyte and the curing agent is not less than 400° C.

[0045] If the temperature of the LiCl-KCl electrolyte is too low, the LiCl-KCl electrolyte cannot be in a molten liquid form; if the temperature of the LiCl-KCl electrolyte is too high, the reaction after the curing agent is added will be too violent.

[0046] In actual operation, if the LiCl-KCl electrolyte to be treated is a production material in a molten state, it can be directly transferred to a de-impurity tank to mix and react with a curing agent, or it can be heated to maintain it at 400°C to 500°C; if the LiCl-KCl electrolyte to be treated is a storage material, it can be first transferred to a de-impurity tank and then heated until its temperature reaches the above temperature.

[0047] If a sulfate curing agent (potassium sulfate, lithium sulfate, sodium sulfate) is used, the reaction temperature is controlled to 400°C to 1000°C after adding the curing agent.

[0048] If a phosphate curing agent (sodium phosphate) is used, the reaction temperature should be controlled at 400°C to 500°C after adding the curing agent. If the reaction temperature exceeds 500°C, the reaction will not occur, affecting the impurity removal effect.

[0049] In some optional embodiments, the reaction time of the LiCl-KCl electrolyte and the curing agent can be 1 h to 5 h, such as 1 h, 1.5 h, 2 h, 2.5 h, 3 h, 3.5 h, 4 h, 4.5 h or 5 h, or other values ​​within the range of 1 h to 5 h.

[0050] During the above reaction process, appropriate stirring can be performed to improve the mixing uniformity of the curing agent and the electrolyte, which is conducive to a full reaction.

[0051] Furthermore, after the reaction is completed, the reaction system is cooled to 400° C. to 500° C., followed by solid-liquid separation.

[0052] It should be noted that the cooling temperature should not be lower than 400°C, otherwise the LiCl-KCl electrolyte will solidify or become viscous and cannot be effectively separated from the barium phosphate precipitate. In addition, by cooling, the barium phosphate can be further effectively precipitated during the cooling process. If the solid-liquid separation is performed directly without cooling, due to the high reaction temperature in the early stage, the reaction materials after the reaction have a high temperature themselves, which is easy to have an adverse effect on the filtration equipment.

[0053] After the cooling was completed, the upper layer of the reaction system was clear.

[0054] In some optional embodiments, the solid-liquid separation can be performed by filtration, which can exemplarily but not limitatively include any one of natural filtration, vacuum filtration and pressure filtration, preferably pressure filtration.

[0055] The electrolyte obtained by filtration can be recycled to the electrolytic cell for recycling.

[0056] The features and performance of the present invention are further described in detail below in conjunction with the embodiments.

[0057] Example 1

[0058] This embodiment provides a method for removing Ba from LiCl-KCl electrolyte. 2+ , Ca 2+ The method comprises the following steps: taking 6 kg of LiCl-KCl electrolyte to be treated (the Ba content is about 1 wt% and the Ca content is about 0.2 wt% according to ICP detection), heating it to 400°C and keeping it warm, and taking a sample as A1. Then adding 115.6 g of potassium sulfate (the actual amount of curing agent added is 90% of the theoretical amount) and stirring the reaction, the electrolyte melt changes from clear to milky white turbid; maintaining the temperature and keeping the reaction for 1 hour, after the end of the insulation, cooling the electrolyte to 450°C, and filtering the upper layer of the electrolyte until it is clear, to obtain the filter residue and the purified electrolyte, and the electrolyte sample at this time is recorded as A2.

[0059] Example 2

[0060] This embodiment provides a method for removing Ba from LiCl-KCl electrolyte. 2+ , Ca 2+ The method comprises the following steps: taking 6 kg of LiCl-KCl electrolyte to be treated (the Ba content is about 1 wt% and the Ca content is about 0.2 wt% according to ICP detection), heating it to 450°C and keeping it warm, and taking a sample as B1. Then adding 81.2 g of lithium sulfate (the actual amount of curing agent added is 100% of the theoretical amount of curing agent) and stirring the reaction, the electrolyte melt changes from clear to milky white turbid; maintaining the temperature and keeping the reaction for 2 hours, after the end of the insulation, cooling the electrolyte to 400°C, and filtering the upper layer of the electrolyte until it is clear, to obtain the filter residue and the purified electrolyte, and the electrolyte sample at this time is recorded as B2.

[0061] Example 3

[0062] This embodiment provides a method for removing Ba from LiCl-KCl electrolyte. 2+ , Ca 2+ The method comprises the following steps: taking 6 kg of LiCl-KCl electrolyte to be treated (the Ba content is about 1 wt% and the Ca content is about 0.2 wt% according to ICP detection), heating it to 500°C for insulation, and taking a sample as C1. Then adding 115.3 g of sodium sulfate (the actual amount of curing agent added is 110% of the theoretical amount) and stirring for reaction, the electrolyte melt changes from clear to milky white turbid; maintaining the temperature for insulation reaction for 3 hours, cooling the electrolyte to 500°C after the insulation is completed, filtering the upper layer of the electrolyte until it is clear, and obtaining the filter residue and the purified electrolyte, and the electrolyte sample at this time is recorded as C2.

[0063] Example 4

[0064] This embodiment provides a method for removing Ba from LiCl-KCl electrolyte. 2+ , Ca2+ The method comprises the following steps: taking 6 kg of LiCl-KCl electrolyte to be treated (ICP detection shows that the Ba content is about 1 wt% and the Ca content is about 0.2 wt%), heating it to 450°C and keeping it warm, and taking a sample as D1. Then add 122 g of potassium sulfate (the actual amount of curing agent added is 95% of the theoretical amount added) and stir to react, and the electrolyte melt changes from clear to milky white turbid. Then heat the electrolyte to 800°C and keep it warm for 4 hours. After the insulation is completed, cool the electrolyte to 450°C, wait until the upper layer of the electrolyte is clear, filter it, and obtain the filter residue and the purified electrolyte. The electrolyte sample at this time is recorded as D2.

[0065] Example 5

[0066] This embodiment provides a method for removing Ba from LiCl-KCl electrolyte. 2+ , Ca 2+ The method comprises the following steps: taking 6 kg of LiCl-KCl electrolyte to be treated (ICP detection shows that the Ba content is about 1 wt% and the Ca content is about 0.2 wt%), heating it to 450°C and keeping it warm, and taking a sample as E1. Then adding 85.2 g of lithium sulfate (the actual amount of curing agent added is 105% of the theoretical amount) and stirring the reaction, the electrolyte melt changes from clear to milky white turbid; then heating the electrolyte to 1000°C and keeping the temperature for 5 hours, after which the electrolyte is cooled to 450°C, and filtering the upper layer of the electrolyte until it is clear, to obtain the filter residue and the purified electrolyte, and the electrolyte sample at this time is recorded as E2.

[0067] Example 6

[0068] This embodiment provides a method for removing Ba from LiCl-KCl electrolyte. 2+ , Ca 2+ The method comprises the following steps: taking 6 kg of LiCl-KCl electrolyte to be treated (the Ba content is about 1 wt% and the Ca content is about 0.2 wt% according to ICP detection), heating it to 400°C and keeping it warm, and taking a sample as F1. Then adding 72.6 g of sodium phosphate (the actual amount of curing agent added is 90% of the theoretical amount) and stirring the reaction, the electrolyte melt changes from clear to milky white turbid; maintaining the temperature and keeping the reaction for 2 hours, after the end of the insulation, cooling the electrolyte to 450°C, and filtering the upper layer of the electrolyte until it is clear, to obtain the filter residue and the purified electrolyte, and the electrolyte sample at this time is recorded as F2.

[0069] Example 7

[0070] This embodiment provides a method for removing Ba from LiCl-KCl electrolyte. 2+ , Ca 2+The method comprises the following steps: taking 6 kg of LiCl-KCl electrolyte to be treated (the Ba content is about 1 wt% and the Ca content is about 0.2 wt% according to ICP detection), heating it to 450°C for insulation, and taking a sample as G1. Then adding 80.7 g of sodium phosphate (the actual amount of curing agent added is 100% of the theoretical amount of curing agent) and stirring for reaction, the electrolyte melt changes from clear to milky white turbid; maintaining the temperature for insulation reaction for 3 hours, cooling the electrolyte to 450°C after the insulation is completed, and filtering the electrolyte until the upper layer is clear to obtain filter residue and purified electrolyte, and the electrolyte sample at this time is recorded as G2.

[0071] Example 8

[0072] This embodiment provides a method for removing Ba from LiCl-KCl electrolyte. 2+ , Ca 2+ The method comprises the following steps: taking 6 kg of LiCl-KCl electrolyte to be treated (ICP detection shows that the Ba content is about 1 wt% and the Ca content is about 0.2 wt%), heating it to 500°C and keeping it warm, and taking a sample as H1. Then adding 88.8 g of sodium phosphate (the actual amount of curing agent added is 110% of the theoretical amount of curing agent) and stirring the reaction, the electrolyte melt changes from clear to milky white turbid; maintaining the temperature for 4 hours of insulation reaction, cooling the electrolyte to 450°C after the insulation is completed, and filtering the upper layer of the electrolyte to obtain filter residue and purified electrolyte, and the electrolyte sample at this time is recorded as H2.

[0073] Comparative Example 1

[0074] The difference between this comparative example and Example 3 is that the amount of curing agent added is 80% of the theoretical amount.

[0075] In this comparative example, the molten LiCl-KCl electrolyte sample to be treated is recorded as I1, and the barium-free electrolyte sample is recorded as I2.

[0076] Comparative Example 2

[0077] The difference between this comparative example and Example 3 is that the added dosage of the curing agent is 70% of the theoretical amount.

[0078] In this comparative example, the molten LiCl-KCl electrolyte sample to be treated is recorded as J1, and the barium-free electrolyte sample is recorded as J2.

[0079] Comparative Example 3

[0080] The difference between this comparative example and Example 3 is that the temperature is lowered to 300° C. after the reaction is completed, and the LiCl-KCl electrolyte solidifies.

[0081] Comparative Example 4

[0082] The difference between this comparative example and Example 7 is that the heat preservation reaction temperature after adding the curing agent is 800°C.

[0083] In this comparative example, the molten LiCl-KCl electrolyte sample to be treated is recorded as K1, and the barium-free electrolyte sample is recorded as K2.

[0084] Comparative Example 5

[0085] The difference between this comparative example and Example 3 is that the reaction is kept warm for 0.5 h after the curing agent is added.

[0086] In this comparative example, the molten LiCl-KCl electrolyte sample to be treated is recorded as L1, and the barium-free electrolyte sample is recorded as L2.

[0087] Test example

[0088] For the samples of each embodiment and comparative example, 2+ , Ca 2+ The content was analyzed and tested, and the results are shown in Table 1.

[0089] Table 1 Test results

[0090]

[0091] From Table 1 we can see that:

[0092] The method provided in this embodiment can effectively remove barium ions in the LiCl-KCl electrolyte to be treated. After impurities are removed, the barium ion content in the electrolyte is below 700 ppm, the calcium ion content is below 320 ppm, the barium ion removal rate is above 94%, and the calcium ion removal rate is above 85%, and the impurity removal effect is good.

[0093] In Comparative Example 1, the amount of curing agent used was reduced to 80% of the theoretical amount compared with Example 3, resulting in the barium removal rate of the electrolyte being reduced to 80.7%, the calcium removal rate being reduced to 76.7%, and the impurity removal effect being significantly reduced.

[0094] In Comparative Example 2, the amount of curing agent used was reduced to 70% of the theoretical amount compared with Example 3, resulting in the barium removal rate of the electrolyte being reduced to 67.3%, the calcium removal rate being reduced to 69.1%, and the impurity removal effect being significantly reduced.

[0095] Compared with Example 3, the cooling temperature of Comparative Example 3 after the insulation is completed is too low, resulting in the solidification of part of the electrolyte, which fails to meet the filtering requirements and cannot be carried out for subsequent operations.

[0096] Compared with Example 7, the insulation temperature of Comparative Example 4 was too high after the curing agent was added, and the reaction was incomplete, resulting in the barium removal rate of the electrolyte being reduced to 63.7%. The barium removal effect was significantly reduced, and the calcium removal effect was not significantly affected.

[0097] In Comparative Example 5, the heat preservation reaction time was reduced to 0.5 h compared with Example 3, and the reaction was incomplete, resulting in the barium removal rate of the electrolyte being reduced to 75.4%, the calcium removal rate being reduced to 70.5%, and the impurity removal effect being significantly reduced.

[0098] As mentioned above, 90% to 110% of the theoretical amount of curing agent is added to the LiCl-KCl electrolyte in a molten state, and the reaction is carried out at an appropriate temperature (the reaction temperature of the sulfate curing agent is 400°C to 1000°C, and the reaction temperature of the sodium phosphate curing agent is 400°C to 500°C) for 1h to 5h, and then the temperature is lowered to 400 to 500°C and filtered, which can ensure that the barium removal rate of the electrolyte is above 94% and the calcium removal rate is above 85%.

[0099] In summary, the method provided by the present invention has at least the following advantages:

[0100] (1) The present invention aims at enriching barium and calcium ions in the process of lithium metal electrolysis, and uses sulfate and phosphate to remove impurities, thereby achieving electrolyte purification;

[0101] (2) Compared with the conventional method of dissolving molten salt in water and then adding a precipitant to remove barium and calcium and recrystallize to obtain an electrolyte, the method provided by the present invention realizes solid-liquid phase transition through chemical reaction and then removes the barium and calcium salts converted into the solid phase through filtration. The method has a simpler processing flow, shorter time, lower processing cost, basically no wastewater and waste gas, etc. are generated, and is highly efficient and environmentally friendly;

[0102] (3) The method provided by the present invention can be directly processed in the original production equipment. The treated electrolyte can be directly used in production without adding additional processing equipment, and is suitable for industrial application.

[0103] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for removing Ba from LiCl-KCl electrolyte 2+ , Ca 2+ The method is characterized in that The following steps are involved: Contains Ba in the molten state 2+ , Ca 2+ A curing agent is added to the LiCl-KCl electrolyte containing one or two ions to react and generate a high melting point salt solid. The Ba contained in the solid-liquid separation is then removed. 2+ , Ca 2+ .

2. The method according to claim 1, characterized in that The actual amount of the curing agent added is 90% to 110% of the theoretical amount.

3. The method according to any one of claims 1 to 2, characterized in that: The curing agent includes at least one of potassium sulfate, lithium sulfate, sodium sulfate and sodium phosphate.

4. The method according to any one of claims 1 to 2, characterized in that: The curing agent is added to the LiCl-KCl electrolyte at a temperature of 400° C. to 500° C.

5. The method according to any one of claims 1 to 2, characterized in that: The reaction temperature of the LiCl-KCl electrolyte and the curing agent is not less than 400°C.

6. The method according to claim 5, characterized in that When the curing agent is at least one of potassium sulfate, lithium sulfate and sodium sulfate, the reaction temperature of the LiCl-KCl electrolyte and the curing agent is 400°C to 1000°C.

7. The method according to claim 5, characterized in that When the curing agent is sodium phosphate, the reaction temperature of the LiCl-KCl electrolyte and the curing agent is 400°C to 500°C.

8. The method according to claim 5, characterized in that The reaction time of the LiCl-KCl electrolyte and the curing agent is 1 h to 5 h.

9. The method according to claim 1, characterized in that: After the reaction is completed, the reaction system is cooled to 400°C to 500°C, followed by solid-liquid separation.

10. The method according to claim 1, characterized in that Solid-liquid separation is carried out by filtration; Preferably, the filtering method includes any one of natural filtration, vacuum filtration and pressure filtration.

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