Composite cleaning agent for cleaning residual solution of lithium battery electrolyte packaging container, and preparation method and cleaning method thereof

Abstract

The present application relates to a composite cleaning agent for cleaning lithium battery electrolyte packaging container residual liquid, a preparation method thereof and a method for cleaning the container residual liquid, the composite cleaning agent comprises linear carbonate, cyclic carbonate, low-boiling-point carboxylic acid ester, low alcohol and anhydrous acetylenic diol low-foam non-ionic wetting agent in percentage by mass, the total content of the cyclic carbonate and the low-boiling-point carboxylic acid ester is not less than 5.00%, no water is added in the cleaning agent, and the cleaning agent does not contain siloxane wetting agent, fluorine-containing surfactant and ionic surfactant, the advantages are that the risk of impurity residue is reduced, various electrolyte residual liquids can be treated at the same time, the cleaning effect and volatile control are considered, the cleaning agent can be filtered, supplemented and recycled.

Description

Technical Field

[0001] This invention relates to a composite cleaning agent for cleaning residual liquid in lithium battery electrolyte packaging containers, its preparation method, and a method for cleaning residual liquid in containers. Background Technology

[0002] Currently, lithium-ion battery electrolytes are typically stored and transported in stainless steel ton containers, 200kg packaging drums, or storage tanks. After the electrolyte is discharged, a certain amount of residue usually remains on the walls, bottom, valves, flanges, and inside the discharge pipe.

[0003] When the residual electrolyte contains a high amount of ethylene carbonate, the viscosity of the ethylene carbonate-rich areas tends to increase, with localized crystallization and decreased fluidity as the ambient temperature decreases. Ethylene carbonate may be solid below approximately 36.4°C; therefore, simply draining the electrolyte at room temperature is insufficient to completely remove residual liquid from the tank walls.

[0004] Currently, the cleaning methods for electrolyte packaging barrels mainly include the following: repeated rinsing with tap water or pure water; long-term drying with hot air, vacuum or nitrogen after water washing; rinsing once or multiple times with a single carbonate solvent such as dimethyl carbonate, ethyl methyl carbonate or diethyl carbonate; heating the packaging barrel with steam, hot water jacket or heat tracing pipe; and rinsing with a solvent similar to the electrolyte formula.

[0005] Existing technologies disclose methods that use tap water and distilled water for sequential washing, followed by prolonged nitrogen purging and drying. These methods consume a large amount of water and drying energy. Other technologies use low-boiling-point carbonates such as dimethyl carbonate, ethyl methyl carbonate, or diethyl carbonate for two or more cleaning cycles. However, these methods mainly rely on the dissolving and rinsing effects of the solvents themselves and do not solve the problem of insufficient wetting of the tank walls, valve dead zones, and highly viscous film during short-term cycles. Still other technologies propose heating the washing material and electrolyte storage tank and controlling the washing process through temperature and weighing feedback. However, the main innovations are focused on equipment and control methods, without designing specialized cleaning agents for different residual liquid compositions such as ethylene carbonate, propylene carbonate, and ethyl acetate. While directly using high-temperature steam can improve the fluidity of the residual liquid, it also introduces heat and moisture. For residual liquids containing lithium hexafluorophosphate, direct contact with moisture is not conducive to the classification and recycling of residual liquids and also increases the burden on subsequent fluoride-containing wastewater treatment and tank drying. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a composite cleaning agent for cleaning residual liquid in lithium battery electrolyte packaging containers, its preparation method, and a method for cleaning container residual liquid. This solution improves the ability to dynamically spread and clean dead corners in a short time by using a trace amount of acetylenol-based wetting agent; achieves wetting at a low addition amount, avoiding the generation of large amounts of foam by ordinary surfactants; does not use silicone oil-based, fluorine-containing, or ionic surfactants, reducing the risk of impurity residue; can simultaneously treat residual electrolytes of ethylene carbonate, propylene carbonate, dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, and ethyl acetate; achieves both cleaning effect and volatilization control through two-stage temperature control of ethylene carbonate for hot discharge and ethyl acetate for low-temperature cleaning; reduces the amount of fluorine-containing wastewater generated by direct water washing; the cleaning agent can be filtered, replenished, and recycled; after cleaning, a small amount of pure dimethyl carbonate or methyl ethyl carbonate can be used to complete the final rinsing; suitable for ton containers, 200kg containers, storage tanks, pipelines, and valves; and eliminates the need to add free solid powder directly into the container, reducing the risk of particle residue and clogging.

[0007] To achieve the above objectives, the first technical solution of the present invention is as follows: a composite cleaning agent for cleaning residual liquid in lithium battery electrolyte packaging containers, characterized in that, by mass percentage, it comprises: 40.00% to 80.00% linear carbonate, wherein the linear carbonate is selected from one or more of dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, methyl propyl carbonate, and ethyl propyl carbonate; 0-25.00% of cyclic carbonates, wherein the cyclic carbonates are selected from one or more of propylene carbonate, ethylene carbonate, and butene carbonate; 0-30.00% of low-boiling-point carboxylic acid esters, wherein the low-boiling-point carboxylic acid esters are selected from one or more of ethyl acetate, methyl acetate, propyl acetate, methyl propionate, and ethyl propionate. 0-8.00% of lower alcohols, wherein the lower alcohols are selected from one or more of ethanol, isopropanol, and n-propanol; and 0.005–0.200% anhydrous acetylenic diol-based low-foaming nonionic wetting agent; The total content of the cyclic carbonate and the low-boiling-point carboxylic acid ester is not less than 5.00%, water is not actively added to the cleaning agent, and the cleaning agent does not contain siloxane wetting agents, fluorinated surfactants, or ionic surfactants.

[0008] In this technical solution, the anhydrous acetylenol-based low-foaming nonionic wetting agent is selected from one or more of acetylenol compounds, acetylenol ethylene oxide adducts, acetylenol propylene oxide adducts, or acetylenol ethylene oxide-propylene oxide co-adducts; preferably, it is selected from one or more of 2,4,7,9-tetramethyl-5-decyn-4,7-diol, 4,7-dimethyl-5-decyn-4,7-diol, and the above-mentioned acetylenol ethylene oxide adducts or the above-mentioned acetylenol ethylene oxide-propylene oxide adducts; and the anhydrous acetylenol-based low-foaming nonionic wetting agent meets at least one of the following conditions: it does not use water as a product carrier; the mass content of the active ingredient is not less than 90%; the water content of the wetting agent itself is not higher than 0.50%; and it does not contain intentionally added anionic or cationic salts.

[0009] In this technical solution, the content of the anhydrous acetylenic diol-based low-foaming nonionic wetting agent is 0.020-0.080%, and the total water content in the cleaning agent is not higher than 0.10%.

[0010] In this technical solution, the linear carbonate is a compound system of dimethyl carbonate and methyl ethyl carbonate or diethyl carbonate; the cyclic carbonate is propylene carbonate; the low-boiling-point carboxylic acid ester is ethyl acetate; the lower alcohol is anhydrous ethanol; preferably, the composite cleaning agent is composed of the following components in mass percentage: dimethyl carbonate 49.95%, methyl ethyl carbonate 20.00%, propylene carbonate 10.00%, ethyl acetate 15.00%, anhydrous ethanol 5.00%, and anhydrous acetylenic diol-based low-foaming nonionic wetting agent 0.05%.

[0011] To achieve the above objectives, the second technical solution of the present invention is as follows: a composite cleaning agent for cleaning residual liquid in lithium battery electrolyte packaging containers, characterized in that, by mass percentage, it comprises: A method for preparing a composite cleaning agent for cleaning residual liquid in lithium battery electrolyte packaging containers, characterized by comprising the following steps: Step 1: Inspect the mixing tank, agitator, pipes, and valves to ensure there is no visible water inside the equipment; Step 2: Add linear carbonate to the mixing tank, add cyclic carbonate while stirring, and then add low-boiling-point carboxylic acid ester. Step 3: Add lower alcohols as needed. Dilute the anhydrous acetylenic diol-based low-foaming nonionic wetting agent with 5 to 20 times its mass of dimethyl carbonate or ethyl methyl carbonate, and then slowly add the diluted wetting agent to the mixing tank. Step 4: After adding to the mixing tank, stir for 10-30 minutes at 15-30°C; Step 5: After stirring, filter the mixture through a 1-10 μm organic solvent resistant filter to obtain the composite cleaning agent.

[0012] To achieve the above objectives, the third technical solution of the present invention is implemented as follows: a composite cleaning agent for cleaning residual liquid in lithium battery electrolyte packaging containers, characterized in that, by mass percentage, it comprises: A method for cleaning residual liquid in lithium battery electrolyte packaging containers using a composite cleaning agent, characterized by comprising the following steps: Step 1: Connect the packaging container to be cleaned to the residual liquid recovery system and drain the free-flowing residual liquid from the packaging container. Step 2: Select the temperature control program based on the composition of the residual electrolyte; Step 3: Add a compound cleaning agent to the packaging container, wherein the amount of the compound cleaning agent added is 1-8% of the volume of the packaging container; Step four: Make the composite cleaning agent come into contact with the inner surface of the packaging container and perform cyclic cleaning; Step 5: Discharge and recycle the composite cleaning agent; Optionally, when the electrolyte residue in the recycled cleaning agent reaches a set upper limit, add the recycled cleaning agent as the first coarse washing solution to the packaging container for the first round of circulating cleaning. After discharging the coarse washing solution, add fresh composite cleaning agent as the second fine washing solution for the second round of circulating cleaning. Discharge and recycle the fine washing solution; Optionally, use pure dimethyl carbonate or pure methyl ethyl carbonate for the final rinsing; and Step six: Purge the packaging container with nitrogen or vacuum dry it.

[0013] In this technical solution, the step of selecting the temperature control program based on the composition of the residual electrolyte includes one of the following: (1) When the mass content of ethylene carbonate in the residual electrolyte is not less than 10%, or when there is obvious crystallization, turbidity or high viscosity on the barrel wall, before adding the composite cleaning agent, indirectly heat the packaging container to 35-45°C and keep it warm for 3-15 minutes. Tilt the packaging container or use low-pressure nitrogen to help discharge the flowable residual liquid. Then stop heating, reduce the temperature of the packaging container to 10-30°C, and then add the composite cleaning agent for circulation cleaning. (2) When the residual electrolyte is mainly composed of propylene carbonate, dimethyl carbonate, ethyl methyl carbonate and diethyl carbonate and there is no obvious ethylene carbonate crystallization, the cleaning temperature is controlled at 15-30℃, and the packaging container is not preheated at high temperature. (3) When the mass content of ethyl acetate or other low-boiling-point carboxylic acid esters in the residual electrolyte is not less than 5%, the original residual liquid is discharged in a closed state, the temperature of the tank is controlled at 10-25℃, the composite cleaning agent is added under nitrogen protection and anti-static grounding conditions and closed-loop spraying is carried out, and steam or high-temperature hot air heating is not continued after the composite cleaning agent is added.

[0014] In this technical solution, the circulating cleaning method includes one or more of the following: rotating nozzle spraying, pump circulation, packaging barrel rolling, packaging barrel flipping, intermittent pulse spraying, and low-pressure nitrogen propelling the cleaning agent flow. The circulating cleaning time is 2 to 15 minutes.

[0015] In this technical solution, the recovery step of the composite cleaning agent includes: Step 1: The discharged composite cleaning agent is filtered through a 1-20μm filter, allowed to settle, passed through a detachable 3A molecular sieve purification tube, distilled at low temperature or under reduced pressure, replenished with solvent or wetting agent, and subjected to one or more of the following treatments: moisture content, density, and main solvent ratio, before being recycled. Step 2: When the electrolyte residue in the recycled cleaning agent reaches the set upper limit, the recycled cleaning agent is used as the first coarse cleaning solution, and the fresh compound cleaning agent is used as the second fine cleaning solution.

[0016] In this technical solution, the final rinse is performed using 0.5-3% of pure dimethyl carbonate or pure ethyl methyl carbonate in the packaging container volume.

[0017] The advantages of this invention compared to existing technologies are as follows: This solution improves short-time dynamic spreading and dead-angle cleaning capabilities through trace amounts of acetylenic diol wetting agents; it achieves wetting at lower addition levels, avoiding the generation of large amounts of foam from ordinary surfactants; it does not use silicone oil-based, fluorinated, or ionic surfactants, reducing the risk of impurity residue; it can simultaneously treat residual electrolytes of ethylene carbonate, propylene carbonate, dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, and ethyl acetate; it balances cleaning effectiveness and volatilization control through two-stage temperature control of ethylene carbonate for hot residual removal and ethyl acetate for low-temperature cleaning; it reduces the amount of fluoride-containing wastewater generated by direct water washing; the cleaning agent can be filtered, replenished, and recycled; a small amount of pure dimethyl carbonate or methyl ethyl carbonate can be used for the final rinsing after cleaning; it is suitable for ton containers, 200kg containers, storage tanks, pipelines, and valves; and it eliminates the need to directly add free solid powder into the container, reducing the risk of particle residue and clogging. Attached Figure Description

[0018] Figure 1 This is a flowchart of the method for cleaning residual liquid in a container according to the present invention; Figure 2 This is a flowchart illustrating the preparation of the cleaning agent according to the present invention; Figure 3 This is a schematic diagram of the structure of the present invention; Figure 4 This is a schematic diagram of the two-stage temperature control of the residual liquid in the EC type of the present invention; Figure 5 This is a schematic diagram of the mechanism by which the acetylenol wetting agent enhances the removal of wall-mounted liquid in this invention. Detailed Implementation

[0019] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings. It should be noted that these descriptions are for the purpose of aiding understanding the present invention, but do not constitute a limitation thereof. Furthermore, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other. Example

[0020] like Figures 1 to 5 The product shown is a composite cleaning agent for cleaning residual liquid in lithium battery electrolyte packaging containers, comprising, by mass percentage: 40.00% to 80.00% linear carbonate, wherein the linear carbonate is selected from one or more of dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, methyl propyl carbonate, and ethyl propyl carbonate; 0-25.00% of cyclic carbonates, wherein the cyclic carbonates are selected from one or more of propylene carbonate, ethylene carbonate, and butene carbonate; 0-30.00% of low-boiling-point carboxylic acid esters, wherein the low-boiling-point carboxylic acid esters are selected from one or more of ethyl acetate, methyl acetate, propyl acetate, methyl propionate, and ethyl propionate. 0-8.00% of lower alcohols, wherein the lower alcohols are selected from one or more of ethanol, isopropanol, and n-propanol; and 0.005–0.200% anhydrous acetylenic diol-based low-foaming nonionic wetting agent; The total content of the cyclic carbonate and the low-boiling-point carboxylic acid ester is not less than 5.00%, water is not actively added to the cleaning agent, and the cleaning agent does not contain siloxane wetting agents, fluorinated surfactants, or ionic surfactants.

[0021] When used, the composite cleaning agent protected by this scheme uses linear carbonate as the main solvent, supplemented by cyclic carbonate and low-boiling-point carboxylic acid esters to adjust the solubility and volatility, and adds a trace amount of anhydrous acetylenic diol low-foaming nonionic wetting agent to give it dynamic wetting ability. It is also specified that water should not be added actively, and it does not contain siloxane wetting agents, fluorinated surfactants and ionic surfactants. Its advantages are: (1) Linear carbonate, such as dimethyl carbonate, ethyl methyl carbonate and diethyl carbonate, have good solubility and dilution ability for carbonate solvents and LiPF6 in electrolyte, and have a moderate boiling point, making them easy to recover and recycle; (2) Cyclic carbonate, such as propylene carbonate, can improve the wetting of high viscosity, high content ethylene carbonate type wall residue; (3) Low-boiling-point carboxylic acid esters, such as ethyl acetate, help dissolve certain additives in the electrolyte and regulate the overall evaporation rate; (4) Anhydrous acetylenic diol wetting agents can significantly reduce the dynamic surface tension of organic solvents at extremely low addition amounts, i.e., 0.005 to 0.200%, accelerating the spreading and penetration speed of cleaning agents on barrel walls, valves, flanges and structural dead corners, while having extremely low foaming properties, and will not generate a large amount of foam during circulating spraying, affecting operation; (5) The formulation does not actively add water, avoiding the risk of HF generation from LiPF6 hydrolysis, and also eliminating the large amount of drying energy required for subsequent water washing processes; (6) It does not contain siloxanes, fluorinated and ionic surfactants, avoiding the introduction of residual sensitive impurities in the electrolyte supply chain.

[0022] In this embodiment, the anhydrous acetylenol-based low-foaming nonionic wetting agent is selected from one or more of acetylenol compounds, acetylenol ethylene oxide adducts, acetylenol propylene oxide adducts, or acetylenol ethylene oxide-propylene oxide co-adducts; preferably, it is selected from one or more of 2,4,7,9-tetramethyl-5-decyn-4,7-diol, 4,7-dimethyl-5-decyn-4,7-diol, and the above-mentioned acetylenol ethylene oxide adducts or the above-mentioned acetylenol ethylene oxide-propylene oxide adducts; and the anhydrous acetylenol-based low-foaming nonionic wetting agent meets at least one of the following conditions: it does not use water as a product carrier; the mass content of the active ingredient is not less than 90%; the water content of the wetting agent itself is not higher than 0.50%; and it does not contain intentionally added anionic or cationic salts. This embodiment further defines the specific chemical type, preferred varieties, and anhydrous use conditions of anhydrous acetylenol-based low-foaming nonionic wetting agents; the advantages are: (1) acetylenol and its ethylene oxide / propylene oxide adducts have a unique "gemini" molecular structure, which can exhibit excellent dynamic surface tension reduction ability in organic solvents, and are far superior to traditional nonionic or anionic wetting agents under short-time cyclic cleaning conditions; (2) Preferred varieties such as 2,4,7,9-tetramethyl-5-decyn-4,7-diol and 4,7-dimethyl-5-decyn-4,7-diol have good solubility in dimethyl carbonate and ethyl methyl carbonate, and can be used directly in solid or high-concentration form; (3) The wetting agent itself has an effective component of ≥90%, water content ≤0.50%, does not use water as a carrier, and does not contain intentionally added anionic or cationic salts, ensuring that the introduction of the wetting agent itself will not become a new source of water or ion pollution, and has good compatibility with polyfluorinated electrolyte systems.

[0023] In this embodiment, the content of the anhydrous acetylenol-based low-foaming nonionic wetting agent is 0.020-0.080%, and the total water content in the cleaning agent is not higher than 0.10%. This embodiment limits the preferred content range of the wetting agent and the upper limit of the total water content of the cleaning agent; the advantages are: (1) The content range of 0.020-0.080% is determined based on the actual cleaning test results. When it is lower than 0.020%, the dynamic wetting improvement effect is not obvious, and when it is higher than 0.080%, the wetting effect tends to saturate and the cost increases; (2) The total water content is controlled below 0.10%, which can effectively inhibit the hydrolysis of residual LiPF6 to generate HF during the cleaning process, protect the inner wall of the packaging container, valves and subsequent operators, and reduce the drying burden of residual water in the bucket after cleaning.

[0024] In this embodiment, the linear carbonate is a compound system of dimethyl carbonate and methyl ethyl carbonate or diethyl carbonate; the cyclic carbonate is propylene carbonate; the low-boiling-point carboxylic acid ester is ethyl acetate; and the lower alcohol is anhydrous ethanol. Preferably, the composite cleaning agent is composed of the following components in mass percentage: 49.95% dimethyl carbonate, 20.00% methyl ethyl carbonate, 10.00% propylene carbonate, 15.00% ethyl acetate, 5.00% anhydrous ethanol, and 0.05% anhydrous acetylene diol-based low-foaming nonionic wetting agent. In this embodiment, the linear carbonate is a DMC / EMC or DMC / DEC compound system, the cyclic carbonate is propylene carbonate, the low-boiling-point carboxylic acid ester is ethyl acetate, and the lower alcohol is anhydrous ethanol, and a specific optimal formulation is provided. The advantages are: (1) The DMC / EMC compound combines the high solubility and low viscosity of DMC with the moderate boiling point and low volatility loss of EMC, and the two work together to provide an ideal solvent base; (2) The addition of propylene carbonate helps to dissolve viscous wall-mounted substances with high EC content, reducing the energy consumption of softening by heating alone; (3) Ethyl acetate can effectively dissolve low polarity additives such as vinylene carbonate and FEC in the electrolyte, reducing the risk of cross-contamination caused by their individual residues; (4) Anhydrous ethanol adjusts the overall polarity of the cleaning agent and assists the wetting agent to adsorb at the gas-liquid and liquid-solid interfaces; (5) The specific formula disclosed provides directly replicable examples, which are convenient for industry implementation. Example

[0025] like Figures 1 to 5 As shown, this is a method for preparing a composite cleaning agent for cleaning residual liquid in lithium battery electrolyte packaging containers, comprising the following steps: Step 1: Inspect the mixing tank, agitator, pipes, and valves to ensure there is no visible water inside the equipment; Step 2: Add linear carbonate to the mixing tank, add cyclic carbonate while stirring, and then add low-boiling-point carboxylic acid ester. Step 3: Add lower alcohols as needed. Dilute the anhydrous acetylenic diol-based low-foaming nonionic wetting agent with 5 to 20 times its mass of dimethyl carbonate or ethyl methyl carbonate, and then slowly add the diluted wetting agent to the mixing tank. Step 4: After adding to the mixing tank, stir for 10-30 minutes at 15-30°C; Step 5: After stirring, filter the mixture through a 1-10 μm organic solvent resistant filter to obtain the composite cleaning agent.

[0026] This embodiment protects the preparation process of the composite cleaning agent. The advantages are: (1) First check that there is no obvious moisture inside the equipment, and control the water content of the finished cleaning agent from the source; (2) The feeding sequence of "first add the main solvent, then add the auxiliary solvent and finally add the pre-diluted wetting agent" is adopted to ensure that the wetting agent is evenly dispersed in the insoluble solvent system, and avoid local high concentration leading to turbidity or precipitation of insoluble matter; (3) Pre-dilution of the wetting agent is a key technical detail. The pure product of acetylenol wetting agent is a low melting point solid or a high viscosity liquid. Direct addition in large quantities may dissolve slowly. Adding it after pre-dilution can significantly shorten the homogenization time and improve batch consistency; (4) Low temperature stirring at 15-30℃ avoids the volatilization loss of low boiling point components and the risk of organic vapor accumulation; (5) Finally, mechanical impurities and undissolved particles are removed by 1-10μm filtration to ensure that the cleaning agent does not clog the nozzle during spray cleaning. Example

[0027] like Figures 1 to 5 As shown, this is a method for cleaning residual liquid in lithium battery electrolyte packaging containers using a composite cleaning agent, characterized by the following steps: Step 1: Connect the packaging container to be cleaned to the residual liquid recovery system and drain the free-flowing residual liquid from the packaging container. Step 2: Select the temperature control program based on the composition of the residual electrolyte; Step 3: Add a compound cleaning agent to the packaging container, wherein the amount of the compound cleaning agent added is 1-8% of the volume of the packaging container; Step four: Make the composite cleaning agent come into contact with the inner surface of the packaging container and perform cyclic cleaning; Step 5: Discharge and recycle the composite cleaning agent; Optionally, when the electrolyte residue in the recycled cleaning agent reaches a set upper limit, add the recycled cleaning agent as the first coarse washing solution to the packaging container for the first round of circulating cleaning. After discharging the coarse washing solution, add fresh composite cleaning agent as the second fine washing solution for the second round of circulating cleaning. Discharge and recycle the fine washing solution; Optionally, use pure dimethyl carbonate or pure methyl ethyl carbonate for the final rinsing; and Step six: Purge the packaging container with nitrogen or vacuum dry it.

[0028] This embodiment protects the temperature-controlled circulating cleaning method for lithium battery electrolyte packaging containers. The advantages are: (1) First, the residual liquid is connected to the residual liquid recovery system to discharge the flowable residual liquid, and then the cleaning agent is injected, which significantly reduces the consumption of cleaning agent. The cleaning agent only needs to treat the residual liquid on the wall instead of the whole barrel of residual liquid, and the amount used is only 1 to 8% of the volume; (2) "Selecting the temperature control program according to the composition of the residual electrolyte" links the cleaning method with the chemical characteristics of the residual liquid, avoiding the problem of low cleaning efficiency when a single temperature scheme is used to treat EC-enriched or EA-enriched residual liquid; (3) Circulating cleaning allows the cleaning agent to repeatedly impact and wet the barrel wall, giving full play to the dynamic wetting advantage of the acetylsene diol wetting agent; (4) Discharging and recycling the cleaning agent reflects the economic benefits of recycling; (5) The final rinse further reduces the residue, and nitrogen purging or vacuum drying replaces water washing and long-term baking, reducing drying energy consumption and time costs.

[0029] In this embodiment, the step of selecting the temperature control program based on the composition of the residual electrolyte includes one of the following: (1) When the mass content of ethylene carbonate in the residual electrolyte is not less than 10%, or when there is obvious crystallization, turbidity or high viscosity on the barrel wall, before adding the composite cleaning agent, indirectly heat the packaging container to 35-45°C and keep it warm for 3-15 minutes. Tilt the packaging container or use low-pressure nitrogen to help discharge the flowable residual liquid. Then stop heating, reduce the temperature of the packaging container to 10-30°C, and then add the composite cleaning agent for circulation cleaning. (2) When the residual electrolyte is mainly composed of propylene carbonate, dimethyl carbonate, ethyl methyl carbonate and diethyl carbonate and there is no obvious ethylene carbonate crystallization, the cleaning temperature is controlled at 15-30℃, and the packaging container is not preheated at high temperature. (3) When the mass content of ethyl acetate or other low-boiling-point carboxylic acid esters in the residual electrolyte is not less than 5%, the original residual liquid is discharged in a closed state, the temperature of the tank is controlled at 10-25℃, the composite cleaning agent is added under nitrogen protection and anti-static grounding conditions and closed-loop spraying is carried out, and steam or high-temperature hot air heating is not continued after the composite cleaning agent is added.

[0030] This embodiment clearly defines three typical scenarios for "selecting the temperature control program based on the composition of the residual electrolyte". The advantages are: (1) For EC-enriched residual liquid, first heat to 35-45℃ to convert EC from solid or high viscosity to liquid, keep warm for 3-15 minutes to fully soften the wall material, tilt or nitrogen-assisted drainage, and then cool down to 10-30℃ to add cleaning agent. This not only improves the drainage efficiency of EC residual liquid, but also avoids the violent volatilization and safety hazards caused by injecting low boiling point solvent at high temperature; (2) For residual liquid without EC crystallization, mainly PC, DMC, EMC and DEC, directly control the cleaning at room temperature of 15-30℃. The operation is simple and the energy consumption is the lowest; (3) For residual liquid containing ≥5% ethyl acetate or other low boiling point carboxylic esters, the whole process is operated under closed conditions of 10-25℃, with nitrogen protection and anti-static grounding. No additional heating is required to control the volatilization of low boiling point components and the risk of organic vapor accumulation, taking into account both safety and cleaning effect. The three situations cover the most common residual liquid types in electrolyte production, making the cleaning method universal.

[0031] In this embodiment, the circulating cleaning method includes one or more of the following: rotating nozzle spraying, pump circulation, packaging barrel rolling, packaging barrel flipping, intermittent pulse spraying, and low-pressure nitrogen propelling the cleaning agent flow. The circulating cleaning time is 2 to 15 minutes.

[0032] This embodiment defines the specific method and time of the circulating cleaning. The advantages are: (1) It provides a variety of cleaning methods such as rotating nozzle spraying, pump circulation, packaging barrel rolling, flipping, intermittent pulse spraying and low-pressure nitrogen driving the cleaning agent flow, which can be flexibly selected or combined according to the container type; (2) Rotating nozzle spraying combined with pump circulation can cover the top wall and top corner of the barrel, packaging barrel rolling or flipping uses gravity to assist the cleaning agent to hang on the wall and descend, intermittent pulse spraying generates shock waves to break through the liquid stagnation film in dead corners, and low-pressure nitrogen driving can effectively discharge the accumulated liquid at the pipe bend; (3) The cleaning time is controlled between 2 and 15 minutes, which can ensure sufficient wetting and dissolution time in industrial continuous operation without affecting the cycle time and capacity of the cleaning line.

[0033] In this embodiment, the recovery step of the composite cleaning agent includes: Step 1: The discharged composite cleaning agent is filtered through a 1-20μm filter, allowed to settle, passed through a detachable 3A molecular sieve purification tube, distilled at low temperature or under reduced pressure, replenished with solvent or wetting agent, and subjected to one or more of the following treatments: moisture content, density, and main solvent ratio, before being recycled. Step two: When the residual electrolyte in the recycled cleaning agent reaches a set upper limit, the recycled cleaning agent is used as the first coarse cleaning solution, and the fresh composite cleaning agent is used as the second fine cleaning solution. This embodiment defines the recycling and purification treatment of the composite cleaning agent and its two-stage, graded use strategy. Advantages: (1) The recycling process includes multiple optional methods such as filtration, static sedimentation, 3A molecular sieve dehydration and purification, low temperature or vacuum distillation, addition of solvent or wetting agent, and quality inspection, forming a complete cleaning agent recycling scheme; (2) 3A molecular sieve can effectively adsorb the trace amount of water accumulated in the cleaning agent due to multiple cycles without adsorbing solvent molecules, and low temperature or vacuum distillation can remove the accumulated high boiling point electrolyte components; (3) When the electrolyte residue in the recycled cleaning agent reaches the set upper limit for recycling, it is not directly scrapped, but downgraded and used as the first rough washing liquid. The rough washing liquid first cleans the next batch of containers in the first round, roughly removing most of the wall residue, and then uses fresh composite cleaning agent for the second round of fine washing. This two-stage mode of rough washing plus fine washing greatly extends the overall service life of the cleaning agent, reduces the consumption of fresh solvent and wetting agent, reduces the discharge of waste organic solvent, and takes into account both economic and environmental benefits.

[0034] In this embodiment, the final rinse uses 0.5–3% of pure dimethyl carbonate or pure ethyl methyl carbonate by volume of the packaging container. This embodiment specifies that the final rinse uses 0.5–3% of pure DMC or pure EMC by volume of the packaging container. The advantages are: the purpose of the final rinse is to displace the trace amounts of wetting agent-containing cleaning agent remaining on the container wall; a dosage of 0.5–3% is sufficient to accomplish this task without wasting pure solvent; the rinse solution can be collected separately and used as a replenishing solvent for the next batch of cleaning agent, reflecting refined management of chemical resources.

[0035] When cleaning a general-purpose ton container, use a general-purpose composite cleaning agent containing 49.95% dimethyl carbonate, 20.00% methyl ethyl carbonate, 10.00% propylene carbonate, 15.00% ethyl acetate, 5.00% anhydrous ethanol, and 0.05% anhydrous acetylenic diol low-foaming nonionic wetting agent.

[0036] The cleaning steps are as follows: Connect the 1000L electrolyte container to the sealed residual liquid recovery pipe; use low-pressure nitrogen to discharge the flowable residual liquid; control the container temperature at 20-25℃, add 30kg of compound cleaning agent, and circulate and spray for 5 minutes using a rotating nozzle; discharge the cleaning agent and send it to the recovery tank, add 10-15kg of pure dimethyl carbonate to the container and rinse for 2 minutes, then discharge the dimethyl carbonate; purge with dry nitrogen and test for moisture, volatile residues, and particles inside the container.

[0037] When cleaning EC-enriched tonnes, use an EC-enriched residual liquid composite cleaning agent: 44.95% dimethyl carbonate, 15.00% methyl ethyl carbonate, 15.00% propylene carbonate, 15.00% ethyl acetate, 10.00% anhydrous ethanol, and 0.05% anhydrous acetylenic diol low-foaming nonionic wetting agent.

[0038] The cleaning steps are as follows: Without adding cleaning agent, indirectly heat the tank wall to 40℃; Maintain for 8 minutes; tilt the container and use nitrogen to assist in draining; stop heating and cool the container to below 25°C; add 35 kg of cleaning agent; circulate and spray for 5 minutes; drain the cleaning agent; rinse with 15 kg of pure dimethyl carbonate; purge and dry with nitrogen.

[0039] When cleaning PC ethyl acetate low-temperature electrolyte tanks, use a PC ethyl acetate low-temperature electrolyte composite cleaning agent: 54.95% dimethyl carbonate, 20.00% methyl ethyl carbonate, 5.00% propylene carbonate, 20.00% ethyl acetate, 0% anhydrous ethanol, and 0.05% anhydrous acetylene diol low-foaming nonionic wetting agent.

[0040] The cleaning steps are as follows: drain the original residual liquid in a sealed container at 15-20℃; do not steam heat the packaging barrel; add 30kg of cleaning agent; circulate and spray for 4 minutes under nitrogen protection; drain the cleaning agent; rinse with 10kg of methyl ethyl carbonate; drain the rinsing solution and purge with nitrogen.

[0041] When cleaning 200kg packaging drums, choose one of the three cleaning agents mentioned above based on the composition of the residual liquid.

[0042] The cleaning steps are as follows: Add 6 kg of compound cleaning agent; roll or circulate in a closed system for 4 minutes; drain the cleaning agent; add 2 kg of dimethyl carbonate for rinsing; roll for 1-2 minutes; drain the liquid and purge with nitrogen. The embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited to the described embodiments. For those skilled in the art, various changes, modifications, substitutions, and variations of these embodiments without departing from the principles and spirit of the present invention still fall within the protection scope of the present invention.

Claims

1. A composite cleaning agent for cleaning residual liquid in lithium battery electrolyte packaging containers, characterized in that, By weight percentage, including: 40.00% to 80.00% linear carbonate, wherein the linear carbonate is selected from one or more of dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, methyl propyl carbonate, and ethyl propyl carbonate; 0-25.00% of cyclic carbonates, wherein the cyclic carbonates are selected from one or more of propylene carbonate, ethylene carbonate, and butene carbonate; 0-30.00% of low-boiling-point carboxylic acid esters, wherein the low-boiling-point carboxylic acid esters are selected from one or more of ethyl acetate, methyl acetate, propyl acetate, methyl propionate, and ethyl propionate. 0-8.00% of lower alcohols, wherein the lower alcohols are selected from one or more of ethanol, isopropanol, and n-propanol; and 0.005–0.200% anhydrous acetylenic diol-based low-foaming nonionic wetting agent; The total content of the cyclic carbonate and the low-boiling-point carboxylic acid ester is not less than 5.00%, water is not actively added to the cleaning agent, and the cleaning agent does not contain siloxane wetting agents, fluorinated surfactants, or ionic surfactants.

2. The composite cleaning agent for cleaning residual liquid in lithium battery electrolyte packaging containers according to claim 1, characterized in that... The anhydrous acetylenol-based low-foaming nonionic wetting agent is selected from one or more of acetylenol compounds, acetylenol ethylene oxide adducts, acetylenol propylene oxide adducts, or acetylenol ethylene oxide-propylene oxide co-adducts; preferably, it is selected from one or more of 2,4,7,9-tetramethyl-5-decyn-4,7-diol, 4,7-dimethyl-5-decyn-4,7-diol, and the above-mentioned acetylenol ethylene oxide adducts or the above-mentioned acetylenol ethylene oxide-propylene oxide adducts; and the anhydrous acetylenol-based low-foaming nonionic wetting agent meets at least one of the following conditions: it does not use water as a product carrier; the mass content of the active ingredient is not less than 90%; the water content of the wetting agent itself is not higher than 0.50%; and it does not contain intentionally added anionic or cationic salts.

3. The composite cleaning agent for cleaning residual liquid in lithium battery electrolyte packaging containers according to claim 1, characterized in that... The content of the anhydrous acetylenic diol-based low-foaming nonionic wetting agent is 0.020-0.080%, and the total water content in the cleaning agent is not higher than 0.10%.

4. The composite cleaning agent for cleaning residual liquid in lithium battery electrolyte packaging containers according to claim 1, characterized in that... The linear carbonate is a compound system of dimethyl carbonate and methyl ethyl carbonate or diethyl carbonate; the cyclic carbonate is propylene carbonate; the low-boiling-point carboxylic acid ester is ethyl acetate; the lower alcohol is anhydrous ethanol; preferably, the composite cleaning agent is composed of the following components in mass percentage: 49.95% dimethyl carbonate, 20.00% methyl ethyl carbonate, 10.00% propylene carbonate, 15.00% ethyl acetate, 5.00% anhydrous ethanol, and 0.05% anhydrous acetylenic diol-based low-foaming nonionic wetting agent.

5. The method for preparing the composite cleaning agent for cleaning residual liquid in lithium battery electrolyte packaging containers according to claims 1 to 4, characterized in that... Includes the following steps: Step 1: Inspect the mixing tank, agitator, pipes, and valves to ensure there is no obvious water inside the equipment; Step 2: Add linear carbonate to the mixing tank, add cyclic carbonate while stirring, and then add low-boiling-point carboxylic acid ester. Step 3: Add lower alcohols as needed. Dilute the anhydrous acetylenic diol-based low-foaming nonionic wetting agent with 5 to 20 times its mass of dimethyl carbonate or ethyl methyl carbonate, and then slowly add the diluted wetting agent to the mixing tank. Step 4: After adding to the mixing tank, stir for 10-30 minutes at 15-30℃; Step 5: After stirring, filter the mixture through a 1-10 μm organic solvent resistant filter to obtain the composite cleaning agent.

6. The method for cleaning residual liquid in lithium battery electrolyte packaging containers using a composite cleaning agent according to claims 1 to 4, characterized in that... Includes the following steps: Step 1: Connect the packaging container to be cleaned to the residual liquid recovery system and drain the free-flowing residual liquid from the packaging container. Step 2: Select the temperature control program based on the composition of the residual electrolyte; Step 3: Add a compound cleaning agent to the packaging container, wherein the amount of the compound cleaning agent added is 1-8% of the volume of the packaging container; Step four: Make the composite cleaning agent come into contact with the inner surface of the packaging container and perform cyclic cleaning; Step 5: Discharge and recycle the composite cleaning agent; Optionally, when the electrolyte residue in the recycled cleaning agent reaches a set upper limit, add the recycled cleaning agent as the first coarse washing solution to the packaging container for the first round of circulating cleaning. After discharging the coarse washing solution, add fresh composite cleaning agent as the second fine washing solution for the second round of circulating cleaning. Discharge and recycle the fine washing solution; Optionally, use pure dimethyl carbonate or pure methyl ethyl carbonate for the final rinsing; and Step six: Purge the packaging container with nitrogen or vacuum dry it.

7. The method for cleaning residual liquid in lithium battery electrolyte packaging containers using the composite cleaning agent according to claim 6, characterized in that... The step of selecting the temperature control program based on the composition of the residual electrolyte includes one of the following: (1) When the mass content of ethylene carbonate in the residual electrolyte is not less than 10%, or when there is obvious crystallization, turbidity or high viscosity on the barrel wall, before adding the composite cleaning agent, indirectly heat the packaging container to 35-45°C and keep it warm for 3-15 minutes. Tilt the packaging container or use low-pressure nitrogen to help discharge the flowable residual liquid. Then stop heating, reduce the temperature of the packaging container to 10-30°C, and then add the composite cleaning agent for circulation cleaning. (2) When the residual electrolyte is mainly composed of propylene carbonate, dimethyl carbonate, ethyl methyl carbonate and diethyl carbonate and there is no obvious ethylene carbonate crystallization, the cleaning temperature is controlled at 15-30℃, and the packaging container is not preheated at high temperature. (3) When the mass content of ethyl acetate or other low-boiling-point carboxylic acid esters in the residual electrolyte is not less than 5%, the original residual liquid is discharged in a closed state, the temperature of the tank is controlled at 10-25℃, the composite cleaning agent is added under nitrogen protection and anti-static grounding conditions and closed-loop spraying is carried out, and steam or high-temperature hot air heating is not continued after the composite cleaning agent is added.

8. The method for cleaning residual liquid in lithium battery electrolyte packaging containers using the composite cleaning agent according to claim 6, characterized in that... The circulating cleaning method includes one or more of the following: rotating nozzle spraying, pump circulation, packaging barrel rolling, packaging barrel flipping, intermittent pulse spraying, and low-pressure nitrogen propelling the cleaning agent flow. The circulating cleaning time is 2 to 15 minutes.

9. The method for cleaning residual liquid in a lithium battery electrolyte packaging container using a composite cleaning agent according to claim 6, characterized in that... The recovery steps of the composite cleaning agent include: Step 1: The discharged composite cleaning agent is filtered through a 1-20μm filter, allowed to settle, passed through a detachable 3A molecular sieve purification tube, distilled at low temperature or under reduced pressure, replenished with solvent or wetting agent, and subjected to one or more of the following treatments: moisture content, density, and main solvent ratio, before being recycled. Step 2: When the electrolyte residue in the recycled cleaning agent reaches the set upper limit, the recycled cleaning agent is used as the first coarse cleaning solution, and the fresh compound cleaning agent is used as the second fine cleaning solution.

10. The method for cleaning residual liquid in a lithium battery electrolyte packaging container using a composite cleaning agent according to claim 6, characterized in that... The final rinse is performed using 0.5–3% of pure dimethyl carbonate or pure ethyl methyl carbonate by volume of the packaging container.

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