Preparation of organic lithium compound composite supported activator material and application thereof in electrolyte refining

Abstract

The application discloses a preparation method of an organic lithium compound composite loaded active agent material and application thereof in electrolyte refining. A carrier material is activated at a high temperature of 200 DEG C to 850 DEG C before use, and then is uniformly mixed with an organic lithium compound in a reaction bottle to obtain an organic lithium compound loaded composite active agent material. The multifunctional organic lithium compound loaded composite active agent material is contacted with a deteriorated electrolyte at room temperature, so that the chroma, acidity and moisture of the deteriorated electrolyte are greatly reduced, and the electrochemical stability and cycle life of the battery electrolyte and other electrochemical performances are further improved. The organic lithium compound loaded composite active agent material can also be applied to non-aqueous organic electrolyte production, color change regeneration application after long-time storage of commercial electrolyte, liquid LiPF6 lithium salt product production and the like.

Description

Technical fields:

[0001] This invention relates to the preparation of organolithium compound composite supported activator materials and their application in electrolyte purification. Background technology:

[0002] Lithium-ion batteries are widely used in mobile phones, portable devices, electric bicycles, electric vehicles, and energy storage due to their high specific energy, low self-discharge, lack of memory effect, and long cycle life. Currently, the electrolyte used in lithium-ion batteries is mainly composed of lithium salts and organic solvents. The chemical stability of the lithium-ion battery electrolyte is crucial to the battery's energy density, cycle life, and other electrochemical and safety performance.

[0003] In the preparation of lithium-ion battery electrolytes, if lithium salts are added too quickly, the electrolyte system can overheat locally. Thermal decomposition of the lithium salts produces PF5, which reacts with the electrolyte solvent, resulting in increased electrolyte color. Furthermore, ethylene oxide residues are easily left over from the production of ethylene carbonate. Ethylene oxide can accept hydrogen ions from strong acids to form molten salts, leading to increased electrolyte color during storage. Trace amounts of water, unavoidable in the external environment, can also cause lithium hexafluorophosphate to hydrolyze, producing acidic substances such as HF. HF acid corrodes the protective film at the electrode interface, damages the electrode material structure, and accelerates the dissolution of transition metals in the electrode material, resulting in capacity loss and reduced battery cycle life. National standards require that the free acid content of lithium-ion electrolytes be controlled below 30 ppm, color below 50 halons, and moisture below 10 ppm. When these technical indicators—free acid, color, and moisture—exceed the national standard requirements, they all have varying degrees of impact on battery capacity and cycle performance.

[0004] CN100539293C obtains a refined electrolyte by contacting and separating decolorizing agents such as silica gel, molecular sieves, and ion exchange resins with the deteriorated electrolyte, which reduces the color and moisture content of the electrolyte to some extent. CN1339845A removes acid and water by adding deacidifying agents (metal oxides such as magnesium, aluminum, barium, and calcium) and dehydrating agents (activated alumina, molecular sieve calcium sulfate, etc.) to the electrolyte for physical adsorption, which also reduces the free acid and water in the electrolyte to some extent, but has no significant effect on reducing the color of the electrolyte.

[0005] Therefore, researching and developing multifunctional decolorizing agents to simultaneously reduce the color, acid value, and moisture content of deteriorated electrolytes is a long-term and urgent technical need for improving the electrochemical stability of battery electrolytes and meeting and improving the application of electrochemical energy storage devices such as lithium-ion batteries. Summary of the Invention:

[0006] The purpose of this invention is to provide a method for preparing organolithium compound supported activator materials and their application in electrolyte purification.

[0007] This invention is achieved through the following technical solutions:

[0008] The preparation method of organolithium compound composite supported activator material includes the following steps: activating the carrier material at a high temperature of 200℃-850℃ before use, and then uniformly mixing it with the organolithium compound in a reaction flask to obtain the organolithium compound supported composite activator material.

[0009] The amount of the organolithium compound used is 0.1%-25% of the mass of the carrier material.

[0010] The organolithium compound is selected from any one of lithium bis(trimethylsilylamine) (LiHMDS), lithium diisopropylamine (LDA), and lithium 2,2,6,6-tetramethylpiperidine; preferably lithium bis(trimethylsilylamine); the support material is a commercially available support material with high specific surface area, including molecular sieves, activated carbon, alumina, silica gel, etc., preferably one or more of 4A molecular sieves and activated carbon.

[0011] When the carrier is 4A molecular sieve, the preparation of organic lithium compound supported activator material also includes the following steps: vacuuming, heating to 90-110℃ and holding for 10 min, then stopping heating and allowing it to cool to room temperature.

[0012] When the carrier is activated carbon, the preparation of the organic lithium compound supported activator material also involves adding a reaction solvent for mixing, and then removing the solvent by vacuuming with an oil pump.

[0013] This invention also protects the application of the aforementioned organolithium compound composite supported activator material in electrolyte purification, applied to the decolorization, deacidification, and dehydration of non-aqueous organic electrolytes, including non-aqueous organic electrolyte production processes, color-changing regeneration applications of commercial electrolytes after long-term storage, and production of liquid LiPF6 lithium salt products, including the following steps: adding the organolithium compound activator material directly to the electrolyte at room temperature, with a dosage of 1-13 kg / 50 liters of color-changing electrolyte, and then filtering to obtain the purified electrolyte product;

[0014] Alternatively, the color-changing electrolyte can be passed through a chromatography column packed with an organolithium composite activator material, at a dosage of 1-13 kg / 50 liters of color-changing electrolyte, to obtain a purified electrolyte product.

[0015] The non-aqueous organic electrolyte is an electrolyte containing a metal salt and an organic solvent; the organic solvent is one or more of dimethyl carbonate, ethylene carbonate, methyl ethyl carbonate, diethyl carbonate, and propylene carbonate; the metal salt is one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium difluorooxalate borate, lithium bis(oxalate borate), lithium bis(trifluoromethanesulfonyl)imide, and lithium bis(fluorosulfonyl)imide, or one or more corresponding sodium metal salts.

[0016] The non-aqueous organic electrolyte is used in electrochemical energy storage devices such as lithium-ion batteries and sodium-ion batteries.

[0017] The positive electrode material of a lithium-ion battery can be one or more of the following: ternary positive electrode, lithium iron phosphate, lithium cobalt oxide, nickel cobalt aluminum, and lithium manganese oxide. The negative electrode material of a lithium-ion battery can be one of the following: metallic lithium, graphite, lithium titanate, or silicon-based system.

[0018] The beneficial effects of this invention are as follows: The preparation method of this invention is simple. The resulting multifunctional organolithium-based supported composite activator material, when contacted with the deteriorated electrolyte at room temperature, significantly reduces the color, acidity, and moisture content of the deteriorated electrolyte, further improving the electrochemical stability and cycle life of the battery electrolyte. The organolithium-based supported composite activator material can also be applied to processes including the production of non-aqueous organic electrolytes, the regeneration of commercial electrolytes after long-term storage due to discoloration, and the production of liquid LiPF6 lithium salt products. Attached image description:

[0019] Figure 1 The electrolytes of Example 4 and Comparative Example 2 of this invention were tested for room temperature cycling performance in LMO / Li batteries.

[0020] Figure 2 Impedance performance testing of LMO / Li batteries using the electrolytes of Example 4 and Comparative Example 2 of this invention;

[0021] Figure 3 The room temperature 4.5V cycle performance test of the NCM811 / Li battery with electrolyte of Example 4 and blank comparative example 2 of the present invention;

[0022] Figure 4 Impedance performance testing of NCM811 / Li batteries using the electrolytes of Example 4 and Comparative Example 2 of this invention. Detailed implementation method:

[0023] The following is a further description of the invention, but not a limitation thereof.

[0024] Example 1: Preparation of LiHMDS-supported decolorizing agent

[0025] (1) Preparation of LiHMDS-350℃ supported molecular sieve

[0026] First, activate the 4A molecular sieve at 350℃ for 8 hours, then dry and store for later use. Weigh 7g of the activated molecular sieve and 1.76g of solid LiHMDS into a 50mL Slank tube in a glove box, seal it, and transfer it out of the glove box. Use an oil pump to create a vacuum in the tube. After evacuation, place the reaction tube at 90℃ and stir continuously until the solid LiHMDS is completely melted, maintaining this temperature for 10 minutes. Then, increase the temperature to 110℃ and maintain this temperature for 10 minutes. Stop heating and allow it to cool to room temperature to obtain LiHMDS-350℃ supported molecular sieve.

[0027] (2) Preparation of LiHMDS-850℃ supported molecular sieve

[0028] First, activate the 4A molecular sieve at 850℃ for 8 hours, then dry and store for later use. Weigh 7g of the activated molecular sieve and 1.76g of solid LiHMDS into a 50mL Slank tube in a glove box, seal it, and transfer it out of the glove box. Use an oil pump to create a vacuum in the tube. After evacuation, place the reaction tube at 90℃ and stir continuously until the solid LiHMDS is completely melted, maintaining this temperature for 10 minutes. Then, increase the temperature to 110℃ and maintain this temperature for 10 minutes. Stop heating and allow it to cool to room temperature to obtain LiHMDS-850℃ supported molecular sieve.

[0029] (3) Preparation of LiHMDS-supported activated carbon

[0030] First, the activated carbon was vacuum dried at 200℃ for 5 hours and then stored for later use. In a glove box, 7.2 g of activated carbon, 4.3 mL of LiHMDS-n-hexane solution (1 mol / L), and 10 mL of n-hexane were added sequentially to a 50 mL Slank tube. After stirring thoroughly, the tube was sealed. The solvent was removed by pumping out the reaction tube with an oil pump to obtain LiHMDS-supported activated carbon.

[0031] Example 2: Decolorization of deteriorated electrolyte A1 by different materials

[0032] In a glove box, 20g of the deteriorated electrolyte A1 was mixed with the LiHMDS-loaded decolorizing agent prepared in Example 1 in a 50mL bottle. After half an hour, the mixture was filtered to obtain the decolorized electrolyte. The color of the electrolyte was measured using a Sanenshi YS6060, the acidity was measured using a Leici ZDJ-4B instrument, and the moisture content was measured using a Metrohm Coulomb moisture analyzer, model 831KF. The results are shown in Table 1.

[0033] When the LiHMDS-loaded decolorizing agent was 1g LiHMDS-loaded molecular sieve at 350℃, the decolorized electrolyte B1 was obtained after filtration after half an hour, with a color value of 155.7 Hazen and a moisture content of 3.3 ppm. The results are shown in Table 1.

[0034] When the LiHMDS-loaded decolorizing agent is 1g LiHMDS-loaded molecular sieve at 850℃, after half an hour of filtration, the decolorized electrolyte B2 is obtained with a color value of 147.1 Hazen and a moisture content of 4.5ppm.

[0035] When the LiHMDS-supported decolorizing agent is 0.75g LiHMDS-supported activated carbon, after half an hour of filtration, the decolorized electrolyte B3 is obtained with a color value of 18.2 Hazen and a moisture content of 5.9ppm.

[0036] When the LiHMDS-supported decolorizing agent prepared in Example 1 was replaced with 0.082g LiHMDS, after half an hour, decolorized electrolyte B4 was obtained with a color value of 112.8 Hazen, a moisture content of 6.9 ppm, and an HF acidity value of 3.9 mg / kg.

[0037] When the LiHMDS-supported decolorizing agent prepared in Example 1 was replaced with 0.082g HMDS, after half an hour, decolorized electrolyte B5 was obtained with a color value of 254.3 Hazen, a moisture content of 2.9ppm, and an HF acidity value of 2.6mg / kg.

[0038] When the LiHMDS-supported decolorizing agent prepared in Example 1 was replaced with 0.3g of activated carbon, decolorized electrolyte B6 was obtained after half an hour, with a color value of 553.6 Hazen, a moisture content of 7ppm, and an HF acidity value of 500mg / kg.

[0039] When the LiHMDS-supported decolorizing agent prepared in Example 1 was replaced with 1g of ordinary molecular sieve, decolorized electrolyte B7 was obtained after half an hour, with a color value of 770 Hazen, a moisture content of 6.5ppm, and an HF acidity value of 600mg / kg.

[0040] Example 3: Decolorization of modified electrolyte A3 by LiHMDS-supported activated carbon

[0041] In a glove box, 30g of degraded electrolyte A3 and 2.2g of LiHMDS-supported activated carbon prepared in Example 1 were mixed in a 50mL bottle. After half an hour, decolorized electrolyte B8 was obtained with a color value of 38.9 Hazen, a moisture content of 16.8ppm, and an HF acidity value of 25.8mg / kg.

[0042] Blank comparison example 1:

[0043] The deteriorated lithium-ion electrolyte A1 has a color value of 772.3 Hazen, a moisture content of 7.0 ppm, and an HF acid value of 902 mg / kg. The results are shown in Table 1 below.

[0044] Blank comparison example 2:

[0045] The commercial electrolyte A2 has a color value of 50 Hazen, a moisture content of 6.9 ppm, and an HF acid value of 46.2 mg / kg. The results are shown in Table 1 below.

[0046] Blank comparison example 3:

[0047] The modified sodium ion electrolyte A3 had a color value of 357.5 Hazen, a moisture content of 37.1 ppm, and an HF acid value of 3278 mg / kg. The results are shown in Table 1 below.

[0048] Table 1 compares the effects of different types and dosages of decolorizing agents on color and moisture content.

[0049]

[0050]

[0051] As can be seen from the table, the decolorizing agent of the present invention has a significant effect on reducing the color, acidity and moisture content of the deteriorated electrolyte. Among them, LiHMDS-activated carbon has the most obvious effect, which can reduce the color of the deteriorated electrolyte from 772.3 Hazen to 18.2 Hazen. In addition, the moisture content of the deteriorated electrolyte treated with the decolorizing agent in Example 2 is less than 10 ppm.

[0052] Example 4:

[0053] 20g of commercially available electrolyte A2 (LB301 = 1M LiPF6 ethylene carbonate (EC) / dimethyl carbonate (DMC) / ethyl methyl carbonate (EMC) (1:1:1)) from Shanghai Xiaoyuan Energy Technology Co., Ltd. was weighed out. 1g of LiHMDS-850℃ supported molecular sieve was added to the electrolyte and filtered to obtain purified electrolyte B9.

[0054] Example 5: Electrode Fabrication

[0055] A positive electrode slurry is prepared according to a mass ratio of positive electrode material, conductive agent, and binder of (85-95):(1-9):(4-6). After adding solvent to adjust the solid content of the slurry to 25-50%, the slurry is coated onto aluminum foil and dried to obtain the positive electrode sheet. Similarly, a negative electrode slurry is prepared according to a mass ratio of negative electrode material, conductive agent, and binder of (90-98):(1-5):(1-5). After adding solvent to adjust the solid content of the slurry to 25-50%, the slurry is coated onto copper foil and dried to obtain the negative electrode sheet.

[0056] The positive electrode material is any one or more of ternary cathode, lithium iron phosphate, lithium cobalt oxide, nickel cobalt aluminum, and lithium manganese oxide; the negative electrode material is one of lithium metal, graphite, and lithium titanate.

[0057] Acetylene black is a conductive agent; the binder can be selected from at least one of vinylidene fluoride / hexafluoropropylene copolymer, vinylidene fluoride (PVDF), sodium carboxymethyl cellulose, polyacrylic acid and styrene-butadiene latex; the solvent can be selected from at least one of N-methylpyrrolidone, acetone and water.

[0058] Button cell separators are generally selected from separators that can be well wetted with electrolyte, such as polyethylene, polypropylene, or a mixture of both.

[0059] Example 6: Battery Assembly and Performance Testing

[0060] CR2025 button cells were assembled in a glove box. The positive electrode film was prepared according to Example 5, comprising ternary lithium nickel cobalt manganese oxide (NCM811), acetylene black, and PVDF in a mass ratio of 85:9:6. The negative electrode was a lithium sheet. The electrolytes from Example 4 and the blank comparative example 2 were used as test electrolytes. The cells were assembled in the following order: negative electrode shell, negative electrode sheet, electrolyte, separator, electrolyte, positive electrode sheet, and positive electrode shell. After assembly, the cells were left to stand for 12 hours to obtain the ternary NCM811 button cell.

[0061] CR2025 button cells were assembled in a glove box. The positive electrode was prepared according to Example 5, with the positive electrode film comprising lithium manganese oxide, acetylene black, and PVDF in a mass ratio of 85:9:6. The negative electrode was a lithium sheet. The electrolytes from Example 4 and the blank comparative example 2 were assembled sequentially in the following order: negative electrode shell, negative electrode sheet, electrolyte, separator, electrolyte, positive electrode sheet, and positive electrode shell. After assembly, the cells were left to stand for 12 hours to obtain the lithium manganese oxide button cell.

[0062] Battery impedance test method: After the battery cycle is completed, the AC impedance EIS is tested on the Shanghai Chenhua Electrochemical Workstation with an amplitude of 5mV and a frequency range of 0.01Hz to 100kHz.

[0063] like Figure 1 Using LMO and lithium foil as positive and negative electrodes respectively, 2025 coin cells were assembled. Charge / discharge tests were conducted at Shenzhen Xinwei, with a charge / discharge voltage of 3-4.3V. The battery assembled with the refined electrolyte of Example 4 was charged / discharged at a constant current of 1C. Compared to the blank control example 2 (without refined electrolyte), the LMO / Li half-cell assembled with the electrolyte of Example 4 showed improved room temperature cycling performance, with capacity retention increasing from 92.2% to 93.2% (100 cycles).

[0064] like Figure 2 Impedance testing of LMO / Li half-cells assembled with the electrolytes of Example 4 and Comparative Example 2 showed that the electrolyte of Example 4 significantly reduced the impedance of the interface film of the positive electrode material. (3 circles).

[0065] Figure 3Using NCM811 and lithium foil as positive and negative electrodes respectively, 2025 coin cells were assembled. Charge / discharge tests were conducted at Shenzhen Xinwei, with a charge / discharge voltage of 3-4.5V. The battery assembled with the electrolyte of Example 4 was charged / discharged at a constant current of 1C. It was found that the NCM811 / Li half-cell assembled with the electrolyte of Example 4 showed a significant improvement in cycle performance at a high voltage of 4.5V. The capacity retention increased from 78.3% to 86.8% (100 cycles).

[0066] like Figure 4 Impedance tests were performed on the NCM811 / Li half-cells assembled with the electrolytes of Example 4 and the blank control Example 2. The electrolyte additive in Example 4 significantly reduced the impedance of the NCM811 cathode material interface film. (3 circles)

Claims

1. The application of organolithium compound composite supported activator materials in electrolyte purification, characterized in that, It is used for decolorization, deacidification, and dehydration of non-aqueous organic electrolytes, including regeneration applications for commercial electrolytes that have changed color after long-term storage. The method includes the following steps: adding an organolithium compound composite supported activator material directly to a color-changing electrolyte at room temperature, with a dosage of 1-13 kg / 50 L of color-changing electrolyte, followed by filtration to obtain a purified electrolyte product; the preparation method of the organolithium compound composite supported activator material includes the following steps: activating the carrier material at 200°C before use, and then uniformly mixing it with the organolithium compound in a reaction flask to obtain the organolithium compound supported activator material; the preparation of the organolithium compound supported activator material also involves adding a reaction solvent for mixing, followed by removing the solvent by vacuum pumping; the organolithium compound is selected from any one of bis(trimethylsilylaminolithium), diisopropylaminolithium, and 2,2,6,6-tetramethylpiperidinelithium; the carrier material is activated carbon.

2. The application according to claim 1, characterized in that, The amount of the organolithium compound used is 0.1%-25% of the mass of the carrier material.

3. The application according to claim 1, characterized in that, The non-aqueous organic electrolyte is an electrolyte containing a metal salt and an organic solvent; the organic solvent is one or more of dimethyl carbonate, ethylene carbonate, methyl ethyl carbonate, diethyl carbonate, and propylene carbonate; the metal salt is one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium difluorooxalate borate, lithium bis(oxalate borate), lithium bis(trifluoromethanesulfonyl)imide, and lithium bis(fluorosulfonyl)imide, or one or more corresponding sodium metal salts.

4. The application according to claim 3, characterized in that, The non-aqueous organic electrolyte is used in lithium-ion batteries and sodium-ion batteries.

5. The application according to claim 4, characterized in that, The positive electrode material of lithium-ion batteries uses one or more of the following systems: ternary cathode, lithium iron phosphate, lithium cobalt oxide, nickel cobalt aluminum, and lithium manganese oxide. The negative electrode material of lithium-ion batteries uses one of the following systems: metallic lithium, graphite, lithium titanate, or silicon-based system.

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