Electrolyte composite water trapping agent, preparation method thereof, electrolyte and battery

Abstract

The application provides an electrolyte composite water capturing agent, a preparation method thereof, an electrolyte and a battery. The electrolyte composite water capturing agent comprises a deep eutectic solvent matrix and a crown ether compound. The deep eutectic solvent matrix comprises an organic base and an organic acid. The organic base comprises choline chloride and / or betaine. The electrolyte composite water capturing agent can not only capture water in the electrolyte, but also continuously control the water content in the electrolyte efficiently. In addition, the water can be converted into a substance that is beneficial to the stability of the electrode interface, thereby improving the cycle life and the interface stability of the battery.

Description

Technical Field

[0001] This invention belongs to the field of battery technology and relates to an electrolyte composite water-capturing agent and its preparation method, as well as the electrolyte and battery. Background Technology

[0002] During the production and storage of lithium-ion batteries, trace amounts of moisture are inevitably introduced. The presence of moisture in the electrolyte will react with commonly used lithium salts (such as LiPF6) to generate HF, which corrodes electrode materials and catalyzes the decomposition of organic solvents, leading to a series of problems such as battery capacity decay, increased internal resistance, and gas generation.

[0003] Currently, the main method for removing water from the electrolyte is to add a small amount of water-removing agent before battery assembly. Existing technology discloses the use of isocyanate compounds as water-removing agents, which react with water to generate CO2 and amines, thereby removing water. However, this method has significant drawbacks: the generated CO2 may lead to increased internal battery pressure, posing a safety hazard, and the amines may have unknown negative impacts on battery performance. Another common method is to add physical adsorbents (such as molecular sieves) to remove water, but physical adsorbents have limited adsorption capacity and lack sustainability; they become ineffective once saturated.

[0004] More importantly, current technologies focus on how to eliminate water, without considering how to utilize it. The introduction of water essentially brings additional chemical energy; if it can be channeled into beneficial chemical pathways, it can be turned from a hazard into a resource.

[0005] Therefore, a new type of electrolyte composite water-removing agent is needed, which can not only efficiently remove water, but also transform water into a beneficial substance that can improve the electrochemical performance of the battery. Summary of the Invention

[0006] The purpose of this invention is to provide an electrolyte composite water-capturing agent and its preparation method, as well as an electrolyte and a battery. The electrolyte composite water-capturing agent can not only efficiently capture water in the electrolyte and efficiently and continuously control the water content in the electrolyte, but also convert water into substances that are beneficial to the stability of the electrode interface, thereby improving the cycle life and interface stability of the battery.

[0007] To achieve this objective, the present invention adopts the following technical solution:

[0008] In a first aspect, the present invention provides an electrolyte composite water-catching agent, the electrolyte composite water-catching agent comprising a deep eutectic solvent matrix and a crown ether compound, the deep eutectic solvent matrix comprising an organic base and an organic acid, the organic base comprising choline chloride and / or betaine.

[0009] The electrolyte composite water-trapping agent of this invention comprises a deep eutectic solvent matrix and a complex of crown ether compounds. The deep eutectic solvent matrix is ​​internally filled with a network of hydrogen bonds. When water molecules enter, they react with hydroxyl (-OH), carboxyl (-COOH), and chloride (Cl) ions in the deep eutectic solvent matrix. - Crown ethers form stronger hydrogen bonds, thus binding water molecules. Their unique cavity structure allows them to selectively complex lithium ions, forming stable crown ethers -Li. + The complex, consisting of water molecules bound by a deep eutectic solvent matrix, has oxygen atoms whose lone pair electrons in their OH bonds can complex with Li₂C₃, which is bound to a crown ether. + Further weak interactions occur: 2H₂O + 2e⁻ - +2Li + → 2LiOH + H₂↑, and a beneficial interfacial chemical reaction will also occur, producing Li₂O and LiF, with the specific chemical formula: 2LiOH + 2e⁻ - +2Li + →2Li₂O + H₂↑, 4HF + 4e⁻ - +4Li + →4LiF + 2H2↑ (trace amounts of HF produced by the decomposition of LiPF6 in the electrolyte). Therefore, this invention can not only efficiently and continuously control the moisture in the electrolyte, but also convert water into substances (Li2O and LiF) that are beneficial to the stability of the electrode interface, thereby improving the cycle life and interface stability of lithium-ion batteries. The small amount of hydrogen produced is much lower than that of traditional dehydrating agents because the moisture is highly bound and the reaction is controllable and localized. Furthermore, it will be effectively discharged in the subsequent formation and high-temperature settling processes.

[0010] Preferably, the mass ratio of the deep eutectic solvent matrix to the crown ether compound is (5-15):1, for example, it can be 5:1, 7:1, 9:1, 11:1, 13:1 or 15:1, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0011] The mass ratio of the deep eutectic solvent matrix to the crown ether compound described in this invention is preferably within a specific range. If the deep eutectic solvent matrix is ​​too small, the crown ether compound will be relatively excessive, causing the free crown ether to over-complex lithium ions on the negative electrode surface, disrupting the normal desolvation and deposition process of lithium ions, resulting in battery capacity decay and deterioration of cycle performance. If the deep eutectic solvent matrix is ​​too large, the crown ether concentration will be over-diluted, and it will be unable to effectively complex and guide lithium ions. As a result, the water molecules adsorbed by the deep eutectic solvent matrix will lack "navigation" and will be difficult to undergo in-situ transformation at the interface. The function of the water trap will be downgraded to simple physical adsorption, and the effect of improving battery performance will be weakened.

[0012] Preferably, the molar ratio of the organic base to the organic acid is 1:(0.5-2), for example, it can be 1:0.5, 1:1, 1:1.5 or 1:2, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0013] In the deep eutectic solvent matrix described in this invention, the molar ratio of organic base to organic acid is preferably within a specific range. If the organic base is too small compared to the organic acid, the hydrogen bond donor (organic acid) is excessive, causing the deep eutectic solvent system to deviate from the eutectic point, making it difficult to form a uniform and stable eutectic mixture. Unreacted organic acid crystals may precipitate, and excessive carboxyl groups (-COOH) may increase the acidity of the system, exacerbating the corrosion risk to the battery cathode material or current collector. If the organic base is too large compared to the organic acid, the hydrogen bond acceptor (organic base) is excessive. The excess organic base cannot form an effective hydrogen bond network with the organic acid and may exist in the system in a free state. On the one hand, this increases the chloride ion (Cl⁻) concentration, which may trigger side reactions or corrode the stainless steel shell under high pressure. On the other hand, excessive organic base cations may participate in interfacial reactions, leading to a more complex SEI film composition and increasing irreversible capacity loss.

[0014] Preferably, the crown ether compound includes any one or a combination of at least two of 18-crown-6, 12-crown-4, 15-crown-5, or benzocrown ethers.

[0015] Preferably, the organic acid includes citric acid and / or acetylpropionic acid.

[0016] In a second aspect, the present invention provides a method for preparing an electrolyte composite water-capturing agent as described in the first aspect, the preparation method comprising the following steps:

[0017] (1) Mix organic base and organic acid to obtain a mixture, and heat and stir the mixture to obtain a deep eutectic solvent matrix;

[0018] (2) The crown ether compound, solvent and deep eutectic solvent matrix described in step (1) are mixed to obtain a mixed solution. The mixed solution is then desolventized and dried to obtain the electrolyte composite water-trapping agent.

[0019] Preferably, the heating and stirring temperature in step (1) is 60℃-80℃, for example, it can be 60℃, 65℃, 70℃, 75℃ or 80℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0020] Preferably, the heating and stirring time in step (1) is 1h-2h, for example, it can be 1h, 1.2h, 1.4h, 1.6h, 1.8h or 2h, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0021] Preferably, the heating and stirring in step (1) is carried out under a protective atmosphere, which includes any one or a combination of at least two of nitrogen, argon or helium.

[0022] Preferably, the temperature at which the crown ether compound, the solvent, and the deep eutectic solvent matrix of step (1) are mixed in step (2) is 35°C-50°C, for example, 35°C, 40°C, 45°C, or 50°C, and the time is 3h-5h, for example, 3h, 3.5h, 4h, 4.5h, or 5h, but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0023] Preferably, the mass ratio of the crown ether compound to the volume of the solvent in step (2) is 1g:(40-60)mL, for example, it can be 1g:40mL, 1g:45mL, 1g:50mL, 1g:55mL or 1g:60mL, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0024] Preferably, the solvent in step (2) includes ethanol.

[0025] Preferably, the solvent removal method in step (2) includes evaporation.

[0026] Preferably, the drying temperature in step (2) is 50℃-70℃, for example, 50℃, 55℃, 60℃, 65℃ or 70℃, and the time is 18h-28h, for example, 18h, 20h, 22h, 24h, 26h or 28h, but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0027] Preferably, after drying in step (2), the particles are further ground until the particle size D50 is less than 100 μm. For example, the particle size can be 95 μm, 90 μm, 85 μm, 80 μm, 75 μm, 70 μm, 65 μm or 60 μm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0028] Thirdly, the present invention provides an electrolyte comprising a lithium salt, an organic solvent, and an electrolyte composite water-capturing agent as described in the first aspect.

[0029] Preferably, the content of the electrolyte composite water-capturing agent in the electrolyte is 0.5-2wt%, for example, it can be 0.5wt%, 1wt%, 1.5wt% or 2wt%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0030] The electrolyte of the present invention preferably contains a specific amount of electrolyte composite water-catching agent. If the amount of electrolyte composite water-catching agent added is too small, the water removal effect will decrease; however, if the amount of electrolyte composite water-catching agent added is too large, the overall viscosity of the electrolyte will increase, thereby increasing the internal resistance and restricting lithium ion migration.

[0031] Preferably, the lithium salt includes any one or a combination of at least two of LiPF6, LiBF4, LiBOB, LiTFSI, or LiFSI.

[0032] Preferably, the organic solvent includes ethylene carbonate (EC), dimethyl carbonate (DMC), and diethyl carbonate (DEC).

[0033] Fourthly, the present invention provides a battery comprising an electrolyte composite water-capturing agent as described in the first aspect, or an electrolyte as described in the third aspect.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] This invention utilizes a deep eutectic solvent as the matrix of a composite water-capturing agent, which is filled with a network of hydrogen bonds. When water molecules enter, they react with hydroxyl (-OH), carboxyl (-COOH), and chloride (Cl) ions in the deep eutectic solvent matrix. - Crown ethers form stronger hydrogen bonds, thus binding water molecules. Their unique cavity structure allows them to selectively complex lithium ions, forming stable crown ethers -Li. + The complex, consisting of water molecules bound by a deep eutectic solvent matrix, has oxygen atoms whose lone pair electrons in their OH bonds can complex with Li₂C₃, which is bound to a crown ether. + Further weak interactions occur: 2H₂O + 2e⁻ + 2Li + →2LiOH+H2↑, and beneficial interfacial chemical reactions will also occur to generate Li2O and LiF. Therefore, this invention can not only efficiently and continuously control the moisture in the electrolyte, but also convert water into substances (Li2O and LiF) that are beneficial to the stability of the electrode interface, thereby improving the cycle life and interfacial stability of lithium-ion batteries. The small amount of hydrogen produced is much lower than that of traditional dehydrating agents because the moisture is highly bound and the reaction is controllable and localized. It will be effectively discharged in the subsequent formation and high-temperature settling processes. Detailed Implementation

[0036] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0037] Example 1

[0038] This embodiment provides an electrolyte composite water-catching agent, which includes a deep eutectic solvent matrix and a crown ether compound. The crown ether compound includes 18-crown-6, and the deep eutectic solvent matrix includes choline chloride and citric acid.

[0039] The mass ratio of the deep eutectic solvent matrix to the crown ether compound is 10:1, and the molar ratio of choline chloride to citric acid is 1:1.

[0040] The preparation method of the electrolyte composite water-capturing agent includes the following steps:

[0041] (1) In a dry reactor, choline chloride and citric acid are weighed and mixed according to the formula to obtain a mixture. The mixture is placed in an oil bath at 70°C and magnetically stirred for 1.5 h under nitrogen protection until a homogeneous, transparent, colorless liquid is formed. After cooling to room temperature, a deep eutectic solvent matrix is ​​obtained.

[0042] (2) Dissolve the deep eutectic solvent matrix and crown ether compound described in step (1) together in anhydrous ethanol according to the formula amount, and stir continuously at 40°C for 4 hours to obtain a mixed solution, wherein the mass ratio of the crown ether compound to the volume of anhydrous ethanol is 1g:50mL.

[0043] The mixed solution was poured into a polytetrafluoroethylene petri dish and placed in a fume hood to allow the anhydrous ethanol to evaporate slowly at room temperature. After the ethanol had completely evaporated, a translucent gel-like solid was obtained. This gel-like solid was placed in a vacuum drying oven and dried at 60°C for 24 hours. Finally, the dried block was ground into a powder with a particle size D50 of 70 μm to obtain the composite water-capturing agent.

[0044] This embodiment also provides an electrolyte, which includes 1 wt% of the composite water-capturing agent described in this embodiment, and also includes ethylene carbonate, dimethyl carbonate and diethyl carbonate in a volume ratio of 1:1:1 and 1.0 mol / L of LiPF6.

[0045] The preparation method of the electrolyte includes the following steps: In a glove box filled with argon (H2O content <1ppm, O2 content <1ppm), ethylene carbonate, dimethyl carbonate and diethyl carbonate are mixed in a volume ratio of 1:1:1, and then fully dried LiPF6 is added to prepare a basic electrolyte.

[0046] According to the formula, the composite water-capturing agent described in this embodiment is added to the basic electrolyte, and mechanically stirred for 6 hours to disperse it evenly, thus obtaining the electrolyte described in this embodiment.

[0047] Example 2

[0048] This embodiment provides an electrolyte composite water-catching agent, which includes a deep eutectic solvent matrix and a crown ether compound. The crown ether compound includes 18-crown-6, and the deep eutectic solvent matrix includes choline chloride and citric acid.

[0049] The mass ratio of the deep eutectic solvent matrix to the crown ether compound is 5:1, and the molar ratio of choline chloride to citric acid is 1:2.

[0050] The preparation method of the electrolyte composite water-capturing agent includes the following steps:

[0051] (1) In a dry reactor, choline chloride and citric acid are weighed and mixed according to the formula to obtain a mixture. The mixture is placed in an oil bath at 80°C and magnetically stirred for 1 hour under nitrogen protection until a homogeneous, transparent, colorless liquid is formed. After cooling to room temperature, a deep eutectic solvent matrix is ​​obtained.

[0052] (2) Dissolve the deep eutectic solvent matrix and crown ether compound described in step (1) together in anhydrous ethanol according to the formula amount, and stir continuously at 35°C for 5 hours to obtain a mixed solution, wherein the mass ratio of the crown ether compound to the volume of anhydrous ethanol is 1g:40mL.

[0053] The mixed solution was poured into a polytetrafluoroethylene petri dish and placed in a fume hood to allow the anhydrous ethanol to evaporate slowly at room temperature. After the ethanol had completely evaporated, a translucent gel-like solid was obtained. This gel-like solid was placed in a vacuum drying oven and dried at 70°C for 18 hours. Finally, the dried block was ground into a powder with a particle size D50 of 90 μm to obtain the composite water-trapping agent.

[0054] This embodiment also provides an electrolyte, which includes 2 wt% of the composite water-capturing agent described in this embodiment, and also includes ethylene carbonate, dimethyl carbonate and diethyl carbonate in a volume ratio of 1:1:1 and 1.0 mol / L of LiPF6.

[0055] The preparation method of the electrolyte includes the following steps: In a glove box filled with argon (H2O content <1ppm, O2 content <1ppm), ethylene carbonate, dimethyl carbonate and diethyl carbonate are mixed in a volume ratio of 1:1:1, and then fully dried LiPF6 is added to prepare a basic electrolyte.

[0056] According to the formula, the composite water-capturing agent described in this embodiment is added to the basic electrolyte, and mechanically stirred for 6 hours to disperse it evenly, thus obtaining the electrolyte described in this embodiment.

[0057] Example 3

[0058] This embodiment provides an electrolyte composite water-trapping agent, which includes a deep eutectic solvent matrix and a crown ether compound, wherein the crown ether compound includes 12-crown-4, and the deep eutectic solvent matrix includes betaine and levulinic acid;

[0059] The mass ratio of the deep eutectic solvent matrix to the crown ether compound is 15:1, and the molar ratio of betaine to levulinic acid is 1:0.5.

[0060] The preparation method of the electrolyte composite water-capturing agent includes the following steps:

[0061] (1) In a dry reactor, betaine and levulinic acid are weighed and mixed according to the formula to obtain a mixture. The mixture is placed in an oil bath at 60°C and magnetically stirred for 2 hours under nitrogen protection until a homogeneous, transparent, colorless liquid is formed. After cooling to room temperature, a deep eutectic solvent matrix is ​​obtained.

[0062] (2) Dissolve the deep eutectic solvent matrix and crown ether compound described in step (1) together in anhydrous ethanol according to the formula amount, and stir continuously at 50°C for 3 hours to obtain a mixed solution, wherein the mass ratio of the crown ether compound to the volume of anhydrous ethanol is 1g:60mL.

[0063] The mixed solution was poured into a polytetrafluoroethylene petri dish and placed in a fume hood to allow the anhydrous ethanol to evaporate slowly at room temperature. After the ethanol had completely evaporated, a translucent gel-like solid was obtained. This gel-like solid was placed in a vacuum drying oven and dried at 50°C for 28 hours. Finally, the dried block was ground into a powder with a particle size D50 of 60 μm to obtain the composite water-capturing agent.

[0064] This embodiment also provides an electrolyte, which includes 0.5 wt% of the composite water-capturing agent described in this embodiment, and also includes ethylene carbonate, dimethyl carbonate and diethyl carbonate in a volume ratio of 1:1:1 and 1.0 mol / L of LiPF6.

[0065] The preparation method of the electrolyte includes the following steps: In a glove box filled with argon (H2O content <1ppm, O2 content <1ppm), ethylene carbonate, dimethyl carbonate and diethyl carbonate are mixed in a volume ratio of 1:1:1, and then fully dried LiPF6 is added to prepare a basic electrolyte.

[0066] According to the formula, the composite water-capturing agent described in this embodiment is added to the basic electrolyte, and mechanically stirred for 6 hours to disperse it evenly, thus obtaining the electrolyte described in this embodiment.

[0067] Example 4

[0068] This embodiment provides an electrolyte composite water-catching agent, which is the same as that in Example 1 except that the mass ratio of deep eutectic solvent matrix to crown ether compound is 3:1.

[0069] The preparation method of the electrolyte composite water-capturing agent is the same as that in Example 1, except that the formulation amount is adapted to change.

[0070] This embodiment also provides an electrolyte, which is the same as that in Example 1 except that it uses the electrolyte composite water-capturing agent described in this embodiment.

[0071] Example 5

[0072] This embodiment provides an electrolyte composite water-catching agent, which is the same as that in Example 1 except that the mass ratio of deep eutectic solvent matrix to crown ether compound is 18:1.

[0073] The preparation method of the electrolyte composite water-capturing agent is the same as that in Example 1, except that the formulation amount is adapted to change.

[0074] This embodiment also provides an electrolyte, which is the same as that in Example 1 except that it uses the electrolyte composite water-capturing agent described in this embodiment.

[0075] Example 6

[0076] This embodiment provides an electrolyte composite water-catching agent, which is the same as that in Example 1 except that the molar ratio of choline chloride and citric acid is 0.3:1;

[0077] The preparation method of the electrolyte composite water-capturing agent is the same as that in Example 1, except that the formulation amount is adapted to change.

[0078] This embodiment also provides an electrolyte, which is the same as that in Example 1 except that it uses the electrolyte composite water-capturing agent described in this embodiment.

[0079] Example 7

[0080] This embodiment provides an electrolyte composite water-catching agent, which is the same as that in Example 1 except that the molar ratio of choline chloride and citric acid is 3:1.

[0081] The preparation method of the electrolyte composite water-capturing agent is the same as that in Example 1, except that the formulation amount is adapted to change.

[0082] This embodiment also provides an electrolyte, which is the same as that in Example 1 except that it uses the electrolyte composite water-capturing agent described in this embodiment.

[0083] Example 8

[0084] This embodiment provides an electrolyte composite water-capturing agent, which is the same as that in Embodiment 1;

[0085] The preparation method of the electrolyte composite water-capturing agent is the same as that in Example 1.

[0086] This embodiment also provides an electrolyte, which is the same as that in Example 1 except that it includes 0.3 wt% of the composite water-capturing agent described in this embodiment.

[0087] Example 9

[0088] This embodiment provides an electrolyte composite water-capturing agent, which is the same as that in Embodiment 1;

[0089] The preparation method of the electrolyte composite water-capturing agent is the same as that in Example 1.

[0090] This embodiment also provides an electrolyte, which is the same as that in Example 1 except that it includes 3.5 wt% of the composite water-capturing agent described in this embodiment.

[0091] Comparative Example 1

[0092] This comparative example provides an electrolyte that is identical to that of Example 1, except that it does not include the composite water-capturing agent described in Example 1 and is instead the basic electrolyte described in Example 1.

[0093] Comparative Example 2

[0094] This comparative example provides an electrolyte composite water-capturing agent, wherein the electrolyte composite water-capturing agent is phenyl isocyanate;

[0095] This comparative example also provides an electrolyte, which is the same as that in Example 1 except that it uses the electrolyte composite water-capturing agent described in this comparative example.

[0096] Comparative Example 3

[0097] This comparative example provides an electrolyte composite water-catching agent, which is the same as in Example 1 except that the deep eutectic solvent matrix does not contain choline chloride.

[0098] The preparation method of the electrolyte composite water-capturing agent is the same as that in Example 1, except that step (1) is omitted and step (2) is carried out directly with citric acid and crown ether compounds.

[0099] This comparative example also provides an electrolyte, which is the same as that in Example 1 except that it uses the electrolyte composite water-capturing agent described in this comparative example.

[0100] Comparative Example 4

[0101] This comparative example provides an electrolyte composite water-catching agent, which is the same as in Example 1 except that the deep eutectic solvent matrix does not contain citric acid;

[0102] The preparation method of the electrolyte composite water-capturing agent is the same as that in Example 1, except that step (1) is omitted and step (2) is carried out directly with citric acid and crown ether compounds.

[0103] This comparative example also provides an electrolyte, which is the same as that in Example 1 except that it uses the electrolyte composite water-capturing agent described in this comparative example.

[0104] Comparative Example 5

[0105] This comparative example provides an electrolyte composite water-catching agent, which is the same as that in Example 1 except that it does not contain crown ether compounds;

[0106] The preparation method of the electrolyte composite water-capturing agent is the same as that in Example 1, except that step (2) is not performed.

[0107] This comparative example also provides an electrolyte, which is the same as that in Example 1 except that it uses the electrolyte composite water-capturing agent described in this comparative example.

[0108] The electrolytes described in the above embodiments and comparative examples were used to prepare pouch cells. The preparation process is as follows:

[0109] (1) Preparation method of positive electrode sheet: The positive electrode material (LFP), conductive carbon black (Super P), binder (PVDF) and dispersant (polypyrrolidone) are mixed in a mass ratio of 9.6:0.2:0.17:0.03, and then N-methylpyrrolidone is added and mixed to obtain positive electrode slurry; the obtained positive electrode slurry is uniformly coated on 12μm aluminum foil, and after drying, the positive electrode sheet is obtained.

[0110] (2) Preparation method of negative electrode sheet: The negative electrode main material (graphite:silicon carbon mass ratio = 95:5), conductive carbon black (Super P), carboxymethyl cellulose, dispersant (polypyrrolidone) and binder (styrene-butadiene rubber) are mixed in a mass ratio of 96:0.5:0.5:0.8:2.2, and then mixed with deionized water to obtain negative electrode slurry; the obtained negative electrode slurry is uniformly coated on a 5μm thick copper foil, and after drying, the negative electrode sheet is obtained.

[0111] (3) The diaphragm is a commercially available polyolefin diaphragm;

[0112] (4) After cutting the obtained positive and negative electrode sheets, stack them with the separator, insert them into the shell, vacuum bake them, inject the electrolyte (the electrolyte described in the above examples and comparative examples), let them stand, and after forming and compatibility, a soft pack battery is obtained.

[0113] The moisture content of the electrolytes described in the above examples and comparative examples was tested after standing for 0 days, 3 days, and 7 days. The cycle performance of the obtained pouch batteries and the composition of the negative electrode SEI film after 500 cycles were also tested. The moisture content was tested using the Karl Fischer method, following GB / T 45330-2025. The cycle performance was tested within a charge / discharge range of 2.5V-3.65V, following GB / T 31484-2015. The composition of the negative electrode SEI film after 500 cycles was analyzed using X-ray photoelectron spectroscopy (XPS).

[0114] The test results are shown in Table 1 below:

[0115] Table 1

[0116]

[0117] As can be seen from Table 1 above:

[0118] As shown in Example 1 and Comparative Example 1, the addition of a composite water-trapping agent to the basic electrolyte of Comparative Example 1 significantly reduces the water content in the electrolyte, while also greatly improving the battery's cycle performance and the LiF content in the negative electrode SEI film. As shown in Example 1 and Comparative Example 2, the composite water-trapping agent described in this invention has a better water removal effect than conventional dehydrating agents and can convert water into substances that enhance interfacial stability, thereby improving the battery's electrochemical performance. As shown in Example 1 and Comparative Examples 3-5, this invention uses choline chloride and organic acids to construct a hydrogen bond network, binding water molecules. The bound water molecules can then react further with crown ether-complexed lithium ions to generate substances that enhance interfacial stability. Therefore, the absence of any one of the substances—choline chloride, organic acid, and crown ether compounds—will prevent the achievement of the effects of this invention, resulting in a decrease in water removal efficiency and battery performance. As shown in Examples 1 and 4-5, the mass ratio of the deep eutectic solvent matrix to the crown ether compounds in this invention affects the effectiveness of the electrolyte composite water-catching agent, preferably within a specific range. As shown in Examples 1 and 6-7, the molar ratio of choline chloride to organic acid in this invention is preferably within a specific range to promote the ability of the deep eutectic solvent matrix to bind water molecules, thereby promoting the effectiveness of the electrolyte composite water-catching agent. As shown in Examples 1 and 8-9, the amount of water-catching agent added to the electrolyte in this invention affects its effectiveness, preferably within a specific range.

[0119] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. An electrolyte composite water-capturing agent, characterized in that, The electrolyte composite water-capturing agent comprises a deep eutectic solvent matrix and crown ether compounds. The deep eutectic solvent matrix comprises organic bases and organic acids, and the organic bases comprise choline chloride and / or betaine.

2. The electrolyte composite water-capturing agent according to claim 1, characterized in that, The mass ratio of the deep eutectic solvent matrix to the crown ether compound is (5-15):1; Preferably, the molar ratio of the organic base to the organic acid is 1:(0.5-2).

3. The electrolyte composite water-capturing agent according to claim 1 or 2, characterized in that, The crown ether compounds include any one or a combination of at least two of 18-crown-6, 12-crown-4, 15-crown-5 or benzocrown ethers; Preferably, the organic acid includes citric acid and / or acetylpropionic acid.

4. A method for preparing an electrolyte composite water-capturing agent as described in any one of claims 1-3, characterized in that, The preparation method includes the following steps: (1) Mix organic base and organic acid to obtain a mixture, and heat and stir the mixture to obtain a deep eutectic solvent matrix; (2) The crown ether compound, solvent and deep eutectic solvent matrix described in step (1) are mixed to obtain a mixed solution. The mixed solution is then desolventized and dried to obtain the electrolyte composite water-trapping agent.

5. The preparation method according to claim 4, characterized in that, The heating and stirring temperature in step (1) is 60℃-80℃; Preferably, the heating and stirring time in step (1) is 1-2 hours; Preferably, the heating and stirring in step (1) is carried out under a protective atmosphere, which includes any one or a combination of at least two of nitrogen, argon or helium.

6. The preparation method according to claim 4 or 5, characterized in that, The temperature for mixing the crown ether compound, solvent and deep eutectic solvent matrix described in step (2) is 35℃-50℃, and the time is 3h-5h. Preferably, the mass ratio of the crown ether compound to the volume of the solvent in step (2) is 1 g:(40-60) mL; Preferably, the solvent in step (2) includes ethanol.

7. The preparation method according to claim 4 or 5, characterized in that, The solvent removal method described in step (2) includes evaporation; Preferably, the drying temperature in step (2) is 50℃-70℃ and the drying time is 18h-28h; Preferably, after drying in step (2), the particles are further ground until the particle size D50 < 100 μm.

8. An electrolyte, characterized in that, The electrolyte comprises lithium salt, organic solvent, and electrolyte composite water-capturing agent as described in any one of claims 1-3.

9. The electrolyte according to claim 8, characterized in that, The electrolyte contains 0.5-2 wt% of a composite water-capturing agent.

10. A battery, characterized in that, The battery includes the electrolyte composite water-capturing agent as described in any one of claims 1-3, or the electrolyte as described in claim 8 or 9.

Images