Battery and preparation method thereof

Abstract

The invention relates to the field of batteries, in particular to a battery and a preparation method thereof. The battery comprises a diaphragm and electrolyte, the diaphragm comprises a base film, a first coating arranged on the surface of one side of the base film along the thickness direction, a second coating arranged on the surface of one side of the first coating far away from the base film, and a third coating arranged on the surface of the other side of the base film along the thickness direction; the first coating comprises boron nitride; the second coating comprises a silane coupling agent modified aluminum-based compound; the third coating comprises a first lithium salt and a polymer; the electrolyte comprises a silicon-based compound. According to the battery composite electrolyte and the diaphragm system provided by the invention, the problems of SEI membrane rupture, lithium dendrite growth, poor thermal stability and the like of the electrolyte during high-rate rapid charging are solved, and the rapid charging performance of the battery is improved through the combined action of the diaphragm structure system and the electrolyte.

Description

Technical Field

[0001] This invention relates to the field of batteries, and more specifically, to a battery and a method for preparing the same. Background Technology

[0002] Traditional lithium-ion battery electrolytes suffer from the following problems during high-rate charging: low lithium-ion migration rate, leading to concentration polarization and lithium dendrite growth; the negative electrode SEI film is prone to rupture under high current, resulting in reduced cycle life; and conventional carbonate electrolytes experience intensified side reactions with the positive electrode material (such as high-nickel ternary materials) at high temperatures, posing a risk of thermal runaway. Current technologies often address high and low temperature performance through optimization with single additives or solvents. For example, some additives can improve SEI film stability but have no significant effect on ion migration, while some high-dielectric-constant solvents can improve ion solubility but sacrifice low-temperature fluidity. However, the optimization effect of single additives or solvents is relatively limited, making it difficult to simultaneously achieve ion transport efficiency, interface stability, and thermal safety at high rates, severely restricting the further application of lithium-ion batteries in high-power-density scenarios (such as fast charging of electric vehicles and large-scale energy storage systems). Summary of the Invention

[0003] In view of this, the present invention aims to provide a battery and its preparation method to solve the problems of SEI film rupture, lithium dendrite growth, and poor thermal stability of electrolytes in the prior art during high-rate fast charging.

[0004] To solve the above-mentioned technical problems, this application is implemented as follows: The present invention provides a battery comprising a separator and an electrolyte. The separator comprises a base film, a first coating disposed on one side surface of the base film along the thickness direction, a second coating disposed on the side surface of the first coating away from the base film, and a third coating disposed on the other side surface of the base film along the thickness direction. The first coating comprises boron nitride; The second coating comprises a silane coupling agent modified aluminum-based compound; The third coating comprises a first lithium salt and a polymer; The electrolyte contains silicon-based compounds.

[0005] Optionally, the silicon-based compound includes silicon dioxide; optionally, the mass content of the silicon-based compound is 1% to 3% based on the total mass of the electrolyte.

[0006] Optionally, the thickness of the first coating is 1~3 μm; optionally, the thickness of the second coating is 1~3 μm; optionally, the thickness of the third coating is 1~3 μm; optionally, the thickness of the base film is 5~11 μm; optionally, the base film comprises a polyolefin and / or ceramic membrane.

[0007] Optionally, the first coating further includes a first dispersant and a first binder; optionally, the mass ratio of boron nitride, the first dispersant, and the first binder is (80~95):(2~10):(3~10); optionally, the first dispersant includes polyvinylpyrrolidone and / or polyethylene glycol; optionally, the first binder includes polyvinylidene fluoride and / or polyacrylic acid; optionally, the second coating further includes a second dispersant and a second binder; optionally, the mass ratio of the silane coupling agent modified aluminum-based compound, the second dispersant, and the second binder is (75~95):(2~15):(3~15); optionally, the aluminum-based compound includes alumina; optionally, the second dispersant includes at least one of sodium polyacrylate, polyethylene oxide, and polyethylene glycol; optionally, the second binder includes acrylate and / or polyvinylidene fluoride.

[0008] Optionally, the total mass of the first lithium salt and the polymer is used as a basis, and the mass content of the first lithium salt is 20% to 40%; optionally, the first lithium salt includes lithium fluoride and / or lithium aluminate; optionally, the polymer includes polyimide and / or polyether ether ketone.

[0009] Optionally, the electrolyte further includes a second lithium salt and an organic solvent; optionally, the concentration of the second lithium salt in the electrolyte is 1~3 mol / L; optionally, the second lithium salt includes at least one of lithium fluorophosphate, lithium bis(fluorosulfonyl)imide, and lithium bis(trifluoromethanesulfonyl)imide; optionally, the organic solvent includes at least one of ethylene carbonate, propylene carbonate, dimethyl carbonate, ethyl methyl carbonate, and diethyl carbonate.

[0010] A second aspect of the present invention provides a method for preparing a battery, comprising the following steps: The first slurry is coated on one side surface of the base film along the thickness direction, and then dried to obtain a base film with the first coating. The second slurry is coated onto the surface of the first coating away from the base film, and then dried to obtain a base film with the second coating. The third slurry is coated onto the other side of the base film with the second coating along the thickness direction, and then dried in the third stage to obtain a diaphragm; The diaphragm, positive electrode, negative electrode, and electrolyte containing silicon-based compounds are assembled. The first slurry includes boron nitride; The second slurry includes a silane coupling agent-modified aluminum-based compound; The third slurry includes a first lithium salt and a polymer.

[0011] Optionally, the preparation of the silane coupling agent modified aluminum-based compound includes the following steps: An aluminum-based compound and a silane coupling agent solution are mixed, dispersed in the first stage, reacted, and then dried. Optionally, the mass ratio of the aluminum-based compound to the silane coupling agent solution is 10-15:1. Optionally, the concentration of the silane coupling agent solution is 0.005-0.02 mol / L. Optionally, the aluminum-based compound includes alumina. Optionally, the silane coupling agent in the silane coupling agent solution includes at least one of aminosilane coupling agents, mercaptosilane coupling agents, epoxysilane coupling agents, vinylsilane coupling agents, and cyanosilane coupling agents. Optionally, the reaction temperature is 60-80°C, and the reaction time is 2-4 hours. Optionally, the fourth drying temperature is 80-100°C, and the fourth drying time is 2-4 hours.

[0012] Optionally, the first slurry further includes a first solvent; optionally, the solid content of the first slurry is 30wt%~60wt%; optionally, the second slurry further includes a second solvent; optionally, the solid content of the second slurry is 40~50wt%; optionally, the preparation step of the third slurry includes: mixing the polymer dispersion and the first lithium salt suspension to perform a second dispersion; optionally, the volume ratio of the polymer dispersion to the first lithium salt suspension is 6~9:1~3; optionally, the solid content of the polymer dispersion is 10~20wt%; optionally, the solid content of the first lithium salt suspension is 15~45wt%; optionally, the electrolyte further includes a second lithium salt and an organic solvent.

[0013] Optionally, the temperature of the first drying is 60~80℃, and the drying time is 3~10min; Optionally, the temperature of the second drying is 60~80℃, and the drying time is 3~10min; Optionally, the temperature of the third drying is 80~120℃, and the drying time is 3~8min.

[0014] The beneficial technical effects of the present invention through the above technical solution are as follows: Other features and advantages of the present invention will be described in detail in the following detailed description section.

[0015] The battery provided by this invention features a separator and electrolyte that synergistically improve lithium-ion transport efficiency and suppress fast-charging side reactions, thereby enhancing the battery's fast-charging performance. One side of the separator is coated with a double-layer coating of boron nitride (BN) and a silane coupling agent-modified aluminum-based compound, improving the separator's high-temperature resistance. The other side is coated with a polymer layer containing lithium salt. The polyimide layer exhibits high thermal stability, as does the polymer itself. The addition of lithium salt further enhances the separator's stability under high-temperature conditions. The lithium salt also improves the separator's mechanical strength, making it more puncture-resistant and hindering lithium dendrite penetration. This double-layer coating arrangement comprehensively improves the separator's stability. A stable interface is formed between the silicon-based compound in the electrolyte and the coating on the separator, reducing interfacial impedance. This structure enhances the hydrophilicity of the separator surface, improving the wettability and uniformity of the electrolyte distribution. Detailed Implementation

[0016] This invention discloses a battery and its preparation method. Those skilled in the art can refer to the content of this document and appropriately modify the process parameters to achieve the desired result. It should be particularly noted that all similar substitutions and modifications are obvious to those skilled in the art and are considered to be included in this invention. The methods and applications of this invention have been described through preferred embodiments. Those skilled in the art can obviously make modifications or appropriate alterations and combinations to the methods and applications described herein without departing from the content, spirit, and scope of this invention to realize and apply the technology of this invention.

[0017] In the description of this invention, the list of items connected by the term "at least one of" or other similar terms may mean any combination of the listed items. For example, if items A and B are listed, then the phrase "at least one of A and B" means only A; only B; or A and B. In another example, if items A, B, and C are listed, then the phrase "at least one of A, B, and C" means only A; or only B; only C; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B, and C. Item A may contain a single element or multiple elements. Item B may contain a single element or multiple elements. Item C may contain a single element or multiple elements.

[0018] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges or individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0019] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0020] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0021] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0022] To address the problems of SEI film rupture, lithium dendrite growth, and poor thermal stability in existing electrolytes during high-rate fast charging, this invention adopts the following technical solution: The present invention provides a battery comprising a separator and an electrolyte. The separator comprises a base film, a first coating disposed on one side surface of the base film along the thickness direction, a second coating disposed on the side surface of the first coating away from the base film, and a third coating disposed on the other side surface of the base film along the thickness direction. The first coating comprises boron nitride; The second coating comprises a silane coupling agent modified aluminum-based compound; The third coating comprises a first lithium salt and a polymer; The electrolyte contains silicon-based compounds.

[0023] The separator and electrolyte in this invention work synergistically to solve problems such as SEI film rupture, lithium dendrite growth, and poor thermal stability that exist in electrolytes during high-rate fast charging. This improves lithium-ion transport efficiency and suppresses fast-charging side reactions, thereby enhancing the battery's fast-charging performance. In detail: One side of the base membrane is coated with a double-layer coating of boron nitride (BN) and a silane coupling agent-modified aluminum-based compound. In the first coating, boron nitride provides high thermal conductivity and chemical stability, while in the second coating, the aluminum-based compound provides mechanical strength and thermal stability. These two components work synergistically to significantly improve the membrane's high-temperature resistance. Furthermore, the silane coupling agent-modified aluminum-based compound enhances the membrane's mechanical properties and the adhesion of the aluminum-based compound, effectively preventing punctures and reducing coating peeling. The other side is coated with a lithium salt-containing polymer layer. The polymer exhibits high thermal stability, and the addition of lithium salt further enhances the membrane's stability under high-temperature conditions. The lithium salt also improves the membrane's mechanical strength, making it more puncture-resistant and hindering lithium dendrite penetration. This double-layer coating arrangement comprehensively improves the membrane's stability. A stable interface is formed between the silicon-based compound in the electrolyte and the coating on the membrane, reducing interfacial impedance. This structure enhances the hydrophilicity of the membrane surface, improving the wettability and uniformity of the electrolyte distribution.

[0024] The silane coupling agent modified aluminum-based compound used in this invention can form a stable interface between the diaphragm, the second coating and the electrolyte through chemical bonding, thereby reducing interfacial impedance, enhancing the hydrophilicity of the diaphragm surface and improving the wettability and distribution uniformity of the electrolyte.

[0025] In this invention, the side of the base film coated with the first and second coatings is bonded to the positive electrode, which can enhance the wettability of the electrolyte and reduce the resistance to lithium ion extraction; the side of the base film coated with the third coating is bonded to the negative electrode. The polymer has high thermal stability, and the addition of the first lithium salt further enhances the stability of the separator under high temperature conditions. The first lithium salt can also improve the mechanical strength of the separator, making it more puncture-resistant and preventing lithium dendrite puncture.

[0026] According to the present invention, the silicon-based compound includes, but is not limited to, silicon dioxide. In this invention, by adding silicon dioxide to the electrolyte, the ionic conductivity can be improved, thereby increasing the charge and discharge efficiency of the battery. Silicon dioxide can also act as a stabilizer in the electrolyte, reducing the decomposition of the electrolyte under high temperature or high pressure conditions and extending the battery's lifespan.

[0027] To enhance the synergistic effect between the separator and the electrolyte, during the battery formation process, a constant current charge-discharge cycle is performed three times at a low rate of 0.01C to 0.33C. This allows silicon-based compounds in the electrolyte to be directionally adsorbed onto the boron nitride surface of the separator, forming a SiO2-BN-LiF channel network. During charging, the negative charge on the SiO2 surface attracts lithium ions, which then travel along the alumina and BN double coating, forming a low-torsion transport path. During discharging, the LiF layer preferentially releases the stored Li+. + Replenish the negative electrode interface loss in a timely manner.

[0028] According to the present invention, the mass content of the silicon-based compound is 1% to 3% based on the total mass of the electrolyte. In this invention, a suitable content of the silicon-based compound helps to form a stable electrode / electrolyte interface film, improving the battery's cycle performance and high-temperature storage performance. As an example, based on the total mass of the electrolyte, the mass content of the silicon-based compound can be any value from 1%, 1.2%, 1.5%, 1.8%, 2%, 2.2%, 2.5%, 2.8%, and 3%, or any value within the range of any two of the above values. In this invention, if the mass content of the silicon-based compound is too high, it will lead to excessively high electrolyte viscosity, decreased ionic conductivity, and may increase unnecessary side reactions; if the mass content of the silicon-based compound is too low, it cannot effectively form ion channels, failing to achieve the effect of improving ionic conductivity.

[0029] According to the present invention, the thickness of the first coating is 1~3 μm. In this invention, the thickness of the first coating within a suitable range helps to fully utilize the high thermal conductivity and thermal stability of the BN material, effectively improving the high-temperature resistance of the separator and the thermal safety of the battery. As an example, the thickness of the first coating can be any value from 1 μm, 1.2 μm, 1.5 μm, 1.8 μm, 2 μm, 2.2 μm, 2.5 μm, 2.8 μm, and 3 μm, or any value within the range formed by any two of the above values. If the thickness of the first coating is too thin, it will lead to insufficient thermal management capability, and the separator will easily shrink at high temperatures, increasing the risk of battery short circuits; if the thickness of the first coating is too thick, it will lead to an increase in the overall thickness and internal resistance of the separator, which is detrimental to lithium-ion transport and reduces the rate performance of the battery.

[0030] According to the present invention, the thickness of the second coating is 1~3 μm. In this invention, the thickness of the second coating, within a suitable range, helps to utilize the excellent mechanical strength and electrolyte affinity of alumina to enhance the physical integrity of the separator and improve electrode interface compatibility. As an example, the thickness of the second coating can be any value from 1 μm, 1.2 μm, 1.5 μm, 1.8 μm, 2 μm, 2.2 μm, 2.5 μm, 2.8 μm, and 3 μm, or any value within the range formed by any two of the above values. If the thickness of the second coating is too thin, it will result in insufficient mechanical protection of the separator, making it difficult to effectively prevent dendrite puncture, and limiting the wetting effect on the electrolyte; if the thickness of the second coating is too thick, it will lead to a significant reduction in the porosity of the separator, hindering ion conduction, and may affect the long-term cycle stability of the battery due to coating detachment.

[0031] According to the present invention, the thickness of the third coating is 1~3 μm. In this invention, the thickness of the third coating, within a suitable range, helps to fully utilize the excellent thermal stability and mechanical strength of polyimide, while simultaneously utilizing lithium fluoride (LiF) to promote the formation of a stable, high-ionic-conductivity solid electrolyte interphase (SEI) film, thereby synergistically improving the overall heat resistance, puncture resistance, interfacial stability, and cycle life of the separator. As an example, the thickness of the third coating can be any value from 1 μm, 1.2 μm, 1.5 μm, 1.8 μm, 2 μm, 2.2 μm, 2.5 μm, 2.8 μm, and 3 μm, or any value within the range of any two of the above values. If the thickness of the third coating is too thin, the polyimide matrix will not be able to form a continuous and effective protective layer, resulting in insufficient mechanical reinforcement and thermal protection. Furthermore, a low LiF content will also make it difficult to effectively improve interfacial ion transport kinetics. If the thickness of the third coating is too thick, the total thickness and internal resistance of the separator will increase excessively, significantly hindering lithium-ion migration.

[0032] According to the present invention, the thickness of the base film is 5 to 11 μm. As an example, the thickness of the base film can be any value among 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, 8.5 μm, 9 μm, 9.5 μm, 10 μm, 10.5 μm, and 11 μm, or any value within the range formed by any pair of the above values.

[0033] According to the present invention, the base membrane includes, but is not limited to, polyolefin and / or ceramic membranes.

[0034] According to the present invention, the first coating further includes a first dispersant and a first binder. That is, the first coating includes boron nitride, a first dispersant, and a first binder.

[0035] According to the present invention, the mass ratio of boron nitride, the first dispersant, and the first binder is (80~95):(2~10):(3~10). As an example, the mass ratio of boron nitride, the first dispersant, and the first binder can be any value among 80:10:10, 85:7:8, 85:8:7, 88:6:6, 90:5:5, 92:3:5, 92:5:3, 95:2:3, and 95:3:2, or any value within the range of any pairwise values ​​mentioned above.

[0036] According to the present invention, the first dispersant includes, but is not limited to, polyvinylpyrrolidone and / or polyethylene glycol. That is, the first dispersant can be polyvinylpyrrolidone, polyethylene glycol, or a combination of polyvinylpyrrolidone and polyvinyl glycol. In the present invention, the first dispersant can prevent powder agglomeration.

[0037] According to the present invention, the first adhesive includes, but is not limited to, polyvinylidene fluoride and / or polyacrylic acid. That is, the first adhesive can be polyvinylidene fluoride, polyacrylic acid, or a combination of polyvinylidene fluoride and polyacrylic acid. In the present invention, the first adhesive can enhance the adhesion between the coating and the base film.

[0038] According to the present invention, the second coating further includes a second dispersant and a second binder. That is, the second coating includes a silane coupling agent modified aluminum-based compound, a second dispersant, and a second binder.

[0039] According to the present invention, the mass ratio of the silane coupling agent modified aluminum-based compound, the second dispersant, and the second binder is (75~95):(2~15):(3~15). As an example, the mass ratio of the silane coupling agent modified aluminum-based compound, the second dispersant, and the second binder can be any value among 75:15:15, 80:5:10, 80:10:5, 85:7:8, 85:8:7, 90:10:10, 95:2:3, and 95:3:2, or any value within the range of any pair of the above values.

[0040] According to the present invention, the aluminum-based compound includes, but is not limited to, aluminum oxide.

[0041] According to the present invention, the second dispersant includes, but is not limited to, at least one of sodium polyacrylate, polyethylene oxide, and polyethylene glycol.

[0042] According to the present invention, the second adhesive includes, but is not limited to, acrylates and / or polyvinylidene fluoride. That is, the second adhesive can be acrylate, can be polyvinylidene fluoride, or can be both acrylate and polyvinylidene fluoride.

[0043] According to the present invention, the total mass of the first lithium salt and the polymer is used as a basis, and the mass content of the first lithium salt is 20% to 40%. In this invention, a suitable mass content of the first lithium salt helps to construct efficient lithium-ion transport channels in the polymer matrix while maintaining good film-forming properties and mechanical strength of the composite electrolyte layer. As an example, based on the total mass of the first lithium salt and the polymer, the mass content of the first lithium salt can be any value from 20%, 22%, 24%, 25%, 26%, 28%, 30%, 32%, 34%, 35%, 38%, and 40%, or any value within the range of any two of the above values. If the mass content of the first lithium salt is too high, it will cause the polymer matrix to be damaged by excessive salt grains, resulting in decreased density and deterioration of mechanical properties. Furthermore, excessively high lithium salt content may trigger interfacial side reactions, affecting the battery's cycle stability. If the mass content of the first lithium salt is too low, it will result in insufficient lithium-ion conduction pathways, significantly reduced ionic conductivity, and failure to meet the ion transport requirements for normal battery operation.

[0044] According to the present invention, the first lithium salt includes, but is not limited to, lithium fluoride and / or lithium aluminate. That is, the first lithium salt can be lithium fluoride, lithium aluminate, or a combination of lithium fluoride and lithium aluminate.

[0045] According to the present invention, the polymer includes, but is not limited to, polyimide and / or polyetheretherketone. That is, the polymer can be polyimide, polyetheretherketone, or a combination of both.

[0046] According to the present invention, the electrolyte further comprises a second lithium salt and an organic solvent. That is, the electrolyte comprises a silicon-based compound, a second lithium salt, and an organic solvent.

[0047] According to the present invention, the concentration of the second lithium salt in the electrolyte is 1 to 3 mol / L. According to the present invention, the concentration of the second lithium salt in the electrolyte within a suitable range helps to provide sufficient free lithium ions, ensures high ionic conductivity of the electrolyte, and promotes the formation of a stable interfacial film with high ionic conductivity on the electrode surface. As an example, the concentration of the second lithium salt in the electrolyte can be any value selected from 1 mol / L, 1.2 mol / L, 1.4 mol / L, 1.5 mol / L, 1.6 mol / L, 1.8 mol / L, 2 mol / L, 2.2 mol / L, 2.4 mol / L, 2.5 mol / L, 2.6 mol / L, 2.8 mol / L, and 3 mol / L, or any value within the range formed by any two of the above values. If the concentration of the second lithium salt in the electrolyte is too high, it will lead to a significant increase in electrolyte viscosity, a decrease in lithium ion mobility, and an exacerbation of the decomposition side reaction of lithium salt on the electrode surface, while also increasing costs. If the concentration of the second lithium salt in the electrolyte is too low, it will lead to insufficient electrolyte ionic conductivity, increased battery internal resistance, poor rate performance, and difficulty in forming an effective interface protective layer.

[0048] According to the present invention, the second lithium salt includes, but is not limited to, at least one of lithium fluorophosphate, lithium bis(fluorosulfonyl)imide, and lithium bis(trifluoromethanesulfonyl)imide.

[0049] According to the present invention, the organic solvent includes, but is not limited to, at least one of ethylene carbonate, propylene carbonate, dimethyl carbonate, ethyl methyl carbonate, and diethyl carbonate.

[0050] A second aspect of the present invention provides a method for preparing a battery, comprising the following steps: The first slurry is coated on one side surface of the base film along the thickness direction, and then dried to obtain a base film with the first coating. The second slurry is coated onto the surface of the first coating away from the base film, and then dried to obtain a base film with the second coating. The third slurry is coated onto the other side of the base film with the second coating along the thickness direction, and then dried in the third stage to obtain a diaphragm; The diaphragm, positive electrode, negative electrode, and electrolyte containing silicon-based compounds are assembled. The first slurry includes boron nitride; The second slurry includes a silane coupling agent-modified aluminum-based compound; The third slurry includes a first lithium salt and a polymer.

[0051] The battery preparation method of this invention mainly includes sequentially coating a slurry containing boron nitride, a silane coupling agent-modified aluminum-based compound, a first lithium salt, and a polymer onto a base membrane to prepare a separator; assembling the separator, positive and negative electrodes, and an electrolyte containing a silicon-based compound to obtain the battery. This preparation method is simple and easy to operate. Furthermore, the fast-charging performance of the battery is improved through the combined action of the separator structure system and the electrolyte.

[0052] According to the present invention, the preparation of the silane coupling agent modified aluminum-based compound includes the following steps: The aluminum-based compound and silane coupling agent solution are mixed, dispersed in the first stage, reacted, and dried in the fourth stage.

[0053] According to the present invention, the preparation of the silane coupling agent solution includes: The silane coupling agent and solvent are mixed, and a catalyst is added to adjust the pH to acidic before dispersion. Solvents include, but are not limited to, water and ethanol solutions; The concentration of the ethanol solution is 70wt% to 95wt%. As an example, the concentration of the ethanol solution can be any value from 70wt%, 71wt%, 72wt%, 75wt%, 76wt%, 78wt%, 80wt%, 82wt%, 84wt%, 85wt%, 88wt%, 90wt%, 91wt%, 92wt%, and 95wt%, or any value within the range formed by any pair of the above values; The mass ratio of silane coupling agent to solvent is 1:9 to 20. As an example, the mass ratio of silane coupling agent to solvent can be any value from 1:9, 1:10, 1:11, 1:12, 1:13, 1:14, 1:15, 1:16, 1:17, 1:18, 1:19 and 1:20, or any value within the range of any two of the above values. Catalysts, including but not limited to one or more of acetic acid, acetic acid, and nitric acid; The target pH value is 4 to 5. For example, the target pH value can be any value among 4, 4.1, 4.2, 4.5, 4.8 and 5, or any value within the range of any two of the above values.

[0054] In this invention, the chemical equations involved in the modification of aluminum-based compounds with silane coupling agents are as follows: (1) R-Si(OR')3+ 3H2O → R-Si(OH)3+ 3ROH; (2) R-Si(OH)3+ Al-OH→R-Si-O-Al +2H2O.

[0055] In this invention, the alkoxy group of the silane coupling agent undergoes a hydrolytic condensation reaction with the hydroxyl groups on the surface of aluminum-based compounds such as alumina to form Si-O-Al bonds. The silanol group (Si-OH) of the silane coupling agent can react with silicon-based compounds such as silica particles in the electrolyte to form Si-O-Si bonds. The reaction equation is R-Si(OH)3 + Si-OH → R-Si-O-Si + H2O. This reaction can occur under natural conditions, but the reaction rate is slow. During high-rate charging of fast-charging batteries, the temperature rise inside the battery increases, and the increased temperature accelerates this reaction. Through chemical bonding, the silane coupling agent can form a stable interface between the separator, the second coating, and the electrolyte, reducing interfacial impedance. This structure enhances the hydrophilicity of the separator surface and improves the wettability and distribution uniformity of the electrolyte.

[0056] According to the present invention, the mass ratio of the aluminum-based compound to the silane coupling agent solution is 10-15:1; the concentration of the silane coupling agent solution is 0.005-0.02 mol / L. In this invention, the suitable mass ratio of the aluminum-based compound to the silane coupling agent helps to effectively improve the dispersion stability and interfacial compatibility of the silane coupling agent in the polymer matrix. As an example, the mass ratio of the aluminum-based compound to the silane coupling agent can be any value from 10:1, 10.5:1, 11:1, 11.5:1, 12:1, 12.5:1, 13:1, 13.5:1, 14:1, 14.5:1, and 15:1, or any value within the range of any two of the above values; the concentration of the silane coupling agent solution can be any value from 0.005 mol / L, 0.008 mol / L, 0.01 mol / L, 0.012 mol / L, 0.015 mol / L, 0.018 mol / L, and 0.2 mol / L, or any value within the range of any two of the above values. If the mass ratio of aluminum-based compound to silane coupling agent is too high, it will result in a relative deficiency of silane coupling agent, incomplete surface modification of alumina, and some particles will easily agglomerate due to lack of modification, reducing the dispersion uniformity in the composite coating. If the mass ratio of aluminum-based compound to silane coupling agent is too low, it will result in an excess of silane coupling agent. Unreacted coupling agent molecules are prone to self-condensation to form gels or physical adsorption on the particle surface, introducing insulating impurities and deteriorating interfacial ion transport performance.

[0057] Optionally, the aluminum-based compound includes, but is not limited to, aluminum oxide.

[0058] Optionally, the silane coupling agent in the silane coupling agent solution includes, but is not limited to, at least one of aminosilane coupling agents, mercaptosilane coupling agents, epoxysilane coupling agents, vinylsilane coupling agents, and cyanosilane coupling agents.

[0059] According to the present invention, the reaction temperature is 60~80°C, and the reaction time is 2~4h. As an example, the reaction temperature can be any value from 60°C, 62°C, 65°C, 68°C, 70°C, 72°C, 75°C, 78°C, and 80°C, or any value within the range formed by any two of the above values. The reaction time can be any value from 2h, 2.25h, 2.5h, 2.75h, 3h, 3.25h, 3.5h, 3.75h, and 4h, or any value within the range formed by any two of the above values.

[0060] According to the present invention, the temperature of the fourth drying is 80~100℃, and the time of the fourth drying is 2~4h. As an example, the temperature of the fourth drying can be any value among 80℃, 82℃, 85℃, 86℃, 88℃, 90℃, 92℃, 94℃, 95℃, 98℃, and 100℃, or any value within the range formed by any two of the above values, and the time of the fourth drying can be any value among 2h, 2.25h, 2.5h, 2.75h, 3h, 3.25h, 3.5h, 3.75h, and 4h, or any value within the range formed by any two of the above values.

[0061] According to the present invention, the first slurry further includes a first solvent.

[0062] According to the present invention, the solid content of the first slurry is 30wt% to 60wt%. As an example, the solid content of the first slurry can be any value among 30wt%, 35wt%, 40wt%, 45wt%, 50wt%, 55wt%, and 60wt%, or any value within the range of any pair of the above values.

[0063] According to the present invention, the second slurry further includes a second solvent.

[0064] According to the present invention, the solid content of the second slurry is 40 to 50 wt%. As an example, the solid content of the second slurry can be any value among 40 wt%, 41 wt%, 42 wt%, 43 wt%, 45 wt%, 46 wt%, 48 wt%, 49 wt%, and 50 wt%, or any value within the range of any pair of the above values.

[0065] According to the present invention, the preparation step of the third slurry includes: mixing the polymer dispersion and the first lithium salt suspension to perform a second dispersion.

[0066] According to the present invention, the volume ratio of the polymer dispersion to the first lithium salt suspension is 6 to 9:1 to 3. As an example, the volume ratio of the polymer dispersion to the first lithium salt suspension can be any value among 6:1, 7:2, 8:2.5, 9:3, 9:2, and 9:1, or any value within the range of any two of the above values.

[0067] According to the present invention, the solid content of the polymer dispersion is 10 to 20 wt%. As an example, the solid content of the polymer dispersion can be any value among 10 wt%, 11 wt%, 12 wt%, 13 wt%, 14 wt%, 15 wt%, 16 wt%, 17 wt%, 18 wt%, 19 wt%, and 20 wt%, or any value within the range formed by any pair of the above values.

[0068] According to the present invention, the solid content of the first lithium salt suspension is 15 to 45 wt%. As an example, the solid content of the first lithium salt suspension can be any value from 15 wt%, 18 wt%, 20 wt%, 22 wt%, 25 wt%, 28 wt%, 30 wt%, 32 wt%, 35 wt%, 38 wt%, 40 wt%, 42 wt%, and 45 wt%, or any value within the range formed by any pair of the above values.

[0069] According to the present invention, the electrolyte further includes a second lithium salt and an organic solvent.

[0070] According to the present invention, the temperature of the first drying is 60~80°C, and the time of the first drying is 3~10 min. As an example, the temperature of the first drying can be any value among 60°C, 62°C, 65°C, 68°C, 70°C, 72°C, 75°C, 78°C, and 80°C, or any value within the range formed by any two of the above values, and the time of the first drying can be any value among 3 min, 4 min, 5 min, 6 min, 7 min, 8 min, 9 min, and 10 min, or any value within the range formed by any two of the above values.

[0071] According to the present invention, the temperature of the second drying is 60~80°C, and the time of the second drying is 3~10 min. As an example, the temperature of the second drying can be any value among 60°C, 62°C, 65°C, 68°C, 70°C, 72°C, 75°C, 78°C, and 80°C, or any value within the range formed by any two of the above values, and the time of the second drying can be any value among 3 min, 4 min, 5 min, 6 min, 7 min, 8 min, 9 min, and 10 min, or any value within the range formed by any two of the above values.

[0072] According to the present invention, the temperature of the third drying is 80~120°C, and the time of the third drying is 3~8 min. As an example, the temperature of the third drying can be any value among 80°C, 82°C, 85°C, 88°C, 90°C, 92°C, 95°C, 98°C, 100°C, 105°C, 110°C, 115°C, and 120°C, or any value within the range formed by any two of the above values, and the time of the second drying can be any value among 3 min, 4 min, 5 min, 6 min, 7 min, and 8 min, or any value within the range formed by any two of the above values.

[0073] The present invention will be further described in detail below through examples. All raw materials used in the examples are commercially available.

[0074] Example 1 The manufacturing process of batteries includes: (1) Preparation of the diaphragm, including the following steps: Boron nitride powder was dispersed in deionized water, and dispersant polyvinylpyrrolidone and binder polyvinylidene fluoride were added. The mass ratio of boron nitride powder, dispersant and binder was 85:6:9. The mixture was ultrasonically treated at 500W for 35 minutes to form a stable first slurry with a solid content of 45wt%. The first slurry was coated on one side of a polypropylene (PP) base film along the thickness direction at a coating speed of 2m / min, and then dried at 80℃ for 5 minutes to form a first coating with a thickness of 2μm. A silane coupling agent and a 95wt% ethanol solution were mixed at a ratio of 1:9. Acetic acid was added as a catalyst to adjust the pH to 5, and the mixture was dispersed for 30 min to obtain a silane coupling agent solution. Alumina was added to a 0.01mol / L silane coupling agent solution at a mass ratio of 15:1. The mixture was stirred and dispersed for 2 h, and then reacted at 80 °C for 4 h. After the reaction, the resulting product was dried at 100 °C for 4 h to obtain a silane coupling agent modified aluminum-based compound. The silane coupling agent modified aluminum-based compound, sodium polyacrylate dispersant, and polyvinylidene fluoride binder prepared in the preparation example were mixed at a mass ratio of 86:6:8 and dispersed in deionized water. The mixture was ultrasonically treated at 500W for 50 min to form a stable second slurry with a solid content of 45wt%. The second slurry was coated onto the surface of the first coating away from the PP base film at a coating speed of 2 m / min, and then dried at 70 °C for 5 min to form a second coating with a thickness of 2 μm. A polyimide dispersion with a solid content of 15 wt% and a LiF suspension with a solid content of 25 wt% were mixed at a volume ratio of 9:1 to obtain a third slurry. The third slurry was coated on the other side of the PP base film along the thickness direction at a coating speed of 5 m / s, and then dried at 110 °C for 3 min to form a third coating with a thickness of 3 μm to obtain a diaphragm.

[0075] (2) Preparation of the negative electrode sheet, including the following steps: The prepared negative electrode active material (graphite), conductive agent (conductive carbon black) and binder (CMC) are mixed in a mass ratio of 90:2:8 to obtain a mixed material. The mixed material is thoroughly stirred in deionized water to obtain a negative electrode slurry. The obtained slurry is coated on conventional copper foil, and after drying and rolling, a negative electrode active material layer with a thickness of 120μm is formed on the copper foil to obtain a negative electrode sheet.

[0076] (3) Preparation of the positive electrode sheet, including the following steps: The positive electrode active material (lithium iron phosphate), conductive agent (conductive carbon black), and binder (PVDF) are mixed in a mass ratio of 95:3:2 to obtain a mixed material. The mixed material is thoroughly stirred in NMP to obtain a positive electrode slurry. The obtained slurry is coated on conventional aluminum foil, and after drying and rolling, a positive electrode active material layer with a thickness of 170 μm is formed on the aluminum foil to obtain the positive electrode sheet.

[0077] (4) Preparation of electrolyte, including the following steps: Ethylene carbonate (EC) and dimethyl carbonate (DMC) were mixed in a volume ratio of 1:1. Then, fully dried lithium salt LiPF6 was dissolved in the mixed organic solvent at a ratio of 1 mol / L to prepare an electrolyte. 1.4 wt% silicon dioxide (SiO2) was added to the electrolyte.

[0078] (5) Battery assembly, including the following steps: After weighing, the electrode sheets are directly used as the negative electrode of the lithium-ion battery. The assembly of the 2032 button cell is carried out in a glove box filled with Ar. The assembly sequence of the battery from top to bottom is: negative electrode shell, gasket, pad, lithium sheet, separator, self-supporting electrode sheet, positive electrode shell, resulting in the battery.

[0079] Example 2 The battery fabrication process differs from that in Example 1 in the following ways: The volume ratio of polyimide dispersion to LiF suspension is 9:2.

[0080] Everything else is the same as in Example 1.

[0081] Example 3 The battery fabrication process differs from that in Example 1 in the following ways: The volume ratio of polyimide dispersion to LiF suspension is 8:2.

[0082] Everything else is the same as in Example 1.

[0083] Example 4 The battery fabrication process differs from that in Example 1 in the following ways: The volume ratio of polyimide dispersion to LiF suspension is 6:4.

[0084] Everything else is the same as in Example 1.

[0085] Example 5 The battery fabrication process differs from that in Example 1 in the following ways: The mass ratio of boron nitride powder, dispersant, and binder is 88:6:6.

[0086] Everything else is the same as in Example 1.

[0087] Example 6 The battery fabrication process differs from that in Example 1 in the following ways: The mass ratio of boron nitride powder, dispersant, and binder is 90:3:7.

[0088] Everything else is the same as in Example 1.

[0089] Example 7 The battery fabrication differs from that in Example 1 in that: The mass ratio of silane coupling agent to ethanol solution is 64:36.

[0090] Everything else is the same as in Example 1.

[0091] Example 8 The battery fabrication differs from that in Example 1 in that: The mass ratio of silane coupling agent to ethanol solution is 8:2.

[0092] Everything else is the same as in Example 1.

[0093] Example 9 The battery fabrication differs from that in Example 1 in that: The thickness of the first coating is 1 μm.

[0094] Everything else is the same as in Example 1.

[0095] Example 10 The battery fabrication differs from that in Example 1 in that: The thickness of the first coating is 3 μm.

[0096] Everything else is the same as in Example 1.

[0097] Example 11 The battery fabrication differs from that in Example 1 in that: The thickness of the second coating is 1 μm.

[0098] Everything else is the same as in Example 1.

[0099] Example 12 The battery fabrication differs from that in Example 1 in that: The thickness of the second coating is 3 μm.

[0100] Everything else is the same as in Example 1.

[0101] Comparative Example 1 The battery fabrication differs from that in Example 1 in that: There is no third coating in the diaphragm.

[0102] Everything else is the same as in Example 1.

[0103] Comparative Example 2 The battery fabrication differs from that in Example 1 in that: There is no first coating and a second coating in the diaphragm.

[0104] Everything else is the same as in Example 1.

[0105] Comparative Example 3 The battery fabrication differs from that in Example 1 in that: Preparation of electrolyte: Ethylene carbonate (EC) and dimethyl carbonate (DMC) were mixed at a volume ratio of 1:1. Then, fully dried lithium salt LiPF6 was dissolved in the mixed organic solvent at a ratio of 1 mol / L to prepare the electrolyte.

[0106] Everything else is the same as in Example 1.

[0107] Test case (1) Internal resistance test: The internal resistance of different groups of batteries is obtained by using a battery internal resistance meter.

[0108] (2) Ratio performance test: ① Calibration of battery initial capacity (rated capacity C0) Allow the battery to stand at 25°C for at least 1 hour to stabilize its temperature. Charge it at a constant current of 1C until it reaches the upper limit cutoff voltage (typically 3.65V). Switch to constant voltage charging until the charging current decreases to 0.05C. After charging is complete, allow it to stand for 30 minutes. Discharge it at a constant current of 1C until it reaches the lower limit cutoff voltage of 2.2V. Record the total capacity of this discharge; this is the battery's initial rated capacity C0.

[0109] ②4C discharge capacity retention test Fully charge the battery using the same constant current and constant voltage method as in "Step ①". Let it rest for 30 minutes. Discharge at a constant current of 4C until the lower cutoff voltage of 2.2V is reached. Record the total discharge capacity as C4C (initial). Perform continuous charge-discharge cycles on the battery. The cycle procedure is to charge at a constant current and constant voltage of 1C. Let it rest for 5 minutes. Discharge at a constant current of 4C until the cutoff voltage of 2.2V is reached. Let it rest for 5-10 minutes. After 500 cycles, record the current 4C discharge capacity C4C.

[0110] ③ Calculate the capacity retention rate after 500 cycles. 4C discharge capacity retention (%) = (C4C, / C4C, initial) × 100% (3) Battery energy density test: First, weigh the battery and record the weight as m. Then, at 25°C, charge the battery at a constant current of 0.33C to 3.65V, and then charge it at a constant voltage of 3.65V until the current is ≤0.05C. After standing for 5 minutes, discharge it at a constant current of 0.33C to 2.0V to obtain the discharge energy Q. The battery energy density is calculated as Q / m.

[0111] (4) Thermal response test of the separator (testing the porosity of the separator at 60℃ and 120℃ respectively): Cut at least 3 representative circular or square samples from the separator to be tested. Place the samples in a vacuum drying oven and vacuum dry at 60 (120)℃ for more than 2 hours to completely remove moisture and residual solvent. Transfer the dried samples to a desiccator to cool to room temperature (about 20-25℃). Weigh each dried sample in air and record it as m1 (unit: g). Turn on the high temperature constant temperature chamber and density measuring device to heat and stabilize the impregnation liquid at 60 (120) ± 2℃. Carefully immerse the dried and weighed (m1) sample into the impregnation liquid at 60 (120)℃. To ensure that the impregnation liquid completely fills the pores of the separator, evacuate the container containing the sample and impregnation liquid and keep it for 5-10 minutes until no bubbles overflow. Using a special stand for the high-temperature densitometer, completely immerse the sample, already saturated with the impregnation solution, in a 60 (120)°C impregnation solution (high-boiling-point silicone oil) (but without contacting the container walls and bottom). After the reading stabilizes, record the mass at this point as m² (unit: g). This is equivalent to the buoyancy force experienced by the saturated sample in the high-temperature impregnation solution. Take the average of the test results of at least three parallel samples as the final reported value, noting that the test temperature was 120°C.

[0112] Calculate apparent density (ρ) a ): ρ a = (m1 / (m1- m2)) × ρli q ρ a Apparent density of the sample at 60 (120) °C (g / cm³) 3 m1: Mass of the dried sample in air (g); m2: Apparent mass of the saturated sample in the impregnation solution (g); ρ li q: Density of the impregnation solution at 60 (120) °C (g / cm³) Calculate porosity (P, %): P = (1 - ρ a / ρ i ) × 100% P: Porosity of the sample (%); ρ a : Calculated apparent density (g / cm³) 3 );ρ i : Spatial density of membrane material (g / cm³) 3 ), the ρ of polypropylene (PP) i It is 0.91 g / cm 3 The content of polyethylene (PE) is 0.96 g / cm³. 3 .

[0113] Table 1 Based on the test results of the examples and comparative examples, the coated separator prepared in Example 1 using the optimal reactant ratio achieved a capacity retention rate of 90% for the battery under a 4C high-rate charge-discharge cycle, thus improving the battery's fast-charging performance.

[0114] The ratio of reactants affects the content of the base layer and coating, influencing electron transport and consequently the battery's rate capability and cycle performance. Silica can reduce the surface tension of the electrolyte, making it easier to spread on the electrode material surface, thereby increasing the contact area between the electrode and the electrolyte and promoting ion transport. A stable interface is formed between silica and the coating on the separator, reducing interfacial impedance. This structure enhances the hydrophilicity of the separator surface, improving the wettability and uniformity of electrolyte distribution.

[0115] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A battery, characterized in that, The battery includes a separator and an electrolyte. The separator includes a base film, a first coating disposed on one side surface of the base film along the thickness direction, a second coating disposed on the side surface of the first coating away from the base film, and a third coating disposed on the other side surface of the base film along the thickness direction. The first coating comprises boron nitride; The second coating comprises a silane coupling agent modified aluminum-based compound; The third coating comprises a first lithium salt and a polymer; The electrolyte contains silicon-based compounds.

2. The battery according to claim 1, characterized in that, The silicon-based compound includes silicon dioxide; Optionally, the mass content of the silicon-based compound is 1% to 3% based on the total mass of the electrolyte.

3. The battery according to claim 1, characterized in that, The thickness of the first coating is 1~3μm; and / or, The thickness of the second coating is 1~3μm; and / or, The thickness of the third coating is 1~3μm; and / or, The thickness of the base film is 5~11μm; Optionally, the base membrane comprises a polyolefin and / or a ceramic membrane.

4. The battery according to claim 1, characterized in that, The first coating also includes a first dispersant and a first binder; Optionally, the mass ratio of the boron nitride, the first dispersant, and the first binder is (80~95):(2~10):(3~10). Optionally, the first dispersant comprises polyvinylpyrrolidone and / or polyethylene glycol; Optionally, the first adhesive comprises polyvinylidene fluoride and / or polyacrylic acid; and / or, The second coating also includes a second dispersant and a second binder; Optionally, the mass ratio of the silane coupling agent modified aluminum-based compound, the second dispersant, and the second binder is (75~95):(2~15):(3~15); Optionally, the aluminum-based compound includes aluminum oxide; Optionally, the second dispersant includes at least one of sodium polyacrylate, polyethylene oxide, and polyethylene glycol; Optionally, the second adhesive comprises acrylate and / or polyvinylidene fluoride.

5. The battery according to claim 1, characterized in that, Based on the total mass of the first lithium salt and the polymer, the mass content of the first lithium salt is 20% to 40%; Optionally, the first lithium salt includes lithium fluoride and / or lithium aluminate; Optionally, the polymer includes polyimide and / or polyetheretherketone.

6. The battery according to claim 1, characterized in that, The electrolyte also includes a second lithium salt and an organic solvent; Optionally, the concentration of the second lithium salt in the electrolyte is 1~3 mol / L; Optionally, the second lithium salt includes at least one of lithium fluorophosphate, lithium bis(fluorosulfonyl)imide, and lithium bis(trifluoromethanesulfonyl)imide; Optionally, the organic solvent includes at least one of ethylene carbonate, propylene carbonate, dimethyl carbonate, ethyl methyl carbonate, and diethyl carbonate.

7. A method for preparing a battery, characterized in that, Includes the following steps: The first slurry is coated on one side surface of the base film along the thickness direction, and the first drying is performed to obtain a base film with the first coating. The second slurry is coated onto the surface of the first coating away from the base film, and then dried to obtain a base film with the second coating. The third slurry is coated onto the other side of the base film with the second coating along the thickness direction, and then dried in the third stage to obtain a diaphragm; The diaphragm, positive electrode, negative electrode, and electrolyte containing silicon-based compounds are assembled. The first slurry includes boron nitride; The second slurry includes a silane coupling agent-modified aluminum-based compound; The third slurry includes a first lithium salt and a polymer.

8. The preparation method according to claim 7, characterized in that, The preparation of the silane coupling agent modified aluminum-based compound includes the following steps: The aluminum-based compound and the silane coupling agent solution are mixed, dispersed in the first stage, reacted, and dried in the fourth stage. Optionally, the mass ratio of the aluminum-based compound to the silane coupling agent solution is 10-15:1; Optionally, the concentration of the silane coupling agent solution is 0.005~0.02 mol / L; Optionally, the aluminum-based compound includes aluminum oxide; Optionally, the silane coupling agent in the silane coupling agent solution includes at least one of aminosilane coupling agents, mercaptosilane coupling agents, epoxysilane coupling agents, vinylsilane coupling agents, and cyanosilane coupling agents; Optionally, the reaction temperature is 60~80℃, and the reaction time is 2~4h; Optionally, the temperature of the fourth drying step is 80~100℃, and the drying time is 2~4h.

9. The preparation method according to claim 7, characterized in that, The first slurry also includes a first solvent; Optionally, the solid content of the first slurry is 30wt%~60wt%; and / or, The second slurry also includes a second solvent; Optionally, the solid content of the second slurry is 40-50 wt%; and / or, The preparation steps of the third slurry include: The polymer dispersion and the first lithium salt suspension are mixed for a second dispersion. Optionally, the volume ratio of the polymer dispersion to the first lithium salt suspension is 6~9:1~3; Optionally, the solid content of the polymer dispersion is 10-20 wt%. Optionally, the solid content of the first lithium salt suspension is 15-45 wt%; and / or, The electrolyte also includes a second lithium salt and an organic solvent.

10. The preparation method according to claim 7, characterized in that, The first drying temperature is 60~80℃, and the first drying time is 3~10 min; and / or, The second drying temperature is 60~80℃, and the second drying time is 3~10 min; and / or, The temperature of the third drying step is 80~120℃, and the drying time is 3~8 minutes.

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