Slurry and preparation method thereof, diaphragm and battery cell

Abstract

The invention provides slurry and a preparation method thereof, a diaphragm and a battery cell, the slurry comprises the following components in parts by mass: 20-35 parts of multi-component carbides, 2.5-4.5 parts of a binding material and 65-75 parts of a solvent, and the multi-component carbides comprise at least two of a titanium element, a zirconium element, a niobium element, a tantalum element and a hafnium element; according to the present invention, the multi-element carbide is added to the slurry, and the multi-element carbide comprises at least two of the titanium element, the zirconium element, the niobium element, the tantalum element and the hafnium element, such that the high hardness and the high temperature resistance are provided compared to the aluminum oxide, and the anti-puncture strength of the cell can be improved by applying the slurry to the diaphragm; therefore, the technical problem of over-high temperature rise caused by short circuit due to extrusion and needling of the battery cell is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and particularly relates to a slurry and its preparation method, a separator, and an electric core. Background Art

[0002] The separator is a key component of a lithium battery, which can effectively prevent short circuits between the positive and negative electrodes inside the battery. At the same time, the separator also helps to provide thermal stability for the lithium battery.

[0003] In related technologies, an alumina coating is usually provided on the surface of the separator. The alumina coating can ensure the integrity of the separator at a high temperature of 180°C, significantly improving the thermal stability of the lithium-ion battery.

[0004] However, during use, the separator may be subjected to external mechanical pressure or puncture by a sharp object, resulting in a short circuit between the positive and negative electrodes of the electric core. Therefore, the separator needs to have sufficient puncture resistance to prevent short circuits between the positive and negative electrodes caused by the above situations. Summary of the Invention

[0005] Embodiments of the present invention provide a slurry and its preparation method, a separator, and an electric core, which can solve the technical problem of short circuits between the positive and negative electrodes caused by puncture of the separator.

[0006] In a first aspect, embodiments of the present invention provide a slurry. By mass, the slurry includes:

[0007] 20 parts to 35 parts of a multi-component carbide;

[0008] 2.5 parts to 4.5 parts of a binder;

[0009] 65 parts to 75 parts of a solvent;

[0010] wherein, the multi-component carbide includes at least two of titanium, zirconium, niobium, tantalum, and hafnium.

[0011] In one embodiment, based on 100% of the total mass of the slurry, the slurry includes 20% to 35% of the multi-component carbide, 2.5% to 4.5% of the binder, and the balance is the solvent.

[0012] In one embodiment, the multi-component carbide includes a combination of any two of titanium, zirconium, niobium, tantalum, and hafnium; and / or

[0013] the multi-component carbide includes any one of titanium-zirconium-carbon, titanium-niobium-carbon, and titanium-hafnium-carbon;

[0014] Preferably, the mass ratio of titanium:zirconium:carbon in the multi-component carbide is (1 - 1.5):(1 - 1.5):2.

[0015] In one embodiment, the average particle size of the multi-component carbide is 100 nm to 500 nm;

[0016] Preferably, the average particle size of the multi-component carbide is 100 nm to 350 nm.

[0017] In one embodiment, the bonding material includes one or more combinations of polyvinylidene fluoride, polyvinyl alcohol, and polytetrafluoroethylene; and / or

[0018] The solvent includes at least one of N-methylpyrrolidone and N,N-dimethylformamide.

[0019] In one embodiment, the solid content of the bonding material is 5% to 15%; and / or

[0020] The solid content of the slurry is 25% to 35%.

[0021] In a second aspect, an embodiment of the present invention provides a method for preparing a slurry, which is used to prepare the aforementioned slurry, and the preparation method comprises the following steps:

[0022] Provide multicomponent carbides, bonding materials and solvents;

[0023] The multi-component carbide, the bonding material and the solvent are stirred and mixed to prepare a slurry.

[0024] In one embodiment, the multi-component carbide is prepared by the following steps:

[0025] Placing multiple metal elements and carbon powder in a reaction container, heating them under an inert atmosphere to react, and obtaining a multiphase solid solution;

[0026] The multiphase solid solution is cooled and ground to obtain multi-component carbides;

[0027] The plurality of metal elements include at least two of metal element titanium, metal element zirconium, metal element niobium, metal element tantalum, and metal element hafnium;

[0028] Preferably, the plurality of metal elements include any two of metal element titanium, metal element zirconium, metal element niobium, metal element tantalum, and metal element hafnium;

[0029] Preferably, the plurality of metal elements include metal element titanium and metal element zirconium.

[0030] In one embodiment, the inert atmosphere includes any one of a nitrogen atmosphere, an argon atmosphere, a neon atmosphere, a helium atmosphere, a xenon atmosphere or a krypton atmosphere, or a combination of at least two thereof; and / or

[0031] The temperature range of the heating is 1500° C. to 2000° C.; and / or

[0032] The cooling includes cooling to room temperature in a natural cooling manner; and / or

[0033] The cooling includes cooling to room temperature at a cooling rate of 4°C to 20°C / h; and / or

[0034] The grinding includes ball-milling the cooled multiphase solid solution for 9 h to 12 h, and the diameter of the ball-milling medium is 0.5 cm to 1 cm.

[0035] In one embodiment, stirring and mixing the multi-component carbide, the binder material and the solvent includes:

[0036] First, dissolving the binder material in a part of the solvent to obtain a glue solution with a solid content of 5% to 15%;

[0037] Dissolving the multi-component carbide and the glue solution in the remaining solvent, and stirring and mixing to obtain a slurry.

[0038] In a third aspect, an embodiment of the present invention provides a separator, which includes:

[0039] A base film;

[0040] A protective layer, disposed on one or both sides of the base film;

[0041] Wherein, the protective layer includes a multi-component carbide;

[0042] The multi-component carbide includes at least two metal elements among titanium element, zirconium element, niobium element, tantalum element, and hafnium element.

[0043] In one embodiment, the thickness of the protective layer ranges from 1 μm to 5 μm.

[0044] In a fourth aspect, an embodiment of the present invention provides a method for preparing a separator for preparing the foregoing separator, and the preparation method includes the following steps:

[0045] Providing a base film;

[0046] Preparing a slurry with a multi-component carbide, a binder material and a solvent;

[0047] Coating the slurry on the base film to form a protective layer to obtain the separator.

[0048] In a fifth aspect, an embodiment of the present invention provides an electric core, including the foregoing separator or a separator prepared by the foregoing method for preparing a separator.

[0049] The beneficial effects of the embodiments of the present invention:

[0050] In an embodiment of the present invention, by using a multi-component carbide in the slurry, and the multi-component carbide includes at least two of titanium, zirconium, niobium, tantalum, and hafnium, the above metals have higher hardness and heat resistance compared to alumina. Applying the slurry to the separator can improve the anti-puncture strength of the battery cell, thereby solving the technical problem of excessive short-circuit temperature rise caused by the battery cell being squeezed or punctured by a needle. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are only some embodiments of the present invention. For those skilled in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0052] Figure 1 is a flowchart of a slurry preparation method provided by an embodiment of the present invention;

[0053] Figure 2 is a flowchart of a separator preparation method provided by an embodiment of the present invention;

[0054] Figure 3 is a SEM morphology diagram of a multi-component carbide provided by an embodiment of the present invention;

[0055] Figure 4 is an appearance diagram of a specimen after a needle puncture test provided by an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0056] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative efforts belong to the scope of protection of the present invention. In addition, it should be understood that the specific embodiments described herein are only used to explain and illustrate the present invention, and are not used to limit the present invention. In the present invention, unless otherwise stated, the orientation words such as "upper" and "lower" usually refer to the upper and lower in the actual use or working state of the device, specifically the drawing direction in the drawings; and "inner" and "outer" refer to the outline of the device.

[0057] In the related art, alumina is usually coated on the surface of the separator to ensure the thermal stability of the separator.

[0058] However, during use, the separator may be subjected to mechanical pressure or puncture by a sharp object, resulting in the technical problem of excessive short-circuit temperature rise caused by the battery cell being squeezed or punctured by a needle.

[0059] In view of this, the present application provides a slurry, a preparation method thereof, a separator and an electric core.

[0060] In a first aspect, an embodiment of the present invention provides a slurry. By mass, the slurry may include the following components:

[0061] 20 parts to 35 parts of multi - carbide;

[0062] 2.5 parts to 4.5 parts of binder;

[0063] 65 parts to 75 parts of solvent;

[0064] Wherein, the multi - carbide includes at least two of titanium, zirconium, niobium, tantalum, and hafnium.

[0065] The slurry provided by the embodiment of the present application includes multi - carbide, and the multi - carbide includes at least two of titanium, zirconium, niobium, tantalum, and hafnium. Since titanium, zirconium, niobium, tantalum, and hafnium have good hardness and high - temperature resistance compared with aluminum, for the protective layer made of a combination of two or more of the above - mentioned metal elements, the protective layer can help resist external mechanical pressure or puncture by sharp objects, effectively preventing short - circuit between the positive and negative electrodes of the electric core.

[0066] In one embodiment, based on 100% of the total mass of the slurry, the slurry includes 20% to 35% of multi - carbide, 2.5% to 4.5% of binder, and the balance is solvent.

[0067] It can be understood that the mass percentage content of the multi - carbide accounts for 20% to 35%, ensuring the content of the multi - carbide in the slurry. Moreover, the mass percentage content of the binder accounts for 2.5% to 4.5%, which helps to ensure that after the slurry is coated on the surface of the separator, the separator has high mechanical strength, thereby reducing the influence of external mechanical pressure or sharp objects on the separator, and making the prepared slurry have excellent puncture - resistance ability and temperature - rise resistance performance.

[0068] In one embodiment, the multi - carbide may include any combination of two of titanium, zirconium, niobium, tantalum, and hafnium.

[0069] It can be understood that titanium, zirconium, niobium, tantalum, and hafnium all have excellent high strength and high - temperature resistance, and titanium, zirconium, tantalum, and hafnium also have good corrosion resistance. In addition, titanium and niobium also have the characteristic of maintaining high strength at high temperatures.

[0070] In one embodiment, the multi - carbide may include any one of titanium - zirconium - carbon, titanium - niobium - carbon, and titanium - hafnium - carbon. Further, the multi - carbide may include titanium - zirconium - carbon.

[0071] It can be understood that the multi-component carbide used in this embodiment includes titanium zirconium carbide. Titanium and zirconium have good strength and high temperature resistance, and after the combination of the two, it can be applied to the environment that needs to withstand high mechanical stress; in addition, titanium has better fatigue resistance than aluminum, which helps to be more reliable in applications that bear cyclic loads for a long time.

[0072] In one embodiment, the mass ratio of titanium:zirconium:carbon in the multi-component carbide can be (1 - 1.5):(1 - 1.5):2. Further, the mass ratio of titanium:zirconium:carbon in the multi-component carbide can be 1:(1 - 1.5):2; or the mass ratio of titanium:zirconium:carbon in the multi-component carbide can be (1 - 1.5):1:2. Exemplarily, the mass ratio of titanium:zirconium:carbon in the multi-component carbide can be 1:1:2, 1.2:1:2, 1.5:1:2, 1:1.2:2 or 1:1.5:2.

[0073] In one embodiment, referring to Figure 3 , the average particle size of the multi-component carbide can be 100 nm to 500 nm. Further, the average particle size of the multi-component carbide can be 100 nm to 350 nm. Exemplarily, the average particle size of the multi-component carbide can be 100 nm, 120 nm, 150 nm, 170 nm, 200 nm, 220 nm, 250 nm, 270 nm, 290 nm, 310 nm, 330 nm, 350 nm and any value between the above adjacent two values. The average particle size can be observed by scanning electron microscope (SEM) and transmission electron microscope (TEM) to observe the morphology of the powder in the embodiment and measure the particle size.

[0074] It can be understood that the average particle size of the multi-component carbide is between 100 nm and 350 nm, that is, the particle size of the multi-component carbide is very fine. The fine particle size particles can play a better rigid support role, which helps to improve the puncture resistance of the separator; moreover, the slurry with fine particle size may also reduce the interfacial transfer resistance of the separator, thereby improving the electrochemical performance of the battery.

[0075] In one embodiment, the binder material includes one or a combination of polyvinylidene fluoride, polyvinyl alcohol, and polytetrafluoroethylene.

[0076] It can be understood that polyvinylidene fluoride, polyvinyl alcohol, and polytetrafluoroethylene all have excellent heat resistance and can maintain their performance unchanged in a high temperature environment, making the battery more suitable for use under high temperature conditions.

[0077] In one embodiment, the solvent includes at least one of N-methylpyrrolidone and N,N-dimethylformamide.

[0078] It is understandable that solvents such as N-methylpyrrolidone (NMP) and N,N-dimethylformamide (DMF) exhibit good solubility and stability when dissolving PVDF, and are volatile during the coating of the ceramic slurry, leaving the effective solid substances remaining.

[0079] In one embodiment, the solid content of the slurry can be 25% to 35%. Further, the solid content of the slurry can be 27% to 33%. Exemplarily, the solid content of the slurry can be 27%, 27.5%, 28%, 28.5%, 29%, 29.5%, 30%, 30.5%, 31%, 31.5%, 32%, 32.5%, 33%, and any value between two adjacent above-mentioned values. The solid content can be tested by the drying method, and the solid content (%) = (mass of the sample after drying / mass of the sample before drying) × 100%.

[0080] It is understandable that the greater the solid content of the slurry, the higher the effective components in the slurry, which is more conducive to ensuring the high strength and high temperature resistance of the separator. However, if the solid content of the slurry is too large, the viscosity increases and the fluidity weakens, which is not conducive to the coating of the slurry on the surface of the separator. Therefore, it is appropriate to limit the solid content of the slurry to 25% to 35%.

[0081] In a second aspect, an embodiment of the present invention provides a method for preparing a slurry for preparing the aforementioned slurry. Refer to Figure 1 , and the preparation method may include the following steps:

[0082] S110. Provide a multi-component carbide, a binder, and a solvent;

[0083] S120. Stir and mix the multi-component carbide, the binder, and the solvent to obtain a slurry.

[0084] It is understandable that the method for preparing the slurry in the embodiment of the present application is simple. By stirring and mixing the multi-component carbide, the binder, and the solvent, a slurry with uniform and stable texture can be prepared.

[0085] In one embodiment, in step S120, first dissolve the binder in a part of the solvent to form a glue solution; then dissolve the multi-component carbide and the glue solution in the remaining solvent, and stir and mix to obtain a slurry.

[0086] In one embodiment, the solid content of the glue solution can be 5% to 15%. Further, the solid content of the glue solution can be 8% to 12%. Exemplarily, the solid content of the glue solution can be 8%, 8.5%, 9%, 9.5%, 10%, 10.5%, 11%, 11.5%, 12%, and any value between two adjacent above-mentioned values.

[0087] It is understandable that the higher the solid content of the glue, the higher its strength after curing. At the same time, the solid content of the glue should not be too high, otherwise it will not be easy to apply the glue. Therefore, the solid content of the glue in this application is limited to 5% to 15%.

[0088] In one embodiment, the multi-component carbide can be prepared by the following steps:

[0089] S111, placing multiple metal elements and carbon powder in a reaction container, heating them under an inert atmosphere to react, and obtaining a multiphase solid solution;

[0090] S112, cooling the multiphase solid solution and grinding it to obtain multi-component carbide;

[0091] The plurality of metal elements include at least two of metal element titanium, metal element zirconium, metal element niobium, metal element tantalum, and metal element hafnium.

[0092] It can be understood that the synthesis method is simple and convenient, and the obtained multi-component carbide material has uniform texture and stable properties, by first heating a plurality of metal elements and carbon powder to obtain a multi-phase solid solution, and then cooling the multi-phase solid solution and grinding it.

[0093] In one embodiment, in step S111, the plurality of metal elements may include any two of metal element titanium, metal element zirconium, metal element niobium, metal element tantalum, and metal element hafnium. Further, the plurality of metal elements include one of a combination of metal element titanium and metal element zirconium, a combination of metal element titanium and metal element niobium, and a combination of metal element titanium and metal element hafnium.

[0094] In one embodiment, in step S111 , the inert atmosphere includes any one of a nitrogen atmosphere, an argon atmosphere, a neon atmosphere, a helium atmosphere, a xenon atmosphere, or a krypton atmosphere, or a combination of at least two of them.

[0095] In one embodiment, in step S111, the temperature range of the heating is 1500° C. to 2000° C. Further, the temperature range of the heating may be 1500° C. to 1900° C. Exemplarily, the temperature range of the heating may be 1500° C., 1550° C., 1600° C., 1650° C., 1700° C., 1750° C., 1800° C., 1850° C., 1900° C., and any value between two adjacent values ​​thereof.

[0096] In one embodiment, in step S111, after the temperature is raised to 1500° C. to 2000° C., the temperature may be kept warm for 4 to 10 minutes. Further, the temperature may be kept warm for 5 to 8 minutes. Exemplarily, the temperature may be kept warm for 5 minutes, 6 minutes, 7 minutes, 8 minutes, and any value between the adjacent values.

[0097] In one embodiment, in step S112, the temperature reduction includes reducing the temperature to room temperature in a natural cooling manner.

[0098] In one embodiment, in step S112, the temperature reduction includes reducing the temperature to room temperature at a temperature reduction rate of 4°C to 20°C / h. Further, the temperature reduction includes reducing the temperature to room temperature at a temperature reduction rate of 8°C to 15°C / h. Exemplarily, the temperature reduction rate can be 8°C / h, 9°C / h, 10°C / h, 11°C / h, 12°C / h, 13°C / h, 14°C / h, 15°C / h, and any value between any two adjacent of the above values to reduce the temperature to room temperature.

[0099] In one embodiment, in step S112, the grinding includes ball-milling the temperature-reduced multiphase solid solution for 9 h to 12 h, and the diameter of the ball-milling medium is 0.5 cm to 1 cm. Exemplarily, the ball-milling time can be 9 h, 10 h, 11 h, 12 h, and any value between any two adjacent of the above values; the diameter of the ball-milling medium can be 0.5 cm, 0.6 cm, 0.7 cm, 0.8 cm, 0.9 cm, 1.0 cm, and any value between any two adjacent of the above values.

[0100] In a third aspect, an embodiment of the present invention provides a separator, which may include:

[0101] A base film;

[0102] A protective layer provided on one or both sides of the base film;

[0103] wherein the protective layer includes a multi-component carbide;

[0104] The multi-component carbide includes at least two of titanium element, zirconium element, niobium element, tantalum element, and hafnium element.

[0105] The separator provided by the embodiment of the present application includes a base film and a protective layer, and the protective layer includes a multi-component carbide. Among them, the multi-component carbide includes at least two metal elements of titanium element, zirconium element, niobium element, tantalum element, and hafnium element. Since the multi-component carbide has excellent strength and high temperature resistance, the protective layer has excellent strength and high temperature resistance, which helps to resist external mechanical pressure or puncture by sharp objects, and effectively prevents short circuit between the positive and negative electrodes of the battery cell.

[0106] In one embodiment, the thickness of the protective layer ranges from 1 μm to 5 μm. Further, the thickness of the protective layer can range from 1.5 μm to 4.5 μm. Exemplarily, the thickness of the protective layer can be 1.5 μm, 1.6 μm, 1.7 μm, 1.8 μm, 1.9 μm, 2 μm, 2.1 μm, 2.2 μm, 2.3 μm, 2.4 μm, 2.5 μm, 2.6 μm, 2.7 μm, 2.8 μm, 2.9 μm, 3.0 μm, 3.1 μm, 3.2 μm, 3.3 μm, 3.4 μm, 3.5 μm, 3.6 μm, 3.7 μm, 3.8 μm, 3.9 μm, 4.0 μm, 4.1 μm, 4.2 μm, 4.3 μm, 4.4 μm, 4.5 μm, and any value between any two adjacent values above.

[0107] Fourthly, an embodiment of the present invention provides a method for preparing a separator for preparing the aforementioned separator. Refer to Figure 2 , the preparation method includes the following steps:

[0108] S100. Provide a base film;

[0109] S200. Prepare a slurry by using a multi-component carbide, a binder, and a solvent;

[0110] S300. Coat the slurry on the base film to form a protective layer, and obtain the separator.

[0111] An embodiment of the present application provides a method for preparing a separator. By stirring and mixing a multi-component carbide, a binder, and a solvent to form a slurry, and then coating the slurry on a base film to form a protective layer, it helps to improve the puncture resistance of the separator and effectively prevent the positive and negative electrodes of the battery cell from short-circuiting.

[0112] Fifthly, an embodiment of the present invention provides a battery cell including the aforementioned separator or a separator prepared by the method for preparing the aforementioned separator.

[0113] An embodiment of the present application provides a battery cell. Since the aforementioned separator has excellent strength and high temperature resistance, the battery cell including the aforementioned separator also has excellent strength and high temperature resistance, which helps to improve the puncture resistance of the battery cell, thereby preventing the positive and negative electrodes of the battery cell from short-circuiting.

[0114] The following specifically describes the present application through specific embodiments. The following embodiments are only partial embodiments of the present application and do not limit the present application. The raw materials used in the following embodiments are all commercially available products unless otherwise specified.

[0115] Example 1

[0116] A battery cell, the battery cell includes a negative electrode tab, a separator, a positive electrode tab, a separator and a negative electrode tab which are stacked in sequence, wherein the separator is prepared by the following method:

[0117] Provide a PE-based film with a thickness of 10 μm;

[0118] Prepare a multi-component carbide:

[0119] Place elemental titanium, elemental zirconium and carbon powder in a sintering furnace, and under N 2 atmosphere, heat up to 1700 °C, keep warm for 5 min to obtain a multi-phase solid solution; wherein, elemental titanium, elemental zirconium and carbon powder are weighed according to a mass ratio of 1:1:2; cool the multi-phase solid solution to room temperature, and grind to obtain a multi-component carbide with an average particle size of 350 nm; wherein, the grinding medium uses balls with a diameter of 0.5 cm to 1 cm;

[0120] Prepare a slurry:

[0121] The binder is PVDF and the solvent is NMP;

[0122] Dissolve 3.5 kg of PVDF in 31.5 kg of NMP to prepare a PVDF glue solution with a solid content of 10%;

[0123] Stir and mix 27 kg of the multi-component carbide with 35 kg of the PVDF glue solution with a solid content of 10% to obtain an intermediate solution;

[0124] Add 38 kg of NMP to the intermediate solution and stir evenly to prepare a slurry with a solid content of about 30%;

[0125] Use a coater to coat the slurry on the PE-based film, and the coating thickness of the slurry is 4 μm. After drying, a separator is obtained.

[0126] Prepare a negative electrode tab:

[0127] Stir graphite, conductive carbon black SP, sodium carboxymethyl cellulose CMC, and binder SBR according to a mass ratio of 96.9:0.4:1.4:1.3 to prepare a slurry, evenly coat the slurry on a copper foil current collector, dry and cold press, and cut the negative electrode tab with a thickness of 150 μm.

[0128] Prepare a positive electrode tab:

[0129] Stir a NMP solution of lithium iron manganese phosphate with a solid content of 25% with carbon nanotubes CNT, polyvinylidene fluoride PVDF and polyvinylpyrrolidone PVP according to a mass ratio of 97.9:0.4:1.5:0.2 to prepare a slurry. After stirring, evenly coat it in an aluminum foil current collector, dry and cold press and cut it into a positive electrode tab with a thickness of 200 μm.

[0130] Example 2:

[0131] A battery cell, which is different from that of Example 1 in that the composition of the multi-component carbide is different. The multi-component carbide in this example is prepared by the following steps:

[0132] Put elemental titanium, elemental niobium and carbon powder into a sintering furnace, and under N 2 atmosphere, heat up to 1800 °C and keep the temperature for 5 minutes to obtain a multi-phase solid solution; among them, elemental titanium, elemental niobium and carbon powder are weighed according to a mass ratio of 1:1:2; cool the multi-phase solid solution to room temperature and grind it to obtain a multi-component carbide; among them, the grinding medium is small balls with a diameter of 0.5 cm to 1 cm; the remaining steps and process parameters are the same as those in Example 1.

[0133] Example 3:

[0134] A battery cell, which is different from that of Example 1 in that the composition of the multi-component carbide is different. The multi-component carbide in this example is prepared by the following steps:

[0135] Put elemental titanium, elemental hafnium and carbon powder into a sintering furnace, and under N 2 atmosphere, heat up to 1900 °C and keep the temperature for 5 minutes to obtain a multi-phase solid solution; among them, elemental titanium, elemental hafnium and carbon powder are weighed according to a mass ratio of 1:1:2; cool the multi-phase solid solution to room temperature and grind it to obtain a multi-component carbide; among them, the grinding medium is small balls with a diameter of 0.5 cm to 1 cm; the remaining steps and process parameters are the same as those in Example 1.

[0136] Example 4:

[0137] A battery cell, which is different from that of Example 1 in that the solid content of the slurry is different. The solid content of the slurry in this example is 25%.

[0138] Example 5:

[0139] A battery cell, which is different from that of Example 1 in that the solid content of the slurry is different. The solid content of the slurry in this example is 35%.

[0140] Example 6:

[0141] A battery cell, which is different from that of Example 1 in that the average particle size of the multi-component carbide is different. The average particle size of the multi-component carbide in this example is 100 nm.

[0142] Example 7:

[0143] A battery cell, which is different from that of Example 1 in that the average particle size of the multi-component carbide is different. The average particle size of the multi-component carbide in this example is 500 nm.

[0144] Example 8:

[0145] A battery cell, which is different from that in Example 1 in that the average particle size of the multi-component carbide is different. In this example, the average particle size of the multi-component carbide is 200 nm.

[0146] Example 9:

[0147] A battery cell, which is different from that in Example 1 in that the mass ratio of Ti, Zr and C in the multi-component carbide is different. In this example, the mass ratio of Ti, Zr and C in the multi-component carbide is 1.5:1:2, and the remaining steps are the same as those in Example 1.

[0148] Example 10:

[0149] A battery cell, which is different from that in Example 1 in that the mass ratio of Ti, Zr and C in the multi-component carbide is different. In this example, the mass ratio of Ti, Zr and C in the multi-component carbide is 1:1.5:2, and the remaining steps are the same as those in Example 1.

[0150] Comparative Example 1:

[0151] A battery cell, which is different from that in Example 1 in the selection of the multi-component carbide. In this comparative example, the multi-component carbide is a binary carbide TiC and ZrC mixed in a mass ratio of 1:1, and then the multi-component carbide and a PVDF adhesive solution with a solid content of 10% are stirred and mixed in a volume ratio of 9:1 to obtain an intermediate solution; NMP is added to the intermediate solution and stirred and mixed to obtain a slurry with a solid content of 30%; the slurry is coated on a PE base film by a coater, and the coating thickness is 4 μm to obtain a separator.

[0152] Comparative Example 2:

[0153] A battery cell, which is different from that in Example 1 in the preparation method of the separator. The separator in this comparative example includes a PE base film and an alumina coating coated on the surface of the PE base film. The preparation method of the alumina coating includes the following steps:

[0154] Alumina, polymethyl methacrylate, polyethylene glycol 200, carboxymethyl cellulose sodium thickener and deionized water are ground and stirred, wherein the grinding speed is 1000 rpm and the stirring time is 10 h to obtain an alumina slurry;

[0155] The alumina slurry is coated on one side of the PE base film, and the coating thickness is 4 μm, and dried to obtain a separator.

[0156] Detection method:

[0157] 1. Puncture strength test:

[0158] The diaphragms of the embodiment and the comparative example were flattened and clamped in a fixture, and punctured at a rate of 100 mm / min. After completion, the samples were taken out, and the thickness was tested at 4 points around the pinhole according to the provisions of GB / T6672-2001, and the average value was taken, and the puncture strength was calculated according to the formula;

[0159] 2. Overcharge test:

[0160] Charge the battery cell at a charge rate of 1C until the battery cell reaches 120% of the rated capacity, and monitor the maximum temperature of overcharge 120% SOC;

[0161] 3. Acupuncture test:

[0162] According to GB / T 31485 standard, after fully charging the battery cell, use a 5mm steel needle to pierce the battery cell at a speed of 25mm / s. The steel needle stays in the battery cell and observes the maximum temperature rise within 1 hour to determine the temperature that triggers thermal runaway.

[0163] 4. Average particle size: The morphology of the powders in the examples was observed and the particle size was measured using a scanning electron microscope (SEM) and a transmission electron microscope (TEM);

[0164] 5. Solid content (%) = (mass of sample after drying / mass of sample before drying) × 100%.

[0165] The test results of the embodiment and the comparative example are shown in Table 1

[0166]

[0167]

[0168] Compared with comparative example 1, embodiment 1 uses titanium zirconium carbon, which plays a role of solid solution strengthening and dispersion strengthening, and improves the strength and high temperature resistance of the diaphragm. Comparative example 1 uses a mixture of titanium carbide and zirconium carbide. Titanium carbide and zirconium carbide still exist in independent forms and do not form a multiphase solid solution. The strengthening effect of comparative example 1 is not as good as that of embodiment 1. Therefore, the puncture strength of the sample of embodiment 1 is much greater than that of comparative example 1, and the maximum puncture strength of 120% SOC overcharge can reach about 50°C, which is much lower than 60°C of comparative example 1. The maximum temperature rise of the needle puncture test is about 45°C, which is lower than 52°C of comparative example 1. The triggering thermal runaway temperature of the sample of embodiment 1 is also greatly reduced compared with comparative example 1. Figure 4 It can be seen that after the needle puncture test, the surface condition of the sample in Example 1 is good, and no heat spread and explosion occurs.

[0169] Compared with Example 1 and Comparative Example 2, Example 2 uses alumina slurry to coat the PE base film to prepare the diaphragm. Compared with alumina, titanium zirconium carbon has higher strength and high temperature resistance, which helps to improve the puncture resistance of the battery cell and the temperature rise resistance during extrusion and acupuncture, thereby improving the technical problem of short circuit of the positive and negative electrodes caused by puncture due to the external environment.

[0170] Compared with Example 1, Example 2 uses titanium niobium carbon, and Example 3 uses titanium hafnium carbon. Compared with Example 1, the samples of Example 2-3 have better strength and high temperature resistance. Therefore, the puncture strength of the samples of Example 2-3 is greater than that of the sample of Example 1, and the temperature resistance is also better than that of the sample of Example 1.

[0171] Compared with Example 1, Example 4-5 changes the solid content of the slurry to 25%. Compared with Example 1, Example 4 reduces the solid content of the slurry, and the content of multi-carbide in the slurry is less, which will reduce the strength and high temperature resistance of the diaphragm; Example 5 changes the solid content of the slurry to 35%. Compared with Example 1, Example 5 increases the solid content of the slurry, and the content of multi-carbide in the slurry increases, but excessive multi-carbide may be unevenly dispersed with the bonding material and the solvent, resulting in a decrease in the puncture strength of the sample in Example 5 and a decrease in the temperature rise resistance.

[0172] Compared with Example 1, Examples 6-8 change the average particle size of the multi-carbide in the slurry after grinding. The average particle size of the multi-carbide in Example 6 is 100nm, the average particle size of the multi-carbide in Example 7 is 500nm, and the average particle size of the multi-carbide in Example 8 is 200nm. Combined with the test results in Table 1, it can be seen that the smaller the average particle size of the multi-carbide, the more conducive it is to improve the strength and temperature resistance of the diaphragm, thereby improving the puncture resistance of the diaphragm. This is because the smaller the average particle size of the multi-carbide, the faster the smaller particle size can be dissolved, so that the hardness obtained after calcination is higher and the temperature resistance is also higher; however, the average particle size should not be too large, and the slurry prepared with multi-carbide of larger particle size has a slightly reduced temperature resistance.

[0173] Compared with Example 1, Example 9 changes the ratio of Ti, Zr and C in the multi-carbide. Compared with Example 1, the content of Ti is increased, which will lead to excess Ti. The excess Ti reacts slowly with air to form TiO 2 , TiO 2 The Mohs hardness of the alloy is lower than that of TiC, and its structural stability is weaker in a high temperature environment. Example 10 changes the ratio of Ti, Zr and C in the multi-component carbide. Compared with Example 1, the content of Zr is increased, which will lead to excess Zr. The excess Zr reacts slowly with air to form ZrO 2, ZrO 2 The Mohs hardness of 2 is lower than that of ZrC, and its structural stability in high-temperature environments is also weaker. Therefore, the mass ratio of Ti, Zr, and C is preferably (1 - 1.5):(1 - 1.5):2.

[0174] The embodiments of the present invention have been introduced in detail above. Specific examples are used in this article to elaborate on the principle and implementation manner of the present invention. The description of the above embodiments is only used to help understand the method and its core idea of the present invention; at the same time, for those skilled in the art, based on the idea of the present invention, there will be changes in the specific implementation manner and application scope. In summary, the content of this specification should not be construed as a limitation to the present invention.

Claims

1. A slurry, characterized in that: In parts by mass, the slurry comprises: 20 to 35 parts of multi-component carbide; 2.5 to 4.5 parts of bonding material; 65 to 75 parts of solvent; The multi-component carbide includes at least two of the following elements: titanium, zirconium, niobium, tantalum and hafnium.

2. The slurry according to claim 1, characterized in that Based on 100% of the total mass of the slurry, the slurry includes 20% to 35% of multi-carbide, 2.5% to 4.5% of bonding material, and the balance is solvent.

3. The slurry according to claim 1, characterized in that The multi-component carbide comprises a combination of any two of the elements titanium, zirconium, niobium, tantalum and hafnium; and / or The multi-component carbide includes any one of titanium zirconium carbon, titanium niobium carbon, and titanium hafnium carbon; Preferably, the mass ratio of titanium:zirconium:carbon in the multi-component carbide is (1-1.5):(1-1.5):

2.

4. The slurry according to claim 1, characterized in that The average particle size of the multi-component carbide is 100nm to 500nm; Preferably, the average particle size of the multi-component carbide is 100 nm to 350 nm.

5. The slurry according to claim 1, characterized in that The bonding material includes one or more combinations of polyvinylidene fluoride, polyvinyl alcohol, and polytetrafluoroethylene; and / or The solvent includes at least one of N-methylpyrrolidone and N,N-dimethylformamide.

6. The slurry according to claim 1, characterized in that The solid content of the slurry is 25% to 35%.

7. A method for preparing a slurry, characterized in that: For preparing the slurry according to any one of claims 1 to 6, the preparation method comprises the following steps: Provide multicomponent carbides, bonding materials and solvents; The multi-component carbide, the bonding material and the solvent are stirred and mixed to prepare a slurry.

8. The method for preparing the slurry according to claim 7, characterized in that: The multi-component carbide is prepared by the following steps: Placing multiple metal elements and carbon powder in a reaction container, heating them under an inert atmosphere to react, and obtaining a multiphase solid solution; The multiphase solid solution is cooled and ground to obtain multi-component carbides; The plurality of metal elements include at least two of metal element titanium, metal element zirconium, metal element niobium, metal element tantalum, and metal element hafnium; Preferably, the plurality of metal elements include any two of metal element titanium, metal element zirconium, metal element niobium, metal element tantalum, and metal element hafnium; Preferably, the plurality of metal elements include metal element titanium and metal element zirconium.

9. The method for preparing the slurry according to claim 8, characterized in that: The inert atmosphere includes any one of nitrogen atmosphere, argon atmosphere, neon atmosphere, helium atmosphere, xenon atmosphere or krypton atmosphere, or a combination of at least two thereof; and / or The temperature range of the heating is 1500° C. to 2000° C.; and / or The cooling includes cooling to room temperature by natural cooling; and / or The cooling comprises cooling to room temperature at a cooling rate of 4°C to 20°C / h; and / or The grinding comprises ball milling the cooled multi-phase solid solution for 9 to 12 hours, with the diameter of the ball milling medium being 0.5 to 1 cm.

10. The method for preparing the slurry according to claim 7, characterized in that: The stirring and mixing of the multi-component carbide, the bonding material and the solvent includes: Firstly, the bonding material is dissolved in part of the solvent to obtain a glue solution with a solid content of 5% to 15%; The multi-component carbide and the glue solution are dissolved in the remaining solvent, and the mixture is stirred and mixed to obtain a slurry.

11. A diaphragm, characterized in that: The diaphragm comprises: Basement membrane; A protective layer, disposed on one side or both sides of the base film; Wherein, the protective layer comprises multi-component carbide; The multi-component carbide includes at least two metal elements selected from the group consisting of titanium, zirconium, niobium, tantalum and hafnium.

12. The diaphragm according to claim 11, characterized in that The thickness of the protective layer ranges from 1 μm to 5 μm.

13. A method for preparing a diaphragm, characterized in that: For preparing the diaphragm according to claim 11 or 12, the preparation method comprises the following steps: providing a basement membrane; The slurry is prepared by using multi-component carbides, bonding materials and solvents; The slurry is applied onto a base film to form a protective layer, thereby obtaining the separator.

14. A battery cell, characterized in that: The invention comprises a diaphragm as claimed in claim 11 or 12 or a diaphragm prepared by the method for preparing the diaphragm as claimed in claim 13.

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