A method for manufacturing a composite ceramic separator, a composite ceramic separator, and a battery

Abstract

The application discloses a preparation method of a composite ceramic diaphragm, the composite ceramic diaphragm and a battery. The preparation method comprises the following steps: providing a suspension containing ceramic; applying the suspension to the surface of a porous base film, applying negative pressure, and allowing the suspension to penetrate into the pores of the porous base film to obtain the composite ceramic diaphragm after drying; wherein the particle size of the ceramic is smaller than the pore size of the pores. The composite ceramic diaphragm comprises a porous base film and ceramic, the ceramic is formed in at least the pores of the porous base film, the particle size of the ceramic is smaller than the pore size of the pores, and the ceramic comprises first inorganic ceramic, which is nitride inorganic ceramic. The composite ceramic diaphragm has excellent high-temperature resistance and good interface performance, and can effectively improve the safety performance of the battery. The preparation method can uniformly disperse the ceramic particles in the pores of the base film, and effectively improves the performance of the diaphragm.

Description

Technical Field

[0001] This invention belongs to the field of battery technology and relates to a method for preparing a composite ceramic separator, the composite ceramic separator, and a battery. Background Technology

[0002] With the widespread application of new energy vehicles and portable electronic devices, people have placed higher demands on battery performance, such as high safety performance, high energy density, and long service life. Among these, battery safety performance is particularly important. Battery explosions, spontaneous combustion, and other safety issues not only endanger personal safety but can also cause property damage. One of the core reasons for this is the use of liquid electrolytes. Liquid electrolytes contain a large number of flammable components, making them highly susceptible to explosion and combustion when the battery encounters impacts or other adverse conditions.

[0003] Quasi-solid-state or semi-solid-state batteries significantly improve battery safety by reducing or eliminating the use of liquid electrolytes. A key component in solid-state batteries is the solid electrolyte layer, which should generally possess the following characteristics: 1. Effectively isolate the positive and negative electrodes to prevent short circuits; 2. Highly efficient conduction of lithium ions; 3. Certain heat resistance to prevent contact between the positive and negative electrodes due to separator shrinkage at high temperatures, thus avoiding safety issues.

[0004] Existing membrane technologies typically employ a process of coating both sides of a base membrane with a slurry containing electrolytes and ceramics to form a ceramic layer. Because ceramics possess heat resistance and electrolytes have ion-conducting properties, the resulting membrane exhibits heat resistance. However, the high-temperature resistance of the membrane still needs further improvement to meet the demands of practical applications. Furthermore, existing membrane preparation methods generally involve coating followed by drying, which can lead to poor adhesion between the electrolyte and ceramics on the base membrane, hindering the improvement of membrane performance.

[0005] Therefore, it is necessary to provide a diaphragm and its preparation method to improve the binding of the components in the diaphragm and effectively improve its high-temperature resistance. Summary of the Invention

[0006] In view of the above-mentioned problems existing in the prior art, the purpose of the present invention is to provide a method for preparing a composite ceramic separator, a composite ceramic separator, and a battery.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] In a first aspect, the present invention provides a method for preparing a composite ceramic diaphragm, characterized in that the preparation method includes the following steps:

[0009] Provides suspensions containing ceramics;

[0010] The suspension is applied to the surface of the porous base membrane, and a negative pressure is applied to allow the suspension to penetrate into the pores of the porous base membrane. After drying, a composite ceramic membrane is obtained.

[0011] Wherein, the particle size of the ceramic is smaller than the pore size of the pores.

[0012] The method of this invention involves applying a suspension to the surface of a porous base membrane and applying negative pressure, which allows the suspension to penetrate into the pores of the porous base membrane. This allows the ceramic particles to enter the pores, resulting in a uniform distribution of ceramic particles within the pores of the porous base membrane. The ceramic particles in the pores can still provide stable support at high temperatures. When this composite ceramic separator is applied to a battery, it can directly contact the positive and negative electrodes, respectively, thereby improving the battery's safety performance.

[0013] Compared to directly immersing a porous membrane in a suspension containing ceramic particles, allowing the particles to enter the pores, the method of this invention ensures the uniform distribution of ceramic particles within the pores. Direct immersion, lacking external force, is difficult and may result in an uneven distribution of ceramic particles, with more particles near the membrane surface and fewer inside, leading to poor membrane performance. Furthermore, the method of this invention minimizes the amount of ceramic on the membrane surface, thus avoiding interfacial defects caused by direct contact between ceramic particles and the positive and negative electrodes.

[0014] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. The technical objectives and beneficial effects of the present invention can be better achieved and realized through the following preferred technical solutions.

[0015] In a preferred embodiment of the method for preparing the composite ceramic diaphragm according to the present invention, the solid content of the suspension is 5%-20%, such as 5%, 7%, 8%, 10%, 12.5%, 15%, 18%, or 20%. If the solid content of the suspension is too low, the suspension is too dilute, which will prevent the ceramic particles from fully entering the ceramic of the porous base membrane under negative pressure, resulting in a low internal ceramic content in the prepared composite ceramic diaphragm. If the solid content of the suspension is too high, the suspension is too concentrated, which will cause the ceramic particles to easily agglomerate and be difficult to disperse evenly in the suspension. Consequently, after the suspension is applied to the surface of the porous base membrane, the ceramic particles on the surface are unevenly distributed, and after subsequent negative pressure treatment, the ceramic distribution inside the porous base membrane is uneven.

[0016] Preferably, the particle size of the ceramics in the suspension is 0.01μm-3μm, such as 0.01μm, 0.05μm, 0.1μm, 0.2μm, 0.3μm, 0.4μm, 0.5μm, 0.6μm, 0.7μm, 0.8μm, 0.9μm, 1μm, 1.5μm, 2μm, 2.5μm or 3μm.

[0017] Preferably, based on the dry weight of the suspension, the mass content of the ceramic is 5%-100%, for example 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 97%, or 100%, etc., preferably 5%-95%, more preferably 50%-95%.

[0018] Preferably, the ceramic includes a first inorganic ceramic, which is a nitride inorganic ceramic.

[0019] Nitride inorganic ceramics possess excellent insulation properties, along with superior high-temperature resistance and thermal conductivity. When applied to separators, they effectively improve the separator's resistance to high-temperature shrinkage, thereby enhancing battery safety. Taking cubic boron nitride as an example, it has an extremely high melting point, excellent thermal shock resistance and thermal stress resistance, and good shrinkage resistance at high temperatures. It also exhibits good thermal conductivity, quickly transferring heat to other parts. Therefore, at high temperatures, it provides excellent support within the separator, preventing short circuits caused by separator deformation, thus improving the separator's high-temperature shrinkage resistance and ensuring battery safety at high temperatures. Furthermore, nitride inorganic ceramics have a lower density, allowing for maximum control over the overall battery weight.

[0020] Preferably, the nitride inorganic ceramic includes at least one of boron nitride, aluminum nitride, silicon nitride, titanium nitride, and magnesium nitride. These substances may exist in the form of a mixture or a composite.

[0021] Preferably, the boron nitride comprises hexagonal boron nitride and / or N-type cubic boron nitride.

[0022] Preferably, the ceramic further includes a second inorganic ceramic, which includes at least one of aluminum oxide, titanium dioxide, silicon dioxide, zirconium dioxide, molybdenum-doped silicon dioxide, zirconium boride, zirconium nitride ceramics, silicon boride, vanadium boride, titanium boride, magnesium boride, and inorganic ceramic solid electrolyte.

[0023] Preferably, the zirconium nitride compound includes at least one of ZrN, o-Zr3N4, and c-Zr3N4.

[0024] Preferably, the inorganic ceramic solid electrolyte comprises at least one of lithium lanthanum zirconium oxide (LLZO), lithium lanthanum titanate oxide (LLTO), tantalum-doped lithium lanthanum zirconium oxide (LLZTO), aluminum-doped lithium lanthanum zirconium oxide (LLZAO), lithium germanium phosphorus sulfide (LGPS), lithium phosphorus sulfur chloride (LPSCl), and lithium aluminum germanium phosphate (LAGP).

[0025] Preferably, the mass of the second inorganic ceramic accounts for 0-95% of the mass of the first inorganic ceramic, for example, 0.05%, 0.1%, 0.3%, 0.5%, 0.8%, 1%, 1.5%, 2%, 2.5%, 3%, 4%, 4.5%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, or 95%.

[0026] As a preferred embodiment of the preparation method of the composite ceramic diaphragm of the present invention, the suspension further includes a polymer binder and an organic solvent.

[0027] Preferably, the polymer binder includes at least one selected from polyethylene oxide (PEO), polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP), polyvinylidene fluoride-trifluorochloroethylene copolymer (PVDF-CTFE), polymethyl methacrylate (PMMA), polyacrylic acid (PAA), polyacrylonitrile (PAN), perfluorosulfonic acid resin (Nafion-H), lithium perfluorosulfonic acid resin (Nafion-Li), thermoplastic polyurethane (TPU), polyphenylene sulfide (PPS), polyethyleneimine, ethyl cyanoacrylate (PCA), polyvinyl carbonate (PEC), polypropylene carbonate (PPC), polyvinyl carbonate (PVC), polymalonate, polysuccinate, polyimide (PI), polyetherimide, and polyethersulfone (PESU).

[0028] Preferably, the polymalonate material includes at least one of polypentyl malonate (PPM), polyethylene malonate (PEM), polypropylene glycol malonate (PTM), and polyhexyl malonate (PHM).

[0029] Preferably, the polysuccinate includes at least one of polyethylene succinate (PES) and propylene glycol succinate.

[0030] Preferably, based on the dry basis mass of the suspension, the mass content of the polymer binder is 0%-95% and does not include endpoint values, such as 0.5%, 1%, 2%, 3%, 4%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, or 94%, etc., preferably 3%-95%, more preferably 3%-50%.

[0031] The polymer binder in the suspension has a mass content of 3%-50%, for example, 3%, 4%, 4.5%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, or 50%. If the mass content of the polymer binder is too low, the stability of the suspension will be reduced; if the mass content is too high, the viscosity of the suspension will be too high, making it difficult for ceramic particles to penetrate into the pores of the porous membrane. Using an appropriate amount of binder is beneficial for the formation of a uniform and stable suspension system for the ceramic particles.

[0032] Preferably, the organic solvent includes at least one of N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAC), N-methylpyrrolidone (NMP), and acetonitrile (ACN).

[0033] As a preferred embodiment of the method for preparing the composite ceramic diaphragm according to the present invention, the suspension further includes a dispersant, which includes at least one of nonionic surfactants, anionic surfactants and cationic surfactants.

[0034] In one embodiment, the anionic surfactant is polyvinylpyrrolidone (PVP).

[0035] In one embodiment, the nonionic surfactant is a fluorocarbon surfactant FSO.

[0036] Preferably, based on the dry basis mass of the suspension, the mass content of the dispersant is 0%-2% and does not exceed 0%, for example, 0.05%, 0.1%, 0.3%, 0.5%, 1%, 1.2%, 1.5%, 1.8%, or 2%. Here, the dry basis substances in the suspension refer to the total amount of substances other than the solvent, such as ceramics, polymer binders, and dispersants. Adding a dispersant can improve the dispersibility of ceramic particles in the suspension; however, the content of the dispersant should not be excessive, as too much dispersant will cause instability in the suspension, thereby affecting the dropping effect and the uniformity of ceramic particle dispersion in the final composite ceramic diaphragm, thus affecting the performance of the composite ceramic diaphragm.

[0037] Preferably, the suspension is applied to the surface of the porous base membrane by dropwise addition.

[0038] Preferably, the amount of suspension applied to the surface of the porous base membrane per unit area is 0.08 mL / cm². 2 -0.35mL / cm 2 For example, 0.08 mL / cm 2 0.10 mL / cm 2 0.12 mL / cm 2 0.15 mL / cm 2 0.17 mL / cm 2 0.18 mL / cm 2 0.20 mL / cm 2 0.22 mL / cm 2 0.23 mL / cm 2 0.25mL / cm 2 0.27 mL / cm 2 0.28 mL / cm 2 0.30 mL / cm 2 0.33 mL / cm 2 Or 0.35 mL / cm 2 The amount of material added mainly determines the ceramic content in the composite ceramic membrane. If the amount added is too small, there will be too few ceramic particles in the composite ceramic membrane, making it difficult to improve the membrane's strength and high-temperature resistance. If the amount added is too large, there will be too many ceramic particles in the composite ceramic membrane, which can easily lead to the blockage of the pores in the porous base membrane.

[0039] Preferably, the negative pressure is between 100mbar and 500mbar, such as 100mbar, 150mbar, 200mbar, 220mbar, 240mbar, 260mbar, 280mbar, 300mbar, 350mbar, 400mbar, 450mbar, or 500mbar.

[0040] Preferably, the duration of the negative pressure is 30s-5min, such as 30s, 40s, 50s, 1min, 1.5min, 2min, 2.5min, 3min, 3.5min, 4min, 4.5min or 5min.

[0041] In this invention, the main function of applying negative pressure is to allow the ceramic particles in the suspension to enter and remain in the pores of the porous membrane. If the negative pressure value is too small or the duration of the negative pressure is too short, the ceramic particles will not be able to fully enter the pores of the porous membrane; if the negative pressure value is too large or the duration of the negative pressure is too long, the ceramic particles may pass through the pores of the porous membrane and fail to remain in the pores.

[0042] The method of the present invention can achieve uniform distribution of ceramic particles under relatively low pressure. The preparation method is simple and energy-efficient, making it suitable for large-scale production.

[0043] Preferably, the negative pressure is applied by using a vacuum filtration device to perform vacuum filtration on the porous base membrane to which the suspension has been applied.

[0044] Preferably, the porous base membrane includes any one of porous polyethylene membrane, porous polypropylene membrane, porous polyethylene / polypropylene composite membrane, porous cellulose membrane, porous polyethylene terephthalate membrane, porous polyimide membrane, porous polyvinylidene fluoride membrane, porous polyvinylidene fluoride-hexafluoropropylene copolymer membrane, or porous polytetrafluoroethylene membrane.

[0045] This invention does not specifically limit the source of the porous base membrane; it can be a commercially available base membrane or one prepared using existing methods, such as dry or wet processes. The pore size of the porous base membrane prepared by different methods will vary.

[0046] In one embodiment, a porous base membrane is prepared by electrospinning or meltblowing.

[0047] Preferably, the porosity of the porous base membrane is 40%-80%, such as 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, or 80%.

[0048] Preferably, in the porous base film, the pore size is 0.01μm-10μm, for example, 0.01μm, 0.05μm, 0.1μm, 0.2μm, 0.3μm, 0.4μm, 0.5μm, 0.6μm, 0.7μm, 0.8μm, 0.9μm, 1μm, 1.5μm, 2μm, 2.5μm, 3μm, 3.5μm, 4μm, 4.5μm, 5μm, 5.5μm, 6μm, 6.5μm, 7μm, 7.5μm, 8μm, 8.5μm, 9μm, 9.5μm or 10μm, preferably 0.01μm-1μm, and more preferably 0.03μm-5μm.

[0049] In a second aspect, the present invention provides a composite ceramic membrane, the composite ceramic membrane comprising a porous base membrane and a composite ceramic material, the composite ceramic material comprising ceramic, the ceramic being formed at least in the pores of the porous base membrane, the particle size of the ceramic being smaller than the pore size of the pores; the ceramic comprising a first inorganic ceramic, the first inorganic ceramic being a nitride inorganic ceramic.

[0050] In the composite ceramic separator of this invention, since the ceramic is located at least within the pores of the porous base membrane, it provides better stability and support compared to placing the ceramic on the surface of the base membrane. This results in better high-temperature mechanical properties and improved high-temperature shrinkage resistance of the separator. Furthermore, the presence of the ceramic within the pores avoids the interfacial problems caused by direct contact between ceramic particles and the positive and negative electrodes.

[0051] Furthermore, since the composite ceramic separator of the present invention contains at least nitride inorganic ceramics, its overall performance is further improved. Specifically: 1. Compared with other inorganic ceramics (such as alumina, silicon dioxide, etc.), nitride inorganic ceramics have a lower density, thus maximizing the control of the overall battery weight; 2. Nitride inorganic ceramics have good insulation properties, preventing direct contact between the positive and negative electrodes; 3. Nitride inorganic ceramics have excellent high-temperature resistance, improving the high-temperature shrinkage resistance of the separator, while also having good thermal conductivity, allowing heat to be transferred to other parts in a short time. Therefore, it can play a good supporting role at high temperatures, preventing battery short circuits caused by separator deformation and ensuring the safety performance of the battery at high temperatures.

[0052] In one embodiment, the composite ceramic diaphragm described in the second aspect is prepared using the preparation method described in the first aspect.

[0053] Preferably, the nitride inorganic ceramic includes at least one of boron nitride, aluminum nitride, silicon nitride, titanium nitride, and magnesium nitride.

[0054] Preferably, the boron nitride comprises hexagonal boron nitride and / or N-type cubic boron nitride.

[0055] Preferably, the ceramic further includes a second inorganic ceramic, which includes at least one of aluminum oxide, titanium dioxide, silicon dioxide, zirconium dioxide, molybdenum-doped silicon dioxide, zirconium boride, zirconium nitride ceramics, silicon boride, vanadium boride, titanium boride, magnesium boride, and inorganic ceramic solid electrolyte.

[0056] Preferably, the zirconium nitride compound includes at least one of ZrN, o-Zr3N4, and c-Zr3N4.

[0057] Preferably, the inorganic ceramic solid electrolyte includes at least one of lithium lanthanum zirconium oxide, lithium lanthanum titanate, tantalum-doped lithium lanthanum zirconium oxide, aluminum-doped lithium lanthanum zirconium oxide, lithium germanium phosphorus sulfide compound, lithium phosphorus sulfide chloride compound, and lithium germanium aluminum phosphate.

[0058] Preferably, the mass of the second inorganic ceramic accounts for 0%-95% of the mass of the first inorganic ceramic, for example, 0.01%, 0.05%, 0.1%, 0.3%, 0.5%, 0.8%, 1%, 1.5%, 2%, 2.5%, 3%, 4%, 4.5%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, or 95%.

[0059] Preferably, in the composite ceramic diaphragm, the particle size of the ceramic is 0.01μm-3μm, such as 0.01μm, 0.05μm, 0.1μm, 0.2μm, 0.3μm, 0.4μm, 0.5μm, 0.6μm, 0.7μm, 0.8μm, 0.9μm, 1μm, 1.5μm, 2μm, 2.5μm or 3μm, etc.

[0060] Preferably, based on the mass of the composite ceramic material as 100%, the mass content of the ceramic is 5%-100%, such as 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 97%, or 100%, etc., preferably 5%-95%, more preferably 50%-95%. If the ceramic content is too low, it cannot effectively provide high-temperature support; if the ceramic content is too high, the ceramic will block the pores of the diaphragm and hinder the penetration of the electrolyte.

[0061] Preferably, the composite ceramic material further includes a polymer binder. The polymer binder can bond the ceramic particles together, giving the composite ceramic diaphragm good flexibility, making it applicable to the field of flexible devices.

[0062] Preferably, the polymer binder includes at least one of polyethylene oxide, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, polyvinylidene fluoride-trifluorochloroethylene, polyacrylic acid, polyacrylic acid, polyacrylonitrile, perfluorosulfonic acid resin, lithium perfluorosulfonic acid resin, thermoplastic polyurethane, polyphenylene sulfide, polyethyleneimine, ethyl cyanoacrylate, vinylene polycarbonate, polypropylene polycarbonate, ethylene polycarbonate, polymalonate, polysuccinate, polyimide, polyetherimide, and polyethersulfone.

[0063] Preferably, the polymalonate includes at least one of polypentyl malonate, polyethylene malonate, polypropylene malonate, and hexanediol malonate.

[0064] Preferably, the polysuccinate includes at least one of polyethylene succinate and propylene succinate.

[0065] Preferably, based on the mass of the composite ceramic material (100%), the mass content of the polymer binder is 0%-95% and does not include endpoint values, such as 0.5%, 1%, 2%, 3%, 4%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, or 94%, etc., preferably 3%-95%, more preferably 3%-50%.

[0066] Preferably, the composite ceramic material further includes a dispersant, which includes at least one of nonionic surfactants, anionic surfactants, and cationic surfactants.

[0067] Preferably, the mass content of the dispersant is 0%-2% and does not exceed 0%, based on 100% of the mass of the composite ceramic material, for example, 0.05%, 0.1%, 0.3%, 0.5%, 1%, 1.2%, 1.5%, 1.8% or 2%, etc.

[0068] Preferably, the thickness of the composite ceramic diaphragm is 5μm-35μm, such as 5μm, 7μm, 8μm, 10μm, 12.5μm, 15μm, 17μm, 20μm, 23μm, 26μm, 30μm, 32μm, 34μm or 35μm.

[0069] Preferably, the porosity of the composite ceramic membrane is 30%-70%, such as 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, or 70%.

[0070] Thirdly, the present invention provides a battery comprising a positive electrode, a negative electrode, and a separator, wherein the separator is located between the positive electrode and the negative electrode, thereby isolating the positive electrode and the negative electrode, and the separator is a composite ceramic prepared by the method described in the first aspect or a composite ceramic separator as described in the second aspect.

[0071] Preferably, a flexible interface is formed between the composite ceramic separator and the positive electrode and / or between the composite ceramic separator and the negative electrode.

[0072] The battery of this invention exhibits significantly improved safety performance due to the use of the composite ceramic separator described herein. Furthermore, the inclusion of nitride inorganic ceramics in the ceramic enhances the battery's gravimetric energy density.

[0073] Preferably, the battery can be a solid-state battery or a semi-solid-state battery.

[0074] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0075] Compared with existing technologies, the present invention has the following beneficial effects:

[0076] (1) The method of the present invention allows the suspension to penetrate into the pores of the porous base membrane by applying the suspension to the surface of the porous base membrane and applying negative pressure. This allows the ceramic to enter the pores, and the ceramic particles can be evenly distributed in the pores of the porous base membrane. The ceramic particles in the pores can still play a stable supporting role at high temperature. When this composite ceramic separator is applied to a battery, it can directly contact the positive and negative electrodes respectively, thereby improving the safety performance of the battery.

[0077] (2) In the composite ceramic separator of the present invention, since the ceramic is located at least in the pores of the porous base membrane, compared with placing the ceramic on the surface of the base membrane, the ceramic in the pores can play a better stabilizing and supporting role, thus exhibiting better high-temperature mechanical properties and improving the high-temperature shrinkage resistance of the separator. Simultaneously, the presence of the ceramic in the pores avoids the problem of interface differences caused by direct contact between ceramic particles and the positive and negative electrodes. Furthermore, since the composite ceramic separator of the present invention contains at least nitride inorganic ceramics, the overall performance is further improved. Attached Figure Description

[0078] Figure 1 This is a schematic diagram of the structure of a composite ceramic membrane in one embodiment of the present invention, wherein 1-porous base membrane, 11-pores, and 2-ceramic. Detailed Implementation

[0079] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0080] In this embodiment of the invention, the base film used can be prepared by methods disclosed in the prior art or can be a commercially available product.

[0081] Example 1

[0082] A composite ceramic diaphragm, structural schematic diagram shown. Figure 1 The composite ceramic material includes a porous base membrane 1 and a composite ceramic material, wherein the composite ceramic material includes ceramic 2, wherein the ceramic 2 is formed at least in the pores 11 of the porous base membrane 1, and the particle size of the ceramic 2 is smaller than the pore size of the pores 11; the ceramic 2 includes a first inorganic ceramic, wherein the first inorganic ceramic is a nitride inorganic ceramic, and the particle size of the ceramic is 0.5 μm.

[0083] The nitride inorganic ceramic is hexagonal phase BN;

[0084] The composite ceramic material also includes a polymer binder and a dispersant, wherein the polymer binder is polyvinylidene fluoride (PVDF) and the dispersant is polyvinylpyrrolidone (PVP);

[0085] Based on the mass of the composite ceramic material being 100%, the mass content of the ceramic is 90%, the mass content of the polymer binder is 9%, and the mass content of the dispersant is 1%.

[0086] The method for preparing the composite ceramic diaphragm provided in this embodiment includes the following steps:

[0087] Hexagonal BN particles with a particle size of 0.5 μm, along with PVP and PVDF, were dispersed in N,N-dimethylformamide (DMF). After stirring, a suspension with a solid content of 10% was obtained.

[0088] A porous membrane (polypropylene membrane) with a pore size of 5 μm and a porosity of 50% was used. The above suspension was dropped onto the surface of the porous membrane at a rate of 0.2 mL / cm². 2 Then, the suspension is filtered to allow it to penetrate into the porous base membrane. The negative pressure generated during the filtration process is 300 mbar. After the negative pressure is maintained for 1 minute, the vacuum is removed. The membrane after filtration is air-dried and then placed in a vacuum oven at 60°C for 24 hours to obtain the composite ceramic membrane.

[0089] Example 2

[0090] A composite ceramic membrane includes a porous base membrane and a composite ceramic material, wherein the composite ceramic material includes ceramics, the ceramics being formed at least in the pores of the porous base membrane, and the particle size of the ceramics being smaller than the pore size of the pores; the ceramics include a first inorganic ceramic, the first inorganic ceramic being a nitride inorganic ceramic, and the particle size of the ceramics being 1 μm;

[0091] The nitride inorganic ceramic is AlN;

[0092] The composite ceramic material also includes a polymer binder and a dispersant, wherein the polymer binder is polyethylene oxide (PEO) and the dispersant is PVP;

[0093] Based on the mass of the composite ceramic material as 100%, the mass content of the ceramic is 85%, the mass content of the polymer binder is 14.5%, and the mass content of the dispersant is 0.5%.

[0094] The method for preparing the composite ceramic diaphragm provided in this embodiment includes the following steps:

[0095] AlN particles with a particle size of 1 μm, along with PVP and PEO, were dispersed in N,N-dimethylacetamide (DMAC). After stirring, a suspension with a solid content of 15% was obtained.

[0096] A porous membrane (polypropylene membrane) with a pore size of 10 μm and a porosity of 80% was used. The above suspension was dropped onto the surface of the porous membrane at a rate of 0.3 mL / cm². 2 Then, the suspension is filtered to allow it to penetrate into the porous base membrane. The negative pressure generated during the filtration process is 400 mbar. After the negative pressure is maintained for 3 minutes, the vacuum is removed. The membrane after filtration is air-dried and then placed in a vacuum oven at 80°C for 10 hours to obtain the composite ceramic membrane.

[0097] Example 3

[0098] A composite ceramic membrane includes a porous base membrane and a composite ceramic material, wherein the composite ceramic material includes ceramics, the ceramics being formed at least in the pores of the porous base membrane, and the particle size of the ceramics being smaller than the pore size of the pores; the ceramics include a first inorganic ceramic, the first inorganic ceramic being a nitride inorganic ceramic, and the particle size of the ceramics being 0.05 μm;

[0099] The nitride inorganic ceramic is Si3N4;

[0100] The composite ceramic material also includes a polymer binder and a dispersant, wherein the polymer binder is polymethyl methacrylate (PMMA) and the dispersant is PVP;

[0101] Based on the mass of the composite ceramic material as 100%, the mass content of the ceramic is 65%, the mass content of the polymer binder is 33.5%, and the mass content of the dispersant is 1.5%.

[0102] The method for preparing the composite ceramic diaphragm provided in this embodiment includes the following steps:

[0103] Si3N4 particles with a particle size of 0.05 μm, along with PVP and PMMA, were dispersed in N-methylpyrrolidone (NMP). After stirring, a suspension with a solid content of 8% was obtained.

[0104] A porous membrane (polypropylene membrane) with a pore size of 0.5 μm and a porosity of 40% was used. The above suspension was dropped onto the surface of the porous membrane at a rate of 0.25 mL / cm². 2 Then, the suspension is filtered to allow it to penetrate into the porous base membrane. The negative pressure generated during the filtration process is 200 mbar. After the negative pressure is maintained for 5 minutes, the vacuum is removed. The membrane after filtration is air-dried and then placed in a vacuum oven at 90°C for 8 hours to obtain the composite ceramic membrane.

[0105] Example 4

[0106] A composite ceramic membrane includes a porous base membrane and a composite ceramic material, wherein the composite ceramic material includes ceramics, the ceramics being formed at least in the pores of the porous base membrane, and the particle size of the ceramics being smaller than the pore size of the pores; the ceramics include a first inorganic ceramic, the first inorganic ceramic being a nitride inorganic ceramic, and the particle size of the ceramics being 0.2 μm;

[0107] The nitride inorganic ceramic is AlN;

[0108] The composite ceramic material also includes a polymer binder and a dispersant, wherein the polymer binder is polyacrylonitrile (PAN) and the dispersant is PVP;

[0109] Based on the mass of the composite ceramic material as 100%, the mass content of the ceramic is 85%, the mass content of the polymer binder is 14.5%, and the mass content of the dispersant is 0.5%.

[0110] The method for preparing the composite ceramic diaphragm provided in this embodiment includes the following steps:

[0111] AlN particles with a particle size of 0.2 μm, along with PVP and PAN, were dispersed in DMF and stirred to obtain a suspension with a solid content of 5%.

[0112] A porous membrane (polyethylene membrane) with a pore size of 2 μm and a porosity of 55% was used. The above suspension was dropped onto the surface of the porous membrane at a rate of 0.09 mL / cm². 2 Then, the suspension is filtered to allow it to penetrate into the porous base membrane. The negative pressure generated during the filtration process is 150 mbar. After the negative pressure is maintained for 4.5 min, the vacuum is removed. The membrane after filtration is air-dried and then placed in a vacuum oven at 70°C for 18 hours to obtain the composite ceramic membrane.

[0113] Example 5

[0114] A composite ceramic membrane includes a porous base membrane and a composite ceramic material. The composite ceramic material includes ceramics, which are formed at least in the pores of the porous base membrane. The particle size of the ceramics is smaller than the pore size of the pores. The ceramics include a first inorganic ceramic and a second inorganic ceramic. The first inorganic ceramic is a nitride inorganic ceramic, and the second inorganic ceramic is lithium lanthanum zirconium oxide (LLZO). The mass of the second inorganic ceramic accounts for 50% of the mass of the first inorganic ceramic, and the particle size of the ceramics is 0.5 μm.

[0115] The nitride inorganic ceramic is cubic phase boron nitride;

[0116] The composite ceramic material also includes a polymer binder and a dispersant, wherein the polymer binder is PVDF and the dispersant is PVP;

[0117] Based on the mass of the composite ceramic material being 100%, the mass content of the ceramic is 88%, the mass content of the polymer binder is 11%, and the mass content of the dispersant is 1%.

[0118] The method for preparing the composite ceramic diaphragm provided in this embodiment includes the following steps:

[0119] Cubic boron nitride particles with a particle size of 0.5 μm, LLZO particles with a particle size of 0.5 μm, PVP and PVDF were dispersed in DMF, and after stirring, a suspension with a solid content of 15% was obtained.

[0120] A porous membrane (polypropylene membrane) with a pore size of 10 μm and a porosity of 80% was used. The above suspension was dropped onto the surface of the porous membrane at a rate of 0.3 mL / cm². 2 Then, the suspension is filtered to allow it to penetrate into the porous base membrane. The negative pressure generated during the filtration process is 400 mbar. After the negative pressure is maintained for 3 minutes, the vacuum is removed. The membrane after filtration is air-dried and then placed in a vacuum oven at 80°C for 10 hours to obtain the composite ceramic membrane.

[0121] Example 6

[0122] A composite ceramic membrane and its preparation method are disclosed, which differ from Example 1 only in that the composite ceramic membrane does not contain the dispersant PVP.

[0123] Example 7

[0124] A composite ceramic diaphragm and its preparation method differ from Example 1 only in that the content of dispersant PVP is 3% and the content of polymer binder is 7%.

[0125] Example 8

[0126] A composite ceramic diaphragm and its preparation method differ from Example 1 only in that the amount of solvent DMF is changed in the preparation method of the composite ceramic diaphragm so that the solid content of the suspension is 3%.

[0127] Example 9

[0128] A composite ceramic diaphragm and its preparation method differ from Example 1 only in that the amount of solvent DMF is changed in the preparation method of the composite ceramic diaphragm so that the solid content of the suspension is 22%.

[0129] Example 10

[0130] A composite ceramic diaphragm and its preparation method are disclosed, differing from Example 1 only in that the negative pressure in the preparation method of the composite ceramic diaphragm is 280 mbar.

[0131] Example 11

[0132] A composite ceramic diaphragm and its preparation method are disclosed, differing from Example 1 only in that the negative pressure in the preparation method of the composite ceramic diaphragm is 520 mbar.

[0133] Example 12

[0134] A composite ceramic diaphragm and its preparation method are different from those in Example 1, except that the negative pressure duration in the preparation method of the composite ceramic diaphragm is 20s.

[0135] Example 13

[0136] A composite ceramic diaphragm and its preparation method are different from those in Example 1, except that the negative pressure duration in the preparation method of the composite ceramic diaphragm is 5.2 min.

[0137] Example 14

[0138] A composite ceramic diaphragm and its preparation method differ from Example 1 only in that the drop volume per unit area in the preparation method of the composite ceramic diaphragm is 0.05 mL / cm². 2 .

[0139] Example 15

[0140] A composite ceramic diaphragm and its preparation method differ from Example 1 only in that the drop volume per unit area in the preparation method of the composite ceramic diaphragm is 0.38 mL / cm². 2 .

[0141] Comparative Example 1

[0142] A composite ceramic diaphragm and its preparation method are different from those in Example 1, except that the composite ceramic diaphragm preparation method does not involve filtration.

[0143] Comparative Example 2

[0144] A composite ceramic diaphragm and its preparation method are disclosed. The only difference between this method and Example 1 is that the nitride inorganic ceramic in Example 1 is replaced with Al2O3 in the preparation method of the composite ceramic diaphragm.

[0145] Comparative Example 3

[0146] A composite ceramic diaphragm and its preparation method are disclosed. The only difference between this method and Example 1 is that the nitride inorganic ceramic in Example 1 is replaced with LLZO in the preparation method of the composite ceramic diaphragm.

[0147] Application Example 1

[0148] A lithium-ion battery includes a positive electrode, a negative electrode, a separator (the composite ceramic separator of Example 1), and an electrolyte. The preparation method of the lithium-ion battery includes the following steps:

[0149] According to the mass ratio of lithium iron phosphate (LFP): Super P: PVDF = 8:1:1, LFP, Super P and PVDF are dispersed in DMF, and the solid content is controlled at 60% to obtain a positive electrode slurry. The positive electrode slurry is coated onto aluminum foil with a thickness of 100μm using a scraper and dried for later use.

[0150] The electrolyte composition is as follows: 1 mol / L LiPF6 is used as the electrolyte, and a mixture of EC:DMC (volume ratio) = 1:1 is used as the solvent.

[0151] A coin cell, model 2032, was assembled using a 100μm thick lithium sheet as the counter electrode in an inert gas glove box where the water and oxygen content were both below 0.1ppm.

[0152] Application Example 2-15

[0153] A lithium-ion battery differs from Application Example 1 only in that the composite ceramic separator of Example 2-15 is used instead of the composite ceramic separator of Example 1.

[0154] Application Comparative Examples 1-3

[0155] A lithium-ion battery differs from Application Example 1 only in that the composite ceramic separator of Example 1 is replaced by the composite ceramic separator of Example 1-3.

[0156] Performance testing:

[0157] (1) Diaphragm thickness: The thickness of the diaphragm is measured using a micrometer.

[0158] (2) Porosity of the diaphragm: The porosity of the diaphragm was tested using a mercury porosimeter.

[0159] (3) Heat shrinkage rate of the diaphragm: Place the diaphragm in an oven at 150℃ and keep it warm for 1 hour. Take it out and measure its longitudinal and transverse lengths before and after heat treatment. Calculate the percentage of the change in longitudinal and transverse lengths relative to the initial length. The initial length is recorded as d0 and the length after shrinkage is recorded as d1. Heat shrinkage rate = (d0-d1) / d0×100%.

[0160] (4) Discharge capacity: Charge and discharge test at room temperature with a current density of 0.1C.

[0161] (5) Interface impedance: The interface impedance of the battery after one cycle is tested by calling the EIS program through the electrochemical workstation and setting the frequency range to 1Hz~1MHz.

[0162] The thickness, porosity, and thermal shrinkage rate of the composite ceramic membranes of Examples 1-15 and Comparative Examples 1-3 were tested according to the above test methods, and the test results are shown in Table 1.

[0163] The interface impedance and discharge capacity of lithium-ion batteries corresponding to use cases 1-15 and application comparison examples 1-3 were tested, and the results are shown in Table 2.

[0164] Table 1

[0165]

[0166]

[0167] Table 2

[0168]

[0169]

[0170] As shown in Tables 1 and 2, the composite ceramic separator of the present invention exhibits excellent shrinkage resistance, effectively improving battery safety performance. Furthermore, because the ceramic is introduced into the pores of the base membrane using negative pressure in the preparation method, the problem of poor interfacial properties caused by contact between the ceramic on the base membrane surface and the positive and negative electrodes is avoided.

[0171] A comparison of Examples 1 and 6-7 shows that adding a dispersant can improve the dispersibility of ceramic particles in the suspension. However, excessive dispersant content can cause instability in the suspension, thereby affecting the dripping effect and the uniformity of ceramic particle dispersion in the final composite ceramic membrane, thus affecting the performance of the composite ceramic membrane. Moreover, excessive dispersant in Example 7 reduces the binder content in the composite ceramic membrane, resulting in lower adhesion of ceramic particles in the composite membrane and affecting the anti-shrinkage performance of the composite ceramic membrane.

[0172] A comparison of Examples 1 and 8-9 shows that a solid content of 5%-20% in the suspension is beneficial for ceramic particles to fully enter the pores of the porous base membrane and for the ceramics to be evenly distributed in the pores, thereby improving the performance of the composite membrane.

[0173] A comparison of Examples 1, 10-11, and 12-13 shows that the magnitude and duration of negative pressure have a significant impact on the performance of the composite ceramic diaphragm. If the negative pressure is too small or the duration is too short, the ceramic particles cannot fully enter the pores of the porous base membrane. If the negative pressure is too large or the duration is too long, the ceramic particles may pass through the pores of the porous base membrane but not remain in the pores. All of these factors will result in a low ceramic content in the composite ceramic diaphragm, which will degrade the diaphragm's anti-shrinkage performance.

[0174] A comparison between Example 1 and Examples 14-15 shows that the amount of suspension added to the surface of the porous membrane is 0.08 mL / cm². 2 -0.35mL / cm 2 At the same time, the content of ceramic particles in the composite ceramic diaphragm can be made appropriate without causing pore blockage. The combined effect of the above two factors makes the performance of the composite ceramic diaphragm better.

[0175] By comparing Example 1 with Comparative Example 1, it can be seen that Comparative Example 1 did not undergo negative pressure treatment, resulting in the ceramic particles remaining on the surface. This leads to poor interfacial contact and prevents the ceramic particles from effectively providing stable support, thus reducing the resistance to heat shrinkage. Therefore, the interfacial performance and resistance to heat shrinkage of Comparative Example 1 are inferior to those of Example 1.

[0176] As can be seen from the comparison between Example 1 and Comparative Examples 2-3, when Al2O3 and LLZO are used in composite membranes, their heat shrinkage resistance is worse than that of nitride inorganic ceramics.

[0177] The applicant declares that the detailed method of the present invention is illustrated by the above embodiments, but the present invention is not limited to the above detailed method, that is, it does not mean that the present invention must rely on the above detailed method to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions of the raw materials of the product of the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for preparing a composite ceramic diaphragm, characterized in that, The composite ceramic separator is used in a battery, which includes a positive electrode and a negative electrode. The composite ceramic separator is used to form a flexible interface with the positive electrode and / or with the negative electrode. The preparation method includes the following steps: A suspension comprising ceramics, polymer binders, dispersants, and organic solvents is provided, wherein the solid content of the suspension is 5%-20%; The suspension is applied to the surface of a porous membrane with a porosity of 40%-80% and a pore size of 0.5µm-10µm. The amount of suspension applied per unit area of ​​the porous membrane surface is 0.08mL / cm². 2 -0.35mL / cm 2 A negative pressure is applied, the magnitude of which is 100mbar-500mbar, and the duration of which is 30s-5min, so that the suspension penetrates into the pores of the porous base membrane. After drying, a composite ceramic membrane is obtained. Wherein, the particle size of the ceramic is smaller than the pore size of the pores; Based on the dry weight of the suspension, the ceramic content is 50%-95%, the polymer binder content is 9%-50%, and the dispersant content is 0%-2% and contains no 0%; The ceramic comprises a first inorganic ceramic and a second inorganic ceramic, wherein the first inorganic ceramic is a nitride inorganic ceramic, and the second inorganic ceramic is an inorganic ceramic solid electrolyte, and the mass of the second inorganic ceramic accounts for 50-95% of the mass of the first inorganic ceramic.

2. The method for preparing the composite ceramic diaphragm according to claim 1, characterized in that, The ceramic has a particle size of 0.01µm-3µm.

3. The method for preparing the composite ceramic diaphragm according to claim 1, characterized in that, The nitride inorganic ceramics include at least one of boron nitride, aluminum nitride, silicon nitride, titanium nitride, and magnesium nitride.

4. The method for preparing the composite ceramic diaphragm according to claim 3, characterized in that, The boron nitride includes hexagonal boron nitride and / or N-type cubic boron nitride.

5. The method for preparing the composite ceramic diaphragm according to claim 1, characterized in that, The inorganic ceramic solid electrolyte includes at least one of lithium lanthanum zirconium oxide, lithium lanthanum titanate, tantalum-doped lithium lanthanum zirconium oxide, aluminum-doped lithium lanthanum zirconium oxide, lithium germanium phosphorus sulfide, lithium phosphorus sulfide chloride, and lithium germanium aluminum phosphate.

6. The method for preparing the composite ceramic diaphragm according to claim 1, wherein the polymer binder comprises at least one selected from polyethylene oxide, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, polyvinylidene fluoride-trifluorochloroethylene, polyacrylic acid, polyacrylonitrile, perfluorosulfonic acid resin, lithium perfluorosulfonic acid resin, thermoplastic polyurethane, polyphenylene sulfide, polyethyleneimine, ethyl cyanoacrylate, vinylene polycarbonate, polypropylene polycarbonate, ethylene polycarbonate, polymalonate, polysuccinate, polyimide, polyetherimide, and polyethersulfone.

7. The method for preparing the composite ceramic diaphragm according to claim 6, characterized in that, The polymalonate substances include at least one of polypentyl malonate, polyethylene malonate, polypropylene malonate, and hexanediol malonate.

8. The method for preparing the composite ceramic diaphragm according to claim 6, characterized in that, The polysuccinates include at least one of polyethylene succinate and propylene succinate.

9. The method for preparing the composite ceramic diaphragm according to claim 1, characterized in that, The organic solvent includes at least one of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, and acetonitrile.

10. The method for preparing the composite ceramic membrane according to claim 1, wherein the dispersant comprises at least one of a nonionic surfactant, anionic surfactant, and cationic surfactant.

11. The method for preparing the composite ceramic diaphragm according to claim 1, characterized in that, The suspension is applied to the surface of the porous base membrane by dropwise addition.

12. The method for preparing the composite ceramic diaphragm according to claim 1, characterized in that, The method of applying negative pressure is as follows: a vacuum filtration device is used to perform vacuum filtration on a porous base membrane to which a suspension has been applied.

13. The method for preparing the composite ceramic diaphragm according to claim 1, characterized in that, The porous base membrane includes any one of porous polyethylene membrane, porous polypropylene membrane, porous polyethylene / polypropylene composite membrane, porous cellulose membrane, porous polyethylene terephthalate membrane, porous polyimide membrane, porous polyvinylidene fluoride membrane, porous polyvinylidene fluoride-hexafluoropropylene copolymer membrane, or porous polytetrafluoroethylene membrane.

14. The method for preparing the composite ceramic diaphragm according to claim 1, characterized in that, In the porous base membrane, the pore size is 0.03µm-5µm.

15. A composite ceramic diaphragm prepared by the method described in claim 1, characterized in that, The composite ceramic membrane comprises a porous base membrane and a composite ceramic material, wherein the composite ceramic material comprises ceramic, a polymer binder and a dispersant, and the ceramic is formed at least in the pores of the porous base membrane.

16. The composite ceramic diaphragm according to claim 15, characterized in that, The nitride inorganic ceramics include at least one of boron nitride, aluminum nitride, silicon nitride, titanium nitride, and magnesium nitride.

17. The composite ceramic diaphragm according to claim 16, characterized in that, The boron nitride includes hexagonal boron nitride and / or N-type cubic boron nitride.

18. The composite ceramic diaphragm according to claim 15, characterized in that, The inorganic ceramic solid electrolyte includes at least one of lithium lanthanum zirconium oxide, lithium lanthanum titanate, tantalum-doped lithium lanthanum zirconium oxide, aluminum-doped lithium lanthanum zirconium oxide, lithium germanium phosphorus sulfide, lithium phosphorus sulfide chloride, and lithium germanium aluminum phosphate.

19. The composite ceramic diaphragm according to claim 15, characterized in that, In the composite ceramic diaphragm, the particle size of the ceramic is 0.01µm-3µm.

20. The composite ceramic diaphragm according to claim 15, characterized in that, The polymer binder includes at least one of polyethylene oxide, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, polyvinylidene fluoride-trifluorochloroethylene, polyacrylic acid, polyacrylonitrile, perfluorosulfonic acid resin, lithium perfluorosulfonic acid resin, thermoplastic polyurethane, polyphenylene sulfide, polyethyleneimine, ethyl cyanoacrylate, vinylene polycarbonate, polypropylene polycarbonate, ethylene polycarbonate, polymalonate, polysuccinate, polyimide, polyetherimide, and polyethersulfone.

21. The composite ceramic diaphragm according to claim 20, characterized in that, The polymalonate substances include at least one of polypentyl malonate, polyethylene malonate, polypropylene malonate, and hexanediol malonate.

22. The composite ceramic diaphragm according to claim 20, characterized in that, The polysuccinates include at least one of polyethylene succinate and propylene succinate.

23. The composite ceramic diaphragm according to claim 15, characterized in that, The dispersant includes at least one of nonionic surfactants, anionic surfactants, and cationic surfactants.

24. The composite ceramic diaphragm according to claim 15, characterized in that, The thickness of the composite ceramic diaphragm is 5μm-35μm.

25. The composite ceramic diaphragm according to claim 15, characterized in that, The porosity of the composite ceramic diaphragm is 30%-70%.

26. A battery comprising a positive electrode, a negative electrode, and a separator, the separator being located between the positive electrode and the negative electrode to isolate the positive electrode and the negative electrode, characterized in that, The diaphragm is a composite ceramic diaphragm prepared by the method according to any one of claims 1-14 or a composite ceramic diaphragm according to any one of claims 15-25.

27. The battery according to claim 26, characterized in that, The battery is a quasi-solid-state battery or a semi-solid-state battery.

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