Lithium battery coated separator and method for preparing the same, lithium ion battery and electric device

Abstract

The application discloses a lithium battery coating diaphragm and a preparation method thereof, a lithium ion battery and an electric device, and relates to the technical field of lithium ion batteries. The application forms a diaphragm coating layer by using core-shell ceramic particles, the core-shell ceramic particles include ceramic microspheres and radial crystal clusters growing on the surface of the ceramic microspheres, the core-shell ceramic is in a radial / cluster shape, the nanometer crystal clusters grow from the center to the outside, a multi-stage pore structure is built by stacking, the porosity is higher, the pore channel is tortuous and the connectivity is strong. The core-shell ceramic particles have a higher specific surface area and a liquid absorption rate, the electrolyte contact angle is extremely low, the electrolyte has excellent wettability, the tortuosity is lower, the ion migration resistance is lower and the ion conductivity is higher in the use of the assembled battery. The lithium battery coating diaphragm has a wide application prospect in high-rate fast charging, soft package batteries and long cycle operation.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery technology, and more specifically, to lithium-ion battery coated separators and their preparation methods, lithium-ion batteries, and electrical devices. Background Technology

[0002] Lithium-ion batteries are now widely used in new energy vehicles, consumer electronics, and energy storage. The separator, as a core insulating component, directly affects battery safety, fast-charging capability, and cycle life. Currently, mainstream polyolefin separators suffer from defects such as easy shrinkage and melting at high temperatures, poor electrolyte wettability, and weak resistance to lithium dendrite formation. These defects can easily lead to safety hazards such as short circuits and thermal runaway under high-rate charge / discharge and high-temperature conditions. To improve the overall performance of separators, the industry commonly uses inorganic powders such as nano-alumina and boehmite for ceramic coating modification, effectively enhancing the separator's heat resistance and mechanical protection capabilities.

[0003] The existing ceramic-coated separators have the following problems: (1) Most ceramic coatings are solid particles stacked together, which have insufficient adsorption and storage capacity for electrolyte and increased impedance; (2) The internal channels are tortuous and the pore structure is simple, which has problems such as slow electrolyte permeation rate and large ion conduction resistance, and cannot meet the requirements of high-rate fast charging; (3) Traditional ceramic coatings are brittle and are prone to micro-cracks and coating powdering and peeling during battery winding and bending processes.

[0004] Therefore, there is an urgent need to optimize ceramic-coated separators to improve their wettability with electrolytes, thereby enabling them to have lower ion migration resistance and higher ion conductivity in battery assembly.

[0005] In view of this, the present invention is proposed. Summary of the Invention

[0006] The purpose of this invention is to provide a lithium-ion battery coated separator and its preparation method, a lithium-ion battery, and an electrical device, which aims to improve the wettability of the electrolyte and increase the ionic conductivity.

[0007] This invention is implemented as follows: In a first aspect, the present invention provides a lithium battery coated separator, comprising a base film and a coating on at least one side of the base film; the coating contains core-shell ceramic particles and a binder polymer, wherein the core-shell ceramic particles include ceramic microspheres and crystal clusters growing radially on the surface of the ceramic microspheres, and the aspect ratio of the crystal clusters is 5:1 to 22:1.

[0008] In an optional embodiment, the coating contains 94% to 99% core-shell ceramic particles and 1% to 6% binder polymer by mass fraction; Preferably, the coating thickness is 1μm to 5μm; Preferably, the ceramic microspheres are made of at least one of Al2O3, boehmite, SiO2, and TiO2; the metal element contained in the crystal cluster is selected from at least one of zinc, aluminum, and zirconium. Preferably, the crystal cluster is rod-shaped; Preferably, the ceramic microspheres have a diameter of 0.3 μm to 1.5 μm, a surface cluster length of 20 nm to 500 nm, a surface cluster diameter of 20 nm to 150 nm, a cluster coverage of 80% to 95%, and a cluster aspect ratio of 8:1 to 18:1. Preferably, the core-shell ceramic particles have a particle size D50 of 0.6 μm to 3.5 μm, a D90 of ≤ 5.2 μm, and a particle size distribution Span of ≤ 0.95; Preferably, the specific surface area of ​​the core-shell ceramic particles is 25 m². 2 / g~68m 2 / g, with a pore size of 80nm~220nm and a porosity of 58%~72%; Preferably, the electrolyte contact angle of the core-shell ceramic particles is ≤20°.

[0009] In an optional embodiment, the base membrane is a polyolefin separator; Preferably, the base film is selected from at least one of PE and PP; Preferably, the thickness of the base film is 5μm to 10μm.

[0010] In a second aspect, the present invention provides a method for preparing a lithium battery coated separator according to any of the foregoing embodiments, comprising: performing surface activation treatment on solid spherical ceramic particles to make the surface contain hydroxyl groups and etching sites, thereby obtaining activated particles; A seed layer containing the target metal is formed on the surface of activated particles, followed by the growth of crystal clusters to prepare core-shell ceramic particles; the target metal is selected from at least one of zinc, aluminum and zirconium. A coating slurry is prepared using core-shell ceramic particles and a coating is formed on at least one side of the base film.

[0011] In an optional embodiment, the step of preparing activated particles includes: treating solid spherical ceramic particles in an inorganic alkaline solution, followed by washing and drying; Preferably, the concentration of the inorganic alkali solution is 0.5 mol / L to 3.0 mol / L, and the treatment time is 20 min to 60 min; Preferably, the inorganic alkaline solution is selected from at least one of sodium hydroxide solution and potassium hydroxide solution.

[0012] In an optional embodiment, the step of forming a seed layer containing the target metal on the surface of the activated particles includes: immersing the activated particles in a precursor solution containing the target metal ions, and after impregnation and drying, calcining them. Preferably, the precursor solution is a solution or sol, and the preparation steps of the precursor solution include: mixing and dissolving the metal salt and the solvent, adding the acid corresponding to the metal salt dropwise, adjusting the pH value to 3.5-6.0, and continuing to stir for 30 min to 60 min to obtain a precursor solution with a concentration of 0.05 mol / L-0.25 mol / L; the metal salt is selected from at least one of zinc acetate dihydrate, zinc nitrate hexahydrate, aluminum nitrate, and zirconium nitrate. Preferably, the soaking and drying steps are repeated 1 to 5 times; Preferably, ultrasonic impregnation is used, with each impregnation lasting 30 to 60 minutes, followed by centrifugation to obtain the precipitate. Preferably, during the drying process after impregnation, the drying temperature is controlled at 110℃~130℃ and the drying time is 10min~30min; Preferably, the calcination temperature is 300℃~400℃ and the calcination time is 30min~60min.

[0013] In an optional embodiment, the step of growing crystal clusters includes: dispersing activated particles loaded with seed crystal layers in a growth solution and performing a hydrothermal reaction to obtain a core-shell structure precursor; washing, drying or calcining the core-shell structure precursor to prepare core-shell ceramic particles; wherein the growth solution contains metal salts, alkali sources and structure directing agents. Preferably, the hydrothermal reaction temperature is 80℃~220℃ and the hydrothermal reaction time is 2h~48h; more preferably, the hydrothermal reaction temperature is 90℃~95℃ and the hydrothermal reaction time is 4h~8h. Preferably, the concentration of the metal element in the growth solution is 0.05 mol / L to 0.25 mol / L; Preferably, the alkali source is selected from at least one of hexamethylenetetramine, hexamethylenetetramine, urea, and triethanolamine; the molar ratio of the amount of the alkali source to the metal element in the metal salt is (0.5~1.5):1; Preferably, the structure-directing agent is selected from at least one of polyethyleneimine and polyethylene glycol; the ratio of the mass of the structure-directing agent to the molar amount of the metal element in the metal salt is (0.1~1.5) g: (5~25) mmol.

[0014] In an optional embodiment, the preparation step of the coating slurry includes: mixing core-shell ceramic particles, binder polymer and water, wherein the mass percentages of each component in the slurry are: core-shell ceramic particles 4%~45%, binder polymer 0.5%~3%, and deionized water 50%~80%; Preferably, the coating slurry is applied to the base film by scraping and then dried.

[0015] Thirdly, the present invention provides a lithium-ion battery, comprising any of the lithium-ion coated separators described in the foregoing embodiments or lithium-ion coated separators prepared by any of the preparation methods described in the foregoing embodiments.

[0016] Fourthly, the present invention provides an electrical device including the lithium-ion battery of the aforementioned embodiments.

[0017] This invention offers the following advantages: It utilizes core-shell ceramic particles to form a separator coating. These particles comprise ceramic microspheres and clusters of crystals with a specific aspect ratio grown radially on the surface of the microspheres. The core-shell ceramics exhibit a radial / flower-like shape, with nanocrystal clusters growing outwards from the center, creating a hierarchical porous structure with higher porosity and tortuous, highly interconnected pores. These core-shell ceramic particles possess a high specific surface area and electrolyte absorption rate, exhibiting an extremely low electrolyte contact angle and excellent wettability. Their low tortuosity results in lower ion migration resistance and higher ionic conductivity during battery assembly. The lithium-ion battery coated separator provided by this invention has broad application prospects in high-rate fast charging, pouch batteries, and long-cycle operation. Attached Figure Description

[0018] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of a lithium battery coated separator provided in an embodiment of the present invention. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0021] This invention introduces new structural materials into the separator coating, highlighting the advantages of the material structure and upgrading the performance of existing mainstream ceramic-coated separators, providing a technical path to solve the demand of lithium-ion batteries for fast-charging and long-life separators.

[0022] This invention provides a lithium battery coated separator, such as... Figure 1 As shown, the lithium-ion battery coated separator includes a base film and a coating on at least one surface of the base film. The coating contains core-shell ceramic particles and a binder polymer; the core-shell ceramic particles include ceramic microspheres (i.e.,... Figure 1 The central ceramic particles in the ceramic microspheres and the rod-shaped crystal clusters growing radially on the surface of the ceramic microspheres (i.e., Figure 1 The core-shell ceramic particles (shell nanorods) have a crystal cluster aspect ratio of 5:1 to 22:1, such as 5:1, 8:1, 10:1, 12:1, 14:1, 16:1, 18:1, 20:1, 22:1, etc., or any value between adjacent values, preferably 8:1 to 18:1. The core-shell ceramic particles use solid ceramic microspheres as the core, with rod-shaped crystal clusters growing radially on the surface to form a complete spherical core-shell configuration.

[0023] It should be noted that replacing conventional ceramics with nanorod core-shell ceramic particles in existing conventional ceramic systems can improve coating porosity and electrolyte retention while maintaining heat resistance. Specifically, the core-shell ceramic particles are radial / flower-like, with nanorods growing outward from the center, stacking to construct a hierarchical porous structure, resulting in higher porosity and tortuous, highly interconnected pores. These core-shell ceramic particles have a high specific surface area and electrolyte absorption rate, an extremely low electrolyte contact angle, excellent wettability to electrolytes, and low tortuosity, giving them lower ion migration resistance and higher ionic conductivity when used in assembled batteries.

[0024] The surface crystal clusters of the core-shell ceramic particles provided by this invention are not limited to nanorod shapes; nanosheets and other structures also have the same effect. In addition to solid spheres, other irregular shapes of the central structure can also provide a certain mechanical strength.

[0025] The metal element contained in the rod-shaped crystal cluster is selected from at least one of zinc, aluminum, and zirconium, and can be any one or more of these metal elements. All of these metal elements are suitable for forming the shell structure of rod-shaped crystal clusters on the surface of ceramic microspheres, and can all improve the wettability of the electrolyte.

[0026] In some embodiments, the coating contains 94%–99% core-shell ceramic particles and 1–6% binder polymer by mass fraction. The mass fraction of the core-shell ceramic particles can be 94%, 95%, 96%, 97%, 98%, 99%, etc., or any value between these adjacent values; the mass fraction of the binder polymer can be 1%, 2%, 3%, 4%, 5%, 6%, etc., or any value between these adjacent values. The coating may also contain a portion of conventional ceramics (i.e., ceramic particles without rod-shaped crystal clusters), the specific proportion of which is not limited. The conventional ceramic particles include at least one of alumina (Al2O3) and boehmite (γ-AlOOH), with a particle size of 0.3–1.5 μm and an irregular morphology. The coating thickness is 1 μm–5 μm, such as 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, etc. The coating thickness is preferably within the above range; excessive thickness or thinness is not conducive to improving ionic conductivity.

[0027] In some embodiments, the ceramic microspheres are made of at least one of Al2O3, boehmite, SiO2, and TiO2, and the material of the ceramic microspheres can be any one or more of the above. The diameter of the ceramic microspheres is 0.3μm to 1.5μm, such as 0.3μm, 0.5μm, 0.8μm, 1.0μm, 1.3μm, 1.5μm, etc., or any value between adjacent values ​​above. The surface crystal cluster length of the ceramic microspheres is 20nm to 500nm, such as 20nm, 50nm, 100nm, 200nm, 300nm, 400nm, 500nm, etc., or any value between adjacent values ​​above; the diameter of the surface crystal clusters is 20nm to 150nm, such as 20nm, 50nm, 80nm, 100nm, 130nm, 150nm, etc., or any value between adjacent values ​​above. By controlling the length and diameter of surface crystal clusters, a more suitable aspect ratio can be achieved, which is more conducive to improving the wettability of the electrolyte and increasing the ionic conductivity of the battery. A three-dimensional, multi-level rough surface assembled from nanoscale primary structural units allows for the control of the specific surface area and packing porosity of the material by adjusting the diameter of the solid spheres in the core-shell ceramic structure and the length of the surface crystal clusters, thereby affecting the gas permeability and electrolyte storage capacity. The crystal cluster coverage ranges from 80% to 95%, and can be as follows: 80%, 83%, 85%, 88%, 90%, 93%, 95%, etc.

[0028] In some embodiments, the core-shell ceramic particles are monodisperse as a whole, without agglomeration or breakage, and the particle size D50 is 0.6μm~3.5μm, such as 0.6μm, 1.0μm, 1.5μm, 2.0μm, 2.5μm, 3.0μm, 3.5μm, etc., or any value between these adjacent values. The particle size D90 of the core-shell ceramic particles is ≤5.2μm, the particle size distribution Span is ≤0.95, the particle uniformity is extremely high, and the morphology is highly regular.

[0029] In some embodiments, the core-shell ceramic particles have a dense, uniformly oriented cluster arrangement, without any collapse or cross-adhesion, and a specific surface area of ​​25 m². 2 / g~68m 2 / g, with controllable pore structure, the stacking can form a continuous hierarchical pore structure with pore size concentrated in the range of 80nm~220nm, porosity of 58%~72%, and electrolyte contact angle ≤20°. Numerous nanometer to submicron-sized gaps exist between crystal clusters, and adjacent particle clusters interweave to form a three-dimensional interconnected hierarchical pore network, reducing interfacial impedance, improving ionic conductivity, and ensuring good cycle stability of the battery.

[0030] In some embodiments, the base membrane can be a polyolefin membrane, the specific type of which is not limited, such as PE, PP, etc. The thickness of the base membrane is 5μm to 10μm, such as 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, etc., or any value between the above adjacent values.

[0031] It should be noted that the lithium battery coated separator provided by the present invention has the following advantages: (1) Reduced air permeability: The nanorod core-shell structure constructs a uniform air permeability channel, resulting in excellent air permeability and low air permeability resistance. (2) Improved electrolyte wettability: The porous structure significantly improves the electrolyte wetting speed, and the separator has strong hydrophilicity, resulting in more thorough wetting. (3) Improved separator heat resistance: The solid core has extremely strong thermal stability, does not deform or collapse at high temperatures, the skeleton support does not fail, and the three-dimensional crystal cluster layer on the surface forms an air insulation interlayer, which significantly blocks the transverse and longitudinal heat transfer.

[0032] This invention provides a method for preparing a lithium-ion battery coated separator, comprising the following steps: S1, Surface activation Solid spherical ceramic particles are surface activated to produce hydroxyl groups and micro-etched sites on the surface, resulting in activated particles. Through activation, a large number of highly active Al–OH dangling bonds are formed on the particle surface, inducing ZnO seeds to be anchored at a high density and uniformly on the alumina surface.

[0033] Specifically, the solid spherical ceramic particles are made of at least one of Al2O3, boehmite, SiO2 and TiO2, and are commercially available raw materials. The specific particle size is as described in the instruction manual above.

[0034] In some embodiments, the step of preparing activated particles includes: treating solid spherical ceramic particles in an inorganic alkaline solution, followed by washing and drying to obtain ceramic particles with surface hydroxylation and micro-etching. The concentration of the inorganic alkaline solution is 0.5 mol / L to 3.0 mol / L, such as 0.5 mol / L, 1.0 mol / L, 1.5 mol / L, 2.0 mol / L, 2.5 mol / L, 3.0 mol / L, etc., or any value between these adjacent values. The treatment time in the inorganic alkaline solution is 20 min to 60 min, such as 20 min, 30 min, 40 min, 50 min, 60 min, etc. The inorganic alkaline solution is selected from at least one of sodium hydroxide solution and potassium hydroxide solution, and the inorganic alkaline solution can be any one or more of the above.

[0035] S2, Formation of seed layer A seed layer containing the target metal is formed on the surface of the activated particles, and the specific formation method is not limited. The target metal is selected from at least one of zinc, aluminum, and zirconium, and the target metal can be any one or more of the above.

[0036] In a preferred embodiment, the step of forming a seed layer containing the target metal on the surface of the activated particles includes: immersing the activated particles in a precursor solution containing target metal ions, followed by impregnation and drying, and then calcining to form a uniform seed layer on their surface. The precursor solution can be a solution or a sol.

[0037] Further, the preparation steps of the precursor solution include: mixing the metal salt and solvent, magnetically stirring until completely dissolved, adding the corresponding acid dropwise to adjust the pH to 3.5-6.0 (e.g., 3.5, 4.0, 4.5, 5.0, 5.5, 6.0, etc.), and continuing stirring for 30-60 minutes to obtain a precursor solution with a concentration of 0.05 mol / L-0.25 mol / L. The metal salt is selected from at least one of zinc acetate dihydrate, zinc nitrate hexahydrate, aluminum nitrate, and zirconium nitrate. The metal salt can be any one or more of these, and the solvent can be anhydrous ethanol, water, etc., with a suitable solvent selected according to the type of metal salt. Specifically, the amount of metal salt used can be 1-5 mmol, the amount of solvent can be 20-100 mL, and the concentration of the precursor solution refers to the concentration of the metal salt, which can be 0.05 mol / L, 0.10 mol / L, 0.15 mol / L, 0.20 mol / L, 0.25 mol / L, etc., or any value between the above adjacent values.

[0038] In some embodiments, the impregnation and drying steps are repeated 1 to 5 times, that is, after impregnation, drying is performed, followed by impregnation and drying again, and so on. The number of cycles is preferably 1 to 4 times. Ultrasonic impregnation is used, with each impregnation lasting 30 to 60 minutes (e.g., 30 min, 40 min, 50 min, 60 min, etc.), and centrifugation is performed after impregnation to obtain the precipitate. During the drying process, the drying temperature is controlled at 110℃ to 130℃, such as 110℃, 115℃, 120℃, 125℃, 130℃, etc., or any value between these adjacent values; the drying time is controlled at 10 min to 30 min, such as 10 min, 15 min, 20 min, 25 min, 30 min, etc., or any value between these adjacent values.

[0039] In some embodiments, after the impregnation-drying cycle is completed, the powder is calcined at 300°C to 400°C for 30 to 60 minutes. Specifically, the calcination temperature can be 300°C, 330°C, 350°C, 380°C, 400°C, etc., or any value between adjacent values; the calcination time can be 30 minutes, 40 minutes, 50 minutes, 60 minutes, etc., or any value between adjacent values.

[0040] S3, Nanorod Growth Rod-shaped crystal clusters are grown on the surface of activated particles supported by a seed layer to prepare core-shell ceramic particles. The specific method for growing the rod-shaped crystal clusters is not limited, as long as the size of the clusters meets the requirements.

[0041] In a preferred embodiment, the step of growing rod-shaped crystal clusters includes: dispersing activated particles loaded with seed crystal layers in a growth solution and performing a hydrothermal reaction to obtain a core-shell structure precursor; washing, drying, or calcining the core-shell structure precursor to remove the solvent and prepare core-shell ceramic particles. The hydrothermal reaction temperature is 80℃~220℃, such as 80℃, 100℃, 130℃, 150℃, 180℃, 200℃, 220℃, etc., preferably 90℃~95℃; the hydrothermal reaction time is 2h~48h, such as 2h, 5h, 10h, 15h, 20h, 25h, 30h, 35h, 40h, 45h, 48h, etc., preferably 4h~8h. By controlling the temperature and time of the hydrothermal reaction, the epitaxial growth of nanorods along the seed crystal can be better controlled. In actual operation, the activated particles of the seed layer are added to the growth solution and ultrasonically dispersed for 10-30 minutes. The mixture is then transferred to a PTFE-lined hydrothermal reactor (50-70% filling), sealed, and placed in an oven for reaction. The washing method after reaction is unrestricted; anhydrous ethanol and deionized water can be used.

[0042] The growth solution contains metal salts, an alkali source, and a structure-directing agent, utilizing the alkali source to slowly decompose and release OH-. - This method avoids drastic fluctuations in solution pH, ensuring uniform and stable nucleation and growth of metal oxides such as ZnO. The structure-directing agent acts as a guide, directing the growth of crystal clusters into rod-shaped clusters. The concentration of metal elements in the growth solution is 0.05 mol / L-0.25 mol / L, such as 0.05 mol / L, 0.10 mol / L, 0.15 mol / L, 0.20 mol / L, or 0.25 mol / L, which can be consistent with the concentration of the precursor solution. Specifically, the metal salt, alkali source, and structure-directing agent are weighed and dissolved in deionized water, and the solution is magnetically stirred for 30-60 minutes until completely dissolved.

[0043] Furthermore, the alkali source is selected from at least one of hexamethylenetetramine, hexamethylenetetramine, urea, and triethanolamine; the alkali source can be any one or more of these. The molar ratio of the alkali source to the metal element in the metal salt is (0.5~1.5):1, such as 0.5:1, 0.8:1, 1.0:1, 1.3:1, 1.5:1, etc., or any value between these adjacent values. By controlling the type and amount of the alkali source, the slow decomposition and release of OH- during the reaction process can be controlled. - This can avoid drastic fluctuations in the solution pH value and ensure uniform and stable nucleation and growth of metal oxides.

[0044] Furthermore, the structure-directing agent is selected from at least one of polyethyleneimine (PEI) and polyethylene glycol (PEG), and the structure-directing agent can be any one or more of the above. The ratio of the mass of the structure-directing agent to the molar amount of the metal element in the metal salt is (0.1~1.5) g : (5~25) mmol. When the molar amount of the metal element in the added metal salt is 5~25 mmol, the corresponding mass of the structure-directing agent can be 0.1 g, 0.3 g, 0.5 g, 0.8 g, 1.0 g, 1.3 g, 1.5 g, etc., or any value between the above adjacent values.

[0045] S4. Preparation of coating slurry The core-shell ceramic particles, binder polymer, and water are mixed evenly to obtain a coating slurry.

[0046] In some embodiments, the mass percentages of each component in the slurry are as follows: core-shell ceramic particles 4%~45%, such as 4%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, etc., or any value between adjacent values; binder polymer 0.5%~3%, such as 0.5%, 1.0%, 1.5%, 2.0%, 2.5%, 3.0%, etc., or any value between adjacent values; deionized water 50%~80%, such as 50%, 55%, 60%, 65%, 70%, 75%, 80%, etc.

[0047] S5. Preparation of Coated Separator The coating slurry obtained in step S4 is applied to at least one side of the base film and dried to form a coating.

[0048] In some embodiments, the coating slurry can be uniformly coated onto the base film by scraping, followed by drying at a temperature of 60°C-70°C.

[0049] This invention also provides a lithium-ion battery, including the lithium-ion battery coated separator provided in this invention, and may further include a positive electrode, a negative electrode, an electrolyte, etc. Optimization of the separator can improve the wetting effect on the electrolyte, which is beneficial for improving the ionic conductivity of the lithium-ion battery.

[0050] It should be noted that the lithium-ion battery provided in this embodiment of the invention has the following advantages by optimizing the separator structure: (1) Improved interface stability: The three-dimensional skeleton structure of nanorod core-shell ceramic can buffer the expansion and compression of the electrode, alleviate the deformation of the electrode, effectively block the micro short circuit of the positive and negative electrodes, suppress dendrite growth, and greatly improve the safety and short circuit prevention capability of the cell. (2) Low internal resistance and low interface impedance of the cell, small polarization of charge and discharge, and improved rate performance: The stacked through pores can accelerate ion conduction, improve the lithium ion migration efficiency, reduce the internal resistance of the cell, and significantly improve the fast charging and high rate discharge performance. (3) Improved capacity retention and extended cell life: High porosity has high liquid absorption and retention capacity, and the internal liquid storage of the cell is sufficient, which can alleviate the electrolyte loss during the cycle and keep the battery in stable cycle.

[0051] This invention also provides an electrical device, including the aforementioned lithium-ion battery, which is used for power supply. The specific form of the electrical device is not limited.

[0052] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0053] Example 1 This embodiment provides a lithium battery coated separator, the structure of which is an Al2O3@ZnO ceramic material, and the preparation steps are as follows: (1) Take 0.05 mol of alumina microspheres with a particle size of 0.3-1.5 μm, add them to 300 mL of anhydrous ethanol, sonicate for 30 minutes, centrifuge at 6000 r / min to separate the layers, and wash three times with deionized water to obtain the precipitate. Transfer the washed alumina to a 1 mol / L NaOH solution, stir at room temperature for 30 minutes, and then wash repeatedly with deionized water until the pH of the washing solution is neutral. Centrifuge to collect the precipitate, and vacuum dry at 60 °C for 6 hours to obtain precursor A.

[0054] (2) Dissolve 1 mmol of zinc acetate dihydrate in 20 mL of anhydrous ethanol and stir magnetically until completely dissolved. Add 1 mmol of acetic acid dropwise and continue stirring for 30 minutes to obtain a 0.05 mol / L solution B. Immerse precursor A in the above solution B and sonicate for 30 minutes. Obtain the precipitate by centrifugation and dry it in an oven at 120 °C for 10 minutes. Repeat the above impregnation-drying process 3 times. Then calcine the powder at 350 °C for 30 minutes (heating rate 5 °C / min) to obtain precursor C.

[0055] (3) Take 5 mmol of zinc nitrate hexahydrate, 5 mmol of hexamethylenetetramine and 0.1 g of polyethyleneimine (PEI), dissolve them in 100 mL of deionized water, stir magnetically for 30 minutes until completely dissolved, and obtain a solution D with an equimolar concentration (0.05 mol / L). Add about 0.5 g of precursor C to solution D, sonicate for 5 minutes, transfer to a hydrothermal reactor with a polytetrafluoroethylene liner (50-70% filling degree), seal, and place in an oven at 90-95 °C for 8 hours. Then wash with anhydrous ethanol and deionized water, and vacuum dry to obtain Al2O3@ZnO nanorod core-shell structure ceramic powder.

[0056] (4) Mix ceramic Al2O3@ZnO, binder polymer, and deionized water in a ratio of 95:5:200 to obtain a slurry; (5) The slurry is coated with 2μm coating on both sides of the PE-7μm base film, and the finished coated diaphragm is obtained after drying; The particle size and specific surface area of ​​Al2O3@ZnO ceramics were tested; the air permeability growth, thermal shrinkage, electrolyte immersion rate, contact angle with electrolyte, and battery cell performance after being prepared into a battery cell were also tested.

[0057] Example 2 The only difference from Example 1 is that the impregnation-drying cycle is repeated twice to obtain Al2O3@ZnO ceramic powder.

[0058] Example 3 The only difference from Example 1 is that the hydrothermal reaction time in step (3) is 4 hours, and Al2O3@ZnO ceramic powder is obtained.

[0059] Example 4 The only difference from Example 1 is that the hydrothermal reaction in step (3) lasts for 12 hours, resulting in Al2O3@ZnO ceramic powder.

[0060] Example 5 The only difference from Example 1 is that in step (3), the amount of PEI used is 0.3g, and Al2O3@ZnO ceramic powder is obtained.

[0061] Example 6 The only difference from Example 1 is that in step (3), the amount of PEI used is 0.6g, and Al2O3@ZnO ceramic powder is obtained.

[0062] Example 7 The only difference from Example 1 is that the central particles in step (1) are replaced with TiO2 to obtain TiO2@ZnO ceramic powder.

[0063] Example 8 The only difference from Example 1 is that in step (1), the central particles are replaced with SiO2 to obtain SiO2@ZnO ceramic powder.

[0064] Example 9 The only difference from Example 1 is that the molar ratio of zinc nitrate hexahydrate to hexamethylenetetramine in step (3) is 1.0:0.5, resulting in Al2O3@ZnO ceramic powder.

[0065] Example 10 The only difference from Example 1 is that the molar ratio of zinc nitrate hexahydrate to hexamethylenetetramine in step (3) is 1.0:1.5, resulting in Al2O3@ZnO ceramic powder.

[0066] Example 11 This embodiment provides a lithium-ion battery coated separator, the structure of which is an Al2O3@ZrO2 ceramic material, and the preparation steps are as follows: (1) Take 0.5 mmol of alumina microspheres with a particle size of 0.3-1.5 μm, add them to 300 mL of anhydrous ethanol, sonicate for 30 minutes, centrifuge at 6000 r / min to separate the layers, and wash three times with deionized water to obtain the precipitate. Transfer the washed alumina to a 1 mol / L sodium hydroxide solution, stir at room temperature for 30 minutes, and then wash repeatedly with deionized water until the pH of the washing solution is neutral. Centrifuge to collect the precipitate, and vacuum dry at 60 °C for 6 hours to obtain precursor A.

[0067] (2) Dissolve 5 mmol of zirconium nitrate pentahydrate in 20 mL of anhydrous ethanol and stir until dissolved. Add 0.5 mL of acetylacetone as a chelating agent and continue stirring for 1 hour. Slowly add deionized water to obtain transparent zirconium sol B. Immerse precursor A in the above zirconium sol B and sonicate for 30 minutes. Remove the powder and dry at 80°C for 30 minutes. Repeat the immersion-drying operation 3 times. Place the powder in a muffle furnace and calcine at 500°C for 1 hour to obtain precursor C.

[0068] (3) Dissolve 1.49 g of zirconium nitrate pentahydrate in 40 mL of deionized water and stir until dissolved. Add 0.8 g of urea and 0.15 g of polyethylene glycol and stir until completely dissolved. Adjust the pH to 2–3 with dilute nitric acid to form solution D. Add 0.5 g of precursor C to solution D and sonicate for 5 minutes. Transfer to a hydrothermal reactor and seal, with a filling degree of 50–60%, and react at 180 °C for 18 hours. After the reaction is complete, allow it to cool naturally to room temperature. Wash the product three times each with deionized water and anhydrous ethanol by centrifugation, and dry it under vacuum at 80 °C for 12 hours to obtain precursor E.

[0069] (4) The precursor E was placed in a muffle furnace and calcined at 600°C for 2 hours to obtain Al2O3@ZrO2 core-shell structured nanorod ceramic particles.

[0070] (5) The membrane preparation steps are the same as in Example 1.

[0071] Comparative Example 1 (1) Mix ceramic alumina, binder polymer and deionized water in a ratio of 95:5:200 to obtain a slurry; (2) The slurry was coated with 2μm coating on both sides of the PE-7μm base film and dried to obtain the finished coated diaphragm; The air permeability growth value, heat shrinkage, electrolyte immersion rate, contact angle with electrolyte, and battery cell performance after being fabricated into a battery cell were tested. Comparative Example 2 Replace Al2O3 with TiO2 in Comparative Example 1, and follow the same steps as in Comparative Example 1.

[0072] Comparative Example 3 Replace Al2O3 with SiO2 in Comparative Example 1, and follow the same steps as in Comparative Example 1.

[0073] Comparative Example 4 The only difference from Example 1 is that the impregnation-drying cycle is repeated once to obtain Al2O3@ZnO ceramic powder.

[0074] Comparative Example 5 The only difference from Example 1 is that the hydrothermal reaction time in step (3) is 1 hour, and Al2O3@ZnO ceramic powder is obtained.

[0075] Comparative Example 6 The only difference from Example 1 is that PEI is not used in step (3) to obtain Al2O3@ZnO ceramic powder.

[0076] Comparative Example 7 The only difference from Example 1 is that in step (3), the amount of PEI used is 2.0g, and Al2O3@ZnO ceramic powder is obtained.

[0077] Comparative Example 8 The only difference from Example 1 is that PEI is replaced with polyvinylpyrrolidone (PVP) in step (3).

[0078] Comparative Example 9 The only difference from Example 1 is that the reaction temperature in step (3) is 70°C, and Al2O3@ZnO ceramic powder is obtained.

[0079] Comparative Example 10 The only difference from Example 1 is that the alkali source in step (3) is replaced with ammonia water to obtain Al2O3@ZnO ceramic powder.

[0080] Comparative Example 11 The only difference from Example 1 is that the molar ratio of zinc nitrate hexahydrate to hexamethylenetetramine in step (3) is 1.0:0.3, resulting in Al2O3@ZnO ceramic powder.

[0081] Comparative Example 12 The only difference from Example 1 is that the molar ratio of zinc nitrate hexahydrate to hexamethylenetetramine in step (3) is 1.0:3.0, resulting in Al2O3@ZnO ceramic powder.

[0082] Test methods (1) Specific surface area test: Weigh 1g of ceramic material and put it into the test sample tube. Pre-treat at 300℃ for 3h to degas. Weigh before and after to obtain the specific mass of the core-shell ceramic. Use the static volume method to test. Take the relative pressure range of 0.05-0.35 of the isotherm to calculate the BET specific surface area.

[0083] (2) Incremental air permeability test: This is conducted using a Gurley instrument. The test process includes: cutting the material sample to be tested and placing it in the clamping device of the tester, ensuring the sample is flat and without obvious damage. The tester is set to a pressure of 1.2 ± 0.1 kPa according to the test requirements. The tester applies pressure to the sample at the set pressure. During the test time, gas molecules will pass through the pores or fiber gaps of the sample and enter the other side of the tester. The tester measures the amount of gas passing through the sample and calculates the air permeability value of the material based on the set parameters. The air permeability value is usually expressed as the amount of gas passing through a unit area per unit time, in units of s / 100cc. Finally, the air permeability value of the coated diaphragm is subtracted from the air permeability value of the base membrane for calculation, in units of s / 100cc. (3) Test of heat shrinkage performance of coated diaphragm: Take the coated diaphragm and cut a rectangular sheet with a length of 110 mm and a width of 70 mm (corresponding to the MD / TD direction of the diaphragm respectively). Use a 98 mm × 49 mm stamp to draw a 98 mm × 49 mm frame on the test sheet. Clamp the sheet with two A4 sheets of paper and put it into an oven at 130 / 150 / 180℃ for 1 hour. After cooling at room temperature, test the length M and width T of the frame on the diaphragm. The heat shrinkage values ​​of the coated diaphragm in the MD and TD directions are (98-M) / 98 and (49-T) / 49 respectively.

[0084] (4) Electrolyte wettability test of coated diaphragm: Cut the coated diaphragm into 200mm×5mm pieces, take 25μL of electrolyte (EC:PC:DEC=2:3:4, 1.2 M LiPF6), drop it onto the center of the cut diaphragm, time for 1 minute, and measure the length of the electrolyte spread. The longer the length, the better the wettability. In addition, test the contact angle between the electrolyte and the coated diaphragm: drop 2μL of electrolyte onto the surface of the coated diaphragm and measure the contact angle between the electrolyte drop and the diaphragm. The smaller the contact angle, the better the electrolyte wettability.

[0085] (5) Diaphragm storage performance test: Take a 10cm×10cm diaphragm and soak it in a lithium salt electrolyte (EC, EMC and DEC mass ratio of 3:5:2, LiPF6 1mol / L) at 70℃ for 24h. Weigh the diaphragm before and after soaking. Storage rate = mass after soaking / mass before soaking × 100%.

[0086] (6) Membrane ionic conductivity test: In an argon-filled glove box, the membrane, positive and negative electrodes, and electrolyte were assembled together to form a 2016 button battery. The AC impedance was measured using an electrochemical workstation, and the result was σ = L / (Rb×A), where σ is the ionic conductivity (S cm⁻¹). -1 L is the thickness of the diaphragm (cm); Rb is the intrinsic resistance of the diaphragm (Ω); A is the effective area (cm²). 2 ).

[0087] Table 1. Characteristics of Nanorod Core-Shell Ceramics

[0088] Table 2 Characteristics of Nanorod Core-Shell Ceramics

[0089] Table 3. Test results of various performance aspects of the coated diaphragm

[0090] As can be seen from Tables 1-3, the core-shell ceramics used in the embodiments all have parameters within the range set by the present invention, and the coated membranes all exhibit good performance. After being prepared into battery cells, the battery cells all exhibit good performance.

[0091] The core-shell ceramic-coated diaphragms obtained in Examples 1-11 all showed better performance than those in Comparative Examples 1-3. The data indicate that the introduction of nanorod core-shell ceramic structures can effectively improve diaphragm performance.

[0092] In Examples 1 and 2, the number of seed crystals and the coverage rate were controlled by adjusting the number of resting-drying cycles in step (2) to regulate the final shell nanorod coverage rate. The more cycles, the higher the coverage rate. A moderate coverage rate can make the coating layer form a continuous three-dimensional network channel, which promotes the uniform transport of lithium ions. However, in Comparative Example 4, due to the low coverage rate, the ion transport is uneven. The uneven capillary network results in a larger electrolyte contact angle than in Examples 1 and 2. Therefore, the coverage rate of the nanorod clusters should be controlled within the range of 80-95%.

[0093] Examples 1, 3, and 4 controlled the length and diameter of the shell nanorods by adjusting the hydrothermal reaction time. A longer reaction time resulted in longer nanorod diameters and lengths. Compared to Comparative Example 5, Examples 1, 3, and 4 exhibited higher specific surface area, aspect ratio, and richer pore structure, leading to better electrolyte spreading ability and higher ionic conductivity. However, excessively long nanorods are prone to breakage and debris generation, and the long rods can become entangled, resulting in agglomeration points and uneven coating thickness. Therefore, it is advisable to control the hydrothermal reaction time to 4-8 hours.

[0094] Examples 1, 5, and 6 control the aspect ratio during nanorod growth by adjusting the PEI concentration. PEI can inhibit the radial growth of nanorods. In Comparative Example 6, the absence of PEI leads to isotropic growth of nanorods, resulting in a small aspect ratio and a granular appearance, affecting the coating porosity and membrane performance. In Comparative Example 7, excessive PEI results in an extremely high aspect ratio, with a slight decrease in mechanical properties affecting thermal shrinkage performance. Therefore, the PEI dosage needs to be adjusted according to Examples 1, 5, and 6 to control the aspect ratio within the range of 8:1-18:1. In Comparative Example 8, the PVP adsorption on different ZnO crystal planes shows little difference, resulting in short and thick nanorods. Therefore, suitable directing agents such as PEI need to be selected for material synthesis.

[0095] Examples 1, 9, and 10 regulate the growth process of nanorods by adjusting the ratio of metal ions to alkali source. Increasing the amount of alkali source can increase the growth of shell nanorods to a certain extent. Comparative examples 11 and 12 show that too low an amount of alkali source is not conducive to nanorod growth, while too high an alkali source content leads to OH... - Increased concentration inhibits the axial preferential growth of nanorods, leading to excessively high aspect ratios and affecting the performance of the coated membrane. In Comparative Example 10, the lack of slow alkali release from ammonia water resulted in uneven nanorod growth and short aspect ratios, affecting the porosity of the material and the wettability of the membrane. Therefore, it is necessary to control the amount and use of the alkali source.

[0096] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A lithium battery coated separator, characterized in that, The coating includes a base film and a coating on at least one side of the base film; the coating contains core-shell ceramic particles and a binder polymer, wherein the core-shell ceramic particles include ceramic microspheres and radially growing crystal clusters on the surface of the ceramic microspheres, and the aspect ratio of the crystal clusters is 5:1 to 22:

1.

2. The lithium battery coated separator according to claim 1, characterized in that, By mass fraction, the coating contains 94% to 99% core-shell ceramic particles and 1% to 6% binder polymer; Preferably, the thickness of the coating is 1 μm to 5 μm; Preferably, the ceramic microspheres are made of at least one selected from Al2O3, boehmite, SiO2, and TiO2; the metal element contained in the crystal cluster is selected from at least one selected from zinc, aluminum, and zirconium. Preferably, the crystal cluster is rod-shaped; Preferably, the ceramic microspheres have a diameter of 0.3μm to 1.5μm, a surface crystal cluster length of 20nm to 500nm, a surface crystal cluster diameter of 20nm to 150nm, a crystal cluster coverage of 80% to 95%, and a crystal cluster aspect ratio of 8:1 to 18:

1. Preferably, the core-shell ceramic particles have a particle size D50 of 0.6 μm to 3.5 μm, a D90 of ≤ 5.2 μm, and a particle size distribution Span of ≤ 0.95; Preferably, the specific surface area of ​​the core-shell ceramic particles is 25 m². 2 / g~68m 2 / g, with a pore size of 80nm~220nm and a porosity of 58%~72%; Preferably, the electrolyte contact angle of the core-shell ceramic particles is ≤20°.

3. The lithium battery coated separator according to claim 1, characterized in that, The base membrane is a polyolefin separator; Preferably, the base film is selected from at least one of PE and PP; Preferably, the thickness of the base film is 5μm to 10μm.

4. A method for preparing a lithium-ion battery coated separator according to any one of claims 1-3, characterized in that, include: Surface activation treatment is performed on solid spherical ceramic particles to introduce hydroxyl groups and etching sites on the surface, resulting in activated particles. A seed layer containing the target metal is formed on the surface of the activated particles, and then crystal clusters are grown to prepare core-shell ceramic particles; the target metal is selected from at least one of zinc, aluminum and zirconium. A coating slurry is prepared using the core-shell ceramic particles, and a coating is formed on at least one side of the base film.

5. The preparation method according to claim 4, characterized in that, The steps for preparing the activated particles include: treating the solid ceramic spheres in an inorganic alkaline solution, followed by washing and drying; Preferably, the concentration of the inorganic alkali solution is 0.5 mol / L to 3.0 mol / L, and the treatment time is 20 min to 60 min; Preferably, the inorganic alkaline solution is selected from at least one of sodium hydroxide solution and potassium hydroxide solution.

6. The preparation method according to claim 4, characterized in that, The step of forming a seed layer containing the target metal on the surface of the activated particles includes: immersing the activated particles in a precursor solution containing the target metal ions, and then calcining them after impregnation and drying. Preferably, the precursor solution is a solution or a sol, and the preparation steps of the precursor solution include: mixing and dissolving a metal salt and a solvent, adding the acid corresponding to the metal salt dropwise, adjusting the pH to 3.5-6.0, and continuing to stir for 30-60 minutes to obtain a precursor solution with a concentration of 0.05 mol / L-0.25 mol / L; the metal salt is selected from at least one of zinc acetate dihydrate, zinc nitrate hexahydrate, aluminum nitrate, and zirconium nitrate. Preferably, the soaking and drying steps are repeated 1 to 5 times; Preferably, ultrasonic impregnation is used, with each impregnation lasting 30 to 60 minutes, followed by centrifugation to obtain the precipitate. Preferably, during the drying process after impregnation, the drying temperature is controlled at 110℃~130℃ and the drying time is 10min~30min; Preferably, the calcination temperature is 300℃~400℃ and the calcination time is 30min~60min.

7. The preparation method according to claim 4, characterized in that, The steps for growing crystal clusters include: dispersing activated particles loaded with seed crystal layers in a growth solution and carrying out a hydrothermal reaction to obtain a core-shell structure precursor; washing, drying or calcining the core-shell structure precursor to prepare core-shell ceramic particles; wherein the growth solution contains metal salts, alkali sources and structure directing agents. Preferably, the hydrothermal reaction temperature is 80℃~220℃ and the hydrothermal reaction time is 2h~48h; more preferably, the hydrothermal reaction temperature is 90℃~95℃ and the hydrothermal reaction time is 4h~8h. Preferably, the concentration of the metal element in the growth solution is 0.05 mol / L to 0.25 mol / L; Preferably, the alkali source is selected from at least one of hexamethylenetetramine, hexamethylenetetramine, urea, and triethanolamine; the molar ratio of the amount of the alkali source to the metal element in the metal salt is (0.5~1.5):1; Preferably, the structure-directing agent is selected from at least one of polyethyleneimine and polyethylene glycol; the ratio of the mass of the structure-directing agent to the molar amount of the metal element in the metal salt is (0.1~1.5) g: (5~25) mmol.

8. The preparation method according to claim 4, characterized in that, The preparation steps of the coating slurry include: mixing core-shell ceramic particles, binder polymer and water, wherein the mass percentages of each component in the slurry are as follows: core-shell ceramic particles 4%~45%, binder polymer 0.5%~3%, and deionized water 50%~80%; Preferably, the coating slurry is applied to the base film by scraping and then dried.

9. A lithium-ion battery, characterized in that, The lithium-ion battery coated separator as described in any one of claims 1-3 or the lithium-ion battery coated separator prepared by the preparation method described in any one of claims 4-8.

10. An electrical appliance, characterized in that, Including the lithium-ion battery as described in claim 9.

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