Battery monomer and preparation method thereof, battery and power utilization device

Abstract

The invention discloses a battery monomer, a preparation method thereof, a battery and an electric device. The battery monomer comprises a positive pole piece and a negative pole piece, and at least one of the positive pole piece and the negative pole piece comprises a current collector, an active material layer, a first porous layer and a second porous layer; the active material layer is at least positioned on one side surface of the current collector; the first porous layer covers the active material layer and comprises a first insulating material; the second porous layer covers the first porous layer, the second porous layer comprises a second insulating material, and the porosity of the second porous layer is larger than that of the first porous layer. The first porous layer and the second porous layer protect the active material layer, so that the probability of direct contact between the active material of the positive pole piece and the active material of the negative pole piece is reduced, dual internal short circuit protection is realized, and the stability of the battery is improved.

Description

Technical Field

[0001] This application relates to the field of battery technology, and in particular to battery cells and their preparation methods, batteries, and electrical devices. Background Technology

[0002] Currently, a typical battery structure includes a positive electrode, a negative electrode, and a separator. The separator separates the positive and negative electrodes, reducing the probability of internal short circuits caused by contact between them. The separator also prevents electrons from freely passing through the battery, while allowing ions in the electrolyte to freely pass between the positive and negative electrodes. However, separators have poor stability and pose a risk of internal short circuits. Summary of the Invention

[0003] This application provides a battery cell and its preparation method, a battery, and an electrical device, forming a separator-free battery structure.

[0004] To address the aforementioned technical problems, the first aspect of this application provides a battery cell, including a positive electrode and a negative electrode; at least one of the positive and negative electrode includes a current collector, an active material layer, a first porous layer, and a second porous layer; the active material layer is located on at least one side of the current collector; the first porous layer covers the active material layer and includes a first insulating material; the second porous layer covers the first porous layer and includes a second insulating material, and the porosity of the second porous layer is greater than that of the first porous layer.

[0005] The first porous layer, covering the active material layer, separates the active material layer of one electrode from the other, reducing the probability of direct contact between the active materials of the positive and negative electrodes. Furthermore, a second porous layer, covering the first porous layer, provides secondary protection for the active material layer, further reducing the probability of direct contact between the active materials of the positive and negative electrodes, achieving dual internal short-circuit protection and improving battery stability. Additionally, the porosity of the second porous layer is greater than that of the first porous layer. While achieving dual internal short-circuit protection, it maintains the smoothness of the ion channels formed by the cooperation of the first and second porous layers, preserving the rate at which ions pass through both layers, thus improving battery performance.

[0006] In one embodiment, the first insulating material includes at least one of a metal oxide and an inorganic non-metal oxide. Metal oxides and inorganic non-metal oxides are inorganic materials, possessing good high-temperature resistance and flame retardancy, which helps improve battery stability.

[0007] In one embodiment, the first insulating material includes at least one of alumina, zirconium oxide, titanium oxide, magnesium oxide, and silicon oxide. These metal oxides and / or inorganic non-metal oxide materials have good hydrophilicity and good electrolyte absorption capacity, which facilitates ion transport and maintains the uniformity of current distribution within the battery during charging and discharging. Simultaneously, the film layer formed by these metal oxides and / or inorganic non-metal oxide materials has high strength, reducing the probability of the first porous layer rupture, thereby reducing the short-circuit rate and improving battery stability.

[0008] In one embodiment, the thickness of the first porous layer is 100 nm to 1000 nm. This provides good protection for the active material layer, maintains the patency of ion channels, and keeps the electrode resistance appropriate, which is beneficial for maintaining a high energy density in the battery.

[0009] In one embodiment, the thickness of the first porous layer is 150 nm to 250 nm. Ions in the electrolyte can easily pass through the first porous layer, resulting in a electrode with low resistance.

[0010] In one embodiment, the first porous layer is a porous layer in which a first insulating material is continuously distributed. The film layer is relatively dense, and the continuous distribution of the first insulating material maintains the consistency of the protective effect throughout the active material layer.

[0011] In one embodiment, the second insulating material includes at least one of metal oxides, inorganic non-metal oxides, and hydroxides of metal oxides. Metal oxides, inorganic non-metal oxides, and hydroxides of metal oxides are inorganic materials, possessing good high-temperature resistance and flame retardancy, which is beneficial for improving battery stability.

[0012] In one embodiment, the second insulating material includes at least one of alumina, zirconium oxide, titanium oxide, magnesium oxide, silicon oxide, and boehmite. The aforementioned metal oxides, inorganic non-metal oxides, and metal oxide hydroxides possess good hydrophilicity and excellent electrolyte absorption capacity, facilitating ion transport and maintaining the uniformity of current distribution within the battery during charging and discharging. Simultaneously, the film formed by the aforementioned metal oxides and / or inorganic non-metal oxides and / or metal oxide hydroxides exhibits high strength, reducing the probability of rupture in the second porous layer, thereby lowering the short-circuit rate and improving battery stability.

[0013] In one embodiment, the second porous layer further includes an adhesive and a dispersant; the second insulating material accounts for 90% to 98% of the total mass of the second insulating material, adhesive, and dispersant, the adhesive accounts for 1% to 9% of the total mass of the second insulating material, adhesive, and dispersant, and the dispersant accounts for 0.1% to 1% of the total mass of the second insulating material, adhesive, and dispersant. Since the second insulating material is an inorganic material, the addition of the adhesive allows the second insulating material to adhere to the first porous layer; the addition of the dispersant allows the second insulating material to be evenly distributed in the slurry, thereby making the distribution of the second insulating material in the formed second porous layer more uniform and maintaining the consistency of the protective effect throughout the active material layer.

[0014] In one embodiment, the adhesive includes at least one selected from acrylic polymers, polyvinylidene fluoride polymers, and styrene-butadiene rubber polymers; and / or, the dispersant includes at least one selected from calcium hydroxide, carboxymethyl cellulose, and polyvinyl alcohol. The selection of the above-mentioned materials for the adhesive maintains strong adhesion between the second insulating material and the first porous layer, thus maintaining the protective effect on the active material layer. The selection of the above-mentioned materials for the dispersant provides good dispersion of the second insulating material in the slurry, maintaining the uniformity of the distribution of the second insulating material, and thereby maintaining the consistency of the protective effect on all parts of the active material layer.

[0015] In one embodiment, the thickness of the second porous layer is 1 μm to 4 μm. This provides good coverage of the first porous layer, maintains good protection for the active material layer, preserves the patency of ion channels, and keeps the electrode resistance appropriate, which is beneficial for maintaining a high energy density in the battery.

[0016] In one embodiment, the thickness of the second porous layer is 1 μm to 2 μm. Ions in the electrolyte can easily pass through the second porous layer, the electrode has low resistance, and the battery thickness formed by the electrode is less than that of existing batteries with separators.

[0017] In one embodiment, the second porous layer is a porous layer in which the particles of the second insulating material are spaced apart, which achieves a good protective effect while maintaining the unobstructed ion channels.

[0018] To address the aforementioned technical problems, a second aspect of this application provides a method for preparing a battery cell as described in any of the preceding claims, comprising: providing a current collector; disposing of an active material layer, the active material layer being located at least on one side of the current collector; disposing of a first porous layer, the first porous layer covering the active material layer, the first porous layer comprising a first insulating material; and disposing of a second porous layer, the second porous layer covering the first porous layer, the second porous layer comprising a second insulating material, the porosity of the second porous layer being greater than the porosity of the first porous layer. This method for preparing a battery cell possesses at least the same advantages as the method for preparing a battery cell.

[0019] In one embodiment, a first porous layer is formed by a vapor deposition process; a second porous layer is formed by coating a slurry comprising a second insulating material. The first porous layer formed by the vapor deposition process has a relatively dense film, i.e., small pores; the second porous layer formed by the coating process has larger pores, achieving a porosity greater than that of the first porous layer, thus maintaining the smoothness of the ion channels formed by the combination of the first and second porous layers.

[0020] In one embodiment, the slurry further includes a solvent, an adhesive, and a dispersant; the solid content of the slurry is 6%–10%; the second insulating material accounts for 90%–98% of the total mass of the second insulating material, adhesive, and dispersant, the adhesive accounts for 1%–9% of the total mass of the second insulating material, adhesive, and dispersant, and the dispersant accounts for 0.1%–1% of the total mass of the second insulating material, adhesive, and dispersant; the viscosity of the slurry is 50 mPa·s–1000 mPa·s. By designing the above-mentioned proportions of the second insulating material, adhesive, and dispersant, the solid content of the slurry, and the viscosity of the slurry, the thickness of the second porous layer formed by coating is appropriate, achieving a protective effect while maintaining the smooth passage of electrolyte ions.

[0021] To address the aforementioned technical problems, a third aspect of this application provides a battery comprising a battery cell according to any of the above-mentioned methods or a battery cell prepared by a method for preparing a battery cell according to any of the above-mentioned methods. The battery possesses at least the same advantages as the battery cell.

[0022] To address the aforementioned technical problems, a fourth aspect of this application provides an electrical device including the aforementioned battery. The electrical device possesses at least the same advantages as a single battery cell.

[0023] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 This is an exploded structural diagram of a battery cell provided in an embodiment of this application;

[0026] Figure 2 This is a schematic diagram of the structure of the electrode provided in the embodiments of this application;

[0027] Figure 3a This is a SEM image of the first porous layer provided in the embodiments of this application;

[0028] Figure 3b yes Figure 3a The cross-sectional SEM image of the first porous layer is shown below.

[0029] Figure 4 This is a SEM image of the second porous layer provided in the embodiments of this application;

[0030] Figure 5 This is a schematic flowchart of the method for preparing a single battery cell provided in the embodiments of this application;

[0031] Figure 6 yes Figure 5 The diagram shows the structural flow of the method.

[0032] Figure 7 This is an exploded view of the battery provided in an embodiment of this application;

[0033] Figure 8 This is a schematic diagram of the vehicle structure provided in an embodiment of this application. Detailed Implementation

[0034] To make the objectives, technical solutions, and effects of this application clearer and more explicit, the embodiments of the technical solutions of this application will be described in detail below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solutions of this application, and are therefore merely examples, and should not be used to limit the scope of protection of this application.

[0035] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0036] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, the term "multiple" refers to two or more (including two), similarly, "multiple sets" refers to two or more (including two sets), and "multiple pieces" refers to two or more (including two pieces), unless otherwise explicitly specified.

[0037] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0038] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0039] Quantities, ratios, and other numerical values ​​are presented in range format in this document. It should be understood that this range format is for convenience and brevity and should be interpreted flexibly to include not only numerical values ​​explicitly specified as range limits, but also all individual numerical values ​​or subranges covered within the range, as if each numerical value and subrange were explicitly specified.

[0040] Unless otherwise specified, all steps of this application may be performed sequentially, randomly, or in parallel, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or steps (b) and (a) performed sequentially, or steps (a) and (b) may be performed simultaneously in parallel. For example, the method may also include step (c), indicating that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or steps (a), (c), and (b), or steps (c), (a), and (b), etc.

[0041] The separator is a key component of a battery, directly affecting its stability. Its main function is to separate the positive and negative electrodes, preventing electrons from freely passing through while allowing ions in the electrolyte to freely pass between them.

[0042] Currently, a commonly used separator is the polyolefin separator. Polyolefin separators have poor thermal properties and are prone to thermal shrinkage at high temperatures, resulting in some areas between the positive and negative electrodes not being separated by the separator, posing a risk of internal short circuits. One existing solution to the poor thermal stability of polyolefin separators is to coat the surface with a heat-resistant coating. However, due to the complex interfaces between the separator and the positive and negative electrodes, coating the polyolefin separator with a heat-resistant coating increases the overall thickness of the separator. A thicker separator results in greater internal resistance in the battery, leading to a decrease in the battery's electrical performance.

[0043] In addition, during battery assembly, the soft separator may become wrinkled or lack strength, resulting in some areas between the positive and negative electrodes not being separated by the separator, which can lead to internal short circuits.

[0044] In view of the poor battery stability caused by the thermal stability and assembly problems of the separator, this application provides a battery cell and its preparation method, battery, and power device, which processes the electrode sheets to eliminate the separator and form a separatorless battery structure.

[0045] Please see Figure 1 , Figure 1 This is an exploded structural diagram of a battery cell provided in an embodiment of this application.

[0046] Battery cell 20 refers to the smallest unit that makes up battery 100. For example... Figure 1 The battery cell 20 includes an end cap 21, a housing 22, a cell assembly 23, and other functional components.

[0047] End cap 21 refers to a component that covers the opening of housing 22 to isolate the internal environment of battery cell 20 from the external environment. The shape of end cap 21 can be adapted to the shape of housing 22 to fit it. Optionally, end cap 21 can be made of a material with certain hardness and strength (such as aluminum alloy), so that end cap 21 is not easily deformed under pressure and impact, allowing battery cell 20 to have higher structural strength and improved stability. Functional components such as electrode terminals 21a can be provided on end cap 21. Electrode terminals 21a can be used for electrical connection with cell assembly 23 to output or input electrical energy from battery cell 20. In some embodiments, end cap 21 can also be provided with a pressure relief mechanism for releasing internal pressure when the internal pressure or temperature of battery cell 20 reaches a threshold. The material of end cap 21 can also be various, such as copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc., and this application embodiment does not impose any special limitations on this. In some embodiments, an insulating element may be provided on the inner side of the end cap 21. The insulating element can be used to isolate the electrical connection components within the housing 22 from the end cap 21 to reduce the risk of short circuits. For example, the insulating element may be made of plastic, rubber, etc.

[0048] The housing 22 is a component used to cooperate with the end cap 21 to form the internal environment of the battery cell 20. This internal environment can accommodate the cell assembly 23, electrolyte, and other components. The housing 22 and the end cap 21 can be independent components. An opening can be provided on the housing 22, and the end cap 21 can be used to close the opening to form the internal environment of the battery cell 20. Alternatively, the end cap 21 and the housing 22 can be integrated. Specifically, the end cap 21 and the housing 22 can form a common connecting surface before other components are inserted into the housing. When it is necessary to encapsulate the interior of the housing 22, the end cap 21 closes the housing 22. The housing 22 can be of various shapes and sizes, such as cuboid, cylindrical, hexagonal prism, etc. Specifically, the shape of the housing 22 can be determined according to the specific shape and size of the cell assembly 23. The material of the housing 22 can be various, such as copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc. This application embodiment does not impose any special limitations on this.

[0049] The cell assembly 23 is the component in the battery cell 100 where the electrochemical reaction occurs. The casing 22 may contain one or more cell assemblies 23. The cell assembly 23 is mainly formed by winding or stacking positive and negative electrode sheets; wherein at least one of the positive and negative electrode sheets is the electrode sheet 40 described in the above embodiments or an electrode sheet prepared by the electrode sheet preparation method provided in the above embodiments. The portions of the positive and negative electrode sheets containing active material constitute the main body of the cell assembly, while the portions of the positive and negative electrode sheets without active material each constitute a tab 23a. The positive and negative tabs may be located together at one end of the main body or separately at both ends of the main body. During the charging and discharging process of the battery, the positive and negative active materials react with the electrolyte, and the tabs 23a connect to the electrode terminals to form a current loop.

[0050] Please see Figure 2 , Figure 2 This is a schematic diagram of the structure of the electrode provided in the embodiment of this application.

[0051] The battery cell assembly 23 of the battery cell 20 provided in this application embodiment includes a positive electrode and a negative electrode, at least one of which is an electrode 40. The electrode 40 includes a current collector 41, an active material layer 42, a first porous layer 43, and a second porous layer 44. The active material layer 42 is located on at least one side of the current collector 41. The first porous layer 43 covers the active material layer 42 and includes a first insulating material. The second porous layer 44 covers the first porous layer 43 and includes a second insulating material. The porosity of the second porous layer 44 is greater than that of the first porous layer 43.

[0052] The current collector 41 is a structural component that collects current. In a lithium-ion battery, the current collector 41 is primarily a metal foil. For example, when the electrode 40 is a positive electrode, the current collector 41 is an aluminum foil. For example, when the electrode 40 is a negative electrode, the current collector 41 is a copper foil.

[0053] The active material layer 42 includes an active material. For example, when the electrode 40 is a positive electrode, the active material layer 42 includes a positive active material, which can be a ternary material, lithium iron phosphate, etc., and the design is tailored to specific needs. For example, when the electrode 40 is a negative electrode, the active material layer 42 includes a negative active material, which can be a carbon-based material, silicon-based material, etc., and the design is tailored to specific needs.

[0054] The first porous layer 43 includes a first insulating material, and the second porous layer 44 includes a second insulating material. The first porous layer 43 and the second porous layer 44 prevent electrons from passing through to the active material layer 42. The first porous layer 43 is a membrane layer with multiple first pores, and the second porous layer 44 is also a membrane layer with multiple second pores. The size of both the first and second pores allows ions in the electrolyte to pass through freely. In other words, the first porous layer 43 and the second porous layer 44 achieve the function of allowing ions in the electrolyte to pass through freely while blocking electrons.

[0055] The first porous layer 43 is disposed over the active material layer 42, which can separate the active material layer 42 of the electrode 40 from the other electrode, thereby reducing the probability of direct contact between the active materials of the positive electrode and the active materials of the negative electrode. It should be noted that the other electrode mentioned above can be the electrode 40 provided in the embodiments of this application, or it can be an electrode of the prior art. Furthermore, the second porous layer 44 is disposed over the first porous layer 43, providing secondary protection for the active material layer 42, further reducing the probability of direct contact between the active materials of the positive electrode and the active materials of the negative electrode, realizing dual internal short-circuit protection, which is beneficial to improving the stability of the battery.

[0056] In addition, the porosity of the second porous layer 44 is greater than that of the first porous layer 43. While achieving dual internal short-circuit protection, it maintains the smoothness of the ion channel formed by the cooperation of the first porous layer 43 and the second porous layer 44, and maintains the rate at which ions pass through the first porous layer 43 and the second porous layer 44, which is beneficial to improving the performance of the battery.

[0057] Using the electrode 40 provided in this embodiment to prepare a battery cell, the protective function of the first porous layer 43 and the second porous layer 44 eliminates the need for a separator. The first porous layer 43 and the second porous layer 44 form an integral structure with the active material layer 42, eliminating the need for assembly between them. This solves the internal short-circuit problem caused by separator assembly issues, thereby improving battery stability.

[0058] In one embodiment, the current collector 41 is provided with active material layers 42 on opposite sides, and the active material layers 42 on opposite sides of the current collector 41 are respectively covered with a first porous layer 43 and a second porous layer 44, so that when the electrode 40 is formed into a battery by winding or stacking, the separator can be omitted, and the active material of the positive electrode and the active material of the negative electrode can be connected.

[0059] In one embodiment, an active material layer 42 is disposed on one side of the current collector 41, a first porous layer 43 encapsulates the current collector 41 and the active material layer 42, and a second porous layer 44 encapsulates the first porous layer 43. The second porous layer 44 located on the side of the current collector 41 facing the active material layer 42 is used to contact the electrolyte in the battery, or the second porous layer 44 is entirely used to contact the electrolyte.

[0060] In one embodiment, at least a portion of the current collector 41 may be provided with an active material layer 42, at least a portion of the active material layer 42 may be provided with a first porous layer 43, at least a portion of the first porous layer 43 may be provided with a second porous layer 44, and the second porous layer 44 is used to contact the electrolyte in the battery.

[0061] In one embodiment, the first insulating material includes at least one of a metal oxide and an inorganic non-metal oxide. Metal oxides and inorganic non-metal oxides are inorganic materials, possessing good high-temperature resistance and flame retardancy, which helps improve battery stability.

[0062] In one embodiment, the first insulating material includes at least one of aluminum oxide, zirconium oxide, titanium oxide, magnesium oxide, and silicon oxide. These metal oxides and / or inorganic non-metal oxide materials have good hydrophilicity and good electrolyte absorption capacity, which facilitates ion transport and maintains the uniformity of current distribution within the battery during charging and discharging. Simultaneously, the film layer formed by these metal oxides and / or inorganic non-metal oxide materials has high strength, reducing the probability of the first porous layer 43 rupturing, thereby reducing the short-circuit rate and improving battery stability.

[0063] In one embodiment, the thickness of the first porous layer 43 is 100nm to 1000nm, which provides good protection for the active material layer 42, maintains the patency of ion channels, and keeps the resistance of the electrode 40 appropriate, thus helping to maintain a high energy density in the battery. It can be understood that the thickness of the first porous layer 43 can be 100nm, 150nm, 200nm, 250nm, 300nm, 350nm, 400nm, 450nm, 500nm, 550nm, 600nm, 650nm, 700nm, 750nm, 800nm, 850nm, 900nm, 950nm, 1000nm, etc., or it can be a range of any two of these values, such as 100nm to 200nm, 300nm to 500nm, 250nm to 750nm, 800nm ​​to 900nm, 600nm to 1000nm, etc.

[0064] In one embodiment, the thickness of the first porous layer 43 is 150 nm to 250 nm, allowing ions in the electrolyte to easily pass through the first porous layer 43 to the active material layer 42, resulting in a lower resistance for the electrode 40. It is understood that the thickness of the first porous layer 43 can be 150 nm, 170 nm, 190 nm, 210 nm, 230 nm, 250 nm, etc., or a range consisting of any two of these values, such as 150 nm to 230 nm, 170 nm to 250 nm, 190 nm to 230 nm, etc.

[0065] In one embodiment, the first porous layer 43 is a continuously distributed porous layer of the first insulating material. It should be noted that the first porous layer 43 is formed using a vapor deposition process, such as vacuum evaporation, magnetron sputtering, or atomic layer deposition. Vapor deposition is a method that, under vacuum conditions, vaporizes materials into atoms or molecules or ionizes them into ions and directly deposits them onto the substrate surface. The first porous layer 43 formed by vapor deposition has a thinner thickness and smaller pores, and the first insulating material is continuously distributed, resulting in better coverage of the active material layer 42. For example, as... Figure 3a and Figure 3b As shown, Figure 3a This is a SEM image of the first porous layer provided in the embodiments of this application. Figure 3b yes Figure 3a The cross-sectional SEM image of the first porous layer shown is shown below. Figure 3a and Figure 3b The first porous layer 43 is made of aluminum oxide and is formed by vacuum evaporation PVD process, resulting in a morphology with a thickness of 148nm to 171nm. The film is relatively dense, and the first insulating material is continuously distributed, maintaining the consistency of the protective effect of the active material layer 42.

[0066] In one embodiment, the second insulating material includes at least one of metal oxides, inorganic non-metal oxides, and hydroxides of metal oxides. Metal oxides, inorganic non-metal oxides, and hydroxides of metal oxides are inorganic materials, possessing good high-temperature resistance and flame retardancy, which is beneficial for improving battery stability.

[0067] In one embodiment, the second insulating material includes at least one of alumina, zirconium oxide, titanium oxide, magnesium oxide, silicon oxide, and boehmite. The aforementioned metal oxides, inorganic non-metal oxides, and hydroxides of metal oxides possess good hydrophilicity and excellent electrolyte absorption capacity, facilitating ion transport and maintaining the uniformity of current distribution within the battery during charging and discharging. Simultaneously, the film formed by the aforementioned metal oxides and / or inorganic non-metal oxides and / or hydroxides of metal oxides exhibits high strength, reducing the probability of rupture in the second porous layer 44 and protecting the first porous layer 43, thereby reducing the battery's short-circuit rate and improving battery stability.

[0068] In one embodiment, the second porous layer 44 further includes an adhesive and a dispersant; the second insulating material accounts for 90% to 98% of the total mass percentage of the second insulating material, adhesive, and dispersant, the adhesive accounts for 1% to 9% of the total mass percentage of the second insulating material, adhesive, and dispersant, and the dispersant accounts for 0.1% to 1% of the total mass percentage of the second insulating material, adhesive, and dispersant. It is understood that the mass percentage of the second insulating material in the total mass percentage of the second insulating material, adhesive, and dispersant can be 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, etc., or it can be a range consisting of any two of these values, for example, 90% to 93%, 93% to 95%, 95% to 98%, etc. The mass percentage of the adhesive in the sum of the second insulating material, adhesive, and dispersant can be 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, etc., or a range consisting of any two of these values, such as 1%–5%, 1%–7%, 2%–7%, 2%–9%, ​​etc. The mass percentage of the dispersant in the sum of the second insulating material, adhesive, and dispersant can be 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, etc., or a range consisting of any two of these values, such as 0.1%–0.7%, 0.2%–0.6%, 0.4%–1%, 0.6%–0.9%, etc.

[0069] The second porous layer 44 can be formed by coating a slurry. Since the second insulating material is inorganic, an adhesive is added to allow it to adhere to the first porous layer 43; a dispersant is added to ensure the second insulating material is evenly distributed in the slurry, resulting in a more uniform distribution of the second insulating material in the formed second porous layer 44, maintaining the consistency of the protective effect throughout the active material layer 42. By designing the above-mentioned ratio between the second insulating material, adhesive, and dispersant, the slurry viscosity is suitable, and the thickness of the second porous layer 44 formed is appropriate, achieving a protective effect while maintaining the smooth passage of electrolyte ions.

[0070] In one embodiment, the adhesive includes at least one selected from acrylic polymers, polyvinylidene fluoride polymers, and styrene-butadiene rubber polymers; and / or, the dispersant includes at least one selected from calcium hydroxide, carboxymethyl cellulose, and polyvinyl alcohol. The selection of the above-mentioned materials for the adhesive maintains strong adhesion between the second insulating material and the first porous layer 43, thus maintaining the protective effect on the active material layer 42. The selection of the above-mentioned materials for the dispersant provides good dispersion of the second insulating material in the slurry, maintaining the uniformity of the distribution of the second insulating material, and thereby maintaining the consistency of the protective effect on all parts of the active material layer 42.

[0071] In one embodiment, the thickness of the second porous layer 44 is 1 μm to 4 μm. This provides good coverage of the first porous layer 43, maintains good protection of the active material layer 42, preserves the ion channel's patency, and simultaneously maintains appropriate resistance of the electrode 40, thus contributing to a high energy density in the battery. Furthermore, by designing the thickness of the second porous layer 44 as described above, the battery thickness formed using the electrode 40 is at most the same as that of a conventional battery with a separator. It is understood that the thickness of the second porous layer 44 can be 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, etc., or a range consisting of any two of these values, such as 1 μm to 3 μm, 1.5 μm to 3.5 μm, 2 μm to 4 μm, 1 μm to 3.5 μm, etc.

[0072] In one embodiment, the thickness of the second porous layer 44 is 1 μm to 2 μm. Ions in the electrolyte can easily pass through the second porous layer 44, the electrode 40 has a low resistance, and the battery thickness formed by the electrode 40 is less than that of existing batteries with separators. It is understood that the thickness of the second porous layer 44 can be 1 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.7 μm, 1.8 μm, 1.9 μm, 2 μm, etc., or a range consisting of any two of these values, for example, 1 μm to 1.5 μm, 1.3 μm to 1.8 μm, 1.6 μm to 2 μm, 1.2 μm to 2 μm, etc.

[0073] In one embodiment, the second porous layer 44 is a porous layer in which the particles of the second insulating material are spaced apart. It should be noted that, compared to the first porous layer 43 formed by vapor deposition, the second porous layer 44 formed by coating a slurry has a thicker layer, larger pores, and the particles of the second insulating material are spaced apart. For example, as shown... Figure 4 As shown, Figure 4 This is a SEM image of the second porous layer provided in the embodiments of this application. Specifically, Figure 4 The second porous layer 44 is made of aluminum oxide and is coated to form a morphology with a thickness of 1 to 2 μm. The second insulating material particles are spaced apart to achieve a good protective effect while maintaining the unobstructed ion channels.

[0074] Optionally, the particle size range of the second insulating material is 1 to 2 μm, so that the second insulating material can be distributed relatively evenly in the slurry, and the gap between the material particles of the second porous layer 44 formed by coating is appropriate, which is conducive to maintaining the smooth passage of electrolyte ions.

[0075] In one specific embodiment, the electrode 40 includes a current collector 41, an active material layer 42, a first porous layer 43, and a second porous layer 44. The active material layer 42 is respectively disposed on opposite sides of the current collector 41, and the active material layers 42 on opposite sides of the current collector 41 are respectively covered by the first porous layer 43 and the second porous layer 44. The first porous layer 43 is formed using a vacuum vapor deposition (PVD) process; the first porous layer 43 includes alumina. The second porous layer 44 is formed using a coating slurry, the slurry including alumina.

[0076] Please see Figure 5 and Figure 6 , Figure 5 This is a schematic flowchart of the method for preparing a single battery cell provided in the embodiments of this application. Figure 6 yes Figure 5 The diagram shows the structural flow of the method.

[0077] This application also provides a method for preparing a battery cell, which can be used to prepare the battery cell 20 described in the above embodiments. The method for preparing the battery cell 20 specifically includes:

[0078] Step S01: Provide a current collector.

[0079] Specifically, the current collector 41 is a structural component that collects current. In lithium-ion batteries, the current collector 41 is primarily a metal foil. For example, when the electrode 40 is a positive electrode, the current collector 41 is an aluminum foil. For example, when the electrode 40 is a negative electrode, the current collector 41 is a copper foil.

[0080] Step S02: Set an active material layer, which is located at least on one side of the current collector.

[0081] Specifically, the active material layer 42 includes active materials. When preparing the positive electrode, the positive active material can be a ternary material, lithium iron phosphate, etc., designed according to specific needs. When preparing the negative electrode, the negative active material can be a carbon-based material, silicon-based material, etc., designed according to specific needs.

[0082] In one embodiment, the active material layer 42 may be formed by coating.

[0083] In one embodiment, an active material layer 42 is provided on both opposite sides of the current collector 41.

[0084] Step S03: Set a first porous layer, the first porous layer covering the active material layer, the first porous layer including a first insulating material.

[0085] Specifically, the first porous layer 43 includes a first insulating material, and the first porous layer 43 blocks electrons from passing through it. The first porous layer 43 is a membrane layer with multiple first pores, each pore size allowing ions in the electrolyte to pass through freely. In other words, the first porous layer 43 can achieve the function of allowing ions in the electrolyte to pass through freely while blocking electrons.

[0086] The first porous layer 43 is disposed on the active material layer 42, which can separate the active material layer 42 of the electrode 40 from the other electrode, thereby reducing the probability of direct contact between the active material of the positive electrode and the active material of the negative electrode, and realizing internal short circuit protection.

[0087] Step S04: Set a second porous layer, which covers the first porous layer. The second porous layer includes a second insulating material, and the porosity of the second porous layer is greater than that of the first porous layer.

[0088] Specifically, the second porous layer 44 includes a second insulating material, and the second porous layer 44 blocks electrons from passing through it. The second porous layer 44 is a membrane layer with multiple second pores, the size of which allows ions in the electrolyte to pass through freely. In other words, the second porous layer 44 can achieve the function of allowing ions in the electrolyte to pass through freely while blocking electrons.

[0089] The second porous layer 44 is deposited over the first porous layer 43, providing secondary protection for the active material layer 42. This further reduces the probability of direct contact between the active materials of the positive and negative electrodes, achieving dual internal short-circuit protection. Furthermore, the porosity of the second porous layer 44 is greater than that of the first porous layer 43. While achieving dual internal short-circuit protection, this maintains the smoothness of the ion channels formed by the cooperation of the first and second porous layers 44, ensuring the rate at which lithium ions pass through both layers, thus improving battery performance.

[0090] The electrode 40 prepared using the electrode preparation method provided in this application is used to prepare a battery. The protective function of the first porous layer 43 and the second porous layer 44 eliminates the need for a separator. The first porous layer 43 and the second porous layer 44 form an integral structure with the active material layer 42. No assembly is required between the first porous layer 43 and the second porous layer 44 and the active material layer 42, thus solving the internal short circuit problem caused by the assembly problem of the separator in existing batteries.

[0091] In one embodiment, in step S03, a first porous layer 43 is formed by a vapor deposition process; in step S04, a second porous layer 44 is formed by coating a slurry comprising a second insulating material. The first porous layer 43 formed by the vapor deposition process has a relatively dense film, i.e., small pores; the second porous layer 44 formed by the coating process has larger pores, so that the porosity of the second porous layer 44 is greater than that of the first porous layer 43, maintaining the smoothness of the ion channel formed by the cooperation of the first porous layer 43 and the second porous layer 44.

[0092] In one embodiment, the slurry used to coat and form the second porous layer 44 includes, in addition to the second insulating material, a solvent, an adhesive, and a dispersant. The solid content of the slurry is 6% to 10%; the mass percentage of the second insulating material, adhesive, and dispersant is 90% to 98% of the total mass percentage of the second insulating material, adhesive, and dispersant; the mass percentage of the adhesive is 1% to 9% of the total mass percentage of the second insulating material, adhesive, and dispersant; and the mass percentage of the dispersant is 0.1% to 1% of the total mass percentage of the second insulating material, adhesive, and dispersant. The viscosity of the slurry is 50 mPa·s to 1000 mPa·s. It is understandable that the viscosity of the slurry can be 50 mPa·s, 100 mPa·s, 200 mPa·s, 300 mPa·s, 400 mPa·s, 500 mPa·s, 600 mPa·s, 700 mPa·s, 800 mPa·s, 900 mPa·s, 1000 mPa·s, etc., or it can be a range of any two of these values, such as 50 mPa·s~600 mPa·s, 300 mPa·s~900 mPa·s, 700 mPa·s~1000 mPa·s, 300 mPa·s~1000 mPa·s, 100 mPa·s~500 mPa·s, etc.

[0093] Since the second insulating material is inorganic, an adhesive is added to ensure it adheres to the first porous layer 43. A dispersant is added to ensure the second insulating material is evenly distributed in the slurry, resulting in a more uniform distribution of the second insulating material in the formed second porous layer 44 and maintaining consistent protective effects throughout the active material layer 42. By designing the proportions of the second insulating material, adhesive, and dispersant, as well as the solid content and viscosity of the slurry, the thickness of the formed second porous layer 44 is appropriate, achieving a protective effect while maintaining smooth passage of electrolyte ions.

[0094] Optionally, the viscosity of the slurry is 50 mPa·s to 100 mPa·s. A slurry with lower viscosity is beneficial for forming a thinner second porous layer 44, which helps to reduce the resistance of the electrode 40 and improve the energy density of the battery. It can be understood that the viscosity of the slurry can be 50 mPa·s, 60 mPa·s, 70 mPa·s, 80 mPa·s, 90 mPa·s, 100 mPa·s, etc., or it can be a range of any two of these values, such as 50 mPa·s to 80 mPa·s, 60 mPa·s to 90 mPa·s, 80 mPa·s to 100 mPa·s, 70 mPa·s to 90 mPa·s, etc.

[0095] It should be noted that the electrode 40 is obtained through the above steps S01 to S04; if the positive electrode or negative electrode in the battery cell 20 is the electrode 40, the electrode 40 is wound or stacked with another existing electrode to form the battery cell 20; if both the positive electrode and the negative electrode in the battery cell 20 are electrode 40, steps S01 to S04 need to be repeated once to wind or stack the two electrode 40s (the active material layers of the two electrode 40s are made of different materials) to form the battery cell 20.

[0096] When preparing the positive electrode sheet using steps S01 to S04 provided in the embodiments of this application, the slurry used to coat and form the second porous layer 44 is an oil-based slurry, for example, the solvent used can be N-methylpyrrolidone; the slurry used to coat and form the second porous layer 44 can also be an aqueous slurry, for example, the solvent used can be water. When preparing the negative electrode sheet using steps S01 to S04 provided in the embodiments of this application, the slurry used to coat and form the second porous layer 44 is an aqueous slurry, for example, the solvent used can be water; the slurry used to coat and form the second porous layer 44 is an oil-based slurry, for example, the solvent used can be N-methylpyrrolidone.

[0097] Please refer to Figure 7 , Figure 7 This is an exploded structural diagram of a battery provided in an embodiment of this application.

[0098] The battery 100 includes a housing 10 and battery cells 20, with the battery cells 20 housed within the housing 10. The battery cells 20 can be the battery cells 20 provided in the above embodiments. The battery cells 20 can be the battery cells 20 described in the above embodiments or battery cells 20 prepared by the method for preparing the battery cells provided in the above embodiments.

[0099] The housing 10 provides a space for accommodating the battery cell 20, and can adopt various structures. In some embodiments, the housing 10 may include a first part 11 and a second part 12, which overlap each other, and together define a space for accommodating the battery cell 20. The second part 12 may be a hollow structure with one open end, and the first part 11 may be a plate-like structure, covering the open side of the second part 12 so that the first part 11 and the second part 12 together define the space; alternatively, the first part 11 and the second part 12 may both be hollow structures with one open side, with the open side of the first part 11 covering the open side of the second part 12. Of course, the housing 10 formed by the first part 11 and the second part 12 can be of various shapes, such as a cylinder, a cuboid, etc.

[0100] In battery 100, there can be multiple battery cells 20, which can be connected in series, parallel, or in a mixed manner. A mixed connection means that multiple battery cells 20 are connected in both series and parallel configurations. Multiple battery cells 20 can be directly connected in series, parallel, or in a mixed manner, and then the entire assembly of the multiple battery cells 20 is housed within the housing 10. Alternatively, battery 100 can also be composed of multiple battery cells 20 first connected in series, parallel, or in a mixed manner to form a battery module, and then multiple battery modules are connected in series, parallel, or in a mixed manner to form a whole, which is also housed within the housing 10. Battery 100 may also include other structures; for example, it may include a busbar component for electrical connection between the multiple battery cells 20.

[0101] Each battery cell 20 can be a secondary battery or a primary battery; it can also be a lithium-sulfur battery, a sodium-ion battery, or a magnesium-ion battery, but is not limited to these. The battery cell 20 can be cylindrical, flat, cuboid, or other shapes.

[0102] The batteries disclosed in this application can be used in electrical devices that use batteries as a power source or in various energy storage systems that use batteries as energy storage elements. Electrical devices can be, but are not limited to, mobile phones, tablets, laptops, electric toys, power tools, electric vehicles, electric cars, ships, spacecraft, etc. Electric toys can include stationary or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc. Spacecraft can include airplanes, rockets, space shuttles, and spacecraft, etc.

[0103] For ease of explanation, the following embodiments use a vehicle 1000 as an example of an electrical device according to an embodiment of this application. Please refer to... Figure 8 , Figure 8 This is a schematic diagram of the vehicle structure provided in an embodiment of this application.

[0104] Vehicle 1000 can be a gasoline-powered vehicle, a natural gas-powered vehicle, or a new energy vehicle. New energy vehicles can be pure electric vehicles, hybrid electric vehicles, or range-extended electric vehicles, etc. A battery 100 is installed inside vehicle 1000, which can be located at the bottom, front, or rear of vehicle 1000. Battery 100 can be used to power vehicle 1000; for example, battery 100 can serve as the operating power source for vehicle 1000. Vehicle 1000 may also include a controller 200 and a motor 300. Controller 200 controls the battery 100 to supply power to motor 300, for example, to meet the power needs of vehicle 1000 during starting, navigation, and driving.

[0105] In some embodiments of this application, the battery 100 can not only serve as the operating power source for the vehicle 1000, but also as the driving power source for the vehicle 1000, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle 1000.

[0106] This application also investigates the performance of batteries made using the electrode 40 provided in the embodiments of this application.

[0107] The preparation process of Example 1 is as follows:

[0108] (1) Preparation of negative electrode sheet:

[0109] (a) Obtain a copper foil for the negative electrode current collector with a thickness of 8 μm.

[0110] (b) A negative electrode active material graphite, conductive agent conductive carbon black, binder sodium carboxymethyl cellulose, and styrene-butadiene rubber are mixed and dispersed in a dispersant water at a mass percentage ratio of 97%:0.5%:2.5% to prepare a negative electrode active slurry. The negative electrode active slurry is coated onto a negative electrode current collector copper foil to form a negative electrode active material layer with a thickness of 120 μm.

[0111] (c) A 150 nm aluminum oxide coating is deposited on the surface of the negative electrode active material layer by vacuum evaporation to form the first porous layer.

[0112] (d) The second insulating material alumina, the adhesive acrylate, and the dispersant carboxymethyl cellulose are fully dispersed in an aqueous solvent at a mass percentage ratio of 95:4:1 to prepare a second porous layer slurry with a viscosity of 60 mPa·s. The second porous layer slurry is then coated onto the surface of the first porous layer to form a 1 μm thick second porous layer.

[0113] (e) After being compacted by a cold press, a negative electrode sheet is obtained.

[0114] (2) Preparation of positive electrode sheet:

[0115] (a) Obtain the positive current collector aluminum foil with a thickness of 13 μm.

[0116] (b) The positive electrode active material is a ternary lithium nickel cobalt manganese material (LiNi 0.6 Co 0.2 Mn 0.2 02) Conductive agent (conductive carbon black) and binder (polyvinylidene fluoride) are dispersed in N-methylpyrrolidone (N-methylpyrrolidone) at a mass percentage ratio of 97%:1%:2% to prepare a positive electrode active slurry. The positive electrode active slurry is then coated onto the positive electrode current collector aluminum foil to form a positive electrode active material layer with a thickness of 130 μm.

[0117] (c) A 150 nm aluminum oxide coating is deposited on the surface of the positive electrode active material layer by vacuum evaporation to form the first porous layer.

[0118] (d) The second insulating material, alumina, the adhesive, acrylate glue, and the dispersant, carboxymethyl cellulose, are fully dispersed in an aqueous solvent at a mass percentage ratio of 96.5%:3%:0.5% to prepare a second porous layer slurry with a viscosity of 60 mPa·s. The second porous layer slurry is then coated onto the surface of the first porous layer to form a second porous layer with a thickness of 1 μm.

[0119] (e) After being compacted by a cold press, a positive electrode sheet is obtained.

[0120] (3) Preparation of electrolyte:

[0121] Lithium salt LiPF6 was added to a mixed solvent of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a mass ratio of 35:65 and mixed thoroughly to obtain an electrolyte, wherein the molar concentration of LiPF6 in the electrolyte was 1 mol / L.

[0122] It should be noted that the prepared negative electrode sheet and positive electrode sheet are stacked in sequence and wound to obtain a bare cell, which is then inserted into the battery casing and subjected to processes such as baking, liquid injection, standing, encapsulation, formation, and capacity testing to obtain a lithium-ion battery.

[0123] The difference between Examples 2 to 11 and Example 1 is the first insulating material and thickness of the first porous layer, and the second insulating material and thickness of the second porous layer.

[0124] The difference between Comparative Example 1 and Example 1 is that the first porous layer was omitted in the preparation process of both the positive and negative electrode sheets, and the second porous layer was formed directly on the active material layer.

[0125] The difference between Comparative Example 2 and Example 1 is that the first porous layer and the second porous layer are omitted in the preparation process of both the positive and negative electrode sheets, and a diaphragm is provided between the positive and negative electrode sheets.

[0126] The relevant parameter tests for each embodiment and comparative example are as follows:

[0127] 1. The IMP1 resistance value of the battery.

[0128] Using an IMP internal resistance tester connected to the battery terminals, a constant current I is applied at a frequency of 1000 Hz. The voltage U across the battery terminals can be obtained, and the internal resistance value is U / I.

[0129] 2. Battery internal short circuit safety test.

[0130] Step 1: Charge the battery at a constant current of 0.33C to 4V, then charge at a constant voltage with a cutoff current of 0.05C, and let it stand for 30 minutes at 25℃.

[0131] Step 2: Disassemble the battery, use tools to connect the cathode tab to the anode plate to achieve an internal short circuit between the cathode and anode, and observe whether the plate catches fire.

[0132] 3. Battery cycle performance.

[0133] Step 1: Let the battery stand at 25°C for 30 minutes, discharge it at 0.33C to 2.5V, and then let it stand at 25°C for 30 minutes.

[0134] Step 2: Charge the battery at a constant current of 0.33C to 4V, then charge at a constant voltage with a cutoff current of 0.05C. Let it stand at 25℃ for 30 minutes, then discharge at 1C to 2.5V, and let it stand at 25℃ for 30 minutes. The capacity retention rate CR (%) after n cycles = (discharge capacity of the nth cycle / discharge capacity of the first cycle) × 100%. Measure the capacity retention rate after 2000 cycles.

[0135] Table 1. Test data of relevant parameters for each embodiment and comparative example.

[0136]

[0137]

[0138] Comparing Examples 1 to 5, it is evident that the thicker the first porous layer 43, the higher the battery resistance. Comparing Examples 1, 6 to 9, it is evident that the thicker the second porous layer 44, the higher the battery resistance. Comparing Examples 2 and 11, it is evident that when the particle size of boehmite is slightly smaller than that of alumina, and the second porous layer 44 is denser, the battery resistance slightly increases. Comparing Examples 1 to 11 with Comparative Example 1, it is evident that when only the second porous layer 44 is provided on the surface of the active material layer 42, without the first porous layer 43, the battery immediately ignites during short-circuit stability testing. Comparing Examples 1 to 12 with Comparative Example 2, it is evident that the resistance of the separatorless battery provided in this application is significantly lower than that of the separator-containing battery, which is beneficial for improving battery electrical performance.

[0139] The above description is merely an embodiment of this application and does not limit the patent scope of this application. Any equivalent structural or procedural transformations made using the content of this application's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of this application.

Claims

1. A battery cell, comprising a positive electrode and a negative electrode, characterized in that, At least one of the positive electrode and the negative electrode includes: current collector; An active material layer is located at least on one side of the current collector; A first porous layer, the first porous layer being disposed over the active material layer, the first porous layer comprising a first insulating material; and A second porous layer is disposed on top of the first porous layer. The second porous layer includes a second insulating material, and the porosity of the second porous layer is greater than that of the first porous layer.

2. The battery cell according to claim 1, characterized in that, The first insulating material includes at least one of metal oxides and inorganic non-metal oxides.

3. The battery cell according to claim 1 or 2, characterized in that, The first insulating material includes at least one of aluminum oxide, zirconium oxide, titanium oxide, magnesium oxide, and silicon oxide.

4. The battery cell according to any one of claims 1 to 3, characterized in that, The thickness of the first porous layer is 100nm to 1000nm.

5. The battery cell according to any one of claims 1 to 4, characterized in that, The thickness of the first porous layer is 150 nm to 250 nm.

6. The battery cell according to any one of claims 1 to 5, characterized in that, The first porous layer is a porous layer in which the first insulating material is continuously distributed.

7. The battery cell according to any one of claims 1 to 6, characterized in that, The second insulating material includes at least one of metal oxides, inorganic non-metal oxides, and hydroxides of metal oxides.

8. The battery cell according to any one of claims 1 to 7, characterized in that, The second insulating material includes at least one of aluminum oxide, zirconium oxide, titanium oxide, magnesium oxide, silicon oxide, and boehmite.

9. The battery cell according to any one of claims 1 to 8, characterized in that, The second porous layer further includes an adhesive and a dispersant; the second insulating material accounts for 90% to 98% of the total mass of the second insulating material, the adhesive, and the dispersant, the adhesive accounts for 1% to 9% of the total mass of the second insulating material, the adhesive, and the dispersant, and the dispersant accounts for 0.1% to 1% of the total mass of the second insulating material, the adhesive, and the dispersant.

10. The battery cell according to claim 9, characterized in that, The adhesive includes at least one of acrylic polymers, polyvinylidene fluoride polymers, and styrene-butadiene rubber polymers; and / or, the dispersant includes at least one of calcium hydroxide, carboxymethyl cellulose, and polyvinyl alcohol.

11. The battery cell according to any one of claims 1 to 10, characterized in that, The thickness of the second porous layer is 1 μm to 4 μm.

12. The battery cell according to any one of claims 1 to 11, characterized in that, The thickness of the second porous layer is 1 μm to 2 μm.

13. The battery cell according to any one of claims 1 to 12, characterized in that, The second porous layer is a porous layer in which the particles of the second insulating material are spaced apart.

14. A method for preparing a battery cell according to any one of claims 1 to 13, characterized in that, include: Provide a fluid collection; An active material layer is provided, wherein the active material layer is located at least on one side of the current collector; A first porous layer is provided, which covers the active material layer, and the first porous layer includes a first insulating material; as well as A second porous layer is provided, which covers the first porous layer. The second porous layer includes a second insulating material, and the porosity of the second porous layer is greater than that of the first porous layer.

15. The method for preparing a battery cell according to claim 14, characterized in that, The first porous layer is formed by a vapor deposition process; the second porous layer is formed by coating a slurry comprising the second insulating material.

16. The method for preparing a single battery cell according to claim 15, characterized in that, The slurry further includes a solvent, an adhesive, and a dispersant; the solid content of the slurry is 6% to 10%; the second insulating material accounts for 90% to 98% of the total mass of the second insulating material, the adhesive, and the dispersant, the adhesive accounts for 1% to 9% of the total mass of the second insulating material, the adhesive, and the dispersant, and the dispersant accounts for 0.1% to 1% of the total mass of the second insulating material, the adhesive, and the dispersant; the viscosity of the slurry is 50 mPa·s to 1000 mPa·s.

17. A battery, characterized in that, This includes the battery cell as described in any one of claims 1 to 13 or the battery cell prepared by the method described in any one of claims 14 to 16.

18. An electrical appliance, characterized in that, Includes the battery as described in claim 17.

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