Pole core, battery cell and electric device

Abstract

The application discloses a pole core, an electric core and an electric device, and relates to the technical field of batteries. The pole core comprises a positive pole sheet and a negative pole sheet which are arranged in a stack, and a diaphragm arranged between the positive pole sheet and the negative pole sheet. At least one side of the diaphragm is provided with a coating, and a plurality of deformable microspheres are arranged in the coating. The deformable microspheres can be expanded by heat to adjust the spacing between the positive pole sheet and the negative pole sheet. When the temperature inside the battery reaches a certain degree, the deformable microspheres in the coating can be expanded by heat to increase the spacing between the positive pole sheet and the negative pole sheet, reduce the possibility of local short circuit of the positive pole sheet interface and the negative pole sheet interface, avoid further thermal runaway, and improve the safety and reliability of the electric core.

Description

Technical Field

[0001] This application belongs to the field of battery technology, specifically relating to an electrode core, a battery cell, and an electrical device. Background Technology

[0002] Currently, lithium batteries are widely used rechargeable batteries. Lithium batteries are mainly composed of positive electrode materials, negative electrode materials, separators, and electrolytes. Among the components of a lithium battery, the separator plays a crucial role. The performance of the separator determines the battery's interface structure, internal resistance, and other characteristics, affecting the battery's capacity, cycle life, and safety performance. A high-performance separator plays an important role in improving the overall performance of the battery.

[0003] In related technologies, the diaphragm shrinks under high temperature conditions, which reduces the diaphragm's isolation effect between the positive and negative electrodes, and may even cause local short circuits at the positive and negative electrode interfaces, thereby triggering a series of chain thermal runaway reactions. Utility Model Content

[0004] This application aims to provide an electrode core, a battery cell, and an electrical device that can solve the problem in related technologies where the separator shrinks under high temperature conditions, which reduces the separator's isolation effect between the positive and negative electrodes, and may even cause local short circuits at the positive and negative electrode interfaces, thereby triggering a series of chain thermal runaway reactions.

[0005] To solve the above-mentioned technical problems, this application is implemented as follows:

[0006] In a first aspect, embodiments of this application propose an electrode core, comprising: a positive electrode sheet and a negative electrode sheet stacked together, and a separator disposed between the positive electrode sheet and the negative electrode sheet, wherein at least one side of the separator is provided with a coating, and the coating is provided with a plurality of deformable microspheres, the deformable microspheres being able to expand upon heating to adjust the spacing between the positive electrode sheet and the negative electrode sheet.

[0007] Optionally, the diameter expansion rate η of the deformable microsphere satisfies: 100% ≤ η ≤ 300%.

[0008] Optionally, the coefficient of linear expansion of the deformable microsphere is α, satisfying: α ≥ 0.07℃ -1 .

[0009] Optionally, the thickness of the diaphragm is d1, which satisfies: 7μm≤d1≤14μm.

[0010] Optionally, the deformable microsphere has an initial state and an expanded state. When the deformable microsphere is in the initial state, the diameter of the deformable microsphere is d2, which satisfies: 3μm≤d2≤5μm.

[0011] Optionally, when the deformable microsphere is in the expanded state, the diameter of the deformable microsphere is d3, which satisfies: 6μm≤d3≤20μm.

[0012] Optionally, when the deformable microspheres are in the initial state, the thickness of the coating is d4, satisfying: 3μm≤d4≤7μm.

[0013] Optionally, the deformable microspheres include at least one of polyvinyl alcohol microspheres, polystyrene microspheres, or polyacrylate microspheres.

[0014] Secondly, embodiments of this application propose a battery cell, comprising: any of the electrode cores described above.

[0015] Thirdly, embodiments of this application propose an electrical device comprising: an electrode core as described above; or, a battery cell as described above.

[0016] In the embodiments of this application, the electrode core includes a positive electrode and a negative electrode stacked together, and a separator disposed between the positive and negative electrode sheets. At least one side of the separator is provided with a coating containing a plurality of deformable microspheres. These deformable microspheres can expand upon heating to adjust the spacing between the positive and negative electrode sheets. Thus, when the internal temperature of the battery reaches a certain level, the deformable microspheres in the coating can expand upon heating, increasing the spacing between the positive and negative electrode sheets, reducing the possibility of local short circuits at the positive and negative electrode interfaces, preventing further thermal runaway, and improving the safety and reliability of the battery cell.

[0017] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0018] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0019] Figure 1 This is a schematic diagram of the deformable microspheres in the electrode core in the initial state according to an embodiment of this application;

[0020] Figure 2 This is a schematic diagram of the deformable microspheres in the electrode core in an expanded state according to an embodiment of this application;

[0021] Figure 3 According to the embodiments of this application Figure 1 An enlarged view of part A, shown in the middle circle.

[0022] Figure label:

[0023] 1: Positive electrode sheet; 11: Positive electrode active material layer; 12: Positive electrode current collector; 2: Negative electrode sheet; 21: Negative electrode active material layer; 22: Negative electrode current collector; 3: Separator; 4: Coating; 41: Deformable microspheres. Detailed Implementation

[0024] The embodiments of this application will now be described in detail. Examples of these embodiments are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this application, and should not be construed as limiting this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0025] The terms "first" and "second" in the specification and claims of this application may explicitly or implicitly include one or more of the features. In the description of this application, unless otherwise stated, "multiple" means two or more. Furthermore, "and / or" in the specification and claims indicates at least one of the connected objects, and the character " / " generally indicates that the preceding and following objects are in an "or" relationship.

[0026] In the description of this application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicating the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0027] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0028] Before explaining the electrode core, battery cell, and electrical equipment provided in the embodiments of this application, the application scenarios of the electrode core, battery cell, and electrical equipment provided in the embodiments of this application will be specifically described:

[0029] Currently, lithium batteries are widely used rechargeable batteries. A lithium battery mainly consists of positive electrode materials, negative electrode materials, a separator, and electrolyte. The separator plays a crucial role in the battery's structure; its performance determines the battery's interface structure, internal resistance, and other characteristics, affecting its capacity, cycle life, and safety performance. A high-performance separator is essential for improving the overall performance of the battery. The main function of the separator is to separate the positive and negative electrodes, preventing short circuits caused by contact between them. The separator also allows electrolyte ions to pass freely while preventing electrons from passing through.

[0030] When the internal temperature of a battery rises or thermal runaway occurs, the internal temperature may reach approximately 70°C due to heating, short circuits, or other reasons. At this point, the anode SEI film begins to decompose, and the lithium embedded in the graphite reacts with the electrolyte, further increasing the internal temperature. During this process, the separator in related technologies typically shrinks at 120°C, causing a localized short circuit between the positive and negative electrode interfaces, which in turn triggers a chain reaction of subsequent thermal runaway.

[0031] Therefore, this application provides an electrode core, a battery cell, and an electrical device. The electrode core, battery cell, and electrical device provided in this application will be described in detail below with reference to the accompanying drawings and through specific embodiments and application scenarios.

[0032] like Figure 1 and Figure 2 As shown, the electrode core according to some embodiments of this application includes a positive electrode 1 and a negative electrode 2 stacked together, and a separator 3 disposed between the positive electrode 1 and the negative electrode 2. At least one side of the separator 3 is provided with a coating 4, and a plurality of deformable microspheres 41 are provided in the coating 4. The deformable microspheres 41 can expand when heated to adjust the spacing between the positive electrode 1 and the negative electrode 2.

[0033] In this embodiment, the coating 4 on the separator 3 is provided with a plurality of deformable microspheres 41. This allows the deformable microspheres 41 in the coating to expand when the internal temperature of the battery reaches a certain level, thereby increasing the distance between the positive electrode 1 and the negative electrode 2, reducing the possibility of local short circuit between the interface of the positive electrode 1 and the interface of the negative electrode 2, avoiding further thermal runaway, and improving the safety and reliability of the cell.

[0034] In specific applications, the multiple deformable microspheres 41 in the coating 4 can be arranged arbitrarily to form a single layer or multiple layers in the coating 4. The specific number of deformable microspheres 41 can be determined according to the volume of the coating 4, as long as the multiple deformable microspheres 41 can increase the distance between the positive electrode 1 and the negative electrode 2 when the internal temperature of the battery cell rises. Those skilled in the art can set it according to actual needs, and this application does not limit it in this regard.

[0035] Understandably, at least one side of the diaphragm 3 is provided with a coating 4, that is, the coating 4 can be provided on one side of the diaphragm 3, or on both sides, that is, it can be a single-sided coating or a double-sided coating. Those skilled in the art can make the setting according to actual needs, and this application does not limit it.

[0036] In some embodiments of this application, the coating 4 comprises 20wt% to 70wt% of deformable microspheres 41, 10wt% to 30wt% of binder, 5wt% to 15wt% of plasticizer, and 5wt% to 20wt% of additives, thereby enabling easy mixing to form the coating 4 attached to the diaphragm 3 and reducing the processing difficulty of the coating 4. Here, wt% represents "mass percentage," and wt is an abbreviation for weight, indicating the weight ratio, i.e., the proportion of one substance in the mixture.

[0037] In specific applications, the adhesive can be at least one of polyvinyl alcohol (PVA), carboxymethyl cellulose (CMC), and polyvinylidene difluoride (PVDF), thereby increasing the range of adhesives that can be selected for the coating 4 and reducing the processing difficulty. Of course, other adhesives that can achieve the bonding function can also be used. Those skilled in the art can set the adhesive according to the actual situation, and this application does not limit it.

[0038] The plasticizer is specifically dichloromethane (DCM), which can improve the plasticity and flexibility of coating 4. Of course, other types of plasticizers can also be used. Those skilled in the art can set them according to actual needs, and this application does not limit them.

[0039] The additive is at least one of polyoxyethylene dioleate and polytetraethylene glycol monostearate.

[0040] like Figure 1 and Figure 2 As shown, in some embodiments of this application, the positive electrode 1 includes a positive current collector 12 and a positive active material layer 11 attached thereto, and the positive active material layer 11 may be disposed on at least one side of the positive current collector 12.

[0041] The positive electrode current collector 12 can be an aluminum current collector, which meets the energy density requirements of the battery cell while being more cost-effective. The material of the positive electrode active material layer 11 can specifically include at least one of lithium iron phosphate, lithium manganese oxide, lithium cobalt oxide, ternary nickel cobalt manganese, etc., which has higher power density, better stability, and lower cost.

[0042] like Figure 1 and Figure 2 As shown, in some embodiments of this application, the negative electrode 2 includes a negative electrode current collector 22 and a negative electrode active material layer 21 attached thereto, and the negative electrode active material layer 21 may be disposed on at least one side of the negative electrode current collector 22.

[0043] The negative electrode current collector 22 can be a copper current collector, etc., and the material of the negative electrode active material layer 21 can specifically include at least one of graphite, silicon-based composite material, metal oxide, metal sulfide, etc.

[0044] In some embodiments of this application, the deformable microspheres 41 include at least one of polyvinyl alcohol microspheres, polystyrene microspheres, or polyacrylate microspheres.

[0045] In the embodiments of this application, by setting the deformable microspheres 41 as at least one of polyvinyl alcohol microspheres, polystyrene microspheres or polyacrylate microspheres, the selectability of the deformable microspheres 41 is improved, the flexibility in coating 4 preparation is increased, and the cost of coating 4 is reduced.

[0046] In specific applications, the deformable microspheres 41 can be one of polyvinyl alcohol microspheres, polystyrene microspheres, or polyacrylate microspheres, or a combination of two or more. Those skilled in the art can set them according to actual needs, and this application does not limit them.

[0047] It should be explained that polyvinyl alcohol microspheres, polystyrene microspheres, or polyacrylate microspheres have good thermal expansion properties and can expand rapidly when heated, thereby deforming in the coating 4 and separating the positive electrode 1 and negative electrode 2 that are in contact with the coating 4, reducing the possibility of short circuit between the two and improving the reliability and safety of the battery cell.

[0048] In some embodiments of this application, the diameter expansion rate of the deformable microsphere 41 is η, which satisfies: 100% ≤ η ≤ 300%.

[0049] In this embodiment of the application, by setting the diameter expansion rate η of the deformable microsphere 41 within a reasonable range, the ability of the deformable microsphere 41 to adjust the distance between the positive electrode 1 and the negative electrode 2 is ensured, and short circuit between the positive electrode 1 and the negative electrode 2 is avoided when the temperature is too high; at the same time, the distance between the positive electrode 1 and the negative electrode 2 is also avoided from being too large, which would affect the conductivity and energy conversion efficiency of the electrode core.

[0050] It should be noted that when η < 100%, the volume change of the deformable microspheres 41 after thermal expansion is too small, resulting in a small change in the distance between the positive electrode 1 and the negative electrode 2, which cannot completely prevent short circuits between the interfaces of the positive electrode 1 and the negative electrode 2. When η > 300%, the volume change of the deformable microspheres 41 after thermal expansion is too large, resulting in a large change in the distance between the positive electrode 1 and the negative electrode 2, which results in an excessively high internal resistance of the cell, thereby reducing the overall performance of the cell. It also results in an excessively large overall volume of the electrode core, causing defects such as shell deformation.

[0051] In specific applications, the diameter expansion rate η of the deformable microsphere 41 can be set to any value or a range between any two values, such as 100%, 120%, 140%, 160%, 180%, 200%, 220%, 240%, 260%, 280%, 300%.

[0052] It should be explained that the diameter expansion rate η refers to the proportion by which the diameter of a material or structure changes with temperature, pressure, or other factors under certain conditions. Specifically, it is shown in Formula 1 below:

[0053] η=Δd / d0 (1)

[0054] Where Δd is the difference in diameter before and after the change; d0 is the initial diameter.

[0055] In this application, the diameter expansion rate η refers to the proportion of diameter change of the deformable microsphere 41 before and after thermal expansion.

[0056] In specific applications, the diameter of the deformable microspheres 41 can be measured or calculated using electron microscopy, optical microscopy, laser scattering, or particle size analysis.

[0057] In some embodiments of this application, the coefficient of linear expansion of the deformable microspheres 41 is α, satisfying: α ≥ 0.07℃ -1 .

[0058] In this embodiment of the application, by setting the linear expansion coefficient α of the deformable microsphere 41 within a reasonable range, it can be ensured that the deformable microsphere 41 can expand rapidly when the internal temperature of the cell reaches a certain level, so as to increase the distance between the positive electrode 1 and the negative electrode 2, reduce the possibility of short circuit inside the cell, and curb the occurrence of thermal runaway.

[0059] It should be noted that when α < 0.07℃ -1 As the temperature increases, the expansion rate of the deformable microspheres 41 is too slow, which cannot increase the distance between the positive electrode 1 and the negative electrode 2 in time. This increases the possibility of short circuit between the positive electrode 1 and the negative electrode 2, and makes it impossible to contain the thermal runaway in time.

[0060] In specific applications, the linear expansion coefficient α of the deformable microspheres 41 can be set to 0.07℃. -1 0.1℃ -1 0.15℃ -1 0.2℃ -1 0.25℃ -1 0.3℃ -1 0.35℃ -1 0.4℃ -1 0.45℃ -1 0.5℃ -1 0.55℃ -1 0.6℃ -1 0.65℃ -1 0.7℃ -1 Any number or the range between any two numbers.

[0061] It should be explained that the coefficient of linear expansion α refers to the elongation per unit length of a solid material when its temperature increases by 1°C. In this application, it refers to the elongation of the diameter of the deformable microsphere 41 when its temperature increases by 1°C. Specifically, it is shown in Formula 2 below:

[0062] α=Δd / (d0ΔT) (2)

[0063] Where α is in °C -1 or k -1 Δd is the difference in diameter before and after the change; d0 is the initial diameter; ΔT is the difference in temperature before and after the change, in °C or K.

[0064] In actual use, the deformable microspheres 41 expand at 60°C and expand to their maximum size at 150°C.

[0065] like Figure 1 , Figure 2 and Figure 3 As shown, in some embodiments of this application, the thickness of the diaphragm 3 is d1μm, which satisfies: 7μm≤d1≤14μm.

[0066] In this embodiment of the application, by setting the thickness d1 of the separator 3 within a reasonable range, the safety of the battery cell can be guaranteed while ensuring the battery capacity.

[0067] It should be noted that when the thickness d1 of the separator 3 is less than 7 μm, the separator 3 is too thin and is prone to deformation when the temperature rises, causing the positive electrode 1 and the negative electrode 2 to short-circuit; while when the thickness d1 of the separator 3 is greater than 14 μm, it will increase the core volume and affect the discharge performance of the cell.

[0068] In specific applications, the thickness d1 of the diaphragm 3 can be set to any value or a range between any two values, such as 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm.

[0069] It should be explained that the material of the diaphragm 3 can be at least one of polypropylene, polyethylene, copolymer of propylene and ethylene, polyethylene homopolymer, etc. Those skilled in the art can choose according to actual needs, and this application does not limit it.

[0070] like Figure 1 and Figure 3 As shown, in some embodiments of this application, the deformable microsphere 41 has an initial state and an expanded state. When the deformable microsphere 41 is in the initial state, the diameter of the deformable microsphere 41 is d2μm, which satisfies: 3μm≤d2≤5μm.

[0071] In this embodiment, the deformable microsphere 41 is in its initial state when it is not heated. By setting the diameter d2 of the deformable microsphere 41 in its initial state within a reasonable range, it is possible to avoid the gap between the positive electrode 1 and the negative electrode 2 being too small, which could easily lead to a short circuit. At the same time, it is possible to avoid the internal resistance of the cell being too large and the overall size of the electrode core being too large, which would affect the energy density of the cell.

[0072] It should be explained that when the diameter d2 of the deformable microsphere 41 in the initial state is less than 3 μm, the overall size of the separator 3 between the positive electrode 1 and the negative electrode 2 and the deformable microsphere 41 is too small, that is, the distance between the positive electrode 1 and the negative electrode 2 is too small, and they are prone to short circuit. When the diameter d2 of the deformable microsphere 41 in the initial state is greater than 5 μm, the overall size of the separator 3 between the positive electrode 1 and the negative electrode 2 and the deformable microsphere 41 is too large, that is, the distance between the positive electrode 1 and the negative electrode 2 is too large, which makes the internal resistance of the cell too large and the overall size of the electrode core too large, affecting the energy density of the cell.

[0073] In specific applications, the diameter d2 of the deformable microsphere 41 in the initial state can be set to any value or a range between any two values, such as 3μm, 3.5μm, 4μm, 4.5μm, 5μm.

[0074] Understandably, the deformable microspheres 41 are in their initial state when they are not deformed by heat. At this time, the deformable microspheres 41 are normally in the coating 4. When the deformable microspheres 41 are heated and expanded to their maximum size, they are in an expanded state. At this time, the deformable microspheres 41 can increase the overall thickness of the coating 4, or they can destroy the structure of the coating 4 and break out of the coating 4. The specific form is related to the structure of the coating 4. Those skilled in the art can set it according to the actual situation. This application does not limit it.

[0075] like Figure 2 As shown, in some embodiments of this application, when the deformable microsphere 41 is in an expanded state, the diameter of the deformable microsphere 41 is d3μm, which satisfies: 6μm≤d3≤20μm.

[0076] In this embodiment of the application, by setting the diameter d3 of the deformable microsphere 41 in the expanded state within a reasonable range, it can be ensured that the diameter of the deformable microsphere 41 after expansion is large enough when the internal temperature of the cell rises, thereby increasing the distance between the positive electrode 1 and the negative electrode 2 to a suitable range and reducing the possibility of short circuit between the positive electrode 1 and the negative electrode 2; at the same time, it can also ensure the normal operation of the cell.

[0077] It should be explained that when the diameter d3 of the deformable microsphere 41 in the expanded state is less than 6 μm, the expansion of the deformable microsphere 41 does not increase the distance between the positive electrode 1 and the negative electrode 2 by a sufficient scale, and there is still a risk of short circuit between the positive electrode 1 and the negative electrode 2; while when the diameter d3 of the deformable microsphere 41 in the expanded state is greater than 20 μm, the distance between the positive electrode 1 and the negative electrode 2 is too large, and the ions between the positive electrode 1 and the negative electrode 2 cannot move normally, so the cell cannot operate normally.

[0078] In specific applications, the diameter d3 of the deformable microsphere 41 in the expanded state can be set to any value or a range between any two values, such as 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm, 15μm, 16μm, 17μm, 18μm, 19μm, 20μm.

[0079] like Figure 1 and Figure 3 As shown, in some embodiments of this application, when the deformable microspheres 41 are in their initial state, the thickness of the coating 4 is d4μm, satisfying: 3μm≤d4≤7μm.

[0080] In this embodiment of the application, by setting the thickness d4 of the coating 4 in the initial state of the deformable microsphere 41 within a reasonable range, it is possible to avoid the gap between the positive electrode 1 and the negative electrode 2 being too small, which could easily lead to a short circuit between them; at the same time, it is possible to avoid the internal resistance of the cell being too large and the overall size of the electrode core being too large, which would affect the energy density of the cell.

[0081] It should be explained that when the thickness d4 of the coating 4 in the initial state of the deformable microspheres 41 is less than 3 μm, the overall size of the separator 3 and the coating 4 set between the positive electrode 1 and the negative electrode 2 is too small, that is, the distance between the positive electrode 1 and the negative electrode 2 is too small, and the two are prone to short circuit; when the thickness d4 of the coating 4 in the initial state of the deformable microspheres 41 is greater than 7 μm, the overall size of the separator 3 and the coating 4 set between the positive electrode 1 and the negative electrode 2 is too large, that is, the distance between the positive electrode 1 and the negative electrode 2 is too large, which makes the internal resistance of the cell too large and the overall size of the electrode core too large, affecting the energy density of the cell.

[0082] In specific applications, the thickness d4 of the coating 4 in the initial state of the deformable microsphere 41 can be set to any value or a range between any two values, such as 3μm, 3.5μm, 4μm, 4.5μm, 5μm, 5.5μm, 6μm, 6.5μm, 5μm.

[0083] Understandably, the deformable microspheres 41 are in their initial state when not deformed by heat, and are normally contained within the coating 4. When heated and expanded to their maximum size, the deformable microspheres 41 are in an expanded state, increasing the overall thickness of the coating 4. This means the thickness of the coating 4 is the same as the diameter d3 of the deformable microspheres 41 in the expanded state. The overall expansion of the coating 4 increases the distance between the positive electrode 1 and the negative electrode 2. Alternatively, the deformable microspheres 41 may expand and break through the structure of the coating 4, thus the thickness d4 of the coating 4 remains unchanged, while only the diameter of the deformable microspheres 41 changes before and after expansion. This expansion increases the distance between the positive electrode 1 and the negative electrode 2. The specific change in the thickness of the coating 4 depends on its structure.

[0084] This application also provides a method for preparing the electrode core, as detailed below:

[0085] S1. Slurry preparation: The adhesive and additives are thoroughly mixed to form a glue solution; then the deformable microspheres 41 and plasticizer are thoroughly mixed with the above glue solution to obtain the slurry of coating 4.

[0086] S2. Diaphragm preparation: The slurry of the obtained coating 4 is coated onto the diaphragm 3;

[0087] S3. Electrode core assembly: The positive electrode 1 and the negative electrode 2 are wound or stacked with the separator 3 prepared above to obtain the electrode core.

[0088] The preparation processes for positive electrode 1 and negative electrode 2 are the same as those for conventional preparation processes, and will not be described in detail here.

[0089] The following specific examples and comparative results illustrate the impact of selecting the aforementioned deformable microspheres 41 on the battery cell:

[0090] Example 1:

[0091] Step 1: Mix 20wt% of adhesive and 20wt% of additive thoroughly to form an adhesive solution; then mix 50wt% of polyvinyl alcohol microspheres and 10wt% of plasticizer with the above adhesive solution to obtain the slurry of coating 4, wherein the diameter of the polyethylene microspheres before expansion is 3μm;

[0092] Step 2: The obtained coating 4 is applied to the diaphragm 3, wherein the thickness of the coating 4 is 3 μm and the thickness of the diaphragm 3 is 7 μm, to obtain the diaphragm 3 with the coating 4.

[0093] Step 3: The positive electrode 1 and the negative electrode 2 are wound or stacked with the separator 3 prepared above to obtain the electrode core;

[0094] Step 4: The obtained electrode core is used to prepare a battery cell. The preparation process of the electrode core to prepare a battery cell is the same as that of a conventional battery cell, and will not be described in detail here.

[0095] Example 2:

[0096] The difference between this embodiment and Embodiment 1 is that the deformable microsphere 41 in step 1 is a polystyrene microsphere, and the diameter of the polystyrene microsphere before expansion is 3 μm.

[0097] Example 3:

[0098] The difference between this embodiment and Embodiment 1 is that the diameter of the polyethylene microspheres before expansion in step 1 is 5 μm; and the thickness of coating 4 in step 2 is 7 μm.

[0099] Example 4:

[0100] The difference between this embodiment and Embodiment 1 is that the content of polyvinyl alcohol microspheres in step 1 is 70 wt%, the content of adhesive is 10 wt%, and the content of additive is 10 wt%.

[0101] Comparative example:

[0102] The difference between this comparative example and the above embodiments is that the preparation process does not involve steps 1 and 2, that is, the slurry of coating 4 is not applied to the diaphragm 3.

[0103] In actual processing, the following battery cells, under the same conditions, are obtained using the above preparation method:

[0104] The same conditions are as follows:

[0105] All cells are square aluminum-cased, with graphite as the negative electrode material. Their dimensions are 52mm*148mm*106mm, and the rated voltage is 2.8~4.4V. All other components in each cell are identical, such as the material and dimensions of the positive electrode 1 and the negative electrode 2.

[0106] The battery cells described in the above comparative examples and four embodiments were all subjected to high-temperature internal resistance tests and heating boundary tests. The specific experimental methods are as follows:

[0107] 1. High-temperature internal resistance test:

[0108] The DC resistance (DCR) of the battery cells obtained in the above embodiments and comparative examples was tested at a temperature of 60°C. The magnitude of the DC resistance of the battery cells can be used to determine the impact of different selections of deformable microspheres 41 on the battery cells.

[0109] 2. Heating boundary test:

[0110] The battery cells obtained in the above embodiments and comparative examples were heated at a heating rate of 5°C / min until thermal runaway occurred. During this process, the temperature at which each battery cell reached the thermal runaway boundary and the highest temperature at which thermal runaway occurred were measured. By testing the thermal runaway boundary temperature and the highest temperature of each battery cell, the influence of different selections of deformable microspheres 41 on the control capability of the battery cell's internal temperature can be intuitively understood.

[0111] The test results are shown in Table 1 below:

[0112] Table 1: Test Results

[0113]

[0114] As can be seen from Table 1 above:

[0115] Compared to the comparative example, in Example 1, a coating 4 with a thickness of 3 μm is provided on the diaphragm 3, wherein the coating 4 includes 50 wt% polyvinyl alcohol microspheres, which can increase the DC internal resistance of the battery cell by 19.7%, increase the thermal runaway boundary temperature by 16°C, and reduce the maximum temperature by 40°C.

[0116] Compared to the comparative example, in Example 2, a coating 4 with a thickness of 3 μm is provided on the diaphragm 3, wherein the coating 4 includes 50 wt% polystyrene microspheres, which can increase the DC internal resistance of the battery cell by 22.7%, increase the thermal runaway boundary temperature by 14°C, and reduce the maximum temperature by 59°C.

[0117] Compared to the comparative example, in Example 3, a coating 4 with a thickness of 7 μm is provided on the diaphragm 3, wherein the coating 4 includes 50 wt% polyvinyl alcohol microspheres, which can increase the DC internal resistance of the battery cell by 33.3%, increase the thermal runaway boundary temperature by 28°C, and reduce the maximum temperature by 71°C.

[0118] Compared to the comparative example, in Example 4, a coating 4 with a thickness of 3 μm is provided on the diaphragm 3, wherein the coating 4 includes 70 wt% polyvinyl alcohol microspheres, which can increase the DC internal resistance of the battery cell by 24.2%, increase the thermal runaway boundary temperature by 20°C, and reduce the maximum temperature by 49°C.

[0119] Therefore, it can be seen that applying a coating 4 with deformable microspheres 41 to the separator 3 in the battery cell can increase the DC internal resistance of the battery cell, raise the thermal runaway boundary temperature of the battery cell, and reduce the maximum temperature of the battery cell, thereby improving the reliability and safety of the battery cell. Furthermore, a comparison between Examples 1 and 2 shows that polyvinyl alcohol microspheres are slightly more effective than polystyrene microspheres; a comparison between Examples 1 and 3 shows that increasing the thickness of the coating 4 can improve the safety performance of the battery cell; and a comparison between Examples 1 and 4 shows that increasing the content of deformable microspheres 41 can improve the safety performance of the battery cell.

[0120] In some embodiments of this application, a battery cell is also proposed, comprising the electrode core as described in any of the above embodiments.

[0121] In this embodiment, the electrode core includes a positive electrode 1 and a negative electrode 2 stacked together, and a separator 3 disposed between the positive electrode 1 and the negative electrode 2. At least one side of the separator 3 is provided with a coating 4, which contains a plurality of deformable microspheres 41. These deformable microspheres 41 can expand upon heating to adjust the spacing between the positive electrode 1 and the negative electrode 2. This allows the deformable microspheres 41 in the coating to expand upon heating when the internal temperature of the battery reaches a certain level, increasing the spacing between the positive electrode 1 and the negative electrode 2. This reduces the possibility of local short circuits at the interface between the positive electrode 1 and the negative electrode 2, preventing further thermal runaway and improving the safety and reliability of the battery cell.

[0122] In specific applications, the battery cell can be at least one of square batteries, cylindrical batteries, or pouch batteries, etc. Those skilled in the art can make the configuration according to actual needs, and this application does not impose any restrictions on it.

[0123] In some embodiments of this application, an electrical device is also proposed, including an electrode core as described in any of the above embodiments; or, a battery cell as described in the above embodiments.

[0124] In this embodiment, the electrode core includes a positive electrode 1 and a negative electrode 2 stacked together, and a separator 3 disposed between the positive electrode 1 and the negative electrode 2. At least one side of the separator 3 is provided with a coating 4, which contains a plurality of deformable microspheres 41. These deformable microspheres 41 can expand upon heating to adjust the spacing between the positive electrode 1 and the negative electrode 2. This allows the deformable microspheres 41 in the coating to expand upon heating when the internal temperature of the battery reaches a certain level, increasing the spacing between the positive electrode 1 and the negative electrode 2. This reduces the possibility of local short circuits at the interface between the positive electrode 1 and the negative electrode 2, preventing further thermal runaway and improving the safety and reliability of the battery cell.

[0125] In specific applications, electrical equipment can include laptops, pen-based computers, mobile computers, e-book players, portable telephones, portable fax machines, portable copiers, portable printers, stereo headphones, video recorders, LCD TVs, portable cleaners, portable CD players, mini CDs, transceivers, electronic notebooks, calculators, memory cards, portable recorders, radios, backup power supplies, motors, automobiles, motorcycles, electric bicycles, bicycles, ships, spacecraft, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, large household batteries, and lithium-ion capacitors, etc.

[0126] Specifically, the vehicles can be gasoline-powered vehicles, natural gas-powered vehicles, or new energy vehicles. New energy vehicles can be pure electric vehicles, hybrid electric vehicles, or range-extended electric vehicles, etc.

[0127] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0128] Although embodiments of this application have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of this application, the scope of which is defined by the claims and their equivalents.

Claims

1. An electrode core, characterized in that, include: A positive electrode (1) and a negative electrode (2) are stacked together, and a separator (3) is disposed between the positive electrode (1) and the negative electrode (2). At least one side of the separator (3) is provided with a coating (4). The coating (4) is provided with a plurality of deformable microspheres (41). The deformable microspheres (41) can expand when heated to adjust the spacing between the positive electrode (1) and the negative electrode (2).

2. The electrode core according to claim 1, characterized in that, The diameter expansion rate of the deformable microsphere (41) is η, which satisfies: 100%≤η≤300%.

3. The electrode core according to claim 1, characterized in that, The coefficient of linear expansion of the deformable microsphere (41) is α, which satisfies: α ≥ 0.07℃ -1 .

4. The electrode core according to claim 1, characterized in that, The thickness of the diaphragm (3) is d1, which satisfies: 7μm≤d1≤14μm.

5. The electrode core according to any one of claims 1-4, characterized in that, The deformable microsphere (41) has an initial state and an expanded state. When the deformable microsphere (41) is in the initial state, the diameter of the deformable microsphere (41) is d2, which satisfies: 3μm≤d2≤5μm.

6. The electrode core according to claim 5, characterized in that, When the deformable microsphere (41) is in the expanded state, the diameter of the deformable microsphere (41) is d3, which satisfies: 6μm≤d3≤20μm.

7. The electrode core according to claim 5, characterized in that, When the deformable microspheres (41) are in the initial state, the thickness of the coating (4) is d4, which satisfies: 3μm≤d4≤7μm.

8. The electrode core according to any one of claims 1-4, characterized in that, The deformable microspheres (41) include at least one of polyvinyl alcohol microspheres, polystyrene microspheres, or polyacrylate microspheres.

9. A battery cell, characterized in that, include: The electrode core as described in any one of claims 1-8.

10. An electrical appliance, characterized in that, include: The electrode core as described in any one of claims 1-8; or, including the battery cell as described in claim 9.

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