Secondary battery, heat insulation pad and electrical apparatus

Abstract

The present application relates to a secondary battery, a heat insulation pad and an electrical apparatus. The secondary battery comprises battery cells and a heat insulation pad arranged adjacent to the battery cells. The heat insulation pad comprises a heat insulation base substrate and a filler, the filler being arranged inside the heat insulation base substrate and / or on at least part of the surface of the heat insulation base substrate, and the filler comprising heat absorption microcapsules.

Description

Secondary batteries, heat insulation pads, and electrical appliances Cross-references

[0001] This application claims priority to Chinese Patent Application No. 202411545587.4, filed on October 31, 2024, entitled “Secondary Battery, Thermal Insulation Pad and Electrical Device”, which is incorporated herein by reference in its entirety. Technical Field

[0002] This application relates to the field of battery technology, and in particular to a secondary battery, a heat insulation pad, and an electrical device. Background Technology

[0003] In recent years, with the increasingly wide application of secondary batteries, they have been widely used in energy storage power systems such as hydropower, thermal power, wind power, and solar power plants, as well as in power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace, and many other fields. Due to the significant development of secondary batteries, thermal runaway has become a key technical concern, and therefore, how to prevent or delay thermal runaway is an urgent technical problem to be solved. Summary of the Invention

[0004] This application provides a secondary battery, a heat insulation pad, and an electrical device that can prevent or delay the thermal runaway problem of secondary batteries.

[0005] To achieve the above objectives, a first aspect of this application provides a secondary battery, including a battery cell and a heat insulation pad disposed adjacent to the sidewall of the battery cell.

[0006] The heat insulation pad includes a heat insulation substrate and a filler, the filler being disposed inside the heat insulation substrate and / or at least a portion of the surface of the heat insulation substrate, the filler including heat-absorbing microcapsules.

[0007] In some embodiments of this application, the number of battery cells is at least two, and the heat insulation pad is provided between the sidewalls of two adjacent battery cells.

[0008] In the secondary battery of this application, the heat insulation pad is disposed adjacent to the side wall of the battery cell. When the battery cell experiences thermal runaway, the heat-absorbing microcapsules in the heat insulation pad can effectively absorb the heat generated by the thermal runaway, reduce heat release, inhibit the continued occurrence of thermal runaway in the battery cell, and reduce the thermal runaway problem of the battery.

[0009] In some embodiments of this application, the interior of the thermal insulation substrate contains a porous structure, and the filler is disposed in the porous structure.

[0010] In some embodiments of this application, the porous structure includes a plurality of pores, the pore diameter of which is larger than the particle size of the heat-absorbing microcapsules.

[0011] In some embodiments of this application, the heat-absorbing microcapsule includes a core and a wall covering the core, the core comprising a core material and the wall comprising a wall material, wherein the boiling point of the core material is lower than the melting point of the wall material.

[0012] In some embodiments of this application, the boiling point of the core material is less than or equal to 80 degrees Celsius (°C), and the melting point of the wall material is 90°C to 160°C.

[0013] In some embodiments of this application, the heat-absorbing microcapsules satisfy one or more of the following conditions:

[0014] (1) The core material includes one or more of perfluorohexanone, fluoroalkyl compounds and halon compounds;

[0015] (2) The wall material includes one or more of microcrystalline wax, polyolefin compounds and their derivatives and polyacrylate compounds;

[0016] (3) The core of the capsule accounts for 60% to 80% of the mass of the heat-absorbing microcapsule.

[0017] In some embodiments of this application, the heat-absorbing microcapsules satisfy one or more of the following conditions:

[0018] (1) The core material includes one or more of perfluorohexanone, heptafluoropropane, hexafluoropropane and bromotrifluoromethane;

[0019] (2) The wall material includes one or more of microcrystalline wax, oxidized polyethylene, oxidized polypropylene and polymethyl methacrylate;

[0020] (3) The core of the capsule accounts for 65% to 75% of the mass of the heat-absorbing microcapsule.

[0021] In some embodiments of this application, the volume average particle size Dv50 of the heat-absorbing microcapsules is 100 micrometers (μm) to 500 μm.

[0022] In some embodiments of this application, the filler is provided both inside the heat insulation substrate and on the surface of the heat insulation substrate, and the filler forms a filler layer on the surface of the heat insulation substrate.

[0023] In some embodiments of this application, the thickness of the filler layer is 0.5 mm to 1.5 mm.

[0024] In some embodiments of this application, the weight ratio of the filler to the heat insulation substrate is (0.1 to 0.5):1.

[0025] In some embodiments of this application, the weight ratio of the filler to the heat insulation substrate is (0.2 to 0.3):1.

[0026] In some embodiments of this application, the filler further includes a binder, which is mixed with the heat-absorbing microcapsules.

[0027] In some embodiments of this application, the mass ratio of the heat-absorbing microcapsules to the binder in the filler is (50-70):(30-50).

[0028] In some embodiments of this application, the material of the thermal insulation substrate includes one or more of ceramics, aerogels, silicone, and glass fibers.

[0029] In some embodiments of this application, the thermal conductivity of the heat insulation pad is 0.01 watts / (meter·K) to 0.1 W / (m·K).

[0030] In some embodiments of this application, the thermal conductivity of the heat insulation pad is 0.01 W / m·K to 0.03 W / m·K.

[0031] A second aspect of this application also provides a heat insulation pad, comprising a heat insulation substrate and a filler, the filler being disposed inside the heat insulation substrate and / or at least a portion of the surface of the heat insulation substrate, the filler comprising heat-absorbing microcapsules.

[0032] In some embodiments of this application, the heat insulation pad is the heat insulation pad in the secondary battery described in the first aspect of this application.

[0033] A third aspect of this application provides an electrical device including a secondary battery as described in the first aspect of this application.

[0034] The electrical device of this application includes the secondary battery provided in this application, and therefore has at least the same advantages as the secondary battery.

[0035] Details of one or more embodiments of this application are set forth in the following drawings and description. Other features, objects, and advantages of this application will become apparent from the specification, drawings, and claims. Attached Figure Description

[0036] To better describe and illustrate the embodiments or examples provided in this application, reference may be made to one or more accompanying drawings. Additional details or examples used to describe the drawings should not be considered as limiting the scope of any of the disclosed applications, the currently described embodiments or examples, or the best mode of these applications as currently understood. Furthermore, throughout the drawings, the same reference numerals denote the same pads. In the drawings:

[0037] Figure 1 is a schematic diagram of a secondary battery according to an embodiment of this application.

[0038] Figure 2 is a schematic diagram of a battery cell according to one embodiment of this application.

[0039] Figure 3 is an exploded view of a battery cell according to an embodiment of this application shown in Figure 2.

[0040] Figure 4 is a schematic diagram of a battery device according to an embodiment of this application.

[0041] Figure 5 is a schematic diagram of a battery pack according to one embodiment of this application.

[0042] Figure 6 is an exploded view of the battery pack of one embodiment of this application shown in Figure 5.

[0043] Figure 7 is a schematic diagram of an electrical device using a secondary battery as a power source according to an embodiment of this application.

[0044] Explanation of reference numerals in the attached figures:

[0045] 1 Battery pack; 2 Upper casing; 3 Lower casing; 4 Battery assembly; 5 Battery cell; 51 Housing; 52 Electrode assembly; 53 Cover plate; 6 Electrical device; 8 Heat insulation pad. Detailed Implementation

[0046] Hereinafter, some embodiments of this application are described in detail with appropriate reference to the accompanying drawings. However, some unnecessary details may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of actually identical structures may be omitted. This is to avoid making the following description unnecessarily lengthy and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0047] The "range" disclosed in this application can be defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints; any endpoint can be independently included or excluded, and they can be combined arbitrarily, meaning any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​1 and 2 are listed, and maximum range values ​​3, 4, and 5 are also listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0" and "5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when describing a parameter as an integer ≥ 2, it is equivalent to listing integers such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, and 12 for that parameter. For instance, when describing a parameter as an integer selected from "2-10", it is equivalent to listing the integers 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0048] In this application, the terms "multiple" or "various" are used unless otherwise specified, referring to a quantity greater than or equal to 2. For example, "one or more" means one or more types.

[0049] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0050] 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 or implementation 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. The term "implementation" as used herein has a similar understanding.

[0051] Those skilled in the art will understand that the order in which the steps are written in the methods of various embodiments or examples does not imply a strict execution order and does not constitute any limitation on the implementation process. The detailed execution order of each step should be determined by its function and possible internal logic. Unless otherwise specified, all steps of this application may be performed sequentially or randomly, preferably sequentially. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, if the method may also include step (c), it means that step (c) can be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0052] In this application, "optionally," "optionally," and "optional" mean that something is optional, that is, it means that it is selected from either "with" or "without." If there are multiple "optional" entries in a technical solution, unless otherwise specified and there are no contradictions or mutual constraints, each "optional" entry shall be independent.

[0053] Currently, in lithium-ion batteries, as the energy density of a single cell increases, the heat generated during thermal runaway also increases. Heat diffusion occurs between adjacent cells, spreading from the cell experiencing thermal runaway to its neighbors, potentially leading to a chain reaction and increasing the risk of fire and explosion. To address this problem, inventors conceived of placing ceramic heat-insulating pads between adjacent cells. These pads would provide insulation, preventing heat transfer from one cell to its neighbors and thus avoiding fire and explosion. However, the thermal conductivity of ceramic heat-insulating pads is not low enough, requiring sufficient thickness between adjacent cells to effectively prevent heat diffusion. Furthermore, thicker pads would occupy battery space, potentially reducing the battery's energy density.

[0054] To address the aforementioned technical problems, this application provides a secondary battery in which a heat-insulating pad comprising heat-absorbing microcapsules is disposed adjacent to a battery cell (i.e., a battery cell). When a battery cell experiences thermal runaway, the heat-insulating pad effectively prevents heat diffusion to adjacent battery cells. This allows thermal runaway to be contained within a single battery cell, reducing the likelihood of a chain reaction of thermal runaway between cells and making the battery less prone to fire or explosion, thus solving the problem of battery thermal runaway. The secondary battery will be described in detail below.

[0055] In a first aspect, this application provides a secondary battery, as shown in FIG1, which includes a battery cell 5 and a heat insulation pad 8 disposed adjacent to the sidewall of the battery cell 5.

[0056] The heat insulation pad includes a heat insulation substrate and a filler, the filler being disposed inside the heat insulation substrate and / or at least a portion of the surface of the heat insulation substrate, the filler including heat-absorbing microcapsules.

[0057] The secondary battery of this application has a heat-insulating pad disposed adjacent to the sidewall of the battery cell. When thermal runaway occurs in the battery cell, the heat-absorbing microcapsules in the heat-insulating pad can effectively absorb the heat generated by the thermal runaway, reduce heat release, and inhibit the continued occurrence of thermal runaway in the battery cell, thus reducing the thermal runaway problem. At the same time, the heat-absorbing microcapsules can also work in conjunction with the heat-insulating substrate to effectively prevent the thermal runaway battery cell from diffusing heat to adjacent battery cells. In this way, the thermal runaway can be controlled within a single battery cell, reducing the chain reaction of thermal runaway between battery cells, making the battery less prone to fire and explosion, and reducing the thermal runaway problem. Moreover, the heat-absorbing microcapsules in the heat-insulating pad can effectively improve its thermal conductivity, so that even with a relatively small thickness, the heat-insulating pad can still have a low thermal conductivity, thus reducing its space occupation in the battery and allowing the battery to still have a relatively high energy density.

[0058] It is understood that the thickness of the heat insulation pad described in this application refers to the thickness of the heat insulation pad along the arrangement direction of two adjacent battery cells (as shown in the "x" direction in Figure 1).

[0059] It is understood that in the secondary battery of this application, the number of battery cells can be one or more; when the number of battery cells is one, the heat insulation pad can be disposed at an adjacent position to one or more sidewalls of the single battery cell; when there are multiple battery cells, the heat insulation pad can be disposed between the sidewalls of two adjacent battery cells.

[0060] It is understood that the “surface of the thermal insulation substrate” described in this application includes the following situations: (1) the thermal insulation substrate is a single layer, in which case the surface of the thermal insulation substrate refers to all surfaces of the thermal insulation substrate that are directly exposed to the environment; (2) the thermal insulation substrate is multi-layered, and at least two layers are in contact with each other, in which case the surface of the thermal insulation substrate includes all surfaces of the thermal insulation substrate that are directly exposed to the environment, as well as the surfaces in contact between the layers of the thermal insulation substrate; all of the above situations fall within the scope of the “surface of the thermal insulation substrate” described in this application.

[0061] As an example, the method for extracting heat-absorbing microcapsule samples from the heat insulation pad of this application is as follows: the heat insulation pad is fully soaked in an organic solvent (such as dimethyl carbonate) for a certain period of time (such as 2 hours (h) to 10 hours) to dissolve the adhesive and allow the heat-absorbing microcapsules to be released from the heat insulation pad and dispersed in the solvent in the form of particles; the released heat-absorbing microcapsules are separated from the solvent, washed, and dried to obtain heat-absorbing microcapsule samples for subsequent testing.

[0062] As an example, the test method for determining whether a heat insulation pad contains heat-absorbing microcapsules is as follows: Perform a combustion test on the heat insulation pad and observe whether it has a fire extinguishing effect to determine whether the heat insulation pad can absorb heat; at the same time, as described above, soak the heat insulation pad in an organic solvent (such as dimethyl carbonate) for a certain period of time (such as 2h to 10h) to see if any particulate matter detaches and disperses in the solvent; then separate the particulate matter from the solvent and observe its morphology using a scanning electron microscope (SEM) to see if it is capsule-shaped; and use thermogravimetric analysis (TG) to observe whether there are two weight loss peaks in the capsule wall and capsule core to determine whether the particulate matter is in microcapsule form, and thus determine whether the heat insulation pad contains heat-absorbing microcapsules.

[0063] In some embodiments, the number of battery cells is at least two, and the heat insulation pad is provided between the sidewalls of two adjacent battery cells. Thus, the heat insulation pad can effectively isolate heat diffusion between two adjacent battery cells, thereby reducing the occurrence of a chain reaction of thermal runaway between battery cells, making the battery less prone to fire or explosion, and solving the problem of battery thermal runaway.

[0064] In some embodiments, the heat insulation pad is disposed between the larger sidewalls of two adjacent battery cells.

[0065] It is understandable that when a battery cell is square, it will include multiple sidewalls of equal or unequal area. Placing a heat insulation pad between the larger sidewalls of two adjacent battery cells can further effectively absorb the heat generated by thermal runaway, suppress the continued occurrence of thermal runaway of battery cells, and further effectively isolate the heat diffusion between battery cells.

[0066] In some embodiments, the thermal insulation substrate has a porous structure inside, and the filler is disposed within the porous structure. The porous structure can accommodate the filler and facilitates the release of the core material from the core of the heat-absorbing microcapsule.

[0067] In some embodiments, the porous structure includes multiple pores, the pore diameter of which is larger than the particle size of the heat-absorbing microcapsules. Thus, the porous structure of the thermal insulation substrate can accommodate the heat-absorbing microcapsules, enabling the thermal insulation substrate to serve as a carrier for the heat-absorbing microcapsules.

[0068] It is understood that the "particle size of the heat-absorbing microcapsules" mentioned in this application may refer to the volume average particle size Dv50 of the heat-absorbing microcapsules.

[0069] As an example, porous structures can be observed using a scanning electron microscope (SEM). For instance, the insulation pad can be cut open along its thickness to expose a cross-section. By observing the cross-section under an SEM, the pores of the porous structure and the heat-absorbing microcapsules filling the pores can be observed.

[0070] In some embodiments, the heat-absorbing microcapsule includes a core and a wall covering the core. The core comprises a core material, and the wall comprises a wall material. The boiling point of the core material is lower than the melting point of the wall material. This lower boiling point facilitates the rupture of the heat-absorbing microcapsule and release of the core in the event of thermal runaway in a single battery cell, while also ensuring that the core material can be vaporized to absorb the heat generated by the thermal runaway.

[0071] In some embodiments, the boiling point of the core material is less than or equal to 80°C, and the melting point of the wall material is 90°C to 160°C. For example, the boiling point of the core material can be 79°C, 71°C, 62°C, 53°C, 44°C, 35°C, 26°C, 17°C, 6°C, 0°C, -8°C, -19°C, -23°C, -34°C, -45°C, -56°C, -67°C, -70°C, or any range thereof. The melting point of the wall material can be 90°C, 93°C, 97°C, 100°C, 106°C, 110°C, 115°C, 120°C, 124°C, 130°C, 138°C, 140°C, 143°C, 150°C, 157°C, 160°C, or any range thereof.

[0072] The melting point of the wall material is within the above range, which ensures that the capsule wall can rupture and release the core when the battery cell experiences thermal runaway, so that the core can absorb heat. The boiling point of the core material is within the above range, which ensures that the core material can vaporize after the heat-absorbing microcapsule ruptures and releases the core, thereby absorbing the heat generated by thermal runaway.

[0073] As an example, the core and wall materials of endothermic microcapsules can be tested using the following method: by using Fourier transform infrared spectroscopy (FT-IR) coupled with thermogravimetric analysis (TGA) to test the endothermic microcapsules, the types of materials of the core and wall materials, as well as the mass ratio of the core and wall materials, can be determined.

[0074] In some embodiments, the core material includes one or more of perfluorohexanone, fluoroalkyl compounds, and halonides. These types of core materials vaporize at high temperatures, effectively absorbing the heat generated by the thermal runaway of individual battery cells, resulting in a low thermal conductivity for the insulation pad; they can also react with oxygen in the battery to generate inert gases, thereby reducing the oxygen concentration and lowering the probability of a thermal runaway battery ignition.

[0075] It should be noted that the "fluoroalkane compounds" mentioned in this application refer to fluorine-substituted hydrocarbon compounds, and these hydrocarbon compounds may optionally contain other halogen atoms besides fluorine atoms, such as chlorine atoms and bromine atoms; the "halon compounds" refer to halogen-substituted hydrocarbon compounds, where halogens include fluorine atoms, chlorine atoms and bromine atoms.

[0076] In some embodiments, the core material includes one or more of perfluorohexanone, heptafluoropropane, hexafluoropropane, and bromotrifluoromethane. These types of core materials can better absorb the heat generated by the thermal runaway of the battery cells, further reduce the thermal conductivity of the heat insulation pad, and further reduce the oxygen concentration in the battery.

[0077] In some embodiments, the wall material includes one or more of microcrystalline wax, polyolefin compounds and their derivatives, and polyacrylate compounds. These types of wall materials not only enable the capsule wall to rupture and release the core during thermal runaway of the battery cell, but also possess a certain degree of pressure resistance, reducing the possibility that the endothermic microcapsules will prematurely rupture and fail due to pressure before the battery cell experiences thermal runaway.

[0078] In some embodiments, the wall material comprises one or more of microcrystalline wax, oxidized polyethylene, oxidized polypropylene, and polymethyl methacrylate. These types of wall materials facilitate core release in the event of thermal runaway of the battery cell and exhibit better pressure resistance.

[0079] It should be noted that the "polyolefin compounds and their derivatives" mentioned in this application refer to polymeric compounds polymerized from olefin monomers, as well as new compounds obtained by chemical modification or introduction of other chemical groups from such polymeric compounds; wherein, "olefin monomers" refer to organic compounds containing carbon-carbon double bonds (*-C=C-*), including ethylene, propylene, butene, and styrene, etc.

[0080] It should be noted that the "polyacrylate compounds" mentioned in this application refer to polymeric compounds polymerized from acrylate monomers, wherein "acrylate monomers" refer to those containing acrylate functional groups. Organic compounds, including methyl methacrylate, methyl acrylate, ethyl acrylate and butyl acrylate.

[0081] In some embodiments, the core mass percentage of the heat-absorbing microcapsule is 60% to 80%. For example, the core mass percentage of the heat-absorbing microcapsule can be 60%, 62%, 64%, 66%, 68%, 70%, 71%, 73%, 75%, 77%, 79%, 80%, or within any range of the above values; alternatively, the core mass percentage of the heat-absorbing microcapsule is 70% to 80%. This is beneficial for further improving the heat absorption performance of the heat insulation pad and further reducing the thermal conductivity of the heat insulation pad.

[0082] As an example, the mass percentage of the core material in the heat-absorbing microcapsule can be tested using the following method: by using Fourier transform infrared spectroscopy (FT-IR) coupled with thermogravimetric analysis (TGA) to test the heat-absorbing microcapsule, the types of core and wall materials can be determined, as well as the mass percentage of the core material in the heat-absorbing microcapsule.

[0083] In some embodiments, the volume average particle size Dv50 of the heat-absorbing microcapsules is 100 μm to 500 μm. For example, the volume average particle size Dv50 of the heat-absorbing microcapsules can be 100 μm, 150 μm, 200 μm, 250 μm, 300 μm, 350 μm, 400 μm, 450 μm, 500 μm, or within any range of the above values. This allows the heat-absorbing microcapsules to accommodate a larger amount of core material, resulting in a higher core material capacity and enabling them to absorb sufficient heat. Furthermore, it allows the heat-absorbing microcapsules to be better supported by the thermal insulation substrate, enabling the thermal insulation substrate to support a sufficient number of heat-absorbing microcapsules and giving the thermal insulation pad high heat absorption performance.

[0084] The volume average particle size (Dv50) of endothermic microcapsules is a well-known concept in the art and can be determined using instruments and methods known in the art. For example, particle size distribution-laser diffraction can be used, referring to GB / T19077-2016 Particle Size Distribution Laser Diffraction Method. A specific example is as follows: Endothermic microcapsule sample particles can be dispersed at an appropriate concentration in a suitable liquid (e.g., deionized water) or gas through ultrasonic treatment or other methods. The sample is then tested using a Malvern Mastersizer-3000 instrument. The sample is passed through a monochromatic beam (usually a laser). When the light encounters the particles, it scatters at different angles. The scattered light is measured by a multi-element detector, and these values ​​related to the scattering pattern are stored for subsequent analysis. Through appropriate optical models and mathematical processes, these quantified scattering data are converted to obtain a series of discrete particle size ranges representing the percentage of particle volume relative to the total particle volume, thus yielding the volume distribution of the particle size.

[0085] In some embodiments, the filler is provided both in the porous structure of the thermal insulation substrate and on the surface of the thermal insulation substrate, and the filler forms a filler layer on the surface of the thermal insulation substrate. Thus, the thermal insulation pad has better heat absorption performance, can further reduce its thermal conductivity, and can also further reduce the oxygen concentration in a thermally runaway battery.

[0086] In some embodiments, the thickness of the filler layer is 0.5 mm to 1.5 mm. For example, the thickness of the filler layer can be 0.5 mm, 0.7 mm, 0.9 mm, 1 mm, 1.1 mm, 1.3 mm, 1.5 mm, or within any range of the above values. This reduces both the thermal conductivity of the heat insulation pad and the increase in its thickness, minimizing the space occupied by the increased thickness on the battery and enabling the battery to achieve a higher energy density.

[0087] As an example, the thickness of the filler layer can be tested using a micrometer (such as the MDH-25MB).

[0088] In some embodiments, the weight ratio of the filler to the thermal insulation substrate is (0.1 to 0.5):1. For example, the weight ratio of the filler to the thermal insulation substrate can be 0.1:1, 0.2:1, 0.3:1, 0.4:1, 0.5:1, or within any range of the above values; optionally, the weight ratio of the filler to the thermal insulation substrate is (0.2 to 0.3):1. Adjusting the weight ratio of the filler to the thermal insulation substrate is equivalent to adjusting the loading of heat-absorbing microcapsules on the thermal insulation substrate; when the loading of heat-absorbing microcapsules on the thermal insulation substrate is within a suitable range, the thermal insulation substrate can load a sufficient number of heat-absorbing microcapsules to achieve a better heat absorption and insulation effect.

[0089] As an example, the weight ratio of filler to thermal insulation substrate can be tested using the following method: The weight of the thermal insulation pad is recorded as w1. As mentioned above, the thermal insulation pad is fully immersed in an organic solvent (such as dimethyl carbonate) for a certain period of time (such as 2h to 10h) to dissolve the adhesive and allow the heat-absorbing microcapsules to detach from the thermal insulation pad and disperse in the solvent in the form of particles. Then, the thermal insulation pad with the heat-absorbing microcapsules detached is taken out, cleaned, and dried, and its weight is recorded as w2. The weight ratio of filler to thermal insulation substrate can then be recorded as (w1-w2):w2.

[0090] In some embodiments, the filler further includes a binder, which is mixed with the heat-absorbing microcapsules.

[0091] In some embodiments, the mass ratio of the heat-absorbing microcapsules to the binder in the filler is (50-70):(30-50). For example, the mass ratio of the heat-absorbing microcapsules to the binder can be 50:50, 50:40, 50:30, 70:50, 70:40, 70:30, or within any range of these values. This balances the load capacity of the heat-absorbing microcapsules in the insulation pad with the stability of their load within the pad.

[0092] As an example, the mass ratio of heat-absorbing microcapsules to binder in the filler can be tested using the following method: The mass of the heat insulation pad is recorded as w1. As mentioned earlier, the heat insulation pad is thoroughly soaked in an organic solvent (such as dimethyl carbonate) for a certain period of time (e.g., 2h to 10h) to dissolve the binder and allow the heat-absorbing microcapsules to detach from the heat insulation pad and disperse in the solvent as particles. Then, the heat insulation pad with the detached heat-absorbing microcapsules is removed, cleaned, and dried, and its mass is recorded as w2. The mass of the filler can then be recorded as (w1-w2). The detached heat-absorbing microcapsules are separated from the solvent, cleaned, and dried, and their mass is recorded as w3. The mass ratio of heat-absorbing microcapsules to binder in the filler can then be recorded as w3:(w1-w2-w3).

[0093] In some embodiments, the material of the thermal insulation substrate includes one or more of ceramic (i.e., ceramic thermal insulation pad), aerogel (i.e., aerogel thermal insulation pad), silicone (i.e., silicone thermal insulation pad), and glass fiber (i.e., glass fiber thermal insulation pad), and may be selected as one or both of ceramic and aerogel.

[0094] When the heat insulation substrate includes the above-mentioned materials, the heat insulation substrate itself already has a certain heat insulation performance. It can work with the heat-absorbing microcapsules to make the heat insulation pad have a low thermal conductivity. Moreover, compared with the heat insulation substrate materials including polymers, the above-mentioned heat insulation substrates are not easy to melt and burn at the thermal runaway temperature. After the heat-absorbing microcapsules are ruptured and consumed, they can still maintain the relative integrity of the heat insulation pad structure and still have a certain heat insulation performance.

[0095] It should be noted that the aforementioned "polymer" may include one or more of polyethylene terephthalate (PET), polyvinylidene fluoride (PVDF), polyethylene terephthalate (PBT), polyethylene (PE), and polypropylene (PP).

[0096] In some embodiments, the ceramic comprises ceramic fibers. The thermal insulation substrate comprising ceramic fibers has a more porous structure, which can accommodate more heat-absorbing microcapsules, enabling the thermal insulation pad to have good heat absorption performance even when the thickness is not high. This reduces the space occupied by the thermal insulation pad in the battery and minimizes the decrease in energy density.

[0097] In some embodiments, the thermal insulation substrate includes thermal insulation layers, which may be a single-layer thermal insulation layer or a multi-layer thermal insulation layer stacked together. The material of each thermal insulation layer may independently include one or more of ceramic, aerogel, silicone, and glass fiber; ceramic or aerogel may be selected.

[0098] In some embodiments, the heat insulation substrate includes a heat insulation layer and a heat dissipation layer stacked together; the material of the heat insulation layer may include one or more of ceramics, aerogels, silicone rubber and glass fibers, and the material of the heat dissipation layer may include one or more of metallic materials and carbon materials.

[0099] It should be noted that the thermal insulation substrate of this application does not exclude the possibility of the thermal insulation layer and heat dissipation layer being set in other ways, and all thermal insulation substrates containing thermal insulation layers and heat dissipation layers are within the protection scope of the thermal insulation substrate described in this application.

[0100] In some embodiments, the adhesive comprises at least one of polyurethane, polyethylene oxide, styrene-butadiene rubber, polyacrylic acid, gelatin, chitosan, sodium alginate, sodium carboxymethyl cellulose, polymeric cyclic ether derivatives, and cyclodextrin.

[0101] It is understood that this application does not limit the size and shape of the heat insulation pad. The size and shape of the heat insulation pad can be adapted to meet actual usage requirements, such as the size and shape of the battery cell, so as to achieve a better structural match with the battery cell and exert better heat absorption and insulation performance.

[0102] In some embodiments, the height of the thermal insulation pad is equal to the height of the battery cell along the height direction. This further reduces heat transfer from the thermally runaway battery cell to adjacent battery cells, reduces the likelihood of a chain reaction of thermal runaway between battery cells, makes the battery less prone to fire or explosion, and solves the problem of battery thermal runaway.

[0103] In some embodiments, the thermal conductivity of the heat insulation pad is 0.01 W / (m·K) to 0.1 W / (m·K). For example, the thermal conductivity of the heat insulation pad can be 0.01 W / (m·K), 0.02 W / (m·K), 0.03 W / (m·K), 0.04 W / (m·K), 0.05 W / (m·K), 0.06 W / (m·K), 0.07 W / (m·K), 0.08 W / (m·K), 0.09 W / (m·K), 0.1 W / (m·K), or within any range of the above values; it can be selected as 0.01 W / (m·K) to 0.03 W / (m·K). The low thermal conductivity of the heat insulation pad is beneficial for blocking heat transfer between battery cells at a thinner thickness, reducing the occurrence of battery thermal runaway problems, while also enabling the battery to have a higher energy density.

[0104] Secondly, this application provides a heat insulation pad, including a heat insulation substrate and a filler, wherein the filler is disposed inside the heat insulation substrate and / or at least a portion of the surface of the heat insulation substrate, and the filler includes heat-absorbing microcapsules.

[0105] In some embodiments, the heat insulation pad is the heat insulation pad in the secondary battery described in the first aspect of this application.

[0106] The heat insulation pad of the second aspect of this application plays the same or similar role as the secondary battery of the first aspect, and will not be described in detail here.

[0107] Thirdly, this application provides a method for preparing a heat insulation pad, which can be used to prepare the heat insulation pad of the second aspect of this application, and may include the following steps:

[0108] A slurry containing filler is introduced into the interior of a thermal insulation substrate and / or applied to at least a portion of the surface of the thermal insulation substrate, and dried to form a thermal insulation pad, wherein the filler comprises heat-absorbing microcapsules.

[0109] In some embodiments, a filler may be formed on the interior and / or part of the surface of the thermal insulation substrate by spraying or dipping. For example, the thermal insulation substrate may be immersed in a slurry containing a filler, allowing the slurry to penetrate the interior of the thermal insulation substrate and / or be applied to at least part of the surface of the thermal insulation substrate.

[0110] In some embodiments, the viscosity of the slurry is between 200 mPa·s and 3000 mPa·s. For example, the viscosity of the slurry can be 200 mPa·s, 500 mPa·s, 800 mPa·s, 1000 mPa·s, 1500 mPa·s, 2000 mPa·s, 2500 mPa·s, 3000 mPa·s, or within any range of the above values.

[0111] In some embodiments, the filler further includes a binder, and the mass ratio of the heat-absorbing microcapsule to the binder is (50-70):(30-50).

[0112] It is understandable that, in the above preparation process, by adjusting one or more conditions such as the spraying or dipping time and the viscosity of the slurry, the weight ratio of the filler to the heat insulation substrate and the thickness of the filler layer in the heat insulation pad can be controlled.

[0113] It should be noted that the drying temperature is lower than the melting point of the wall material of the heat-absorbing microcapsule and lower than the boiling point of the core material.

[0114] In addition, the battery cell, secondary battery and power device of this application will be described below with appropriate reference to the accompanying drawings.

[0115] Typically, a battery cell includes a positive electrode, a negative electrode, an electrolyte, and a separator. During charging and discharging, active ions move back and forth between the positive and negative electrodes, inserting and releasing. The electrolyte acts as a conductor of ions between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, primarily prevents short circuits while allowing ions to pass through.

[0116] Positive electrode sheet

[0117] The positive electrode sheet includes a positive current collector and a positive active material layer disposed on at least one surface of the positive current collector, the positive active material layer including a positive active material.

[0118] As a non-limiting example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive active material layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0119] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymeric material substrate and a metal layer formed on at least one surface of the polymeric material substrate. The composite current collector can be obtained by forming a metal material on a polymeric material substrate. Non-limiting examples of the metal material in the positive electrode current collector may include one or more of aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. Non-limiting examples of the polymeric material substrate in the positive electrode current collector may include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0120] In some embodiments, the positive electrode active material may be a known positive electrode active material for batteries. As a non-limiting example, the positive electrode active material may include one or more of the following materials: lithium-containing phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, this application is not limited to these materials, and other conventional materials that can be used as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides include, but are not limited to, one or more of lithium cobalt oxides (such as LiCoO2), lithium nickel oxides, lithium manganese oxides, lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, lithium nickel cobalt manganese oxides, lithium nickel cobalt aluminum oxides, and their modified compounds. Non-limiting examples of lithium-containing phosphates with an olivine structure include, but are not limited to, one or more of lithium iron phosphate, lithium iron phosphate and carbon composites, lithium manganese phosphate, lithium manganese phosphate and carbon composites, lithium iron manganese phosphate, and lithium manganese iron phosphate and carbon composites. Non-limiting examples of lithium cobalt oxides may include LiCoO2; non-limiting examples of lithium nickel oxides may include LiNiO2; non-limiting examples of lithium manganese oxides may include LiMnO2, LiMn2O4, etc.; non-limiting examples of lithium nickel cobalt manganese oxides may include LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also known as NCM) 333 LiNi 0.5 Co 0.2 Mn 0.3 O2 (also known as NCM) 523 LiNi 0.5 Co 0.25 Mn 0.25 O2 (also known as NCM) 211 LiNi 0.6 Co 0.2 Mn 0.2 O2 (also known as NCM) 622 LiNi 0.8 Co 0.1 Mn 0.1 O2 (also known as NCM) 811 Examples of lithium nickel cobalt aluminum oxides include LiNi, etc. 0.8 Co 0.15 Al 0.05 O2.

[0121] Understandably, lithium (Li) is intercalated and deintercalated during the charging and discharging process of a battery, and the Li content in the positive electrode varies depending on the state of discharge. Unless otherwise specified, the Li content in the examples of positive electrode materials listed in this application refers to the initial state of the material. When a positive electrode material is applied to a positive electrode in a battery system, the Li content in the positive electrode material typically changes after charge-discharge cycles. The Li content can be measured using molar content, but is not limited to this. Regarding "Li content refers to the initial state of the material," the initial state of the material refers to its state before being added to the positive electrode slurry. It is understood that new materials obtained by appropriately modifying the listed positive electrode materials are also within the scope of positive electrode materials. The aforementioned appropriate modification refers to acceptable modification methods for the positive electrode material; non-limiting examples include coating modification.

[0122] In the examples of cathode materials in this application, the oxygen (O) content is only a theoretical value. Lattice oxygen release will cause changes in the molar content of oxygen, and the actual O content will fluctuate. The O content can be measured in molar content, but is not limited to this.

[0123] In some embodiments, the positive electrode active material may also include at least one of the following materials: sodium transition metal oxides, polyanionic compounds, and Prussian blue compounds. However, this application is not limited to these materials, and other conventionally known materials that can be used as positive electrode active materials for sodium-ion batteries may also be used.

[0124] As an optional technical solution in this application, the transition metal in the sodium transition metal oxide may include one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce. A non-limiting example of a sodium transition metal oxide is Na. x MO2, where M can include one or more of Ti, V, Mn, Co, Ni, Fe, Cr and Cu, and 0 < x ≤ 1.

[0125] As an optional technical solution in this application, the polyanionic compound can be a compound containing sodium ions, transition metal ions, or a tetrahedral (YO4) structure. n- A class of compounds with anionic units. Transition metals may include one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; Y may be one or more of P, S, and Si; n represents (YO4). n- The price state.

[0126] Polyanionic compounds can also contain sodium ions, transition metal ions, or tetrahedral (YO4) ions. n-A class of compounds consisting of anionic units and halide anions. Transition metals may include one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; Y may be one or more of P, S, and Si, and n represents (YO4). n- The valence state; halogens can be one or more of F, Cl and Br.

[0127] Polyanionic compounds can also be sodium-containing tetrahedral (YO4) compounds. n- Anionic unit, polyhedral unit (ZO) y ) m+ And a class of compounds with optional halide anions. Y can be one or more of P, S, and Si, and n represents (YO4). n - represents the valence state; Z represents a transition metal, which can include one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; m represents (ZO) y ) m+ The valence state; halogens can be one or more of F, Cl and Br.

[0128] Polyanionic compounds can include NaFePO4, Na3V2(PO4)3 (sodium vanadium phosphate, abbreviated as NVP), Na4Fe3(PO4)2 (P2O7), NaM'PO4F and Na3(VO y )2(PO4)2F 3-2y One or more of (0≤y≤1). Among them, M' in NaM'PO4F can include one or more of V, Fe, Mn and Ni.

[0129] Prussian blue compounds can be compounds containing sodium ions, transition metal ions, and cyanide ions (CN). - A class of compounds containing Prussian blue. Transition metals may include one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce. A non-limiting example of Prussian blue compounds is Na. a Me b Me' c (CN)6, wherein Me and Me' can each be one or more of Ni, Cu, Fe, Mn, Co and Zn, 0 < a ≤ 2, 0 < b < 1, 0 < c < 1.

[0130] In some embodiments, the positive electrode active material layer may optionally include a binder. As a non-limiting example, the binder may include one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resins.

[0131] In some embodiments, the positive electrode active material layer may optionally include a conductive agent. As a non-limiting example, the conductive agent may include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0132] In some embodiments, the positive electrode sheet can be prepared by dispersing the components used to prepare the positive electrode sheet, such as the positive active material, conductive agent, binder, and any other components, in a solvent to form a positive electrode slurry; coating the positive electrode slurry onto at least one surface of the positive electrode current collector, and obtaining the positive electrode sheet after drying, cold pressing, and other processes. The solvent can be selected from, but is not limited to, any of the solvents described in the foregoing embodiments, such as N-methylpyrrolidone (NMP). The surface of the positive electrode current collector coated with the positive electrode slurry can be a single surface of the positive electrode current collector or both surfaces of the positive electrode current collector. The solid content of the positive electrode slurry can be 40 wt% to 80 wt%. The viscosity of the positive electrode slurry at room temperature can be adjusted to 5000 to 25000 mPa·s. When coating the positive electrode slurry, the surface density of the coating on one side (excluding solvent) can be 15 to 35 mg / cm² (mg / cm³). 2 The compaction density of the positive electrode sheet can be 3.0–3.6 g / cm³. 3 The concentration can be selected as 3.3–3.5 g / cm³. 3 .

[0133] Negative electrode sheet

[0134] The negative electrode sheet includes a negative current collector and a negative active material layer disposed on at least one surface of the negative current collector, wherein the negative active material layer includes a negative active material.

[0135] As a non-limiting example, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode active material layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0136] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymeric material substrate and a metal layer formed on at least one surface of the polymeric material substrate. The composite current collector can be obtained by forming a metal material on the polymeric material substrate. Non-limiting examples of the metal material in the negative electrode current collector may include one or more of copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. Non-limiting examples of the polymeric material substrate in the negative electrode current collector may include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0137] In some embodiments, the negative electrode active material may be a negative electrode active material known in the art for use in batteries. As a non-limiting example, the negative electrode active material may include one or more of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc. Silicon-based materials may include one or more of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials may include one or more of elemental tin, tin oxide compounds, and tin alloys. However, this application is not limited to these materials, and other conventional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0138] In some embodiments, the negative electrode active material layer may optionally include a binder. The binder may include one or more of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0139] In some embodiments, the negative electrode active material layer may optionally include a conductive agent. The conductive agent may include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0140] In some embodiments, the negative electrode active material layer may also optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0141] In some embodiments, the negative electrode sheet can be prepared by dispersing the components used to prepare the negative electrode sheet, such as the negative electrode active material, conductive agent, binder, and any other components, in a solvent (a non-limiting example of a solvent is deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto at least one surface of the negative electrode current collector, and then obtaining the negative electrode sheet after drying, cold pressing, and other processes. The surface of the negative electrode current collector coated with the negative electrode slurry can be a single surface of the negative electrode current collector or both surfaces of the negative electrode current collector. The solid content of the negative electrode slurry can be 40wt% to 60wt%. The viscosity of the negative electrode slurry at room temperature can be adjusted to 2000 to 10000 mPa·s. When coating the negative electrode slurry, the surface density of the coating on one side (dry weight, minus solvent) can be 75 to 220 g / m². 2 The compaction density of the negative electrode sheet can be 1.0 g / cm³. 3 ~1.8g / cm 3 .

[0142] electrolytes

[0143] Electrolytes function to conduct ions between the positive and negative electrode plates. This application does not impose any particular restrictions on the type of electrolyte; it can be selected according to requirements. For example, the electrolyte can be liquid, gel, or completely solid.

[0144] In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0145] In some embodiments, the electrolyte salt may include one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorophosphate (LiPO2F2), lithium difluorooxalate borate (LiDFOB), lithium dioxalate borate (LiBOB), lithium difluorodioxalate phosphate (LiDFOP), and lithium tetrafluorooxalate phosphate (LiTFOP).

[0146] In some embodiments, the solvent may include one or more of ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butenyl carbonate, fluoroethylene carbonate (FEC), methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0147] In some embodiments, the electrolyte may optionally include additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.

[0148] In some embodiments, the additives in the electrolyte may include, but are not limited to, one or more of fluoroethylene carbonate (FEC), difluoroethylene carbonate (DFEC), trifluoromethyl ethylene carbonate (TFPC), etc.

[0149] Separating membrane

[0150] In some embodiments, the secondary battery also includes a separator. This application does not impose any particular limitation on the type of separator; any known porous separator with good chemical and mechanical stability can be selected.

[0151] In some embodiments, the material of the separator may include one or more of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer may be the same or different, without particular limitation.

[0152] In some embodiments, the thickness of the isolation membrane is 6 μm to 40 μm, and optionally 12 μm to 20 μm.

[0153] In some embodiments, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding process or a stacking process.

[0154] In some embodiments, the battery cell may include an outer packaging. This outer packaging can be used to encapsulate the electrode assembly and electrolyte described above.

[0155] In some embodiments, the outer packaging of the battery cell can be a rigid shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer packaging of the battery cell can also be a flexible package, such as a pouch-type flexible package. The material of the flexible package can be plastic; further, non-limiting examples of plastic may include one or more of polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0156] In this application, unless otherwise specified, "cell battery" refers to the basic unit capable of converting chemical energy into electrical energy, and generally includes at least a positive electrode, a negative electrode, and an electrolyte. During the charging and discharging process of the battery, active ions move back and forth between the positive and negative electrode plates, inserting and extracting. The electrolyte acts as a conductor for the active ions between the positive and negative electrode plates.

[0157] This application does not impose any particular limitation on the shape of the battery cell; it can be cylindrical, square, or any other arbitrary shape. For example, Figure 2 shows a square battery cell 5 as an example.

[0158] In some embodiments, referring to FIG3, the outer packaging may include a housing 51 and a cover plate 53. The housing 51 may include a base plate and side plates connected to the base plate, the base plate and side plates forming a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover plate 53 can be placed over the opening to close the receiving cavity. The positive electrode sheet, negative electrode sheet, and separator may be formed into an electrode assembly 52 by a winding process or a stacking process. The electrode assembly 52 is encapsulated within the receiving cavity. Electrolyte is immersed in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the battery cell 5 may be one or more, which can be selected by those skilled in the art according to actual needs.

[0159] In some embodiments, the secondary battery may be a battery device 4 or a battery pack 1.

[0160] The battery device includes at least two battery cells. The number of battery cells in the battery device can be two or more, and those skilled in the art can select an appropriate number according to the application and capacity of the battery device; and a heat insulation pad 8 can be provided between any two adjacent battery cells.

[0161] Figure 4 shows a battery device 4 as an example. Referring to Figure 4, in the battery device 4, multiple battery cells 5 can be arranged sequentially along the length of the battery device 4. Of course, they can also be arranged in any other arbitrary way. Furthermore, the multiple battery cells 5 can be fixed in place by fasteners.

[0162] Optionally, the battery device 4 may also include a housing with a receiving space in which multiple battery cells 5 are received.

[0163] In some embodiments, the battery devices described above can also be assembled into a battery pack, and the number of battery devices contained in the battery pack can be one or more. Those skilled in the art can select an appropriate number according to the application and capacity of the battery pack.

[0164] Figures 5 and 6 illustrate a battery pack 1 as an example. Referring to Figures 5 and 6, the battery pack 1 may include a battery compartment and multiple battery devices 4 disposed within the battery compartment. The battery compartment includes an upper compartment 2 and a lower compartment 3, with the upper compartment 2 covering the lower compartment 3 to form a closed space for accommodating the battery devices 4. The multiple battery devices 4 can be arranged in any manner within the battery compartment.

[0165] In addition, this application also provides an electrical device, which includes the secondary battery provided in this application. The secondary battery can be used as the power source of the electrical device or as the energy storage unit of the electrical device. The electrical device may include, but is not limited to, mobile devices, electric vehicles, electric trains, ships and satellites, energy storage systems, etc. Among them, mobile devices may be, for example, mobile phones, laptops, etc.; electric vehicles may be, for example, pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc., but are not limited to.

[0166] As an electrical device, a rechargeable battery can be selected based on its usage requirements.

[0167] Figure 7 shows an example of an electrical device 6. This electrical device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. To meet the high power and high energy density requirements of the secondary battery for this electrical device, a battery pack or battery device can be used.

[0168] Another example device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use a rechargeable battery as their power source.

[0169] Example

[0170] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where the technology or conditions are not specified in the embodiments, they are performed according to the technology or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0171] Example 1

[0172] (1) Heat insulation pad

[0173] Preparation of the slurry: The heat-absorbing microcapsules and the binder sodium carboxymethyl cellulose were dissolved in water at a mass ratio of 50:50 to form a slurry, and the viscosity of the slurry was controlled at 500 mPa·s. The core material of the heat-absorbing microcapsules was perfluorohexanone, and the wall material was oxidized polyethylene. The core material accounted for 60% of the total mass, and the volume average particle size (Dv50) of the heat-absorbing microcapsules was 200 μm.

[0174] Coating and drying: Immerse a ceramic heat insulation substrate with a thickness (which is the thickness along the "x" direction in Figure 1) of 4 mm into the above slurry and dip it for 30 seconds to allow the slurry to enter the porous structure of the ceramic heat insulation substrate and to coat the surface of the ceramic heat insulation substrate. Then dry it at 40°C for 24 hours to form a filler in the porous structure of the ceramic heat insulation substrate and form a filler layer on the surface of the substrate to obtain the heat insulation pad.

[0175] (2) Preparation of battery cells

[0176] Preparation of positive electrode sheet

[0177] Lithium iron phosphate (LiFePO4), conductive carbon black (SP), and PVDF binder were dispersed in NMP solvent at a weight ratio of 98:1:1 and mixed evenly to obtain a positive electrode slurry. The positive electrode slurry was then uniformly coated onto both sides of an aluminum foil current collector. After drying and cold pressing, a positive electrode sheet was obtained, with a coating weight per unit area of ​​0.27 g / 1540.25 mm² on each side. 2 .

[0178] Preparation of negative electrode sheet

[0179] Graphite (negative electrode active material), sodium carboxymethyl cellulose (thickener), styrene-butadiene rubber (binder), and acetylene black (conductive agent) were mixed in a mass ratio of 97:1:1:1. Deionized water was added, and the mixture was stirred under vacuum to obtain a negative electrode slurry. The negative electrode slurry was then uniformly coated onto both sides of a copper foil. After the copper foil was dried at room temperature, it was transferred to a 120°C oven and dried for 1 hour. The foil was then cold-pressed and slit to obtain negative electrode sheets, with a coating weight of 0.17 g / 1540.25 mm² on each side. 2 .

[0180] Separating membrane

[0181] A 12μm thick polypropylene separator membrane was selected.

[0182] Preparation of electrolyte

[0183] The organic solvent was a mixture containing ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC), with a volume ratio of EC:20:20:60. Thoroughly dried lithium salt LiPF6 was dissolved in the organic solvent and mixed thoroughly in an argon-atmosphere glove box with a water content of <10 ppm to obtain the electrolyte. The concentration of the lithium salt was 1 mol / L.

[0184] Preparation of battery cells

[0185] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrodes to provide isolation. After being wound into a cylindrical bare cell, it is placed in an aluminum-plastic film, baked at 80°C to remove water, injected with electrolyte, and sealed. After processes such as settling, hot and cold pressing, formation, clamping, and capacity testing, a single battery cell is obtained.

[0186] (3) Preparation of secondary batteries

[0187] Three battery cells are arranged in parallel along the "x" direction in Figure 1. The heat insulation pad obtained in step (1) is cut along the thickness direction so that its thickness is set along the "x" direction, and its length and width are consistent with the length and width of the battery cells respectively. The cut heat insulation pad is placed between two adjacent battery cells so that the heat insulation pad completely separates the two adjacent battery cells. Then it is encapsulated in the cavity to form a secondary battery.

[0188] Examples 2-12

[0189] The preparation process is similar to that in Example 1, with the main difference being that endothermic microcapsules with different parameters were used, as detailed in Table 1.

[0190] Examples 13-14

[0191] The preparation process is similar to that of Example 1, except that in step (1), the mass ratio of the heat-absorbing microcapsules to the binder was adjusted. Please refer to Table 1 for details.

[0192] Examples 15-17

[0193] Similar to the preparation process in Example 1, the main difference is that in step (1), the dipping time is adjusted to 10s, 1min and 2min respectively, so that the weight ratio of filler to heat insulation substrate changes. Please refer to Table 1 for details.

[0194] Example 18

[0195] The preparation process is similar to that of Example 1, except that the heat-absorbing microcapsules with triphenyl phosphate core material are used instead of the heat-absorbing microcapsules in Example 1.

[0196] Example 19

[0197] Similar to the preparation process of Example 1, the main difference is that in step (1), the immersion time is adjusted to 70s, so that the slurry enters the porous structure of the ceramic heat insulation substrate and is applied to the surface of the ceramic heat insulation substrate. Then the slurry applied to the surface of the ceramic heat insulation substrate is removed, and then dried under the same conditions to form a filler in the porous structure of the ceramic heat insulation substrate, and the surface of the heat insulation pad does not contain a filler layer.

[0198] Comparative Example 1

[0199] Similar to the preparation process of Example 1, the main difference is that step (1) is omitted, and in step (3), a ceramic heat insulation substrate with a thickness of 6 mm is used instead of the heat insulation pad, and the length and width of the ceramic heat insulation substrate are equal to the length and width of the heat insulation pad after slitting.

[0200] Table 1

[0201] In addition, the heat insulation pads and secondary batteries obtained in Examples 1 to 19 and Comparative Example 1 were subjected to performance tests, and the test results are shown in Table 2 below.

[0202] Test section

[0203] (1) Thermal conductivity test

[0204] The thermal conductivity of the insulation pad was tested using a thermal constant analyzer (model: Hot Disk). The thermal conductivity measurement range was 0.005 W / (m·K) to 500 W / (m·K).

[0205] (2) Thermal diffusion test

[0206] The secondary battery was subjected to thermal runaway testing in accordance with GB 38031-2020 "Safety Requirements for Power Batteries for Electric Vehicles".

[0207] Table 2

[0208] Comparing Examples 1-19 with Comparative Example 1, it can be seen that, compared with ceramic thermal insulation substrate, the thermal insulation pad prepared using this application can reduce the thermal conductivity of the thermal insulation pad, thereby reducing the occurrence of thermal runaway problems in secondary batteries.

[0209] The description of the various embodiments above tends to emphasize the differences between the various embodiments. The similarities or similarities between them can be referred to, and for the sake of brevity, they will not be repeated here.

[0210] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A secondary battery, comprising a battery cell and a heat insulation pad disposed adjacent to the sidewall of the battery cell; The heat insulation pad includes a heat insulation substrate and a filler, the filler being disposed inside the heat insulation substrate and / or at least a portion of the surface of the heat insulation substrate, the filler including heat-absorbing microcapsules.

2. The secondary battery according to claim 1, wherein, The number of battery cells is at least two, and the heat insulation pad is provided between the sidewalls of two adjacent battery cells.

3. The secondary battery according to claim 1 or 2, wherein, The heat insulation substrate has a porous structure inside, and the filler is disposed in the porous structure.

4. The secondary battery according to claim 3, wherein, The porous structure includes multiple pores, the pore diameter of which is larger than the particle size of the heat-absorbing microcapsules.

5. The secondary battery according to any one of claims 1 to 4, wherein, The heat-absorbing microcapsule includes a core and a wall covering the core. The core contains a core material, and the wall contains a wall material. The boiling point of the core material is lower than the melting point of the wall material.

6. The secondary battery according to claim 5, wherein, The boiling point of the core material is less than or equal to 80°C, and the melting point of the wall material is 90°C to 160°C.

7. The secondary battery according to claim 5 or 6, wherein, The heat-absorbing microcapsules satisfy one or more of the following conditions: (1) The core material includes one or more of perfluorohexanone, fluoroalkyl compounds and halon compounds; (2) The wall material includes one or more of microcrystalline wax, polyolefin compounds and their derivatives and polyacrylate compounds; (3) The core of the capsule accounts for 60% to 80% of the mass of the heat-absorbing microcapsule.

8. The secondary battery according to any one of claims 5 to 7, wherein, The heat-absorbing microcapsules satisfy one or more of the following conditions: (1) The core material includes one or more of perfluorohexanone, heptafluoropropane, hexafluoropropane and bromotrifluoromethane; (2) The wall material includes one or more of microcrystalline wax, oxidized polyethylene, oxidized polypropylene and polymethyl methacrylate; (3) The core of the capsule accounts for 65% to 75% of the mass of the heat-absorbing microcapsule.

9. The secondary battery according to any one of claims 1 to 8, wherein, The volume average particle size Dv50 of the heat-absorbing microcapsules is 100μm to 500μm.

10. The secondary battery according to any one of claims 1 to 9, wherein, The filler is provided both inside the heat insulation substrate and on the surface of the heat insulation substrate, and the filler forms a filler layer on the surface of the heat insulation substrate.

11. The secondary battery according to claim 10, wherein, The thickness of the filler layer is 0.5mm to 1.5mm.

12. The secondary battery according to any one of claims 1 to 11, wherein, The weight ratio of the filler to the heat insulation substrate is (0.1 to 0.5):

1.

13. The secondary battery according to any one of claims 1 to 12, wherein, The weight ratio of the filler to the heat insulation substrate is (0.2-0.3):

1.

14. The secondary battery according to any one of claims 1 to 13, wherein, The filler also includes a binder, which is mixed with the heat-absorbing microcapsules.

15. The secondary battery according to claim 14, wherein, In the filler, the mass ratio of the heat-absorbing microcapsule to the binder is (50-70):(30-50).

16. The secondary battery according to any one of claims 1 to 15, wherein, The material of the thermal insulation substrate includes one or more of ceramics, aerogels, silicone, and glass fibers.

17. The secondary battery according to any one of claims 1 to 16, wherein, The thermal conductivity of the insulation pad is 0.01 W / m·K to 0.1 W / m·K.

18. The secondary battery according to any one of claims 1 to 17, wherein, The thermal conductivity of the insulation pad is 0.01 W / m·K to 0.03 W / m·K.

19. A heat insulation pad comprising a heat insulation substrate and a filler, the filler being disposed inside the heat insulation substrate and / or at least a portion of the surface of the heat insulation substrate, the filler comprising heat-absorbing microcapsules.

20. The heat insulation pad according to claim 19, wherein, The heat insulation pad is the heat insulation pad in the secondary battery according to any one of claims 2 to 18.

21. An electrical device comprising a secondary battery as described in any one of claims 1 to 18 or a heat-insulating pad as described in any one of claims 19 to 20.

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