Battery monomer, battery and electric device

Abstract

The invention relates to the technical field of batteries, and provides a battery monomer, a battery and a power utilization device, the battery monomer comprises a shell and an electrode assembly, the electrode assembly is located in the shell, the electrode assembly comprises a negative plate, a positive plate and an isolating membrane, and at least one isolating membrane is arranged between the adjacent positive plate and negative plate; the negative plate comprises a negative current collector and a negative active layer, the negative active layer is arranged on at least one surface of the negative current collector along the thickness direction, and the melting point of the negative active layer is lower than the thermal shrinkage temperature of the isolating membrane. The local phase change of the negative electrode active layer can inhibit the temperature rise in the shell, so that the temperature in the shell is lower than the thermal shrinkage temperature of the isolating membrane, that is, the isolating membrane is basically not subjected to thermal shrinkage, the contact short-circuit risk of the positive plate and the negative plate is reduced, the self-protection barrier effect is achieved, the heat spreading is inhibited, and the heat spreading risk is reduced.

Description

Technical Field

[0001] This application relates to the field of battery technology, and in particular to a battery cell, a battery, and an electrical device. Background Technology

[0002] Batteries are being used more and more widely in daily life and production. For example, new energy vehicles equipped with batteries are already widely used, and batteries can be used to provide all or part of the power for new energy vehicles.

[0003] In related technologies, if a single cell of a battery experiences thermal runaway, it can easily lead to thermal propagation and battery failure, affecting battery safety. Summary of the Invention

[0004] In view of this, embodiments of this application aim to provide a battery cell, a battery, and an electrical device that can reduce the risk of heat spread.

[0005] To achieve the above objectives, the technical solution of this application embodiment is implemented as follows:

[0006] The first aspect of this application provides a battery cell, comprising:

[0007] shell;

[0008] An electrode assembly is located inside the housing. The electrode assembly includes a negative electrode, a positive electrode, and a separator. At least one separator is disposed between adjacent positive and negative electrode sheets. The negative electrode includes a negative current collector and a negative active layer. The negative active layer is disposed on at least one surface of the negative current collector along the thickness direction. The melting point of the negative active layer is lower than the heat shrinkage temperature of the separator.

[0009] The battery cell provided in this application embodiment has a negative electrode active layer with a melting point lower than the thermal shrinkage temperature of the separator. With this design, when the temperature inside the casing rises, the temperature inside the casing will reach the melting point of the negative electrode active layer first due to its relatively low melting point. This causes local melting of the negative electrode active layer, which then partially melts and separates from the negative electrode sheet, becoming a separate entity. The separated entity transforms the originally complete negative electrode active material into a scattered conductive distribution, which cannot form a continuous thermal conductor. Heat cannot spread rapidly to the remaining negative electrode active layer of the negative electrode sheet through solid contact. In other words, local melting of the negative electrode sheet inhibits further heat spread on the negative electrode sheet. In addition, the negative electrode active layer absorbs heat during the melting process, which can delay or inhibit the temperature inside the casing from rising further to a certain extent, thereby preventing the continued occurrence of internal heat spread. The local phase change of the negative electrode active layer can suppress the temperature rise inside the shell. In this way, the temperature inside the shell will be lower than the thermal shrinkage temperature of the separator. That is to say, the separator will basically not undergo thermal shrinkage, reducing the risk of short circuit between the positive and negative electrodes, playing a self-protective barrier role, suppressing heat spread, reducing the risk of heat spread, and improving the safety performance of the battery cell.

[0010] In some embodiments, after the battery cell is charged, the negative electrode current collector deposits the negative electrode active layer on at least one surface along the thickness direction.

[0011] In this embodiment, since the negative electrode sheet lacks negative electrode active material before charging, its weight is reduced, thus increasing the energy density of the battery cell. The surface of the negative electrode current collector is essentially free of negative electrode active material before the first charge and discharge, improving safety during battery production and assembly.

[0012] In some embodiments, the material of the negative electrode active layer includes at least one of sodium metal and potassium metal.

[0013] In this embodiment, both sodium and potassium metals have melting points below 100°C and also possess good energy storage density.

[0014] In some embodiments, the surface of the negative electrode current collector is divided into at least two partition regions, each partition region containing the negative electrode active layer.

[0015] In this embodiment, the negative electrode active layer is divided into multiple small units. When the local temperature of the negative electrode sheet rises to the point of runaway failure and the negative electrode active layer in some of the separated areas melts, heat transfer can be slowed down or suppressed, so as to avoid affecting the negative electrode active layer in other separated areas to a certain extent and reduce the risk of heat spread.

[0016] In some embodiments, the negative electrode sheet includes a support structure, and the support structure is disposed on at least one surface of the negative electrode current collector along the thickness direction, the support structure dividing the surface of the negative electrode current collector into at least two partition regions.

[0017] In this embodiment, on the one hand, the support structure can enhance the structural strength of the negative electrode current collector. The support structure can support the negative electrode current collector and the other structural layers, playing an interlayer support role. On the other hand, the support structure divides the surface of the negative electrode current collector into at least two partition regions, each containing a negative electrode active layer. In this way, the negative electrode active layer is divided into multiple small units. In the event that the local temperature of the negative electrode sheet rises to a point of runaway failure and the negative electrode active layer in some partition regions melts, the support structure can inhibit further heat transfer and reduce the risk of heat spread.

[0018] In some embodiments, the support structure is printed or etched onto the negative electrode current collector.

[0019] In this embodiment, both the printing and etching processes are relatively mature, the manufacturing cost is relatively low, and the yield rate of the support structure is high.

[0020] In some embodiments, the support structure includes at least two support bars, at least a portion of which form a closed area.

[0021] In this embodiment, the partition area, as a closed area, can block heat transfer between the partition areas as much as possible.

[0022] In some embodiments, the support structure includes a first support bar and a second support bar, the first support bar and the second support bar intersecting.

[0023] In this embodiment, the first support bar and the second support bar can divide the surface of the negative electrode current collector into more partitioned areas.

[0024] In some embodiments, at least two of the first support bars and at least two of the second support bars are staggered to form a grid-like area.

[0025] In this embodiment, the support structure is roughly a grid structure with more partitions, and the negative electrode active layer is divided into more modules with smaller individual areas.

[0026] In some embodiments, the negative electrode sheet includes a conductive layer located between the negative electrode current collector and the support structure in the thickness direction of the negative electrode current collector.

[0027] In this embodiment, the conductive layer has the function of conducting electricity and providing electron conduction. The conductive layer can also play an interface modification role, improving the morphology of the negative electrode active layer and making the negative electrode active layer more dense.

[0028] In some embodiments, the battery cell includes a flame-retardant component located within a housing, and the flame-retardant component is disposed on at least one surface of the separator along its thickness direction. The flame-retardant component includes a casing and a flame retardant, the flame retardant being contained within the casing, and the melting point of the casing being lower than the heat shrinkage temperature of the separator.

[0029] In this embodiment, the flame retardant is encapsulated in a shell. Under normal battery cell conditions, the flame retardant will not be released. However, if the battery cell experiences thermal runaway and the temperature inside the shell rises, the temperature inside the shell will reach the melting point of the shell first because the melting point of the shell is lower than the thermal shrinkage temperature of the separator. This causes localized melting of the shell, creating a gap. The flame retardant can then be released into the shell through this gap, thus preventing, delaying, or terminating the spread of flame and inhibiting further thermal runaway.

[0030] In some embodiments, the flame retardant element covers two surfaces of the insulating membrane along its thickness direction.

[0031] In this embodiment, the flame-retardant component is laid on the surface of the isolation membrane along its thickness direction as a flame-retardant layer. This design provides better flame-retardant performance.

[0032] In some embodiments, the battery cell includes an insulating heat insulation element located within the housing, and at least one of the electrode assemblies is provided with the insulating heat insulation element on at least one side along the thickness direction, wherein the melting point of the insulating heat insulation element is lower than the heat shrinkage temperature of the separator.

[0033] In this embodiment, on the one hand, the insulating and heat-insulating component can restrain the electrode assembly, reducing or even eliminating the probability of the electrode assembly shaking within the casing. On the other hand, in the event of thermal runaway within the battery cell, the insulating and heat-insulating component can melt and flow into the electrode assembly. For example, the liquid-phase insulating and heat-insulating component can cover the surface of the negative electrode to form an insulating barrier, further isolating the positive and negative electrodes and thus avoiding short-circuit risks to a certain extent.

[0034] In some embodiments, the insulating and heat-insulating component is made of at least one of paraffin wax, polyethylene, polymethyl methacrylate, polyethylene terephthalate, polytetrafluoroethylene, and melamine.

[0035] In this embodiment, after the temperature inside the outer casing rises to the melting point of the aforementioned material, the material melts and penetrates into the electrode assembly, forming a non-conductive barrier on the surface of the positive electrode and / or the surface of the negative electrode.

[0036] In some embodiments, the amount of oxygen released by the positive electrode is no more than 0.5 wt% of the mass of the positive electrode active layer of the positive electrode.

[0037] In this embodiment, the lower the oxygen release of the positive electrode, the less oxygen is released by the positive electrode. In this way, in the event of thermal runaway of the battery, there is insufficient oxygen in the casing to aid combustion, thereby avoiding open flames or heat spread in the casing to a certain extent and slowing down the degree of failure as much as possible.

[0038] In some embodiments, the positive electrode includes a positive electrode active layer, the material of which includes at least one of polyanionic, Prussian, and modified versions of each material.

[0039] In this embodiment, the material of the positive electrode active layer includes at least one of polyanionic, Prussian, modified polyanionic, and modified Prussian materials. These materials have the characteristics of low oxygen release or no oxygen release.

[0040] In some embodiments, the material of the positive electrode active layer includes at least one of NaFePO4, NaMnPO4, NaCoPO4, Na4Fe3(PO4)2O7, Na3V2(PO4)2F3, Na3V2(PO4)3, Prussian blue, Prussian white, and modifiers of each material.

[0041] In this embodiment, the material of the positive electrode active layer has the characteristic of low oxygen release or no oxygen release, and the oxygen release is no more than 0.5% by mass.

[0042] In some embodiments, the thermal runaway temperature of the battery cell is not less than 220°C.

[0043] In this embodiment, the thermal runaway temperature of the battery cell is relatively high, resulting in a low risk of thermal runaway and high safety.

[0044] A second aspect of this application provides a battery, comprising any one of the battery cells described above as a first battery cell.

[0045] The battery provided in this application embodiment includes the battery cell of this application and has the same or corresponding beneficial effects as the battery cell.

[0046] In some embodiments, the battery includes a second battery cell, the second battery cell and the battery cell being stacked along a first direction to form a component of a cell unit, wherein the thermal runaway temperature of the second battery cell is not greater than 180°C.

[0047] In this embodiment, the single-cell unit includes different types of second battery cells and battery cells. The second battery cells can be used to improve the energy density of the battery, and the battery cells can serve as safety cells. In the event of thermal runaway in the second battery cell, the battery cells can isolate the second battery cell, prevent heat propagation, and improve the safety performance of the battery. Using battery cells as a heat insulation structure can also reduce the amount of heat insulation structure used and improve the utilization rate of space inside the casing. The combined use of second battery cells and first battery cells can meet both safety and energy density requirements.

[0048] In some embodiments, the single cell unit includes a heat insulation pad and at least two second battery cells, with at least one heat insulation pad disposed between two adjacent second battery cells.

[0049] In this embodiment, heat transfer between two adjacent second battery cells can be blocked or delayed by a heat insulation pad, thereby suppressing the spread of heat between multiple cells.

[0050] In some embodiments, in any one of the individual cell units, the ratio of the number of the second battery cells to the number of the first battery cells is 0.5:1 to 5:1.

[0051] In this embodiment, the second battery cell can save production costs, the total heat generated by all the second battery cells in the cell unit can be controlled, the heat generated per unit cell is relatively small, the number of battery cells can improve the reliability of suppressing heat spread, reduce the amount of heat insulation structure such as heat insulation pad, save heat insulation structure such as heat insulation pad, and can increase battery capacity.

[0052] In some embodiments, the second battery cell includes a positive electrode active material layer, the material of which includes at least one of nickel-cobalt-manganese ternary materials, lithium manganese oxide, lithium iron phosphate, and lithium manganese iron phosphate.

[0053] In this embodiment, the material of the positive electrode active material layer has a relatively low cost and a relatively high energy density.

[0054] A third aspect of this application provides an electrical device including a battery as described in any one of the above embodiments for providing electrical energy.

[0055] The electrical device provided in this application includes the battery cell of this application and has the same or corresponding beneficial effects as the battery cell. Attached Figure Description

[0056] Figure 1 This is a schematic diagram of the structure of a single battery cell in one embodiment of this application;

[0057] Figure 2This is a schematic diagram of the negative electrode current collector and the first type of support structure in one embodiment of this application;

[0058] Figure 3 This is a schematic diagram of the negative electrode current collector and the second support structure in one embodiment of this application;

[0059] Figure 4 This is a schematic diagram of the negative electrode current collector and the third type of support structure in one embodiment of this application;

[0060] Figure 5 This is a schematic diagram of the structure of the first electrode assembly and the insulating heat insulation component in one embodiment of this application;

[0061] Figure 6 This is a schematic diagram of the structure of the second type of electrode assembly and insulating heat insulation component in one embodiment of this application;

[0062] Figure 7 This is a schematic diagram of the structure of the first type of single-unit in one embodiment of this application;

[0063] Figure 8 This is a schematic diagram of the structure of the second type of single-unit in one embodiment of this application;

[0064] Figure 9 This is a schematic diagram of the structure of the third type of single-unit in one embodiment of this application;

[0065] Figure 10 This is a schematic diagram of the structure of a flame-retardant component in one embodiment of this application;

[0066] Figure 11 This is a schematic diagram of the vehicle structure in one embodiment of this application.

[0067] Explanation of reference numerals in the attached figures

[0068] Vehicle 1000; Battery 100; Controller 200; Motor 300; Single cell 10; Battery cell 1; Casing 11; Electrode assembly 12; Negative current collector 121; Separating area 121a; Support structure 122; First support bar 1221; Second support bar 1222; Flame retardant 13; Encasing shell 131; Flame retardant 132; Insulating and heat-insulating component 14; Second battery cell 2; Heat insulation pad 3. Detailed Implementation

[0069] The embodiments of the technical solution of this application will now be described in detail with reference to the accompanying drawings. These embodiments are only used to more clearly illustrate the technical solution of this application and are therefore merely examples, and should not be used to limit the scope of protection of this application.

[0070] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit this application.

[0071] In the description of the embodiments of this application, the technical terms "first", "second", etc. are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features.

[0072] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0073] It should be noted that in this application, the first direction, the second direction, and the third direction are mutually perpendicular, together forming a three-dimensional vertical coordinate system. "At least two" refers to two or more directions. "Multiple" refers to two or more directions. The unit "℃" is degrees Celsius. The unit "μm" is micrometers. The unit "K / min" is Kelvin per minute. The unit "℃ / s" is degrees Celsius per second. The unit "s" is seconds. The unit "℃ / min" is degrees Celsius per minute.

[0074] In related technologies, numerous improvements have been made to the separator and negative electrode active layer to enhance the performance of individual battery cells. For example, to improve the power performance of a battery cell, the porosity of the separator has been increased; using a high-porosity separator reduces internal resistance, thereby improving power performance. Another example is using amorphous carbon and porous carbon materials as the negative electrode active layer to reduce resistance during charging and discharging, thus improving power performance. To improve battery cell performance, such as power performance, porous carbon negative electrodes are used to accelerate ion conduction; to improve battery cell storage life or reduce gas production, materials such as hard carbon / amorphous carbon are used to embed active ions into the channels, reducing reactions between metals and electrolytes. In other words, while related technologies have improved the materials and structure of the separator and negative electrode active layer to enhance battery cell performance, they have not addressed the melting point of the negative electrode active layer and the thermal shrinkage temperature of the separator. In some cases, in order to improve the performance of a battery cell, the thermal shrinkage temperature of the separator may be lowered and / or the melting point of the negative electrode active layer may be raised. This may result in the melting point of the negative electrode active layer being higher than the thermal shrinkage temperature of the separator, increasing the probability of short circuit between the positive and negative electrodes of the battery cell and increasing the risk of thermal runaway of the battery cell.

[0075] In related technologies, when the separator in a battery cell shrinks due to heat, the positive and negative electrodes of the cell may short-circuit. Under conditions of internal short circuits, overheating, or other failures, the battery cell is prone to thermal runaway. In some cases, the active material of the positive electrode releases oxygen at high temperatures, essentially introducing a combustion accelerant into the previously sealed battery cell under failure conditions, intensifying the reaction. With the electrolyte in the negative electrode ignited, heat spreads continuously within the cell and can easily spread to other cells that haven't yet experienced thermal runaway, potentially leading to thermal runaway in all cells and posing a risk of battery fire. In vehicles, this could potentially cause a vehicle fire, posing a safety hazard.

[0076] The battery cell provided in this application includes a casing and an electrode assembly. The electrode assembly is located inside the casing and includes a negative electrode sheet, a positive electrode sheet, and a separator. At least one separator is disposed between adjacent positive and negative electrode sheets. The negative electrode sheet includes a negative current collector and a negative active layer. At least one surface of the negative current collector along the thickness direction is provided with the negative active layer. The melting point of the negative active layer is lower than the heat shrinkage temperature of the separator.

[0077] The melting point of the negative electrode active layer is lower than the thermal shrinkage temperature of the separator. With this design, when the temperature inside the casing rises, the relatively lower melting point of the negative electrode active layer causes it to reach that point first, resulting in localized melting of the negative electrode active layer. This localized melting breaks off and detaches from the negative electrode sheet, forming a separate entity. This separate entity transforms the originally intact negative electrode active material into a scattered, conductive distribution, preventing the formation of a continuous thermal conductor. Heat cannot rapidly spread to the remaining negative electrode active layer via solid-state contact. In other words, localized melting of the negative electrode sheet inhibits further heat spread. Furthermore, the negative electrode active layer absorbs heat during melting, which can, to some extent, delay or suppress further temperature increases within the casing, thus preventing continued internal heat spread. The localized phase change of the negative electrode active layer suppresses temperature increases within the casing, keeping the internal temperature below the thermal shrinkage temperature of the separator. This means the separator essentially does not undergo thermal shrinkage, reducing the risk of short circuits between the positive and negative electrodes, acting as a self-protective barrier, suppressing heat spread, reducing the risk of heat spread, and improving the safety performance of the battery cell.

[0078] Please see Figure 1 and Figure 11 This application provides a battery 100, which includes a battery cell 1 as a first battery cell in any embodiment of this application.

[0079] In some embodiments, the battery 100 includes a housing, and the battery cell 1 is located inside the housing. The housing can protect the battery cell 1 from liquids or other foreign matter affecting the charging and discharging of the battery cell 1.

[0080] For example, the enclosure can be a sealed enclosure, which provides more reliable dust and water protection, and can therefore be used in harsher, more humid, or even submerged environments.

[0081] Please see Figure 11 This application also provides an electrical device, which includes a battery 100 for providing electrical energy, as described in any embodiment of this application.

[0082] Electrical devices include, but are not limited to, energy storage devices, mobile phones, tablets, laptops, electric toys, power tools, electric vehicles, electric cars, ships, or spacecraft. Among them, electric toys can include stationary or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc. Spacecraft can include airplanes, rockets, space shuttles, and spacecraft, etc.

[0083] In the following embodiments, for ease of explanation, a vehicle 1000 is used as an example of an electrical device according to an embodiment of this application. The description is as follows with reference to the accompanying drawings.

[0084] Figure 11 The diagram illustrates the structure of a vehicle 1000 as provided in some embodiments of this application. The vehicle 1000 can be a gasoline-powered vehicle, a natural gas-powered vehicle, or a new energy vehicle. New energy vehicles can be pure electric vehicles, hybrid electric vehicles, or range-extended electric vehicles, etc. Figure 11 As shown, a battery 100 is installed inside the vehicle 1000. The battery 100 can be located at the bottom, front, or rear of the vehicle 1000. The battery 100 can be used to power the vehicle 1000; for example, the battery 100 can serve as the operating power source for the vehicle 1000. The vehicle 1000 may also include a controller 200 and a motor 300. The controller 200 is used to control the battery 100 to supply power to the motor 300, for example, to meet the power needs of the vehicle 1000 during starting, navigation, and driving.

[0085] In some embodiments of this application, the battery 100 can not only serve as the operating power source for the vehicle 1000, but also as the driving power source for the vehicle 1000, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle 1000.

[0086] Please see Figures 1 to 5 The battery cell 1 provided in this application embodiment includes a casing 11 and an electrode assembly 12.

[0087] Please continue reading. Figures 1 to 5The electrode assembly 12 is located inside the housing 11. The electrode assembly 12 includes a negative electrode sheet, a positive electrode sheet, and a separator. At least one separator is disposed between adjacent positive and negative electrode sheets. The negative electrode sheet includes a negative current collector 121 and a negative active layer. At least one surface of the negative current collector 121 along the thickness direction is provided with a negative active layer. The melting point of the negative active layer is lower than the heat shrinkage temperature of the separator.

[0088] Electrode assembly 12 is the energy storage structure of battery cell 1.

[0089] At least one separator is provided between adjacent positive and negative electrode plates. The separator is provided between the positive and negative electrode plates to prevent short circuits.

[0090] For example, the negative electrode current collector 121 has two opposing surfaces along its thickness direction, and a negative electrode active layer is disposed on either or both of the two opposing surfaces along the thickness direction. In one embodiment, the negative electrode active layer is disposed on one surface of the negative electrode current collector 121 along the thickness direction. In another embodiment, the negative electrode active layer is disposed on both surfaces of the negative electrode current collector 121 along the thickness direction.

[0091] The melting point of the negative electrode active layer refers to the temperature at which the negative electrode active layer changes from a solid state to a liquid state.

[0092] The heat shrinkage temperature of a separating film refers to the temperature at which the separating film shrinks when heated.

[0093] The battery cell 1 provided in this application embodiment has a negative electrode active layer with a melting point lower than the thermal shrinkage temperature of the separator. With this design, when the temperature inside the casing 11 rises, the temperature inside the casing 11 will reach the melting point of the negative electrode active layer first because the melting point of the negative electrode active layer is relatively low. This causes local melting of the negative electrode active layer, which then breaks off and separates from the negative electrode sheet to become a separate body. The separate body turns the originally complete negative electrode active material into a scattered conductive distribution, which cannot form a continuous thermal conductor. Heat cannot spread rapidly to the remaining negative electrode active layer of the negative electrode sheet in a solid contact manner. In other words, the negative electrode sheet undergoes local melting to suppress the continued spread of heat on the negative electrode sheet. In addition, the negative electrode active layer absorbs heat during the melting process, which can delay or suppress the continued rise of the temperature inside the casing 11 to a certain extent, thereby preventing the continuous occurrence of internal heat spread. The local phase change of the negative electrode active layer can suppress the temperature rise inside the shell 11. In this way, the temperature inside the shell 11 will be lower than the thermal shrinkage temperature of the separator. That is to say, the separator will basically not undergo thermal shrinkage, reducing the risk of short circuit between the positive and negative electrode plates, playing a self-protective barrier role, suppressing heat spread, and improving the safety performance of the battery cell 1.

[0094] It should be noted that melting point has a well-known meaning in the art and can be determined using methods and instruments known in the art. For example, in a heat flow-temperature change graph, the peak temperature of the DSC curve is the melting point. The melting point of a substance can be tested with reference to ASTM D3418-2015.

[0095] It should be noted that the heat shrinkage temperature of the release liner can be determined as follows: Multiple release liner samples of a set size are placed in a vacuum oven at different set temperatures (starting at 100℃, increasing by 5℃ increments) and held at that temperature for 2 hours. The shrinkage size of the release liner after holding at that temperature is then measured. The number of release liner samples should be ≥5. The maximum and minimum values ​​are removed to reduce error, and the average of the remaining samples is calculated, for example, an arithmetic mean. Taking 5 release liner samples as an example, the maximum and minimum values ​​are removed to reduce error, and the average of the remaining 3 samples is calculated, for example, an arithmetic mean. The shrinkage size of the release liner can be obtained using the above method. The temperature corresponding to a heat shrinkage ratio in the length and width directions of the release liner that meets the set conditions is the heat shrinkage temperature of the release liner. The set conditions include: a heat shrinkage ratio in the length direction reaching 5.0% and a heat shrinkage ratio in the width direction reaching 3.0%. The heat shrinkage ratio in the length direction refers to the ratio of the shrinkage size in the length direction of the release liner after holding at that temperature to the set size in the length direction. The heat shrinkage ratio in the width direction refers to the ratio of the shrinkage dimension of the separator film in the width direction after being kept at a constant temperature to the set dimension in the width direction.

[0096] In one embodiment, after the battery cell 1 is charged, a negative electrode active layer is deposited on at least one surface of the negative electrode current collector 121 along the thickness direction. That is, before the first charge and discharge, there is essentially no negative electrode active layer on the negative electrode current collector 121, and the battery cell 1 is generally referred to as a negative electrode-free battery cell 1.

[0097] For example, during charging, the second active ions of battery cell 1 combine with electrons on the surface of the negative electrode current collector 121, resulting in deposition and forming a negative electrode active layer. Since the negative electrode sheet lacks active material before charging, its mass is reduced, increasing the energy density of battery cell 1. The surface of the negative electrode sheet is essentially devoid of active material before the first charge and discharge, improving safety during the battery 100 manufacturing and assembly process.

[0098] In one embodiment, under normal temperature and pressure, the cohesion of the liquid-phase negative electrode active layer is relatively large. For example, the cohesion of the liquid-phase negative electrode active layer is greater than the adhesion of the liquid-phase negative electrode active layer to the surface of the separator. The normal temperature can be -20°C to 50°C, and the normal pressure can be one atmosphere. During the melting process of the negative electrode active layer, a portion of the negative electrode active layer melts and detaches from the negative electrode sheet. The detached liquid-phase negative electrode active layer agglomerates into separate bodies. For example, the detached liquid-phase negative electrode active layer agglomerates and disperses into solid separate bodies of blocky or spherical shapes. The detached liquid-phase negative electrode active layer basically does not wet the separator, and the agglomerated separate bodies cannot cause heat propagation on the remaining negative electrode sheet through solid-state contact.

[0099] In one embodiment, the melting point of the negative electrode active layer may not exceed 100°C. A melting point less than or equal to 100°C allows the negative electrode active layer to partially melt and break off during thermal runaway, thus inhibiting heat propagation and providing self-protection.

[0100] In one embodiment, the negative electrode active layer can be made of metal. For example, the negative electrode active layer can be made of a metal with a melting point not exceeding 100°C.

[0101] For example, in one embodiment, the material of the negative electrode active layer includes at least one of sodium metal and potassium metal. Both sodium metal and potassium metal have melting points below 100°C and also possess good energy storage density.

[0102] In one embodiment, the surface of the negative electrode current collector 121 is divided into at least two partition regions 121a, and each partition region 121a contains a negative electrode active layer. In this way, the negative electrode active layer is divided into multiple small units. If the local temperature of the negative electrode sheet rises to a point of runaway failure, and the negative electrode active layer in part of the partition region 121a melts, heat transfer can be slowed down or suppressed, thereby avoiding impact on the negative electrode active layer in other partition regions 121a to a certain extent and reducing the risk of heat propagation.

[0103] In one embodiment, a groove may be formed on the surface of the negative electrode current collector 121 to separate at least two partition regions 121a. The groove is not limited in its formation method; for example, a portion of the material on the surface of the negative electrode current collector 121 may be removed by an etching process to form the groove.

[0104] In one embodiment, please refer to Figures 2 to 4 The negative electrode sheet includes a support structure 122, and the negative electrode current collector 121 has the support structure 122 disposed on at least one surface along the thickness direction.

[0105] The support structure 122 divides the surface of the negative electrode current collector 121 into at least two partition regions 121a.

[0106] For example, a support structure 122 is provided on one or both of the two opposing surfaces of the negative electrode current collector 121 along the thickness direction. In one embodiment, the support structure 122 is provided on one surface of the negative electrode current collector 121 along the thickness direction. In another embodiment, the support structure 122 is provided on both surfaces of the negative electrode current collector 121 along the thickness direction.

[0107] The support structure 122 may protrude from at least one surface of the negative electrode current collector 121 along the thickness direction. That is, the support structure 122 is a structure that is added to at least one surface of the negative electrode current collector 121 along the thickness direction.

[0108] In this embodiment, on the one hand, the support layer support structure 122 can strengthen the structural strength of the negative electrode current collector 121. The support layer support structure 122 can support the negative electrode current collector 121 and the other structural layers, playing an interlayer support role. On the other hand, the support structure 122 divides the surface of the negative electrode current collector 121 into at least two partition regions 121a. The partition region 121a contains a negative electrode active layer. In this way, the negative electrode active layer is divided into multiple small units. In the event that the local temperature of the negative electrode sheet rises and becomes an uncontrolled failure point, and the negative electrode active layer in part of the partition region 121a melts, the support structure 122 can inhibit further heat transfer and reduce the risk of heat spread.

[0109] In one embodiment, please refer to Figure 2 and Figure 3 The support structure 122 includes at least two support bars, with at least a portion of the support bars forming a closed region. For example, all support bars may form a closed region. Alternatively, only a portion of the support bars may form a closed region. In some embodiments, at least a portion of the support bars extends to the edge of the negative electrode current collector 121, and the partition region 121a defined by the support bars and the edge of the negative electrode current collector 121 is a closed region. In some embodiments, the support bars are interconnected to form closed regions, and the partition region defined by the support bars is a closed region. The partition region 121a, as a closed region, can effectively block heat transfer between the partition regions.

[0110] In one embodiment, please refer to Figure 2 and Figure 3 The support structure 122 includes at least two spaced-apart first support bars 1221, each of which extends in parallel. The parallel extension of the first support bars 1221 means that the first support bars 1221 are approximately parallel, so that the portion of the surface of the negative electrode current collector 121 located between two adjacent first support bars 1221 can be a separation region 121a.

[0111] It is understandable that the support bar includes a first support bar 1221, meaning that the first support bar 1221 is one type of support bar. The support bar also includes a second support bar 1222, meaning that the second support bar 1222 is another type of support bar.

[0112] In one embodiment, the spacing between any two adjacent first support bars 1221 may be equal or unequal.

[0113] The extension direction of the first support bar 1221 is not limited. For example, in one embodiment, please refer to... Figure 3 The first support bar 1221 extends along the length direction of the negative electrode current collector 121. In another embodiment, the first support bar 1221 may also extend along a direction intersecting the length direction, for example, see [reference needed]. Figure 2 The first support strip 1221 extends along the width direction of the negative electrode current collector 121. In some embodiments, the first support strip 1221 may extend to the edge of the negative electrode current collector 121.

[0114] The shape of the first support strip 1221 is not limited. The first support strip 1221 can extend along a straight line, or it can extend along a curve. In one embodiment, please refer to... Figure 4 The support structure 122 includes a first support strip 1221 and a second support strip 1222, which intersect. Specifically, the intersection of the first support strip 1221 and the second support strip 1222 is located on the surface of the negative electrode current collector 121. In this way, the first support strip 1221 and the second support strip 1222 can divide the surface of the negative electrode current collector 121 into more partition regions 121a.

[0115] In one embodiment, please refer to Figure 4 At least two first support bars 1221 and at least two second support bars 1222 are interlaced to form a grid-like area. With this design, the support structure 122 is roughly grid-like, the number of partition regions 121a is greater, and the negative electrode active layer is divided into more modules with smaller individual areas.

[0116] Understandably, please refer to Figure 4 The supporting structure 122 is generally in the form of a grid, and the shape of the dividing area 121a is not limited. For example, the dividing area 121a can be polygonal, circular, elliptical, or irregular, etc. Irregular shape refers to an irregular shape. Polygons include, but are not limited to, squares or rhombuses, etc.

[0117] As an example, in one embodiment, please refer to Figure 4One of the first support bar 1221 and the second support bar 1222 extends along the length direction of the negative electrode current collector 121, and the other of the first support bar 1221 and the second support bar 1222 extends along the width direction of the negative electrode current collector 121.

[0118] The shape of the second support bar 1222 is not limited. The second support bar 1222 can extend along a straight line or along a curve.

[0119] The support structure 122 can be made of a conductive or insulating material. For example, the support structure 122 can be made of a resin and / or a polymer such as polyacrylic acid.

[0120] The manufacturing process of the support structure 122 is not limited; the support structure 122 is formed by printing or etching on the negative electrode current collector 121. For example, the support structure 122 can be attached to the surface of the negative electrode current collector 121 by processes such as gravure printing, 3D printing, or UV printing. Both printing and etching processes are relatively mature, with relatively low manufacturing costs and a high yield rate for the support structure 122.

[0121] In one embodiment, the thickness of the support structure 122 can be from 5 μm to 50 μm. For example, the thickness of the support structure 122 can be 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, 28 μm, 30 μm, 35 μm, 40 μm, 45 μm, 47 μm, or 50 μm, etc. Thus, the support structure 122 has good support properties and will not collapse during the processing and shaping of the negative electrode sheet.

[0122] In one embodiment, the negative electrode sheet includes a conductive layer, which is located between the negative electrode current collector 121 and the support structure 122 in the thickness direction of the negative electrode current collector 121. That is, the negative electrode current collector 121, the conductive layer, and the support structure 122 are stacked sequentially in the thickness direction of the negative electrode current collector 121, and the negative electrode active layer can be located on the conductive layer. The conductive layer has electrical conductivity, providing electron conduction. The conductive layer can also act as an interface modifier, improving the morphology of the negative electrode active layer and making it more dense.

[0123] The manufacturing process of the conductive layer is not limited. For example, the conductive paste can be coated on the surface of the negative electrode current collector 121 and dried to form the desired shape.

[0124] It is understandable that, without a conductive layer on the surface of the negative electrode current collector 121, the support structure 122 and the negative electrode active layer can be directly disposed on the surface of the negative electrode current collector 121.

[0125] In one embodiment, please refer to Figure 1 and Figure 10The battery cell 1 includes a flame-retardant element 13 located within the casing 11, and the flame-retardant element 13 is disposed on at least one surface of the separator along its thickness direction. The flame-retardant element 13 can prevent, delay, or terminate the spread of flame and suppress the continuous occurrence of thermal runaway.

[0126] The flame retardant component 13 includes a housing 131 and a flame retardant 132, wherein the flame retardant 132 is contained within the housing 131, and the melting point of the housing 131 is lower than the heat shrinkage temperature of the insulating film.

[0127] The melting point of the outer shell 131 refers to the temperature at which the outer shell 131 changes from a solid to a liquid state.

[0128] Flame retardant 132 can prevent, delay or terminate the spread of flame.

[0129] For example, flame-retardant elements 13 are provided on one or both of the two opposing surfaces of the separator along its thickness direction. In one embodiment, flame-retardant elements 13 are provided on one surface of the separator along its thickness direction. In another embodiment, flame-retardant elements 13 are provided on both surfaces of the separator along its thickness direction.

[0130] In this embodiment, the flame retardant 132 is encapsulated by the casing 131. Under normal conditions, the flame retardant 132 will not be released. However, if the battery cell 1 experiences thermal runaway and the temperature inside the casing 11 rises, the temperature inside the casing 11 will reach the melting point of the casing 131 first because the melting point of the casing 131 is lower than the thermal shrinkage temperature of the separator. This causes a localized melting of the casing 131, creating a gap. The flame retardant 132 can then be released from this gap into the casing 11, thus preventing, delaying, or terminating the spread of flame and inhibiting further thermal runaway.

[0131] The melting point of the casing 131 can be higher than that of the negative electrode. For example, the melting point of the negative electrode is no greater than 100°C, while the melting point of the casing 131 can be greater than 100°C.

[0132] The shape of the enclosure 131 is not limited; for example, in one embodiment, please refer to [reference needed]. Figure 10 The outer shell 131 can be roughly hollow spherical.

[0133] In one embodiment, the flame-retardant element 13 covers both surfaces of the isolation membrane along its thickness direction. That is, the flame-retardant element 13 is laid on the surface of the isolation membrane along its thickness direction as a flame-retardant layer. This design provides better flame-retardant performance.

[0134] In one embodiment, the shell thickness of the encapsulation shell 131 can be from 1 μm to 10 μm. That is, the shell thickness of the encapsulation shell 131 can be 1 μm, 3 μm, 5 μm, 7 μm, 9 μm, or 10 μm, etc. Under normal conditions of the battery cell 1, the strength of the encapsulation shell 131 is moderate, which can effectively protect the flame retardant 132 from leakage; under the condition of thermal runaway of the battery cell 1, the melting rate of the encapsulation shell 131 is moderate, which can form a notch relatively quickly to release the flame retardant 132.

[0135] In one embodiment, the diameter of the hollow cavity of the encapsulating shell 131 can be from 1 μm to 20 μm. For example, the diameter of the hollow cavity of the encapsulating shell 131 can be 1 μm, 5 μm, 10 μm, 14 μm, 15 μm, or 20 μm, etc. That is, the diameter of the flame retardant 132 located in the hollow cavity can be from 1 μm to 20 μm.

[0136] In one embodiment, the thickness of the flame-retardant layer can be from 3 μm to 30 μm. For example, the thickness of the flame-retardant layer can be 3 μm, 5 μm, 10 μm, 20 μm, or 30 μm, etc. This design allows the mass of the flame retardant 132 to be adapted to the size of the battery cell 1, more effectively suppressing thermal runaway.

[0137] The material of flame retardant 132 is not limited, and the material of flame retardant 132 includes, but is not limited to, 2,4-dimethyl-6-tert-butylphenol phosphate (DMTP).

[0138] The material of the outer shell 131 is not limited, but includes, but is not limited to, polymethyl methacrylate (PMMA).

[0139] The materials used for the separator include, but are not limited to, polypropylene (PP) and / or polyethylene (PE).

[0140] In one embodiment, the battery cell 1 includes an adhesive layer disposed between at least one surface of the flame-retardant component 13 and the separator along the thickness direction. That is, the adhesive layer is located on the side of the flame-retardant component 13 closer to the separator along the thickness direction. The adhesive layer not only facilitates stable adhesion of the flame-retardant component 13, but also serves to bond the positive and negative electrode sheets, shaping the interface between the positive and / or negative electrode sheets, reducing the risk of wrinkles in the positive and negative electrode sheets, and improving processing consistency.

[0141] In one embodiment, the battery cell 1 includes a composite coating disposed on at least one surface of the adhesive layer and the separator along the thickness direction. The composite coating can have liquid absorption function and improve the heat shrinkage resistance of the separator.

[0142] Composite coatings can be made of insulating inorganic materials and can also protect against micro-short circuits.

[0143] In one embodiment, the composite coating is made of at least one of ceramics and metal oxides.

[0144] In one embodiment, please refer to Figure 1 , Figure 5 and Figure 6 The battery cell 1 includes an insulating heat insulation element 14 located inside the housing 11. At least one electrode assembly 12 is provided with the insulating heat insulation element 14 on at least one side along the thickness direction. The melting point of the insulating heat insulation element 14 is lower than the heat shrinkage temperature of the separator.

[0145] An insulating and heat-insulating member 14 is provided on at least one side of the electrode assembly 12 along the thickness direction, that is, at least a portion of the insulating and heat-insulating member 14 overlaps with the electrode assembly 12 in the thickness direction. For example, the insulating and heat-insulating member 14 is provided on one side of the electrode assembly 12 along the thickness direction. Or, for example, the insulating and heat-insulating member 14 is provided on both sides of the electrode assembly 12 along the thickness direction.

[0146] The melting point of the insulating and heat-insulating component 14 refers to the temperature at which the insulating and heat-insulating component 14 changes from a solid state to a liquid state.

[0147] The insulating and heat-insulating component 14 has both heat insulation and electrical insulation functions. The melting point of the insulating and heat-insulating component 14 is lower than the thermal shrinkage temperature of the separator. Because the melting point of the insulating and heat-insulating component 14 is relatively low, the temperature inside the outer shell 11 will reach the melting point of the insulating and heat-insulating component 14 first, causing local melting of the insulating and heat-insulating component 14. The liquid phase of the insulating and heat-insulating component 14 flows into the electrode assembly 12 to further isolate the positive electrode and the negative electrode, thereby reducing the risk of short circuit between the positive electrode and the negative electrode and suppressing heat spread to a certain extent.

[0148] In this embodiment, on the one hand, the insulating and heat-insulating member 14 can restrain the electrode assembly 12, reducing or even eliminating the probability of the electrode assembly 12 shaking within the housing 11. On the other hand, in the event of thermal runaway within the battery cell 1, the insulating and heat-insulating member 14 can melt and flow into the electrode assembly 12. For example, the liquid phase insulating and heat-insulating member 14 can cover the surface of the negative electrode to form an insulating barrier, further isolating the positive and negative electrodes and thus avoiding short-circuit risks to a certain extent.

[0149] In one embodiment, the insulating and heat-insulating component 14 is made of at least one of paraffin wax, polyethylene, polymethyl methacrylate, polyethylene terephthalate, polytetrafluoroethylene, and melamine. Exemplarily, after the temperature inside the housing 11 rises to the melting point of the aforementioned materials, the materials melt and penetrate into the electrode assembly 12, forming a non-conductive barrier on the surface of the positive electrode and / or the negative electrode.

[0150] In one embodiment, the material of the insulating heat insulation element 14 includes, but is not limited to, paraffin wax. For example, after the temperature inside the housing 11 rises to the melting point of the insulating heat insulation element 14, the paraffin wax of the insulating heat insulation element 14 melts, and the liquid phase of the paraffin wax penetrates into the electrode assembly 12, forming a non-conductive barrier on the surface of the positive electrode and / or the surface of the negative electrode.

[0151] In one embodiment, the total thickness of the insulating and heat-insulating element 14 is 1µm to 15µm. The total thickness of the insulating and heat-insulating element 14 refers to the sum of the thicknesses of all the insulating and heat-insulating elements 14 in a single battery cell 1. For example, the total thickness of the insulating and heat-insulating element 14 may be 1µm, 2µm, 3µm, 5µm, 8µm, 10µm, 12µm, 14µm, or 15µm, etc. This design, to a certain extent, avoids excessively increasing the thickness of the battery cell 1.

[0152] The number of insulating and heat-insulating elements 14 can be one or at least two, for example, two, three, four or five, etc.

[0153] In one embodiment, please refer to Figure 5 The battery cell 1 includes four electrode assemblies 12 and five insulating heat insulation components 14, with one electrode assembly 12 disposed between two adjacent insulating heat insulation components 14. For example, the total thickness of the five insulating heat insulation components 14 can be from 1µm to 15µm.

[0154] In one embodiment, please refer to Figure 6 The cell unit 1 includes four electrode assemblies 12 and five insulating and heat-insulating components 14. The five insulating and heat-insulating components 14 are stacked along the thickness direction, and the four electrode assemblies 12 are distributed in pairs on both sides of the five insulating and heat-insulating components 14 along the thickness direction. For example, the total thickness of the five insulating and heat-insulating components 14 can be from 1 μm to 15 μm.

[0155] In one embodiment, the insulating heat insulation element 14 can be in the form of a flat plate. Thus, the flat plate structure of the insulating heat insulation element 14 is easy to mold and can better fit the electrode assembly 12.

[0156] In some embodiments, the thickness of each insulating heat insulation element 14 is equal.

[0157] In some embodiments, at least two insulating elements 14 have unequal thicknesses. For example, there are three insulating elements 14, two of which have equal thicknesses and are unequal in thickness to the third insulating element 14.

[0158] In one embodiment, the percentage of oxygen released by the positive electrode to the mass of the positive electrode active layer is no more than 0.5 wt%. For example, the oxygen release from the positive electrode can be 0.5 wt%, 0.4 wt%, or 0 wt%, etc. The lower the oxygen release from the positive electrode, the less oxygen is released. Thus, in the event of thermal runaway in the battery 100, there is insufficient oxygen inside the casing 11 to support combustion, thereby preventing open flames or heat spread within the casing 11 to some extent and mitigating the degree of failure as much as possible.

[0159] Oxygen release rate refers to the percentage of oxygen released by the positive electrode to the mass of the positive electrode active layer. The oxygen release rate of the positive electrode can be determined using methods known in the art. For example, a thermal analysis and mass spectrometry (TAMS) instrument can be used, and the testing method can refer to standards JYT014-1996 and GB / T 6041-2002. For instance, within a temperature range of 45°C to 600°C, with a heating rate of 10 K / min, in an Ar atmosphere, the oxygen release rate of the positive electrode can be obtained by accumulating the mass of oxygen using the aforementioned measuring equipment.

[0160] In one embodiment, the positive electrode sheet includes a positive electrode active layer, the material of which includes at least one of polyanionic, Prussian, and modified polyanionic and modified Prussian materials. That is, the material of the positive electrode active layer includes at least one of polyanionic, Prussian, modified polyanionic, and modified Prussian materials. These materials have the characteristic of low or no oxygen release.

[0161] In one embodiment, the positive electrode active layer is made of at least one of NaFePO4, NaMnPO4, NaCoPO4, Na4Fe3(PO4)2O7, Na3V2(PO4)2F3, Na3V2(PO4)3, Prussian blue, Prussian white, and modified forms of each material. For example, the positive electrode active layer is made of at least one of NaFePO4, NaMnPO4, NaCoPO4, Na4Fe3(PO4)2O7, Na3V2(PO4)2F3, Na3V2(PO4)3, Prussian blue, and Prussian white. The above materials have the characteristic of low or no oxygen release, with an oxygen release of no more than 0.5 wt%.

[0162] In some embodiments, the material of the positive electrode active layer may include at least one modified material such as NaFePO4, NaMnPO4, NaCoPO4, Na4Fe3(PO4)2O7, Na3V2(PO4)2F3, Na3V2(PO4)3, Prussian blue, and Prussian white. It may be a doping or coating of these materials. The above materials are stable and release virtually no oxygen or only trace amounts of oxygen.

[0163] In one embodiment, the thermal runaway temperature of the battery cell 1 is not less than 220°C. For example, the thermal runaway temperature of the battery cell 1 is 220°C, 230°C, or 250°C, etc.

[0164] In this embodiment, the thermal runaway temperature of the battery cell 1 is relatively high, resulting in a low risk of thermal runaway and high safety.

[0165] In one embodiment, please refer to Figures 7 to 9 ,as well as Figure 11 The battery 100 includes a second battery cell 2, and the second battery cell 2 and the first battery cell 1 are stacked along a first direction to form a component of the cell unit 10. The thermal runaway temperature of the second battery cell 2 is not greater than 180°C.

[0166] The stacking of the second battery cell 2 and the first battery cell 1 along the first direction means that the large surface of both the second battery cell 2 and the first battery cell 1 intersects the first direction, and the large surface of the second battery cell 2 and the large surface of the first battery cell 1 are approximately parallel. For example, the large surface of the first battery cell 1 is perpendicular to the first direction, and the large surface of the second battery cell 2 is also perpendicular to the first direction. For example, the first direction can be consistent with the thickness direction of the negative electrode current collector 121.

[0167] Thermal runaway temperature refers to the temperature at which the cell's temperature rise rate is not less than 60℃ / min.

[0168] The thermal runaway temperature of the second battery cell 2 is no greater than 180°C. For example, the thermal runaway temperature of the second battery cell 2 can be 180°C, 170°C, or 160°C, etc.

[0169] In this embodiment, the single-cell unit 10 includes different types of second battery cells 2 and first battery cells 1. The second battery cells 2 can be used to increase the energy density of the battery 100, and the first battery cells 1 can serve as a safety cell. In the event of thermal runaway of the second battery cells 2, the first battery cells 1 can isolate the second battery cells 2, prevent heat propagation, and improve the safety performance of the battery 100. Using the first battery cells 1 as a heat insulation structure can also reduce the amount of heat insulation structure used and improve the utilization rate of space inside the casing. The combined use of the second battery cells 2 and the first battery cells 1 can meet both safety and energy density requirements.

[0170] It is understandable that both the second battery cell 2 and the first battery cell 1 are battery cells.

[0171] Thermal runaway temperature can be tested using methods known in the art. For example, it can be tested using an adiabatic accelerating rate calorimeter (ARC test). Test conditions: During the experiment, the prepared sample and container are heated to a pre-set initial temperature under adiabatic conditions and allowed to standby for a certain period (usually 5 to 10 minutes) to reach thermal equilibrium. The self-reaction heat release rate is then observed to see if it exceeds a set value (usually 0.02℃ / min). If no heat release is detected, the sample temperature is increased by a step, typically 5℃-10℃, and the heat release is checked again after the same standby time (usually 5 to 10 minutes). This step-by-step test is repeated several times. Once heat release is detected, the experimental system automatically enters strict adiabatic control and records data such as time, temperature, heat release rate, and pressure at specified time intervals. The temperature at which the cell's temperature rise rate is not less than 60℃ / min is the thermal runaway temperature.

[0172] In one embodiment, please refer to Figures 7 to 9 The single cell unit 10 includes a heat insulation pad 3 and at least two second battery cells 2, with at least one heat insulation pad 3 disposed between two adjacent second battery cells 2.

[0173] For example, in one embodiment, a heat insulation pad 3 is disposed between two adjacent second battery cells 2. In another embodiment, two or more heat insulation pads 3 are disposed between two adjacent second battery cells 2.

[0174] In this embodiment, heat transfer between two adjacent second battery cells 2 can be blocked or delayed by a heat insulation pad 3, thereby achieving the effect of suppressing heat spread between multiple cells.

[0175] In one embodiment, in a single cell unit 10, all second battery cells 2 are sequentially arranged along a first direction to form components of a battery pack, and at least one first battery cell 1 is respectively arranged at both ends of the battery pack along the first direction. A heat insulation pad 3 is provided between two adjacent second battery cells 2. The first battery cells 1 have higher safety and can reduce heat transfer between the battery cell and the casing.

[0176] In one embodiment, please refer to Figure 7 Each cell unit 10 includes five second battery cells 2 and one first battery cell 1. The five second battery cells 2 are arranged sequentially, with a heat insulation pad 3 placed between two adjacent second battery cells 2. There is no heat insulation pad 3 between adjacent second battery cells 2 and first battery cells 1. Thus, the entire cell unit 10 can use four heat insulation pads 3. This improves the utilization rate of the internal space, allowing more battery cells to be placed without increasing the internal space, thereby increasing the energy density.

[0177] In one embodiment, please refer to Figure 8 The single-cell unit 10 includes three second battery cells 2 and two first battery cells 1. The three second battery cells 2 are arranged sequentially, with one first battery cell 1 positioned between two adjacent second battery cells 2, and the other first battery cell 1 positioned at any end of the single-cell unit 10 along a first direction. A heat-insulating pad 3 is positioned between two adjacent second battery cells 2. There is no heat-insulating pad 3 between adjacent second battery cells 2 and first battery cells 1. Thus, the entire single-cell unit 10 can use only one heat-insulating pad 3.

[0178] In one embodiment, in the single-cell unit 10, the first battery cell 1 and the second battery cell 2 are alternately arranged along a first direction. That is, two adjacent second battery cells 2 in the first direction are arranged with one first battery cell 1. In this way, the entire single-cell unit 10 can be completed without the use of the heat insulation pad 3, making greater use of the space inside the casing and improving the energy density of the battery.

[0179] In one embodiment, please refer to Figure 9 The single-cell unit 10 includes two second battery cells 2 and three first battery cells 1, which are arranged sequentially. A second battery cell 2 is placed between any two adjacent first battery cells 1. There is no heat insulation pad 3 between adjacent second battery cells 2 and first battery cells 1. Thus, the entire single-cell unit 10 does not require a heat insulation pad 3.

[0180] In one embodiment, in a single cell 10, the ratio of the number of second battery cells 2 to the number of first battery cells 1 is 0.5:1 to 5:1. In some embodiments, the ratio of the number of second battery cells 2 to the number of first battery cells 1 is 0.5:1 to 4:3. Exemplary examples include ratios of 0.5:1, 3:1, 4:3, or 5:1.

[0181] In one specific embodiment, the ratio of the number of second battery cells 2 to the number of first battery cells 1 is 1:1, and the number of second battery cells 2 and first battery cells 1 are arranged alternately along a first direction. A heat insulation pad 3 may not be provided between adjacent second battery cells 2 and first battery cells 1. Thus, the entire cell unit 10 can be without a heat insulation pad 3, resulting in a more compact structure. More second battery cells 2 and first battery cells 1 can be placed inside the housing, increasing battery capacity.

[0182] In this embodiment, by adopting the above ratio, the production cost of the second battery cell 2 can be saved, the total heat generated by all the second battery cells 2 in the cell unit 10 can be controlled, the heat generated per unit of the cell unit 10 is relatively small, the number of first battery cells 1 can improve the reliability of suppressing heat spread, reduce the amount of heat insulation structure such as heat insulation pad 3, save heat insulation structure such as heat insulation pad 3, and increase the capacity of battery 100.

[0183] In some embodiments, the heat insulation pad 3 may be generally flat.

[0184] In some embodiments, the thickness of each heat insulation pad 3 is equal.

[0185] In some embodiments, at least two of the heat insulation pads 3 have unequal thicknesses. For example, there are three heat insulation pads 3, two of which have equal thicknesses and are unequal in thickness to the third heat insulation pad 3.

[0186] In one embodiment, the second battery cell 2 is a lithium-ion battery cell or a lithium metal battery cell.

[0187] In this embodiment, both lithium-ion battery cells and lithium metal battery cells rely on the reciprocating insertion and extraction of lithium ions between the positive and negative electrodes to achieve charging and discharging. The lithium metal battery cell uses lithium metal as the negative electrode active layer, which can be formed after the first charge and discharge cycle. Lithium-ion batteries and lithium metal batteries have the characteristics of low production cost and relatively high energy density.

[0188] In one embodiment, the second battery cell 2 includes a positive electrode active material layer, the material of which includes at least one of nickel-cobalt-manganese ternary materials, lithium manganese oxide, lithium iron phosphate, and lithium manganese iron phosphate. These materials have relatively low cost and relatively high energy density. The nickel-cobalt-manganese ternary material can be lithium nickel-cobalt-manganese oxide.

[0189] For example, nickel-cobalt-manganese ternary materials can be high-nickel ternary materials or medium-low nickel ternary materials.

[0190] High nickel content can be defined as a ratio of nickel content to the total mass of the positive electrode active material layer of not less than 80%.

[0191] Medium-low nickel ternary cathodes can be defined as cathodes where the ratio of nickel content to the total mass of the positive electrode active material layer is less than 80%.

[0192] In one embodiment, the second battery cell 2 includes a housing, an electrode assembly, and a first electrolyte. Both the electrode assembly and the first electrolyte are located within the housing.

[0193] The electrode assembly is the energy storage structure of the second battery cell 2.

[0194] The electrode assembly includes a positive electrode, a negative electrode, and a separator, with at least one separator disposed between adjacent positive and negative electrodes. The separator, disposed between the positive and negative electrodes, serves to prevent short circuits.

[0195] The positive electrode includes a positive current collector substrate and a positive active material layer, wherein the positive active material layer is attached to at least one surface of the positive current collector substrate along the thickness direction.

[0196] For example, the positive electrode current collector substrate has two opposing surfaces along its thickness direction, and a positive electrode active material layer is disposed on either or both of the two opposing surfaces along the thickness direction. In one embodiment, the positive electrode active material layer is disposed on one surface of the positive electrode current collector substrate along the thickness direction. In another embodiment, the positive electrode active material layers are disposed on both surfaces of the positive electrode current collector substrate along the thickness direction.

[0197] The negative electrode sheet includes a negative current collector substrate and a negative active material layer, wherein the negative active material layer is attached to at least one surface of the negative current collector substrate along the thickness direction.

[0198] For example, the negative electrode current collector has two opposing surfaces along its thickness direction, and a negative electrode active material layer is disposed on either or both of the two opposing surfaces along the thickness direction. In one embodiment, the negative electrode active material layer is disposed on one surface of the negative electrode current collector along the thickness direction. In another embodiment, the negative electrode active material layers are disposed on both surfaces of the negative electrode current collector along the thickness direction.

[0199] In this embodiment, the first active ions in the first electrolyte migrate between the positive electrode active material layer and the negative electrode active material layer, achieving charging and discharging. The separator allows the first active ions to pass through.

[0200] In some embodiments, the second battery cell 2 includes an electrode assembly. In other embodiments, the second battery cell 2 includes at least two electrode assemblies, which may be stacked along a first direction.

[0201] In one embodiment, the positive electrode has a first positive tab and the negative electrode has a first negative tab, which can draw current from the electrode assembly.

[0202] In some embodiments, the electrode assembly is a wound structure. Exemplarily, the positive electrode, negative electrode, and separator are wound into a wound structure.

[0203] In some embodiments, the electrode assembly is a stacked structure.

[0204] For example, there are at least two positive electrode plates, at least two negative electrode plates, and at least two separators. Multiple positive electrode plates and multiple negative electrode plates are stacked alternately, and a separator is disposed between adjacent positive electrode plates and negative electrode plates to form a stacked structure.

[0205] For example, multiple positive electrode sheets can be provided, and negative electrode sheets are folded to form multiple stacked folded segments, with a positive electrode sheet sandwiched between adjacent folded segments to form a stacked structure.

[0206] For example, both the positive and negative electrode sheets are folded to form multiple stacked folded segments, which are alternately nested to form a stacked structure.

[0207] In one embodiment, the battery cell 1 includes a second electrolyte located within the casing 11. The positive electrode includes a positive current collector, and a positive active layer is attached to at least one surface of the positive current collector. Second active ions in the second electrolyte migrate between the positive and negative active layers, enabling charging and discharging. A separator allows the second active ions to pass through.

[0208] In one embodiment, the positive electrode is provided with a second positive tab and the negative electrode is provided with a second negative tab. The second positive tab and the second negative tab can conduct current from the electrode assembly 12.

[0209] In some embodiments, the electrode assembly 12 is a wound structure. Exemplarily, the positive electrode, negative electrode, and separator are wound into a wound structure.

[0210] In some embodiments, the electrode assembly 12 has a stacked structure.

[0211] For example, there are at least two positive electrode plates, at least two negative electrode plates, and at least two separators. Multiple positive electrode plates and multiple negative electrode plates are stacked alternately, and a separator is disposed between adjacent positive electrode plates and negative electrode plates to form a stacked structure.

[0212] For example, multiple positive electrode sheets can be provided, and negative electrode sheets can be folded to form multiple stacked folded segments, with a positive electrode sheet sandwiched between adjacent folded segments to form a stacked structure.

[0213] For example, both the positive and negative electrode sheets are folded to form multiple stacked folded segments, which are nested alternately to form a stacked structure.

[0214] The shell is a hollow structure, with an internal cavity for accommodating the electrode assembly and the first electrolyte. The shell can be of various shapes, such as a cuboid.

[0215] The outer shell 11 has a hollow structure, and its interior forms a space for accommodating the electrode assembly 12 and the second electrolyte. The outer shell 11 can be of various shapes, such as a cuboid.

[0216] In some embodiments, the housing may be a rigid structure; for example, the housing may be made of rigid materials such as aluminum and / or steel.

[0217] In some embodiments, the housing includes a body and a cover. The body may be a hollow structure with an opening at one end, and the cover closes the opening at one end of the body. Thus, the cover and the body together define a receiving cavity.

[0218] In some embodiments, the cover may be equipped with a balancing valve. The balancing valve can pre-vent some of the gas in the containment cavity, which helps with heat dissipation and prevents the accumulation of flammable gases at high temperatures, thereby increasing the heat resistance temperature range.

[0219] In some embodiments, the housing 11 may be a rigid structure; for example, the housing 11 may be made of rigid materials such as aluminum and / or steel.

[0220] In some embodiments, the housing 11 includes a bottom shell and a top cover. The bottom shell may be a hollow structure with an opening at one end, and the top cover closes the opening at one end of the bottom shell. Thus, the top cover and the bottom shell together define an accommodating space.

[0221] In some embodiments, the top cover may be equipped with a balancing valve. The balancing valve can pre-vent some of the gas in the containment space, which helps with heat dissipation and prevents the accumulation of flammable gases at high temperatures, thereby increasing the heat resistance temperature range.

[0222] Balance valves include, but are not limited to, vent valves or explosion-proof valves. Balance valves can be one-way valves. A one-way valve on the cover can restrict the airflow from the containment cavity to the outside in one direction. A one-way valve on the top cover can also restrict the airflow from the containment space to the outside in one direction.

[0223] In some embodiments, both the positive electrode current collector substrate and the positive electrode current collector can be metal foil or composite current collector. The metal foil can be aluminum, silver-treated aluminum, or stainless steel, etc. The composite current collector may include a polymer base layer and a metal layer. The metal layer can be aluminum, aluminum alloy, or nickel, etc. The polymer base layer can be polypropylene, polyethylene terephthalate, or polyethylene, etc.

[0224] It should be noted that the positive current collector substrate and the positive current collector can be made of the same material or different materials.

[0225] In some embodiments, both the negative electrode current collector substrate and the negative electrode current collector 121 can be made of metal foil or a composite current collector. The metal foil can be made of copper or nickel, etc. The composite current collector may include a polymer material substrate and a metal layer. The metal layer can be made of copper or nickel, etc. The polymer material substrate can be made of polypropylene, polyethylene terephthalate, or polyethylene, etc.

[0226] It should be noted that the negative electrode current collector substrate and the negative electrode current collector 121 can be made of the same material or different materials.

[0227] Both the second battery cell 2 and the battery cell 1 can be a secondary battery 100. A secondary battery 100 refers to a cell that can be used again after being discharged because the active materials can be activated by charging.

[0228] For example, battery cell 1 and battery cell 2 in battery 100 can be connected in series, in parallel, or in a mixed manner. A mixed connection means that battery cell 1 and battery cell 2 are connected in both series and parallel. Battery cell 1 and battery cell 2 can be directly connected in series, in parallel, or in a mixed manner; of course, battery cell 1 and battery cell 2 can also be first connected in series, in parallel, or in a mixed manner to form a battery group of 100, and then the battery group of 100 can be connected in series, in parallel, or in a mixed manner to form a whole.

[0229] The battery 100 may also include other structures, for example, the battery 100 may also include a busbar for realizing an electrical connection between the battery cell 1 and the second battery cell 2.

[0230] In some embodiments, the battery 100 includes a single cell 10.

[0231] In some embodiments, the battery 100 includes at least two individual cells 10; the at least two individual cells 10 may be stacked along a third direction. Alternatively, the at least two individual cells 10 may be laid flat along a second direction. Alternatively, multiple individual cells 10 may be laid flat along the second direction to form a layer, and multiple layers of individual cells 10 may be stacked along a third direction.

[0232] In one exemplary embodiment, the negative electrode active layer of battery cell 1 is made of sodium metal, and the separator is made of PP or PE. The thermal runaway temperature of the second battery cell 2 is no greater than 180°C. The second battery cell 2 is a lithium-ion battery 100, meaning that the first active ion of the second battery cell 2 is lithium ion. The second battery cell 2 and the battery cell 1 are stacked along a first direction to form a single cell unit 10.

[0233] In this embodiment, on the one hand, the melting point of the negative electrode active layer is lower than the thermal shrinkage temperature of the separator. When the temperature inside the shell 11 rises, due to the relatively low melting point of the negative electrode active layer, the temperature inside the shell 11 will reach the melting point of the negative electrode active layer first, causing local melting of the negative electrode active layer. The local melting of the negative electrode active layer breaks off and separates from the negative electrode sheet to form a separate body. The separate body separates from the negative electrode sheet and cannot spread rapidly to the remaining negative electrode active layer of the negative electrode sheet in a solid contact manner. In other words, the negative electrode sheet undergoes local melting to inhibit the continued thermal spread on the negative electrode sheet. The negative electrode active layer absorbs heat during the melting process, which can delay or inhibit the continued rise of the temperature inside the shell 11 to a certain extent, thereby preventing the continuous occurrence of internal thermal spread. The local phase change of the negative electrode active layer can inhibit the temperature rise inside the shell 11. Thus, the temperature inside the shell 11 will be lower than the thermal shrinkage temperature of the separator. In other words, the separator will not undergo thermal shrinkage, reducing the risk of short circuit between the positive and negative electrode sheets, playing a self-protective barrier role, inhibiting thermal spread, and improving the safety performance of the battery cell 1. On the other hand, based on lower heat generation per unit mass and higher specific capacity, battery cell 1 has a lower heat generation capacity for the same capacity. When the second battery cell 2 and the first battery cell 1 are combined, the battery 100 has a wider range of mass energy density and safety performance.

[0234] In some embodiments, the DSC heat generation of the negative electrode of the first battery cell 1 can be 300 J / g to 1200 J / g. In some embodiments, the DSC heat generation of the negative electrode of the second battery cell 2 can be 1500 J / g to 3000 J / g. With this design, the DSC heat generation of the negative electrode of the first battery cell 1 is relatively low, resulting in less heat release and better safety. The second battery cell 2 can be used to meet the requirements of high energy density and low cost in batteries.

[0235] It should be noted that the unit J / g refers to joules per gram. DSC refers to differential scanning calorimetry (DSC). The heat generated by DSC refers to the heat released per unit mass of the negative electrode active layer under a nitrogen atmosphere at 50℃ to 500℃.

[0236] It is understood that the definition of DSC heat generation of the negative electrode of the first battery cell 1 and the definition of DSC heat generation of the negative electrode of the second battery cell 2 are the same, and the same method can be used for measurement. The following explanation uses the DSC heat generation of the negative electrode of the first battery cell 1 as an example. By disassembling the negative electrode of the cell in a fully charged state, the DSC heat generation at the electrode layer is tested to compare the heat release situation, serving as evidence of the cell's safety capability. Methods known in the art can be used for measurement. The national standard GB / T 13464-2008 for measuring DSC heat generation can be referenced. As an example, the DSC heat generation can be tested using the following method:

[0237] Test conditions: Test equipment model: NETZSCH STA449F3; Sample: The negative electrode sheet is punched into a small circular sheet with a diameter of 5mm (the negative electrode sheet includes the negative electrode active layer and the current collector; when calculating the heat release per unit mass, the mass of the current collector needs to be deducted) and 2uL (microliter) of electrolyte is dropped onto the negative electrode sheet; The test start temperature is room temperature, for example, 25℃; The heating rate is 10K / min (Kelvin per minute); The test atmosphere is nitrogen; The sample preparation environment is a glove box.

[0238] Post-test data standard processing: In the DSC test results, the vertical axis represents heat flux in mW / mg (milliwatts per milligram), and the horizontal axis represents temperature in °C. The test data needs to be adjusted by subtracting the baseline of the empty crucible test results; the temperature from 50°C to the end temperature is horizontally adjusted, and after fitting calculation, the DSC heat release of the test sample in a nitrogen atmosphere within the range of 50°C to 500°C is obtained. In this application, thermal spread testing can be performed using methods known in the art. For example, the thermal spread testing of battery 100 can refer to the thermal spread test in Appendix C of GB 38031-2020. Exemplarily, the following test steps can be used:

[0239] S1: Fully charge all test cells (full charge means charging to the nominal voltage using a constant current and constant voltage at a 0.33C rate), arrange and electrically connect the cells into a module, and use end plates and side plates to fix the module or use steel strips to fix the module; select appropriate steel pin size (generally 3mm or 4mm in diameter) or heating plate (generally 500W, the power and size of the heating plate can be adjusted according to the cell capacity and shell size);

[0240] S2: Place the module in a simulated sealed box (the sealed box has explosion-proof function) and monitor the voltage and temperature of each cell;

[0241] S3: Heating plate verification of heat spread: Select a first battery cell 1 adjacent to the second battery cell 2 in the module as the target cell, and place it in close contact with the heating plate. The heating plate is plugged in and heated until the target cell fails (active failure). Stop the needle penetration and observe the heat spread.

[0242] S4: After the target cell fails, stop heating or needle puncture (choose one of the two verification measures), continue to observe the module for two hours to confirm whether the other second battery cells 2 and the other first battery cells 1 on the non-trigger side of the module have thermal propagation (i.e., determine whether the cell has failed); after cooling for 24 hours, perform appearance confirmation and capacity testing on the second battery cells 2 and battery cells 1.

[0243] The criteria for determining heat spread are: confirming whether there is an open flame in other battery cells; if there is no open flame, heat spread has not occurred; if there is an open flame, heat spread has occurred.

[0244] The cell failure criteria are as follows: if any two of the following four conditions are met, the cell is considered to have failed: ① Temperature ≥ 280℃; ② Cell temperature rise rate reaches: dT / dt ≥ 1℃ / s, and lasts for more than 3s; ③ Cell voltage drops by more than 25% of the initial voltage; ④ Cell produces an open flame.

[0245] The above methods can be used to determine whether the battery has experienced thermal propagation or whether the battery cell has failed.

[0246] The following thermal propagation test experiments were conducted using one comparative example and four test cases from this application:

[0247] Table 1

[0248]

[0249]

[0250] It should be noted that the ternary lithium battery cell used in the comparison is a self-made cell, with lithium nickel cobalt manganese oxide as the positive electrode active material and graphite as the negative electrode active material. The output voltage is 3.7V and the capacity is 177Ah.

[0251] Test Examples 1 to 4 of this application:

[0252] The first battery cell is a self-made cell, with the positive electrode active layer made of Na4Fe3(PO4)2O7; the material of the negative electrode active layer is shown in Table 1; the output voltage is 3.0V and the capacity is 130Ah.

[0253] The second battery cell is a self-made cell. The positive electrode active material layer uses lithium nickel cobalt manganese oxide, and the negative electrode active material layer uses graphite. The output voltage is 3.7V and the capacity is 177Ah.

[0254] As shown in Table 1, the comparative example battery consists of a module composed of five ternary lithium battery cells stacked sequentially along the first direction. The melting point of the negative electrode active material layer of the ternary lithium battery cell is higher than the thermal shrinkage temperature of the separator. Any ternary lithium battery between the two ends can be selected as the target cell. The comparative example is subjected to thermal spread test, that is, thermal spread test according to Appendix C of GB38031-2020. The comparative example has thermal spread and the cell has failed.

[0255] As shown in Table 1, in Test Examples 1, 2, 3, and 4 of this application, the second battery cell is a ternary lithium battery cell, and the melting point of the negative electrode active layer of the first battery cell is lower than the thermal shrinkage temperature of the separator. For Test Examples 1 and 2, any one of the five first battery cells 1 was selected as the target cell. For Test Examples 3 and 4, one first battery cell 1 adjacent to the second battery cell 2 in the module was selected as the target cell. Thermal propagation tests were performed on Test Examples 1, 2, 3, and 4, according to Appendix C of GB 38031-2020. No thermal propagation occurred in Test Examples 1, 2, 3, and 4, indicating the cells are effective. Therefore, the first battery cell can act as a self-protective barrier, isolating the second battery cell and suppressing thermal propagation.

[0256] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit it. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application. In particular, as long as there is no structural conflict, the various technical features mentioned in each embodiment can be combined in any way.

Claims

1. A battery cell, characterized in that, include: shell; An electrode assembly is located inside the housing. The electrode assembly includes a negative electrode, a positive electrode, and a separator. At least one separator is disposed between adjacent positive and negative electrode sheets. The negative electrode includes a negative current collector and a negative active layer. The negative active layer is disposed on at least one surface of the negative current collector along the thickness direction. The melting point of the negative active layer is lower than the heat shrinkage temperature of the separator.

2. The battery cell according to claim 1, characterized in that, After the battery cell is charged, the negative electrode active layer is deposited on at least one surface of the negative electrode current collector along the thickness direction.

3. The battery cell according to claim 1 or 2, characterized in that, The material of the negative electrode active layer includes at least one of sodium metal and potassium metal.

4. The battery cell according to any one of claims 1 to 3, characterized in that, The surface of the negative electrode current collector is divided into at least two partition regions, and the negative electrode active layer is present in each partition region.

5. The battery cell according to claim 4, characterized in that, The negative electrode sheet includes a support structure, and the support structure is disposed on at least one surface of the negative electrode current collector along the thickness direction, the support structure dividing the surface of the negative electrode current collector into at least two partition regions.

6. The battery cell according to claim 5, characterized in that, The support structure is formed by printing or etching on the negative electrode current collector.

7. The battery cell according to claim 5 or 6, characterized in that, The support structure includes at least two support bars, and at least a portion of the support bars form a closed area.

8. The battery cell according to any one of claims 5 to 7, characterized in that, The support structure includes a first support bar and a second support bar, which intersect.

9. The battery cell according to claim 8, characterized in that, At least two of the first support bars and at least two of the second support bars are staggered to form a grid-like area.

10. The battery cell according to any one of claims 5 to 9, characterized in that, The negative electrode sheet includes a conductive layer, which is located between the negative electrode current collector and the supporting structure in the thickness direction of the negative electrode current collector.

11. The battery cell according to any one of claims 1 to 10, characterized in that, The battery cell includes a flame-retardant component located inside the casing. The flame-retardant component is disposed on at least one surface of the separator along its thickness direction. The flame-retardant component includes a casing and a flame retardant. The flame retardant is contained within the casing. The melting point of the casing is lower than the heat shrinkage temperature of the separator.

12. The battery cell according to claim 11, characterized in that, The flame-retardant component covers two surfaces of the insulating membrane along its thickness direction.

13. The battery cell according to any one of claims 1 to 12, characterized in that, The battery cell includes an insulating heat insulation component located within the housing, and at least one of the electrode components is provided with the insulating heat insulation component on at least one side along the thickness direction, wherein the melting point of the insulating heat insulation component is lower than the heat shrinkage temperature of the separator.

14. The battery cell according to claim 13, characterized in that, The insulating and heat-insulating component is made of at least one of paraffin wax, polyethylene, polymethyl methacrylate, polyethylene terephthalate, polytetrafluoroethylene, and melamine.

15. The battery cell according to any one of claims 1 to 14, characterized in that, The percentage of oxygen released by the positive electrode to the mass of the positive electrode active layer of the positive electrode is no more than 0.5 wt%.

16. The battery cell according to claim 15, characterized in that, The positive electrode includes a positive electrode active layer, and the material of the positive electrode active layer includes at least one of polyanionic, Prussian, and modified versions of each material.

17. The battery cell according to claim 16, characterized in that, The positive electrode active layer is made of at least one of the following materials: NaFePO4, NaMnPO4, NaCoPO4, Na4Fe3(PO4)2O7, Na3V2(PO4)2F3, Na3V2(PO4)3, Prussian blue, Prussian white, and modifiers of each material.

18. The battery cell according to any one of claims 1 to 17, characterized in that, The thermal runaway temperature of the battery cell is not less than 220°C.

19. A battery, characterized in that, The battery cell described in any one of claims 1 to 18 is used as the first battery cell.

20. The battery according to claim 19, characterized in that, The battery includes a second battery cell, and the second battery cell and the first battery cell are stacked along a first direction to form a component of a single cell unit. The thermal runaway temperature of the second battery cell is not greater than 180°C.

21. The battery according to claim 20, characterized in that, In any one of the said individual cells, the ratio of the number of the second battery cells to the number of the first battery cells is 0.5:1 to 5:

1.

22. The battery according to claim 20 or 21, characterized in that, The single unit includes a heat insulation pad and at least two second battery cells, with at least one heat insulation pad disposed between two adjacent second battery cells.

23. The battery according to any one of claims 20 to 22, characterized in that, The second battery cell includes a positive electrode active material layer, the material of which includes at least one of nickel-cobalt-manganese ternary materials, lithium manganese oxide, lithium iron phosphate, and lithium manganese iron phosphate.

24. An electrical appliance, characterized in that, Includes the battery as described in any one of claims 19 to 23 for providing electrical energy.

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