Battery cell, battery, and electric device

Abstract

The present disclosure relates to the technical field of batteries, and provides a battery cell, a battery, and an electric device. The battery cell comprises a casing and an electrode assembly; the electrode assembly is located in the casing; the electrode assembly comprises a negative electrode sheet, a positive electrode sheet, and a separator; at least one separator is arranged between the positive electrode sheet and the negative electrode sheet which are adjacent to each other; the negative electrode sheet comprises a negative electrode current collector and a negative electrode active layer; at least one surface of the negative electrode current collector in the thickness direction is provided with the negative electrode active layer; and the melting point of the negative electrode active layer is lower than the thermal shrinkage temperature of the separator. The local phase change of the negative electrode active layer can inhibit the temperature rise in the casing. In this way, the temperature in the casing is lower than the thermal shrinkage temperature of the separator. That is, the separator basically does not undergo thermal shrinkage, thereby reducing the risk of short circuit caused by contact between the positive electrode sheet and the negative electrode sheet, providing a self-protection barrier effect, inhibiting thermal spreading, and reducing the risk of thermal spreading.

Description

Battery cell, battery and electric device

[0001] Cross-reference to related applications

[0002] The present disclosure is based on and claims priority to Chinese Patent Application No. 202410992919.7, filed on July 23, 2024, entitled "Battery cell, battery and electric device", the entire contents of which are incorporated herein by reference. TECHNICAL FIELD

[0003] The present disclosure relates to the technical field of batteries, and in particular to a battery cell, a battery and an electric device. BACKGROUND

[0004] Batteries are increasingly widely used in life and production. For example, new energy vehicles equipped with batteries have been widely used, and batteries can be used to provide all or part of power for new energy vehicles.

[0005] In related technologies, if a battery cell of a battery experiences thermal runaway, heat spread is likely to occur, leading to battery failure and affecting the safety of the battery. SUMMARY

[0006] Therefore, embodiments of the present disclosure aim to provide a battery cell, a battery and an electric device that can reduce the risk of heat spread.

[0007] To achieve the above-mentioned purpose, the technical solution of the embodiments of the present disclosure is as follows:

[0008] In a first aspect, the present disclosure provides a battery cell, comprising:

[0009] a housing;

[0010] an electrode assembly located in the housing, the electrode assembly comprising a negative electrode sheet, a positive electrode sheet and a separator film, at least one separator film being arranged between adjacent positive electrode sheets and negative electrode sheets, the negative electrode sheet comprising a negative electrode current collector and a negative electrode active layer, the negative electrode active layer being arranged on at least one surface of the negative electrode current collector in the thickness direction, and the melting point of the negative electrode active layer being lower than the heat shrinkage temperature of the separator film.

[0011] The battery cell provided by the embodiments of the present disclosure has a negative electrode active layer with a melting point lower than the heat shrinkage temperature of the separation film. In this way, when the temperature in the shell rises, the temperature in the shell first reaches the melting point of the negative electrode active layer due to the relatively low melting point of the negative electrode active layer, so that the negative electrode active layer locally melts, and the locally melted negative electrode active layer separates from the negative electrode sheet to become a separator. The separator changes the originally complete negative electrode active material into a scattered point-like distribution, and cannot form a continuous heat conductor, so that heat cannot spread to the remaining negative electrode active layer of the negative electrode sheet in a solid contact manner. In other words, the local melting of the negative electrode sheet can inhibit the continuous heat spread on the negative electrode sheet. In addition, the negative electrode active layer can absorb heat during melting, which can delay or inhibit the continuous rise of the temperature in the shell to a certain extent, so that the continuous heat spread in the shell can be interrupted. The phase change of the negative electrode active layer can inhibit the rise of the temperature in the shell, so that the temperature in the shell is lower than the heat shrinkage temperature of the separation film. In other words, the separation film basically does not shrink, which reduces the risk of contact short circuit between the positive electrode sheet and the negative electrode sheet, plays a self-protection and blocking role, inhibits heat spread, reduces the risk of heat spread, and improves the safety performance of the battery cell.

[0012] In some embodiments, the negative electrode active layer is deposited on at least one surface of the negative electrode current collector in the thickness direction after the battery cell is charged.

[0013] In this embodiment, the negative electrode sheet does not have negative electrode active material before charging, which reduces the mass of the negative electrode sheet and improves the energy density of the battery cell. The surface of the negative electrode current collector is basically free of negative electrode active material before the first charging and discharging, which improves the safety during the battery production and assembly process.

[0014] In some embodiments, the material of the negative electrode active layer includes at least one of sodium metal and potassium metal.

[0015] In this embodiment, the melting point of sodium metal and the melting point of potassium metal are both lower than 100 DEG C, and the sodium metal and the potassium metal also have good energy storage density.

[0016] In some embodiments, the surface of the negative electrode current collector is divided into at least two partition areas, and the negative electrode active layer is arranged in the partition areas.

[0017] In this embodiment, the negative electrode active layer is divided into a plurality of small units, and in the case that the negative electrode active layer in part of the partition areas melts due to the local temperature rise of the negative electrode sheet, heat transfer can be slowed down or inhibited to a certain extent to avoid affecting the negative electrode active layer in other partition areas and reduce the risk of heat spread.

[0018] In some embodiments, the negative electrode sheet includes a support structure, and the negative electrode current collector is provided with the support structure on at least one surface in the thickness direction, and the support structure divides the surface of the negative electrode current collector into at least two partition areas.

[0019] In this embodiment, on the one hand, the support structure can play a role in strengthening the structural strength of the negative current collector, and the support structure can be supported between the negative current collector and the remaining structural layers to play a role in interlayer support; on the other hand, the support structure divides the surface of the negative current collector into at least two partition areas, and the negative active layer is arranged in the partition areas, so that the negative active layer is divided into a plurality of small units, and in the case that the negative active layer in part of the partition areas melts when the local temperature of the negative plate becomes an out-of-control failure point, the support structure can inhibit the further transmission of heat and reduce the risk of heat spread.

[0020] In some embodiments, the support structure is formed by printing or etching on the negative current collector.

[0021] In this embodiment, both the printing process and the etching process are relatively mature, and the manufacturing cost is relatively low, and the yield of the support structure is high.

[0022] In some embodiments, the support structure includes at least two support strips, and at least part of the support strips form a closed area.

[0023] In this embodiment, the partition area as a closed area can block the heat transfer between each partition area as much as possible.

[0024] In some embodiments, the support structure includes a first support strip and a second support strip, and the first support strip and the second support strip intersect.

[0025] In this embodiment, the first support strip and the second support strip can divide the surface of the negative current collector into more partition areas.

[0026] In some embodiments, the at least two first support strips and the at least two second support strips form a grid-shaped area in a staggered manner.

[0027] In this embodiment, the support structure is roughly in a grid-shaped structure, the number of partition areas is larger, and the negative active layer is divided into more modules with smaller individual areas.

[0028] In some embodiments, the negative plate includes a conductive layer, and in the thickness direction of the negative current collector, the conductive layer is located between the negative current collector and the support structure.

[0029] In this embodiment, the conductive layer has a conductive function to provide electron conduction, and the conductive layer can also play a role in interface modification to improve the morphology of the negative active layer, so that the negative active layer is more dense.

[0030] In some embodiments, the battery cell includes a flame retardant member in the housing, and the flame retardant member is arranged on at least one surface of the separator in the thickness direction, the flame retardant member includes a wrapping shell and a flame retardant agent, the flame retardant agent is contained in the wrapping shell, and the melting point of the wrapping shell is less than the heat shrinkage temperature of the separator.

[0031] In this embodiment, the flame retardant is wrapped by the wrapping shell. In the case of normal battery monomer, the flame retardant will not be released. In the case of thermal runaway of the battery monomer and temperature rise in the shell, since the melting point of the wrapping shell is lower than the heat shrinkage temperature of the separation film, the temperature in the shell will first reach the melting point of the wrapping shell, the local part of the wrapping shell will melt to form a gap, and the flame retardant can be released into the shell from the gap to prevent, delay or terminate the flame propagation, and inhibit the occurrence of thermal runaway.

[0032] In some embodiments, the flame retardant covers both surfaces of the separation film along the thickness direction.

[0033] In this embodiment, the flame retardant is laid on the surface of the separation film along the thickness direction to form a flame-retardant layer. This design has better flame-retardant effect.

[0034] In some embodiments, the battery monomer includes an insulating and heat-insulating member in the shell, and at least one electrode assembly is provided with the insulating and heat-insulating member on at least one side along the thickness direction, and the melting point of the insulating and heat-insulating member is lower than the heat shrinkage temperature of the separation film.

[0035] In this embodiment, on the one hand, the insulating and heat-insulating member can bind the electrode assembly to reduce or even eliminate the probability of the electrode assembly shaking in the shell. On the other hand, in the case of thermal runaway in the battery monomer, the insulating and heat-insulating member melts and flows into the electrode assembly, for example, the liquid-phase insulating and heat-insulating member covers the surface of the negative electrode sheet to form an insulating barrier, further isolating the positive electrode sheet and the negative electrode sheet to avoid the risk of short circuit to a certain extent.

[0036] In some embodiments, the material of the insulating and heat-insulating member includes at least one of paraffin, polyethylene, polymethyl acrylate, polyethylene terephthalate, polytetrafluoroethylene and melamine.

[0037] In this embodiment, after the temperature in the shell rises to the melting point of the above-mentioned material, the above-mentioned material melts and penetrates into the electrode assembly to form a non-conductive barrier on the surface of the positive electrode sheet and / or the surface of the negative electrode sheet.

[0038] In some embodiments, the percentage of the amount of oxygen released by the positive electrode sheet to the mass of the positive active layer of the positive electrode sheet is not greater than 0.5wt%.

[0039] In this embodiment, the lower the oxygen release amount of the positive electrode sheet, the less oxygen is released by the positive electrode sheet. In the case of thermal runaway of the battery, there is not enough oxygen to assist combustion in the shell, thereby avoiding the occurrence of open fire or heat spread in the shell to a certain extent and slowing down the failure as much as possible.

[0040] In some embodiments, the positive electrode sheet includes a positive active layer, and the material of the positive active layer includes at least one of polyanion, prussian and modified materials of each material.

[0041] In this embodiment, the material of the positive active layer includes at least one of polyanion, prussian, modified polyanion, and modified prussian. These materials have the characteristics of low oxygen release or no oxygen release.

[0042] In some embodiments, the material of the positive active layer includes at least one of NaFePO4, NaMnPO4, NaCoPO4, Na4Fe3(PO4)2O7, Na3V2(PO4)2F3, Na3V2(PO4)3, Prussian blue, Prussian white, and modified materials of each of the above.

[0043] In this embodiment, the material of the positive active layer has the characteristics of low oxygen release or no oxygen release, and the oxygen release is not more than 0.5% by mass.

[0044] In some embodiments, the thermal runaway temperature of the battery cell is not less than 220°C.

[0045] In this embodiment, the thermal runaway temperature of the battery cell is relatively high, the risk of thermal runaway is low, and the safety is high.

[0046] The second aspect of the embodiments of the present disclosure provides a battery, which includes the battery cell of any one of the above as a first battery cell.

[0047] The battery provided by the embodiments of the present disclosure includes the battery cell of the present disclosure, and has the same or corresponding beneficial effects as the battery cell.

[0048] In some embodiments, the battery includes a second battery cell, the second battery cell and the battery cell are stacked along a first direction to constitute a component of a cell unit, and the thermal runaway temperature of the second battery cell is not more than 180°C.

[0049] In this embodiment, the 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 be used as safety cells. In the case of thermal runaway of the second battery cell, the battery cell can isolate the second battery cell, block the spread of heat, and improve the safety performance of the battery. By using the battery cell as a heat insulation structure, the use amount of the heat insulation structure can be reduced, and the utilization rate of the space in the box can be improved. The combination of the second battery cell and the first battery cell can meet the safety requirement and the energy density requirement.

[0050] In some embodiments, the cell unit includes a heat insulation pad and at least two second battery cells, and at least one heat insulation pad is arranged between the two adjacent second battery cells.

[0051] In this embodiment, the heat transfer between two adjacent second battery cells can be blocked or delayed by the heat insulation pad, so as to achieve the effect of inhibiting heat spread between the plurality of battery cells.

[0052] In some embodiments, the ratio of the number of second battery cells to the number of first battery cells in any one monomer unit is 0.5:1 to 5:1.

[0053] In this embodiment, the second battery cell can save production cost, the total heat generated by all second battery cells in the monomer unit can be controlled, the unit heat generation of the monomer unit is relatively small, the number of battery cells can improve the reliability of inhibiting heat spread, reduce the amount of heat insulation structure such as heat insulation pad, save heat insulation structure such as heat insulation pad, and improve the battery capacity.

[0054] In some embodiments, the second battery cell includes a positive active material layer, and the material of the positive active material layer includes at least one of nickel-cobalt-manganese ternary material, lithium manganate, iron lithium phosphate, and manganese iron lithium phosphate.

[0055] In this embodiment, the above-mentioned material of the positive active material layer has relatively low cost and relatively high energy density.

[0056] The third aspect of the embodiments of the present disclosure provides a power utilization device, which includes the battery of any one of the above.

[0057] The power utilization device provided by the embodiments of the present disclosure includes the battery cell of the present disclosure, and has the same or corresponding beneficial effects as the battery cell. BRIEF DESCRIPTION OF DRAWINGS

[0058] FIG. 1 is a structural schematic diagram of a battery cell in an embodiment of the present disclosure;

[0059] FIG. 2 is a structural schematic diagram of a negative current collector and a first support structure in an embodiment of the present disclosure;

[0060] FIG. 3 is a structural schematic diagram of a negative current collector and a second support structure in an embodiment of the present disclosure;

[0061] FIG. 4 is a structural schematic diagram of a negative current collector and a third support structure in an embodiment of the present disclosure;

[0062] FIG. 5 is a structural schematic diagram of a first electrode assembly and an insulating and heat insulation member in an embodiment of the present disclosure;

[0063] FIG. 6 is a structural schematic diagram of a second electrode assembly and an insulating and heat insulation member in an embodiment of the present disclosure;

[0064] FIG. 7 is a structural schematic diagram of a first monomer unit in an embodiment of the present disclosure;

[0065] FIG. 8 is a structural schematic diagram of a second single unit in an embodiment of the present disclosure;

[0066] FIG. 9 is a structural schematic diagram of a third single unit in an embodiment of the present disclosure;

[0067] FIG. 10 is a structural schematic diagram of a fire retardant in an embodiment of the present disclosure;

[0068] FIG. 11 is a structural schematic diagram of a vehicle in an embodiment of the present disclosure.

[0069] The reference signs explain a vehicle 1000; a battery 100; a controller 200; a motor 300; a single unit 10; a battery cell 1; a casing 11; an electrode assembly 12; a negative electrode current collector 121; a partition 121a; a support structure 122; a first support bar 1221; a second support bar 1222; a fire retardant 13; a wrapping casing 131; a fire retardant 132; an insulating and heat insulating member 14; a second battery cell 2; a heat insulating pad 3. DETAILED DESCRIPTION

[0070] The embodiments of the technical solutions of the present disclosure will be described in detail below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solutions of the present disclosure, and therefore only serve as examples, and cannot limit the protection scope of the present disclosure.

[0071] 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 the present disclosure belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the present disclosure.

[0072] In the description of the embodiments of the present disclosure, the technical terms "first", "second", and the like are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features.

[0073] Reference herein to "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the present disclosure. The appearance of the phrase in various places in the specification does not necessarily all refer to the same embodiment, nor is it necessarily independent or alternative embodiments to other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0074] It should be noted that in the present disclosure, the first direction, the second direction and the third direction are perpendicular to each other, and together constitute a three-dimensional perpendicular coordinate system. At least two includes two and more than two. A plurality of includes two and more than two. The unit "℃" is Celsius. The unit "μm" is micrometer. The unit "K / min" is Kelvin per minute. The unit "℃ / s" is Celsius per second. The unit "s" is second. The unit "℃ / min" is Celsius per minute.

[0075] In the related art, in order to improve the performance of the battery monomer, many improvements have been made to the separator, the negative active layer and the like. For example, in order to improve the power performance of the battery monomer, the porosity of the separator is improved, and the high-porosity separator is used to reduce the internal resistance, thereby improving the power performance. For example, by using amorphous carbon and porous carbon and other materials as the negative active layer to reduce the resistance during charging and discharging, thereby improving the power performance. In order to improve the performance of the battery monomer, such as power performance: using porous carbon negative electrode to speed up ion conduction; improving the storage life or gas production of the battery monomer: using hard carbon / amorphous carbon and other materials to embed active ions into the pore channel, reducing the reaction of metal and electrolyte and the like. That is, in the related art, in order to improve the performance of the battery monomer, improvements have been made to the materials and structures of the separator and the negative active layer. However, the melting point of the negative active layer and the heat shrinkage temperature of the separator have not been concerned. In some cases, in order to improve the performance of the battery monomer, the heat shrinkage temperature of the separator may be reduced and / or the melting point of the negative active layer may be increased, which may cause the melting point of the negative active layer to be higher than the heat shrinkage temperature of the separator, increasing the probability of short circuit between the positive and negative electrodes of the battery monomer, and increasing the risk of thermal runaway of the battery monomer.

[0076] In the related art, when the separator in the battery monomer shrinks due to heat, the positive plate and the negative plate of the battery monomer are in short circuit, and the battery monomer is prone to thermal runaway under the condition of internal short circuit, overheating and the like. In some cases, the active material of the positive plate of the battery monomer releases oxygen at high temperature, which is equivalent to introducing a combustible agent into the originally sealed shell of the battery monomer under failure conditions, intensifying the entire reaction. Under the condition of ignition, the negative plate and the electrolyte in the battery monomer continue to spread heat, and are also prone to spread to other battery monomers that have not occurred thermal runaway, and eventually may cause all battery monomers to occur thermal runaway, causing the risk of battery fire. In the case of using the battery for a vehicle, it may cause the vehicle to catch fire, bringing safety risks.

[0077] The battery monomer provided by the embodiments of the present disclosure includes a shell and an electrode assembly, the electrode assembly is located in the shell, the electrode assembly includes a negative electrode sheet, a positive electrode sheet and a separator, at least one separator is arranged between adjacent positive electrode sheets and negative electrode sheets, the negative electrode sheet includes a negative electrode current collector and a negative electrode active layer, at least one surface of the negative electrode current collector along the thickness direction is provided with the negative electrode active layer, and the melting point of the negative electrode active layer is lower than the heat shrinkage temperature of the separator.

[0078] The melting point of the negative electrode active layer is lower than the heat shrinkage temperature of the separator, and thus, in the case that the temperature in the shell rises, the temperature in the shell will first reach the melting point of the negative electrode active layer due to the relatively low melting point of the negative electrode active layer, so that the local negative electrode active layer melts first, the local negative electrode active layer is fused and separated from the negative electrode sheet to become a separator; the separator changes the originally complete negative electrode active material into a scattered point distribution, cannot form a continuous heat conductor, and heat cannot spread to the remaining negative electrode active layer of the negative electrode sheet in a solid contact manner, that is, the local melting of the negative electrode sheet can inhibit the continuous heat spread on the negative electrode sheet, in addition, the negative electrode active layer can absorb heat during the melting process, and can delay or inhibit the continuous rise of the temperature in the shell to a certain extent, so that the internal heat spread can be disconnected. The phase change of the local negative electrode active layer can inhibit the rise of the temperature in the shell, so that the temperature in the shell is lower than the heat shrinkage temperature of the separator, that is, the separator basically does not shrink, the risk of contact short circuit of the positive electrode sheet and the negative electrode sheet is reduced, the self-protection and blocking effect is achieved, the heat spread is inhibited, the risk of heat spread is reduced, and the safety performance of the battery monomer is improved.

[0079] Referring to FIG. 1 and FIG. 11, the embodiments of the present disclosure provide a battery 100, the battery 100 includes the battery monomer 1 in any one of the embodiments of the present disclosure as a first battery monomer.

[0080] In some embodiments, the battery 100 includes a box body, and the battery monomer 1 is located in the box body. The box body can protect the battery monomer 1, so as to avoid that liquid or other foreign matters affect the charging and discharging of the battery monomer 1.

[0081] For example, the box body can be a sealed box body, so as to have more reliable dustproof and waterproof performance, and thus can be applied to scenes in which the use environment is more severe, humid or even immersed in water.

[0082] Referring to FIG. 11, the embodiments of the present disclosure also provide a power utilization device, the power utilization device includes the battery 100 in any one of the embodiments of the present disclosure for providing electric energy.

[0083] The electric device includes, but is not limited to, a power storage device, a mobile phone, a tablet, a notebook computer, an electric toy, an electric tool, an electric vehicle, an electric automobile, a ship or a spacecraft, etc. The electric toy can include a fixed or mobile electric toy, such as a game console, an electric automobile toy, an electric ship toy, an electric aircraft toy, etc. The spacecraft can include an airplane, a rocket, a space shuttle, a spacecraft, etc.

[0084] In the following embodiments, for the convenience of description, the electric device of an embodiment of the present disclosure is taken as a vehicle 1000 for example. The following is described in conjunction with the drawings.

[0085] FIG. 11 is a structural schematic diagram of the vehicle 1000 provided by some embodiments of the present disclosure. The vehicle 1000 can be a fuel automobile, a gas automobile or a new energy automobile, and the new energy automobile can be a pure electric automobile, a hybrid electric automobile or a range extended automobile, etc. As shown in FIG. 11, the vehicle 1000 is internally provided with a battery 100, which can be arranged at the bottom of the vehicle 1000 or at the front or tail of the vehicle 1000. The battery 100 can be used for power supply of the vehicle 1000, for example, the battery 100 can be used as an operating power supply of the vehicle 1000. The vehicle 1000 can further include a controller 200 and a motor 300, and the controller 200 is used to control the battery 100 to supply power to the motor 300, for example, to meet the working power demand of the vehicle 1000 during starting, navigation and driving.

[0086] In some embodiments of the present disclosure, the battery 100 can not only be used as an operating power supply of the vehicle 1000, but also be used as a driving power supply of the vehicle 1000, to replace or partially replace fuel or natural gas to provide driving power for the vehicle 1000.

[0087] Please refer to FIGS. 1 to 5, the battery monomer 1 provided by the embodiments of the present disclosure includes a shell 11 and an electrode assembly 12.

[0088] Please continue to refer to FIGS. 1 to 5, the electrode assembly 12 is located in the shell 11, and the electrode assembly 12 includes a negative electrode sheet, a positive electrode sheet and a separator film. At least one separator film is arranged between adjacent positive electrode sheets and negative electrode sheets. The negative electrode sheet includes a negative electrode current collector 121 and a negative electrode active layer. The negative electrode current collector 121 is provided with the negative electrode active layer on at least one surface in the thickness direction. The melting point of the negative electrode active layer is lower than the thermal shrinkage temperature of the separator film.

[0089] The electrode assembly 12 is an energy storage structure of the battery monomer 1.

[0090] At least one separator film is arranged between adjacent positive electrode sheets and negative electrode sheets. The separator film arranged between the positive electrode sheet and the negative electrode sheet can prevent short circuit.

[0091] Exemplarily, the negative current collector 121 has two surfaces opposite along a thickness direction of the negative current collector 121, and the negative active layer is arranged on any one or both of the two surfaces of the negative current collector 121 along the thickness direction. In an embodiment, the negative active layer is arranged on one surface of the negative current collector 121 along the thickness direction. In another embodiment, the negative active layer is arranged on both surfaces of the negative current collector 121 along the thickness direction.

[0092] The melting point of the negative active layer refers to a temperature at which the negative active layer changes from a solid state to a liquid state.

[0093] The heat shrinkage temperature of the separator film refers to a temperature at which the separator film shrinks under heat.

[0094] The battery monomer 1 provided by the embodiments of the present disclosure has a melting point of the negative active layer lower than the heat shrinkage temperature of the separator film. In this way, when the temperature in the shell 11 rises, the temperature in the shell 11 first reaches the melting point of the negative active layer due to the relatively low melting point of the negative active layer, so that the negative active layer locally melts, the local melting of the negative active layer breaks and separates from the negative plate to become a separated body; the separated body changes the originally complete negative active material into a scattered point-like distribution, and cannot form a continuous heat conductor, so that heat cannot spread to the remaining negative active layer of the negative plate in a solid contact manner. In other words, the local melting of the negative plate inhibits the continuous heat spreading on the negative plate. In addition, the negative active layer absorbs heat during the melting process, which can delay or inhibit the temperature in the shell 11 from rising, so that the internal heat spreading is interrupted. The phase change of the local negative active layer can inhibit the temperature rise in the shell 11, so that the temperature in the shell 11 is lower than the heat shrinkage temperature of the separator film, that is, the separator film basically does not shrink under heat, thereby reducing the risk of short circuit between the positive plate and the negative plate, playing a self-protection and blocking role, inhibiting heat spreading, and improving the safety performance of the battery monomer 1.

[0095] It should be noted that the melting point is a meaning known in the art, and can be measured by a method and an instrument known in the art. For example, in a heat flow-temperature change diagram, the peak temperature of a DSC curve is the melting point. The melting point of a substance can be tested according to ASTM_D3418-2015.

[0096] It should be noted that the heat shrinkage temperature of the isolation film can be determined in the following manner: a plurality of isolation film samples of a set size are placed in a vacuum oven at different set temperatures (starting from 100°C, increasing the temperature by 5°C intervals), and the temperature is kept constant for 2 hours (h). The shrinkage size of the isolation film after constant temperature is tested. The number of isolation film samples is ≥5, the maximum and minimum values are removed to reduce errors, and the average value (for example, the arithmetic mean) of the remaining number of isolation film samples is calculated. For example, if the number of isolation film samples is 5, the maximum and minimum values are removed to reduce errors, and the average value (for example, the arithmetic mean) of the remaining 3 isolation film samples is calculated. The shrinkage size of the isolation film can be obtained by the above method, and the heat shrinkage ratios of the length direction and the width direction of the isolation film meet the set conditions, and the corresponding temperature is the heat shrinkage temperature of the isolation film. The set conditions include: the heat shrinkage ratio of the length direction reaches 5.0%, and the heat shrinkage ratio of the width direction reaches 3.0%. The heat shrinkage ratio of the length direction refers to the ratio of the shrinkage size of the length direction of the isolation film after constant temperature to the set size of the length direction. The heat shrinkage ratio of the width direction refers to the ratio of the shrinkage size of the width direction of the isolation film after constant temperature to the set size of the width direction.

[0097] In an embodiment, the negative active layer is deposited on at least one surface of the negative current collector 121 in the thickness direction after the battery cell 1 is charged. That is, before the first charge and discharge, there is essentially no negative active layer on the negative current collector 121, and the battery cell 1 is generally referred to as a negative electrode-free battery cell 1.

[0098] For example, during the charging process of the battery cell 1, the second active ions of the battery cell 1 combine with electrons on the surface of the negative current collector 121 to form a negative active layer through deposition behavior. Since the negative plate has no negative active material before charging, the mass of the negative plate is reduced, and the energy density of the battery cell 1 is improved. The surface of the negative plate has essentially no active material before the first charge and discharge, which improves the safety during the production and assembly process of the battery 100.

[0099] In an embodiment, the cohesion of the liquid-phase negative active layer is relatively large at normal temperature and pressure, for example, the cohesion of the liquid-phase negative active layer is greater than the adhesion of the liquid-phase negative active layer on the surface of the isolation film. Normal temperature can be -20°C to 50°C, and normal pressure can be one atmosphere. During the melting process of the negative active layer, the local negative active layer is fused and separated from the negative plate, and the liquid-phase negative active layer separated from the negative plate agglomerates into a separate body, for example, the liquid-phase negative active layer separated from the negative plate agglomerates and disperses into a block-shaped or spherical solid separate body. The liquid-phase negative active layer separated from the negative plate does not substantially infiltrate the isolation film, and the agglomerated separate body cannot cause heat spread on the remaining negative plate in a solid contact manner.

[0100] In an embodiment, the melting point of the negative active layer can be no greater than 100°C. The melting point of the negative active layer is relatively low, and the negative active layer melts locally to break and inhibit heat spread when thermal runaway occurs, thereby playing a self-protective barrier role.

[0101] In an embodiment, the material of the negative active layer can be a metal. For example, the material of the negative active layer can be a metal with a melting point of no greater than 100°C.

[0102] For example, in an embodiment, the material of the negative active layer includes at least one of sodium metal and potassium metal. The melting point of sodium metal and the melting point of potassium metal are both less than 100°C, and they also have good energy storage density.

[0103] In an embodiment, the surface of the negative current collector 121 is divided into at least two division areas 121a, and the negative active layer is in the division areas 121a. In this way, the negative active layer is divided into multiple small units, and in the case that the negative active layer in part of the division areas 121a melts, heat transfer can be slowed down or inhibited, so as to avoid affecting the negative active layer in other division areas 121a to some extent and reduce the risk of heat spread.

[0104] In an embodiment, the surface of the negative current collector 121 can be formed with a groove to divide it into at least two division areas 121a. The formation of the groove is not limited, and for example, part of the material on the surface of the negative current collector 121 can be removed by etching to form the groove.

[0105] In an embodiment, referring to FIGS. 2 to 4, the negative electrode sheet includes a support structure 122, and the negative current collector 121 is provided with the support structure 122 on at least one surface in the thickness direction.

[0106] The support structure 122 divides the surface of the negative current collector 121 into at least two division areas 121a.

[0107] For example, either one or both of the two opposite surfaces of the negative current collector 121 in the thickness direction is / are provided with the support structure 122. In an embodiment, one surface of the negative current collector 121 in the thickness direction is provided with the support structure 122. In another embodiment, both surfaces of the negative current collector 121 in the thickness direction are provided with the support structure 122.

[0108] The support structure 122 can protrude from at least one surface of the negative current collector 121 in the thickness direction. That is, the support structure 122 is a structure added to at least one surface of the negative current collector 121 in the thickness direction.

[0109] In this embodiment, on one hand, the support layer support structure 122 can play a role in strengthening the structural strength of the negative electrode current collector 121, and the support layer support structure 122 can be supported between the negative electrode current collector 121 and the remaining structural layers, playing a role in interlayer support; on the other hand, the support structure 122 divides the surface of the negative electrode current collector 121 into at least two partition areas 121a, and the partition areas 121a have negative electrode active layers therein, so that the negative electrode active layers are divided into multiple small units, and in the case that the negative electrode active layers in part of the partition areas 121a melt when the local temperature of the negative electrode sheet becomes an out-of-control failure point, the support structure 122 can inhibit further heat transfer and reduce the risk of heat spread.

[0110] In one embodiment, referring to FIGS. 2 and 3, the support structure 122 includes at least two support bars, and at least part of the support bars form closed areas. For example, all of the support bars can form closed areas. For another example, part of the support bars can form closed areas. In some embodiments, at least part of the support bars extend to the edge line of the negative electrode current collector 121, and the support bars and the edge line of the negative electrode current collector 121 together define the partition areas 121a as closed areas. In some embodiments, the support bars are connected to each other to form closed areas, and the partition areas defined by the support bars together are closed areas. As closed areas, the partition areas 121a can block heat transfer between the partition areas as much as possible.

[0111] In one embodiment, referring to FIGS. 2 and 3, the support structure 122 includes at least two first support bars 1221 distributed at intervals, and each first support bar 1221 extends in parallel. The parallel extension of each first support bar 1221 means that each first support bar 1221 is substantially parallel, so that the surface of the negative electrode current collector 121 at the part between adjacent two first support bars 1221 can be a partition area 121a.

[0112] It can be understood that the support bars include the first support bars 1221, that is, the first support bars 1221 are one of the support bars. The support bars include the second support bars 1222, that is, the second support bars 1222 are one of the support bars.

[0113] In one embodiment, the interval between any adjacent two first support bars 1221 can be equal or unequal.

[0114] The extension direction of the first support bars 1221 is not limited. For example, in one embodiment, referring to FIG. 3, the first support bars 1221 extend along the length direction of the negative electrode current collector 121. In another embodiment, the first support bars 1221 can also extend along a direction intersecting the length direction, for example, referring to FIG. 2, the first support bars 1221 extend along the width direction of the negative electrode current collector 121. In some embodiments, the first support bars 1221 can extend to the edge of the negative electrode current collector 121.

[0115] The shape of the first support bar 1221 is not limited, and the first support bar 1221 can extend along a straight line, or the first support bar 1221 can also extend along a curve. In an embodiment, referring to FIG. 4, the support structure 122 includes the first support bar 1221 and the second support bar 1222, and the first support bar 1221 and the second support bar 1222 intersect. Specifically, the intersection of the first support bar 1221 and the second support bar 1222 is located on the surface of the negative current collector 121. In this way, the first support bar 1221 and the second support bar 1222 can divide the surface of the negative current collector 121 into more division areas 121a.

[0116] In an embodiment, referring to FIG. 4, the at least two first support bars 1221 and the at least two second support bars 1222 stagger to form a grid-shaped region. In this way, the support structure 122 is roughly in a grid-shaped structure, the number of division areas 121a is more, and the negative active layer is divided into more individual modules with smaller areas.

[0117] It can be understood that, referring to FIG. 4, the support structure 122 is roughly in a grid-shaped structure, and the shape of the division area 121a is not limited. For example, the division area 121a can be in a polygonal shape, a circular shape, an elliptical shape, or an irregular shape, etc. The irregular shape refers to an irregular shape. The polygonal shape includes, but is not limited to, a square shape or a diamond shape, etc.

[0118] For example, in an embodiment, referring to FIG. 4, one of the first support bar 1221 and the second support bar 1222 extends along the length direction of the negative 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 current collector 121.

[0119] The shape of the second support bar 1222 is not limited, and the second support bar 1222 can extend along a straight line, or the second support bar 1222 can also extend along a curve.

[0120] The material of the support structure 122 can be a conductive material or an insulating material. For example, the material of the support structure 122 can be resin and / or a polymer such as polyacrylic acid.

[0121] The manufacturing process of the support structure 122 is not limited, and the support structure 122 is formed by printing or etching on the negative current collector 121. For example, the support structure 122 can be attached to the surface of the negative current collector 121 by processes such as intaglio, 3D printing, or UV printing. The printing process and the etching process are both mature, the manufacturing cost is relatively low, and the yield of the support structure 122 is high.

[0122] In an embodiment, the thickness of the support structure 122 can be 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. In this way, the support structure 122 has good support and is not easily crushed during the shaping of the negative electrode sheet.

[0123] In an 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, in the thickness direction of the negative electrode current collector 121, the negative electrode current collector 121, the conductive layer, and the support structure 122 are sequentially stacked, and the negative electrode active layer can be located on the conductive layer. The conductive layer has a conductive function and provides electron conduction. The conductive layer can also play an interface modification role to improve the morphology of the negative electrode active layer, making the negative electrode active layer more dense.

[0124] The manufacturing process of the conductive layer is not limited. For example, a conductive paste can be coated on the surface of the negative electrode current collector 121 and dried to form.

[0125] It can be understood that, in the case where the surface of the negative electrode current collector 121 is not provided with a conductive layer, the support structure 122 and the negative electrode active layer can be directly arranged on the surface of the negative electrode current collector 121.

[0126] In an embodiment, referring to FIGS. 1 and 10, the battery monomer 1 includes a flame retardant 13 located in the shell 11, and the flame retardant 13 is arranged on at least one surface of the separator in the thickness direction. The flame retardant 13 can play a role in stopping, delaying, or terminating the spread of flame, and inhibiting the continuous occurrence of thermal runaway.

[0127] The flame retardant 13 includes a wrapping shell 131 and a flame retardant 132, and the flame retardant 132 is contained in the wrapping shell 131. The melting point of the wrapping shell 131 is less than the heat shrinkage temperature of the separator.

[0128] The melting point of the wrapping shell 131 refers to the temperature at which the wrapping shell 131 changes from a solid state to a liquid state.

[0129] The flame retardant 132 can play a role in stopping, delaying, or terminating the spread of flame.

[0130] For example, the flame retardant 13 is arranged on either one or both of the two opposite surfaces of the separator in the thickness direction. In an embodiment, the flame retardant 13 is arranged on one surface of the separator in the thickness direction. In another embodiment, the flame retardant 13 is arranged on both surfaces of the separator in the thickness direction.

[0131] In this embodiment, the flame retardant 132 is wrapped by the wrapping shell 131. In the normal case of the battery cell 1, the flame retardant 132 will not be released. In the case of thermal runaway of the battery cell 1, the temperature in the outer shell 11 will first reach the melting point of the wrapping shell 131, because the melting point of the wrapping shell 131 is lower than the heat shrinkage temperature of the separator. The local melting of the wrapping shell 131 will generate a gap, and the flame retardant 132 can be released into the outer shell 11 through the gap, thereby preventing, delaying or terminating the spread of fire and inhibiting the occurrence of thermal runaway.

[0132] The melting point of the wrapping shell 131 can be higher than the melting point of the negative electrode. For example, the melting point of the negative electrode is not greater than 100°C, and the melting point of the wrapping shell 131 can be greater than 100°C.

[0133] The appearance of the wrapping shell 131 is not limited, and for example, in one embodiment, referring to FIG. 10, the wrapping shell 131 can be substantially hollow spherical.

[0134] In one embodiment, the flame retardant 13 covers both surfaces of the separator along the thickness direction. That is, the flame retardant 13 is laid on the surfaces of the separator along the thickness direction to form a flame retardant layer. In this way, the flame retardant effect is better.

[0135] In one embodiment, the shell thickness of the wrapping shell 131 can be 1-10 μm. That is, the shell thickness of the wrapping shell 131 can be 1 μm, 3 μm, 5 μm, 7 μm, 9 μm or 10 μm, etc. In the normal case of the battery cell 1, the strength of the wrapping shell 131 is moderate, which can well protect the flame retardant 132 from leaking; in the case of thermal runaway of the battery cell 1, the melting rate of the wrapping shell 131 is moderate, which can form a gap to release the flame retardant 132 relatively quickly.

[0136] In one embodiment, the diameter of the hollow cavity of the wrapping shell 131 can be 1-20 μm. For example, the diameter of the hollow cavity of the wrapping 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 in the hollow cavity can be 1-20 μm.

[0137] In one embodiment, the thickness of the flame retardant layer can be 3-30 μm. For example, the thickness of the flame retardant layer can be 3 μm, 5 μm, 10 μm, 20 μm or 30 μm, etc. In this way, the mass of the flame retardant 132 can be adapted to the size of the battery cell 1, and the thermal runaway can be more effectively inhibited.

[0138] The material of the flame retardant 132 is not limited, and the material of the flame retardant 132 includes but is not limited to 2,4-dimethyl-6-tert-butyl phenol phosphate (abbreviated as DMTP).

[0139] The material of the wrapping shell 131 is not limited, and the material of the wrapping shell 131 includes but is not limited to polymethyl methacrylate (PMMA).

[0140] The material of the isolation film includes but is not limited to polypropylene (PP) and / or polyethylene (PE), etc.

[0141] In an embodiment, the battery monomer 1 includes a glue layer, which is arranged between the surface of at least one of the flame-retardant member 13 and the isolation film along the thickness direction. That is, the glue layer is located on the side of the flame-retardant member 13 along the thickness direction close to the isolation film. The glue layer not only facilitates the stable adhesion of the flame-retardant member 13, but also plays a role in bonding the positive plate and the negative plate, shaping the interface of the positive plate and / or the negative plate, reducing the risk of wrinkles of the positive plate and the negative plate, and improving the processing consistency.

[0142] In an embodiment, the battery monomer 1 includes a composite coating layer, which is arranged on the surface of at least one of the glue layer and the isolation film along the thickness direction. The composite coating layer can have the functions of liquid absorption and improving the heat shrinkage resistance of the isolation film.

[0143] The composite coating layer can be made of an insulating inorganic material, which can also play a role in protecting micro-short circuits.

[0144] In an embodiment, the material of the composite coating layer includes but is not limited to at least one of ceramic and metal oxide.

[0145] In an embodiment, referring to FIGS. 1, 5 and 6, the battery monomer 1 includes an insulating and heat-insulating member 14 located in the shell 11, and at least one electrode assembly 12 is provided with the insulating and heat-insulating member 14 on at least one side along the thickness direction, and the melting point of the insulating and heat-insulating member 14 is less than the heat shrinkage temperature of the isolation film.

[0146] The electrode assembly 12 is provided with the insulating and heat-insulating member 14 on at least one side along the thickness direction, that is, at least part of the insulating and heat-insulating member 14 overlaps the electrode assembly 12 in the thickness direction. For example, the electrode assembly 12 is provided with the insulating and heat-insulating member 14 on one side along the thickness direction. For another example, the electrode assembly 12 is provided with the insulating and heat-insulating member 14 on both sides along the thickness direction.

[0147] The melting point of the insulating and heat-insulating member 14 refers to the temperature at which the insulating and heat-insulating member 14 changes from a solid state to a liquid state.

[0148] The insulation and thermal insulation member 14 has thermal insulation function and is insulating. The melting point of the insulation and thermal insulation member 14 is lower than the heat shrinkage temperature of the isolation film. When the temperature in the shell 11 reaches the melting point of the insulation and thermal insulation member 14, the insulation and thermal insulation member 14 melts locally, and the liquid-phase insulation and thermal insulation member 14 flows into the electrode assembly 12 to further isolate the positive and negative electrode sheets, thereby reducing the risk of short circuit between the positive and negative electrode sheets to some extent and inhibiting heat spread.

[0149] In this embodiment, on the one hand, the insulation and thermal insulation member 14 can bind the electrode assembly 12, reducing or even eliminating the probability of the electrode assembly 12 shaking in the shell 11. On the other hand, in the case of thermal runaway in the battery monomer 1, the insulation and thermal insulation member 14 melts and flows into the electrode assembly 12, for example, the liquid-phase insulation and thermal insulation member 14 covers the surface of the negative electrode sheet to form an insulating barrier, further isolating the positive and negative electrode sheets to some extent to avoid the risk of short circuit.

[0150] In an embodiment, the material of the insulation and thermal insulation member 14 includes at least one of paraffin, polyethylene, polymethyl acrylate, polyethylene terephthalate, polytetrafluoroethylene, and melamine. For example, when the temperature in the shell 11 rises to the melting point of the above-mentioned materials, the above-mentioned materials melt and penetrate into the electrode assembly 12 to form a non-conductive barrier on the surface of the positive electrode sheet and / or the surface of the negative electrode sheet.

[0151] In an embodiment, the material of the insulation and thermal insulation member 14 includes but is not limited to paraffin. For example, when the temperature in the shell 11 rises to the melting point of the insulation and thermal insulation member 14, the paraffin of the insulation and thermal insulation member 14 melts, and the liquid-phase paraffin penetrates into the electrode assembly 12 to form a non-conductive barrier on the surface of the positive electrode sheet and / or the surface of the negative electrode sheet.

[0152] In an embodiment, the total thickness of the insulation and thermal insulation member 14 is 1 um to 15 um. The total thickness of the insulation and thermal insulation member 14 refers to the sum of the thicknesses of all insulation and thermal insulation members 14 in one battery monomer 1. For example, the total thickness of the insulation and thermal insulation member 14 is 1 um, 2 um, 3 um, 5 um, 8 um, 10 um, 12 um, 14 um, or 15 um, and the like. In this way, the thickness of the battery monomer 1 is not excessively increased to some extent.

[0153] The number of insulation and thermal insulation members 14 can be one or at least two, for example, 2, 3, 4, or 5, and the like.

[0154] In an embodiment, referring to FIG. 5, the battery monomer 1 includes 4 electrode assemblies 12 and 5 insulation and thermal insulation members 14, and one electrode assembly 12 is arranged between two adjacent insulation and thermal insulation members 14. For example, the total thickness of the 5 insulation and thermal insulation members 14 can be 1 um to 15 um.

[0155] In one embodiment, referring to FIG. 6, the cell unit 1 includes 4 electrode assemblies 12 and 5 insulation and thermal insulation pieces 14, the 5 insulation and thermal insulation pieces 14 are stacked along the thickness direction, and the 4 electrode assemblies 12 are distributed on both sides of the 5 insulation and thermal insulation pieces 14 along the thickness direction. For example, the total thickness of the 5 insulation and thermal insulation pieces 14 can be 1 um to 15 um.

[0156] In one embodiment, the insulation and thermal insulation piece 14 can have a flat plate structure. In this way, the flat plate structure of the insulation and thermal insulation piece 14 is easy to form and can better fit the electrode assembly 12.

[0157] In some embodiments, the thickness of each insulation and thermal insulation piece 14 is equal.

[0158] In some embodiments, the thickness of at least two insulation and thermal insulation pieces 14 is not equal. For example, the number of insulation and thermal insulation pieces 14 is three, the thickness of two insulation and thermal insulation pieces 14 is equal, and the thickness of the other insulation and thermal insulation piece 14 is not equal.

[0159] In one embodiment, the amount of oxygen released by the positive electrode sheet is not more than 0.5wt% of the mass of the positive electrode active layer of the positive electrode sheet. For example, the oxygen release amount of the positive electrode sheet can be 0.5wt%, 0.4wt%, or 0wt%, etc. The lower the oxygen release amount of the positive electrode sheet, the less oxygen is released by the positive electrode sheet, so that in the case of thermal runaway of the battery 100, there is not enough oxygen to assist combustion in the shell 11, thereby to some extent avoiding the occurrence of open fire or heat spread in the shell 11, and slowing down the failure as much as possible.

[0160] The oxygen release amount refers to the percentage of the amount of oxygen released by the positive electrode sheet to the mass of the positive electrode active layer of the positive electrode sheet. The determination method of the amount of oxygen released by the positive electrode sheet can be determined by a method known in the art, for example, the determination device can be a thermal analysis and mass spectrometry instrument, the test method can refer to standards JYT014-1996, GB / T 6041-2002, for example, in the temperature range of 45℃ to 600℃, the temperature is raised at 10K / min, in Ar (argon) atmosphere, the mass of oxygen accumulated by the above determination device can be used to obtain the oxygen release amount of the positive electrode sheet.

[0161] In one embodiment, the positive electrode sheet includes a positive electrode active layer, and the material of the positive electrode active layer includes at least one of polyanion type, prussian type, and modified materials of each type. That is, the material of the positive electrode active layer includes at least one of polyanion type, prussian type, modified polyanion type, and modified prussian type. These materials have the characteristics of low oxygen release amount or no oxygen release.

[0162] In an embodiment, the material of the positive active layer includes at least one of NaFePO4, NaMnPO4, NaCoPO4, Na4Fe3(PO4)2O7, Na3V2(PO4)2F3, Na3V2(PO4)3, Prussian blue, Prussian white, and modified versions of each of the above. For example, the material of the positive active layer includes 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 a low oxygen release amount or do not release oxygen, and the oxygen release amount is not greater than 0.5 wt%.

[0163] In some embodiments, the material of the positive active layer can include at least one of NaFePO4, NaMnPO4, NaCoPO4, Na4Fe3(PO4)2O7, Na3V2(PO4)2F3, Na3V2(PO4)3, Prussian blue, Prussian white, and modified versions of each of the above. The modified versions can be doped or coated versions of the above materials. The above materials have stable performance and do not release oxygen or release a small amount of oxygen.

[0164] In an 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 can be 220°C, 230°C, or 250°C, and the like.

[0165] In this embodiment, the thermal runaway temperature of the battery cell 1 is relatively high, the risk of thermal runaway is low, and the safety is high.

[0166] In an embodiment, referring to FIGS. 7-9 and 11, the battery 100 includes a second battery cell 2, the second battery cell 2 and the first battery cell 1 are stacked along a first direction to form a part of the battery cell 10, and the thermal runaway temperature of the second battery cell 2 is not greater than 180°C.

[0167] The second battery cell 2 and the first battery cell 1 are stacked along the first direction, which means that the large face of the second battery cell 2 and the large face of the first battery cell 1 both intersect the first direction, and the large face of the second battery cell 2 and the large face of the first battery cell 1 are substantially parallel. For example, the large face of the first battery cell 1 is perpendicular to the first direction, and the large face of the second battery cell 2 is perpendicular to the first direction. For example, the first direction can be consistent with the thickness direction of the negative current collector 121.

[0168] The thermal runaway temperature refers to a temperature at which the temperature rise rate of the battery cell is not less than 60°C / min.

[0169] The thermal runaway temperature of the second battery cell 2 is not 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, and the like.

[0170] In this embodiment, the monomer unit 10 includes different types of second battery monomer 2 and first battery monomer 1. The second battery monomer 2 can be used to improve the energy density of the battery 100, and the first battery monomer 1 can be used as a safety cell. In the case of thermal runaway of the second battery monomer 2, the first battery monomer 1 can isolate the second battery monomer 2, block the spread of heat, and improve the safety performance of the battery 100. Using the first battery monomer 1 as a heat insulation structure can also reduce the use of the heat insulation structure and improve the utilization rate of the space in the box. The combination of the second battery monomer 2 and the first battery monomer 1 can meet the safety requirements and energy density requirements.

[0171] It can be understood that the second battery monomer 2 and the first battery monomer 1 are both cells.

[0172] The thermal runaway temperature can be tested by a method known in the art. For example, the thermal runaway temperature can be tested by an Accelerating Rate Calorimeter (ARC test). The test conditions are as follows: during the experiment, the prepared sample and container are heated to a pre-set initial temperature under adiabatic conditions, and a certain standby time (usually 5-10 minutes) is allowed to reach thermal equilibrium, and then the self-reaction heat release rate is observed to see if it exceeds the set value (usually set to 0.02℃ / min). If no heat release is detected, the temperature of the sample is increased by one step, usually 5-10℃, and the heat release is checked again after a standby time (usually 5-10 minutes). The same steps are repeated several times, and once the heat release is detected, the experimental system automatically enters strict adiabatic control, and records the time, temperature, heat release rate and pressure data at regular time intervals. The temperature at which the temperature rise rate of the cell is not less than 60℃ / min is the thermal runaway temperature.

[0173] In one embodiment, referring to FIGS. 7-9, the monomer unit 10 includes a heat insulation pad 3 and at least two second battery monomers 2. At least one heat insulation pad 3 is arranged between adjacent two second battery monomers 2.

[0174] For example, in one embodiment, one heat insulation pad 3 is arranged between adjacent two second battery monomers 2. In one embodiment, two or more heat insulation pads 3 are arranged between adjacent two second battery monomers 2.

[0175] In this embodiment, the heat insulation pad 3 can block or delay heat transfer between adjacent two second battery monomers 2, thereby achieving the effect of inhibiting the spread of heat between multiple cells.

[0176] In an embodiment, in the single unit 10, all the second battery cells 2 are arranged in sequence along the first direction as components of the battery pack, and at least one first battery cell 1 is arranged at each end of the battery pack along the first direction. A thermal insulation pad 3 is arranged between any two adjacent second battery cells 2. The first battery cell 1 has higher safety, and the heat transfer between the battery cell and the box can be reduced.

[0177] In an embodiment, referring to FIG. 7, the single unit 10 includes 5 second battery cells 2 and 1 first battery cell 1, the 5 second battery cells 2 are arranged in sequence, and a thermal insulation pad 3 is arranged between any two adjacent second battery cells 2. No thermal insulation pad 3 is arranged between the adjacent second battery cell 2 and the first battery cell 1. In this way, the whole single unit 10 can use four thermal insulation pads 3. In this way, the utilization of the space in the box can be improved, and more battery cells can be placed without increasing the space in the box, thereby improving the energy density.

[0178] In an embodiment, referring to FIG. 8, the single unit 10 includes 3 second battery cells 2 and 2 first battery cells 1, the 3 second battery cells 2 are arranged in sequence, one of the first battery cells 1 is arranged between any two adjacent second battery cells 2, and the other first battery cell 1 is arranged at any end of the single unit 10 along the first direction. A thermal insulation pad 3 is arranged between any two adjacent second battery cells 2. No thermal insulation pad 3 is arranged between the adjacent second battery cell 2 and the first battery cell 1. In this way, the whole single unit 10 can use only one thermal insulation pad 3.

[0179] In an embodiment, in the single unit 10, the first battery cells 1 and the second battery cells 2 are arranged alternately along the first direction. That is, one first battery cell 1 is arranged between any two adjacent second battery cells 2 along the first direction. In this way, the whole single unit 10 can not use the thermal insulation pad 3, and the space in the box can be used to a greater extent, thereby improving the energy density of the battery.

[0180] In an embodiment, referring to FIG. 9, the single unit 10 includes 2 second battery cells 2 and 3 first battery cells 1, the 3 first battery cells 1 are arranged in sequence, and one second battery cell 2 is arranged between any two adjacent first battery cells 1. No thermal insulation pad 3 is arranged between the adjacent second battery cell 2 and the first battery cell 1. In this way, the whole single unit 10 can not use the thermal insulation pad 3.

[0181] In one embodiment, the ratio of the number of the second battery cells 2 to the number of the first battery cells 1 in one monomer unit 10 is 0.5:1 to 5:1. In some embodiments, the ratio of the number of the second battery cells 2 to the number of the first battery cells 1 is 0.5:1 to 4:3. For example, the ratio of the number of the second battery cells 2 to the number of the first battery cells 1 is 0.5:1, 3:1, 4:3, or 5:1, etc.

[0182] In one embodiment, the ratio of the number of the second battery cells 2 to the number of the first battery cells 1 is 1:1, and the second battery cells 2 and the first battery cells 1 are arranged alternately along the first direction. The adjacent second battery cells 2 and the first battery cells 1 can not be provided with the thermal insulation pad 3. In this way, the entire monomer unit 10 can be free of the thermal insulation pad 3, and the structure is more compact, and more second battery cells 2 and the first battery cells 1 can be placed in the box, thereby improving the capacity of the battery 100.

[0183] In this embodiment, the second battery cells 2 can save production costs by using the above-mentioned ratio, the total heat generated by all the second battery cells 2 in the monomer unit 10 can be controlled, the unit heat generated by the monomer unit 10 is relatively small, the number of the first battery cells 1 can improve the reliability of suppressing heat spread, the amount of the thermal insulation structure such as the thermal insulation pad 3 can be reduced, the thermal insulation structure such as the thermal insulation pad 3 can be saved, and the capacity of the battery 100 can be improved.

[0184] In some embodiments, the thermal insulation pad 3 can have a substantially flat plate structure.

[0185] In some embodiments, the thickness of each thermal insulation pad 3 is equal.

[0186] In some embodiments, the thickness of at least two thermal insulation pads 3 is not equal. For example, the number of the thermal insulation pads 3 is three, the thickness of two thermal insulation pads 3 is equal, and the thickness of the other thermal insulation pad 3 is not equal.

[0187] In one embodiment, the second battery cell 2 is a lithium ion battery cell or a lithium metal battery cell.

[0188] In this embodiment, the lithium ion battery cell and the lithium metal battery cell are both battery cells that realize charging and discharging by relying on lithium ions to embed and de-embed between the positive and negative electrodes. The lithium metal battery cell uses lithium metal as the negative active layer, which can be generated after the first charging and discharging. The lithium ion battery and the lithium metal battery have the characteristics of low production cost and relatively large energy density.

[0189] In an embodiment, the second battery cell 2 comprises a positive electrode active material layer, and a material of the positive electrode active material layer comprises at least one of a nickel-cobalt-manganese ternary material, lithium manganate, lithium iron phosphate, and lithium manganese iron phosphate. The above-mentioned materials have relatively low cost and relatively high energy density. The nickel-cobalt-manganese ternary material can be lithium nickel-cobalt-manganese oxide.

[0190] For example, the nickel-cobalt-manganese ternary material can be a high-nickel ternary material or a medium-low-nickel ternary material.

[0191] The high-nickel ternary material can be a material in which a ratio of a content of nickel to a total mass of the positive electrode active material layer is not less than 80%.

[0192] The medium-low-nickel ternary material can be a material in which a ratio of a content of nickel to a total mass of the positive electrode active material layer is less than 80%.

[0193] In an embodiment, the second battery cell 2 comprises a shell, an electrode sheet assembly, and a first electrolyte. The electrode sheet assembly and the first electrolyte are both located in the shell.

[0194] The electrode sheet assembly is an energy storage structure of the second battery cell 2.

[0195] The electrode sheet assembly comprises positive electrode sheets, negative electrode sheets, and separators. At least one separator is arranged between adjacent positive electrode sheets and negative electrode sheets. The separator arranged between the positive electrode sheets and the negative electrode sheets can prevent short circuit.

[0196] The positive electrode sheet comprises a positive electrode current collector and a positive electrode active material layer. The positive electrode active material layer is attached to at least one surface of the positive electrode current collector in a thickness direction.

[0197] For example, the positive electrode current collector has two opposite surfaces in a thickness direction thereof. Either one or both of the two opposite surfaces of the positive electrode current collector in the thickness direction is / are provided with the positive electrode active material layer. In an embodiment, one surface of the positive electrode current collector in the thickness direction is provided with the positive electrode active material layer. In another embodiment, both of the two opposite surfaces of the positive electrode current collector in the thickness direction are provided with the positive electrode active material layer.

[0198] The negative electrode sheet comprises a negative electrode current collector and a negative electrode active material layer. The negative electrode active material layer is attached to at least one surface of the negative electrode current collector in a thickness direction.

[0199] For example, the negative electrode current collector has two opposite surfaces in a thickness direction thereof. Either one or both of the two opposite surfaces of the negative electrode current collector in the thickness direction is / are provided with the negative electrode active material layer. In an embodiment, one surface of the negative electrode current collector in the thickness direction is provided with the negative electrode active material layer. In another embodiment, both of the two opposite surfaces of the negative electrode current collector in the thickness direction are provided with the negative electrode active material layer.

[0200] In this embodiment, the first active ions in the first electrolyte migrate between the positive active material layer and the negative active material layer to realize charging and discharging. The separator can allow the first active ions to pass through.

[0201] In some embodiments, the second battery cell 2 comprises one electrode sheet assembly. In other embodiments, the second battery cell 2 comprises at least two electrode sheet assemblies, which can be stacked along the first direction.

[0202] In one embodiment, the positive electrode sheet is provided with a first positive tab, and the negative electrode sheet is provided with a first negative tab. The first positive tab and the first negative tab can lead the current out of the electrode sheet assembly.

[0203] In some embodiments, the electrode sheet assembly is in a jellyroll structure. For example, the positive electrode sheet, the negative electrode sheet, and the separator are wound into a jellyroll structure.

[0204] In some embodiments, the electrode sheet assembly is in a stack structure.

[0205] For example, the positive electrode sheet, the negative electrode sheet, and the separator are all at least two, the plurality of positive electrode sheets and the plurality of negative electrode sheets are alternately stacked, and one separator is arranged between adjacent positive electrode sheets and negative electrode sheets to form a stack structure.

[0206] For example, the positive electrode sheet can be provided in multiple, and the negative electrode sheet is folded to form a plurality of folded segments arranged in layers, and one positive electrode sheet is clamped between adjacent folded segments to form a stack structure.

[0207] For example, the positive electrode sheet and the negative electrode sheet are both folded to form a plurality of folded segments arranged in layers, and are alternately nested with each other to form a stack structure.

[0208] In one embodiment, the battery cell 1 comprises a second electrolyte, and the second electrolyte is located in the housing 11. The positive electrode sheet comprises a positive current collector, and a positive active layer is attached to at least one surface of the positive current collector. The second active ions in the second electrolyte migrate between the positive active layer and the negative active layer to realize charging and discharging. The separator can allow the second active ions to pass through.

[0209] In one embodiment, the positive electrode sheet is provided with a second positive tab, and the negative electrode sheet is provided with a second negative tab. The second positive tab and the second negative tab can lead the current out of the electrode assembly 12.

[0210] In some embodiments, the electrode assembly 12 is in a jellyroll structure. For example, the positive electrode sheet, the negative electrode sheet, and the separator are wound into a jellyroll structure.

[0211] In some embodiments, the electrode assembly 12 is in a stack structure.

[0212] Exemplarily, the positive electrode sheet, the negative electrode sheet and the separator are all at least two, the plurality of positive electrode sheets and the plurality of negative electrode sheets are alternately stacked, and one separator is arranged between adjacent positive electrode sheets and negative electrode sheets to form a laminated structure.

[0213] Exemplarily, the positive electrode sheet can be provided in plurality, the negative electrode sheet is folded to form a plurality of folded segments arranged in layers, and one positive electrode sheet is clamped between adjacent folded segments to form a laminated structure.

[0214] Exemplarily, the positive electrode sheet and the negative electrode sheet are both folded to form a plurality of folded segments arranged in layers, and are alternately nested with each other to form a laminated structure.

[0215] The shell is a hollow structure, and an accommodation cavity for accommodating the electrode sheet assembly and the first electrolyte is formed in the shell. The shell can be in various shapes, such as a cuboid and the like.

[0216] The shell 11 is a hollow structure, and an accommodation space for accommodating the electrode assembly 12 and the second electrolyte is formed in the shell 11. The shell 11 can be in various shapes, such as a cuboid and the like.

[0217] In some embodiments, the shell can be a hard structure, and exemplarily, the shell can be made of hard materials such as aluminum and / or steel.

[0218] In some embodiments, the shell includes a shell body and a cover, the shell body can be a hollow structure with one end open, and the cover closes the one end opening of the shell body. In this way, the cover and the shell body jointly define the accommodation cavity.

[0219] In some embodiments, the cover can be configured with a balance valve. The balance valve can pre-discharge part of the gas in the accommodation cavity, which is helpful for heat dissipation and avoiding accumulation of flammable gas at high temperature, and can improve the heat resistance temperature range.

[0220] In some embodiments, the shell 11 can be a hard structure, and exemplarily, the shell 11 can be made of hard materials such as aluminum and / or steel.

[0221] In some embodiments, the shell 11 includes a bottom shell and a top cover, the bottom shell can be a hollow structure with one end open, and the top cover closes the one end opening of the bottom shell. In this way, the top cover and the bottom shell jointly define the accommodation space.

[0222] In some embodiments, the top cover can be configured with a balance valve. The balance valve can pre-discharge part of the gas in the accommodation space, which is helpful for heat dissipation and avoiding accumulation of flammable gas at high temperature, and can improve the heat resistance temperature range.

[0223] The balance valve includes but is not limited to a breather valve or an explosion-proof valve, etc. The balance valve can be a one-way valve. The one-way valve of the cover can limit the gas flow in the accommodation cavity to flow outwards in one direction. The one-way valve of the top cover can also limit the gas flow in the accommodation space to flow outwards in one direction.

[0224] In some embodiments, the positive current collecting substrate and the positive current collector can both be metal foils or composite current collectors. The metal foils can be made of aluminum, silver surface treated aluminum, stainless steel, or the like. The composite current collectors can include a polymer material base layer and a metal layer. The metal layer can be made of aluminum, aluminum alloy, nickel, or the like. The polymer material base layer can be made of polypropylene, polyethylene terephthalate, or polyethylene, or the like.

[0225] It should be noted that the positive current collecting substrate and the positive current collector can be made of the same material or different materials.

[0226] In some embodiments, the negative current collecting substrate and the negative current collector 121 can both be metal foils or composite current collectors. The metal foils can be made of copper or nickel, or the like. The composite current collectors can include a polymer material base layer and a metal layer. The metal layer can be made of copper or nickel, or the like. The polymer material base layer can be made of polypropylene, polyethylene terephthalate, or polyethylene, or the like.

[0227] It should be noted that the negative current collecting substrate and the negative current collector 121 can be made of the same material or different materials.

[0228] The second battery cell 2 and the battery cell 1 can both be secondary batteries 100, which refers to an electric cell that can be activated by charging after discharging to continue to be used.

[0229] For example, the battery cell 1 and the second battery cell 2 in the battery 100 can be connected in series, in parallel, or in a mixed connection, which means that the battery cell 1 and the second battery cell 2 are connected in series and in parallel. The battery cell 1 and the second battery cell 2 can be directly connected in series, in parallel, or in a mixed connection; of course, the battery cell 1 and the second battery cell 2 can first be connected in series, in parallel, or in a mixed connection to form a battery 100 group, and then the battery 100 group is connected in series, in parallel, or in a mixed connection to form a whole.

[0230] The battery 100 can also include other structures, for example, the battery 100 can also include a current collecting component for realizing the electrical connection between the battery cell 1 and the second battery cell 2.

[0231] In some embodiments, the battery 100 includes one single cell 10.

[0232] In some embodiments, the battery 100 includes at least two single cells 10; the at least two single cells 10 can be stacked along a third direction. Alternatively, the at least two single cells 10 can be laid flat along a second direction. Alternatively, a plurality of single cells 10 can be laid flat along a second direction to form a layer, and a plurality of layers of single cells 10 can be stacked along a third direction.

[0233] In an example embodiment, the material of the negative active layer of the first battery cell 1 is sodium metal, and the separator is PP or PE. The thermal runaway temperature of the second battery cell 2 is not greater than 180°C, and the second battery cell 2 is a lithium ion battery 100, that is, the first active ion of the second battery cell 2 is lithium ion. The second battery cell 2 and the first battery cell 1 are stacked in the first direction to form the cell unit 10.

[0234] In this embodiment, on the one hand, the melting point of the negative active layer is lower than the thermal shrinkage temperature of the separator. In the case of temperature rise in the shell 11, due to the relatively low melting point of the negative active layer, the temperature in the shell 11 will first reach the melting point of the negative active layer, causing the local melting of the negative active layer. The local melting of the negative active layer breaks the negative plate and forms a separator, the separator separates from the negative plate, and the separator cannot spread to the remaining negative active layer of the negative plate in a solid contact manner. That is, the local melting of the negative plate inhibits the continuous thermal spread on the negative plate. The negative active layer absorbs heat during melting, which can delay or inhibit the continuous rise of the temperature in the shell 11, thereby breaking the continuous thermal spread inside. The phase change of the local negative active layer can inhibit the temperature rise in the shell 11. In this way, the temperature in the shell 11 is lower than the thermal shrinkage temperature of the separator, that is, the separator does not shrink, reducing the risk of short circuit between the positive plate and the negative plate, and playing a self-protection barrier role, inhibiting thermal spread, and improving the safety performance of the battery cell 1. On the other hand, the battery cell 1 has lower heat generation per unit mass and higher capacity per unit mass. The battery cell 1 with the same capacity has lower heat generation capacity. The combination of the second battery cell 2 and the first battery cell 1 has a wider mass energy density range and safety performance.

[0235] In some embodiments, the DSC heat generation of the negative plate 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 plate of the second battery cell 2 can be 1500 J / g to 3000 J / g. In this way, the DSC heat generation of the negative plate of the first battery cell 1 is relatively low, the heat release energy is small, and the safety performance is good. The second battery cell 2 can be used to meet the high energy density and low cost requirements of the battery.

[0236] It should be noted that the unit J / g refers to joules per gram. DSC refers to differential scanning calorimetry (DSC). The DSC heat generation refers to the DSC heat release of the unit mass of the negative active layer under nitrogen atmosphere at 50°C to 500°C.

[0237] It can be understood that the DSC heat generation of the negative tab of the first battery cell 1 and the DSC heat generation of the negative tab of the second battery cell 2 are defined in the same way and can be measured in the same way. The DSC heat generation of the negative tab of the first battery cell 1 is taken as an example for illustration. By disassembling the negative tab of the battery cell in the fully charged state, the DSC heat generation at the tab level is tested, and the heat release is compared, which serves as evidence of the safety capability of the battery cell. The determination can be made by a method known in the art. The DSC heat generation can be measured according to the national standard document GB / T 13464-2008. As an example, the DSC heat generation can be tested by the following method:

[0238] Test conditions: test equipment model: NETZSCH STA 449F3; sample: negative tab is punched into a small disc with a diameter of 5mm (the negative tab includes a negative active layer and a current collector, and the mass of the current collector needs to be deducted when calculating the heat release per unit mass); 2uL (microliters) of electrolyte is added on the negative tab; the test starting temperature is room temperature, for example, 25°C; the temperature rising rate is 10K / min (kelvin per minute); the test atmosphere is nitrogen; the sample preparation environment is a glove box.

[0239] Post-test data standard processing: the ordinate of the DSC test result is the heat flow, with the unit of mW / mg (milliwatt per milligram), and the abscissa is the temperature, with the unit of °C. The test data needs to deduct the baseline of the empty crucible test result; the horizontal adjustment is made from 50°C to the end temperature, and the DSC heat release of the test sample in the range of 50°C-500°C under nitrogen atmosphere is obtained by fitting calculation. In the present disclosure, the heat spread test can be performed in a manner known in the art, for example, the heat spread test of the battery 100 can refer to the heat diffusion test in Appendix C of GB 38031-2020. As an example, the following test steps can be used:

[0240] S1: all test battery cells are fully charged (full charging refers to charging at 0.33C rate current to the nominal voltage by constant current and constant voltage charging), the battery cells are arranged and electrically connected into a module, the module is fixed by end plates and side plates together or by steel belts; select appropriate steel needle 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 capacity of the battery cell and the size of the shell);

[0241] S2: place the module in a simulated sealed box (the sealed box has an explosion-proof function), and monitor the voltage and temperature of each battery cell;

[0242] S3: heating plate verification of heat spread: select a first battery cell 1 adjacent to the second battery cell 2 in the module as a target battery cell, and place it close to the heating plate. The heating plate is plugged in for heating until the target battery cell fails (active failure), the needle piercing is stopped, and the heat spread is observed;

[0243] S4: after the target battery cell fails, stop heating or needling (one of the two verification measures), continue to observe the module for two hours, and confirm whether the other second battery cell 2 and the other first battery cell 1 on the non-trigger side in the module have thermal spread (i.e., determine whether the battery cell fails); after cooling for 24 hours, perform appearance confirmation, capacity test on the second battery cell 2 and the battery cell 1.

[0244] The thermal spread determination standard is to confirm whether other battery cells have open flames; if there are no open flames, thermal spread does not occur, and if there are open flames, thermal spread occurs.

[0245] The battery cell failure standard is that if any two of the following four conditions are met, the battery cell is considered to have failed: ① temperature ≥ 280℃; ② battery cell temperature rise rate reaches: dT / dt ≥ 1℃ / s, and lasts for more than 3s; ③ battery cell voltage drop exceeds 25% of the initial voltage; ④ battery cell produces open flames.

[0246] The above method can be used to determine whether the battery has thermal spread and whether the battery cell has failed.

[0247] The following is a comparative example and four test examples of the present disclosure for thermal spread test experiments:

[0248] Table 1

[0249] It should be noted that the ternary lithium battery cell of the comparative example is a self-made battery cell, the positive active material uses lithium nickel manganese cobalt oxide, the negative active material uses graphite, the output voltage is 3.7V, and the capacity is 177Ah.

[0250] In the first test example to the fourth test example of the present disclosure:

[0251] The first battery cell is a self-made battery cell, the positive active layer uses Na4Fe3(PO4)2O7; the material of the negative active layer is shown in Table 1; the output voltage is 3.0V, and the capacity is 130Ah.

[0252] The second battery cell is a self-made battery cell, the positive active material layer uses lithium nickel manganese cobalt oxide, and the material of the negative active material layer uses graphite, the output voltage is 3.7V, and the capacity is 177Ah.

[0253] According to Table 1, the battery of the comparative example includes a module composed of five ternary lithium battery cells stacked in the first direction, the melting point of the negative active material layer of the ternary lithium battery cell is higher than the thermal shrinkage temperature of the isolation film, and any one of the ternary lithium battery cells between the two ends can be selected as the target battery cell. The comparative example is subjected to thermal spread test, that is, thermal diffusion test according to GB 38031-2020 Appendix C, the comparative example has thermal spread, and the battery cell fails.

[0254] According to Table 1, in the first test example, the second battery monomer in the second test example, the third test example and the fourth test example of the present disclosure, the second battery monomer is a ternary lithium battery monomer, the melting point of the negative active layer of the first battery monomer is lower than the heat shrinkage temperature of the isolation film; for the first test and the second test example of the present disclosure: select any one of the five first battery monomers 1 as the target battery cell; for the third test and the fourth test example of the present disclosure: select one of the first battery monomers 1 adjacent to the second battery monomer 2 in the module as the target battery cell, and perform heat spread test on the first test example, the second test example, the third test example and the fourth test example of the present disclosure, that is, perform heat diffusion test according to GB 38031-2020 Appendix C, the first test example, the second test example, the third test example and the fourth test example of the present disclosure do not occur heat spread, and the battery cell is effective. Therefore, the first battery monomer can play a self-protection barrier role, and the first battery monomer can be used as a safety battery cell to isolate the second battery monomer and inhibit heat spread.

[0255] The above embodiments are only used to illustrate the technical solutions of the present disclosure, but not to limit them; although the present disclosure has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or make equivalent replacement for part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present disclosure, especially, as long as there is no structural conflict, each technical feature mentioned in each embodiment can be combined in any way.

Claims

1. A battery cell, comprising: a housing; an electrode assembly located in the housing, the electrode assembly comprising a negative electrode sheet, a positive electrode sheet, and a separator, at least one of the separator being disposed between adjacent ones of the positive electrode sheet and the negative electrode sheet, the negative electrode sheet comprising a negative electrode current collector and a negative electrode active layer, the negative electrode active layer being disposed on at least one surface of the negative electrode current collector in a thickness direction, the negative electrode active layer having a melting point lower than a heat shrinkage temperature of the separator. the negative electrode active layer being deposited on at least one surface of the negative electrode current collector in a thickness direction after the battery cell is charged. the negative electrode active layer comprising at least one of sodium metal and potassium metal.

2. The battery cell of claim 1, wherein, the negative electrode current collector having at least two partitioned regions separated by a surface of the negative electrode current collector, the negative electrode active layer being present in the partitioned regions.

3. The battery cell of claim 1 or 2, wherein, the negative electrode sheet comprising a support structure, the support structure being disposed on at least one surface of the negative electrode current collector in a thickness direction, the support structure separating the surface of the negative electrode current collector into at least two of the partitioned regions.

4. The battery cell according to any one of claims 1 to 3, wherein, the support structure being printed or etched on the negative electrode current collector.

5. The battery cell of claim 4, wherein, the support structure comprising at least two support bars, at least some of the support bars forming a closed region.

6. The battery cell of claim 5, wherein, the support structure comprising first support bars and second support bars, the first support bars and the second support bars intersecting.

7. The battery cell of claim 5 or 6, wherein, at least two of the first support bars and at least two of the second support bars interleaving to form a grid-like region.

8. The battery cell of any one of claims 5 to 7, wherein, the negative electrode sheet comprising a conductive layer, the conductive layer being located between the negative electrode current collector and the support structure in a thickness direction of the negative electrode current collector.

9. The battery cell of claim 8, wherein, the battery cell comprising a flame retardant located in the housing, the separator having at least one surface in a thickness direction of the separator on which the flame retardant is disposed, the flame retardant comprising a wrapping shell and a flame retardant agent, the flame retardant agent being contained in the wrapping shell, the wrapping shell having a melting point lower than a heat shrinkage temperature of the separator.

10. The battery cell of any one of claims 5 to 9, wherein, the flame retardant covering both surfaces of the separator in a thickness direction.

11. The battery cell of any one of claims 1 to 10, wherein, the battery cell comprising an insulating and heat insulating member located in the housing, at least one of the electrode assemblies having at least one side in a thickness direction of the electrode assembly on which the insulating and heat insulating member is disposed, the insulating and heat insulating member having a melting point lower than a heat shrinkage temperature of the separator.

12. The battery cell of claim 11, wherein, the insulating and heat insulating member comprising at least one of paraffin, polyethylene, polymethyl acrylate, polyethylene terephthalate, polytetrafluoroethylene, and melamine.

13. The battery cell of any one of claims 1 to 12, wherein, an amount of oxygen released by the positive electrode sheet being not more than 0.5 wt% relative to a mass of a positive electrode active layer of the positive electrode sheet.

14. The battery cell of claim 13, wherein, the positive electrode active layer comprising at least one of polyanion-based, prussian-based, and modified versions of each of the foregoing.

15. The battery cell of any one of claims 1 to 14, wherein, the positive electrode active layer comprising at least one of NaFePO 4, NaMnPO 4, NaCoPO 4, Na 4 Fe 3 (PO 4) 2 O 7, Na 3 V 2 (PO 4) 2 F 3, Na 3 V 2 (PO 4) 3, Prussian blue, Prussian white, and modified versions of each of the foregoing.

16. The battery cell of claim 15, wherein, the battery cell having a thermal runaway temperature not less than 220℃.

17. The battery cell of claim 16, wherein, ​ 18. The battery cell of any one of claims 1 to 17, wherein, ​ 19. A battery comprising the battery cell of any one of claims 1 to 18 as a first battery cell.

20. The battery of claim 19, wherein, The battery comprises a second battery cell, the second battery cell and the first battery cell are stacked along a first direction to be a component of a cell unit, the thermal runaway temperature of the second battery cell is not greater than 180℃.

21. The battery of claim 20, wherein, In any one of the 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.

22. The battery of claim 20 or 21, wherein, The cell unit comprises a thermal insulation pad and at least two of the second battery cells, at least one of the thermal insulation pads is arranged between two adjacent second battery cells.

23. The battery of any one of claims 20-22, wherein, The second battery cell comprises a positive electrode active material layer, the material of the positive electrode active material layer comprises at least one of a nickel-cobalt-manganese ternary material, lithium manganate, lithium iron phosphate and manganese iron phosphate.

24. An electric device comprising the battery of any one of claims 19 to 23 for providing electric energy.

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