Secondary battery, energy storage device, and method for manufacturing secondary battery

Abstract

The application discloses a secondary battery, an energy storage device and a secondary battery manufacturing method. The secondary battery comprises a shell and at least one electrode assembly. The electrode assembly comprises a positive electrode sheet, a negative electrode sheet and a separator. The material of the positive electrode active material layer of the positive electrode sheet comprises lithium-containing phosphate. The material of the negative electrode active material layer of the negative electrode sheet comprises graphite. The separator comprises a substrate layer and a reinforcing layer attached to at least one surface of the substrate layer. The total thickness of the reinforcing layer attached to the substrate layer is not less than 1 micrometer. The length of the large surface of the shell is in the range of 260 mm to 475 mm, the width of the large surface is in the range of 160 mm to 300 mm, and the electric capacity of the secondary battery is not less than 300 Ah. The application has large capacity and low self-discharge rate.

Description

Technical Field

[0001] This application relates to the field of battery technology, and in particular to secondary batteries, energy storage devices, and methods for manufacturing secondary batteries. Background Technology

[0002] The application of new energy batteries in daily life and industry is becoming increasingly widespread. For example, new energy vehicles equipped with batteries are already widely used, and batteries are also increasingly being applied in energy storage. In new energy vehicles equipped with batteries, the batteries can provide all or part of the power. In the field of energy storage, batteries can be installed in energy storage boxes or directly on the user side.

[0003] How to increase battery capacity while suppressing self-discharge rate is one of the topics that the industry needs to study. Summary of the Invention

[0004] To address the aforementioned technical problems, this application provides a secondary battery with low self-discharge rate and large capacity, an energy storage device, and a method for manufacturing the secondary battery.

[0005] This application is achieved through the following technical solution.

[0006] The first aspect of this application provides a secondary battery, comprising: a casing having a receiving cavity; at least one electrode assembly disposed within the receiving cavity, the electrode assembly comprising stacked positive electrode sheets, a separator, and a negative electrode sheet, the positive electrode sheet comprising a positive current collector and a positive active material layer attached to at least one surface of the positive current collector, the positive active material layer being made of lithium phosphate; the negative electrode sheet comprising a negative current collector and a negative active material layer attached to at least one surface of the negative current collector, the negative active material layer being made of graphite; the separator comprising a substrate layer and a reinforcing layer attached to at least one surface of the substrate layer, the total thickness of the reinforcing layers attached to the same substrate layer being not less than 1 μm; the length and width of the large surface of the casing being in the range of 260 mm to 475 mm and 160 mm to 300 mm, respectively, and the capacity of the secondary battery being not less than 300 Ah.

[0007] In the technical solution of this application embodiment, the positive electrode active material layer of the positive electrode sheet includes lithium phosphate, and the negative electrode active material layer of the negative electrode sheet includes graphite, thus the secondary battery is suitable for energy storage devices. This application embodiment limits the length and width of the large surface of the casing to the ranges of 260mm to 475mm and 160mm to 300mm, respectively, resulting in a larger secondary battery size and a capacity of not less than 300Ah, thus giving the secondary battery a large capacity. Furthermore, the positive and negative electrode sheets of the electrode assembly are stacked, making the electrode assembly a stacked structure, eliminating the space enclosed by the bends and corners of the casing in a wound structure, thereby increasing the volumetric energy density of the secondary battery and further increasing its capacity. Furthermore, this application addresses the problem of increased burrs caused by the stacked structure, leading to a higher probability of puncturing the separator. It limits the total thickness of the reinforcing layer attached to the same substrate layer of the electrode assembly separator to a relatively large range, reducing the probability of the separator being punctured by burrs and thus lowering the self-discharge rate of the high-capacity secondary battery. Therefore, this application's embodiments increase the capacity of the secondary battery while also reducing its self-discharge rate. Additionally, due to profitability considerations, power batteries have a stronger requirement for small footprint than energy storage devices. Therefore, suppressing self-discharge rate by thickening the separator is more suitable for secondary batteries in energy storage devices.

[0008] In some embodiments, the length of the large surface is in the range of 310mm to 370mm, and / or the width of the large surface is in the range of 190mm to 230mm.

[0009] Thus, by limiting the length of the large surface to the range of 310mm to 370mm and the width of the large surface to the range of 190mm to 230mm, the size of the secondary battery is made larger, which increases the capacity of the secondary battery. Moreover, the number of secondary batteries that can be accommodated in a certain volume of space is relatively small, which can reduce the space occupied by the secondary battery casing. This allows the space occupied by the electrode assembly of the secondary battery to be relatively increased, that is, the volumetric energy density within a certain volume of space is increased.

[0010] In some embodiments, the total thickness of the reinforcing layers attached to the same substrate layer is in the range of 2 μm to 4 μm.

[0011] By limiting the total thickness of the reinforcing layer attached to the same substrate layer of the separator to the range of 2μm to 4μm, the thickness of the separator is kept within a suitable range. This reduces the chance of the separator being punctured by burrs and prevents the separator from being too thick, which would excessively affect the internal resistance and capacity of the secondary battery.

[0012] In some embodiments, the reinforcing layer is attached to both surfaces of the substrate layer, and the two reinforcing layers have the same thickness.

[0013] This ensures uniform strength on both sides of the substrate layer, further reducing the risk of the separator being punctured.

[0014] In some embodiments, the thickness of the insulating element is in the range of 7 μm to 20 μm.

[0015] In this way, by limiting the thickness of the separator to the range of 7μm to 20μm, the probability of the separator being punctured by burrs can be reduced, and the internal resistance and capacity of the secondary battery will not be affected too much by the separator being too thick.

[0016] In some embodiments, the thickness of the insulating element is in the range of 9 μm to 14 μm.

[0017] In this way, by limiting the thickness of the separator to the range of 9μm to 14μm, the probability of the separator being punctured by burrs can be reduced, and the internal resistance and capacity of the secondary battery will not be affected too much by the separator being too thick.

[0018] In some embodiments, the positive current collector forms a positive electrode tab at at least one end along the width direction of the large surface, and the negative current collector forms a negative electrode tab at at least one end along the width direction of the large surface, wherein the ratio of the length to the width of the large surface is in the range of 1 to 3.

[0019] By limiting the ratio of the length to the width of the large surface to the range of 1 to 3, not only can the electron transport path be shortened, but the uniformity of the current density can also be improved, thereby increasing the energy conversion efficiency.

[0020] In some embodiments, the positive current collector forms a positive electrode tab at at least one end along the width direction of the large surface, and the negative current collector forms a negative electrode tab at at least one end along the width direction of the large surface, wherein the ratio of the length to the width of the large surface is in the range of 1.1 to 2.

[0021] By limiting the ratio of the length to the width of the large surface to the range of 1.1 to 2, not only can the electron transport path be shortened, but the uniformity of the current density can also be improved, thereby increasing the energy conversion efficiency.

[0022] In some embodiments, the dimensions of the housing in the direction perpendicular to the large surface are in the range of 50 mm to 100 mm.

[0023] Thus, by limiting the size of the outer casing in the direction perpendicular to the large surface to within the range of 50mm to 100mm, the size of the secondary battery is made larger, thereby increasing the volumetric energy density within a certain volume of storage space.

[0024] In some embodiments, the dimensions of the housing in the direction perpendicular to the large surface are in the range of 60 mm to 80 mm.

[0025] Thus, by limiting the size of the outer casing in the direction perpendicular to the large surface to 60mm to 80mm, the size of the secondary battery is made larger, thereby increasing the volumetric energy density within a certain volume of storage space.

[0026] In some embodiments, the capacity of the secondary battery is not less than 500Ah.

[0027] In this way, by limiting the capacity of the secondary battery to no less than 500Ah, the secondary battery can have a large capacity, thereby increasing the energy density and achieving the goal of cost reduction.

[0028] In some embodiments, the reinforcing layer comprises inorganic particles and organic particles.

[0029] The reinforcing layer includes inorganic and organic particles. On the one hand, it can improve the strength of the separator and reduce the risk of separator puncture. On the other hand, it can improve the interface between the positive and negative electrode plates and the separator in the electrode assembly, reduce the risk of wrinkling, and improve the performance of the secondary battery. In addition, the organic particles can leave gaps between the positive and negative electrode plates and the separator, thereby mitigating the degree of expansion during the charging and discharging process of the secondary battery.

[0030] In some embodiments, the reinforcing layer includes a first reinforcing layer attached to the surface of the substrate layer and a second reinforcing layer attached to the surface of the first reinforcing layer facing away from the substrate layer, wherein the material of the first reinforcing layer includes the inorganic particles and the material of the second reinforcing layer includes the organic particles.

[0031] Thus, the layering of inorganic and organic particles can improve the strength of the separator and reduce the risk of puncture. On the other hand, it can improve the interface between the positive and negative electrode plates and the separator in the electrode assembly, reduce the risk of wrinkling, and improve the performance of the secondary battery. In addition, the organic particles can leave gaps between the positive and negative electrode plates and the separator, thereby mitigating the expansion of the secondary battery during charging and discharging.

[0032] In some embodiments, the reinforcing layer includes an inorganic particle layer attached to the surface of the substrate layer and organic particles embedded in the inorganic particle layer, wherein the organic particles form protrusions on the surface of the inorganic particle layer.

[0033] Thus, embedding organic particles into inorganic particles can improve the strength of the separator and reduce the risk of separator puncture. On the other hand, it can improve the interface between the positive and negative electrode plates and the separator in the electrode assembly, reduce the risk of wrinkling, and improve the performance of the secondary battery. In addition, organic particles can leave gaps between the positive and negative electrode plates and the separator, thereby mitigating the degree of expansion during the charging and discharging process of the secondary battery.

[0034] In some embodiments, the average particle size of the organic particles is in the range of 2 μm to 25 μm.

[0035] If the particle size of the organic particles is too large, they tend to form large sheets of adhesive film, thus affecting ion conduction. If the particle size is too small, it will affect the dispersion of the organic particles on the substrate layer and will hardly serve its purpose of leaving gaps between the positive and negative electrode plates and the separator, thus affecting the performance of the secondary battery. Therefore, the embodiments of this application limit the average particle size of the organic particles to the range of 2μm to 25μm, which not only improves ion conduction but also leaves gaps, thereby improving the performance of the secondary battery.

[0036] In some embodiments, the average particle size of the organic particles is in the range of 4 μm to 20 μm.

[0037] Therefore, by limiting the average particle size of the organic particles to the range of 4μm to 20μm, the embodiments of this application can not only improve the conductivity of ions, but also leave gaps to improve the performance of the secondary battery.

[0038] In some embodiments, the average particle size of the inorganic particles is not greater than 2.5 μm.

[0039] Thus, by limiting the average particle size of inorganic particles to no more than 2.5 μm, the use of small-sized inorganic particles is beneficial for the inorganic particles to be coated more evenly and densely on the substrate layer, reducing the risk of the separator being punctured.

[0040] In some embodiments, the average particle size of the inorganic particles is in the range of 0.5 μm to 2.5 μm.

[0041] In this way, the average particle size of inorganic particles is limited to the range of 0.5μm to 2.5μm, which allows the inorganic particles to be used with a small particle size. This is beneficial for the inorganic particles to be coated more evenly and densely on the substrate layer, reducing the risk of the separator being punctured.

[0042] In some embodiments, the organic particles comprise at least one of the following: homopolymers or copolymers of fluoroolefin monomer units, homopolymers or copolymers of olefin monomer units, homopolymers or copolymers of unsaturated nitrile monomer units, homopolymers or copolymers of epoxy alkane monomer units, homopolymers or copolymers of acrylic monomer units, homopolymers or copolymers of acrylate monomer units, homopolymers or copolymers of styrene monomer units, polyurethane compounds, rubber compounds, and modified compounds of the above homopolymers or copolymers.

[0043] Thus, applying the aforementioned organic particles to the separator can improve the adhesion between the separator and the electrode, and reduce the degree of expansion during the charging and discharging process of the secondary battery.

[0044] In some embodiments, the infinite particles include at least one of boehmite, alumina, silicon dioxide, magnesium oxide, magnesium hydroxide, titanium dioxide, tin dioxide, barium sulfate, calcium oxide, zinc oxide, zirconium oxide, yttrium oxide, cerium oxide, magnesium fluoride, and barium titanate.

[0045] Thus, applying the aforementioned inorganic particles to the separator can enhance its mechanical strength, reduce the likelihood of it being punctured by burrs, and extend the lifespan of the secondary battery.

[0046] In some embodiments, the material of the positive electrode active material layer includes lithium iron phosphate, and the material of the negative electrode active material layer includes artificial graphite.

[0047] In some embodiments, the housing is made of aluminum and / or steel.

[0048] The outer casing is made of aluminum and / or steel, making it a rigid casing, and the secondary battery is also a rigid-cased secondary battery. This gives the casing a certain degree of hardness and strength, making it less prone to deformation under pressure and impact, thus enabling the secondary battery to have higher structural strength and improved safety performance.

[0049] A second aspect of this application provides an energy storage device comprising a plurality of secondary batteries provided in the first aspect, the secondary batteries being used to store or provide electrical energy.

[0050] Since the energy storage device includes a secondary battery provided by the first aspect and the secondary battery has a large capacity and a low self-discharge rate, the energy storage device has a large capacity and a low self-discharge rate.

[0051] A third aspect of this application provides a method for manufacturing a secondary battery, comprising:

[0052] Provide a substrate layer;

[0053] A reinforcing layer is attached to at least one surface of the substrate layer to form a spacer;

[0054] Provides positive current collector;

[0055] A positive electrode active material layer is attached to at least one surface of the positive electrode current collector to form a positive electrode sheet;

[0056] Provide negative electrode current collector;

[0057] A negative electrode active material layer is attached to at least one surface of the negative electrode current collector to form a negative electrode sheet;

[0058] The positive electrode, the separator, and the negative electrode are stacked sequentially along a first direction to form an electrode assembly;

[0059] Provide a casing;

[0060] At least one of the electrode components is installed inside the housing to form a secondary battery;

[0061] The positive electrode active material layer is made of lithium phosphate, the negative electrode active material layer is made of graphite, and the total thickness of the reinforcing layer attached to the substrate layer is not less than 1 μm; the length and width of the outer shell are in the range of 260 mm to 475 mm and 160 mm to 300 mm, respectively, and the capacity of the secondary battery is not less than 300 Ah.

[0062] The secondary battery manufactured in this application embodiment is suitable for energy storage devices because the positive electrode active material layer of the positive electrode sheet includes lithium phosphate and the negative electrode active material layer of the negative electrode sheet includes graphite. This application embodiment limits the length and width of the large surface of the casing to the ranges of 260mm to 475mm and 160mm to 300mm, respectively, resulting in a larger secondary battery size and a capacity of not less than 300Ah, thus achieving a large capacity. Furthermore, the positive and negative electrode sheets of the electrode assembly are stacked, resulting in a stacked structure that eliminates the space enclosed by the bends and corners of the casing in a wound structure, thereby increasing the volumetric energy density of the secondary battery and further increasing its capacity. Furthermore, this application addresses the problem of increased burrs caused by the stacked structure, leading to a higher probability of puncturing the separator. It limits the total thickness of the reinforcing layer attached to the same substrate layer of the electrode assembly separator to a relatively large range, reducing the probability of the separator being punctured by burrs and thus lowering the self-discharge rate of the high-capacity secondary battery. Therefore, this application's embodiments increase the capacity of the secondary battery while also reducing its self-discharge rate. Additionally, due to profitability considerations, power batteries have a stronger requirement for small footprint than energy storage devices. Therefore, suppressing self-discharge rate by thickening the separator is more suitable for secondary batteries in energy storage devices.

[0063] The beneficial effects of the embodiments disclosed herein include: through this application, a secondary battery with low self-discharge rate and large capacity, an energy storage device, and a method for manufacturing a secondary battery can be provided. Attached Figure Description

[0064] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiments below. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of this application. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0065] Figure 1 This is a three-dimensional structural schematic diagram of an energy storage device according to one or more embodiments;

[0066] Figure 2 This is an exploded perspective view of a battery pack according to one or more embodiments;

[0067] Figure 3 A cross-sectional view of a battery cell according to one or more embodiments;

[0068] Figure 4 A cross-sectional view of a spacer according to one or more embodiments. Figure 1 ;

[0069] Figure 5 A cross-sectional view of a spacer according to one or more embodiments. Figure 2 ;

[0070] Figure 6 A three-dimensional structural schematic diagram of a battery cell according to one or more embodiments;

[0071] Figure 7 An exploded perspective view of a battery cell according to one or more embodiments;

[0072] Figure 8 A cross-sectional view of a spacer according to one or more embodiments. Figure 3 .

[0073] Explanation of reference numerals in the attached figures

[0074] 1000 Energy storage device; 100 Battery pack; 200 Energy storage enclosure; 210 Communication interface; 220 Power transmission interface; 10 Battery box; 101 Box cover; 102 Box body; 20 Battery cell; 1 Outer shell; 11 End cap; 12 Housing; 121 Large surface; 13 Pressure relief mechanism; 14 Electrode terminal; 15 Adapter piece; 2 Electrode assembly; 21 Positive electrode sheet; 211 Positive electrode tab; 22 Separator; 221 Substrate layer; 222 Reinforcing layer; 2221 First reinforcing layer; 2222 Second reinforcing layer; 23 Negative electrode sheet; 231 Negative electrode tab. Detailed Implementation

[0075] The embodiments of the technical solution of this application will now be described in detail with reference to the accompanying drawings. These embodiments are only used to more clearly illustrate the technical solution of this application and are therefore merely examples, and should not be used to limit the scope of protection of this application.

[0076] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit this application; the terms “comprising” and “having”, and any variations thereof, in the specification and the foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0077] In the description of the embodiments of this application, technical terms such as "first," "second," and "third" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0078] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0079] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects are in an "or" relationship.

[0080] In the description of the embodiments of this application, the technical terms "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "circumferential", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the embodiments of this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed, operated or used in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of this application.

[0081] In the description of the embodiments of this application, unless otherwise expressly specified and limited, technical terms such as "installation," "connection," "joining," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in the embodiments of this application according to the specific circumstances.

[0082] In the description of the embodiments of this application, unless otherwise expressly specified and limited, the technical term "contact" should be interpreted broadly, and can be direct contact, contact through an intermediate medium layer, contact between two contacting parties with substantially no interaction force, or contact between two contacting parties with interaction force.

[0083] The following is a detailed description of this application.

[0084] Currently, new energy batteries are being used more and more widely in daily life and industry. They are not only widely used in electric vehicles such as electric bicycles, electric motorcycles, and electric cars, as well as in aerospace and other fields, but also in energy storage power systems such as hydropower, thermal power, wind power, and solar power plants. With the rapid development of the energy storage field, higher requirements are being placed on the capacity of secondary batteries used in energy storage devices.

[0085] In addition, the self-discharge rate of secondary batteries not only causes energy loss, but also, under high self-discharge rates, can lead to thermal runaway and even the risk of fire and explosion. Therefore, how to suppress the self-discharge rate of secondary batteries while increasing battery capacity is one of the research topics that the industry needs to study.

[0086] The inventors of this application have noticed that currently, due to the small size of secondary batteries, the size of the electrode components of secondary batteries is limited, resulting in a small capacity of secondary batteries. Moreover, some secondary batteries use a wound structure for their electrode components. The space enclosed by the bends of the wound structure and the corners of the outer casing cannot be effectively utilized, affecting the volumetric energy density of the secondary battery, which also results in a small capacity of the secondary battery.

[0087] The inventors of this application discovered through research that by increasing the size of the secondary battery, the capacity of the secondary battery is increased. Furthermore, by setting the electrode assembly inside the secondary battery to a stacked structure, the space enclosed by the bends of the wound structure and the corners of the outer casing can be eliminated, thereby increasing the volumetric energy density of the secondary battery and further increasing its capacity.

[0088] However, the inventors of this application also noticed that increasing the size of the secondary battery and setting the electrode assembly to a stacked structure caused an increase in the self-discharge rate of the secondary battery due to the increased burrs on the electrode assembly. Therefore, the inventors of this application conducted further research and discovered that thickening the separator of the electrode assembly can reduce the probability of the separator being punctured by burrs, thereby suppressing the self-discharge rate of the secondary battery.

[0089] Based on this design concept, the inventors of this application have designed a secondary battery. The secondary battery includes a casing and at least one electrode assembly. The electrode assembly is disposed within a receiving cavity. The electrode assembly includes stacked positive electrode plates, a separator, and a negative electrode plate. The positive electrode plate includes a positive current collector and a positive active material layer attached to at least one surface of the positive current collector. The material of the positive active material layer includes lithium phosphate. The negative electrode plate includes a negative current collector and a negative active material layer attached to at least one surface of the negative current collector. The material of the negative active material layer includes graphite. The separator includes a substrate layer and a reinforcing layer attached to at least one surface of the substrate layer. The total thickness of the reinforcing layers attached to the same substrate layer is not less than 1 μm. The length and width of the main surface of the casing are in the range of 260 mm to 475 mm and 160 mm to 300 mm, respectively. The capacity of the secondary battery is not less than 300 Ah.

[0090] The positive electrode active material layer of this design includes lithium phosphate, and the negative electrode active material layer includes graphite, making this secondary battery suitable for energy storage devices. This design increases the size of the secondary battery by limiting the length and width of the outer casing to the ranges of 260mm–475mm and 160mm–300mm, respectively, while maintaining a minimum capacity of 300Ah. The electrode assembly size is also increased, further enhancing the battery's capacity. Furthermore, by using a stacked electrode assembly structure, the space enclosed by the bends and corners of the casing in a wound structure is eliminated, improving the volumetric energy density and further increasing the battery's capacity. To address the high probability of burr punctures in the separator caused by the stacked structure, the thickness of the separator's reinforcing layer is limited to a relatively large range, reducing the likelihood of burr punctures and thus lowering the self-discharge rate of the high-capacity secondary battery. Therefore, this design increases the battery's capacity while simultaneously reducing its self-discharge rate. In addition, due to profit considerations, power batteries have a stronger requirement for small footprint than energy storage devices. Therefore, suppressing self-discharge rate by thickening the separator is more suitable for secondary batteries in energy storage devices.

[0091] A secondary battery is a battery that can be recharged after discharge to activate its active materials and continue to be used. In the embodiments of this application, a secondary battery refers to a single battery cell, a battery module, or a battery pack.

[0092] In the embodiments of this application, "multiple" means two or more. The battery cells provided in the embodiments of this application can be grouped into multiple groups to form a battery cell assembly, used to provide voltage and capacity. Multiple battery cells in a battery cell assembly can be connected in series, parallel, or in a mixed configuration via a busbar.

[0093] The battery cells provided in this application embodiment can be applied to battery devices. A battery device may include one or more battery cell assemblies for providing voltage and capacity. A battery cell assembly may include multiple battery cells, which are connected in series, parallel, or mixed connections via a busbar.

[0094] In some embodiments, a battery cell assembly is typically formed by arranging multiple battery cells; as an example, a battery cell assembly can be a battery module, which is formed by arranging and fixing multiple battery cells together to form a single module. As an example, a battery module can be formed by bundling multiple battery cells together with cable ties.

[0095] In some embodiments, the battery device may be a battery pack, which includes a battery case and one or more individual battery cells housed within the battery case.

[0096] As an example, a battery cell assembly can be a battery module, which can be housed in a battery case by fixing the battery module in the battery case.

[0097] As an example, battery cell assemblies can also be housed in a battery box by directly fixing multiple battery cells to the battery box.

[0098] The secondary battery provided in this application embodiment can be applied to energy storage devices, which include energy storage boxes, with a door on at least one side of the energy storage box. Energy storage devices include energy storage containers, energy storage cabinets, etc.

[0099] In the following embodiments, for ease of understanding, the description is provided in conjunction with the accompanying drawings.

[0100] Figure 1 This is a three-dimensional structural schematic diagram of an energy storage device 1000 according to one or more embodiments.

[0101] Reference Figure 1The energy storage device 1000 may include an energy storage housing 200 and at least one battery pack 100 housed within the energy storage housing 200. The energy storage device 1000 may also include a communication interface 210 and a power transmission interface 220 disposed within the energy storage housing 200. In some embodiments, the energy storage housing 200 may be internally divided into a battery compartment and an electrical compartment. The battery pack 100 is typically placed in the battery compartment, while the main control module, master control module, etc., are typically located in the electrical compartment. The communication interface 210 and the power transmission interface 220 can be electrically connected to the main control module, master control module, etc., within the electrical compartment.

[0102] Figure 2 This is an exploded perspective view of a battery pack 100 according to one or more embodiments.

[0103] In some embodiments of this application, such as Figure 2 As shown, the battery pack 100 includes a battery case 10 and at least one battery cell 20. The battery case 10 has a receiving space, in which at least one battery cell 20 is received.

[0104] In some embodiments of this application, the battery box 10 includes a box body 102 and a box cover 101, with the box cover 101 covering the box body 102, thereby forming the receiving space between the box body 102 and the box cover 101.

[0105] The housing 102 can be a hollow structure with one open end, and the cover 101 can be a plate-like structure. The cover 101 closes onto the open side of the housing 102 so that the cover 101 and the housing 102 together define the receiving space. Alternatively, both the cover 101 and the housing 102 can be hollow structures with one open side, and the open side of the cover 101 closes onto the open side of the housing 102. Of course, the battery box 10 formed by the cover 101 and the housing 102 can be of various shapes, such as a cylinder, a cuboid, etc.

[0106] In the battery pack 100, there can be multiple battery cells 20, which can be connected in series, parallel, or in a mixed configuration. A mixed configuration means that multiple battery cells 20 are connected in both series and parallel configurations. Multiple battery cells 20 can be directly connected in series, parallel, or in a mixed configuration, and then the entire assembly of multiple battery cells 20 is placed in the receiving space formed by the housing 102 and the cover 101. Alternatively, the battery pack 100 can also be composed of multiple battery cells 20 first connected in series, parallel, or in a mixed configuration to form battery modules, and then these battery modules are connected in series, parallel, or in a mixed configuration to form a whole, which is then housed within the receiving space formed by the housing 102 and the cover 101. The battery pack 100 may also include other structures; for example, it may include a busbar component for electrical connection between the multiple battery cells 20.

[0107] In the following embodiments, for ease of explanation, the secondary battery of some embodiments of this application is used as an example of battery cell 20. Referring to the following... Figures 3 to 8 A detailed explanation will be provided.

[0108] Figure 3 A cross-sectional view of a battery cell according to one or more embodiments; Figure 4 A cross-sectional view of a spacer according to one or more embodiments. Figure 1 ; Figure 5 A cross-sectional view of a spacer according to one or more embodiments. Figure 2 ; Figure 6 A three-dimensional structural schematic diagram of a battery cell according to one or more embodiments; Figure 7 An exploded perspective view of a battery cell according to one or more embodiments; Figure 8 A cross-sectional view of a spacer according to one or more embodiments. Figure 3 .

[0109] For ease of explanation, a first direction, a second direction, and a third direction are defined, and these three directions are perpendicular. For ease of understanding of the embodiments of this application, as shown... Figures 1 to 7 As shown by the arrows in the diagram, the direction of arrow X is the first direction, the direction of arrow Y is the second direction, and the direction of arrow Z is the third direction.

[0110] like Figures 3 to 6 As shown, the battery cell 20 includes a housing 1 and at least one electrode assembly 2. The housing 1 has a receiving cavity. At least one electrode assembly 2 is disposed in the receiving cavity. The electrode assembly 2 includes a stacked positive electrode 21, a separator 22, and a negative electrode 23. The positive electrode 21 includes a positive current collector and a positive active material layer attached to at least one surface of the positive current collector. The material of the positive active material layer includes lithium phosphate. The negative electrode 23 includes a negative current collector and a negative active material layer attached to at least one surface of the negative current collector. The material of the negative active material layer includes graphite. The separator 22 includes a substrate layer 221 and a reinforcing layer 222 attached to at least one surface of the substrate layer 221. The total thickness of the reinforcing layers 222 attached to the same substrate layer 221 is not less than 1 μm. The length and width of the large surface of the housing 1 are in the range of 260 mm to 475 mm and 160 mm to 300 mm, respectively. The capacity of the battery cell 20 is not less than 300 Ah.

[0111] Electrode assembly 2 is the component in the battery cell 20 where the electrochemical reaction occurs. The casing 1 may contain one or more electrode assemblies 2. Electrode assembly 2 includes a positive electrode 21, a negative electrode 23, and a separator. The battery cell 20 primarily operates by the movement of metal ions between the positive electrode 21 and the negative electrode 23. The positive electrode 21 includes a positive current collector and a positive active material layer, the positive active material layer being coated on the surface of the positive current collector; the positive current collector includes a positive current collector portion and a positive current collector protruding from the positive current collector portion, the positive current collector portion being coated with the positive active material layer, and at least a portion of the positive current collector protruding from the positive current collector portion not coated with the positive active material layer, the positive current collector protruding from the positive current collector portion serving as a positive electrode tab 211. Taking a lithium-ion battery as an example, the material of the positive current collector can be aluminum. The negative electrode 23 includes a negative electrode current collector and a negative electrode active material layer, the negative electrode active material layer being coated on the surface of the negative electrode current collector; the negative electrode current collector includes a negative electrode current collection portion and a negative electrode protrusion protruding from the negative electrode current collection portion, the negative electrode current collection portion being coated with the negative electrode active material layer, and at least a portion of the negative electrode protrusion not being coated with the negative electrode active material layer, the negative electrode protrusion serving as a negative electrode tab 231. The material of the negative electrode current collector can be copper. To ensure that a large current can pass through without melting, there are multiple positive electrode tabs 211 stacked together, and there are multiple negative electrode tabs 231 stacked together.

[0112] Examples of lithium phosphates include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO4, also known as LFP), lithium iron phosphate and carbon composites, lithium manganese phosphate (such as LiMnPO4), lithium manganese phosphate and carbon composites, lithium manganese iron phosphate, and lithium manganese iron phosphate and carbon composites. The material of the negative electrode active material layer may include, but is not limited to, at least one of artificial graphite and natural graphite.

[0113] In some embodiments, attachment refers to adhesion, coating, or spraying.

[0114] For example, such as Figure 4 As shown, a reinforcing layer 222 is attached to one surface of the substrate layer 221. This means that one of the two opposing surfaces of the substrate layer 221 along its thickness direction has a reinforcing layer 222 attached, while the other does not. Thus, the total thickness of the reinforcing layers 222 attached to the same substrate layer 221 is the thickness of the reinforcing layers 222 attached to one surface of the substrate layer 221. See also Figure 4 The total thickness of the reinforcing layer 222 attached to the same substrate layer 221 is the dimension L1, and L1≥1μm.

[0115] For example, such as Figure 5As shown, reinforcing layers 222 are attached to both surfaces of the substrate layer 221. This means that reinforcing layers 222 are attached to both opposite surfaces of the substrate layer 221 along its thickness direction. Thus, the total thickness of the reinforcing layers 222 attached to the same substrate layer 221 is the sum of the thicknesses of the two reinforcing layers 222 attached to the two surfaces of the substrate layer 221. See also Figure 4 The thicknesses of the reinforcing layers 222 attached to the two surfaces of the substrate layer 221 are L1' and L2, respectively, then L1' + L2 ≥ 1 μm. Optionally, the thicknesses of the reinforcing layers 222 attached to the two surfaces of the substrate layer 221 can be the same or different. For example, the combined thickness of the reinforcing layers 222 attached to the two surfaces of the substrate layer 221 can be, but is not limited to, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, and 7 μm.

[0116] For example, the capacity of the battery cell 20 can be, but is not limited to, 300Ah, 310Ah, 320Ah, 330Ah, 340Ah, 350Ah, 360Ah, 370Ah, 380Ah, 390Ah, 400Ah, 410Ah, 420Ah, 430Ah, 440Ah, 450Ah, 460Ah, 470Ah, 480Ah, 490Ah, 500Ah, 600Ah, and 700Ah.

[0117] For example, see Figure 3 The positive electrode 21, the separator 22, and the negative electrode 23 of the electrode assembly 2 are stacked along the first direction X. The two opposite surfaces of the outer casing 1 along the first direction X are the large surfaces 121 of the outer casing 1. The large surface 121 of the outer casing 1 is the surface with the largest area of ​​the outer casing 1. For example, see [reference needed]. Figure 6The dimension W of the large surface 121 along the second direction Y is in the range of 260mm to 475mm. The dimension W of the large surface 121 along the second direction Y can be, but is not limited to, 260mm, 270mm, 280mm, 290mm, 300mm, 310mm, 320mm, 330mm, 340mm, 350mm, 360mm, 370mm, 380mm, 390mm, 400mm, 410mm, 420mm, 430mm, 440mm, 450mm, 460mm, 470mm, and 475mm. The dimension H of the large surface 121 along the third direction Z is in the range of 160mm to 300mm. The dimension H of the large surface 121 along the third direction Z can be, but is not limited to, 160mm, 170mm, 180mm, 190mm, 200mm, 210mm, 220mm, 230mm, 240mm, 250mm, 260mm, 270mm, 280mm, 290mm, and 300mm. It can be understood that the shorter side of the large surface 121 is its width, and the longer side is its length.

[0118] The battery cell 20 provided in this application embodiment has a positive electrode active material layer of positive electrode 21 made of lithium phosphate and a negative electrode active material layer of negative electrode 23 made of graphite, making the battery cell 20 suitable for energy storage devices. This application embodiment limits the length and width of the large surface 121 of the outer casing 1 to the ranges of 260mm to 475mm and 160mm to 300mm respectively, resulting in a larger size for the battery cell 20. Furthermore, the battery cell 20 has a capacity of not less than 300Ah, giving it a large capacity. Moreover, the positive electrode 21 and negative electrode 23 of the electrode assembly 2 are stacked, making the electrode assembly 2 a stacked structure. This eliminates the space enclosed by the bends in the wound structure and the corners of the outer casing, thereby increasing the volumetric energy density of the battery cell 20 and further increasing its capacity. Furthermore, this embodiment addresses the problem of increased burrs caused by the stacked structure, leading to a high probability of puncturing the separator 22. It limits the total thickness of the reinforcing layer 222 attached to the same substrate layer 221 of the separator 22 in the electrode assembly 2 to a relatively large range, reducing the probability of the separator 22 being punctured by burrs and thus reducing the self-discharge rate of the large-capacity battery cell 20. Therefore, this embodiment increases the capacity of the battery cell 20 while also reducing its self-discharge rate. Additionally, power batteries, due to profitability considerations, have a stronger requirement for small footprint than energy storage devices. Therefore, suppressing self-discharge rate by thickening the separator 22 is more suitable for battery cells in energy storage devices.

[0119] In some embodiments of this application, such as Figure 6 and Figure 7 As shown, the outer casing 1 includes a housing 12 and an end cap 11. The housing 12 has an opening, and the end cap 11 closes the opening, forming a receiving cavity with the housing 12.

[0120] End cap 11 refers to a component that covers the opening of housing 12 to isolate the internal environment of battery cell 20 from the external environment. In any case, the shape of end cap 11 can be adapted to the shape of housing 12 to fit it. Optionally, end cap 11 can be made of a material with a certain degree of hardness and strength, so that end cap 11 is not easily deformed under pressure or impact, enabling battery cell 20 to have higher structural strength and improved safety performance.

[0121] An electrode terminal 14 is provided on the end cap 11. The electrode terminal 14 is connected to the positive electrode tab 211 or the negative electrode tab 231 of the electrode assembly 2 for introducing or discharging current. The electrode terminal 14 can be directly connected to the positive electrode tab 211 or the negative electrode tab 231, or it can be connected to the positive electrode tab 211 or the negative electrode tab 231 through an adapter piece 15. The end cap 11 may also be provided with a pressure relief mechanism 13 for releasing internal pressure when the internal pressure or temperature of the battery cell 20 reaches a threshold. The pressure relief mechanism 13 can be, but is not limited to, an explosion-proof valve. The end cap 11 can also be made of various materials, such as copper, iron, aluminum, aluminum alloy, steel, titanium alloy, and copper alloy, etc., and this application embodiment does not impose any special limitations on this. In some embodiments of this application, an insulating structure may also be provided on the inner side of the end cap 11. The insulating structure can be used to isolate the electrical connection components in the housing 12 from the end cap 11 to reduce the risk of short circuit. For example, the insulating structure can be plastic, rubber, etc.

[0122] The housing 12 is a component used to cooperate with the end cap 11 to form the internal environment of the battery cell 20, wherein the formed internal environment can accommodate the electrode assembly 2, electrolyte, and other components. The housing 12 and the end cap 11 are independent components. An opening is provided on the housing 12, and the end cap 11 closes the opening to form the internal environment of the battery cell 20. Specifically, the shape of the housing 12 can be determined according to the specific shape and size of the electrode assembly 2. The material of the housing 12 can be various, such as copper, iron, aluminum, aluminum alloy, plastic, steel, titanium alloy, and copper alloy, etc., and this application embodiment does not impose any special limitations on this. The large surface 121 can be one surface of the housing 12.

[0123] In some embodiments of this application, such as Figure 7 As shown, the housing 1 contains two or more electrode assemblies 2 arranged along the stacking direction of the electrode assemblies 2.

[0124] In some embodiments of this application, the length of the large surface 121 is in the range of 310mm to 370mm, and / or the width of the large surface 121 is in the range of 190mm to 230mm.

[0125] For example, such as Figure 6 As shown, the dimension of the large surface 121 of the outer shell 1 along the second direction Y is the length of the large surface 121, and the dimension along the third direction Z is the width of the large surface 121. The dimension W of the large surface 121 along the second direction Y can be, but is not limited to, 310mm, 311mm, 312mm, 313mm, 314mm, 315mm, 316mm, 317mm, 318mm, 319mm, 320mm, 321mm, 322mm, 323mm, 324mm, 325mm, 326mm, 327mm, 328mm, 329mm, 330mm, 331mm, 332mm, 333mm, 334mm, 335mm, 336mm, 337mm, 3... 38mm, 339mm, 340mm, 341mm, 342mm, 343mm, 344mm, 345mm, 346mm, 347mm, 348mm, 349mm, 350mm, 351mm, 352mm, 353mm, 354mm, 355mm, 356mm, 357mm, 358mm, 359mm, 360mm, 361mm, 362mm, 363mm, 364mm, 365mm, 367mm, 368mm, 369mm, 370mm. For example, the dimension H of the large surface 121 of the housing 1 along the third direction Z can be, but is not limited to, 190mm, 191mm, 192mm, 193mm, 194mm, 195mm, 196mm, 197mm, 198mm, 199mm, 200mm, 201mm, 202mm, 203mm, 204mm, 205mm, 206mm, 207mm, 208mm, 209mm, 210mm, 211mm, 212mm, 213mm, 214mm, 215mm, 216mm, 217mm, 218mm, 219mm, 220mm, 221mm, 222mm, 223mm, 224mm, 225mm, 226mm, 227mm, 228mm, 229mm, and 230mm.

[0126] Thus, by limiting the length of the large surface 121 to the range of 310mm to 370mm, and / or limiting the width of the large surface 121 to the range of 190mm to 230mm, the size of the battery cell 20 is larger, and the number of battery cells 20 that can be accommodated in a certain volume of space is smaller. This reduces the space occupied by the outer casing 1 of the battery cell 20, thereby increasing the space occupied by the electrode assembly 2 of the battery cell 20. In other words, the volumetric energy density in a certain volume of space is increased.

[0127] In some embodiments of this application, the total thickness of the reinforcing layer 222 attached to the same substrate layer 221 is in the range of 2μm to 4μm.

[0128] It is understandable that when reinforcing layers 222 are attached to both surfaces of the substrate layer 221, the sum of the thicknesses of the two reinforcing layers 222 is in the range of 2μm to 4μm. When reinforcing layers 222 are attached to only one surface of the substrate layer 221, the thickness of the reinforcing layer 222 is in the range of 2μm to 4μm.

[0129] For example, the total thickness of the reinforcing layer 222 attached to the same substrate layer 221 can be, but is not limited to, 2μm, 2.1μm, 2.2μm, 2.3μm, 2.4μm, 2.5μm, 2.6μm, 2.7μm, 2.8μm, 2.9μm, 3μm, 3.1μm, 3.2μm, 3.3μm, 3.4μm, 3.5μm, 3.6μm, 3.7μm, 3.8μm, 3.9μm, and 4μm.

[0130] By limiting the total thickness of the reinforcing layer 222 attached to the same substrate layer 221 to the range of 2μm to 4μm, the thickness of the separator 22 is within a suitable range, which can reduce the probability of the separator 22 being punctured by burrs, and prevent the separator 22 from being too thick, thus avoiding excessive impact on the internal resistance and capacity of the battery cell 20.

[0131] In some embodiments of this application, a reinforcing layer 222 is attached to both surfaces of the substrate layer 221, and the two reinforcing layers 222 have the same thickness.

[0132] This ensures uniform strength on both sides of the substrate layer 221, further reducing the risk of the spacer 22 being punctured.

[0133] In some embodiments of this application, the substrate layer 221 is made of polyethylene.

[0134] In some embodiments of this application, the substrate layer 221 is made of polypropylene.

[0135] In some embodiments of this application, the substrate layer 221 includes a polyethylene layer and a polypropylene layer laminated with the polyethylene layer.

[0136] In some embodiments of this application, such as Figure 4 and Figure 5 As shown, the thickness L3 of the separator 22 is in the range of 7μm to 20μm.

[0137] The thickness of the spacer 22 is the total thickness of the spacer 22, including the thickness of the substrate layer 221 and the thickness of the reinforcing layer 222 attached to the substrate layer 221. For example, the spacer 22 is composed of the substrate layer 221 and two reinforcing layers 222, and the thickness of the spacer 22 is the sum of the thicknesses of the substrate layer 221 and the two reinforcing layers 222.

[0138] For example, the thickness L3 of the spacer 22 can be, but is not limited to, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm, 15μm, 16μm, 17μm, 18μm, 19μm, or 20μm.

[0139] Thus, by limiting the thickness of the separator 22 to the range of 7μm to 20μm, the probability of the separator 22 being punctured by burrs can be reduced, and the internal resistance and capacity of the battery cell will not be affected too much due to the separator 22 being too thick.

[0140] In some embodiments of this application, the thickness L3 of the spacer 22 is between 9 μm and 14 μm.

[0141] For example, the thickness L3 of the spacer 22 can be, but is not limited to, 9μm, 9.1μm, 9.2μm, 9.3μm, 9.4μm, 9.5μm, 9.6μm, 9.7μm, 9.8μm, 9.9μm, 10μm, 10.1μm, 10.2μm, 10.3μm, 10.4μm, 10.5μm, 10.6μm, 10.7μm, 10.8μm, 10.9μm, 11μm, 11.1μm, 11.2μm, 11.3μm, 11.4μm, etc. μm, 11.5μm, 11.6μm, 11.7μm, 11.8μm, 11.9μm, 12μm, 12.1μm, 12.2μm, 12.3μm, 12.4μm, 12.5μm, 12.6μm, 12.7 μm, 12.8μm, 12.9μm, 13μm, 13.1μm, 13.2μm, 13.3μm, 13.4μm, 13.5μm, 13.6μm, 13.7μm, 13.8μm, 13.9μm, 14μm.

[0142] Thus, by limiting the thickness of the separator 22 to the range of 9μm to 14μm, the probability of the separator 22 being punctured by burrs can be reduced, and the internal resistance and capacity of the battery cell will not be affected too much due to the separator 22 being too thick.

[0143] In some embodiments of this application, the positive current collector forms a positive electrode tab 211 at at least one end along the width direction of the large surface 121, and the negative current collector forms a negative electrode tab 231 at at least one end along the width direction of the large surface 121. The length-to-width ratio of the large surface 121 of the outer casing 1 is in the range of 1 to 3.

[0144] For example, such as Figure 6 and Figure 7 As shown, the positive current collector forms a positive electrode tab 211 at one end along the third direction Z, and the negative current collector forms a negative electrode tab 231 at one end along the third direction Z. The dimension H of the large surface 121 along the third direction Z is the width of the large surface 121, and the dimension W along the second direction Y is the length of the large surface 121. The ratio of the dimension W of the large surface 121 along the second direction Y to the dimension H along the third direction Z can be, but is not limited to, 1, 1.5, 2, 2.5, or 3.

[0145] By limiting the length-to-width ratio of the large surface 121 of the outer shell 1 to the range of 1 to 3, not only can the electron transport path be shortened, but the uniformity of the current density can also be improved, thereby increasing the energy conversion efficiency.

[0146] In some embodiments of this application, the positive current collector forms a positive electrode tab 211 at at least one end along the width direction of the large surface 121, and the negative current collector forms a negative electrode tab 231 at at least one end along the width direction of the large surface. The ratio of the length to the width of the large surface 121 of the outer casing 1 is in the range of 1.1 to 2.

[0147] For example, the ratio of the dimension W of the large surface 121 of the outer shell 1 along the second direction Y to the dimension H along the third direction Z can be, but is not limited to, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, or 2.

[0148] By limiting the length-to-width ratio of the large surface 121 of the outer shell 1 to the range of 1.1 to 2, not only can the electron transport path be shortened, but the uniformity of the current density can also be improved, thereby increasing the energy conversion efficiency.

[0149] In some embodiments of this application, such as Figure 6 As shown, the dimension T of the outer shell 1 along the direction perpendicular to the large surface 121 is in the range of 50mm to 100mm.

[0150] For example, the first direction X is perpendicular to the large surface 121, and the size T of the outer shell 1 along the first direction X can be, but is not limited to, 50mm, 55mm, 60mm, 65mm, 70mm, 75mm, 80mm, 85mm, 90mm, 95mm, and 100mm.

[0151] Thus, by limiting the dimension T of the outer casing 1 in the direction perpendicular to the large surface 121 to the range of 50mm to 100mm, the size of the battery cell 20 is made larger, thereby increasing the volumetric energy density within a certain volume of the containment space.

[0152] In some embodiments of this application, the size of the outer shell 1 in the direction perpendicular to the large surface 121 is in the range of 60mm to 80mm.

[0153] For example, the first direction X is perpendicular to the large surface 121, and the size T of the outer shell 1 along the first direction X can be, but is not limited to, 60mm, 61mm, 62mm, 63mm, 64mm, 65mm, 66mm, 67mm, 68mm, 69mm, 70mm, 71mm, 72mm, 73mm, 74mm, 75mm, 76mm, 77mm, 78mm, 79mm, and 80mm.

[0154] Thus, by limiting the size T of the outer casing 1 in the direction perpendicular to the large surface 121 to the range of 60mm to 80mm, the size of the battery cell 20 is made larger, thereby increasing the volumetric energy density within a certain volume of the containment space.

[0155] In some embodiments of this application, the capacity of the battery cell 20 is not less than 500Ah.

[0156] For example, the capacity of the battery cell 20 can be, but is not limited to, 500Ah, 510Ah, 520Ah, 530Ah, 540Ah, 550Ah, 560Ah, 570Ah, 580Ah, 590Ah, 600Ah, 610Ah, 620Ah, 630Ah, 640Ah, 650Ah, 660Ah, 670Ah, 680Ah, 690Ah, and 700Ah.

[0157] In this way, by limiting the capacity of the battery cell 20 to no less than 500Ah, the battery cell 20 has a large capacity, thereby increasing the energy density and achieving the cost reduction requirement.

[0158] In some embodiments of this application, the reinforcing layer 222 includes inorganic particles and organic particles.

[0159] The reinforcing layer 222 includes inorganic and organic particles. On the one hand, it can improve the strength of the separator 22 and reduce the risk of puncture. On the other hand, it can improve the interface between the positive electrode 21 and the negative electrode 23 in the electrode assembly 2 and the separator 22, reduce the risk of wrinkling, and improve the performance of the battery cell 20. In addition, the organic particles can leave gaps between the positive electrode 21 and the negative electrode 23 and the separator 22, thereby mitigating the expansion of the battery cell 20 during charging and discharging.

[0160] In some embodiments of this application, such as Figure 8 As shown, the reinforcing layer 222 includes a first reinforcing layer 2221 attached to the surface of the substrate layer 221 and a second reinforcing layer 2222 attached to the surface of the first reinforcing layer 2221 facing away from the substrate layer 221. The material of the first reinforcing layer 2221 includes inorganic particles, and the material of the second reinforcing layer 2222 includes organic particles.

[0161] For example, inorganic particles are uniformly and densely coated on the surface of the substrate layer 221 to form a first reinforcing layer 2221, and organic particles are dispersedly coated on the surface of the first reinforcing layer 2221 to form a second reinforcing layer 2222.

[0162] Thus, the layering of inorganic and organic particles can improve the strength of the separator 22 and reduce the risk of puncture. On the other hand, it can improve the interface between the positive electrode 21 and the negative electrode 23 and the separator 22 in the electrode assembly 2, reduce the risk of wrinkling, and improve the performance of the battery cell 20. In addition, the organic particles can leave gaps between the positive electrode 21 and the negative electrode 23 and the separator 22, thereby mitigating the expansion of the battery cell 20 during charging and discharging.

[0163] In some embodiments of this application, the reinforcing layer 222 includes an inorganic particle layer attached to the surface of the substrate layer 221 and organic particles embedded in the inorganic particle layer, wherein the organic particles form protrusions on the surface of the inorganic particle layer.

[0164] Thus, the partial embedding of organic particles into the inorganic particle layer can, on the one hand, improve the strength of the separator 22 and reduce the risk of puncture; on the other hand, it can improve the interface between the positive electrode 21 and the negative electrode 23 in the electrode assembly 2 and the separator 22, reduce the risk of wrinkling, and improve the performance of the battery cell 20; in addition, the organic particles can leave gaps between the positive electrode 21 and the negative electrode 23 and the separator 22, thereby mitigating the degree of expansion of the battery cell 20 during charging and discharging.

[0165] In some embodiments of this application, the average particle size of the organic particles is in the range of 2 μm to 25 μm.

[0166] For example, the average particle size of the organic particles can be, but is not limited to, 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm, 15μm, 16μm, 17μm, 18μm, 19μm, 20μm, 21μm, 22μm, 23μm, 24μm, and 25μm.

[0167] If the particle size of the organic particles is too large, they tend to form large sheets of adhesive film, thus affecting ion conduction. If the particle size is too small, it will affect the dispersion of the organic particles on the substrate layer 221 and will hardly serve its purpose of leaving gaps between the positive electrode 21 and the negative electrode 23 and the separator 22, thus affecting the performance of the battery cell 20. Therefore, the embodiments of this application limit the average particle size of the organic particles to the range of 2μm to 25μm, which not only improves ion conduction but also leaves gaps, thereby improving the performance of the battery cell 20.

[0168] In some embodiments of this application, the average particle size of the organic particles is between 4 μm and 20 μm.

[0169] For example, the average particle size of the organic particles can be, but is not limited to, 4μm, 4.5μm, 5μm, 5.5μm, 6μm, 6.5μm, 7μm, 7.5μm, 8μm, 8.5μm, 9μm, 9.5μm, 10μm, 10.5μm, 11μm, 11.5μm, 12μm, 12.5μm, 13μm, 13.5μm, 14μm, 14.5μm, 15μm, 15.5μm, 16μm, 16.5μm, 17μm, 17.5μm, 18μm, 18.5μm, 19μm, 19.5μm, and 20μm.

[0170] Therefore, by limiting the average particle size of the organic particles to the range of 4μm to 20μm, the embodiments of this application can not only improve the conductivity of ions, but also leave gaps to improve the performance of the battery cell 20.

[0171] In some embodiments of this application, the average particle size of the inorganic particles is no greater than 2.5 μm.

[0172] Thus, by limiting the average particle size of the inorganic particles to no more than 2.5 μm, the use of small-sized inorganic particles is beneficial for the inorganic particles to be coated more uniformly and densely on the substrate layer 221, reducing the risk of the separator 22 being punctured.

[0173] In some embodiments of this application, the average particle size of the inorganic particles is in the range of 0.5 μm to 2.5 μm.

[0174] For example, the average particle size of the inorganic particles can be, but is not limited to, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.7 μm, 1.8 μm, 1.9 μm, 2 μm, 2.1 μm, 2.2 μm, 2.3 μm, 2.4 μm, and 2.5 μm.

[0175] In this way, the average particle size of the inorganic particles is limited to the range of 0.5μm to 2.5μm, which makes the inorganic particles smaller and more uniformly and densely coated on the substrate layer 221, reducing the risk of the separator 22 being punctured.

[0176] In some embodiments of this application, the organic particles include at least one of the following: homopolymers or copolymers of fluoroolefin monomer units, homopolymers or copolymers of olefin monomer units, homopolymers or copolymers of unsaturated nitrile monomer units, homopolymers or copolymers of epoxy alkane monomer units, homopolymers or copolymers of acrylic monomer units, homopolymers or copolymers of acrylate monomer units, homopolymers or copolymers of styrene monomer units, polyurethane compounds, rubber compounds, and modified compounds of the above homopolymers or copolymers.

[0177] For example, the fluoroolefin monomer unit may be selected from at least one of vinylidene fluoride, vinyl fluoride, trifluoroethylene, trifluorochloroethylene, tetrafluoroethylene, and hexafluoropropylene. The olefin monomer unit may be selected from at least one of ethylene, propylene, butadiene, and isoprene. The unsaturated nitrile monomer unit may be selected from at least one of acrylonitrile and methacrylonitrile. The epoxide monomer unit may be selected from at least one of ethylene oxide and propylene oxide. The acrylic monomer unit may be selected from at least one of acrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate, acrylonitrile, and methyl methacrylate. The acrylate monomer unit may be selected from at least one of methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, methyl methacrylate, butyl methacrylate, and isooctyl methacrylate. The styrene monomer unit may be selected from at least one of styrene and methylstyrene.

[0178] Thus, applying the aforementioned organic particles to the separator 22 can improve the adhesion between the separator and the electrode, and reduce the degree of expansion of the battery cell 20 during charging and discharging.

[0179] In some embodiments of this application, the infinite particles include at least one of boehmite, alumina, silicon dioxide, magnesium oxide, magnesium hydroxide, titanium dioxide, tin dioxide, barium sulfate, calcium oxide, zinc oxide, zirconium oxide, yttrium oxide, cerium oxide, magnesium fluoride, and barium titanate.

[0180] Thus, applying the aforementioned inorganic particles to the separator 22 can enhance the mechanical strength of the separator 22, reduce the probability of the separator 22 being punctured by burrs, and extend the service life of the battery cell 20.

[0181] In some embodiments of this application, the material of the positive electrode active material layer includes lithium iron phosphate, and the material of the negative electrode active material layer includes artificial graphite.

[0182] Thus, the battery cell 20 is a lithium iron phosphate battery, which has advantages such as high thermal stability, high charge and discharge efficiency, low raw material cost, and long cycle life. In addition, the battery cell 20 in this embodiment has a large capacity and low self-discharge rate, making it suitable for use in energy storage devices that require large capacity and high safety performance.

[0183] In some embodiments of this application, the outer casing 1 is made of aluminum and / or steel.

[0184] The outer casing 1 is made of aluminum and / or steel, making it a rigid casing, and the battery cell 20 is a rigid-cased battery cell. This gives the outer casing 1 a certain degree of hardness and strength, making it less prone to deformation under pressure and impact, allowing the battery cell 20 to have higher structural strength and improving safety performance.

[0185] The following describes specific examples of some embodiments of this application with reference to the accompanying drawings.

[0186] As a specific example, a stacked battery cell (cell 20) is provided, including a casing (casing 1) and a bare cell (electrode assembly 2) placed in the casing. The bare cell has a stacked structure, comprising a positive electrode (positive electrode 21), a separator (separator 22), and a negative electrode (negative electrode 23) stacked sequentially along the thickness direction (first direction X). The positive electrode active material of the positive electrode includes lithium iron phosphate, and the negative electrode active material of the negative electrode includes artificial graphite. The tabs of the positive electrode (positive electrode 21) and the tabs of the negative electrode (negative electrode 23) are formed at the same end of the bare cell along the height direction (third direction Z). The thickness direction is perpendicular to the height direction and is perpendicular to the thickness direction. The direction perpendicular to both the direction of width and the direction of height is the width direction (second direction Y). The dimensions of the outer shell along the thickness direction (dimension T) are in the range of 50mm to 100mm, the dimensions along the height direction (dimension H) are in the range of 160mm to 300mm, the dimensions along the width direction (dimension W) are in the range of 260mm to 475mm, the ratio of the dimensions along the width direction to the dimensions along the height direction (W / H) is in the range of 1 to 3, and the capacity of the stacked cell is ≥500Ah. The separator includes a base film layer (substrate layer 221) and a coating layer (reinforcing layer 222) coated on both sides of the base film layer. The sum of the thicknesses of the coating layers on both sides is not less than 1μm, and the thickness of the separator is in the range of 7μm to 20μm. The coating of the diaphragm may include inorganic particles and organic particles; the inorganic particle coating is uniformly and densely distributed on the base membrane layer, and the organic particle coating is dispersed on the inorganic particle coating or partially embedded in the inorganic particle layer. The average particle size of the organic particles is in the range of 2μm to 25μm, and the average particle size of the inorganic particles is not greater than 2.5μm.

[0187] Some embodiments of this application also provide a method for manufacturing a battery cell, the method comprising:

[0188] S1 provides a substrate layer;

[0189] S2, attach reinforcing layers to the two surfaces of the substrate layer to form a separator;

[0190] S3 provides the positive current collector;

[0191] S4, attach a layer of positive active material to at least one surface of the positive current collector to form a positive electrode sheet;

[0192] S5 provides the negative electrode current collector;

[0193] S6, attach a layer of negative electrode active material to at least one surface of the negative electrode current collector to form a negative electrode sheet;

[0194] S7, the positive electrode, the separator and the negative electrode are stacked sequentially along the first direction to form an electrode assembly;

[0195] S8, with a casing;

[0196] S9, at least one electrode assembly is installed inside the housing to form a battery cell.

[0197] The positive electrode active material layer is made of lithium phosphate, the negative electrode active material layer is made of graphite, the separator 22 includes a substrate layer 221 and a reinforcing layer 222 attached to at least one surface of the substrate layer 221, and the total thickness of the reinforcing layer 222 attached to the same substrate layer 221 is not less than 1 μm; the length and width of the large surface of the outer shell 1 are in the range of 260 mm to 475 mm and 160 mm to 300 mm, respectively, and the capacity of the battery cell 20 is not less than 300 Ah.

[0198] The battery cell 20 manufactured in this embodiment has a positive electrode active material layer of positive electrode 21 made of lithium phosphate and a negative electrode active material layer of negative electrode 23 made of graphite, making the battery cell 20 suitable for energy storage devices. This embodiment limits the length and width of the large surface 121 of the outer casing 1 to the ranges of 260mm to 475mm and 160mm to 300mm respectively, resulting in a larger battery cell 20 size. Furthermore, the battery cell 20 has a capacity of not less than 300Ah, giving it a large capacity. Moreover, the positive electrode 21 and negative electrode 23 of the electrode assembly 2 are stacked, making the electrode assembly 2 a stacked structure. This eliminates the space enclosed by the bends in the wound structure and the corners of the outer casing, increasing the volumetric energy density of the battery cell 20 and further increasing its capacity. Furthermore, this embodiment addresses the problem of increased burrs caused by the stacked structure, leading to a high probability of puncturing the separator 22. It limits the total thickness of the reinforcing layer 222 attached to the same substrate layer 221 of the separator 22 in the electrode assembly 2 to a relatively large range, reducing the probability of the separator 22 being punctured by burrs and thus reducing the self-discharge rate of the large-capacity battery cell 20. Therefore, this embodiment increases the capacity of the battery cell 20 while also reducing its self-discharge rate. Additionally, power batteries, due to profitability considerations, have a stronger requirement for small footprint than energy storage devices. Therefore, suppressing self-discharge rate by thickening the separator 22 is more suitable for battery cells in energy storage devices.

[0199] Some embodiments of this application provide an energy storage device 1000, which includes a plurality of battery packs 100, each battery pack 100 including a battery box 10 and a plurality of battery cells 20, the battery cells 20 being housed in the battery box 10.

[0200] Energy storage devices include energy storage containers, energy storage cabinets, etc.

[0201] Since the energy storage device 1000 includes a battery cell 20, and the battery cell 20 has a large capacity and a low self-discharge rate, the energy storage device 1000 has a large capacity and a low self-discharge rate.

[0202] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0203] Example 1

[0204] Preparation of positive electrode sheet

[0205] A slurry containing lithium iron phosphate is coated on both sides of an aluminum foil, dried, and cold-pressed to obtain a positive electrode sheet.

[0206] Preparation of negative electrode sheet

[0207] A slurry containing artificial graphite is coated on both sides of a copper foil, dried, and cold-pressed to obtain a negative electrode sheet.

[0208] Preparation of the isolation component

[0209] An inorganic particle coating (boehmite) is applied to both surfaces of a polyethylene film, and an organic particle coating (polyvinylidene fluoride) is applied to the surface of the inorganic particle coating to obtain a separator. The inorganic particle coating and the organic particle coating on the same side of the polyethylene film constitute a reinforcing layer.

[0210] Preparation of the outer shell

[0211] The cubic shell is manufactured using a stamping process.

[0212] Assembly of battery cells

[0213] A positive electrode, a separator, and a negative electrode are stacked in sequence to form an electrode assembly. At least one electrode assembly is then inserted into the casing to form a battery cell.

[0214] Testing the capacitance of individual battery cells

[0215] At 25℃ and normal pressure, a single battery cell (20 cells) was discharged to 2.5V at a constant power of 0.5P and allowed to stand for 30 minutes. Then it was charged to 3.65V at a constant power of 0.5P, allowed to stand for 5 minutes, and then charged to 3.65V at a constant power of 0.05P, allowed to stand for 30 minutes. Finally, it was discharged to 2.5V at a constant power of 0.5P. The discharge capacity recorded is the capacity of the battery cell.

[0216] Self-discharge rate test of individual battery cells .

[0217] At 25℃ and normal pressure, a single battery cell 20 was charged to 3.35V at a constant power of 0.5P, left to stand for 1 hour, and the open-circuit voltage V1 of battery cell 20 was tested and recorded. After leaving the battery cell 20 to stand for 48 hours, the open-circuit voltage V2 of battery cell 20 was tested and recorded again. The self-discharge rate of battery cell 20 is K = (V1 - V2) / 48.

[0218] Example 2

[0219] The battery cells were prepared using the same steps as in Example 1, except that the thicknesses of the two reinforcing layers were adjusted as shown in Table 1, and the battery cells were subjected to capacity and self-discharge rate tests. The test results are recorded in Tables 1 and 2.

[0220] Comparative Example 1

[0221] The battery cells were prepared using the same steps as in Example 1, except that the thicknesses of the two reinforcing layers were adjusted as shown in Table 1. The battery cells were then subjected to capacity and self-discharge rate tests, and the test results are recorded in Table 1.

[0222] Comparative Example 2

[0223] The battery cells were prepared using the same steps as in Example 1, except that the thicknesses of the two reinforcing layers were adjusted as shown in Table 1. The battery cells were then subjected to capacity and self-discharge rate tests, and the test results are recorded in Table 1.

[0224] Table 1

[0225]

[0226] As shown in Table 1, as the sum of the thicknesses of the two reinforcing layers 222 increases, the self-discharge rate of the battery cell 20 gradually decreases. Furthermore, the self-discharge rate of the battery cell 20 with a sum of the thicknesses of the two reinforcing layers 222 less than 1 μm is significantly greater than that of the battery cell 20 with a sum of the thicknesses of the two reinforcing layers 222 not less than 1 μm. Therefore, in the embodiments of this application, the sum of the thicknesses of the two reinforcing layers 222 is limited to not less than 1 μm, which can reduce the self-discharge rate of the battery cell 20.

[0227] Example 3

[0228] The battery cells were prepared using the same steps as in Example 1, except that the thicknesses of the two reinforcing layers were adjusted as shown in Table 2. The battery cells were then subjected to capacity and self-discharge rate tests, and the test results are recorded in Table 2.

[0229] Example 4

[0230] The battery cells were prepared using the same steps as in Example 1, except that the thicknesses of the two reinforcing layers were adjusted as shown in Table 2. The battery cells were then subjected to capacity and self-discharge rate tests, and the test results are recorded in Table 2.

[0231] Table 2

[0232]

[0233] As shown in Table 2, with the increase of the sum of the thicknesses of the two reinforcing layers 222, the self-discharge rate of the battery cell 20 gradually decreases, while the capacity of the battery cell 20 gradually decreases. Therefore, some embodiments of this application limit the sum of the thicknesses of the two reinforcing layers 222 to an upper limit of 4 μm, which can result in a relatively high capacity of the battery cell 20, and limit the sum of the thicknesses of the two reinforcing layers 222 to a lower limit of 2 μm, which can reduce the self-discharge rate of the battery cell 20. Therefore, some embodiments of this application limit the sum of the thicknesses of the two reinforcing layers 222 to the range of 2 μm to 4 μm, which results in both a high capacity and a low self-discharge rate for the battery cell 20.

[0234] The above embodiments are merely illustrative of the technical solutions of this application and are not intended to limit it. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application, and all should be covered within the scope of the specification of this application. In particular, as long as there is no structural conflict, the various technical features mentioned in the embodiments can be combined in any way.

Claims

1. A secondary battery, characterized in that, include: The outer shell has a receiving cavity; At least one electrode assembly is disposed within the receiving cavity. The electrode assembly includes stacked positive electrode sheets, separators, and negative electrode sheets. The positive electrode sheet includes a positive current collector and a positive active material layer attached to at least one surface of the positive current collector. The material of the positive active material layer includes lithium phosphate. The negative electrode sheet includes a negative current collector and a negative active material layer attached to at least one surface of the negative current collector. The material of the negative active material layer includes graphite. The separator includes a substrate layer and a reinforcing layer attached to at least one surface of the substrate layer. The total thickness of the reinforcing layers attached to the same substrate layer is not less than 1 μm. The length and width of the outer shell are respectively in the range of 260mm to 475mm and 160mm to 300mm, and the capacity of the secondary battery is not less than 300Ah.

2. The secondary battery according to claim 1, characterized in that, The length of the large surface is in the range of 310mm to 370mm, and / or The width of the large surface is in the range of 190mm to 230mm.

3. The secondary battery according to claim 1 or 2, characterized in that, The total thickness of the reinforcing layer attached to the same substrate layer is in the range of 2 μm to 4 μm.

4. The secondary battery according to any one of claims 1 to 3, characterized in that, The reinforcing layer is attached to both surfaces of the substrate layer, and the two reinforcing layers have the same thickness.

5. The secondary battery according to any one of claims 1 to 4, characterized in that, The thickness of the insulating element is in the range of 7μm to 20μm.

6. The secondary battery according to any one of claims 1 to 4, characterized in that, The thickness of the isolation element is in the range of 9μm to 14μm.

7. The secondary battery according to any one of claims 1 to 6, characterized in that, The positive current collector forms a positive electrode tab at at least one end along the width direction of the large surface, and the negative current collector forms a negative electrode tab at at least one end along the width direction of the large surface. The ratio of the length to the width of the large surface is in the range of 1 to 3.

8. The secondary battery according to any one of claims 1 to 6, characterized in that, The positive current collector forms a positive electrode tab at at least one end along the width direction of the large surface, and the negative current collector forms a negative electrode tab at at least one end along the width direction of the large surface. The ratio of the length to the width of the large surface is in the range of 1.1 to 2.

9. The secondary battery according to any one of claims 1 to 8, characterized in that, The dimensions of the outer shell in the direction perpendicular to the large surface are in the range of 50mm to 100mm.

10. The secondary battery according to any one of claims 1 to 8, characterized in that, The dimensions of the outer shell in the direction perpendicular to the large surface are in the range of 60mm to 80mm.

11. The secondary battery according to any one of claims 1 to 10, characterized in that, The capacity of the secondary battery is not less than 500Ah.

12. The secondary battery according to any one of claims 1 to 11, characterized in that, The reinforcing layer comprises inorganic particles and organic particles.

13. The secondary battery according to claim 12, characterized in that, The reinforcing layer includes a first reinforcing layer attached to the surface of the substrate layer and a second reinforcing layer attached to the surface of the first reinforcing layer facing away from the substrate layer. The material of the first reinforcing layer includes the inorganic particles, and the material of the second reinforcing layer includes the organic particles.

14. The secondary battery according to claim 12, characterized in that, The reinforcing layer includes an inorganic particle layer attached to the surface of the substrate layer and organic particles embedded in the inorganic particle layer, wherein the organic particles form protrusions on the surface of the inorganic particle layer.

15. The secondary battery according to any one of claims 12 to 14, characterized in that, The average particle size of the organic particles is in the range of 2μm to 25μm.

16. The secondary battery according to any one of claims 12 to 14, characterized in that, The average particle size of the organic particles is in the range of 4 μm to 20 μm.

17. The secondary battery according to any one of claims 12 to 16, characterized in that, The average particle size of the inorganic particles is no greater than 2.5 μm.

18. The secondary battery according to any one of claims 12 to 16, characterized in that, The average particle size of the inorganic particles is in the range of 0.5 μm to 2.5 μm.

19. The secondary battery according to any one of claims 12 to 18, characterized in that, The organic particles include at least one of the following: homopolymers or copolymers of fluoroolefin monomer units, homopolymers or copolymers of olefin monomer units, homopolymers or copolymers of unsaturated nitrile monomer units, homopolymers or copolymers of epoxy alkane monomer units, homopolymers or copolymers of acrylic monomer units, homopolymers or copolymers of acrylate monomer units, homopolymers or copolymers of styrene monomer units, polyurethane compounds, rubber compounds, and modified compounds of the above homopolymers or copolymers.

20. The secondary battery according to any one of claims 12 to 19, characterized in that, The infinite particles include at least one of boehmite, alumina, silicon dioxide, magnesium oxide, magnesium hydroxide, titanium dioxide, tin dioxide, barium sulfate, calcium oxide, zinc oxide, zirconium oxide, yttrium oxide, cerium oxide, magnesium fluoride, and barium titanate.

21. The secondary battery according to any one of claims 1 to 20, characterized in that, The positive electrode active material layer is made of lithium iron phosphate, and the negative electrode active material layer is made of artificial graphite.

22. The secondary battery according to any one of claims 1 to 21, characterized in that, The outer casing is made of aluminum and / or steel.

23. An energy storage device, characterized in that, It includes a plurality of secondary batteries according to any one of claims 1 to 22, the secondary batteries being used to store or provide electrical energy.

24. A method for manufacturing a secondary battery, characterized in that, include: Provide a substrate layer; A reinforcing layer is attached to at least one surface of the substrate layer to form a spacer; Provides positive current collector; A positive electrode active material layer is attached to at least one surface of the positive electrode current collector to form a positive electrode sheet; Provide negative electrode current collector; A negative electrode active material layer is attached to at least one surface of the negative electrode current collector to form a negative electrode sheet; The positive electrode, the separator, and the negative electrode are stacked sequentially along a first direction to form an electrode assembly; Provide a casing; At least one of the electrode components is installed inside the housing to form a secondary battery; The positive electrode active material layer is made of lithium phosphate, the negative electrode active material layer is made of graphite, and the total thickness of the reinforcing layer attached to the substrate layer is not less than 1 μm; the length and width of the outer shell are in the range of 260 mm to 475 mm and 160 mm to 300 mm, respectively, and the capacity of the secondary battery is not less than 300 Ah.

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