Secondary battery cell and electrical apparatus comprising same

Abstract

The present application provides a secondary battery cell and an electrical apparatus comprising same. The secondary battery cell comprises an electrode assembly. The electrode assembly comprises a body, the body comprising a positive electrode sheet, a negative electrode sheet, and a separator. The electrode assembly is a stacked structure. The separator comprises a porous substrate, a first coating layer and a second coating layer, the first coating layer and the second coating layer respectively being located on two opposite surfaces of the porous substrate, and each comprising a granular filler. The thickness of the first coating layer is denoted as T1, and the thickness of the second coating layer is denoted as T2, T1+T2≥5 μm. The length of the secondary battery cell is 500 mm-1200 mm.

Description

Secondary battery cell and electric device containing same

[0001] Related Applications

[0002] The present application claims priority to the Chinese patent application No. 2024110950767, filed on August 9, 2024, entitled "Secondary battery cell and electric device containing same", the contents of which are hereby incorporated by reference in its entirety. TECHNICAL FIELD

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

[0004] In recent years, secondary batteries are widely used in energy storage power systems such as hydroelectric, thermal, wind and solar power stations, and in many fields such as electric tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace, etc.

[0005] How to make the battery have both high energy density and good safety performance is still a technical problem to be solved in the field. SUMMARY

[0006] Based on the above problems, the first aspect of the present application provides a secondary battery cell, comprising a shell, an end cover and an electrode terminal. The shell has an opening. The end cover is used to cover the opening. The electrode terminal is arranged on the end cover. The electrode assembly is accommodated in the shell. The electrode assembly comprises a body, the body comprises a positive electrode sheet, a negative electrode sheet and a separator film, and the electrode assembly is a laminated structure. The separator film comprises a porous substrate, a first coating layer and a second coating layer, the first coating layer and the second coating layer are respectively located on the two opposite surfaces of the porous substrate, and the first coating layer and the second coating layer both comprise a granular filler. The thickness of the first coating layer is denoted as T1, the thickness of the second coating layer is denoted as T2, then T1+T2≥5μm. And the length of the secondary battery cell is 500mm-1200mm.

[0007] The secondary battery cell of the present application controls the size of the battery within a certain range, and adopts a laminated structure, which can effectively improve the energy density of the battery; at the same time, the thickness of the coating layer of the separator film is controlled within a certain range, which can effectively reduce the pressure drop of the battery, thereby improving the storage safety performance of the battery.

[0008] In some embodiments, 6μm≤T1+T2≤9μm.

[0009] In some embodiments, 6μm≤T1+T2≤8μm.

[0010] In some embodiments, the length of the secondary battery cell is 600mm-1100mm.

[0011] In some embodiments, the width of the secondary battery cell is 120-140 mm. The width of the secondary battery cell in this range can enable the secondary battery cell to have a higher volumetric energy density, and enable the electrolyte to maintain a good wetting effect on the electrode assembly, thereby enabling the secondary battery to have good cycle performance.

[0012] In some embodiments, the width of the secondary battery cell is 120-130 mm.

[0013] In some embodiments, the thickness of the secondary battery cell is 13-28 mm.

[0014] In some embodiments, the aspect ratio of the secondary battery cell is 5-12. The aspect ratio of the secondary battery cell in this range can enable more secondary battery cells to be better arranged as a whole, further promoting the improvement of the energy density of the battery.

[0015] In some embodiments, the width-to-thickness ratio of the secondary battery cell is 3.2-11.5.

[0016] In some embodiments, the electrode assembly further comprises tabs, the electrode terminals comprise first and second electrode terminals, the tabs comprise first and second tabs, the first electrode terminal and the first tab are directly electrically connected, and the second electrode terminal and the second tab are directly electrically connected; the polarity of the first tab is opposite to that of the second tab. The first electrode terminal and the first tab are directly electrically connected, and the second electrode terminal and the second tab are directly electrically connected, eliminating the current collecting member between the electrode terminal and the tab, which can reduce the direct current internal resistance (DCR) of the secondary battery cell and improve the safety performance of the battery cell. At the same time, since the current collecting member is omitted, the volume of the secondary battery cell can be reduced, thereby improving the energy density of the secondary battery cell.

[0017] In some embodiments, the ratio of the width of the first tab to the width of the secondary battery cell is 0.5-1.

[0018] In some embodiments, the ratio of the width of the first tab to the width of the secondary battery cell is 0.7-1.

[0019] In some embodiments, the ratio of the width of the second tab to the width of the secondary battery cell is 0.5-1.

[0020] In some embodiments, the ratio of the width of the second tab to the width of the secondary battery cell is 0.7-1.

[0021] The ratio of the width of the first tab and / or the second tab to the width of the secondary battery cell in this range can promote heat dissipation of the secondary battery cell, reduce heat accumulation during use of the secondary battery cell, and further improve the safety performance of the battery cell.

[0022] In some embodiments, the tab includes a first tab and a second tab, the first tab and the second tab have opposite polarities, and the first tab and the second tab have different widths.

[0023] In some embodiments, the first tab is a positive tab, the second tab is a negative tab, the ratio of the width of the positive tab to the width of the secondary battery cell is W1, and the ratio of the width of the negative tab to the width of the secondary battery cell is W2, then W1 > W2.

[0024] In some embodiments, the extension direction of the first tab and the second tab is the same as the length direction of the secondary battery cell, and the first tab and the second tab are respectively arranged at two ends of the body.

[0025] In some embodiments, the number of the first tabs is 1-2.

[0026] In some embodiments, the number of the first tabs is 2, and the two first tabs are arranged at one end of the body. The arrangement of the two first tabs can obtain better flow guiding capacity, and promote the improvement of the electrical performance of the secondary battery.

[0027] In some embodiments, the number of the second tabs is 1-2.

[0028] In some embodiments, the number of the second tabs is 2, and the two second tabs are arranged at one end of the body. The arrangement of the two second tabs can obtain better flow guiding capacity, and promote the improvement of the electrical performance of the secondary battery.

[0029] In some embodiments, the thickness of the first coating layer is 2-5 μm.

[0030] In some embodiments, the thickness of the second coating layer is 2-5 μm.

[0031] The thickness of the first coating layer and / or the second coating layer in the given range can make the coating layer have higher strength, while making the whole isolation film maintain a relatively appropriate thickness, making the electrode assembly of the stack structure maintain a relatively appropriate volume, thereby further improving the battery energy density and storage safety performance.

[0032] In some embodiments, the positive electrode tab includes a positive current collector and a positive active layer arranged on at least one surface of the positive current collector, the positive active layer includes a positive active material, and the positive active material includes a lithium-containing phosphate. The lithium-containing phosphate itself has good safety, which can further improve the safety performance of the secondary battery cell.

[0033] In some embodiments, the positive active layer further includes carbon nanotubes. The carbon nanotubes can improve the conductivity of the positive active layer and improve the electrical performance of the battery cell.

[0034] In some embodiments, the coated weight of the positive electrode active layer is 19 mg / cm 2 - 30 mg / cm 2 The coated weight of the positive electrode active layer in this range can further reduce the heat generation of the battery cell, improving the safety performance of the battery cell.

[0035] In some embodiments, the first coating layer is located between the positive electrode tab and the porous substrate, the second coating layer is located between the negative electrode tab and the porous substrate, and the thickness of the first coating layer is greater than the thickness of the second coating layer.

[0036] In some embodiments, the particulate filler includes one or more of inorganic particles and organic particles. Optionally, the inorganic particles include one or more of boehmite, alumina, barium sulfate, magnesium oxide, magnesium hydroxide, silicon dioxide, tin dioxide, titanium oxide, calcium oxide, zinc oxide, zirconium oxide, yttrium oxide, nickel oxide, cerium oxide, zirconium titanate, barium titanate, magnesium fluoride. Optionally, the organic particles include one or more of phenolic resin, polystyrene, polyethylene, polypropylene, polyimide, cellulose, polyester, polyphenylene sulfide, polyaramide, polyamide-imide, polyimide.

[0037] In some embodiments, the thickness of the porous substrate is less than or equal to 7 μm. The thickness of the porous substrate in this range is beneficial to further improve the volumetric energy density of the secondary battery cell.

[0038] In some embodiments, the thermal shrinkage of the porous substrate in the MD direction at 115℃ / 1h is ≤ 2%. The thermal shrinkage of the porous substrate in the MD direction at 115℃ / 1h in this range is beneficial to further improve the volumetric energy density of the secondary battery cell.

[0039] In some embodiments, the thermal shrinkage of the porous substrate in the TD direction at 115℃ / 1h is ≤ 2%. The thermal shrinkage of the porous substrate in the TD direction at 115℃ / 1h in this range is beneficial to further improve the volumetric energy density of the secondary battery cell.

[0040] In some embodiments, the puncture strength of the porous substrate is 400 gf-600 gf.

[0041] The second aspect of the present application provides an electrical device comprising the secondary battery cell of the first aspect of the present application. BRIEF DESCRIPTION OF DRAWINGS

[0042] For a better understanding of the embodiments or examples provided by the present application, one or more of the accompanying drawings are referred to. Additional details or examples used to describe the drawings should not be considered as limiting the scope of any one of the present application, the presently described embodiments or examples, and the presently understood best mode. Moreover, in all the drawings, the same reference numbers are used to denote the same components. In the drawings:

[0043] FIG. 1 is an exploded view of a secondary battery cell according to an embodiment of the present application.

[0044] FIG. 2 is a schematic view of an electrode assembly of a secondary battery cell according to an embodiment of the present application.

[0045] FIG. 3 is a schematic view of an electrode assembly of a secondary battery cell according to another embodiment of the present application.

[0046] FIG. 4 is a schematic view of a battery pack according to an embodiment of the present application.

[0047] FIG. 5 is an exploded view of the battery pack of FIG. 4.

[0048] FIG. 6 is a schematic view of an electric device according to an embodiment of the present application.

[0049] Reference signs in the drawings: 1, battery pack; 2, upper case; 3, lower case; 4, battery module; 5, secondary battery cell; 51, case; 52, electrode assembly; 521, body; 522, first tab; 523, second tab; 53, end cap; 54, first electrode terminal; 55, second electrode terminal; 6, electric device. DETAILED DESCRIPTION

[0050] For the purpose of facilitating the understanding of the present application, the present application will be described more fully below with reference to the accompanying drawings. The preferred embodiments of the present application are given in the accompanying drawings. However, the present application can be realized in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that the disclosure of the present application can be more thoroughly and completely understood.

[0051] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present application belongs. The terminology used in the description of the present application herein only for the purpose of describing the specific embodiments and is not intended to limit the present application. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0052] The "range" disclosed in this application can be defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints; any endpoint can be independently included or excluded, and they can be combined arbitrarily, meaning any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​1 and 2 are listed, and maximum range values ​​3, 4, and 5 are also listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0" and "5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when describing a parameter as an integer ≥ 2, it is equivalent to listing integers such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, and 12 for that parameter. For instance, when describing a parameter as an integer selected from "2-10", it is equivalent to listing the integers 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0053] In this application, the terms "multiple" or "various" are used unless otherwise specified, referring to a quantity greater than or equal to 2. For example, "one or more" means one or more types.

[0054] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0055] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment or implementation of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments. The term "implementation" as used herein has a similar understanding.

[0056] Those skilled in the art can understand that the sequence of writing each step in the method of each embodiment or example does not mean a strict execution sequence and constitutes any limitation on the implementation process. The detailed execution sequence of each step should be determined by its function and possible internal logic. If not specifically stated, all steps of the present application can be performed sequentially or randomly. For example, the method includes steps (a) and (b), which means that the method can include steps (a) and (b) performed sequentially, or steps (b) and (a) performed sequentially. For example, it is mentioned that the method can further include step (c), which means that step (c) can be added to the method in any order, for example, the method can include steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), etc.

[0057] In the present application, the open technical features or technical solutions described with the words "containing", "including", "comprising" and the like do not exclude additional members other than the listed members, and can be regarded as providing both a closed feature or solution composed of the listed members and an open feature or solution including additional members in addition to the listed members. For example, A includes a1, a2 and a3, and unless otherwise specified, it can also include other members or can not include additional members, and can be regarded as providing both the feature or solution that "A is composed of a1, a2 and a3" and the feature or solution that "A includes a1, a2 and a3, and also includes other members".

[0058] In the present application, "A, such as B" means that B is a non-limiting example of A, and A can be understood as not limited to B.

[0059] In the present application, "optionally", "optional" and "optional" mean that it can or can not be present, i.e. it can be selected from either of the two parallel solutions "yes" or "no". If there are multiple "optional" in a technical solution, unless otherwise specified, and there is no contradiction or mutual restriction, each "optional" is independent.

[0060] In the present application, unless otherwise specified, "secondary battery cell" refers to a basic unit capable of realizing the mutual conversion of chemical energy and electrical energy. Further, it generally includes at least a positive electrode sheet, a negative electrode sheet and an electrolyte. In the battery charging and discharging process, active ions are embedded and extracted between the positive electrode sheet and the negative electrode sheet. The electrolyte plays a role in conducting active ions between the positive electrode sheet and the negative electrode sheet.

[0061] As shown in FIG. 1, an embodiment of the present application provides a secondary battery cell 5. The secondary battery cell 5 includes a shell 51 having an opening. An end cover 53 is used to cover the opening. An electrode terminal is arranged on the end cover 53. An electrode assembly 52 is accommodated in the shell 51. The electrode assembly 52 includes a body 521 including a positive electrode tab, a negative electrode tab, and a separator film, and the electrode assembly 52 is a jelly-roll structure. The separator film includes a porous substrate, a first coating layer, and a second coating layer, the first coating layer and the second coating layer are respectively arranged on two opposite surfaces of the porous substrate, and the first coating layer and the second coating layer both include a particulate filler. The thickness of the first coating layer is denoted as T1, and the thickness of the second coating layer is denoted as T2, then T1+T2≥5 microns (μm). The length of the secondary battery cell 5 is 500 millimeters (mm)-1200 mm.

[0062] In the secondary battery cell 5 of the embodiment, the size of the secondary battery cell 5 is large, and the amount of active material can be increased to improve the energy density of the battery. At the same time, the jelly-roll structure is adopted, and the jelly-roll structure can make the internal space of the battery shell 51 have a high utilization rate, which is beneficial to further improve the energy density of the battery. However, the electrode assembly 52 of the jelly-roll structure needs to be die-cut on four sides during the preparation process, which greatly increases the probability of burr generation at the edge of the electrode tab. During the cycle process of the secondary battery cell 5, the electrode tab expands, which may cause the burr to pierce the separator film, resulting in the overlap of the positive electrode and the negative electrode, and an internal short circuit, causing the battery voltage drop, and ultimately affecting the storage safety performance of the secondary battery. When the thickness of the coating layer of the separator film is controlled within a certain range, the strength of the separator film can increase the resistance to burrs, and the voltage drop of the battery is reduced, thereby effectively improving the storage safety performance of the secondary battery cell 5. Therefore, the secondary battery cell 5 is designed in a specific manner, so that the secondary battery cell 5 has a high energy density and good storage safety performance.

[0063] It can be understood that the shell 51 can be the outer shell of the secondary battery cell 5, and is used to accommodate the electrode assembly 52. The shell 51 can be a hollow cuboid or other hollow three-dimensional structure, and the electrode assembly 52 is accommodated in the accommodation cavity of the hollow three-dimensional structure. The material of the shell 51 can be a conductive material such as copper, iron, aluminum, stainless steel, aluminum alloy, or an insulating material such as plastic or rubber. Optionally, the shell 51 is a hard shell. Further optionally, the hard shell includes an aluminum shell. The aluminum shell has good heat dissipation performance, which can promote the improvement of the heat dissipation performance of the battery cell.

[0064] The opening can be provided on one or more faces of the shell 51. After the shape of the shell 51 is determined, the shape of the opening is also determined accordingly. For example, if the shell 51 is a hollow cuboid structure, the opening is rectangular. The opening can be one or two. Optionally, when the opening is one, it can be provided on any one face of the hollow cuboid shell 51. When the opening is two, it can be provided on two opposite sides of the hollow cuboid shell 51. When the number of openings is more, it depends on the actual situation.

[0065] The end cover 53 is used to cover the opening of the shell 51 to form a sealed space for accommodating the electrode assembly 52, and the sealed space can also be used to accommodate an electrolyte, such as an electrolyte solution. The shape of the end cover 53 depends on the shape of the shell 51. For example, if the shell 51 is a cuboid structure, a rectangular end cover 53 can be selected. The end cover 53 is a carrier of the electrode terminal and other components. The end cover 53 can serve as an output pole of the battery monomer, which is a part of the battery monomer connected to other components and outputs the electrical energy of the battery monomer.

[0066] The end cover 53 and other components provided on the end cover 53 can be collectively referred to as an end cover assembly, which can include a pressure relief valve, a liquid injection hole, an insulating piece, etc. The end cover assembly can be one or more.

[0067] The electrode terminal is provided on the end cover 53, and the electrode terminal is an output component for outputting the electrical energy of the battery monomer. The number of electrode terminals can be one or more, and the material can be a conductive material such as copper, iron, aluminum, stainless steel, and aluminum alloy. The electrode terminal conducts the electrical energy generated by the electrode assembly 52 to the electrical device through the electrical connection lug and the electrical device.

[0068] In some embodiments, the electrode assembly further includes a lug.

[0069] In some embodiments, the electrode terminal and the lug are directly electrically connected.

[0070] In some embodiments, as shown in FIG. 1, the opening of the shell 51 is two, and the two openings are provided on the opposite sides of the shell 51. The end cover assembly is two, and the two end cover assemblies cover the two openings of the shell 51, respectively.

[0071] In some embodiments, the end cover assembly can further include a pressure relief mechanism mounted on the end cover 53, which is used to release the pressure inside the battery monomer when the internal pressure or temperature of the battery monomer reaches a threshold value. Of course, if the end cover assembly in the battery monomer is one, the pressure relief mechanism can be mounted on the end cover 53 of the end cover assembly. If the end cover assembly in the battery monomer is two, the pressure relief mechanism can be mounted on the end cover 53 of each end cover assembly, or only on the end cover 53 of one end cover assembly. Exemplarily, the pressure relief mechanism can be a pressure relief valve, a pressure relief sheet, a gas valve, a pressure relief valve, or a safety valve, etc.

[0072] It can be understood that the stack structure can be a Z-shaped stack structure or a sheet layer stack structure. When the stack structure is a Z-shaped stack structure, the isolation film can be arranged in a Z-shaped reciprocating folding structure, and the plurality of positive electrode sheets and the plurality of negative electrode sheets are arranged on opposite surfaces of the isolation film. Alternatively, the positive electrode sheet is arranged in a Z-shaped reciprocating folding structure, and the plurality of isolation films and the plurality of negative electrode sheets are arranged on the positive electrode sheet, so that the isolation film is arranged between each negative electrode sheet and the positive electrode sheet. Alternatively, the negative electrode sheet is arranged in a Z-shaped reciprocating folding structure, and the plurality of isolation films and the plurality of positive electrode sheets are arranged on the negative electrode sheet, so that the isolation film is arranged between each positive electrode sheet and the negative electrode sheet. When the stack structure is a sheet layer structure, a plurality of sheet-shaped positive electrode sheets, a plurality of sheet-shaped isolation films, and a plurality of sheet-shaped negative electrode sheets are arranged correspondingly to obtain a plurality of electrode assemblies 52, each electrode assembly 52 comprising a positive electrode sheet, an isolation film, and a negative electrode sheet, the isolation film being arranged between the positive electrode sheet and the negative electrode sheet, and the plurality of electrode assemblies 52 are stacked to obtain a sheet layer stack electrode assembly 52.

[0073] As some optional examples of the length of the secondary battery cell 5, the length of the secondary battery cell 5 can be 500 mm, 600 mm, 700 mm, 800 mm, 900 mm, 1000 mm, 1100 mm, 1200 mm, and any value within the range formed by any two of the above values. Optionally, the length of the secondary battery cell 5 is 600 mm-1100 mm. The length of the secondary battery cell 5 in this range can effectively improve the energy density of the secondary battery.

[0074] In some embodiments, the width of the secondary battery cell 5 is 120 mm-140 mm. Optionally, the width of the secondary battery cell 5 can be 120 mm, 122 mm, 125 mm, 128 mm, 130 mm, 132 mm, 135 mm, 138 mm, 140 mm, and any value within the range formed by any two of the above values. For example, the width of the secondary battery cell 5 can be 120 mm-130 mm. The width of the secondary battery cell 5 in this range can enable the electrolyte to maintain a good wetting effect on the electrode assembly 52, thereby further improving the cycle performance of the secondary battery cell 5 on the basis of a higher volumetric energy density.

[0075] In some embodiments, the thickness of the secondary battery cell 5 is 13mm-28mm. Alternatively, the thickness of the secondary battery cell 5 can be 13mm, 14mm, 15mm, 16mm, 17mm, 18mm, 19mm, 20mm, 20.5mm, 21mm, 21.5mm, 22mm, 22.5mm, 23mm, 23.5mm, 24mm, 24.5mm, 25mm, 25.5mm, 26mm, 26.5mm, 27mm, 27.5mm, 28mm, and any value within a range defined by any two of the above values. For example, the thickness of the secondary battery cell 5 can be 15mm-28mm, 15mm-26mm, 15mm-25mm, 18mm-28mm, 18mm-26mm, 18mm-25mm, 20mm-28mm, 20mm-26mm, 20mm-25mm.

[0076] In some embodiments, the aspect ratio of the secondary battery cell 5 is 5-12. The aspect ratio of the secondary battery cell 5 within this range can further improve the energy density and cycle performance of the battery. Alternatively, the aspect ratio of the secondary battery cell 5 can be 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.2, 8.4, 9, 9.5, 10, 11, 12, and any value within a range defined by any two of the above values. For example, the aspect ratio of the secondary battery cell 5 can be 5-11, 5-10, 5-9, 6-11, 6-10, 6-9, 7-11, 7-10, 7-9, 7.5-11, 7.5-10, 7.5-9, 8-11, 8-10, 8-9. It is understood that the aspect ratio of the secondary battery cell 5 represents the ratio of the length and the width of the secondary battery cell 5.

[0077] In some embodiments, the width-to-thickness ratio of the secondary battery cell 5 is 3.2-11.5. For example, the width-to-thickness ratio of the secondary battery cell 5 can be 3.2, 3.5, 4, 4.2, 4.4, 5, 6, 7, 8, 9, 10, 11, 11.5, and any value within a range defined by any two of the above values. For example, the width-to-thickness ratio of the secondary battery cell 5 can be 3.2-11.5, 3.2-10, 3.2-8, 3.2-6, 3.2-5, 4-11.5, 4-10, 4-8, 4-6, 4-5. It is understood that the width-to-thickness ratio of the secondary battery cell 5 represents the ratio of the width and the thickness of the secondary battery cell 5.

[0078] When the other designs of the secondary battery cell 5 remain unchanged, for example, when the length of the secondary battery cell 5 is determined, if the secondary battery cell 5 achieves the required energy density, the width and thickness of the secondary battery cell 5 need to be reasonably adjusted. If the width or thickness is designed too small, the design requirement of the energy density cannot be met; if the thickness is designed too large, the heat dissipation performance of the secondary battery cell 5 will be affected; if the width is designed too large, the cycle performance of the secondary battery cell 5 will be affected. Therefore, the width-to-thickness ratio of the secondary battery cell 5 needs to be controlled within a certain range, so that the secondary battery cell 5 can have good heat dissipation performance and cycle performance at the same time.

[0079] In some embodiments, as shown in FIGS. 1-3, the electrode terminal includes a first electrode terminal 54 and a second electrode terminal 55, and the tab includes a first tab 522 and a second tab 523, the first electrode terminal 54 and the first tab 522 are directly electrically connected, and the second electrode terminal 55 and the second tab 523 are directly electrically connected; the polarity of the first tab 522 is opposite to that of the second tab 523. The first electrode terminal 54 and the first tab 522 are directly electrically connected, and the second electrode terminal 55 and the second tab 523 are directly electrically connected, which cancels the current collecting member between the electrode terminal and the tab, and can further reduce the direct current resistance (DCR for short) of the secondary battery cell 5. At the same time, since the current collecting member is omitted in the secondary battery cell 5, the volume of the secondary battery cell 5 can be reduced, and thus the energy density of the secondary battery cell 5 can be improved.

[0080] In some embodiments, the ratio of the width of the first tab 522 to the width of the secondary battery cell 5 is 0.5-1. The ratio of the width of the first tab 522 to the width of the secondary battery cell 5 within this range can promote the heat dissipation of the secondary battery cell 5, reduce the heat accumulation of the secondary battery cell 5 during use, and further improve the safety performance of the secondary battery cell 5. Alternatively, the ratio of the width of the first tab 522 to the width of the secondary battery cell 5 can be 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 1, and any value within the range formed by any two of the above values. For example, the ratio of the width of the first tab 522 to the width of the secondary battery cell 5 can be 0.7-1.

[0081] In some embodiments, the ratio of the width of the second tab 523 to the width of the secondary battery cell 5 is 0.5-1. The ratio of the width of the second tab 523 to the width of the secondary battery cell 5 in this range can facilitate heat dissipation of the secondary battery cell 5, reduce heat accumulation during use of the secondary battery cell 5, and further improve the safety performance of the secondary battery cell 5. Alternatively, the ratio of the width of the second tab 523 to the width of the secondary battery cell 5 can be 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 1, and any value in the range formed by any two of the above values. For example, the ratio of the width of the second tab 523 to the width of the secondary battery cell 5 can be 0.7-1.

[0082] In some embodiments, the widths of the first tab 522 and the second tab 523 are different.

[0083] In some embodiments, the first tab 522 is a positive electrode tab, and the second tab 523 is a negative electrode tab. The ratio of the width of the positive electrode tab to the width of the secondary battery cell 5 is denoted as W1, and the ratio of the width of the negative electrode tab to the width of the secondary battery cell 5 is denoted as W2. Then W1>W2. When W1>W2, the temperature rise of the battery can be effectively reduced, thereby further improving the safety performance of the secondary battery.

[0084] In some embodiments, as shown in FIGS. 2 and 3, the extension directions of the first tab 522 and the second tab 523 are the same as the length direction of the secondary battery cell 5, and the first tab 522 and the second tab 523 are respectively arranged at both ends of the body 521.

[0085] In some embodiments, the first tab 522 is directly electrically connected to the first electrode terminal 54, and the second tab 523 is directly electrically connected to the second electrode terminal 55. Alternatively, the first tab 522 is directly welded to the first electrode terminal 54, and the second tab 523 is directly welded to the second electrode terminal 55.

[0086] In some embodiments, the number of the first tabs 522 is 1-2.

[0087] In some embodiments, as shown in FIG. 2, the number of the first tabs 522 is 1.

[0088] In some embodiments, as shown in FIG. 3, the number of the first tabs 522 is 2, and the two first tabs 522 are arranged at one end of the body 521. The arrangement of the two first tabs 522 can obtain better flow guiding capacity, and facilitate improvement of the electrical performance of the secondary battery cell 5.

[0089] In some embodiments, the number of the second tabs 523 is 1-2.

[0090] In some embodiments, as shown in FIG. 2, the number of the second tabs 523 is 1.

[0091] In some embodiments, as shown in FIG. 3, the number of the second tabs 523 is 2, and the two second tabs 523 are arranged at one end of the body 521. The arrangement of the two second tabs 523 can obtain better flow guiding capacity, and promote the improvement of the electrical performance of the secondary battery cell 5.

[0092] It can be understood that, in order to ensure that no fusing occurs when passing a large current, the first tab 522 and / or the second tab 523 are usually arranged in multiple layers. The number of the first tab 522 or the second tab 523 refers to the number of the first tab 522 or the second tab 523 formed after the arrangement in multiple layers.

[0093]

Positive electrode tab

[0094] The positive electrode tab includes a positive electrode current collector and a positive electrode active layer arranged on at least one surface of the positive electrode current collector, and the positive electrode active layer includes a positive electrode active material, and the positive electrode active material includes a lithium-containing phosphate. The lithium-containing phosphate itself has good safety, and can further improve the safety performance of the secondary battery cell 5. Optionally, the lithium-containing phosphate includes one or more of lithium iron phosphate, a composite material of lithium iron phosphate and carbon, lithium manganese iron phosphate, and a composite material of lithium manganese iron phosphate and carbon, and these lithium-containing phosphates have a small amount of gas generation, which can further improve the safety performance of the secondary battery cell 5.

[0095] As a non-limiting example, the positive electrode current collector has two opposite surfaces in the thickness direction thereof, and the positive electrode active layer is arranged on any one or both of the two opposite surfaces of the positive electrode current collector.

[0096] In some embodiments, the positive electrode active layer further includes carbon nanotubes. The carbon nanotubes can improve the electrical conductivity of the positive electrode active layer and improve the electrical performance of the battery cell.

[0097] In some embodiments, in addition to the carbon nanotubes, the positive electrode active layer can further include other publicly known conductive agents in the art. As a non-limiting example, the other publicly known conductive agents in the art can include one or more of superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, graphene, and carbon nanofibers.

[0098] In some embodiments, the coating weight of the positive electrode active layer is 19 milligrams per square centimeter (abbreviated as: mg / cm 2 - 30 mg / cm 2 The coating weight of the positive electrode active layer in this range can further reduce the heat generation of the battery cell and improve the safety performance of the battery cell. Optionally, the coating weight of the positive electrode active layer can be 19 mg / cm2 20 mg / cm 2 21 mg / cm 2 22 mg / cm 2 23 mg / cm 2 24 mg / cm 2 25 mg / cm 2 26 mg / cm 2 27 mg / cm 2 28 g / cm 2 29 mg / cm 2 30 mg / cm 2 and any value within a range defined by any two of the above values.

[0099] The coating weight of the positive electrode active layer can be measured using instruments and methods known in the art. For example, a positive electrode tab after cold pressing is punched into a small disc with an area of S1, weighed, and recorded as M1. Then the positive electrode active layer of the weighed positive electrode tab is wiped off, the weight of the positive electrode current collector is weighed, and recorded as M0, and the coating weight of the positive electrode active layer = (M1-M0) / S1.

[0100] In some embodiments, the positive electrode current collector can employ a metal foil or a composite current collector. For example, as a metal foil, an aluminum foil can be employed. The composite current collector can include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector can be obtained by forming a metal material on a polymer material base material. In the positive electrode current collector, non-limiting examples of the metal material can include one or more of aluminum, an aluminum alloy, nickel, a nickel alloy, titanium, a titanium alloy, silver, a silver alloy, and the like. In the positive electrode current collector, non-limiting examples of the polymer material base material can include one or more of a polypropylene (PP), a polyethylene terephthalate (PET), a polybutylene terephthalate (PBT), a polystyrene (PS), a polyethylene (PE), and the like.

[0101] In some embodiments, the positive electrode active material can include other positive electrode active materials known in the art in addition to lithium-containing phosphates. As non-limiting examples, the known positive electrode active materials include lithium transition metal oxides. Examples of the lithium transition metal oxides can include, but are not limited to, one or more of lithium cobalt oxides, lithium nickel oxides, lithium manganese oxides, lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, lithium nickel cobalt manganese oxides, lithium nickel cobalt aluminum oxides, modified compounds thereof, and the like. Non-limiting examples of the lithium cobalt oxides can include LiCoO2; non-limiting examples of the lithium nickel oxides can include LiNiO2; non-limiting examples of the lithium manganese oxides can include LiMnO2, LiMn2O4, and the like; non-limiting examples of the lithium nickel cobalt manganese oxides can include LiNi1 / 3Co1 / 3Mn1 / 3O2, LiNi0.5Co0.2Mn0.3O2, LiNi0.5Co0.3Mn0.2O2, and the like; and non-limiting examples of the lithium nickel cobalt aluminum oxides can include LiNi0.8Co0.15Al0.05O2, LiNi0.8Co0.1Al0.1O2, and the like. 1 / 3Co 1 / 3 Mn 1 / 3 O2 (abbreviated as: NCM) 333 LiNi 0.5 Co 0.2 Mn 0.3 O2 (abbreviated as: NCM) 523 LiNi 0.5 Co 0.25 Mn 0.25 O2 (abbreviated as: NCM) 211 LiNi 0.6 Co 0.2 Mn 0.2 O2 (abbreviated as: NCM) 622 LiNi 0.8 Co 0.1 Mn 0.1 O2 (abbreviated as: NCM) 811 Examples of lithium nickel cobalt aluminum oxides include LiNi, etc. 0.8 Co 0.15 Al 0.05 O2.

[0102] In some embodiments, the positive electrode active layer may optionally include a binder. As a non-limiting example, the binder may include one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resins.

[0103] In some embodiments, the positive electrode sheet can be prepared by dispersing the components used to prepare the positive electrode sheet, such as the positive electrode active material, conductive agent, binder, and any other components, in a solvent to form a positive electrode slurry; coating the positive electrode slurry onto at least one surface of the positive electrode current collector, and then obtaining the positive electrode sheet after drying, cold pressing, and other processes. The solvent can be selected from, but is not limited to, any of the solvents described in the foregoing embodiments, such as N-methylpyrrolidone (NMP). The surface of the positive electrode current collector coated with the positive electrode slurry can be a single surface of the positive electrode current collector or both surfaces of the positive electrode current collector.

[0104] [Negative electrode plate]

[0105] The negative electrode sheet includes a negative current collector and a negative active layer disposed on at least one surface of the negative current collector, the negative active layer including a negative active material.

[0106] As a non-limiting example, the negative current collector has two surfaces opposite in the thickness direction thereof, and the negative active layer is disposed on either one or both of the two opposite surfaces of the negative current collector.

[0107] In some embodiments, the negative current collector can employ a metal foil or a composite current collector. For example, as the metal foil, a copper foil can be employed. The composite current collector can include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector can be obtained by forming a metal material on a polymer material base layer. Non-limiting examples of the metal material in the negative current collector can include one or more of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, silver alloy, and the like. Non-limiting examples of the polymer material base layer in the negative current collector can include one or more of a polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), and the like.

[0108] In some embodiments, the negative active material can employ a negative active material for a battery known in the art. As a non-limiting example, the negative active material can include one or more of artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based material, tin-based material, lithium titanate, and the like. The silicon-based material can include one or more of elemental silicon, silicon oxide compound, silicon-carbon composite, silicon-nitrogen composite, and silicon alloy. The tin-based material can include one or more of elemental tin, tin oxide compound, and tin alloy. However, the present application is not limited to these materials, and other conventional materials that can be used as a negative active material for a battery can also be used. These negative active materials can be used alone or in combination of two or more.

[0109] In some embodiments, the negative active layer can further optionally include a binder. The binder can include one or more of styrene butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0110] In some embodiments, the negative active layer can further optionally include a conductive agent. The conductive agent can include one or more of super conductive carbon, acetylene black, carbon black, ketjen black, carbon dot, carbon nanotube, graphene, and carbon nanofiber.

[0111] In some embodiments, the negative active layer can further optionally include other auxiliary agents, such as a thickening agent. Optionally, the thickening agent includes sodium carboxymethyl cellulose (CMC-Na) and the like.

[0112] In some embodiments, the negative electrode sheet can be prepared by dispersing the above-mentioned components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder, and any other components, in a solvent, for example, deionized water, to form a negative electrode slurry; coating the negative electrode slurry on at least one side surface of the negative electrode current collector; and drying, cold-pressing, or the like, to obtain the negative electrode sheet. The surface of the negative electrode current collector coated with the negative electrode slurry can be a single surface of the negative electrode current collector or both surfaces of the negative electrode current collector.

[0113]

Separator

[0114] The separator of the present application comprises a porous substrate, a first coating layer, and a second coating layer, the first coating layer and the second coating layer being respectively located on the two opposite surfaces of the porous substrate. Both the first coating layer and the second coating layer comprise a particulate filler. The thickness of the first coating layer is denoted as T1, and the thickness of the second coating layer is denoted as T2, then T1+T2≥5μm.

[0115] T1+T2 can be any value within the above range. For example, T1+T2 can be 5μm, 5.5μm, 6μm, 6.5μm, 7μm, 7.5μm, 8μm, 8.5μm, 9μm. In some embodiments, 5μm≤T1+T2≤9μm.

[0116] It can be understood that, under the condition that other conditions remain unchanged, the greater the total thickness of the coating layer of the separator, the smaller the volumetric energy density of the battery. Therefore, in order to make the secondary battery cell 5 maintain a relatively high energy density and a relatively good storage safety performance at the same time, the total thickness of the coating layer is optionally 8μm or less. For example, 5μm≤T1+T2≤8μm, 6μm≤T1+T2≤8μm.

[0117] In some embodiments, the thickness of the first coating layer is 2μm-5μm. Optionally, the thickness of the first coating layer can be 2μm, 2.5μm, 3μm, 3.5μm, 4μm, 4.5μm, 5μm, and any value within the range constituted by any two of the above values.

[0118] In some embodiments, the thickness of the second coating layer is 2μm-5μm. Optionally, the thickness of the second coating layer can be 2μm, 2.5μm, 3μm, 3.5μm, 4μm, 4.5μm, 5μm, and any value within the range constituted by any two of the above values.

[0119] The thickness of the first coating layer and / or the second coating layer within the range can make the first coating layer and / or the second coating layer have a relatively high strength, while making the whole separator maintain a relatively appropriate thickness, and thus making the electrode assembly 52 of the stack structure maintain a relatively appropriate volume, which is conducive to making the secondary battery cell 5 maintain a relatively high energy density.

[0120] In some embodiments, the first coating layer is located between the positive electrode tab and the porous substrate, the second coating layer is located between the negative electrode tab and the porous substrate, and the thickness of the first coating layer is greater than the thickness of the second coating layer. In the secondary battery cell 5, the potential at the positive electrode tab is higher, and the surface of the separator film facing the positive electrode tab is prone to be oxidized, which reduces the strength of the separator film and further increases the risk of the separator film being punctured. In these embodiments, the thickness of the first coating layer is greater than the thickness of the second coating layer, which can better protect the surface of the separator film facing the positive electrode tab, maintain a higher strength of the separator film, reduce the risk of the separator film being punctured, and further improve the storage safety performance of the secondary battery.

[0121] In some embodiments, the particulate filler includes one or more of inorganic particles or organic particles.

[0122] In some embodiments, the inorganic particles include one or more of boehmite (abbreviation: γ-AlOOH), aluminum oxide (abbreviation: Al2O3), barium sulfate (abbreviation: BaSO4), magnesium oxide (abbreviation: MgO), magnesium hydroxide (abbreviation: Mg(OH)2), silicon dioxide (abbreviation: SiO2), tin dioxide (abbreviation: SnO2), titanium oxide (abbreviation: TiO2), calcium oxide (abbreviation: CaO), zinc oxide (abbreviation: ZnO), zirconium oxide (abbreviation: ZrO2), yttrium oxide (abbreviation: Y2O3), nickel oxide (abbreviation: NiO), cerium oxide (abbreviation: CeO2), zirconium titanate (abbreviation: SrTiO3), barium titanate (abbreviation: BaTiO3), magnesium fluoride (abbreviation: MgF2).

[0123] In some embodiments, the organic particles include one or more of phenol formaldehyde resin, polystyrene, polyethylene, polypropylene, polyimide, cellulose, polyester, polyphenylene sulfide, polyaramid, polyamide-imide, polyimide.

[0124] In some embodiments, the first coating layer and / or the second coating layer further includes a binder for fixing the particulate filler. Optionally, the binder includes one or more of a homopolymer or copolymer of acrylic monomer units, a homopolymer or copolymer of acrylate monomer units, a homopolymer or copolymer of fluorine-containing vinyl monomer units, a homopolymer or copolymer of unsaturated nitrile monomer units, polyvinylpyrrolidone.

[0125] In some embodiments, the thickness of the porous substrate is less than or equal to 7 pm. The thickness of the porous substrate in this range is advantageous for further improving the volumetric energy density of the secondary battery cell 5. Optionally, the thickness of the porous substrate can be 2 pm, 3 pm, 4 pm, 5 pm, 6 pm, 7 pm, and any value within the range consisting of any two of the aforementioned values. For example, the thickness of the porous substrate can be 3 pm to 7 pm, 4 pm to 7 pm, 5 pm to 7 pm.

[0126] In some embodiments, the thermal shrinkage of the porous substrate in the MD direction at 115 degrees Celsius per 1 hour (abbreviated as: °C / 1h) is less than or equal to 2%. The thermal shrinkage of the porous substrate in the MD direction at 115 °C / 1h in this range is advantageous for further improving the volumetric energy density of the secondary battery cell 5. It can be understood that the MD direction represents the longitudinal stretching direction of the porous substrate. Optionally, the thermal shrinkage of the porous substrate in the MD direction at 115 °C / 1h can be 0.2%, 0.5%, 0.8%, 1%, 1.5%, 2%, and any value within the range consisting of any two of the aforementioned values, for example, the thermal shrinkage of the porous substrate in the MD direction at 115 °C / 1h can be 0.2% to 2%.

[0127] In some embodiments, the thermal shrinkage of the porous substrate in the TD direction at 115 °C / 1h is less than or equal to 2%. The thermal shrinkage of the porous substrate in the TD direction at 115 °C / 1h in this range is advantageous for further improving the volumetric energy density of the secondary battery cell 5. It can be understood that the TD direction represents the transverse stretching direction of the porous substrate. Optionally, the thermal shrinkage of the porous substrate in the TD direction at 115 °C / 1h can be 0.2%, 0.5%, 0.8%, 1%, 1.5%, 2%, and any value within the range consisting of any two of the aforementioned values, for example, the thermal shrinkage of the porous substrate in the TD direction at 115 °C / 1h can be 0.2% to 2%.

[0128] The thermal shrinkage of the porous substrate in the MD direction and the TD direction at 115 °C / 1 h in the present application can be measured by the following test method: the porous substrate is punched into a sample with a width of 50 mm and a length of 100 mm by a punch machine, 5 parallel samples are placed on an A4 paper, and then the A4 paper with the samples is placed on a corrugated paper with a thickness of 1 mm to 5 mm. The temperature of the air oven is set to 115 °C, and after the temperature reaches the set temperature and stabilizes for 60 minutes (referred to as: min), the A4 paper placed on the corrugated paper is placed in the air oven, and the timing starts. After reaching the set time of 1 h in the present application, the length and width of the porous substrate are measured, and the values are marked as a and b, respectively. The thermal shrinkage is calculated: the longitudinal (referred to as: MD) thermal shrinkage = [(100-a) / 100]x100%, and the transverse (referred to as: TD) thermal shrinkage = [(50-b) / 50]x100%. The average value of 5 parallel samples is taken as the test result.

[0129] In some embodiments, the puncture strength of the porous substrate is 400 grams force (referred to as: gf)-600 gf. Alternatively, the puncture strength of the porous substrate can be 400 gf, 450 gf, 500 gf, 550 gf, 600 gf, and any value within the range formed by any two of the above values.

[0130] The puncture strength of the porous substrate can be measured by the following test method: the porous substrate is cut into a strip, and the width must be greater than 10 centimeters (referred to as: cm); the strip-shaped porous substrate is placed in a specially designed clamp, and the flatness of the porous substrate is ensured during placement. The clamp is ventilated to clamp the porous substrate; turn on the universal testing machine, and set the needle moving rate to 50 millimeters per minute (referred to as: mm / min). When the needle penetrates the porous substrate, there will be a reading on the computer screen connected to the universal testing machine. The maximum value is the puncture strength of the porous substrate. Test 3 points and take the average value as the puncture strength of the porous substrate.

[0131]

Electrolyte

[0132] The electrolyte has the function of conducting ions between the positive electrode sheet and the negative electrode sheet. The type of electrolyte is not particularly limited in the present application and can be selected as needed. For example, the electrolyte can be liquid, gel or all-solid.

[0133] In some embodiments, the electrolyte uses an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0134] In some embodiments, the electrolyte salt can include one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bisfluorosulfonylimide (LiFSI), lithium bis-trifluoromethanesulfonylimide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorophosphate (LiPO2F2), lithium difluoro(oxalato)borate (LiDFOB), lithium bis(oxalato)borate (LiBOB), lithium difluoro(oxalato)phosphate (LiDFOP), and lithium tetrafluoro(oxalato)phosphate (LiTFOP).

[0135] In some embodiments, the solvent can include one or more of ethylene carbonate (EC), propylene carbonate (PC), methyl ethyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate, fluoroethylene carbonate (FEC), methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0136] In some embodiments, the electrolyte solution can also optionally include an additive. For example, the additive can include a negative electrode film-forming additive, a positive electrode film-forming additive, and can also include an additive capable of improving certain properties of the battery, such as an additive for improving overcharge performance of the battery, an additive for improving high-temperature or low-temperature performance of the battery, etc.

[0137] In some embodiments, the additive in the electrolyte solution can include, but is not limited to, one or more of fluoroethylene carbonate (FEC), difluoroethylene carbonate (DFEC), trifluoromethyl ethylene carbonate (TFPC), etc.

[0138] The application also provides a secondary battery in one embodiment. The secondary battery includes the secondary battery cell 5 of the application.

[0139] In some embodiments, the secondary battery can be a battery module; when there are multiple secondary battery cells, the multiple battery cells are arranged and fixed to form a battery module.

[0140] In some embodiments, the secondary battery can be a battery pack, and the battery pack includes a box and a secondary battery cell, and the battery cell or the battery module is accommodated in the box.

[0141] FIGS. 4 and 5 are a battery pack 1 as an example. Referring to FIGS. 4 and 5, the battery pack 1 can include a battery case and a plurality of battery modules 4 disposed in the battery case. The battery case includes an upper case 2 and a lower case 3, and the upper case 2 is capable of being provided on the lower case 3 and forms an enclosed space for accommodating the battery modules 4. The plurality of battery modules 4 can be arranged in the battery case in any manner.

[0142] The application also provides a power consuming device including the secondary battery cell provided by the application. The secondary battery cell can be used as a power source of the power consuming device, or can be used as an energy storage unit of the power consuming device. The power consuming device can include a mobile device, an electric vehicle, an electric train, a ship and a satellite, an energy storage system, etc., but is not limited thereto. Among them, the mobile device can be a mobile phone, a notebook computer, etc.; the electric vehicle can be a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc., but is not limited thereto.

[0143] As the power consuming device, the battery can be selected according to the use requirement thereof.

[0144] As another example of the device, it can be a mobile phone, a tablet computer, a notebook computer, etc. The device usually requires thinning, and a battery can be used as a power source.

[0145] In some embodiments, as shown in FIG. 6, the battery pack 1 can be part of the chassis structure of the electric vehicle as the power consuming device. For example, part of the case can become at least part of the floor of the vehicle, or part of the case can become at least part of the cross beam and the longitudinal beam of the vehicle.

[0146] In order to make the technical problems, technical solutions and beneficial effects solved by the application clearer, the application will be further described in detail below in combination with embodiments and drawings. Obviously, the described embodiments are only a part of the embodiments of the application, rather than all the embodiments. The following description of at least one exemplary embodiment is merely illustrative in nature and in no way limits the application and its applications. Based on the embodiments in the application, all other embodiments obtained by those of ordinary skill in the art without creative labor fall within the scope of protection of the application.

[0147] Unless otherwise specified in the embodiments, the technology or conditions are carried out according to the technology or conditions described in the literature in the art or according to the product manual. Unless otherwise specified, the reagents or instruments used are conventional products that can be obtained from the market.

[0148] Embodiment 1

[0149] (1) Preparation of positive electrode sheet

[0150] The positive active material lithium iron phosphate LiFePO4, the conductive agent carbon nanotube, and the binder polyvinylidene fluoride are mixed in a weight ratio of 96.4:1.5:2.1, and then dissolved in a solvent N-methyl pyrrolidone NMP to prepare a positive electrode slurry. Then, the positive electrode slurry is coated on a current collector aluminum foil, and after drying, cold pressing, edge cutting, piece cutting, and striping, a positive electrode sheet is obtained.

[0151] (2) Preparation of a negative electrode sheet

[0152] The negative active material artificial graphite, the conductive agent carbon black, the thickening agent CMC, and the binder SBR are mixed in a weight ratio of 96.2:0.5:1.2:2.1, and then dissolved in a solvent deionized water to prepare a negative electrode slurry. Then, the negative electrode slurry is coated on a current collector copper foil, and after drying, cold pressing, tab forming, and striping, a negative electrode sheet is obtained.

[0153] (3) Preparation of an electrolyte

[0154] In an argon atmosphere glove box with a water content of <10 ppm, ethylene carbonate EC and methyl ethyl carbonate EMC are mixed in a volume ratio of 3:7, and then lithium hexafluorophosphate LiPF6 is uniformly dissolved in the solvent. Then, an additive VC is added to obtain an electrolyte. The molar concentration of LiPF6 in the electrolyte is 1 mol / L (abbreviation: mol / L). The mass percentage of VC in the electrolyte is 3%.

[0155] (4) Isolation film

[0156] ① A PE porous substrate with a thickness of 7 μm is provided;

[0157] ② A coating slurry is prepared: inorganic particles aluminum oxide Al2O3, polymethacrylate binder, dispersant sodium carboxymethyl cellulose CMC-Na, and wetting agent silicone modified polyether are mixed in a mass ratio of 93%:6%:0.5%:0.5% in an appropriate amount of solvent deionized water to obtain a coating slurry.

[0158] ③ The coating slurry prepared in step ② is coated on the opposite two surfaces of the PE porous substrate by a coating machine to form a first coating and a second coating. Through drying and slitting processes, an isolation film is obtained. The thickness of the first coating T1 is 2.5 μm, the thickness of the second coating T2 is 2.5 μm, and T1+T2=5 μm.

[0159] (5) Preparation of a battery cell

[0160] The positive electrode sheet, the separator, and the negative electrode sheet are stacked in order, and the separator is arranged between the positive electrode sheet and the negative electrode sheet to play a role of isolation, to obtain an electrode assembly with a laminated structure; the electrode assembly is placed in a square aluminum shell, and the positive electrode tab and the positive terminal on the shell end cover are welded, so that the positive electrode tab is directly connected with the positive terminal; the negative electrode tab and the negative terminal on the shell end cover are welded, so that the negative electrode tab is directly connected with the negative terminal; after vacuum drying, electrolyte is injected, and then standing, formation test, aging are carried out, to obtain a secondary battery monomer. The length of the secondary battery monomer is 945 mm, the width is 122 mm, the thickness is 27.5 mm, the length-width ratio is 7.75, and the width-thickness ratio is 4.44; the ratio W1 of the width of the positive electrode tab to the width of the secondary battery monomer is 0.72, and the ratio W2 of the width of the negative electrode tab to the width of the secondary battery monomer is 0.72.

[0161] Examples 2-8 and Comparative Examples 1-2 are substantially the same as Example 1, and the differences are shown in Table 1.

[0162] Test Example

[0163] (1) Volume energy density test method: at 25℃, the secondary battery monomer is discharged at 0.33C to 2.5V; after standing for 5min, it is charged at 0.33C to the upper limit cutoff voltage 3.65V, and then charged at a constant voltage to a current of 0.05C, and the discharge capacity C0 and the discharge energy E0 at this time are recorded. The volume energy density = E0 / monomer volume, the unit of volume is L. The test results are shown in Table 1.

[0164] (2) Storage pressure drop test test method: at 25℃, the secondary battery monomer is charged at 0.33C to the upper limit cutoff voltage 3.65V, and then charged at a constant voltage to a current of 0.05C, and the voltage U0 of the monomer is recorded; the monomer battery is placed in a 60℃ oven, and left for 28 days, and after taking out, it is placed in a 25℃ environment for 24h before testing the voltage U1 of the monomer, then the pressure drop = (U0-U1) / 28 / 24, the pressure drop unit is mV / h. It can be understood that the smaller the storage pressure drop, the better the storage safety of the secondary battery monomer. The test results are shown in Table 1.

[0165] Table 1

[0166] As can be seen from Table 1, compared with Comparative Example 1-2, the battery monomer in Examples 1-8 effectively improves the storage pressure drop of the battery under the premise of having a higher energy density, thereby effectively improving the storage safety of the secondary battery monomer.

[0167] As can be seen from Examples 1-6, as T1+T2 increases, the storage pressure drop of the battery cell decreases. When 6 μm≤T1+T2≤8 μm, the battery cell can better balance the higher volumetric energy density and the better storage safety performance.

[0168] As can be seen from the comparison between Example 3 and Example 4, when T1 is greater than T2, the battery cell has a lower storage pressure drop.

[0169] (3) The overcurrent temperature rise test was performed on the secondary battery cells of Example 4 and Example 8. The test method was as follows: the initial temperature of the secondary battery end cover was recorded, the secondary battery cell was charged at 3C to the upper limit cutoff voltage 3.65V, and the temperature rise change of the end cover at this time was detected.

[0170] Among them, the temperature rise of the battery cell of Example 4 is 27℃, and the temperature rise of the battery cell of Example 8 is 22℃. This shows that when W1>W2, the secondary battery cell has a lower temperature rise, thereby further improving the safety performance of the battery.

[0171] The technical features of the above examples can be combined in any way. In order to make the description simple, all possible combinations of the technical features in the above examples are not described, however, as long as the combination of the technical features does not exist contradictory, it should be considered as the scope of the present application.

[0172] The above examples only express several embodiments of the present application, and the description is more specific and detailed, but it should not be understood as limiting the scope of the patent. It should be pointed out that for ordinary skilled in the art, without departing from the concept of the present application, a number of variations and improvements can be made, which are within the scope of the present application. Therefore, the scope of protection of the patent of the present application should be subject to the appended claims.

Claims

1. A secondary battery cell, comprising: a housing having an opening; an end cap for covering the opening; an electrode terminal provided to the end cap; an electrode assembly accommodated in the housing; the electrode assembly comprises a body including a positive electrode tab, a negative electrode tab, and a separator, and the electrode assembly is a jelly-roll structure; the separator comprises a porous substrate, a first coating layer, and a second coating layer, the first coating layer and the second coating layer are respectively located on two opposite surfaces of the porous substrate, and the first coating layer and the second coating layer each comprise a particulate filler; a thickness of the first coating layer is denoted as T1, a thickness of the second coating layer is denoted as T2, and T1+T2≥5μm; and a length of the secondary battery cell is 500mm-1200mm.

2. The secondary battery cell according to claim 1, wherein 5μm≤T1+T2≤9μm, optionally, 6μm≤T1+T2≤8μm.

3. The secondary battery cell according to claim 1 or 2, wherein The length of the secondary battery cell is 600mm-1100mm.

4. The secondary battery cell according to any one of claims 1 to 3, wherein The width of the secondary battery cell is 120mm-140mm.

5. The secondary battery cell according to any one of claims 1 to 4, wherein The width of the secondary battery cell is 120mm-130mm.

6. The secondary battery cell according to any one of claims 1 to 5, wherein The thickness of the secondary battery cell is 13mm-28mm.

7. The secondary battery cell according to any one of claims 1 to 6, wherein The aspect ratio of the secondary battery cell is 5-12.

8. The secondary battery cell according to any one of claims 1 to 7, wherein The width-thickness ratio of the secondary battery cell is 3.2-11.

5.

9. The secondary battery cell according to any one of claims 1 to 8, wherein The electrode assembly further comprises a tab, the electrode terminal comprises a first electrode terminal and a second electrode terminal, the tab comprises a first tab and a second tab, the first electrode terminal and the first tab are directly electrically connected, the second electrode terminal and the second tab are directly electrically connected; the polarity of the first tab and the second tab is opposite.

10. The secondary battery cell according to any one of claims 1 to 9, wherein The electrode assembly further comprises a tab, the tab comprises a first tab and a second tab, the polarity of the first tab and the second tab is opposite, and the secondary battery cell satisfies at least one of the following (1)-(4): (1) the ratio of the width of the first tab to the width of the secondary battery cell is 0.5-1, optionally 0.7-1; (2) the ratio of the width of the second tab to the width of the secondary battery cell is 0.5-1, optionally 0.7-1; (3) the width of the first tab and the second tab is different; (4) the first tab is a positive electrode tab, the second tab is a negative electrode tab, the ratio of the width of the positive electrode tab to the width of the secondary battery cell is denoted as W1, the ratio of the width of the negative electrode tab to the width of the secondary battery cell is denoted as W2, and W1>W2.

11. The secondary battery cell according to any one of claims 1 to 10, wherein The electrode assembly further comprises a tab, the tab comprises a first tab and a second tab, the polarity of the first tab and the second tab is opposite; the extension direction of the first tab and the second tab is the same as the length direction of the secondary battery cell, and the first tab and the second tab are respectively arranged at two ends of the body.

12. The secondary battery cell according to any one of claims 1 to 11, wherein, The electrode assembly further comprises a tab, the tab comprises a first tab and a second tab, the polarity of the first tab and the second tab is opposite; The number of the first tab is 1-2; optionally, the number of the first tab is 2, and 2 first tabs are arranged at intervals at one end of the body; and / or, The number of the second tab is 1-2; optionally, the number of the second tab is 2, and 2 second tabs are arranged at intervals at one end of the body.

13. The secondary battery cell according to any one of claims 1 to 12, wherein, The thickness of the first coating layer is 2-5 μm; and / or, The thickness of the second coating layer is 2-5 μm.

14. The secondary battery cell according to any one of claims 1 to 13, wherein The positive electrode tab includes a positive electrode current collector and a positive electrode active layer arranged on at least one surface of the positive electrode current collector, the positive electrode active layer including a positive electrode active material, the positive electrode active material including lithium-containing phosphate.

15. The secondary battery cell of claim 14, wherein, The positive electrode active layer further includes carbon nanotubes.

16. The secondary battery cell according to claim 14 or 15, wherein The coating weight of the positive electrode active layer is 19 mg / cm 2 - 30 mg / cm 2 .

17. The secondary battery cell of any one of claims 1-16, wherein, The first coating layer is located between the positive electrode tab and the porous substrate, the second coating layer is located between the negative electrode tab and the porous substrate, and the thickness of the first coating layer is greater than the thickness of the second coating layer.

18. The secondary battery cell of any one of claims 1-17, wherein, The particulate filler includes one or more of inorganic particles or organic particles; Optionally, the inorganic particles include one or more of boehmite, alumina, barium sulfate, magnesium oxide, magnesium hydroxide, silicon dioxide, tin dioxide, titanium oxide, calcium oxide, zinc oxide, zirconium oxide, yttrium oxide, nickel oxide, cerium oxide, zirconium titanate, barium titanate, magnesium fluoride; Optionally, the organic particles include one or more of phenol formaldehyde resin, polystyrene, polyethylene, polypropylene, polyimide, cellulose, polyester, polyphenylene sulfide, polyaramide, polyamide-imide, polyimide.

19. The secondary battery cell of any one of claims 1-18, wherein, The porous substrate satisfies at least one of the following (1)-(4): (1) The thickness of the porous substrate is less than or equal to 7 μm; (2) The thermal shrinkage of the porous substrate in the MD direction at 115℃ / 1h is ≤2%; (3) The thermal shrinkage of the porous substrate in the TD direction at 115℃ / 1h is ≤2%; (4) The puncture strength of the porous substrate is 400-600 gf.

20. An electrical device comprising the secondary battery cell of any one of claims 1-19.

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