Battery cell and secondary battery

Abstract

The utility model provides a battery cell and a secondary battery. The battery cell comprises a cover plate assembly, a first electrode and a second electrode, the shell is matched with the cover plate assembly to form an accommodating space; the at least one electrode assembly is arranged in the accommodating space, and the electrode assembly comprises a straight section and a bent section along the length direction of the electrode assembly; the multiple supporting structures are located in the containing space and arranged at the two ends of the electrode assembly in the length direction of the electrode assembly, and each supporting structure abuts against the bent section and the shell; in the length direction, the distance between the sides, away from the electrode assembly, of the two adjacent supporting structures is a first distance, and the first distance is equal to the length of the electrode assembly. The battery cell and the secondary battery provided by the utility model are simple in structure and convenient to manufacture, local lithium precipitation of the battery cell can be effectively avoided, the service life is prolonged, and meanwhile, the energy density of the battery cell is ensured.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of batteries, in particular to a battery cell and a secondary battery. BACKGROUND

[0002] With the continuous development of new energy industry, higher requirements are put forward for battery cells. Battery cells are mainly divided into square shell, cylindrical and soft package battery cells according to the shell structure, and the internal electrode assembly arrangement mode is divided into winding and laminating two forms. Under the requirements of production efficiency and safety performance, square shell winding battery cell becomes the mainstream form of existing energy storage system. Usually, a support structure is arranged inside the battery cell to support the corner of the battery cell to avoid local lithium precipitation. However, the existing support structure reduces the energy density of the battery cell. Therefore, there is an urgent need for a battery cell with high energy density and avoiding local lithium precipitation. CONTENT OF THE UTILITY MODEL

[0003] Therefore, the purpose of the present application is to provide a battery cell and a secondary battery to solve the problems mentioned in the background art.

[0004] In a first aspect, the present application provides a battery cell, comprising: a cover plate assembly; a shell cooperating with the cover plate assembly to form an accommodation space; at least one electrode assembly arranged in the accommodation space, the electrode assembly comprising a flat section and a bent section; a plurality of support structures located in the accommodation space and arranged at both ends of the electrode assembly along the length direction of the electrode assembly, each of the support structures being in abutment with the bent section and the shell respectively; along the length direction, the distance between the two adjacent support structures away from one side of the electrode assembly is a first distance, and the first distance is equal to the length of the electrode assembly.

[0005] A plurality of support structures are arranged in the accommodation space, each of the support structures being in abutment with the bent section and the shell respectively, along the length direction, the distance between the two adjacent support structures away from one side of the electrode assembly is a first distance, and the first distance is equal to the length of the electrode assembly.

[0006] Further, the material of the support structure is porous foam, and the porosity of the support structure is 60% to 90%.

[0007] Further, the height of the support structure is greater than or equal to the height of the electrode assembly.

[0008] Further, the support structure comprises a first support column arranged at the corner of the accommodation space and cooperating with a partial area of one of the bent sections.

[0009] Further, the four corners of the accommodating space are respectively provided with a first supporting column, and the distance between two adjacent first supporting columns away from one side of the electrode assembly in the thickness direction of the electrode assembly is a second distance, and the second distance is equal to the total thickness of the at least one electrode assembly.

[0010] Further, the battery cell comprises a plurality of electrode assemblies arranged in stacks, and the supporting structure further comprises a second supporting column arranged between the bending sections of two adjacent electrode assemblies and matched with the partial areas of the two bending sections.

[0011] Further, the battery cell further comprises an insulating film, and the insulating film wraps the electrode assemblies, and the supporting structure is located between the insulating film and the electrode assemblies.

[0012] Further, the insulating film comprises a first insulating layer located on the side surface of the electrode assembly, and the supporting structure is fixed on the first insulating layer.

[0013] Further, the insulating film further comprises a second insulating layer located on the bottom of the electrode assembly, and the second insulating layer is provided with an infiltration hole.

[0014] In a second aspect, the application provides a secondary battery comprising the battery cell as described in the first aspect.

[0015] As can be seen from the above, the battery cell and the secondary battery provided by the application comprise a cover plate assembly, a shell matched with the cover plate assembly to form an accommodating space, at least one electrode assembly arranged in the accommodating space, the electrode assembly comprising a straight section and a bending section along the length direction of the electrode assembly, and a plurality of supporting structures arranged in the accommodating space and located at both ends of the electrode assembly along the length direction, each supporting structure being matched with the bending section and the shell. The distance between two adjacent supporting structures away from one side of the electrode assembly in the length direction is a first distance, and the first distance is equal to the length of the electrode assembly. By arranging the supporting structures at both ends of the electrode assembly along the length direction, the supporting structures can be matched with the shell and the bending section of the electrode assembly, so that the overall stress of the electrode assembly is uniform, and the local lithium precipitation phenomenon is avoided. By setting the first distance equal to the length of the electrode assembly, the size of the supporting structure is limited, so that the supporting structure is not too long in the length direction, the accommodating space is not occupied too much, and the energy density of the battery cell is reduced. The battery cell and the secondary battery have simple structure and are easy to manufacture, can effectively avoid local lithium precipitation of the battery cell, prolong the service life, and ensure the energy density of the battery cell. BRIEF DESCRIPTION OF DRAWINGS

[0016] To more clearly illustrate the technical solutions in this application or related technologies, the drawings used in the description of the embodiments or related technologies will be briefly introduced below. Obviously, the drawings described below are only embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of the longitudinal cross-sectional structure of a battery cell according to an embodiment of this application;

[0018] Figure 2 for Figure 1 A schematic diagram of the cross-sectional structure of a battery cell;

[0019] Figure 3 This is a schematic diagram of the cross-sectional structure of another type of battery cell in an embodiment of this application;

[0020] Figure 4 for Figure 3 A schematic diagram of the unfolded structure of the insulating film of the battery cell;

[0021] Figure 5 for Figure 4 A schematic diagram of the cross-section of the insulating film;

[0022] Figure 6 This is a diagram of the long-cycle test of the battery cell.

[0023] Reference numerals: 1. Cover plate assembly; 2. Housing; 3. Electrode assembly; 3-1. Straight section; 3-2. Bending section; 4. Support structure; 4-1. First support column; 4-2. Second support column; 5. Insulating film; 5-1. First insulating layer; 5-2. Second insulating layer; 5-3. Impregnation hole. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with specific embodiments and the accompanying drawings.

[0025] It should be noted that, unless otherwise defined, technical terms or scientific terms used in the embodiments of the present application shall have the common meanings understood by those with ordinary skills in the art to which the present application belongs. The terms "first", "second" and similar terms used in the embodiments of the present application do not represent any order, quantity or importance, but are only used to distinguish different components. The terms "comprise", "include" and similar terms mean that the elements or objects before the terms encompass the elements or objects listed after the terms and their equivalents, and do not exclude other elements or objects. The terms "connect" or "connected" and similar terms are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. The terms "upper", "lower", "left", "right" and the like are only used to represent relative positional relationships, and when the absolute positions of the described objects are changed, the relative positional relationships may also be changed accordingly.

[0026] The square shell winding battery cell is the mainstream form of the existing energy storage system, but due to the arc shape of the two ends of the electrode assembly, there is a corner gap inside the battery cell, which makes the stress distribution of the corner of the battery cell inconsistent with the flat area, and also limits the compaction of the electrode sheet and the heat pressing pressure of the battery cell. The volume of the negative electrode graphite material changes during charging and discharging, and there is a certain rebound of the negative electrode sheet under full charging filling. This rebound is prone to cause the electrode sheet to wrinkle during long cycle, thereby worsening the contact between the electrode sheets. The electrode assembly flat area electrode sheet is constrained by the shell, and the degree of wrinkling is lighter, but the corner is not limited by the shell. With repeated expansion and contraction of the electrode sheet, the gap between the positive and negative electrodes becomes larger, the ion impedance increases, the dynamic performance of the battery cell at the corner deteriorates, and the battery cell is prone to lithium precipitation. A support structure can be arranged inside the battery cell to support the corner of the battery cell, avoid local lithium precipitation, for example, a support structure is arranged on each side of the battery cell along the length direction to clamp the winding core. Each support structure is arranged to have an arc surface opposite to the entire arc area of the electrode assembly, so that the overall stress of the battery cell is uniform, and local lithium precipitation is avoided. However, the support structure arranged in this way is too large in size and occupies too much space in the length direction, which reduces the energy density of the battery cell.

[0027] Hereinafter, specific embodiments will be described below with reference to the accompanying drawings. Figures 1 to 6 The technical solutions of the present application will be described in further detail.

[0028] In some embodiments of the present application, a battery cell is provided, comprising: a cover plate assembly 1; a shell 2 cooperating with the cover plate assembly 1 to form an accommodation space; at least one electrode assembly 3 arranged in the accommodation space, the electrode assembly 3 comprising a flat section 3-1 and a bent section 3-2 along its length direction; a plurality of support structures 4 located in the accommodation space and arranged at both ends of the electrode assembly 3 along its length direction, each support structure 4 being in abutment with the bent section 3-2 and the shell 2; along the length direction, the distance between the sides of the adjacent two support structures 4 away from the electrode assembly 3 is a first distance, and the first distance is equal to the length of the electrode assembly 3.

[0029] like Figure 1 The figure shows a cross-sectional schematic diagram of a battery cell along the height direction. The battery cell includes a connected cover plate assembly 1 and a housing 2, forming an internal receiving space. An electrode assembly 3 is disposed in the receiving space. In the figure, the L direction is the length direction of the electrode assembly 3, and the H direction is the height direction of the electrode assembly 3.

[0030] like Figure 2 As shown, Figure 1 A cross-sectional diagram of the battery cell along its length is shown. In the diagram, the T direction is the thickness direction of the electrode assembly 3. The electrode assembly 3 includes a straight section 3-1 in the middle and bent sections 3-2 at both ends along its length.

[0031] The accommodating space is provided with a support structure 4. The support structure 4 can be a solid structure or a porous structure, for example, the material of the support structure 4 can be elastic plastic or porous foam, etc., and the specific material is not limited. At least one support structure 4 is provided at each end of the electrode assembly 3 along its length direction, such as... Figure 2 As shown, a support structure 4 is set at each of the four corners of the accommodating space. Thus, two support structures 4 are provided at both ends of the electrode assembly 3 along the length direction. The support structures 4 abut against the shell 2 and the bending section 3-2 respectively. In this way, both bending sections 3-2 of the electrode assembly 3 are subjected to compression, thereby balancing the overall force on the electrode assembly 3 and avoiding excessive gap between the electrode plates at the corners, thus avoiding the phenomenon of local lithium plating.

[0032] like Figure 2 As shown in the figure, L1 is the length of the battery cell, and D1 is the distance between two adjacent support structures 4 on the side away from the electrode assembly 3 along the length direction, i.e., the first distance. Setting D1 = L1 can limit the size of the support structure 4. Compared with the related technology where a support structure 4 completely wraps around a bent section 3-2, it can avoid the support structure 4 being too long and occupying too much space, thereby improving the energy density of the battery cell. At the same time, it can also ensure the binding effect of the shell 2 on the bent section 3-2 through the support structure 4. For the area of ​​the bent section 3-2 where no support structure 4 is provided, it can directly abut against the shell 2, which can also ensure the binding effect.

[0033] This battery cell has a simple structure and is easy to manufacture. It can effectively avoid local lithium plating in the cell, extend its service life, and ensure the energy density of the cell.

[0034] In some embodiments, the support structure 4 is made of porous foam, and the porosity of the support structure 4 is 60% to 90%.

[0035] The support structure 4 is made of porous foam, for example, by mixing foaming masterbatch, flame retardant masterbatch, antioxidant masterbatch and elastic masterbatch with polyolefin and then performing electronic cross-linking radiation, which gives it good elasticity and good support effect for electrode assembly 3; porous foam has strong adsorption of electrolyte, which allows the electrolyte at the bottom of the cell to be quickly replenished upward, increases the electrolyte wetting channels, improves the wetting efficiency of the cell, and improves the uniformity of the cell interface wetting and the integrity of the formation interface; porous foam has strong resistance to electrolyte corrosion, which can ensure the stability of the cell.

[0036] The porosity of the support structure 4 is, for example, 60%, 70%, 80% or 90%, etc., without any specific limitation. On the one hand, it ensures the support effect on the electrode assembly 3, and on the other hand, it ensures the adsorption effect on the electrolyte.

[0037] In some embodiments, the height of the support structure 4 is greater than or equal to the height of the electrode assembly 3.

[0038] like Figure 1 As shown in the figure, H1 is the height of electrode assembly 3 and H2 is the height of support structure 4. H2 is set to be greater than or equal to H1. For example, H2 is 1.0H1, 1.1H1 or 1.2H1, etc. The specific value is not limited. This can ensure that the support structure 4 adsorbs the electrolyte to the top of electrode assembly 3, thereby improving the wetting effect. The test results show that the wetting time of the battery cell can be shortened by 25%, which effectively improves the production capacity of the formation stage.

[0039] In some embodiments, the support structure 4 includes a first support column 4-1, which is disposed at the corner of the accommodating space and cooperates with a portion of a bent section 3-2.

[0040] like Figure 3 The diagram shows a cross-sectional view of another type of battery cell. The support structure 4 includes a first support column 4-1, which is located at the corner of the accommodating space and can fill the gap between the corner of the housing 2 and the electrode assembly 3. The first support column 4-1 cooperates with a portion of a bent section 3-2, for example, with half of the bent section 3-2. The first support column 4-1 can be provided with an arc-shaped surface or a slope to abut against the bent section 3-2, providing local support for the electrode assembly 3.

[0041] In some embodiments, a first support column 4-1 is provided at each of the four corners of the accommodating space. Along the thickness direction of the electrode assembly 3, the distance between two adjacent first support columns 4-1 on the side away from the electrode assembly 3 is the second distance, which is equal to the total thickness of all electrode assemblies 3.

[0042] like Figure 3 As shown, a first support column 4-1 is provided at each of the four corners of the accommodating space, so that the gaps at the four corners are filled and lithium deposition is avoided at the corners.Figure 3 As shown, two electrode assemblies 3 are arranged in the accommodating space in the thickness direction, T1 represents the total thickness of the two electrode assemblies 3, and D2 represents the distance between the two first support columns 4-1 on the side of the electrode assemblies 3 away from the second support column 4-2, i.e., the second distance. In this embodiment, D2 is equal to T1, so that the support effect is ensured and the energy density of the battery cell is improved.

[0043] In some embodiments, the battery cell includes a plurality of electrode assemblies 3 arranged in a stack, and the support structure 4 further includes a second support column 4-2 arranged between the bent sections 3-2 of two adjacent electrode assemblies 3 and matched with the partial regions of the two bent sections 3-2.

[0044] As shown in FIG. 1, Figure 3 The support structure 4 further includes a second support column 4-2 arranged between the bent sections 3-2 of two adjacent electrode assemblies 3 and matched with the partial regions of the two bent sections 3-2, such as matched with half of the two bent sections 3-2. The second support column 4-2 can be provided with an arc surface or an inclined surface to abut against the bent sections 3-2 and locally support the abutting position of the two electrode assemblies 3.

[0045] When the number of electrode assemblies 3 is two, the second support column 4-2 is located in the middle of the side surface of the battery cell. When the number of electrode assemblies 3 is three, the second support column 4-2 is located at 1 / 3 of the side surface of the battery cell. The same applies to other cases.

[0046] In some embodiments, the battery cell further includes an insulating film 5 wrapped around the electrode assemblies 3, and the support structure 4 is arranged between the insulating film 5 and the electrode assemblies 3.

[0047] As shown in FIG. 1, Figure 3 The electrode assemblies 3 are wrapped with the insulating film 5, which can play a binding and insulating role. The support structure 4 can be arranged between the insulating film 5 and the electrode assemblies 3, so that the support structure 4 can be directly fixed when the insulating film 5 is wrapped, which is convenient to operate. In addition, the electrolyte infiltration channel can be increased in the insulating film 5 to improve the infiltration effect.

[0048] In some embodiments, the insulating film 5 includes a first insulating layer 5-1 arranged on the side surface of the electrode assemblies 3 and a second insulating layer 5-2 arranged on the bottom of the electrode assemblies 3. The support structure 4 is fixed on the first insulating layer 5-1, and the second insulating layer 5-2 is provided with an infiltration hole 5-3.

[0049] As shown in FIG. 1, Figure 4As shown in the drawing, it is a schematic diagram of the unwinding of an insulating film 5, which includes a plurality of first insulating layers 5-1 and a second insulating layer 5-2. The second insulating layer 5-2 is located at the bottom of the electrode assembly 3, and a plurality of infiltration holes 5-3 are provided on the second insulating layer 5-2, which can improve the infiltration effect of the bottom electrolyte on the electrode assembly 3. The first insulating layer 5-1 is located at the side of the electrode assembly 3, and the support structure 4 is fixed on the first insulating layer 5-1, for example, by adhesive or hot melt method, so that the support structure 4 can be directly matched with the electrode assembly 3 when wrapping the electrode assembly 3.

[0050] As shown in the drawing, Figure 4 three first insulating layers 5-1 are respectively arranged on both sides of the second insulating layer 5-2, and among the first insulating layers 5-1 on each side, the first insulating layer 5-1 located in the middle is used to wrap the flat section 3-1, and the first insulating layers 5-1 located at both ends are used to wrap the bent section 3-2. As shown in the drawing, Figure 5 it is a schematic diagram of the cross section of the upper insulating film 5, and a first support column 4-1 and a second support column 4-2 are respectively fixed on the first insulating layers 5-1 at both ends; as shown in the drawing, Figure 4 in the first insulating layers 5-1 located on the lower side, a first support column 4-1 is respectively fixed on the first insulating layers 5-1 at both ends, so that the wrapping of the two electrode assemblies 3 can be realized as shown in the drawing. Figure 3

[0051] In order to verify the infiltration effect of the battery, the insulating film 5 without the support structure 4 is wrapped around the electrode assembly 3, and after being assembled into the shell 2 and injected with 200g of electrolyte containing fluorescent dye, high temperature infiltration is carried out for 24h, 36h and 48h respectively, and then the battery is disassembled to test the infiltration effect. It is found that after 36h or 24h of high temperature infiltration, there will be bubbles on the surface of the electrode sheet, and after 48h of high temperature infiltration, there will be no bubbles on the surface of the electrode sheet, indicating that the infiltration efficiency is low.

[0052] Similarly, the insulating film 5 provided with the porous foam support structure 4 is wrapped around the electrode assembly 3, and after being assembled into the shell 2 and injected with 200g of electrolyte containing fluorescent dye, high temperature infiltration is carried out for 24h, 36h and 48h respectively, and then the battery is disassembled to test the infiltration effect. It is found that although after 24h of high temperature infiltration, bubbles will be generated on the surface of the electrode sheet, but after 36h or 48h of high temperature infiltration, there will be no bubbles on the surface of the electrode sheet, indicating that the support structure 4 improves the infiltration efficiency.

[0053] In addition, long cycle tests are carried out on the above two kinds of batteries, and the test results are shown in the drawing, Figure 6 It is found that the capacity retention rate of the battery using the support structure 4 is significantly higher than that of the battery without using the support structure 4. After long cycle test of the two kinds of batteries, it is found that the local lithium precipitation phenomenon of the battery with the porous foam support structure 4 is obviously improved.​

[0054] In some embodiments of the present application, a secondary battery is provided, which comprises the battery cell according to any one of the above embodiments. The secondary battery can be applied to an electric device, which can be a vehicle, a mobile phone, a portable device, a notebook computer, a ship, a spacecraft, an electric toy, an electric tool, etc. The vehicle can be a fuel automobile, a gas automobile or a new energy automobile, and the new energy automobile can be a pure electric automobile, a hybrid electric automobile or a range extended automobile, etc. The spacecraft includes an airplane, a rocket, a space shuttle and a spacecraft, etc. The electric toy includes a fixed or mobile electric toy, such as a game machine, an electric automobile toy, an electric ship toy and an electric airplane toy, etc. The electric tool includes a metal cutting electric tool, a grinding electric tool, an assembling electric tool and a railway electric tool, such as an electric drill, an electric grinder, an electric wrench, an electric screwdriver, an electric hammer, an impact electric drill, a concrete vibrator and an electric planer, etc.

[0055] It should be understood by those of ordinary skill in the art that the above discussion of any of the embodiments is merely exemplary and is not intended to suggest the scope of the present application (including the claims) is limited to these examples; the embodiments or technical features among different embodiments can also be combined, and the steps can be implemented in any order, and there are many other changes to the different aspects of the embodiments of the present application as described above. In order to be brief, they are not provided in detail.

[0056] In addition, although the details are described to describe the exemplary embodiments of the present application, it is obvious to those skilled in the art that the embodiments of the present application can be implemented without these details or with changes to these details. Therefore, these descriptions should be considered as illustrative rather than limiting.

[0057] Although the present application has been described in conjunction with the embodiments thereof, according to the foregoing description, many alternatives, modifications and variations will be apparent to those skilled in the art in light of the foregoing description.

[0058] The embodiments of the present application are intended to cover all such alternatives, modifications and variations as falling within the broad scope of the appended claims. Accordingly, any omission, modification, equivalent replacement, improvement, etc. made within the spirit and principle of the embodiments of the present application should be included in the protection scope of the present application.

Claims

1. An electric cell, characterized by, The application relates to a battery cell. The battery cell comprises: a cover plate assembly; a shell cooperating with the cover plate assembly to form a containing space; at least one electrode assembly arranged in the containing space, the electrode assembly comprising a straight section and a bent section along the length direction of the electrode assembly; 2. The electric cell of claim 1, wherein, a plurality of support structures arranged in the containing space and at two ends of the electrode assembly along the length direction, each of the support structures being in abutment with the bent section and the shell respectively; along the length direction, the distance between two adjacent support structures away from the side of the electrode assembly is a first distance, and the first distance is equal to the length of the electrode assembly.

3. The electric cell of claim 2, wherein, The support structure is made of porous foam, and the porosity of the support structure is 60-90%.

4. The electric cell of claim 1, wherein, The height of the support structure is greater than or equal to the height of the electrode assembly.

5. The electric cell of claim 4, wherein, The support structure comprises a first support column arranged at a corner of the containing space and in cooperation with a partial area of one bent section.

6. The electric cell of claim 4, wherein, The containing space is provided with one first support column at each corner, and along the thickness direction of the electrode assembly, the distance between two adjacent first support columns away from the side of the electrode assembly is a second distance, and the second distance is equal to the total thickness of the at least one electrode assembly.

7. The electric cell of claim 1, wherein, The battery cell comprises a plurality of electrode assemblies arranged in stacks, and the support structure further comprises a second support column arranged between the bent sections of two adjacent electrode assemblies and in cooperation with partial areas of the two bent sections.

8. The electric cell of claim 7, wherein, The battery cell further comprises an insulating film wrapping the electrode assemblies, and the support structure is located between the insulating film and the electrode assemblies.

9. The electric cell of claim 8, wherein, The insulating film comprises a first insulating layer located at the side of the electrode assembly, and the support structure is fixed on the first insulating layer.

10. A secondary battery characterized by comprising: The insulating film further comprises a second insulating layer located at the bottom of the electrode assembly, and the second insulating layer is provided with an infiltration hole. The battery cell according to any one of claims 1-9.

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