A type of battery cell

Abstract

This utility model discloses a battery cell, applied in the field of battery technology. The electrode includes a current collector and tabs protruding from the current collector. At least two tabs of the same polarity are stacked along the thickness direction of the cell and then converge to form a multi-tab structure. The stacked electrode sheets form the cell body, and the multi-tab structure is formed on the side of the cell body, having connection points based on the convergence of the tabs. The cell also includes a first fixing member, comprising a first bonding portion, a second bonding portion, and a third bonding portion. The first bonding portion is bonded to the surface of the cell body and fixed thereto. The third bonding portion is bonded to the connection points and fixed thereto. The second bonding portion is located between the first and third bonding portions. The thickness of the first bonding portion is less than the thickness of the third bonding portion. The thicker third bonding portion ensures protection of the solder joints, while the thinner first bonding portion reduces the impact on the cell's energy density.

Description

Technical Field

[0001] This utility model relates to the field of battery technology, and in particular to a battery cell. Background Technology

[0002] With the widespread adoption and application of lithium-ion batteries, the requirements for lithium batteries are becoming increasingly stringent, with cycle life, safety, and fast charging being key research areas. In the production process of multi-tab lithium-ion batteries, each layer of tabs for both the positive and negative electrodes needs to be welded together to form a single tab structure, which is then welded to a conductive sheet. After welding, solder joints are formed at the connection area between the tabs and the conductive sheet. To protect the tabs and conductive sheet and prevent direct contact between the solder joints and the battery cell, protective adhesive is applied to the connection area between the tabs and the conductive sheet, acting as an isolation and protection against punctures. In existing technologies, balancing the protection of the solder joints with the battery's energy density is a problem that urgently needs to be solved by those skilled in the art. Utility Model Content

[0003] The purpose of this invention is to provide a battery cell that can ensure protection of the connection points while having a high energy density.

[0004] To solve the above-mentioned technical problems, this utility model provides a battery cell, including an electrode assembly. The electrode assembly includes a cell body and tabs. The cell body includes at least two electrodes with opposite polarities and a separator disposed between any two electrodes. The tabs are formed on the side of the cell body and include multiple tab pieces. The tab pieces extend from the current collector of the electrodes and are fixedly connected to the conductive sheet to form a connection area.

[0005] The battery cell further includes a first fixing member, which includes a first bonding portion, a second bonding portion, and a third bonding portion; the first bonding portion is bonded to the surface of the battery cell body and fixed to the battery cell body, the third bonding portion is bonded to the connection area, and the second bonding portion is located between the first bonding portion and the third bonding portion; the thickness of the first bonding portion is less than the thickness of the third bonding portion.

[0006] Optionally, the tab includes a tab root and a transition region, the tab root is connected to the cell body, the transition region connects the tab root and the connection area, and the second bonding portion is bonded to at least one of the tab root and the transition region; the thickness of the second bonding portion is not less than the thickness of the first bonding portion and not greater than the thickness of the third bonding portion.

[0007] Optionally, the first fixing member includes a first substrate layer and a first adhesive layer located on one side of the first substrate layer, wherein the first adhesive layer is disposed only in the first bonding portion and the third bonding portion.

[0008] Optionally, the thickness of the first substrate layer located at the first bonding portion is less than the thickness of the first substrate layer located at the third bonding portion.

[0009] Optionally, the thickness of the first substrate layer located in the second bonding portion is greater than the thickness of the first substrate layer located in the first bonding portion, but less than the thickness of the first substrate layer located in the third bonding portion.

[0010] Optionally, in the third bonding portion, a deformation-resistant layer is provided on one side surface of the first substrate layer, and the first adhesive layer is provided on the side surface of the deformation-resistant layer away from the first substrate layer in the third bonding portion.

[0011] Optionally, in the second bonding portion, the anti-deformation layer is provided on one side surface of the first substrate layer.

[0012] Optionally, the thickness of the anti-deformation layer is no more than one-tenth of the thickness of the first substrate layer located at the first bonding portion.

[0013] Optionally, the electrode and the separator are wound around each other multiple times to form the cell body, and the outermost electrode of the battery cell includes a tail section, which is attached and fixed to the cell body by a second fixing member;

[0014] The active material layer of the electrode has a main body region and a thickness reduction region with gradually decreasing thickness along the first direction pointing to the side where the electrode single piece is located. The cell body forms a main body portion based on the main body region and a thickness reduction portion based on the thickness reduction region.

[0015] The second fixing member includes a fourth fitting portion attached to the main body and a fifth fitting portion attached to the thickness reduction portion, wherein the thickness of the fifth fitting portion gradually increases along the first direction.

[0016] Optionally, the second fixing member includes a second substrate layer and a second adhesive layer located on the side of the second substrate layer facing the battery cell body;

[0017] The thickness of the second substrate layer located in the fifth bonding portion gradually increases along the first direction.

[0018] The present invention provides a battery cell comprising an electrode assembly, the electrode assembly including a cell body and tabs. The cell body includes at least two electrodes with opposite polarities and a separator disposed between any two electrodes. Tabs are formed on the side of the cell body and include multiple tab pieces. Each tab piece extends from a current collector of an electrode and is fixed to a conductive sheet to form a connection area. The battery cell also includes a first fixing member, which includes a first bonding portion, a second bonding portion, and a third bonding portion. The first bonding portion is bonded to the surface of the cell body and fixed to the cell body. The third bonding portion is bonded to the connection area. The second bonding portion is located between the first bonding portion and the third bonding portion. The thickness of the first bonding portion is less than the thickness of the third bonding portion.

[0019] By dividing the first fixing component into a first bonding part, a second bonding part, and a third bonding part, the thickness of the third bonding part is relatively large, which can ensure the protection of the solder joint formed between the electrode tab and the conductive sheet. On the other hand, the thickness of the first bonding part, which is bonded to the front of the battery cell body, is relatively small, which can effectively avoid the influence of the first bonding part on the energy density of the battery cell body. Attached Figure Description

[0020] To more clearly illustrate the technical solutions of the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a schematic diagram of the structure of a battery cell provided in an embodiment of the present utility model;

[0022] Figure 2 for Figure 1 A schematic diagram of the side view structure;

[0023] Figure 3 This is a structural schematic diagram of the first fixing member provided in the embodiment of the present utility model;

[0024] Figure 4 This is a structural schematic diagram of the second type of first fixing member provided in an embodiment of the present utility model;

[0025] Figure 5 This is a schematic diagram of the structure of a specific battery cell provided in an embodiment of the present utility model;

[0026] Figure 6 This is a structural schematic diagram of a second fixing member provided in an embodiment of the present utility model;

[0027] Figure 7 for Figure 5 A partial side view of the structure.

[0028] In the figure: 1. Battery cell body, 2. Electrode, 3. First fixing member, 31. First bonding part, 32. Second bonding part, 33. Third bonding part, 34. First substrate layer, 35. First adhesive layer, 36. Deformation-resistant layer, 4. Second fixing member, 41. Fourth bonding part, 42. Fifth bonding part, 43. Second substrate layer, 44. Second adhesive layer, 5. Conductive sheet. Detailed Implementation

[0029] The core of this invention is to provide a battery cell. In the prior art, in order to ensure that the solder joint protective adhesive can effectively protect the solder joint, the thickness of the solder joint protective adhesive cannot be too thin. A certain thickness of solder joint protective adhesive can not only play a buffering role but also prevent the solder joint from being punctured. However, the solder joint protective adhesive cannot be too thick either, as excessively thick solder joint protective adhesive will affect the energy density of the battery and also affect battery assembly.

[0030] The battery cell provided by this utility model divides the first fixing component into a first bonding part, a second bonding part, and a third bonding part. The third bonding part is thicker to ensure the protection of the solder joint formed between the electrode tab and the conductive sheet. The first bonding part, which is bonded to the front of the cell body, is thinner to effectively avoid affecting the energy density of the cell body.

[0031] To enable those skilled in the art to better understand the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] Example 1

[0033] Please refer to Figures 1 to 4 , Figure 1 This is a schematic diagram of the structure of a battery cell provided in an embodiment of the present utility model; Figure 2 for Figure 1 A schematic diagram of the side view structure; Figure 3 This is a structural schematic diagram of the first fixing member provided in the embodiment of the present utility model; Figure 4 This is a structural schematic diagram of the second type of first fixing member provided in an embodiment of the present utility model.

[0034] See Figure 1 as well as Figure 2In this embodiment, the battery cell includes an electrode assembly, which includes a cell body 1 and tabs 2. The cell body 1 includes at least two electrodes with opposite polarities and a separator film disposed between any two electrodes. The tabs 2 are formed on the side of the cell body 1 and include multiple tab pieces. The tab pieces extend from the current collectors of the electrodes and are fixed to the conductive sheet 5 to form a connection area. The battery cell also includes a first fixing member 3, which includes a first bonding portion 31, a second bonding portion 32, and a third bonding portion 33. The first bonding portion 31 is bonded to the surface of the cell body 1 and fixed to the cell body 1. The third bonding portion 33 is bonded to the connection area. The second bonding portion 32 is located between the first bonding portion 31 and the third bonding portion 33. The thickness of the first bonding portion 31 is less than the thickness of the third bonding portion 33.

[0035] In this embodiment, the at least two electrodes include at least one positive electrode and at least one negative electrode. The aforementioned separator needs to be disposed between the positive and negative electrodes to separate them from each other. The specific material of the separator can be set according to the actual situation and is not specifically limited here.

[0036] In this embodiment, the aforementioned electrode stacking can form the battery cell body 1. Different battery cell bodies 1 with different structures can be formed depending on the stacking method. For example, a battery cell body 1 formed by winding the aforementioned electrode and separator multiple times is a wound battery cell, while a battery cell body 1 formed by stacking the aforementioned electrode and separator along the thickness direction is a stacked battery cell. The specific structure of the battery cell body 1 is not specifically limited here and can be determined according to the actual situation. Typically, the surface of the aforementioned battery cell body 1 is covered by a separator, meaning that the outermost structure of the battery cell body 1 is usually a separator.

[0037] In this embodiment, the electrode includes a current collector and a tab protruding from the current collector. Specifically, it also includes an active material layer disposed on one or both surfaces of the current collector, wherein the positive electrode has a positive active material layer, and the negative electrode has a negative active material layer. The specific material of the active material layer can be found in existing technology and will not be elaborated here. The current collector is a component that collects the current generated by the electrode, and the tab protrudes from the current collector. The current in the current collector is transmitted out of the electrode through the tab. The tab directly leading out of the electrode is usually called a soft tab. In this embodiment, at least one positive tab extending from the positive electrode and at least one negative tab extending from the negative electrode are provided. When there are at least two positive tabs or at least two negative tabs, i.e., at least two tabs of the same polarity, they need to be stacked along the thickness direction of the battery cell to form tab 2. This thickness direction is also the direction of electrode stacking. The aforementioned tab 2 needs to be fixed to the conductive sheet 5. The area where the tab 2 and the conductive sheet 5 specifically contact is the connection area, and the aforementioned solder joint is specifically formed in this connection area. The aforementioned conductive sheet 5 can be a rigid tab connected to a soft tab, and the conductive sheet 5 is specifically the electrode that the battery cell connects to the outside. In this embodiment, the tab 2 formed by the aforementioned positive tab needs to be connected to one conductive sheet 5, and the tab 2 formed by the aforementioned negative tab needs to be connected to another conductive sheet 5.

[0038] In this embodiment, the aforementioned tab 2 is specifically formed on the side of the battery cell body 1. That is, multiple tab pieces extend from the side of the battery cell body 1 and converge to form the tab 2. The tab 2 and the conductive sheet 5 are in contact in the connection area, that is, the aforementioned solder joint is formed in the connection area.

[0039] This embodiment includes a first fixing member 3, which needs to cover the solder joints in the connection area and provide a certain buffering effect as well as prevent the connection points from being punctured. Specifically, the first fixing member 3 needs to be connected to the battery cell body 1 for fixation. Specifically, the first fixing member 3 in this embodiment includes a first fitting portion 31, a second fitting portion 32, and a third fitting portion 33. In this embodiment, the direction pointing towards the side of the tab in the electrode sheet is defined as the first direction. For example, for a wound battery cell, the tab is usually led out from the long side of the electrode sheet, so the first direction can be the width direction of the electrode sheet. The first fixing member 3 is usually a strip-shaped structure extending along the first direction. The first fitting portion 31 is usually located at one end of the first fixing member 3, the third fitting portion 32 is usually located at the other end of the first fixing member 3, and the second fitting portion 32 is located between the two.

[0040] In this embodiment, the third bonding portion 33 is used to bond the connection area where the tab 2 and the conductive sheet 3 are connected. Specifically, it needs to cover the solder joints in the connection area to prevent puncture. The third bonding portion 33 usually needs to cover the solder joints and extend to the root of the tab 2, that is, the third bonding portion 33 extends towards the cell body 1 to the connection between the cell body 1 and the tab 2.

[0041] The first bonding portion 31 is bonded to the surface of the battery cell body 1 and fixed to the battery cell body 1. Specifically, the first bonding portion 31 can be bonded to the surface of the battery cell body 1 in the thickness direction and is fixedly connected to the separator on the surface of the battery cell body 1. Specifically, the first bonding portion 31 is bonded to the area of ​​the surface of the battery cell body 1 near the tab 2 and extends to the edge of the battery cell body 1.

[0042] The aforementioned second bonding portion 32 is located between the first bonding portion 31 and the third bonding portion 33, connecting the first bonding portion 31 and the third bonding portion 33 into a whole. Typically, the second bonding portion 32 is bonded to the surface of the tab 2 away from the main body of the battery cell, that is, it is bonded to the outermost tab piece of the tab 2 away from the main body of the battery cell 1. This tab piece is usually the tab piece corresponding to the outermost electrode sheet in the main body of the battery cell 1.

[0043] In this embodiment, the tab 2 includes a tab root and a transition region. The tab root is connected to the cell body 1, and the transition region connects the tab root and the connection area. The second bonding portion 32 is bonded to at least one of the tab root and the transition region to connect the first bonding portion 31 and the third bonding portion 33. Each tab has an end connected to the current collector, an end away from the current collector, and a transition section between the two ends. The tab root is a stacked structure formed by stacking the ends of multiple tabs connected to the current collector. The tab 2 is specifically connected to the cell body 1 through the tab root. The ends of multiple tabs away from the current collector are connected to the conductive sheet 5 to form solder joints corresponding to the connection area. The corresponding transition region is a stacked structure formed by stacking the transition sections of multiple tabs. This transition region specifically connects the tab root and the connection area. In this embodiment, the second bonding portion 32 is specifically bonded to at least one of the tab root and the transition area. That is, the second bonding portion 32 can be bonded only to the tab root, only to the transition area, or simultaneously to both the tab root and the transition area, and connects the first bonding portion 31 and the third bonding portion 33.

[0044] In this embodiment, the thickness of the first bonding portion 31 needs to be less than that of the third bonding portion 33; that is, the first bonding portion 31 needs to be thinner, while the third bonding portion 33 needs to be thicker. This is because the function of the third bonding portion 33 is to prevent solder joint puncture, thus requiring a thicker thickness to achieve this effect. Since the first bonding portion 31 does not contact the tab piece, its thickness can be thinner to reduce the volume occupied by the first bonding portion 31 in the main body 1 of the battery cell, thereby increasing the energy density of the battery. The second bonding portion 32, as a transition structure between the first bonding portion 31 and the third bonding portion 33, typically has a thickness neither greater than that of the third bonding portion 33 nor less than that of the first bonding portion 31, serving as a transitional element. Of course, the thickness of the second bonding portion 32 can be equal to, less than, or greater than that of the first bonding portion 31 or the third bonding portion 33; there is no specific limitation on the thickness of the second bonding portion 32. Because it serves as a transition, its thickness is typically between the first bonding portion 31 and the third bonding portion 33. This second bonding portion 32 can reduce the amount of the first fixing member 3 used to a certain extent, reduce the weight of the battery cell, and also play a role in protecting the solder joints.

[0045] Specifically, in this embodiment, the first fixing member 3 includes a first substrate layer 34 and a first adhesive layer 35 located on one side of the first substrate layer 34. The first substrate layer 34 serves a load-bearing function, and the first adhesive layer 35 serves a bonding and fixing function. In the first fixing member 3, the first adhesive layer 35 can be provided only in the first bonding portion 31 and the third bonding portion 33, and not in the second bonding portion 32. In this case, the surface of the second bonding portion 32 facing the battery cell body 1 is a non-adhesive surface, and the second bonding portion 32 will not adhere to the tab piece on the side wall of the battery cell body 1, thereby avoiding the problem of the tab piece tearing. The bonding effect of the first fixing member 3 can be achieved solely by the adhesive layer of the first bonding portion 31 and the adhesive layer of the third bonding portion 33.

[0046] In this embodiment, the material of the first substrate layer 34 can be polyethylene terephthalate (PET) or polyimide (PI), and the material of the first adhesive layer 35 can be polymethyl methacrylate (PMMA) or rubber. The thickness of the first adhesive layer 35 can range from 10 μm to 30 μm, and the peel strength of the first adhesive layer 35 can be from 0.32 N / mm to 0.75 N / mm, the initial tack can be from 0.3 N / mm to 1.2 N / mm, and the unwinding force can be from 0.004 N / mm to 0.18 N / mm.

[0047] See Figure 3In one feasible example, the thickness difference between the first bonding portion 31, the second bonding portion 32, and the third bonding portion 33 can be based on the thickness difference of the first substrate layer 34 at different bonding portions. Specifically, in this example, the thickness of the first substrate layer 34 located in the first bonding portion 31 can be less than the thickness of the first substrate layer 34 located in the third bonding portion 33, such that the thickness of the first bonding portion 31 is less than the thickness of the third bonding portion 33. Correspondingly, the thickness of the first substrate layer 34 located in the second bonding portion 32 can be greater than the thickness of the first substrate layer 34 located in the first bonding portion 31 and less than the thickness of the first substrate layer 34 located in the third bonding portion 33, such that the thickness of the second bonding portion 32 is between that of the first bonding portion 31 and the third bonding portion 33.

[0048] Specifically, in this embodiment, the thickness of the first substrate layer 34 in the first bonding portion 31 ranges from 20μm to 50μm; the thickness of the first substrate layer 34 in the second bonding portion 32 ranges from 40μm to 70μm; and the thickness of the first substrate layer 34 in the third bonding portion 33 ranges from 50μm to 120μm. That is, if the thickness of the first substrate layer 34 in the first bonding portion 31 is h1, then h1 ranges from 20μm to 50μm; if the length of the first substrate layer 34 in the first bonding portion 31 in the first direction is L1, then L1 ranges from 20mm to 60mm. If the thickness of the first substrate layer 34 in the second bonding portion 32 is h2, then h2 ranges from 40μm to 70μm; if the length of the first substrate layer 34 in the second bonding portion 32 in the first direction is L2, then L2 ranges from 10mm to 50mm. If the thickness of the first substrate layer 34 in the third bonding portion 33 is h3, then the value of h3 ranges from 50μm to 120μm; if the length of the first substrate layer 34 in the third bonding portion 33 in the first direction is L3, then the value of L3 ranges from 20mm to 30mm, and the distance between the edge of the third bonding portion 33 and the edge of the connection area during bonding is usually 1mm to 2mm, that is, the third bonding portion 33 needs to extend 1mm to 2mm beyond the connection area to ensure coverage of the solder joint.

[0049] In this embodiment, an anti-deformation layer 36 can be provided on one side surface of the first substrate layer 34 in the third bonding portion 33, and the first adhesive layer 35 is disposed on the surface of the anti-deformation layer 36 away from the first substrate layer 34 in the third bonding portion 33. Since the tab single piece and the tab 2 generate heat during operation, and the material of the first substrate layer 34 is usually a polymer material, it is prone to material deformation and shrinkage during heating. To avoid shrinkage of the first substrate layer 34 due to heat, this embodiment can additionally provide an anti-deformation layer 36 in the third bonding portion 33, which can be located between the first substrate layer 34 and the first adhesive layer 35. Since the second bonding portion 32 in this embodiment will be bonded to the tab single piece on the side wall of the cell body 1, the second bonding portion 32 can also be provided with the aforementioned anti-deformation layer 36. In this case, the anti-deformation layer 36 in the second bonding portion 32 will be located on the surface of the first substrate layer 34 facing the cell body 1.

[0050] The aforementioned anti-deformation layer 36 includes a ceramic coating, such as an alumina coating. Based on the characteristic that ceramic coatings are not easily deformed at high temperatures, the thermal stability and safety of the first fixing member 3 are increased. Taking the ceramic coating as an example, this anti-deformation layer 36 not only improves the thermal stability of the first fixing member 3 but also has a certain thermal conductivity, which can improve the thermal safety performance of the battery cell. Furthermore, the aforementioned tab 2 generates a large amount of heat when the battery cell is operating. By thickening the third bonding portion 33 with a ceramic coating, its heat dissipation performance can be increased. This is because the ceramic coating allows the third bonding portion 33 to have more space for heat conduction, thereby reducing the probability of thermal runaway caused by heat concentration and improving the safety of the battery cell.

[0051] In this embodiment, to ensure the bending effect and flexibility of the first fixing member 3, the thickness of the anti-deformation layer 36 is typically no greater than one-tenth of the thickness of the first substrate layer 34 located in the first bonding portion 31. Let the thickness of the anti-deformation layer 36 in the second bonding portion 32 be H2, and the thickness of the anti-deformation layer 36 in the third bonding portion 33 be H3, then both H2 and H3 must be ≤ h1 / 10. Typically, in this embodiment, the thickness of the anti-deformation layer 36 in the third bonding portion 33 needs to be no less than the thickness of the anti-deformation layer 36 in the second bonding portion 32, i.e., H3 ≥ H2. The value range of the thickness H2 of the anti-deformation layer 36 in the second bonding portion 32 is 1 μm to 5 μm, and the value range of the thickness H3 of the anti-deformation layer 36 in the third bonding portion 33 is 2 μm to 5 μm. In this embodiment, the thickness of the first adhesive layer 35 in the first bonding portion 31 can be set to H1, and the thickness of the first adhesive layer 35 in the third bonding portion 33 can be set to H4. H1 can be set to H4, that is, the thickness of the first adhesive layer 35 in the first bonding portion 31 is equal to the thickness of the first adhesive layer 35 in the third bonding portion 33.

[0052] See Figure 4 Based on this, in this embodiment, the thickness of the first bonding portion 31 can be less than the thickness of the third bonding portion 33, based on the first substrate layer 34 without thickness undulations. Specifically, the thickness of the first substrate layer 34 can be set to be equal everywhere, i.e., h1=h2=h3. Since the third bonding portion 33 has an additional anti-deformation layer 36 compared to the first bonding portion 31, under the premise that the thickness of the first adhesive layer 35 in the first bonding portion 31 is approximately equal to the thickness of the first adhesive layer 35 in the third bonding portion 33, the thickness of the first bonding portion 31 can be less than the thickness of the third bonding portion 33. And when the thickness of the anti-deformation layer 36 in the second bonding portion 32 is greater than or equal to the thickness of the first adhesive layer 35 in the first bonding portion 31, the thickness of the second bonding portion 32 can be guaranteed to be greater than or equal to the thickness of the first bonding portion 31.

[0053] In this embodiment, the first bonding portion 31, since it does not contact the individual tab pieces and is directly bonded to the separator film on the surface of the cell body 1, does not require the addition of an anti-deformation layer 36, and a thinner first substrate layer 34 can be used, reducing the weight of the first fixing member 3. The anti-deformation layer 36 of the second bonding portion 32 and the third bonding portion 33 not only effectively prevents short circuits caused by reverse insertion of the individual tab pieces, but also improves the heat shrinkage resistance of the first fixing member 3 and plays a role in heat conduction. In this embodiment, the overall tensile strength of the first fixing member 3 is greater than or equal to 100 MPa, and the puncture resistance is greater than or equal to 10 N.

[0054] The battery cell provided in this embodiment divides the first fixing member 3 into a first bonding portion 31, a second bonding portion 32, and a third bonding portion 33. The third bonding portion 33 is thicker to ensure the protection of the solder joints. The first bonding portion 31, which is bonded to the front of the cell body 1, is thinner to effectively avoid its impact on the cell's energy density.

[0055] The specific structure of the battery cell provided in this embodiment will be described in detail in the following embodiments.

[0056] Example 2

[0057] Please refer to Figures 5 to 7 , Figure 5 This is a schematic diagram of the structure of a specific battery cell provided in an embodiment of the present utility model; Figure 6 This is a structural schematic diagram of a second fixing member provided in an embodiment of the present utility model; Figure 7 for Figure 5 A partial side view of the structure.

[0058] Unlike the embodiments described above, this embodiment further defines the second fixing member 4 in the battery cell. The remaining details have been described in detail in the embodiments above and will not be repeated here.

[0059] See Figure 5 In this embodiment, the electrode and the separator are wound multiple times to form the cell body 1. The outermost electrode of the battery cell includes a tail section, which is attached and fixed to the cell body 1 by a second fixing member 4. The active material layer of the electrode has a main body area and a thickness reduction area that gradually decreases in thickness along the first direction along the first direction. The cell body 1 forms a main body portion based on the main body area and a thickness reduction portion based on the thickness reduction area. The second fixing member 4 includes a fourth bonding portion 41 bonded to the main body portion and a fifth bonding portion 42 bonded to the thickness reduction portion. The thickness of the fifth bonding portion 42 gradually decreases along the first direction.

[0060] In this embodiment, the cell body 1 is specifically a wound cell body 1. The tail section is the structure of the outermost electrode of the battery cell, which extends from the cell body 1 and is the tail structure of the outermost electrode of the cell. This tail section needs to be attached to the cell body 1. In this embodiment, the tail section is specifically fixedly connected to the cell body 1 through the second bonding part 32.

[0061] In this embodiment, a battery cell body 1 typically has two tabs 2, one corresponding to the positive terminal and the other to the negative terminal. Correspondingly, two of the aforementioned first fixing members 3 are provided within the battery cell, each abutting its corresponding tab 2. In this embodiment, the aforementioned termination section typically ends in the area between the two tabs 2, allowing the second fixing member 4 to abut between the two first fixing members 3. Of course, the specific position of the second fixing member 4 depends on the position of the aforementioned termination section and is not specifically limited here.

[0062] Because the active material layer in the electrode is in a slurry state before coating and has a certain degree of fluidity, the slurry will form a thickness reduction zone after coating. Within this thickness reduction zone, the coating thickness at the electrode edge differs from the coating thickness in the middle of the electrode. That is, the electrode coating amount is relatively small in the thickness reduction zone, which will have a certain impact on the energy density of the battery cell. Specifically, in this embodiment, the active material layer has a main region and a thickness reduction zone along a first direction pointing towards the side of the electrode tab. The thickness of the active material layer in the main region is relatively uniform, while the thickness of the active material layer in the thickness reduction zone gradually decreases along the first direction. The main region is often also called the effective region, and the thickness reduction zone is closer to the electrode tab than the main region. In the active material layer, the main region is usually a region with a relatively constant thickness, while the thickness reduction zone is a region with a larger degree of thickness reduction, lower thickness uniformity, and a continuously decreasing thickness trend along the first direction. In this embodiment, the positions of the main body region and the thickness reduction region can be located as follows: From the thickness reduction region to the main body region, a test point is established at 50 μm intervals. Then, the thickness of the active material layer is measured at each of these measurement points using equipment such as an electron microscope. The point where the thickness increase rate between two adjacent measurement points is less than 2% is the boundary between the edge region and the main body region. The area from the boundary point to the edge of the active material layer near the tab monolith is the region where the thickness reduction region is located. Of course, the above interval distance can be 10 μm or other values, and is not limited here.

[0063] In this embodiment, due to the stacking of electrode sheets, the stacking of the main body regions in each electrode sheet forms the main body 1 of the cell body 1, and the stacking of the thickness reduction regions in each electrode sheet forms the thickness reduction region in the cell body 1. Obviously, the thickness of the thickness reduction region gradually decreases along the first direction, resulting in a thinner edge of the cell. However, during the hot pressing process, the thinner edge of the cell cannot effectively bear the force, leading to poor electrode bonding at the edge of the cell. This will affect the electrode interface later, increasing internal resistance and posing a risk of lithium plating on the negative electrode.

[0064] In this embodiment, the second fixing member 4 extends along the first direction, with one part attached to the main body and the other part attached to the thickness-reduced portion. The part attached to the main body is the fourth attachment portion 41, and the part attached to the thickness-reduced portion is the fifth attachment portion 42. In this embodiment, the thickness of the fifth attachment portion 42 gradually increases along the first direction. This means that the fifth attachment portion 42 can at least partially offset the unevenness of the cell body 1 surface caused by the thickness-reduced area, compensate for the thinning effect of the electrode sheet at the edge of the single electrode tab, ensure the consistency of the overall thickness of the cell body 1, and achieve consistent electrode bonding during the hot-pressing process. Correspondingly, the thickness of the fourth attachment portion 41 needs to be consistent to avoid areas of inconsistent thickness in the main body.

[0065] In this embodiment, the second fixing member 4 includes a second substrate layer 43 and a second adhesive layer 44 located on the side of the second substrate layer 43 facing the battery cell body 1; the thickness of the second substrate layer 43 located in the fifth bonding portion 42 gradually increases along the first direction. That is, the second fixing portion is specifically composed of the second substrate layer 43 and the second adhesive layer 44 disposed on the surface of the second substrate layer 43, wherein the thickness of the second adhesive layer 44 is generally equal everywhere, while the thickness of the second substrate layer 43 in the fifth bonding portion 42 gradually increases along the first direction to ensure the consistency of the thickness of the battery cell body 1.

[0066] See Figure 6 In this embodiment, the thickness of the second substrate layer 43 at its thickest position in the fifth bonding portion 42 ranges from 40 μm to 60 μm; and / or, the ratio of the length of the fourth bonding portion 41 along the first direction to the length of the battery cell body 1 along the first direction ranges from 90:100 to 95:100. Let the thickness of the second substrate layer 43 at its thickest position in the fifth bonding portion 42 be h5, then h5 ranges from 40 μm to 60 μm; let the length of the fourth bonding portion 41 along the first direction be L4, and the length of the battery cell body 1 along the first direction can be the height of the battery cell body 1, then the ratio of the length of L4 to the height of the battery cell is 90:100 to 95:100. The length L4 of the fourth bonding portion 41 along the first direction can range from 150 mm to 300 mm, and the thickness h4 of the second substrate layer 43 in the fourth bonding portion 41 ranges from 16 μm to 30 μm. Let L5 be the length of the fifth bonding part 42 along the first direction. Then the value of L5 is in the range of 5mm to 8mm.

[0067] The material of the second adhesive layer 44 can be polymethyl methacrylate (PMMA) or rubber. If the thickness of the second adhesive layer 44 is H5, then the value of H5 ranges from 6 μm to 25 μm. The peel strength of the second adhesive layer 44 is 0.1 N / mm to 0.2 N / mm, the initial tack is 0.06 N / mm to 0.2 N / mm, and the unwinding force is 0.004 N / mm to 0.08 N / mm.

[0068] See Figure 7 In this embodiment, along the first direction, the edge of the fifth bonding portion 42 of the second fixing member 4 away from the fourth bonding portion 41 needs to be aligned with the thinnest edge of the active material layer of the outermost electrode sheet, which is usually the negative electrode sheet, in the battery cell body 1. Let the length by which the edge of the outermost separator extends beyond the edge of the active material layer in the outermost electrode sheet be a, where a = 2.5 mm ± 1 mm, and the length by which the edge of the active material layer in the outermost electrode sheet extends beyond the edge of the active material layer in the second outermost electrode sheet be b, where b = 2 mm ± 1 mm. The aforementioned second outermost electrode sheet is usually the positive electrode sheet.

[0069] In this embodiment, the length of the first fixing member 3 along a second direction perpendicular to the first direction, i.e., the width of the first fixing member 3, is set to W1, with a value ranging from 30mm to 60mm. In the second direction, i.e., the width direction, the centers of the first fixing member 3 and the electrode tab 2 are aligned, and the width of the first fixing member 3 exceeds the width of the electrode tab 2 by 2mm to 5mm. The length of the second fixing member 4 along the second direction, i.e., the width of the second fixing member 4, is set to W2, with a value ranging from 20mm to 40mm.

[0070] The various embodiments in this specification are described in a progressive manner. Each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0071] Finally, it should be noted that in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0072] The present invention provides a detailed description of a battery cell. Specific examples have been used to illustrate the principles and implementation methods of the present invention. The descriptions of these embodiments are merely for the purpose of helping to understand the method and core ideas of the present invention. It should be noted that those skilled in the art can make various improvements and modifications to the present invention without departing from its principles, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. A battery cell, characterized in that, The battery includes an electrode assembly, which includes a battery cell body and tabs. The battery cell body includes at least two electrodes with opposite polarities and a separator disposed between any two electrodes. The tabs are formed on the side of the battery cell body and include a plurality of tab pieces. The tab pieces extend from the current collector of the electrodes and are fixed to a conductive sheet to form a connection area. The battery cell further includes a first fixing member, which includes a first bonding portion, a second bonding portion, and a third bonding portion; the first bonding portion is bonded to the surface of the battery cell body and fixed to the battery cell body, the third bonding portion is bonded to the connection area, and the second bonding portion is located between the first bonding portion and the third bonding portion; the thickness of the first bonding portion is less than the thickness of the third bonding portion.

2. The battery cell according to claim 1, characterized in that, The tab includes a tab root and a transition region. The tab root is connected to the cell body. The transition region connects the tab root and the connection area. The second bonding portion is bonded to at least one of the tab root and the transition region. The thickness of the second bonding portion is not less than the thickness of the first bonding portion and not greater than the thickness of the third bonding portion.

3. The battery cell according to claim 2, characterized in that, The first fixing member includes a first substrate layer and a first adhesive layer located on one side of the first substrate layer. The first adhesive layer is only disposed in the first bonding portion and the third bonding portion.

4. The battery cell according to claim 3, characterized in that, The thickness of the first substrate layer located at the first bonding portion is less than the thickness of the first substrate layer located at the third bonding portion.

5. The battery cell according to claim 4, characterized in that, The thickness of the first substrate layer located at the second bonding portion is greater than the thickness of the first substrate layer located at the first bonding portion, but less than the thickness of the first substrate layer located at the third bonding portion.

6. The battery cell according to claim 3, characterized in that, In the third bonding portion, an anti-deformation layer is provided on one side surface of the first substrate layer, and in the third bonding portion, the first adhesive layer is provided on the side surface of the anti-deformation layer away from the first substrate layer.

7. The battery cell according to claim 6, characterized in that, In the second bonding portion, the anti-deformation layer is provided on one side surface of the first substrate layer.

8. The battery cell according to claim 6, characterized in that, The thickness of the anti-deformation layer is no more than one-tenth of the thickness of the first substrate layer located at the first bonding portion.

9. The battery cell according to claim 1, characterized in that, The electrode and the separator are wound around each other multiple times to form the main body of the battery cell. The outermost electrode of the battery cell includes a tail section, which is attached and fixed to the main body of the battery cell by a second fixing member. The active material layer of the electrode has a main body region and a thickness reduction region with gradually decreasing thickness along the first direction pointing to the side where the electrode single piece is located. The cell body forms a main body portion based on the main body region and a thickness reduction portion based on the thickness reduction region. The second fixing member includes a fourth fitting portion attached to the main body and a fifth fitting portion attached to the thickness reduction portion, wherein the thickness of the fifth fitting portion gradually increases along the first direction.

10. The battery cell according to claim 9, characterized in that, The second fixing member includes a second substrate layer and a second adhesive layer located on the side of the second substrate layer facing the battery cell body; The thickness of the second substrate layer located in the fifth bonding portion gradually increases along the first direction.

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