A battery cell, a battery and an electric device

Abstract

The utility model belongs to the field of battery technology, and specifically relates to a battery cell formed by winding an anode electrode sheet, a separator and a cathode electrode sheet in sequence, wherein the first material layer is coated on the current collector corresponding to the straight area, and the second material layer is coated on the current collector corresponding to the corner area; wherein the length L of the second material layer in the length direction of the anode electrode sheet, the thickness W1 of the anode electrode sheet, the thickness W2 of the cathode electrode sheet, the thickness W3 of the separator and the number of winding turns N of the battery cell satisfy the following relationship: L=π×(NW1+(N‑1)W2+(N‑1)W3) 2 The particle diameter of the first material layer is smaller than the particle diameter of the second material layer. The utility model improves and solves the lithium deposition problem at the corner by limiting the length of the corner area and the lithium ion diffusion coefficient of the second material layer. In addition, the utility model also discloses a battery and an electrical device including the above-mentioned battery cell.

Description

Technical Field

[0001] The utility model belongs to the technical field of batteries, and in particular relates to an electric core, a battery and an electric device. Background Art

[0002] Nowadays, with the development of modern society and the enhancement of people's environmental awareness, more and more devices choose lithium-ion batteries as power sources, such as mobile phones, laptops, power tools and electric vehicles, which provides a broad space for the application and development of lithium-ion batteries.

[0003] In the field of power lithium batteries, wound cells are one of the common structures and can be used in various occasions with high energy density, high current discharge, long-term stability and durability. However, due to the structure of the wound cell, the interface at the corner of the cell is not as tight as that of the plane, resulting in a larger impedance at the corner, which makes it easier to deposit lithium at low temperatures and during the cycle. Therefore, it is urgent to propose a new technical solution to solve the above problems. Utility Model Content

[0004] One of the purposes of the utility model is to provide a battery cell in view of the deficiencies of the prior art, which improves the lithium deposition phenomenon in the corner area of ​​the wound battery cell by setting the length of the corner area and reducing the resistivity of the corner area.

[0005] In order to achieve the above purpose, the utility model adopts the following technical solutions:

[0006] A battery cell, formed by winding an anode electrode sheet, a separator and a cathode electrode sheet in sequence, wherein the battery cell forms a straight area and a corner area, wherein the anode electrode sheet comprises a current collector and an active material layer coated on the current collector, wherein the active material layer comprises a first material layer and a second material layer connected to each other, wherein the first material layer is coated on the current collector corresponding to the straight area, and the second material layer is coated on the current collector corresponding to the corner area;

[0007] The length L of the second material layer in the length direction of the anode electrode sheet, the thickness W1 of the anode electrode sheet, the thickness W2 of the cathode electrode sheet, the thickness W3 of the separator and the number of windings N of the battery cell satisfy the following relationship:

[0008] L = π × (NW1 + (N-1) W2 + (N-1) W3) 2 ; The particle diameter of the first material layer is smaller than the particle diameter of the second material layer.

[0009] In the present invention, the second material layer serves as an enhanced transmission layer. By being set to a material with a larger particle diameter than that of the first material layer, the lithium ion diffusion coefficient of the second material layer is greater than the lithium ion diffusion coefficient of the first material layer, thereby making the impedance of the second material layer smaller than the impedance of the first material layer.

[0010] In the present invention, by setting the length of the second material layer, that is, limiting the length of the corner area, and reducing the impedance of the second material layer coated on the corner area, the lithium deposition phenomenon in the corner area is improved.

[0011] As an improvement of the battery cell described in the utility model, the length of the second material layer in the length direction is set to 1mm-50mm, and gradually increases in the direction from the head of the anode pole piece to the tail of the anode pole piece.

[0012] As an improvement of the battery core described in the utility model, the length of the first material layer in the length direction is set to 10mm-2000mm.

[0013] As an improvement of the battery cell of the utility model, the lithium ion diffusion coefficients of the first material layer and the second material layer are both 10 -6 cm 2 / s-10 -5 cm 2 / s.

[0014] As an improvement of the battery core described in the utility model, the charging rate of the first material layer is smaller than the charging rate of the second material layer.

[0015] As an improvement of the battery cell described in the utility model, the charging rate of the second material layer is set to 0.5C-20C.

[0016] As an improvement of the battery cell described in the utility model, the conductivity of the first material layer is less than the conductivity of the second material layer. The setting of the above parameters further improves the ion transmission capacity of the second material layer, reduces the impedance of the second material layer, and further improves the lithium plating problem at the corners of the wound battery cell.

[0017] As an improvement to the battery cell described in the utility model, a transition layer is arranged between the first material layer and the second material layer, and the transition layer includes a first overlap body and a second overlap body connected to each other, the particle radius of the first overlap body is the same as the particle radius of the first material layer, and the particle radius of the second overlap body is the same as the particle radius of the second material layer. In the utility model, the first material layer and the second material layer use different materials, and a double-layer coating die is used for coating during coating. The transition layer is a mixed layer of the materials of the first material layer and the second material layer, which can avoid exposure of the current collector and improve the electrical performance and safety performance of the anode electrode.

[0018] The second purpose of the present utility model is to provide a battery, comprising the battery cell as described above.

[0019] The third object of the present utility model is to provide an electrical device comprising the battery as described above.

[0020] The beneficial effect of the utility model is that the battery cell of the utility model is formed by winding the anode electrode sheet, the separator and the cathode electrode sheet in sequence, and the battery cell forms a straight area and a corner area, the anode electrode sheet includes a current collector and an active material layer coated on the current collector, the active material layer includes a first material layer and a second material layer connected to each other, the first material layer is coated on the current collector corresponding to the straight area, and the second material layer is coated on the current collector corresponding to the corner area; wherein the length L of the second material layer in the length direction of the anode electrode sheet, the thickness W1 of the anode electrode sheet, the thickness W2 of the cathode electrode sheet, the thickness W3 of the separator and the number of winding turns N of the battery cell satisfy the following relationship: L=π×

[0021] (NW1+(N-1)W2+(N-1)W3) 2 The particle diameter of the first material layer is smaller than the particle diameter of the second material layer. The utility model improves the lithium deposition phenomenon at the corner by limiting the length of the corner area of ​​the wound battery cell and reducing the impedance of the coating material at the corner area. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The features, advantages and technical effects of exemplary embodiments of the present invention will be described below with reference to the accompanying drawings.

[0023] Figure 1 This is one of the structural schematic diagrams of the anode electrode in the utility model.

[0024] Figure 2 This is the second structural schematic diagram of the anode electrode in the utility model.

[0025] The reference numerals are described as follows:

[0026] 100- anode electrode;

[0027] 1-current collector;

[0028] 2-active material layer; 21-first material layer; 22-second material layer; 23-transition layer; 231-first overlapping body; 232-second overlapping body;

[0029] 3- Length direction. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0031] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as those commonly understood by technicians in the technical field of this application; the terms used in the specification of this application are only for the purpose of describing specific implementation methods and are not intended to limit this application; the terms "including" and "having" in the specification and claims of this application and the above-mentioned drawings and any variations thereof are intended to cover non-exclusive inclusions. The terms "first", "second", etc. in the specification and claims of this application or the above-mentioned drawings are used to distinguish different objects, rather than to describe a specific order or a primary and secondary relationship.

[0032] Reference to "embodiment" in this application means that a particular feature, structure or characteristic described in conjunction with the embodiment may be included in at least one embodiment of the present application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments.

[0033] In the description of this application, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", and "attached" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be the internal communication of two elements. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0034] In the embodiments of the present application, the same reference numerals represent the same components, and for the sake of brevity, detailed descriptions of the same components are omitted in different embodiments. It should be understood that the thickness, length, width and other dimensions of various components in the embodiments of the present application shown in the drawings, as well as the overall thickness, length, width and other dimensions of the integrated device are only exemplary descriptions and should not constitute any limitation to the present application.

[0035] The development of battery technology must take into account many design factors at the same time, such as energy density, cycle life, discharge capacity, charge and discharge rate and other performance parameters. In addition, the problem of battery lithium plating must also be considered.

[0036] When a lithium-ion battery is charging, Li + Deintercalation from the cathode and intercalation into the anode; however, when some abnormal conditions occur: insufficient lithium intercalation space at the anode, Li + The resistance of the anode is too large, Li + When an abnormality occurs, such as excessively fast deintercalation from the cathode and inability to intercalate the same amount into the anode, the Li + It can only obtain electrons on the surface of the anode, thus forming a silvery-white metallic lithium. Lithium precipitation not only reduces battery performance and significantly shortens cycle life, but also limits the fast-charging capacity of the battery, and may cause catastrophic consequences such as combustion and explosion. In batteries with a wound structure, the impedance at the corners of the battery cells becomes larger because the interface fit is not as tight as that of the plane, making it easier to precipitate lithium at low temperatures and during the cycle. In view of this, this embodiment improves the lithium precipitation phenomenon in the corner area of ​​the wound battery cell by setting a more reasonable corner area length and reducing the resistivity of the corner area.

[0037] The following is combined with Figures 1-2 The utility model is further described in detail with specific implementation modes, but is not intended to limit the utility model.

[0038] A battery cell is formed by winding an anode electrode sheet 100, a separator and a cathode electrode sheet in sequence, the battery cell forms a straight area and a corner area, the anode electrode sheet 100 includes a current collector 1 and an active material layer 2 coated on the current collector 1, the active material layer 2 includes a first material layer 21 and a second material layer 22 connected to each other, the first material layer 21 is coated on the current collector 1 corresponding to the straight area, and the second material layer 22 is coated on the current collector 1 corresponding to the corner area;

[0039] The length L of the second material layer 22 in the length direction 3 of the anode electrode sheet 100, the thickness W1 of the anode electrode sheet 100, the thickness W2 of the cathode electrode sheet, the thickness W3 of the diaphragm and the number of windings N of the battery cell satisfy the following relationship: L = π × (NW1 + (N-1) W2 + (N-1) W3) 2 ; The particle diameter of the first material layer 21 is smaller than the particle diameter of the second material layer 22.

[0040] In this embodiment, the material of the active material layer 2 is graphite. It is understood that the material selection of the active material layer 2 can be adjusted according to actual conditions and is not specifically set. The second material layer 22 is used as an enhanced transmission layer. It is set to a material with a larger particle diameter than the first material layer 21, so that the lithium ion diffusion coefficient of the second material layer 22 is greater than the lithium ion diffusion coefficient of the first material layer 21, and the impedance of the second material layer 22 is less than the impedance of the first material layer 21.

[0041] In this embodiment, by setting the length of the second material 22 layer, that is, limiting the length of the corner area, and reducing the impedance of the second material layer 22 coated on the corner area, the lithium deposition phenomenon in the corner area is improved.

[0042] Preferably, the length of the second material layer 22 in the length direction 3 is set to 1mm-50mm, and gradually increases from the head of the anode electrode sheet 100 to the tail of the anode electrode sheet 100, and the length of the first material layer 21 in the length direction 3 is set to 10mm-2000mm; the lithium ion diffusion coefficients of the first material layer 21 and the second material layer 22 are both 10 -6 cm 2 / s-10 -5 cm 2 / s; the charging rate of the first material layer 21 is less than the charging rate of the second material layer 22, and the charging rate of the second material layer 22 is set to 0.5C-20C; the conductivity of the first material layer 21 is less than the conductivity of the second material layer 22. The setting of the above parameters further ensures that the ion transmission capacity of the corner area is higher than that of the straight area, reduces the impedance at the corner, and thus improves the lithium deposition problem at the corner.

[0043] In order to better illustrate the feasibility of this embodiment, a method for making an anode electrode sheet 100 is provided, comprising the following steps: stirring two negative electrode active material graphites with different particle diameters, wherein the material of the first material layer 21 is 1.5C graphite, and the material of the second material layer 22 is 5C graphite; dividing the straight area and the corner area in the current collector 1 according to the above relationship, and using a double-layer die head to coat the two graphite materials in the straight area and the corner area respectively to obtain a semi-finished electrode sheet, and at the same time, a transition layer 23 is provided between the first material layer 21 and the second material layer 22, and the transition layer 23 is a mixed layer of the two graphite materials, and the transition layer 23 It includes a first overlap body 231 and a second overlap body 232 connected to each other, the particle radius of the first overlap body 231 is the same as the particle radius of the first material layer 21, the particle radius of the second overlap body 232 is the same as the particle radius of the second material layer 22, and the thickness difference between the transition layer 23 and the first material layer 21 and the second material layer 22 does not exceed 5um, which can prevent the collector 1 from being exposed without affecting the subsequent rolling of the anode electrode 100; the semi-finished electrode sheet after rolling and coating is obtained to obtain the anode electrode 100, at which time the thickness of the first material layer 21, the second material layer 22 and the transition layer 23 are the same.

[0044] It is understandable that the selection of the above graphite can be adjusted according to actual conditions, as long as the particle diameter of the first material layer 21 is smaller than the particle diameter of the second material layer 22, and no specific setting is made.

[0045] Battery

[0046] A battery comprises the battery cell as described above, and the battery may be a lithium ion battery, a sodium ion battery, a magnesium ion battery, etc.

[0047] Electrical devices

[0048] An electrical device, comprising a battery as described above, wherein the electrical device may be a vehicle, a mobile phone, a portable device, a laptop computer, a ship, a spacecraft, an electric toy, an electric tool, etc. The vehicle may be a fuel vehicle, a gas vehicle or a new energy vehicle, and the new energy vehicle may be a pure electric vehicle, a hybrid vehicle or an extended-range vehicle, 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 console, an electric car 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 assembly electric tool and an electric tool for railways, such as an electric drill, an electric grinder, an electric wrench, an electric screwdriver, an electric hammer, an impact drill, a concrete vibrator and an electric planer, etc. The embodiments of the present application do not impose any special restrictions on the above-mentioned electrical devices.

[0049] According to the disclosure and teaching of the above description, the technicians in the field of the utility model can also change and modify the above implementation. Therefore, the utility model is not limited to the above specific implementation, and any obvious improvement, replacement or modification made by the technicians in this field on the basis of the utility model belongs to the protection scope of the utility model. In addition, although some specific terms are used in this specification, these terms are only for the convenience of explanation and do not constitute any limitation to the utility model.

Claims

1. A battery cell, characterized in that: The battery cell is formed by winding an anode electrode sheet (100), a separator and a cathode electrode sheet in sequence, and the battery cell forms a straight region and a corner region, the anode electrode sheet (100) comprises a current collector (1) and an active material layer (2) coated on the current collector (1), the active material layer (2) comprises a first material layer (21) and a second material layer (22) connected to each other, the first material layer (21) is coated on the current collector (1) corresponding to the straight region, and the second material layer (22) is coated on the current collector (1) corresponding to the corner region; The length L of the second material layer (22) in the length direction (3) of the anode electrode sheet (100), the thickness W1 of the anode electrode sheet (100), the thickness W2 of the cathode electrode sheet, the thickness W3 of the separator and the number of windings N of the battery cell satisfy the relationship: L=π×(NW1+(N-1)W2+(N-1)W3) 2 ; The particle diameter of the first material layer (21) is smaller than the particle diameter of the second material layer (22).

2. The battery cell according to claim 1, characterized in that: The length of the second material layer (22) in the length direction (3) is set to 1 mm-50 mm, and gradually increases in the direction from the head of the anode pole piece (100) to the tail of the anode pole piece (100).

3. The battery cell according to claim 1, characterized in that: The length of the first material layer (21) in the length direction (3) is set to 10 mm-2000 mm.

4. The battery cell according to claim 1, characterized in that: The lithium ion diffusion coefficients of the first material layer (21) and the second material layer (22) are both 10 -6 -10 -5 cm 2 / s.

5. The battery cell according to claim 1, characterized in that: The charging rate of the first material layer (21) is smaller than the charging rate of the second material layer (22).

6. The battery cell according to claim 5, characterized in that: The charging rate of the second material layer (22) is set to 0.5C-20C.

7. The battery cell according to claim 1, characterized in that: The electrical conductivity of the first material layer (21) is lower than the electrical conductivity of the second material layer (22).

8. The battery cell according to claim 1, characterized in that: A transition layer (23) is provided between the first material layer (21) and the second material layer (22); the transition layer (23) comprises a first overlapping body (231) and a second overlapping body (232) which are connected to each other; the particle radius of the first overlapping body (231) is the same as the particle radius of the first material layer (21); and the particle radius of the second overlapping body (232) is the same as the particle radius of the second material layer (22).

9. A battery, characterized in that: Comprising the battery cell as described in any one of claims 1 to 8.

10. An electrical device, characterized in that: Comprising the battery as claimed in claim 9.

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