Battery cell, secondary battery and electric device

Abstract

The utility model belongs to the technical field of secondary batteries, and particularly relates to a battery cell, a secondary battery and an electric device. The battery cell comprises a battery cell body, a foil tab and a metal tab, the foil tab is provided with a first section and a second section, the first section is connected with the top of the battery cell body, the second section is connected with the metal tab to form a welding area, a protective layer is arranged between the first section and the welding area, the length of the foil tab along the x-axis is L1, and the length of the metal tab along the x-axis is L2. The length of the protective layer along the x axis is L2, and L1 and L2 meet the relational expression that L2 = L1 + a, and a is larger than or equal to 3mm and smaller than or equal to 6mm. Compared with the prior art, the battery cell has the advantages that the unwelded foil tabs can be prevented from being stabbed and cracked by the metal tabs, the risk of preventing the tabs from being stabbed by the outside world is greatly reduced, the safety of the battery is improved, and normal charging and discharging of the battery cell and the overall thickness of the battery cell are not influenced.

Description

Technical Field

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

[0002] Secondary batteries generally include battery cells, electrolytes, and battery cases. The positive and negative tabs are connected to the positive and negative poles and foil tabs of the top cover through metal tabs to form a battery path. The battery case is then sealed, and electrolyte is injected. After electrochemical activation, a secondary battery is finally obtained. In the structure of secondary batteries, a reasonable battery cell structure can assemble a battery with better performance.

[0003] In the prior art, the positive electrode foil of the current collector used in the battery is mainly aluminum foil, and the negative electrode foil is copper foil; in the welding of the tabs of the laminated battery, the exposed tab foil of the positive and negative electrodes that are not covered is first cut, and then the aluminum tab or copper-plated nickel tab is welded to the metal tab by ultrasonic welding or laser welding. After the tab welding is completed, the root of the tab is usually close to the unwelded foil tab at the diaphragm. Since the metal tab and the weld print area are relatively hard, when the battery is subjected to post-processing, such as packaging, liquid injection, formation, etc., when the tab is subjected to external force, the root of the metal tab will "poke" in the direction of the unwelded foil tab. The softer foil tab is at risk of being "cut and cracked" by the root of the tab, especially the outermost foil tab, which is closest to the root of the tab; the breakage of the foil tab may directly affect the battery's electrical performance and reduce the battery welding rate.

[0004] Therefore, under the current technical background, it is urgent to develop a battery cell that can protect the foil tab from being punctured to solve the above problems. Utility Model Content

[0005] The purpose of the utility model is to provide a battery cell in view of the deficiencies of the prior art, so as to solve the problem in the prior art that when an external force acts on the root of the metal pole ear, the metal pole ear "pokes" toward the top of the battery cell body, thereby causing the unwelded foil pole ear to be punctured and cracked.

[0006] In order to achieve the above purpose, the utility model adopts the following technical solutions:

[0007] A battery cell comprises a battery cell body, a foil tab and a metal tab, wherein the foil tab has a first section and a second section, the first section is connected to the top of the battery cell body, the second section is connected to the metal tab to form a welding area, a protective layer is arranged between the first section and the welding area, the length of the foil tab along the x-axis is L1, the length of the protective layer along the x-axis is L2, and L1 and L2 satisfy the relationship: L2=L1+a, 3mm≤a≤6mm.

[0008] Preferably, the protective layer includes a main material, a flame retardant and a plasticizer. The main material is at least one of polyurethane, rubber, nitrile rubber, silicone rubber and silicone resin; the flame retardant is at least one of ammonium polyphosphate, phosphate ester and aluminum tripolyphosphate; the plasticizer is dioctyl phthalate. The main material is a matrix masterbatch with a mass ratio of 90%-96%; the flame retardant is an additive, which functions to enhance the flame retardancy of the material, with a mass ratio of 1%-4%; the mass ratio of the plasticizer is 0.5%-1.5%, which functions to increase the flexibility of the molecular chain.

[0009] The protective layer is mainly formed by cold pressing the masterbatch, auxiliary agents and additives into a mold after melt extrusion through a blending method. The protective layer has certain impact resistance, puncture resistance, ductility and chemical corrosion resistance. The raw materials of the protective layer are simple, the preparation method is simple, and it can be mass-produced without adding a lot of additional production costs. In addition, the protective layer has high temperature resistance, and it will not lose its function when the temperature rises during the use of the battery cell; it also has flame retardancy. When the temperature of the tab is too high, resulting in thermal runaway, the protective layer as a flame retardant material can protect the tab to a certain extent.

[0010] Preferably, the protective layer is fixed with adhesive tape or adhesive layer. Glue can be applied on the surface of the protective layer and then adhered to the first section or the second section; the protective layer can also be fixed on the tab with insulating adhesive tape; the protective layer does not affect the energy density of the battery, and as a flexible material, when the foil tab is squeezed by the root of the metal tab, it acts as a buffer to buffer the external force and protect the foil tab.

[0011] Preferably, the shape of the protective layer is rectangular. Generally speaking, the shape of the tab is rectangular, and the protective layer acts between the first section and the welding area, and the surface of this area is rectangular. Therefore, the use of a rectangular protective layer in the present application can better fit the actual use of the battery cell and effectively protect the foil tab from being cut off or damaged by external forces.

[0012] Preferably, the distance between the protective layer and the top of the battery body is 1 to 6 mm. A gap is left between the protective layer and the top of the battery body, which does not affect subsequent steps such as battery packaging and the energy density of the secondary battery.

[0013] Preferably, the thickness of the protective layer is 0.3-1.2 mm. The thickness of the protective layer should not be too thick, as it will affect the thickness of the subsequent packaging of the battery cell and the energy density of the battery. If the thickness of the protective layer is too thin, it may not be able to play the role of a buffer layer, and the protective layer itself is easily broken under the action of external force, and cannot protect the foil tab.

[0014] Preferably, the elongation at break of the protective layer is 120%-240%.

[0015] The protective layer will have a large uniaxial elongation when resisting impact, will not break brittlely, and can play a buffering role when acting on the ear.

[0016] Preferably, the tensile strength of the protective layer is 4.0-8.0 MPa.

[0017] Preferably, the shape of the welding area is at least one of polygonal, circular and elliptical. The shape of the welding area is not particularly limited, as long as it can connect the foil tab and the metal tab, including but not limited to square, rectangular, irregular polygon or dot.

[0018] The present invention also provides a secondary battery, comprising the above-mentioned battery cell.

[0019] The present invention also provides an electrical device, comprising the secondary battery.

[0020] The beneficial effect of the utility model is that the battery cell provided by the utility model comprises a battery cell body, a foil pole ear and a metal pole ear, the foil pole ear has a first section and a second section, the first section is connected to the top of the battery cell body, the second section is connected to the metal pole ear to form a welding area, and a protective layer is arranged between the first section and the welding area. Compared with the prior art, the battery cell can prevent the unwelded foil pole ear from being punctured and cracked, greatly reducing the risk of the pole ear being punctured by the outside, and at the same time does not affect the normal charging and discharging of the pole ear and the overall thickness of the battery cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic diagram of the cross-sectional structure of a battery cell in the y-axis direction in one embodiment of the utility model.

[0022] Figure 2 It is a top view of a battery cell in one embodiment of the utility model.

[0023] Among them, 1. battery cell body; 2. foil tab; 21. first section; 22. second section; 3. metal tab; 4. welding area; 5. protective layer. DETAILED DESCRIPTION

[0024] The present invention and its beneficial effects will be further described in detail below in conjunction with specific implementations and the accompanying drawings of the specification, but the specific implementations of the present invention are not limited thereto.

[0025] In the description of the present utility model, unless otherwise clearly specified and limited, the term "including" is an open term and should be interpreted as "including but not limited to". 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.

[0026] In the description of this application, it should be noted that, unless otherwise clearly specified and limited, the terms "installation" and "connection" 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 components. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0027] like Figure 1 As shown, a battery cell is provided, including a battery cell body 1, a foil tab 2 and a metal tab 3, the foil tab 2 has a first section 21 and a second section 22, the first section 21 is connected to the top of the battery cell body 1, the second section 22 is connected to the metal tab 3 to form a welding area 4, a protective layer 5 is arranged between the first section 21 and the welding area 4, the length of the foil tab 2 along the x-axis is L1, the length of the protective layer 5 along the x-axis is L2, L1 and L2 satisfy the relationship: L2 = L1 + a, 3mm ≤ a ≤ 6mm. The direction of the x-axis can be Figure 1 Learn that Figure 1 The x-axis, y-axis, and z-axis are perpendicular to each other.

[0028] In one embodiment of the present application, the foil tab 2 includes a positive electrode foil tab and a negative electrode foil tab, wherein the positive electrode foil tab and the negative electrode foil tab can be arranged on the same side of the battery cell (single-sided tab) or on both sides of the battery cell (double-sided tab).

[0029] In one embodiment of the present application, the protective layer 5 includes a main material, a flame retardant and a plasticizer. The main material is at least one of polyurethane, rubber, nitrile rubber, silicone rubber, and silicone resin; the flame retardant is at least one of ammonium polyphosphate, phosphate ester, and aluminum tripolyphosphate; and the plasticizer is dioctyl phthalate. The main material is a matrix masterbatch with a mass ratio of 90%-96%; the flame retardant is an additive, which is used to enhance the flame retardancy of the material, with a mass ratio of 1%-4%; the mass ratio of the plasticizer is 0.5%-1.5%, which is used to increase the flexibility of the molecular chain.

[0030] The protective layer 5 is mainly formed by cold pressing the masterbatch, auxiliary agent and additives into the mold after melt extrusion by blending method. The protective layer 5 has certain impact resistance, puncture resistance, ductility and chemical corrosion resistance. The raw materials of the protective layer are simple, the preparation method is simple, and it can be mass-produced without adding a lot of additional production costs. In addition, the protective layer 5 has high temperature resistance, and will not lose its function when the temperature rises during the use of the battery cell; it also has flame retardancy. When the temperature of the tab is too high, resulting in thermal runaway, the protective layer 5 as a flame retardant material can protect the tab to a certain extent.

[0031] In one embodiment of the present application, the protective layer 5 is fixed by adhesive tape or adhesive layer. The protective layer 5 can be coated with adhesive and then adhered to the first section 21 or the second section 22; the protective layer 5 can also be fixed to the tab by insulating adhesive tape; the protective layer 5 does not affect the energy density of the battery, and as a flexible material, when the foil tab 2 is squeezed by the root of the metal tab 3, it acts as a buffer to buffer the external force and protect the foil tab 2.

[0032] In one embodiment of the present application, the shape of the protective layer 5 is rectangular. Generally speaking, the shape of the tab is rectangular, and the protective layer 5 acts between the first section 21 and the welding area 4, and the surface of this area is rectangular. Therefore, the use of a rectangular shape for the protective layer 5 of the present application can better fit the actual use of the battery cell 1 and effectively protect the foil tab 2 from being cut off or damaged by external forces.

[0033] In one embodiment of the present application, the distance between the protective layer 5 and the top 1 of the battery body is 1 to 6 mm. A gap is left between the protective layer 5 and the top of the battery body 1, which does not affect subsequent steps such as battery packaging and does not affect the energy density of the secondary battery.

[0034] In one embodiment of the present application, the thickness of the protective layer 5 is 0.3-1.2 mm. The thickness of the protective layer 5 should not be too thick, because it will affect the thickness of the subsequent packaging of the battery cell and the energy density of the battery. If the thickness of the protective layer 5 is too thin, it may not be able to play the role of a buffer layer, and the protective layer 5 itself is easily broken under the action of external force, and cannot protect the foil tab 2.

[0035] In one embodiment of the present application, the elongation at break of the protective layer 5 is 120%-240%.

[0036] The protective layer 5 has a large unilateral elongation when resisting impact and will not break brittlely, and can play a buffering role when acting in the pole ear.

[0037] In one embodiment of the present application, the tensile strength of the protective layer 5 is 4.0-8.0 MPa.

[0038] In one embodiment of the present application, the shape of the welding area 4 is at least one of a polygon, a circle and an ellipse. The shape of the welding area 4 is not particularly limited, as long as the shape that can connect the foil tab 2 and the metal tab 3 is possible, including but not limited to a square, a rectangle, an irregular polygon or a dot.

[0039] The utility model also provides a secondary battery, including a shell and the above-mentioned battery cell. The secondary battery can be a lithium ion battery, a sodium ion battery, or any other battery having a battery cell and a top cover assembly structure. Taking a lithium ion battery as an example, the material of the positive electrode current collector can be aluminum, and the positive electrode active material can be lithium cobalt oxide, lithium iron phosphate, ternary lithium, or lithium manganese oxide, etc. The negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer, the negative electrode active material layer is coated on the surface of the negative electrode current collector, the negative electrode current collector not coated with the negative electrode active material layer protrudes from the negative electrode current collector coated with the negative electrode active material layer, and the negative electrode current collector not coated with the negative electrode active material layer serves as a negative electrode tab. The material of the negative electrode current collector can be copper, and the negative electrode active material can be carbon or silicon, etc. In order to ensure that a large current passes without melting, the number of positive electrode tabs is multiple and stacked together, and the number of negative electrode tabs is multiple and stacked together. The material of the isolation film can be PP (polypropylene, polypropylene) or PE (polyethylene, polyethylene), etc. In addition, the electrode assembly may be a wound structure or a laminated structure, but the embodiments of the present application are not limited thereto.

[0040] The utility model also provides an electrical device, including the above-mentioned secondary battery, wherein the electrical device can be a mobile phone, a portable device, a laptop computer, a battery car, an electric car, a ship, a spacecraft, an electric toy and an electric tool, etc. For example, 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 a railway electric tool, 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.

[0041] 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: It includes a battery cell body, a foil pole ear and a metal pole ear, the foil pole ear has a first section and a second section, the first section is connected to the top of the battery cell body, the second section is connected to the metal pole ear to form a welding area, a protective layer is arranged between the first section and the welding area, the length of the foil pole ear along the x-axis is L1, the length of the protective layer along the x-axis is L2, and L1 and L2 satisfy the relationship: L2=L1+a, 3mm≤a≤6mm.

2. The battery cell according to claim 1, characterized in that: The protective layer is fixed by adhesive tape or adhesive layer.

3. The battery cell according to claim 1, characterized in that: The shape of the protection layer is rectangular.

4. The battery cell according to claim 1, characterized in that: The distance between the protective layer and the top of the battery cell body is 1 to 6 mm.

5. The battery cell according to claim 1, characterized in that: The thickness of the protective layer is 0.3-1.2 mm.

6. The battery cell according to claim 1, characterized in that: The breaking elongation of the protective layer is 120%-240%.

7. The battery cell according to claim 1, characterized in that: The tensile strength of the protective layer is 4.0-8.0 MPa.

8. The battery cell according to claim 1, characterized in that: The shape of the welding area is at least one of a polygon, a circle and an ellipse.

9. A secondary battery, characterized in that: A battery cell comprising the battery cell according to any one of claims 1 to 8.

10. An electrical device, characterized in that: A secondary battery comprising the secondary battery according to claim 9.

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