Lithium ion battery

Abstract

The utility model relates to a lithium ion battery. The lithium ion battery comprises a positive plate and a negative plate, the positive plate comprises a positive current collector, the positive current collector is provided with a positive active material layer and a positive tab, the negative plate comprises a negative current collector, and the negative current collector is provided with a negative active material layer and a negative tab; insulating coatings are arranged on a welding region of the positive tab and the positive current collector on the positive plate and on a projection plane of the positive plate on the negative tab, an empty foil region is arranged at the end part of the positive current collector, and the insulating coatings are arranged at the junction of the empty foil region and the positive active material layer; and the insulating coatings are respectively arranged on a welding area of the negative tab and the negative current collector on the negative plate and on a projection plane of the negative plate on the positive tab. According to the scheme, the thickness of the battery cell can be reduced, and the energy density of the battery cell is improved.

Description

Technical Field

[0001] This application relates to the technical field of batteries, and particularly to a lithium-ion battery. Background Art

[0002] Commercial 3C consumer lithium-ion batteries are applied to devices such as mobile phones, tablets, power banks, and laptop computers, and generally have two types: wound type and laminated structure. In related technologies, tapes are attached to the overhang areas at the head, tail, and tab positions of the electrode sheets of the wound type battery cells to prevent lithium plating caused by uneven areal density at the head and tail of the battery cells during charge and discharge, thus avoiding safety problems.

[0003] However, the taping method in related technologies increases the thickness of the battery cell, affects the energy density of the battery cell, and reduces the product competitiveness; the adhesive layer of the tape (i.e., glue) has poor antioxidant properties under high voltage (>4.4V) and high temperature (>60°C), and is prone to react with the electrolyte, resulting in an increase in by-products at the taped positions of the battery cell. After high-temperature storage, the battery cell is prone to side deformation; at the same time, the taping method requires the setting of a taping mechanism, which increases costs and reduces the profit of the product. Utility Model Content

[0004] To solve or partially solve the problems existing in related technologies, this application provides a lithium-ion battery, which can reduce the thickness of the battery cell and improve the energy density of the battery cell.

[0005] This application provides a lithium-ion battery, including: a positive electrode sheet and a negative electrode sheet. The positive electrode sheet includes a positive current collector, on which a positive active material layer and a positive tab are provided. The negative electrode sheet includes a negative current collector, on which a negative active material layer and a negative tab are provided;

[0006] Insulating coatings are provided on the positive electrode sheet at the welding area between the positive tab and the positive current collector, and at the projection plane of the positive electrode sheet on the negative tab. An empty foil area is provided at the end of the positive current collector, and the insulating coating is provided at the junction of the empty foil area and the positive active material layer;

[0007] Insulating coatings are respectively provided on the negative electrode sheet at the welding area between the negative tab and the negative current collector, and at the projection plane of the negative electrode sheet on the positive tab.

[0008] Further, insulating coatings are provided on both surfaces of the positive electrode sheet on the opposite sides of the welding area between the positive tab and the positive current collector;

[0009] Insulating coatings are provided on both surfaces of the negative electrode sheet on the opposite sides of the welding area between the negative tab and the negative current collector.

[0010] Further, the width of the insulating coating covering the positive electrode active material layer is 1-3 mm.

[0011] Further, the areal density of the insulating coating is 0.1-10 g / m2, and the thickness is 0.5-10 μm.

[0012] Further, the positive tab is a central tab, and the positive tab is located in the middle of the positive current collector in the length direction.

[0013] Further, the negative tab is a central tab, and the negative tab is located in the middle of the negative current collector in the length direction.

[0014] Further, the empty foil areas are respectively provided at both ends of the positive current collector in the length direction.

[0015] Further, the width of the insulating coating on the positive electrode sheet in the welding area between the positive tab and the positive current collector is not less than the width of the positive tab;

[0016] The width of the insulating coating on the negative electrode sheet in the welding area between the negative tab and the negative current collector is not less than the width of the negative tab.

[0017] Further, the positive current collector is made of aluminum foil, and the negative current collector is made of copper foil or aluminum foil.

[0018] Further, the above-mentioned lithium-ion battery further includes a housing, an electrolyte and a separator. The positive electrode sheet, the negative electrode sheet and the separator are wound to form an electrode group, and the electrode group and the electrolyte are both located in the housing.

[0019] The technical solution provided by this application may include the following beneficial effects: By replacing the tape with an insulating coating, the insulating coating is thinner than the tape, which can reduce the thickness of the battery cell and improve the energy density of the battery cell; the insulating coating has good electronic and ionic insulation properties, and does not react with the electrolyte. The insulating coating also has good thermal stability and corrosion resistance and is not easy to fall off, which can improve the side deformation of the battery cell after storage; by replacing the tape with an insulating coating, the taping process can be reduced, the working efficiency can be improved, and the cost can be reduced.

[0020] It should be understood that the above general description and the following detailed description are only exemplary and explanatory, and cannot limit this application. Description of the Drawings

[0021] By describing the exemplary embodiments of the present application in more detail in conjunction with the drawings, the above and other objects, features and advantages of the present application will become more obvious. Among them, in the exemplary embodiments of the present application, the same reference numerals generally represent the same components.

[0022] Figure 1 It is a side view of the positive electrode sheet shown in the first embodiment of the present application;

[0023] Figure 2 It is a front view of the positive electrode sheet shown in the first embodiment of the present application;

[0024] Figure 3 It is a rear view of the positive electrode sheet shown in the first embodiment of the present application;

[0025] Figure 4 It is a side view of the negative electrode sheet shown in the first embodiment of the present application;

[0026] Figure 5 It is a front view of the negative electrode sheet shown in the first embodiment of the present application;

[0027] Figure 6 It is a rear view of the negative electrode sheet shown in the first embodiment of the present application;

[0028] Figure 7 It is a graph of the insulation layer thickness versus the ED benefit percentage shown in the first embodiment of the present application;

[0029] Figure 8 It is a side view of the positive electrode sheet shown in the second embodiment of the present application;

[0030] Figure 9 It is a front view of the positive electrode sheet shown in the second embodiment of the present application;

[0031] Figure 10 It is a rear view of the positive electrode sheet shown in the second embodiment of the present application;

[0032] Figure 11 It is a side view of the negative electrode sheet shown in the second embodiment of the present application;

[0033] Figure 12 It is a front view of the negative electrode sheet shown in the second embodiment of the present application;

[0034] Figure 13 It is a rear view of the negative electrode sheet shown in the second embodiment of the present application.

[0035] Reference numerals:

[0036] 1 - Positive current collector, 2 - Positive active material layer, 3 - Positive tab, 4 - Negative current collector, 5 - Negative active material layer, 6 - Negative tab, 71 - Insulating coating, 72 - Insulating coating, 73 - Insulating coating, 74 - Insulating coating, 75 - Insulating coating, 76 - Insulating coating, 77 - Insulating coating, 78 - Insulating coating, 79 - Insulating coating, 710 - Insulating coating. Detailed implementation manners

[0037] Embodiments of the present application will be described in more detail below with reference to the accompanying drawings. Although the embodiments of the present application are shown in the drawings, it should be understood that the present application can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided to make the present application more thorough and complete, and to fully convey the scope of the present application to those skilled in the art.

[0038] It should be understood that although the terms "first", "second", "third", etc. may be used in the present application to describe various information, such information should not be limited to these terms. These terms are only used to distinguish information of the same type from each other. For example, without departing from the scope of the present application, the first information may also be referred to as the second information, and similarly, the second information may also be referred to as the first information. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present application, the meaning of "a plurality" is two or more unless otherwise specifically defined.

[0039] In the description of the present application, it should be understood that the orientation or positional relationship indicated by the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation to the present application.

[0040] Unless otherwise clearly specified and defined, the terms "mounted", "connected", "connected to", "fixed", etc. should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection or integrated; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium, and it may be the communication inside two elements or the interaction relationship between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to specific circumstances.

[0041] Embodiment 1

[0042] As Figures 1 to 6 shown, Embodiment 1 of the present application provides a lithium-ion battery, including a positive electrode sheet and a negative electrode sheet. The positive electrode sheet includes a positive electrode current collector 1, a positive electrode active material layer 2 and a positive electrode tab 3 are provided on the positive electrode current collector 1. The negative electrode sheet includes a negative electrode current collector 4, a negative electrode active material layer 5 and a negative electrode tab 6 are provided on the negative electrode current collector 4.

[0043] As Figures 1 to 3As shown in the figure, insulating coatings are provided on the positive electrode sheet at the welding area between the positive electrode tab 3 and the positive electrode current collector 1, and at the projection surface of the positive electrode sheet at the negative electrode tab 6. An empty foil area is provided at the end of the positive electrode current collector 1, and an insulating coating is provided at the junction of the empty foil area and the positive electrode active material layer 2. Among them, insulating coatings 71 and 72 are provided on the positive electrode sheet at the area where the positive electrode tab 3 is bonded and welded to the positive electrode current collector 1, insulating coatings 73 and 74 are provided at the projection position corresponding to the negative electrode tab 6 on the positive electrode sheet, and insulating coatings 75 and 76 are provided at the end position of the positive electrode active material layer 2 located in the empty foil area of the positive electrode current collector 1. The empty foil area of the positive electrode current collector 1 is the area where the positive electrode active material layer 2 is not coated. The projection surface of the positive electrode sheet at the negative electrode tab 6 refers to the position on the positive electrode sheet corresponding to the negative electrode tab 6 on the adjacent negative electrode sheet.

[0044] As Figures 4 to 6 shown, insulating coatings are respectively provided on the negative electrode sheet at the welding area between the negative electrode tab 6 and the negative electrode current collector 4, and at the projection surface of the negative electrode sheet at the positive electrode tab 3. Among them, insulating coatings 79 and 710 are provided on the negative electrode sheet at the area where the negative electrode tab 6 is bonded and welded to the negative electrode current collector 4, and insulating coatings 77 and 78 are provided at the projection surface of the negative electrode sheet at the positive electrode tab 3. The projection surface of the negative electrode sheet at the positive electrode tab 3 refers to the position on the negative electrode sheet corresponding to the positive electrode tab 3 on the adjacent positive electrode sheet.

[0045] Based on the above solution, by replacing the adhesive tape with an insulating coating, the thickness of the insulating coating is relatively thin compared to the tape, which can reduce the thickness of the battery cell and improve the energy density of the battery cell; the insulating coating has good electronic and ionic insulation properties and does not react with the electrolyte. The insulating coating also has good thermal stability and corrosion resistance and is not easily detached, which can improve the deformation of the side of the battery cell after storage; by replacing the adhesive tape with an insulating coating, the taping process can be reduced, the work efficiency can be improved, and the cost can be reduced.

[0046] In some embodiments, insulating coatings are provided on both opposite surfaces of the positive electrode sheet at the welding area between the positive electrode tab 3 and the positive electrode current collector 1, that is, insulating coatings 71 and 72, to prevent the burrs of the positive electrode tab 3 from piercing the separator and contacting the negative electrode to cause a short circuit; insulating coatings are provided on both opposite surfaces of the negative electrode sheet at the welding area between the negative electrode tab 6 and the negative electrode current collector 4, that is, insulating coatings 79 and 710, to prevent the burrs of the negative electrode tab 6 from piercing the separator and contacting the positive electrode to cause a short circuit.

[0047] In some embodiments, the width of the insulating coating covering the positive electrode active material layer 2 is 1-3 mm. Specifically, the insulating coating covers the end position of the positive electrode active material layer 2 to prevent uneven thinning of the tail of the positive electrode sheet from causing lithium deposition. The insulating coating has good electronic insulation properties and does not allow lithium ions to pass through.

[0048] In some embodiments, the surface density of the insulating coating is 0.1-10 g / m2, and the thickness is 0.5-10 μm, which is thinner than the thickness of the tape.

[0049] In some embodiments, the positive tab 3 is a central tab, and the positive tab 3 is located in the middle of the positive current collector 1 in the length direction.

[0050] In some embodiments, the negative tab 6 is a central tab, and the negative tab 6 is located in the middle of the negative current collector 4 in the length direction.

[0051] In some embodiments, the width of the insulating coating in the welding area between the positive tab 3 and the positive current collector 1 on the positive electrode sheet is not less than the width of the positive tab 3. In this way, the insulating coating completely covers the positive tab 3 to prevent the burrs of the positive tab 3 from piercing the separator and contacting the negative electrode to cause a short circuit. The width of the insulating coating in the welding area between the negative tab 6 and the negative current collector 4 on the negative electrode sheet is not less than the width of the negative tab 6. In this way, the insulating coating completely covers the negative tab 6 to prevent the burrs of the negative tab 6 from piercing the separator and contacting the positive electrode to cause a short circuit.

[0052] In some embodiments, the positive current collector 1 is made of aluminum foil, and the negative current collector 4 is made of copper foil or aluminum foil.

[0053] In some embodiments, the lithium-ion battery further includes a housing, an electrolyte, and a separator. The positive electrode sheet, the negative electrode sheet, and the separator are wound to form an electrode assembly, and the electrode assembly and the electrolyte are both located in the housing.

[0054] In some embodiments, the main components of the insulating coating are inorganic fillers, binders, and dispersants, and the insulating coating has good electrical insulation properties.

[0055] In some embodiments, the inorganic filler is one or more of calcium carbonate, calcium oxide, manganese oxide, titanium oxide, zinc oxide, vanadium pentoxide, and chromium oxide. The inorganic filler can improve the insulation performance of the coating.

[0056] In some embodiments, the binder is one or more of cyanoacrylate, polyvinyl acetal, polycarbonate, nylon, polysulfone, polyimide, and polyurethane. The binder is used to increase the adhesion performance of the insulating coating and prevent the powder from falling off under external force, thereby improving the safety performance of the battery.

[0057] In some embodiments, the dispersant is one or more of styrene, perchloroethylene, trichloroethylene, ethylene glycol ether, and triethanolamine. The dispersant makes the inorganic filler and the binder evenly mixed.

[0058] In some embodiments, by mass fraction, the proportion of the inorganic filler is 70%-80%, the proportion of the binder is 5%-10%, and the proportion of the dispersant is 10%-20%.

[0059] The insulating coating has good electronic and ionic insulation capabilities and does not react with the electrolyte. The insulating coating also has good thermal stability and corrosion resistance and is not easily detached.

[0060] Specifically, insulating coatings 71 and 72 are located at the positive tab 3, with a width of 15 - 25 mm and a length of 25 - 35 mm, for preventing the burrs of the positive tab 3 from piercing through the separator and contacting the negative electrode to cause a short circuit; insulating coatings 73 and 74 face the negative tabs 6 on both sides, with a width of 15 - 25 mm and a length of 25 - 35 mm, capable of preventing the burrs of the negative tab 6 from piercing through the separator to cause a short circuit, and at the same time avoiding the lithium ions in the positive electrode sheet from escaping to the position of the negative tab 6 during charge and discharge to cause lithium plating; insulating coatings 75 and 76 are used to prevent lithium plating caused by uneven thinning at the tail of the positive electrode sheet. The width of the insulating coatings 75 and 76 covering the positive active material layer 2 is 1 - 3 mm, and the width of the insulating coatings 75 and 76 is 15 - 20 mm, and their length is equal to the width of the positive electrode sheet.

[0061] Insulating coatings 77 and 78 correspond to the positions of the positive tabs 3 on both sides, mainly for preventing the burrs of the positive tab 3 from piercing through the separator to cause a short circuit, with a width of 10 - 20 mm and a length of 20 - 30 mm. Insulating coatings 79 and 710 are located at the negative tab 6, with a width of 15 - 25 mm and a length of 25 - 35 mm, which can prevent the burrs of the negative tab 6 from piercing through the separator and contacting the positive electrode to cause a short circuit.

[0062] Compared with the prior art, the lithium - ion battery of this embodiment uses an insulating layer instead of a tape, and the thickness of the insulating layer is thinner than that of the tape, so that the thickness of the battery cell can be reduced, the energy density (abbreviated as ED) of the battery cell can be increased by 0.2% - 1.35%, as Figure 7 shown, which is the curve graph of the insulating layer thickness and the ED gain percentage shown in Embodiment 1 of this application.

[0063] Embodiment 2

[0064] As Figures 8 to 13 shown, Embodiment 2 of this application provides a lithium - ion battery. The difference between this embodiment and Embodiment 1 above is that: empty foil areas are respectively provided at both ends in the length direction of the positive current collector 1. Insulating coatings 71 and 72 are provided on both sides of the positive electrode sheet at the position where the positive tab 3 is attached to the positive current collector 1. Insulating coatings 73 and 74 are provided at the starting position of the positive active material layer 2. Insulating coatings 75 and 76 are provided at the ending position of the positive active material layer 2; insulating coatings 77 and 78 are provided at the position where the negative tab 6 is attached to the negative current collector 4 on the negative electrode sheet, and insulating coatings 79 and 710 are respectively provided at the positions corresponding to the positive tab 3 on the negative electrode sheet.

[0065] The insulating coatings 71 and 72 are used to prevent the burrs of the positive tab 3 from piercing the separator and contacting the negative electrode to cause a short circuit. The insulating coatings 73 and 74 are used to prevent lithium deposition caused by uneven thinning of the head of the positive electrode sheet. The insulating coatings 75 and 76 are used to prevent lithium deposition caused by uneven thinning of the tail of the positive electrode sheet. The widths of the insulating coatings 71 to 76 are 10 to 20 mm, and the lengths are equal to the width of the positive electrode sheet. The insulating coatings 77 and 78 are used to prevent the burrs of the negative tab 6 from piercing the separator and contacting the positive electrode to cause a short circuit. The insulating coatings 79 and 710 are used to play a safety protection role to prevent the burrs at the blank foil cutting position of the head of the positive electrode sheet from piercing the separator and directly contacting the negative electrode to cause a short circuit. The widths of the insulating coatings 77 to 710 are 10 to 20 mm, and the lengths are equal to the width of the negative electrode sheet.

[0066] The solutions of the present application have been described in detail with reference to the accompanying drawings above. In the above embodiments, the descriptions of the respective embodiments have their own emphases. For the parts not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments. Those skilled in the art should also be aware that the actions and modules involved in the specification are not necessarily essential to the present application. In addition, it can be understood that the steps in the method embodiments of the present application can be adjusted, combined, and deleted according to actual needs, and the modules in the device embodiments of the present application can be combined, divided, and deleted according to actual needs.

[0067] The various embodiments of the present application have been described above. The above description is exemplary and not exhaustive, and is not limited to the disclosed embodiments. Many modifications and variations are obvious to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The choice of terms used herein is intended to best explain the principles of the embodiments, the practical application, or the improvement of the technology in the market, or to enable other ordinary skilled in the art in the technical field to understand the embodiments disclosed herein.

Claims

1. A lithium-ion battery, characterized in that, Comprising: A positive electrode sheet and a negative electrode sheet. The positive electrode sheet includes a positive electrode current collector (1), a positive electrode active material layer (2) and a positive electrode tab (3) are provided on the positive electrode current collector (1). The negative electrode sheet includes a negative electrode current collector (4), a negative electrode active material layer (5) and a negative electrode tab (6) are provided on the negative electrode current collector (4); Insulating coatings are provided on the positive electrode sheet at the welding area between the positive electrode tab (3) and the positive electrode current collector (1), and at the projection surface of the positive electrode sheet on the negative electrode tab (6). An empty foil area is provided at the end of the positive electrode current collector (1), and the insulating coating is provided at the junction of the empty foil area and the positive electrode active material layer (2); Insulating coatings are respectively provided on the negative electrode sheet at the welding area between the negative electrode tab (6) and the negative electrode current collector (4), and at the projection surface of the negative electrode sheet on the positive electrode tab (3).

2. The lithium-ion battery according to claim 1, wherein: Insulating coatings are provided on both surfaces of the positive electrode sheet on opposite sides of the welding area between the positive electrode tab (3) and the positive electrode current collector (1); Insulating coatings are provided on both surfaces of the negative electrode sheet on opposite sides of the welding area between the negative electrode tab (6) and the negative electrode current collector (4).

3. The lithium-ion battery according to claim 1, wherein: The width of the insulating coating covering the positive electrode active material layer (2) is 1-3 mm.

4. The lithium-ion battery according to claim 1, wherein: The surface density of the insulating coating is 0.1-10 g / m2, and the thickness is 0.5-10 um.

5. The lithium-ion battery according to claim 1, wherein: The positive electrode tab (3) is a central tab, and the positive electrode tab (3) is located in the middle of the length direction of the positive electrode current collector (1).

6. The lithium-ion battery according to claim 1, wherein: The negative electrode tab (6) is a central tab, and the negative electrode tab (6) is located in the middle of the length direction of the negative electrode current collector (4).

7. The lithium-ion battery according to claim 1, wherein: Empty foil areas are respectively provided at both ends of the positive electrode current collector (1) in the length direction.

8. The lithium-ion battery according to claim 1, wherein: The width of the insulating coating on the positive electrode sheet at the welding area between the positive electrode tab (3) and the positive electrode current collector (1) is not less than the width of the positive electrode tab (3); The width of the insulating coating on the negative electrode sheet at the welding area between the negative electrode tab (6) and the negative electrode current collector (4) is not less than the width of the negative electrode tab (6).

9. The lithium-ion battery according to claim 1, wherein: The positive electrode current collector (1) is made of aluminum foil, and the negative electrode current collector (4) is made of copper foil or aluminum foil.

10. The lithium-ion battery according to claim 1, wherein: It further includes a housing, an electrolyte and a separator. The positive electrode sheet, the negative electrode sheet and the separator are wound to form an electrode assembly, and the electrode assembly and the electrolyte are both located in the housing.

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