Positive current collector, positive pole piece, battery and electric device

Abstract

The utility model belongs to the technical field of battery production and manufacturing, and particularly relates to an anode current collector which comprises a polymer layer, and at least one side of the polymer layer along the thickness direction of the anode current collector is provided with a first metal layer and a second metal layer; in the Y-axis direction, the first metal layer and the second metal layers are arranged in parallel, the second metal layers are arranged on the two sides of the first metal layer and located on the edge of the macromolecule layer, and the electric conductivity sigma1 of the first metal layer and the electric conductivity sigma2 of the second metal layers meet the relational expression that sigma2 is smaller than sigma1. According to the utility model, the second metal layer with smaller conductivity is arranged at the edge, so that the problem of lithium ion accumulation at the edge is solved, and the problem of lithium precipitation at the edge is relieved. In addition, the utility model also discloses a positive pole piece comprising the positive current collector, a battery and an electric device.

Description

Technical Field

[0001] The utility model belongs to the technical field of battery production and manufacturing, and specifically relates to a positive electrode current collector, a positive electrode sheet, a battery and an electrical 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] Among them, the battery cell pole piece is an important component of the battery. In the manufacturing process of the battery cell pole piece, due to the edge effect, the uniformity of the electrode material on the surface of the current collector is often difficult to ensure, which may lead to a mismatch in the surface density of the edge area, such as too high surface density at the edge of the positive electrode or too low density at the edge of the negative electrode. When the battery is charged and discharged, the inhomogeneity of the electrode material will cause the lithium ions to be unevenly distributed at the edge, resulting in the precipitation of metallic lithium. The precipitation of metallic lithium at the edge of the pole piece will cause the thickness of the head and tail sides of the battery to increase, which will have a certain impact on the performance and safety of the battery. For this reason, 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 address the deficiencies of the prior art and provide a positive electrode current collector which suppresses lithium deposition at the edge of the electrode by arranging a second metal layer with lower conductivity at the edge, thereby improving the performance of the battery.

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

[0006] A positive electrode current collector, comprising:

[0007] A polymer layer, wherein the polymer layer is provided with a first metal layer and a second metal layer on at least one side along the thickness direction of the positive electrode current collector;

[0008] In the Y-axis direction, the first metal layer and the second metal layer are arranged in parallel, the second metal layer is arranged on both sides of the first metal layer and located at the edge of the polymer layer, and the conductivity σ1 of the first metal layer and the conductivity σ2 of the second metal layer satisfy the relationship: σ2<σ1.

[0009] As an improvement of the positive electrode current collector described in the utility model, the conductivity σ1 of the first metal layer and the conductivity σ2 of the second metal layer satisfy the relationship: 2.5≤σ2 / σ1≤20.

[0010] As an improvement of the positive electrode current collector described in the utility model, the first metal layer or the second metal layer is at least one of metal aluminum, metal nickel, nickel-titanium alloy and stainless steel.

[0011] As an improvement of the positive electrode current collector of the utility model, the positive electrode current collector further includes a bonding layer, and the bonding layer is located between the polymer layer and the first metal layer and the second metal layer. The bonding layer can increase the bonding force between the polymer layer and the first metal layer and the second metal layer, and further can avoid the occurrence of wrinkles caused by the difference in elongation between the polymer layer and the first metal layer and the second metal layer.

[0012] As an improvement of the positive electrode current collector of the utility model, the conductivity of the first metal layer or the second metal layer is 1.20×10 6 S / m-3.75×10 7 S / m.

[0013] As an improvement of the positive electrode current collector described in the utility model, the thickness of the first metal layer and the second metal layer are the same, and the thickness of the first metal layer and the second metal layer are both 2μm-5μm.

[0014] As an improvement of the positive electrode current collector described in the utility model, the thickness D1 of the first metal layer or the second metal layer and the thickness D2 of the bonding layer satisfy the relationship: D1>D2.

[0015] As an improvement of the positive electrode current collector described in the utility model, the thickness D1 of the first metal layer or the second metal layer and the thickness D2 of the bonding layer satisfy the relationship: 25≤D1 / D2≤100.

[0016] As an improvement of the positive electrode current collector described in the utility model, the thickness of the polymer layer is 2 μm-4 μm.

[0017] As an improvement of the positive electrode current collector described in the utility model, the polymer layer is at least one of polypropylene, polyethylene terephthalate, polyethylene and cellulose-based film.

[0018] As an improvement of the positive electrode current collector of the utility model, the bonding layer is at least one of a polyurethane adhesive and a rubber adhesive.

[0019] The second object of the present utility model is to provide a positive electrode plate, comprising the positive electrode current collector as described above and active materials coated on both sides of the positive electrode current collector.

[0020] The third object of the present utility model is to provide a battery, comprising the positive electrode plate as described above.

[0021] A fourth object of the present utility model is to provide an electrical device comprising the positive electrode sheet as described above.

[0022] The beneficial effect of the utility model is that the positive electrode current collector of the utility model includes a polymer layer, and the polymer layer is provided with a first metal layer and a second metal layer along at least one side of the thickness direction of the positive electrode current collector; in the Y-axis direction, the first metal layer and the second metal layer are arranged in parallel, and the second metal layer is arranged on both sides of the first metal layer and located at the edge of the polymer layer, and the conductivity σ1 of the first metal layer and the conductivity σ2 of the second metal layer satisfy the relationship: σ2<σ1. The utility model arranges a second metal layer with a lower conductivity at the edge of the positive electrode current collector. Due to the poor conductivity of the second metal layer, the electron transfer rate of the second metal layer is relatively slow during the cycle of the battery cell, thereby reducing the kinetic capacity of the active material at the edge of the pole piece, effectively avoiding the occurrence of lithium plating, and thus improving the performance of the battery using the positive electrode current collector. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The features, advantages and technical effects of exemplary embodiments of the present invention will be described below with reference to the accompanying drawings.

[0024] Figure 1 It is a top view schematic diagram of the positive electrode current collector of the utility model.

[0025] Figure 2 It is a front view schematic diagram of the positive electrode current collector according to the first embodiment of the present invention.

[0026] Figure 3 It is a front view schematic diagram of the positive electrode current collector of the second embodiment of the present utility model.

[0027] The reference numerals are described as follows:

[0028] 1-Polymer layer;

[0029] 2- Adhesive layer;

[0030] 3- first metal layer;

[0031] 4- second metal layer;

[0032] T1-thickness direction of the positive electrode current collector; T2-Y-axis direction; T3-X-axis direction. DETAILED DESCRIPTION

[0033] 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.

[0034] 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.

[0035] 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.

[0036] 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.

[0037] 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. The term "plurality" as used herein refers to more than two (including two).

[0038] In the present application, battery cells may include lithium-ion secondary batteries, lithium-ion primary batteries, lithium-sulfur batteries, sodium-lithium-ion batteries, sodium-ion batteries or magnesium-ion batteries, etc., and the embodiments of the present application do not limit this. Battery cells may be cylindrical, flat, rectangular or other shapes, etc., and the embodiments of the present application do not limit this. Battery cells are generally divided into three types according to the packaging method: cylindrical battery cells, square battery cells and soft-pack battery cells, and the embodiments of the present application do not limit this.

[0039] The battery cell includes an electrode assembly and an electrolyte. The electrode assembly is composed of a positive electrode sheet, a negative electrode sheet and a separator. The battery cell mainly relies on the movement of metal ions between the positive electrode sheet and the negative electrode sheet to work. The positive electrode sheet includes a positive electrode collector and a positive electrode active material layer. The positive electrode active material layer is coated on the surface of the positive electrode collector. The positive electrode collector not coated with the positive electrode active material layer protrudes from the positive electrode collector coated with the positive electrode active material layer. The positive electrode collector not coated with the positive electrode active material layer serves as the positive electrode tab. Taking lithium-ion batteries as an example, 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 collector and a negative electrode active material layer. The negative electrode active material layer is coated on the surface of the negative electrode collector. The negative electrode collector not coated with the negative electrode active material layer protrudes from the negative electrode collector coated with the negative electrode active material layer. The negative electrode collector not coated with the negative electrode active material layer serves as the negative electrode tab. The material of the negative electrode collector can be copper, and the negative electrode active material can be carbon or silicon, etc. In order to ensure that a large current can pass 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) or PE (polyethylene). In addition, the electrode assembly can be a winding structure or a laminated structure, and the embodiments of the present application are not limited to this.

[0040] Lithium deposition at the edge of the battery cell pole piece refers to the phenomenon of metallic lithium deposition at the edge of the pole piece during the charge and discharge process of the battery, which will cause the thickness of the head and tail sides of the battery to increase, which will have a certain impact on the performance and safety of the battery. In order to reduce the negative impact of edge lithium deposition, reasonable optimization is required in the design phase. It is still difficult to maintain a uniform and consistent surface density during the coating process of the positive and negative electrodes, and the equipment requires high precision. The current method is to apply glue to the edge of the surface of the cathode active material layer, but as the cycle proceeds, there is always lithium ion overflow, and edge lithium deposition cannot be effectively avoided. In addition, applying glue to the edge of the pole piece will increase the thickness of the battery and lose energy density.

[0041] In view of this, the embodiment of the present application provides a technical solution, which slows down the escape rate of lithium ions at the edge and reduces the accumulation of lithium ions at the edge by setting a metal coating layer with lower conductivity at the edge of the current collector, thereby ensuring an excellent cycle life of the battery.

[0042] 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.

[0043] Implementation Method 1

[0044] like Figure 1-2 As shown, a positive electrode current collector comprises a polymer layer 1, and a first metal layer 3 and a second metal layer 4 are arranged on both sides of the polymer layer 1 along the thickness direction T1 of the positive electrode current collector;

[0045] In the Y-axis direction T2, the first metal layer 3 and the second metal layer 4 are arranged in parallel, the second metal layer 4 is arranged on both sides of the first metal layer 3 and located at the edge of the polymer layer 1, and the conductivity σ1 of the first metal layer 3 and the conductivity σ2 of the second metal layer 4 satisfy the relationship: σ2<σ1.

[0046] In this embodiment, since the conductivity of the second metal layer 4 is less than that of the first metal layer 3, and the second metal layer 3 is arranged at the edge of the positive electrode collector, the rate of lithium ion escape at the edge can be slowed down, the accumulation of lithium ions at the edge can be reduced, and the excellent cycle life of the battery using this positive electrode collector can be ensured.

[0047] It can be understood that in this embodiment, the first metal layer 3 and the second metal layer 4 are provided on both sides of the polymer layer 1. In some other embodiments, they can be provided on either side of the polymer layer 1, which can also achieve the purpose of slowing down the escape rate of edge lithium ions, but the effect is not as good as that of providing the bonding layer 2 on both sides.

[0048] Preferably, in this embodiment, the first metal layer 3 and the second metal layer 4 cover the surface of the positive electrode current collector along the X-axis direction T3, and the second metal layer 4 is respectively arranged on both sides of the first metal layer 3 at the edge of the positive electrode current collector. In some embodiments, the second metal layer 4 can also be arranged around the circumference of the first metal layer 3, which can better achieve the effect of preventing edge lithium deposition.

[0049] Preferably, the conductivity σ1 of the first metal layer 3 and the conductivity σ2 of the second metal layer 4 satisfy the relationship: 2.5≤σ2 / σ1≤20. As a preferred conductivity relationship between the first metal layer 3 and the second metal layer 4, it is possible to suppress the occurrence of edge lithium plating as much as possible without affecting the normal realization of the conductive function of the positive electrode current collector.

[0050] Preferably, the conductivity of the first metal layer 3 or the conductivity of the second metal layer 4 can be 1.20×10 6 S / m-3.75×10 7S / m; the first metal layer 3 or the second metal layer 4 is at least one of metal aluminum, metal nickel, nickel-titanium alloy and stainless steel.

[0051] Preferably, the first metal layer 3 and the second metal layer 4 have the same thickness, that is, the thickness of the first metal layer 3 and the second metal layer 4 are both 2 μm-5 μm; the thickness of the polymer layer 1 is 2 μm-4 μm.

[0052] Preferably, the polymer layer 1 is at least one of polypropylene, polyethylene terephthalate, polyethylene and cellulose-based films.

[0053] In order to better reflect the beneficial effects of the positive electrode current collector in this embodiment, a plurality of positive electrode current collectors are prepared according to the data in Table 1, and then the active material LiCoO2, the conductive agent acetylene black, the conductive carbon nanotubes, and the binder polyvinylidene fluoride (PVDF) are fully dispersed and evenly coated on a plurality of positive electrode current collectors in an N-methylpyrrolidone solvent system at a weight ratio of 97.6:0.5:0.6:1.3, and then cold-pressed and stripped to obtain positive electrode sheets; the negative electrode active material and the conductive agent (SP and CNT are mixed in a mass ratio of 0.45:0.05) are mixed in a weight ratio of 97.7:2.3 to obtain a negative electrode. The active material slurry is evenly coated on the negative electrode collector, and then cold pressed and slit to obtain the anode electrode sheet; the PE surface is coated with a ceramic mixture as an isolation membrane; ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), and propyl propionate (PP) are mixed in a volume ratio of 1.2:1:4:4, and then the fully dried lithium salt LiPF6 is dissolved in a mixed organic solvent at a ratio of 1 mol / L to prepare an electrolyte. Finally, the above-mentioned positive electrode sheet, isolation membrane, and negative electrode sheet are wound or stacked to produce a bare battery cell, which is then packaged and injected with an electrolyte to produce a finished lithium-ion battery.

[0054] The above batteries were placed in an environment of 25℃ / 45℃ and cycle tested according to the following method: charging mode: 3.6C CC to 4.25V, 2.8C CC to 4.35V, CV to 1.8C, 1.8CCC to 4.4V, CV to 1.5C, 1.5CCC to 4.5V, CV to 1.2C, 1.2C CC to 4.55V, CV to 0.26C; discharging mode: 0.7C DC to 3.0V, and the results in Table 2 were obtained.

[0055] Table 1

[0056]

[0057] Table 2

[0058]

[0059]

[0060] Among them, the capacity remaining ratio of 500 weeks = discharge capacity of the 500th week / discharge capacity of the 1st week * 100%; 500-week expansion rate = (thickness of the 500th week - initial half-electric thickness) / initial half-electric thickness * 100%; the test method for initial half-electric thickness is: charging at a constant current of 0.5C to 3.96V and constant voltage to 0.02C. All battery cell thicknesses are tested using 600PPG.

[0061] It can be concluded from the above data that a first metal layer 3 and a second metal layer 4 with different conductivities and a thickness of 2μm-5μm are arranged on the positive electrode current collector, and the conductivity of the second metal layer 4 located at the edge of the positive electrode current collector is less than the conductivity of the first metal layer 3, which can effectively suppress the edge lithium plating problem and enhance the cycle performance.

[0062] Implementation Method 2

[0063] like Figure 3 As shown, the present embodiment is different from the first embodiment in that the positive electrode current collector further includes a bonding layer 2, and the bonding layer 2 is located between the polymer layer 1 and the first metal layer 3 and the second metal layer 4. The bonding layer 2 can increase the bonding force between the polymer layer 1 and the first metal layer 3 and the second metal layer 4, and further can avoid the occurrence of wrinkles caused by the difference in elongation between the polymer layer 1 and the first metal layer 3 and the second metal layer 4.

[0064] Preferably, the thickness D1 of the first metal layer 3 or the second metal layer 4 and the thickness D2 of the bonding layer 2 satisfy the relationship: D1>D2, the thickness D1 of the first metal layer 3 or the second metal layer 4 and the thickness D2 of the bonding layer 2 satisfy the relationship: 25≤D1 / D2≤100, and the thickness of the polymer layer 1 is 2μm-4μm. The above thickness setting can avoid adding additional thickness, thereby ensuring the energy density of the battery using the positive electrode current collector while improving the battery cycle life.

[0065] Preferably, the adhesive layer 2 is at least one of a polyurethane adhesive and a rubber adhesive.

[0066] Implementation Method 3

[0067] A positive electrode sheet includes a positive electrode current collector of any one of the first embodiment or the second embodiment and an active material coated on both sides of the positive electrode current collector.

[0068] Implementation Method 4

[0069] A battery includes the positive electrode plate in the third embodiment, and the battery can be a lithium ion battery, a sodium ion battery, a magnesium ion battery, etc.

[0070] Implementation Method 5

[0071] An electrical device, including the battery in the fourth embodiment, wherein the electrical device can 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 can be a fuel vehicle, a gas vehicle or a new energy vehicle, and the new energy vehicle can 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 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, etc. The embodiments of the present application do not impose any special restrictions on the above-mentioned electrical devices.

[0072] 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 positive electrode current collector, characterized in that: include: A polymer layer (1), wherein the polymer layer (1) is provided with a first metal layer (3) and a second metal layer (4) on at least one side along a thickness direction (T1) of the positive electrode current collector; In the Y-axis direction (T2), the first metal layer (3) and the second metal layer (4) are arranged in parallel; The second metal layer (4) is arranged on both sides of the first metal layer (3) and is located at the edge of the polymer layer (1); the conductivity σ1 of the first metal layer (3) and the conductivity σ2 of the second metal layer (4) satisfy the relationship: σ2<σ1.

2. The positive electrode current collector according to claim 1, characterized in that: The electrical conductivity σ1 of the first metal layer (3) and the electrical conductivity σ2 of the second metal layer (4) satisfy the relationship: 2.5≤σ2 / σ1≤20.

3. The positive electrode current collector according to claim 1, characterized in that: The conductivity of the first metal layer (3) or the second metal layer (4) is 1.20×10 6 S / m-3.75×10 7 S / m.

4. The positive electrode current collector according to claim 1, characterized in that: It also comprises an adhesive layer (2), wherein the adhesive layer (2) is located between the polymer layer (1) and the first metal layer (3) and the second metal layer (4).

5. The positive electrode current collector according to claim 1, characterized in that: The thickness of the first metal layer (3) and the second metal layer (4) are the same, and the thickness of the first metal layer (3) and the second metal layer (4) are both 2 μm-5 μm; the thickness of the polymer layer (1) is 2 μm-4 μm.

6. The positive electrode current collector according to claim 4, characterized in that: The thickness D1 of the first metal layer (3) or the second metal layer (4) and the thickness D2 of the bonding layer (2) satisfy the relationship: D1>D2.

7. The positive electrode current collector according to claim 4, characterized in that: The thickness D1 of the first metal layer (3) or the second metal layer (4) and the thickness D2 of the bonding layer (2) satisfy the relationship: 25≤D1 / D2≤100.

8. A positive electrode sheet, characterized in that: The invention comprises the positive electrode current collector as claimed in any one of claims 1 to 7 and active materials coated on both sides of the positive electrode current collector.

9. A battery, characterized in that: Comprising the positive electrode sheet as described in claim 8.

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

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