Secondary battery and electric device

Abstract

This application discloses a secondary battery and an electrical device. By using a support layer and a conductive layer disposed on at least one surface of the support layer as the negative electrode current collector, and controlling the length of the support layer and the conductive layer, the separator and the support layer are partially bonded, which can improve the stability of the negative electrode current collector, increase the energy density of the secondary electrode, and solve the problem of separator wrinkles caused by the release of separator tension during the stacking process, thereby improving the cycle performance of the secondary battery.

Description

Technical Field

[0001] This application relates to the field of battery technology, specifically to a secondary battery and an electrical device. Background Technology

[0002] With the rapid development of electric vehicles and mobile electronic devices, people have increasingly higher demands for the energy density, safety, and cycle performance of rechargeable batteries. Among these, energy density and cycle performance are important parameters for evaluating the performance of rechargeable batteries.

[0003] Lithium metal has the lowest relative atomic mass (6.94) and the lowest standard electrode potential (-3.045V) of all metallic elements, with a theoretical specific capacity of 3860 mAh / g. Therefore, using lithium metal as the negative electrode in batteries, combined with high-energy-density positive electrode materials, can significantly improve the battery's energy density (>400Wh / kg) and operating voltage (>4.5V). Lithium metal batteries typically use lithium-coated copper strips as the positive electrode, with Cu foil as the current collector having a density of 8.96 g / cm³. 3 The thickness is typically 5-10µm, which accounts for a large proportion of the mass of lithium metal batteries. This means that the energy density advantage of the battery is not maximized.

[0004] Therefore, this application is submitted. Summary of the Invention

[0005] The purpose of this application is to overcome the shortcomings of the existing technology and provide a secondary battery and power device, wherein the secondary electrode has a high energy density and can solve the problem of membrane wrinkles caused by membrane tension release during the stacking process, thereby improving the cycle performance of the secondary battery.

[0006] To achieve the above objectives, a first aspect of this application provides a secondary battery, including a negative electrode, a positive electrode, and a separator, wherein the separator is disposed between the positive electrode and the negative electrode, and the negative electrode includes a negative current collector and a negative electrode material layer disposed on at least one surface of the negative current collector.

[0007] The negative electrode current collector includes a support layer and a conductive layer disposed on at least one surface of the support layer;

[0008] The length of the support layer is A1, the length of the conductive layer is A2, D = A1 - A2, 1cm ≤ D ≤ 4cm;

[0009] The diaphragm and the support layer are bonded together at least in part.

[0010] As an embodiment of this application, the diaphragm includes a body segment located on the surface of the negative electrode material layer, an adhesive segment located on the surface of the support layer, and a transition segment connecting the body segment and the adhesive segment. The length of the adhesive segment is D2, 0.3cm≤D2≤1.7cm.

[0011] As an embodiment of this application, the distance between the adhesive segment and the conductive layer is D1, where 0.2cm≤D1≤0.3cm.

[0012] As an implementation of this application, D1 and D2 satisfy: 2≤D2 / D1≤6.5.

[0013] As an implementation scheme of this application, at least one of the following (a) to (c) is satisfied:

[0014] (a) The thickness of the negative electrode material layer is 15–50 μm;

[0015] (b) The thickness of the conductive layer is 1–4 μm;

[0016] (c) The thickness of the support layer is 6 to 15 μm.

[0017] As an embodiment of this application, the total thickness of the negative electrode material layer and the conductive layer is H1, and H1 and D1 satisfy: 0.01≤H1 / D1≤0.025.

[0018] As an embodiment of this application, the negative electrode material layer includes at least one of lithium strip and lithium-based alloy, wherein the lithium-based alloy includes at least one of Li-Ag, Li-Al, Li-B, Li-Mg, Li-Au, Li-Na, Li-Si, Li-Sn, Li-Zn, Li-Ba, Li-Bi, Li-C, Li-Ca, Li-Ge, Li-Cs, Li-Ga, Li-K, Li-Pb, Li-P, Li-Sb, Li-B-Mg, and Li-Mg-Si.

[0019] As an embodiment of this application, a protective layer is also included, which is located on at least one surface of the negative electrode material layer, and the thickness of the protective layer is 10 to 300 nm.

[0020] As an embodiment of this application, the support layer is at least one of a polymer or fiberglass.

[0021] As an embodiment of this application, the conductive layer includes at least one of conductive metal and conductive non-metal. The conductive metal includes at least one of Au, Ag, Al, Cu, Ni, Au-based alloy, Ag-based alloy, Al-based alloy, Cu-based alloy, and Ni-based alloy. The conductive non-metal includes at least one of graphite, acetylene black, carbon black, graphene, carbon fiber, and carbon nanotube.

[0022] A third aspect of this application provides an electrical device including the aforementioned secondary battery, wherein the secondary battery serves as the power supply for the electrical device.

[0023] The beneficial effects of this application are as follows: by using a support layer and a conductive layer disposed on at least one surface of the support layer as the negative electrode current collector, and controlling the length of the support layer and the conductive layer, the separator and the support layer are partially bonded, which can improve the stability of the negative electrode current collector, increase the energy density of the secondary electrode, and solve the problem of separator wrinkles caused by the release of separator tension during the stacking process, thereby improving the cycle performance of the secondary battery. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the structure of the secondary battery described in this application. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0026] In this application, the technical features described in an open-ended manner include both closed technical solutions consisting of the listed features and open technical solutions that include the listed features.

[0027] In this application, numerical ranges are referred to as continuous unless otherwise specified, and include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to integers, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be merged. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.

[0028] like Figure 1As shown, this application embodiment provides a secondary battery, including a negative electrode, a positive electrode, and a separator 1. The separator is disposed between the positive electrode and the negative electrode. The negative electrode includes a negative current collector and a negative electrode material layer 2 disposed on at least one surface of the negative current collector. The negative current collector includes a support layer 3 and a conductive layer 4 disposed on at least one surface of the support layer. The length of the support layer is A1, the length of the conductive layer is A2, D = A1 - A2, 1cm ≤ D ≤ 4cm, for example, it can be 1cm, 1.5cm, 2cm, 2.5cm, 3cm, 3.5cm, 4cm or any two of these values. At least a portion of the separator and the support layer are bonded together.

[0029] This application uses a support layer and a conductive layer disposed on at least one surface of the support layer as the negative electrode current collector. By controlling the length of the support layer and the conductive layer, the stability of the negative electrode current collector can be improved, the volumetric energy density of the secondary electrode can be increased, and the problem of membrane wrinkles caused by membrane tension release during the stacking process can be solved, thereby improving the cycle performance of the secondary battery.

[0030] In this application, the negative electrode current collector includes two opposing first and second surfaces in the thickness direction. The negative electrode material layer is disposed on at least one surface of the negative electrode current collector. Those skilled in the art should understand that the negative electrode material layer can be disposed on its first surface, or on its second surface, or simultaneously on both the first and second surfaces.

[0031] In this application, the support layer includes two opposing first and second surfaces in the thickness direction, and a conductive layer is disposed on at least one surface of the support layer. Those skilled in the art should understand that the conductive layer can be disposed on its first surface, or on its second surface, or simultaneously on both the first and second surfaces.

[0032] In one embodiment, the two ends of the diaphragm and the support layer are bonded together.

[0033] In one embodiment, the diaphragm includes a body segment 11 located on the surface of the negative electrode material layer, an adhesive segment 13 located on the surface of the support layer, and a transition segment 12 connecting the body segment and the adhesive segment. The length of the adhesive segment is D2, 0.3cm≤D2≤1.7cm, for example, it can be 0.3cm, 0.5cm, 0.8cm, 1.0cm, 1.2cm, 1.5cm, 1.7cm or any two of these values.

[0034] This application creatively sets the separator into a main section, a bonding section, and a transition section, and controls the length of the bonding section to ensure that the secondary battery has sufficient bonding strength during cycling and will not break, while ensuring the volumetric energy density of the secondary battery.

[0035] It should be noted that the bonding section is formed by hot pressing the diaphragm and the support layer.

[0036] In one embodiment, the distance between the adhesive segment and the conductive layer is D1, where 0.2cm ≤ D1 ≤ 0.3cm, and for example, it can be a range of 0.2cm, 0.22cm, 0.25cm, 0.28cm, 0.3cm, or any two of these values.

[0037] This application controls the distance between the bonding section and the conductive layer, so that it will not affect the negative electrode and positive electrode during hot pressing, and has a certain protective effect on the negative electrode and positive electrode. At the same time, it enables the secondary battery of this application to meet the lightweight design and reduce the internal resistance of the secondary battery. During the lithium deposition process, the negative electrode surface expands in volume, and the support layer and bonding section deform, applying a compressive stress to the negative electrode surface. Under this force, uniform lithium deposition is achieved.

[0038] In one embodiment, the adhesive segment is bonded to the diaphragm.

[0039] The distance between the adhesive segment and the conductive layer refers to the shortest distance from the adhesive segment to the conductive layer.

[0040] In one implementation, D1 and D2 satisfy: 2≤D2 / D1≤6.5, for example, they can be 2, 2.5, 3, 4, 4.5, 5, 5.5, 6, 6.5 or a range of any two of these values.

[0041] This application controls the ratio of D1 to D2 to ensure the stability of the secondary battery during the hot pressing process of forming the bonding section, while improving the volumetric energy density of the secondary electrode and ensuring sufficient bonding strength of the secondary battery during cycling.

[0042] In one embodiment, the length A1 of the support layer is 91–155 mm.

[0043] In one embodiment, the length A2 of the conductive layer is 90-150 mm.

[0044] In one embodiment, the thickness of the negative electrode material layer is 15–50 μm, for example, it can be a range of 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, or any two of these values. By controlling the thickness of the negative electrode material layer within this range, the energy density of the secondary battery can be guaranteed, while improving the cycle performance of the secondary battery.

[0045] In one embodiment, the thickness of the conductive layer is 1–4 μm, for example, it can be a range of 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, or any two of these values. By controlling the thickness of the conductive layer, the secondary battery can achieve both lightweight design and high energy density.

[0046] In one embodiment, the thickness of the support layer is 6–15 μm, for example, it can be a range of 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, or any two of these values. By controlling the thickness of the support layer within this range, compressive stress on the negative electrode surface can be provided to inhibit scale formation, thereby achieving uniform lithium deposition.

[0047] In one embodiment, the Young's modulus of the support layer is ≥1 GPa, which ensures that the support layer and the separator adhere to each other during the cycle of the secondary battery, jointly providing compressive stress on the negative electrode surface and preventing breakage.

[0048] In one embodiment, the Young's modulus of the support layer is 1 GPa to 6 GPa, for example, it can be a range of 1 GPa, 2 GPa, 3 GPa, 4 GPa, 5 GPa, 6 GPa or any two of these values.

[0049] The Young's modulus of the support layer can be determined using methods known in the art.

[0050] For example, the Young's modulus test method of the support layer is as follows: cut the support layer into a sample of 15mm×200mm, measure the thickness of the sample as 1μm with a micrometer, and perform a tensile test using a high-speed rail tensile testing machine at normal temperature and pressure (25℃, 0.1MPa). Set the initial position so that the sample between the clamps is 50mm long, the tensile speed is 50mm / min, and record the load Q (N) at which the sample is stretched to break and the equipment displacement z (mm). Then the stress ξ (GPa) = Q / (15×l) and the strain ξ = z / 50. Plot the stress-strain curve and take the initial linear region curve. The slope of this curve is the Young's modulus.

[0051] In one embodiment, the diaphragm has a transverse tensile strength ≥500MPa, which ensures that the diaphragm will not undergo plastic deformation during the cycle.

[0052] In one embodiment, the transverse tensile strength of the diaphragm is 500 MPa to 1000 MPa, for example, it can be 500 MPa, 600 MPa, 700 MPa, 800 MPa, 900 MPa, 1000 MPa or any two of these values.

[0053] The transverse tensile strength of the diaphragm can be determined using methods known in the art.

[0054] For example, the method for testing the transverse tensile strength of the diaphragm is as follows:

[0055] Uniaxial tensile tests (with load applied along the central axis) were performed using a tensile strength testing machine. The specimens were stretched uniformly at a specified rate, and the tensile force and elongation were recorded. Material parameters such as stress-strain curves, yield strength, tensile strength, and elongation at break were derived. The tensile strength was calculated by determining the ratio of the tensile force at fracture to the fracture area when the diaphragm fractured.

[0056] In one embodiment, the bonding force between the adhesive segment and the support layer is ≥20 N / m.

[0057] In one embodiment, the bonding force between the adhesive segment and the support layer is 20 N / m to 30 N / m, for example, it can be 20 N / m, 22 N / m, 25 N / m, 28 N / m, 30 N / m or any two of these values.

[0058] The bonding force between the bonding segment and the support layer can be determined using methods known in the art.

[0059] For example, the bonding force test method between the bonding segment and the support layer is as follows: bonding force: refers to the bonding force between the diaphragm and the support layer, and the measurement method is: using a tensile testing machine to clamp the diaphragm and peel it off at 180°.

[0060] In one embodiment, the total thickness of the negative electrode material layer and the conductive layer is H1, and H1 and D1 satisfy: 0.01≤H1 / D1≤0.025, for example, it can be 0.01, 0.015, 0.02, 0.025 or any two of these values. By controlling the ratio of H1 and D1, the stability of the secondary battery is improved, and the volumetric energy density of the secondary electrode is increased.

[0061] In one embodiment, the negative electrode material layer includes at least one of lithium strip and lithium-based alloy. The lithium-based alloy includes at least one of Li-Ag, Li-Al, Li-B, Li-Mg, Li-Au, Li-Na, Li-Si, Li-Sn, Li-Zn, Li-Ba, Li-Bi, Li-C, Li-Ca, Li-Ge, Li-Cs, Li-Ga, Li-K, Li-Pb, Li-P, Li-Sb, Li-B-Mg, and Li-Mg-Si. By using the lithium-based alloy, the deposition morphology of lithium can be further improved to enhance the battery cycle performance.

[0062] In one embodiment, a protective layer is further included, located on at least one surface of the negative electrode material layer. The thickness of the protective layer is 10–300 nm, for example, it can be a range of 10 nm, 20 nm, 50 nm, 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, or any two of these values. The protective layer can prevent direct contact between the negative electrode lithium and the electrolyte, reduce side reactions, and improve cycle performance.

[0063] In one embodiment, the protective layer comprises at least one of a polymer, LiF, and Li3N.

[0064] In one embodiment, the support layer is at least one of a polymer or fiberglass.

[0065] In one embodiment, the thickness of the diaphragm is 10-15 μm, for example, it can be 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm or any two of these values.

[0066] In one embodiment, the membrane is a polymer.

[0067] The polymers mentioned in this application include at least one of polyethylene, polystyrene, polyvinyl chloride, polyether, polyester, polyamide, polyurethane, polysulfide rubber, polyethylene terephthalate, polytetrafluoroethylene, and polyethersulfone.

[0068] In one embodiment, the conductive layer includes at least one of a conductive metal and a conductive non-metal. The conductive metal includes at least one of Au, Ag, Al, Cu, Ni, Au-based alloys, Ag-based alloys, Al-based alloys, Cu-based alloys, and Ni-based alloys. The conductive non-metal includes at least one of graphite, acetylene black, carbon black, graphene, carbon fiber, and carbon nanotubes.

[0069] In one embodiment, the positive electrode sheet includes a positive current collector 5 and a positive electrode material layer 6 disposed on at least one surface of the positive current collector.

[0070] In this application, there is no particular limitation on the type of positive electrode current collector; it can be any known material suitable for use as a positive electrode current collector. In one embodiment, the positive electrode current collector includes metallic materials such as aluminum, stainless steel, nickel plating, titanium, and tantalum, as well as carbon materials such as carbon cloth and carbon paper. In one embodiment, the positive electrode current collector is a metallic material. In one embodiment, the positive electrode current collector is aluminum.

[0071] There are no particular restrictions on the form of the positive electrode current collector. When the positive electrode current collector is a metallic material, it can be in the form of metal foil, metal cylinder, metal strip, metal plate, metal foil, metal mesh, stamped metal, foamed metal, etc. When the positive electrode current collector is a carbon material, it can be in the form of carbon plate, carbon film, carbon cylinder, etc.

[0072] In one embodiment, the positive electrode material layer includes a positive electrode material, which may be selected from sodium-iron composite oxides, sodium-cobalt composite oxides, sodium-manganese composite oxides, sodium-nickel composite oxides, sodium-nickel-titanium composite oxides, sodium-nickel-manganese composite oxides, sodium-iron-manganese composite oxides, sodium-nickel-cobalt-manganese composite oxides, sodium-iron phosphate compounds, sodium-manganese phosphate compounds, sodium-cobalt phosphate compounds, etc. However, this application is not limited to these materials, and other conventional materials that can be used as negative electrode active materials in batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more.

[0073] In one embodiment, the positive electrode material layer further includes a conductive agent and a binder.

[0074] In one embodiment, the secondary battery further includes a negative electrode sheet, the negative electrode sheet including a negative current collector and a negative active material layer disposed on at least one surface of the negative current collector, the negative active material layer including a negative active material.

[0075] In one embodiment, the negative electrode sheet and the positive electrode sheet are stacked together.

[0076] In one embodiment, there is no limitation on the type of conductive agent mentioned in this application, and any known conductive agent may be used.

[0077] In one embodiment, the conductive agent includes at least one of carbon materials such as acetylene black, needle coke, carbon nanotubes, and graphene.

[0078] In one embodiment, there is no limitation on the type of adhesive mentioned in this application, and any known positive electrode adhesive can be used.

[0079] In one embodiment, the adhesive includes at least one of polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, polyimide, aromatic polyamide, cellulose, nitrocellulose, styrene-butadiene rubber, nitrile rubber, fluororubber, isoprene rubber, polybutadiene rubber, ethylene-propylene rubber, styrene-butadiene-styrene block copolymer or its hydrogenation, ethylene-propylene-diene terpolymer, styrene-ethylene-butadiene-ethylene copolymer, styrene-isoprene-styrene block copolymer, syndiotactic-1,2-polybutadiene, polyvinyl acetate, ethylene-vinyl acetate copolymer, propylene-α-olefin copolymer, polyvinylidene fluoride, polytetrafluoroethylene, fluorinated polyvinylidene fluoride, and polytetrafluoroethylene-ethylene copolymer.

[0080] In one embodiment, the secondary battery may include an outer packaging that can be used to encapsulate the aforementioned electrode assembly and electrolyte.

[0081] In one embodiment, the outer packaging of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging of the secondary battery can also be a soft pack, such as a pouch. The material of the soft pack can be plastic; examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0082] In some embodiments, the type of electrolyte is not specifically limited. The electrolyte includes an electrolyte salt and an organic solvent, and the specific types of the electrolyte salt and organic solvent are not specifically limited and can be selected according to actual needs. The electrolyte may also include additives, and the type of additives is not particularly limited. These additives can be film-forming additives for the positive and / or negative electrodes, or additives that can improve certain battery performance, such as additives that improve the battery's high or low temperature performance.

[0083] This application does not impose any particular restrictions on the shape of the secondary battery; it can be cylindrical, square, or any other arbitrary shape.

[0084] One embodiment of this application provides an electrical device including the secondary battery described above, wherein the secondary battery serves as the power supply for the electrical device.

[0085] For example, the aforementioned electrical devices may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but are not limited thereto.

[0086] The present application is further illustrated below with specific embodiments:

[0087] Examples 1-11, Comparative Examples 1-3

[0088] A secondary battery, wherein the method for preparing the secondary battery includes the following steps:

[0089] (1) Preparation of negative electrode sheet

[0090] S1. Provide a support layer, wherein the support layer is PET, its Young's modulus is 2 GPa, its thickness is 10 μm, and its length is 102-107 mm.

[0091] S2. A copper metal thin film is deposited under vacuum conditions using a vapor deposition method. The copper vapor forms a composite film on the surface of the PET film substrate. Finally, a conductive layer is formed on the two surfaces in the thickness direction of the support layer. The thickness of the conductive layer is 1-8 μm and the length is 102 mm. The conductive layer and the support layer together form a negative electrode current collector.

[0092] S3. A pure lithium strip with a thickness of 10-60 μm is bonded to two surfaces in the thickness direction of the negative electrode current collector by roll forming, wherein the length of the pure lithium strip corresponds to the length of the conductive layer.

[0093] (2) Preparation of positive electrode sheet

[0094] The ternary active material Ni96, conductive carbon black (Super P), and polyvinylidene fluoride (PVDF) were mixed in a weight ratio of 97:1.5:1.5. N-methylpyrrolidone (NMP) was added as a solvent to prepare a slurry with a solid content of 0.75%, and the mixture was stirred evenly. The slurry was then uniformly coated onto the positive electrode current collector aluminum foil and dried at 90°C to obtain the positive electrode sheet with an areal capacity of 4.5 mAh / cm². 2 After coating, cold pressing was performed, achieving a compaction density of 3.4 g / cm³. 3 Then, the electrode sheet is cut into 98mm×98mm sizes for later use.

[0095] (3) Preparation of electrolyte

[0096] In a dry argon atmosphere, the organic solvent ethylene glycol dimethyl ether (DME) and 1,1,2,2-tetrafluoro-3-(1,1,2,2-tetrafluoroethoxy)propane (TTE) were first mixed at a mass ratio of DME:TTE = 1:3. Then, lithium bis(fluorosulfonyl)imide (LiFSI) was added to the organic solvent to dissolve and mix thoroughly to obtain an electrolyte with a lithium salt concentration of 4.5M: 4.5M LiFSI in 25% DME + 75% TTE.

[0097] (4) Assembly

[0098] The ends of the separator and support layer are hot-pressed together for a length of [(D﹣D1) / 2] cm (D1 is set to 0.1 cm, and D2 is the maximum hot-pressing length). The electrodes are then stacked, with the positive and negative electrodes on either side of the separator, and a separator membrane between the electrodes. After stacking, tabs are welded on. The battery is then placed in an aluminum-plastic film, and after top-side sealing, electrolyte injection, and encapsulation, a lithium metal laminated battery is finally obtained.

[0099] Examples 12-26

[0100] A secondary battery, wherein the method for preparing the secondary battery includes the following steps:

[0101] (1) Preparation of negative electrode sheet

[0102] S1. Provide a support layer, wherein the support layer is PET, its Young's modulus is 2 GPa, its thickness is 10 μm, and its length is 102-107 mm;

[0103] S2. A copper metal thin film is deposited under vacuum conditions using a vapor deposition method. The copper vapor forms a composite film on the surface of the PET film substrate, and finally a conductive layer is formed on the two surfaces in the thickness direction of the support layer. The thickness of the conductive layer is 1-8 μm and the length is 102 mm. The conductive layer and the support layer constitute the negative electrode current collector. S3. A pure lithium strip with a thickness of 15-50 μm is bonded to the two surfaces in the thickness direction of the negative electrode current collector by roll forming. The length of the pure lithium strip corresponds to the length of the conductive layer.

[0104] (2) Preparation of positive electrode sheet

[0105] The ternary active material Ni96, conductive carbon black (Super P), and polyvinylidene fluoride (PVDF) were mixed in a weight ratio of 97:1.5:1.5. N-methylpyrrolidone (NMP) was added as a solvent to prepare a slurry with a solid content of 0.75%, and the mixture was stirred evenly. The slurry was then uniformly coated onto the positive electrode current collector aluminum foil and dried at 90°C to obtain the positive electrode sheet with an areal capacity of 4.5 mAh / cm². 2 After coating, cold pressing was performed, achieving a compaction density of 3.4 g / cm³. 3 Then, the electrode sheet is cut into 98mm×98mm sizes for later use.

[0106] (3) Preparation of electrolyte

[0107] In a dry argon atmosphere, the organic solvent ethylene glycol dimethyl ether (DME) and 1,1,2,2-tetrafluoro-3-(1,1,2,2-tetrafluoroethoxy)propane (TTE) were first mixed at a mass ratio of DME:TTE = 1:3. Then, lithium bis(fluorosulfonyl)imide (LiFSI) was added to the organic solvent to dissolve and mix thoroughly to obtain an electrolyte with a lithium salt concentration of 4.5M: 4.5M LiFSI in 25% DME + 75% TTE.

[0108] (4) Assembly

[0109] Polyethylene (PE) with a transverse tensile strength of 500 MPa was selected as the release film;

[0110] The ends of the separator and the support layer are hot-pressed together, with a length of 0.3–1.7 cm, to form a bonding section, a body section, a bonding section located on the surface of the support layer, and a transition section connecting the body section and the bonding section, all with a length of 0.3–1.7 cm. These sections are then stacked, with positive and negative electrode sheets on either side of the separator, and a separator membrane between the electrodes. After stacking, tabs are welded on. The stacked battery is then placed in an aluminum-plastic film, top-side sealed, injected with electrolyte, and encapsulated to obtain a lithium metal laminated battery.

[0111] Example 27

[0112] The difference between Example 27 and Example 16 is that Example 27 uses a lithium-silver alloy instead of pure lithium strips, but everything else is the same.

[0113] Example 28

[0114] The difference between Example 28 and Example 16 is that, based on Example 16, Example 28 has a protective layer on the surface of the pure lithium strip. The protective layer is a polyethylene oxide polymer and has a thickness of 10 nm.

[0115] Example 29

[0116] The difference between Example 29 and Example 16 is that, based on Example 16, Example 29 has a protective layer on the surface of the pure lithium strip, and the protective layer has a thickness of 300 nm.

[0117] The parameters of the embodiments and comparative examples are shown in Table 1.

[0118] Table 1

[0119]

[0120]

[0121] Test case

[0122] Cyclic performance: Constant current charge and discharge tests were conducted using the Xinwei testing system, with a charge and discharge voltage of 2.8-4.25V, charging at a rate of 0.2C, and discharging at a rate of 0.5C.

[0123] Energy density: The battery mass energy density (Wh / kg) is obtained by dividing the tested battery discharge energy by the battery mass.

[0124] Table 2

[0125]

[0126]

[0127] As can be seen from Tables 1 and 2, the secondary battery described in this application has excellent energy density and cycle performance.

[0128] Comparing Examples 1-10 and Comparative Examples 1-3, it can be seen that the present invention effectively improves energy density and cycle performance by controlling 1cm≤D≤4cm.

[0129] Comparing Examples 1 to 10, it can be seen that, under the condition of controlling 1cm≤D≤4cm, the present invention further controls the thickness of the negative electrode material layer to 15-50μm and the thickness of the conductive layer to 1-4μm, thereby further improving the energy density and cycle performance.

[0130] Comparing Examples 1-6 with Examples 11-26, it can be seen that the present invention controls 2≤D2 / D1≤6.5, which further improves energy density and cycle performance, and controls 0.01≤H1 / D1≤0.025, which further improves energy density and cycle performance.

[0131] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application and are not intended to limit the scope of protection of this application. Although this application has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of this application without departing from the substance and scope of the technical solutions of this application.

Claims

1. A secondary battery, characterized in that, It includes a negative electrode, a positive electrode, and a separator, wherein the separator is disposed between the positive electrode and the negative electrode, and the negative electrode includes a negative current collector and a negative electrode material layer disposed on at least one surface of the negative current collector; The negative electrode current collector includes a support layer and a conductive layer disposed on at least one surface of the support layer; The length of the support layer is A1, the length of the conductive layer is A2, D = A1 - A2, 1 cm ≤ D ≤ 4 cm; At least a portion of the diaphragm and the support layer are bonded together; The length A1 of the support layer is 91~155mm; The diaphragm includes a body segment located on the surface of the negative electrode material layer, an adhesive segment located on the surface of the support layer, and a transition segment connecting the body segment and the adhesive segment. The length of the adhesive segment is D2, 0.3cm≤D2≤1.7cm. The distance between the adhesive segment and the conductive layer is D1, where 0.2cm≤D1≤0.3cm.

2. The secondary battery according to claim 1, characterized in that, The conditions D1 and D2 satisfy: 2≤D2 / D1≤6.

5.

3. The secondary battery according to claim 1, characterized in that, Satisfy at least one of the following conditions (a) to (c): (a) The thickness of the negative electrode material layer is 15~50 μm; (b) The thickness of the conductive layer is 1~4 μm; (c) The thickness of the support layer is 6~15μm.

4. The secondary battery according to claim 2, characterized in that, The total thickness of the negative electrode material layer and the conductive layer is H1, and H1 and D1 satisfy: 0.01≤H1 / D1≤0.

025.

5. The secondary battery according to claim 1, characterized in that, The negative electrode material layer includes at least one of lithium strip and lithium-based alloy, wherein the lithium-based alloy includes at least one of Li-Ag, Li-Al, Li-B, Li-Mg, Li-Au, Li-Na, Li-Si, Li-Sn, Li-Zn, Li-Ba, Li-Bi, Li-C, Li-Ca, Li-Ge, Li-Cs, Li-Ga, Li-K, Li-Pb, Li-P, Li-Sb, Li-B-Mg, and Li-Mg-Si.

6. The secondary battery according to claim 1, characterized in that, It also includes a protective layer, which is located on at least one surface of the negative electrode material layer, and the thickness of the protective layer is 10~300 nm.

7. The secondary battery according to claim 1, characterized in that, The support layer is at least one of a polymer, fiberglass, and / or The conductive layer includes at least one of a conductive metal and a conductive non-metal. The conductive metal includes at least one of Au, Ag, Al, Cu, Ni, Au-based alloys, Ag-based alloys, Al-based alloys, Cu-based alloys, and Ni-based alloys. The conductive non-metal includes at least one of graphite, acetylene black, carbon black, graphene, carbon fiber, and carbon nanotubes.

8. An electrical device, characterized in that, The device includes the secondary battery as described in any one of claims 1 to 7, wherein the secondary battery serves as the power supply for the electrical device.

Images