Positive pole piece, lithium ion battery and electric equipment

Abstract

The invention belongs to the technical field of new energy, and particularly relates to a positive pole piece, a lithium ion battery and electric equipment. The positive pole piece provided by the invention comprises a positive current collector, and at least one side surface of the positive current collector comprises a first active layer, a fast ion conductor layer, a lithium supplementing layer and a second active layer which are arranged in sequence. In the application, the inner layer area of the pole piece is coated with the fast ion conductor layer as a solid electrolyte, so that the fast ion conductor layer plays a role of an ion conductor, lithium ions are effectively released, and the problems of poor infiltration of electrolyte in the pole piece, difficult de-intercalation of the lithium ions and the like are avoided; meanwhile, the fast ion conductor layer needs to consume a small amount of lithium ions, so that the fast ion conductor layer is coated with the lithium supplementing layer to reduce the active lithium loss of the fast ion conductor layer, and the redundant lithium ions of the lithium supplementing layer can be used for supplementing the lithium ion consumption in the later period of circulation to avoid the problems of circulation diving, lithium separation and the like of the lithium ion battery; the arrangement of the double active layers can ensure the energy density.

Description

Technical Field

[0001] The present application belongs to the field of new energy technology, and specifically relates to a positive electrode sheet, a lithium-ion battery and an electrical device. Background Art

[0002] The energy storage and power battery market has higher and higher performance requirements for lithium-ion batteries. In order to meet the needs of large-scale energy storage such as electric vehicles, the next generation of power batteries requires higher energy density and higher cycle life. The capacity of lithium-ion batteries has gradually increased from 280Ah to 324Ah while the size remains unchanged. At the same time, the cycle performance has been increased to more than 12,000 times and there is a certain demand for fast charging performance.

[0003] The performance of the positive electrode will directly affect the overall performance of the battery. Under this market demand, the design of the positive electrode also tends to be thick electrode and high-pressure solid electrode design. This will result in a lower gap inside the electrode, leading to poor electrolyte infiltration in the inner layer of the electrode, low lithium ion conductivity, and difficulty in deintercalation, which will in turn cause a series of consequences such as battery cell cycle diving and lithium precipitation, which cannot meet the use requirements. Summary of the invention

[0004] Therefore, the technical problem to be solved by the present application is to overcome the defects of the prior art such as poor electrolyte infiltration of thick electrodes and high-voltage solid electrodes, cycle diving and lithium deposition in the battery cells, so as to provide a positive electrode, a lithium-ion battery and an electrical device.

[0005] To this end, this application provides the following technical solutions: According to one aspect of the present application, the present application provides a positive electrode sheet, comprising: Positive electrode current collector; A first active layer is disposed on at least one side surface of the positive electrode current collector; A fast ion conductor layer is disposed on at least a portion of the surface of the first active layer; A lithium supplement layer is disposed on at least a portion of the surface of the fast ion conductor layer; The second active layer is arranged on the surface of the lithium replenishing layer.

[0006] In some optional embodiments, the thickness of the first active layer is 50-150 μm; as an example, the thickness of the first active layer is 50 μm, 70 μm, 80 μm, 90 μm, 100 μm, 120 μm, 130 μm, 150 μm, or within a range of any of the above values; And / or, the thickness of the second active layer is 50-150 μm; as an example, the thickness of the first active layer is 50 μm, 70 μm, 80 μm, 90 μm, 100 μm, 120 μm, 130 μm, 150 μm, or within the range of any of the above values; And / or, the compaction density of the positive electrode sheet is ≥2.5g / cm 3 As an example, the compaction density of the positive electrode sheet is 2.5 g / cm 3 , 2.55g / cm 3 , 2.6g / cm 3 , 2.65g / cm 3 , 2.7g / cm 3 , 2.75g / cm 3 , 2.8g / cm 3 , or within a range consisting of any of the above values.

[0007] In some optional embodiments, the thickness of the first active layer is 50-80 μm; And / or, the thickness of the second active layer is 50-80 μm; And / or, the compaction density of the positive electrode sheet is 2.5-2.8 g / cm 3 .

[0008] In some optional embodiments, the thickness of the fast ion conductor layer is 1-10 μm; as an example, the thickness of the fast ion conductor layer is 1 μm, 1.5 μm, 2 μm, 3 μm, 5 μm, 7 μm, 9 μm, 10 μm, or within the range of any of the above values; And / or, the thickness of the lithium replenishing layer is 1-10 μm; as an example, the thickness of the fast ion conductor layer is 1 μm, 1.5 μm, 2 μm, 3 μm, 5 μm, 7 μm, 9 μm, 10 μm, or within the range of any of the above values.

[0009] In some optional embodiments, the thickness of the fast ion conductor layer is 1-2 μm; And / or, the thickness of the lithium replenishing layer is 1-2 μm.

[0010] It can be understood that, in order to increase the capacity, the first active layer is preferably disposed on both side surfaces of the positive electrode current collector.

[0011] In the present application, the thickness of the first active layer, the second active layer, the fast ion conductor layer and the lithium replenishing layer all refer to the thickness of each functional layer on a single side of the positive electrode current collector.

[0012] In some optional embodiments, the fast ion conductor layer includes a fast ion conductor and a binder in a mass ratio of (92-97):(3-8); as an example, the mass ratio of the fast ion conductor and the binder in the fast ion conductor layer is 92:8, 92.5:7.5, 93:7, 93.5:6.5, 94:6, 95:5, 96:4, 97:3, or within the range of any of the above values; The fast ion conductor includes at least one of a garnet-type ion conductor, a perovskite-type ion conductor, a sodium superion conductor, a lithium superion conductor or an argyrodite-type solid electrolyte.

[0013] In some optional embodiments, the lithium replenishing layer includes a lithium replenishing agent, a binder and a conductive agent in a mass ratio of (90-96):(3-8):(1-2); as an example, the mass ratio of the lithium replenishing agent, the binder and the conductive agent in the lithium replenishing layer is 92:7:1, 90:8:2, 93:5:2, 93:5.5:1.5, 91:7.5:1.5, 95:4:1, 94.5:4:1.5, 96:3:1, or within the range of any of the above values; The lithium supplement includes at least one of Li2NiO2, Li5FeO4, Li3N, Li2O, Li2S, LiF, and Li2O2.

[0014] In some optional embodiments, the first active layer includes a first positive electrode material, a first binder, and a first conductive agent, and the mass ratio of the three is (96-98): (0.5-3): (0.5-2); And / or, the second active layer includes a second positive electrode material, a second binder, and a second conductive agent, and the mass ratio of the three is (96~98): (0.5~3): (0.5~2).

[0015] In the present application, the fast ion conductor includes at least one of a garnet-type ion conductor, a perovskite-type ion conductor, a sodium superion conductor, a lithium superion conductor or a sulfide-type solid electrolyte; as an example, the garnet-type ion conductor includes but is not limited to Li5La3M2O 12 ; The perovskite ion conductor includes but is not limited to La 2 / 3 Li 1 / 3 TiO3; the sodium superion conductor includes but is not limited to Li 1.3 Al 0.3 Ti 1.7 (PO4)3; the lithium superion conductor includes but is not limited to Li2SiS3; the sulfide-type solid electrolyte includes but is not limited to at least one of Li2S.

[0016] In the present application, the first positive electrode material in the first active layer and the second positive electrode material in the second active layer are conventional in the field, and the two may be the same or different, and each independently includes at least one of lithium cobalt oxide, ternary positive electrode material, lithium iron phosphate, lithium manganese iron phosphate, etc.

[0017] In the present application, the first conductive agent in the first active layer, the second conductive agent in the second active layer and the conductive agent in the lithium supplement layer are conventional in the field, they may be the same or different, and each independently includes at least one of carbon nanotubes, carbon black, conductive graphite, carbon fiber, graphene, etc.

[0018] In the present application, the first binder in the first active layer, the second binder in the second active layer, the binder in the fast ion conductor layer and the binder in the lithium supplement layer are all conventional in the field. They may be the same or different, and each independently includes at least one of polyvinylidene fluoride, styrene-butadiene rubber, carboxymethyl cellulose, polyacrylic acid, polyacrylonitrile, polyacrylate, etc.

[0019] In the present application, the positive electrode current collector includes but is not limited to aluminum foil with a thickness of 6 to 20 μm.

[0020] According to another aspect of the present application, a lithium-ion battery is provided, comprising the above-mentioned positive electrode plate.

[0021] According to another aspect of the present application, there is provided an electrical device comprising the above-mentioned lithium-ion battery.

[0022] The lithium-ion battery provided in the present application includes, in addition to the above-mentioned positive electrode plate, a negative electrode plate, a separator, an electrolyte and a casing, etc., and its composition and preparation method are conventional in the field.

[0023] As an example, the negative electrode plate is composed of a negative electrode material, a binder, and a conductive agent; the negative electrode material includes but is not limited to at least one of graphite, silicon, lithium titanate, etc.; the binder includes but is not limited to at least one of polyvinylidene fluoride, styrene-butadiene rubber, carboxymethyl cellulose, polyacrylic acid, polyacrylonitrile, polyacrylate, etc.; the conductive agent contains at least one of carbon nanotubes, carbon black, conductive graphite, carbon fiber, graphene, etc.

[0024] In the present application, the diaphragm can be a polypropylene film, a polyvinylidene fluoride film, etc.; the electrolyte contains lithium hexafluorophosphate, propylene carbonate, ethylene carbonate, dimethyl carbonate, etc.; the shell contains an aluminum-plastic film, an aluminum shell, etc.

[0025] In the present application, each functional layer of the positive electrode plate can be prepared by using equipment and methods known in the art. As an example, it can be prepared by coating, and the specific operation is not specifically limited.

[0026] In the electric device provided in the present application, the lithium-ion battery can be used as a power source of the electric device, and can also be used as an energy storage unit of the electric device. The electric device can be, but is not limited to, a mobile device (such as a mobile phone, a laptop computer, etc.), an electric vehicle (such as a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a ship and a satellite, an energy storage system, etc.

[0027] The technical solution of this application has the following advantages: The positive electrode plate provided in the present application includes: a positive current collector; a first active layer, arranged on at least one side surface of the positive current collector; a fast ion conductor layer, arranged on at least part of the surface of the first active layer; a lithium supplement layer, arranged on at least part of the surface of the fast ion conductor layer; and a second active layer, arranged on the surface of the lithium supplement layer. In the present application, a fast ion conductor layer is coated on the inner layer area of ​​the electrode plate as a solid electrolyte, which acts as an ion conductor and effectively releases lithium ions to avoid problems such as poor electrolyte infiltration inside the electrode plate and difficulty in lithium ion deintercalation. At the same time, since the fast ion conductor layer needs to consume a small amount of lithium ions, a lithium supplement layer is coated on the fast ion conductor layer to reduce the active lithium loss of the fast ion conductor layer. At the same time, the excess lithium ions of the lithium supplement layer can be used to supplement the lithium ion consumption in the later stage of the cycle to avoid problems such as cycle diving and lithium precipitation of lithium ion batteries. The setting of the double active layer can ensure energy density. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the specific implementation methods of the present application or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0029] Figure 1 It is a schematic diagram of the structure of the positive electrode sheet in the embodiment of the present application; Reference numerals: 1. Positive electrode plate; 11. Positive electrode current collector; 12. First active layer; 13. Fast ion conductor layer; 14. Lithium replenishing layer; 15. Second active layer.

[0030] The numbering method of the figure marks, for example: a composition includes: component A, represented by 1, component A includes three parts, which are represented by 11, 12 and 13 respectively. DETAILED DESCRIPTION

[0031] The following examples are provided for a better understanding of the present application, but are not limited to the best implementation mode described, and do not limit the content and protection scope of the present application. Any product identical or similar to the present application obtained by anyone under the inspiration of the present application or by combining the features of the present application with other prior arts shall fall within the protection scope of the present application.

[0032] If no specific experimental steps or conditions are specified in the examples, the conventional experimental steps or conditions described in the literature in the field can be used. If no manufacturer is specified for the reagents or instruments used, they are all conventional reagent products that can be obtained commercially.

[0033] Example 1 This embodiment provides a positive electrode sheet, and its structural schematic diagram is as follows Figure 1 As shown, the positive electrode plate 1 includes a positive electrode current collector 11, and a first active layer 12 arranged on both sides of the positive electrode current collector 11, and a fast ion conductor layer 13, a lithium supplement layer 14 and a second active layer 15 are sequentially arranged on the surface of the first active layer 12 on both sides of the positive electrode current collector 11; Wherein, the positive electrode current collector is aluminum foil with a thickness of 13 μm; On one side of the positive electrode current collector, the first active layer has a thickness of 65 μm and is composed of positive electrode material lithium iron phosphate, binder PVDF (average molecular weight 800,000, the same below), conductive agent carbon black (SP), and carbon nanotubes, and the mass ratio of the four is 97:2:0.5:0.5; The thickness of the fast ion conductor layer is 1 μm, and the fast ion conductor Li 1.3 Al 0.3 Ti 1.7 (PO4)3 and binder PVDF, the mass ratio of the two is 97:3; The lithium supplement layer has a thickness of 1 μm and is composed of a lithium supplement agent Li2NiO2, a binder PVDF, and a conductive agent carbon black (SP), and the mass ratio of the three is 97:2:1; The second active layer has a thickness of 75 μm and is composed of positive electrode material lithium iron phosphate, binder PVDF, conductive agent carbon black and carbon nanotubes, and the mass ratio of the four is 97:2:0.5:0.5; The preparation method of the positive electrode plate comprises: adding lithium iron phosphate, a binder PVDF, a conductive agent carbon black, and carbon nanotubes to an appropriate amount of N-methylpyrrolidone according to the above proportions, and controlling the solid content to 65wt% as a first active layer and a second active layer coating slurry; 1.3 Al 0.3 Ti 1.7(PO4)3. Add the binder PVDF to an appropriate amount of N-methylpyrrolidone according to the above proportion, and control the solid content to 92wt% as a fast ion conductor layer slurry; add Li2NiO2, binder PVDF, and conductive agent to an appropriate amount of N-methylpyrrolidone according to the above mass ratio, and control the solid content to 60wt% as a lithium supplement layer slurry; different levels of slurry are coated on the current collector in sequence, and the coating order is the first active layer, fast ion conductor layer, lithium supplement layer, and second active layer, and the compaction density is controlled to be 2.6g / cm 3 .

[0034] Example 2 This embodiment provides a positive electrode sheet, and its structural schematic diagram is as follows Figure 1 As shown, the positive electrode plate 1 includes a positive electrode current collector 11, and a first active layer 12 arranged on both sides of the positive electrode current collector 11, and a fast ion conductor layer 13, a lithium supplement layer 14 and a second active layer 15 are sequentially arranged on the surface of the first active layer 12 on both sides of the positive electrode current collector 11; Wherein, the positive electrode current collector is aluminum foil with a thickness of 13 μm; On one side of the positive electrode current collector, the first active layer has a thickness of 120 μm and is composed of positive electrode material lithium iron phosphate, binder PVDF, conductive agent carbon black and carbon nanotubes, and the mass ratio of the four is 97:2:0.5:0.5; The thickness of the fast ion conductor layer is 1 μm, and the fast ion conductor Li 1.3 Al 0.3 Ti 1.7 (PO4)3 and binder PVDF, the mass ratio of the two is 97:3; The lithium supplement layer has a thickness of 1 μm and is composed of a lithium supplement agent Li2NiO2, a binder PVDF, and a conductive agent carbon black (SP), and the mass ratio of the three is 97:2:1; The second active layer has a thickness of 120 μm and is composed of positive electrode material lithium iron phosphate, binder PVDF, conductive agent carbon black and carbon nanotubes, and the mass ratio of the four is 97:2:0.5:0.5; The preparation method of the positive electrode plate comprises: adding lithium iron phosphate, a binder PVDF, a conductive agent carbon black, and carbon nanotubes to an appropriate amount of N-methylpyrrolidone according to the above proportions, and controlling the solid content to 65wt%, as a first active layer and a second active layer slurry; 1.3 Al 0.3 Ti 1.7(PO4)3. Add the binder PVDF to an appropriate amount of N-methylpyrrolidone in the above proportions, and control the solid content to 92wt% as a fast ion conductor layer slurry; add Li2NiO2, binder PVDF, and conductive agent (SP) to an appropriate amount of N-methylpyrrolidone in the above proportions, and control the solid content to 60wt% as a lithium supplement layer slurry; different levels of slurry are coated on the current collector in sequence, and the coating order is the first active layer, fast ion conductor layer, lithium supplement layer, and second active layer, using a compaction density of 2.6g / cm 3 .

[0035] Example 3 This embodiment provides a positive electrode sheet, and its structural schematic diagram is as follows Figure 1 As shown, the positive electrode plate 1 includes a positive electrode current collector 11, and a first active layer 12 arranged on both sides of the positive electrode current collector 11, and a fast ion conductor layer 13, a lithium supplement layer 14 and a second active layer 15 are sequentially arranged on the surface of the first active layer 12 on both sides of the positive electrode current collector 11; Wherein, the positive electrode current collector is aluminum foil with a thickness of 13 μm; On one side of the positive electrode current collector, the first active layer has a thickness of 50 μm and is composed of positive electrode material lithium iron phosphate, binder PVDF, conductive agent carbon black and carbon nanotubes, and the mass ratio of the four is 97:2:0.5:0.5; The thickness of the fast ion conductor layer is 1 μm, and the fast ion conductor Li 1.3 Al 0.3 Ti 1.7 (PO4)3 and binder PVDF, the mass ratio of the two is 97:3; The lithium supplement layer has a thickness of 1 μm and is composed of a lithium supplement agent Li2NiO2, a binder PVDF, and a conductive agent carbon black (SP), and the mass ratio of the three is 97:2:1; The second active layer has a thickness of 50 μm and is composed of positive electrode material lithium iron phosphate, binder PVDF, conductive agent carbon black and carbon nanotubes, and the mass ratio of the four is 97:2:0.5:0.5; The preparation method of the positive electrode plate comprises: adding lithium iron phosphate, a binder PVDF, a conductive agent carbon black, and carbon nanotubes to an appropriate amount of N-methylpyrrolidone according to the above proportions, and controlling the solid content to 65wt%, as a first active layer and a second active layer slurry; 1.3 Al 0.3 Ti 1.7(PO4)3. Add the binder PVDF to an appropriate amount of N-methylpyrrolidone in the above proportions, and control the solid content to 92wt% as a fast ion conductor layer slurry; add Li2NiO2, binder PVDF, and conductive agent to an appropriate amount of N-methylpyrrolidone in the above proportions, and control the solid content to 60wt% as a lithium supplement layer slurry; different levels of slurry are coated on the current collector in sequence, and the coating order is the first active layer, fast ion conductor layer, lithium supplement layer, and second active layer, using a compaction density of 2.6g / cm 3 .

[0036] Example 4 This embodiment provides a positive electrode sheet, and its structural schematic diagram is as follows Figure 1 As shown, the positive electrode plate 1 includes a positive electrode current collector 11, and a first active layer 12 arranged on both sides of the positive electrode current collector 11, and a fast ion conductor layer 13, a lithium supplement layer 14 and a second active layer 15 are sequentially arranged on the surface of the first active layer 12 on both sides of the positive electrode current collector 11; Wherein, the positive electrode current collector is aluminum foil with a thickness of 13 μm; On one side of the positive electrode current collector, the first active layer has a thickness of 80 μm and is composed of positive electrode material lithium iron phosphate, binder PVDF, conductive agent carbon black and carbon nanotubes, and the mass ratio of the four is 97:2:0.5:0.5; The thickness of the fast ion conductor layer is 1 μm, and the fast ion conductor Li 1.3 Al 0.3 Ti 1.7 (PO4)3 and binder PVDF, the mass ratio of the two is 97:3; The lithium supplement layer has a thickness of 1 μm and is composed of a lithium supplement agent Li2NiO2, a binder PVDF, and a conductive agent carbon black (SP), and the mass ratio of the three is 97:2:1; The second active layer has a thickness of 80 μm and is composed of positive electrode material lithium iron phosphate, binder PVDF, conductive agent carbon black and carbon nanotubes, and the mass ratio of the four is 97:2:0.5:0.5; The preparation method of the positive electrode plate comprises: adding lithium iron phosphate, a binder PVDF, a conductive agent carbon black, and carbon nanotubes to an appropriate amount of N-methylpyrrolidone according to the above proportions, and controlling the solid content to 65wt%, as a first active layer and a second active layer slurry; 1.3 Al 0.3 Ti 1.7(PO4)3. Add the binder PVDF to an appropriate amount of N-methylpyrrolidone in the above proportions, and control the solid content to 92wt% as a fast ion conductor layer slurry; add Li2NiO2, binder PVDF, and conductive agent to an appropriate amount of N-methylpyrrolidone in the above proportions, and control the solid content to 60wt% as a lithium supplement layer slurry; different levels of slurry are coated on the current collector in sequence, and the coating order is the first active layer, fast ion conductor layer, lithium supplement layer, and second active layer, using a compaction density of 2.6g / cm 3 .

[0037] Example 5 This embodiment provides a positive electrode sheet, and its structural schematic diagram is as follows Figure 1 As shown, the positive electrode plate 1 includes a positive electrode current collector 11, and a first active layer 12 arranged on both sides of the positive electrode current collector 11, and a fast ion conductor layer 13, a lithium supplement layer 14 and a second active layer 15 are sequentially arranged on the surface of the first active layer 12 on both sides of the positive electrode current collector 11; Wherein, the positive electrode current collector is aluminum foil with a thickness of 13 μm; On one side of the positive electrode current collector, the first active layer has a thickness of 65 μm and is composed of positive electrode material lithium cobalt oxide, binder PVDF, conductive agent carbon black and carbon nanotubes, and the mass ratio of the four is 97:2:0.5:0.5; The thickness of the fast ion conductor layer is 1 μm, and the fast ion conductor Li 1.3 Al 0.3 Ti 1.7 (PO4)3 and binder PVDF, the mass ratio of the two is 97:3; The lithium supplement layer has a thickness of 1 μm and is composed of a lithium supplement agent Li2NiO2, a binder PVDF, and a conductive agent carbon black (SP), and the mass ratio of the three is 97:2:1; The second active layer has a thickness of 65 μm and is composed of a positive electrode material, lithium cobalt oxide (LiCoO2), a binder, PVDF, and a conductive agent, carbon black, and carbon nanotubes, with a mass ratio of 97:2:0.5:0.5; The preparation method of the positive electrode plate comprises: adding lithium cobalt oxide, a binder PVDF, a conductive agent carbon black, and carbon nanotubes to an appropriate amount of N-methylpyrrolidone according to the above proportions, and controlling the solid content to 75wt%, as a first active layer and a second active layer slurry; 1.3 Al 0.3 Ti 1.7(PO4)3. Add the binder PVDF to an appropriate amount of N-methylpyrrolidone in the above proportions, and control the solid content to 92wt% as a fast ion conductor layer slurry; add Li2NiO2, binder PVDF, and conductive agent to an appropriate amount of N-methylpyrrolidone in the above proportions, and control the solid content to 60wt% as a lithium supplement layer slurry; different levels of slurry are coated on the current collector in sequence, and the coating order is the first active layer, fast ion conductor layer, lithium supplement layer, and second active layer, using a compaction density of 4.1g / cm 3 .

[0038] Example 6 This embodiment provides a positive electrode sheet, and its structural schematic diagram is as follows Figure 1 As shown, the positive electrode plate 1 includes a positive electrode current collector 11, and a first active layer 12 arranged on both sides of the positive electrode current collector 11, and a fast ion conductor layer 13, a lithium supplement layer 14 and a second active layer 15 are sequentially arranged on the surface of the first active layer 12 on both sides of the positive electrode current collector 11; Wherein, the positive electrode current collector is aluminum foil with a thickness of 13 μm; On one side of the positive electrode current collector, the first active layer has a thickness of 65 μm and is composed of a positive electrode ternary material (LiNi 0.6 Co 0.2 Mn 0.2 O2), binder PVDF and conductive agent carbon black, carbon nanotubes, the mass ratio of the four is 97:2:0.5:0.5; The thickness of the fast ion conductor layer is 1 μm, and the fast ion conductor Li 1.3 Al 0.3 Ti 1.7 (PO4)3 and binder PVDF, the mass ratio of the two is 97:3; The lithium supplement layer has a thickness of 1 μm and is composed of a lithium supplement agent Li2NiO2, a binder PVDF, and a conductive agent carbon black (SP), and the mass ratio of the three is 97:2:1; The thickness of the second active layer is 65 μm, and the positive electrode material is ternary material (LiNi 0.6 Co 0.2 Mn 0.2 O2), binder PVDF and conductive agent carbon black, carbon nanotubes, the mass ratio of the four is 97:2:0.5:0.5; The preparation method of the positive electrode plate comprises: adding lithium cobalt oxide, a binder PVDF, a conductive agent carbon black, and carbon nanotubes to an appropriate amount of N-methylpyrrolidone according to the above proportions, and controlling the solid content to 75wt%, as a first active layer and a second active layer slurry; 1.3 Al 0.3 Ti 1.7(PO4)3. Add the binder PVDF to an appropriate amount of N-methylpyrrolidone in the above proportions, and control the solid content to 92wt% as a fast ion conductor layer slurry; add Li2NiO2, binder PVDF, and conductive agent to an appropriate amount of N-methylpyrrolidone in the above proportions, and control the solid content to 60wt% as a lithium supplement layer slurry; different levels of slurry are coated on the current collector in sequence, and the coating order is the first active layer, fast ion conductor layer, lithium supplement layer, and second active layer, using a compaction density of 3.8g / cm 3 .

[0039] Comparative Example 1 This comparative example provides a positive electrode plate, which is different from Example 1 only in that it does not include a fast ion conductor layer and a lithium supplement layer.

[0040] Comparative Example 2 This comparative example provides a positive electrode plate, which is different from Example 1 only in that it does not include a fast ion conductor layer.

[0041] Comparative Example 3 This comparative example provides a positive electrode plate, which is different from Example 1 only in that it does not include a lithium supplement layer.

[0042] Comparative Example 4 This comparative example provides a positive electrode plate, which is different from Example 1 only in that the positions of the fast ion conductor layer and the lithium replenishing layer are interchanged, that is, the surface of the positive electrode current collector includes a first active layer, a lithium replenishing layer, a fast ion conductor layer and a second active layer arranged in sequence.

[0043] Test Case The positive electrode sheets provided in each embodiment and comparative example are assembled into a battery and tested, wherein the assembly of the battery includes the following steps: Preparation of negative electrode sheets: Graphite, conductive agent SP, thickener CMC, and binder SBR are added to an appropriate amount of deionized water in a mass ratio of 96:1:1:2, and the solid content is controlled to 52wt%. The prepared slurry is evenly coated on the copper foil and formed into a negative electrode sheet by rolling after drying.

[0044] The composition of the electrolyte: includes the following components in percentage by mass: lithium hexafluorophosphate: ethylene carbonate: propylene carbonate: vinylene carbonate: ethyl methyl carbonate = 15%: 30%: 30%: 5%: 20%.

[0045] The separator is a PE film with a thickness of 9 μm.

[0046] The positive electrode sheet provided in each embodiment and comparative example, the above-mentioned negative electrode sheet, and the separator are assembled by winding, and are packaged with an aluminum-plastic film to obtain a soft-package dry battery cell. After the above-mentioned electrolyte is injected into the soft-package dry battery cell, it is allowed to stand at 45° C. for 2 days and formed on a formation machine to obtain a lithium-ion battery with a model of 4060D0.

[0047] 1. Capacity test The lithium-ion battery after formation was left standing at 45°C for 2 days, then charged to 3.65V at 0.33C constant current and constant voltage on a capacity analyzer. After standing for 5 minutes, it was discharged to 2.5V at 0.33C to obtain capacity data.

[0048] 2. Cycle performance test At 25℃±5℃, charge and discharge cycles were performed with 1.5C constant current and constant voltage charging to 3.65V and 1C constant current and constant voltage discharging to 2.5V, and the capacity retention rate after 1000 cycles was calculated.

[0049] 3. Lithium precipitation After the lithium-ion battery is charged to 3.65V at 0.33C constant current and constant voltage, the battery cell is disassembled to observe whether there is lithium deposition on the surface of the negative electrode.

[0050] 4. Fast charging performance Charge at a constant current of 5C to 3.65V to obtain the constant current capacity, then charge at a constant voltage to a current of 0.05C to obtain the total charging capacity. The constant current section capacity / total charging capacity = constant current ratio. Compare the constant current ratio values. The larger the constant current ratio, the better the fast charging performance.

[0051] The specific test results are shown in the table below: Table 1

[0052] It can be seen from the data in the above table that in Comparative Example 1, due to the lack of coating of the lithium replenishing layer and the fast ion conductor layer, the electrolyte infiltration is poor and the ion conductivity is low, resulting in rapid cycle attenuation. After disassembling the battery cell, it was found that serious lithium precipitation occurred on the surface of the negative electrode, and the 5C charging constant current ratio was only 65.2%; Compared with Example 1, Comparative Example 2 has poor electrolyte infiltration due to the lack of coating of the fast ion conductor layer in the internal area of ​​the electrode piece, but the excess lithium ions in the lithium replenishing layer can effectively supplement the lithium ion loss in the cycle process, and the cycle performance is lower than that of Example 1, but higher than that of Comparative Example 1 and Comparative Example 3. After disassembling the battery cell, it was found that slight lithium precipitation occurred on the surface of the negative electrode, and the 5C charging constant current ratio was poor due to poor internal electrolyte infiltration, resulting in poor ion conduction, and the constant current comparison was close to that of Comparative Example 1; Comparative Example 3 is compared with Example 1 and Compared with Example 2, the fast ion conductor layer can effectively improve the ionic conductivity of the inner area of ​​the electrode piece, but the lithium ion loss during the cycle is not effectively supplemented, so the cycle performance is lower than that of Example 1 and Comparative Example 2, but higher than that of Comparative Example 1. After disassembling the battery cell, it was found that there was a slight lithium deposition on the surface of the negative electrode, and the value of the 5C constant current ratio was higher than that of Comparative Example 1 and Comparative Example 2; Compared with Example 1, since the lithium replenishing layer and the fast ion conductor layer are arranged in opposite positions, an additional lithium replenishing layer is added to the inner area of ​​the electrode piece, and its ion conductivity is reduced, resulting in a cycle performance lower than that of Example 1, but higher than that of Comparative Example 1, Comparative Example 2, and Comparative Example 3. After disassembling the battery cell, it was found that there was a slight lithium deposition on the surface of the negative electrode, and the 5C charging constant current ratio was lower than that of Example 1, but higher than that of Comparative Example 1 and Comparative Example 2.

[0053] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived from these are still within the scope of protection of the invention.

Claims

1. A positive electrode sheet, characterized in that: include: Positive electrode current collector; A first active layer is disposed on at least one side surface of the positive electrode current collector; A fast ion conductor layer is disposed on at least a portion of the surface of the first active layer; A lithium supplement layer is disposed on at least a portion of the surface of the fast ion conductor layer; The second active layer is arranged on the surface of the lithium replenishing layer.

2. The positive electrode sheet according to claim 1, characterized in that: The thickness of the first active layer is 50-150 μm; And / or, the thickness of the second active layer is 50-150 μm; And / or, the compaction density of the positive electrode sheet is ≥2.5g / cm 3 .

3. The positive electrode sheet according to claim 2, characterized in that: The thickness of the first active layer is 50-80 μm; And / or, the thickness of the second active layer is 50-80 μm; And / or, the compaction density of the positive electrode sheet is 2.5-2.8 g / cm 3 .

4. The positive electrode sheet according to claim 1, characterized in that: The thickness of the fast ion conductor layer is 1-10 μm; And / or, the thickness of the lithium replenishing layer is 1-10 μm.

5. The positive electrode sheet according to claim 4, characterized in that: The thickness of the fast ion conductor layer is 1-2 μm; And / or, the thickness of the lithium replenishing layer is 1-2 μm.

6. The positive electrode sheet according to any one of claims 1 to 5, characterized in that: The fast ion conductor layer comprises a fast ion conductor and a binder in a mass ratio of (92-97):(3-8); The fast ion conductor includes at least one of a garnet-type ion conductor, a perovskite-type ion conductor, a sodium superion conductor, a lithium superion conductor or a sulfide-type solid electrolyte.

7. The positive electrode sheet according to any one of claims 1 to 5, characterized in that: The lithium replenishing layer comprises a lithium replenishing agent, a binder and a conductive agent in a mass ratio of (90-96):(3-8):(1-2); The lithium supplement includes at least one of Li2NiO2, Li5FeO4, Li3N, Li2O, Li2S, LiF, and Li2O2.

8. The positive electrode sheet according to any one of claims 1 to 5, characterized in that: The first active layer includes a first positive electrode material, a first binder, and a first conductive agent, and the mass ratio of the three is (96-98): (0.5-3): (0.5-2); And / or, the second active layer includes a second positive electrode material, a second binder, and a second conductive agent, and the mass ratio of the three is (96~98): (0.5~3): (0.5~2).

9. A lithium ion battery, characterized in that: A positive electrode sheet comprising the positive electrode sheet according to any one of claims 1 to 8.

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

Images