Positive electrode sheet, method for manufacturing the same, secondary battery, and power using device

Abstract

The application discloses a positive electrode sheet, a preparation method thereof, a secondary battery and a power utilization device. The positive electrode sheet comprises a current collector and a positive electrode material arranged on the current collector. The current collector comprises a base material and a current collecting layer. The positive electrode material is arranged on the current collecting layer. The base material is an aluminum foil. The current collecting layer is a lithium-containing metal. Through the arrangement of the positive electrode sheet, the lithium-containing metal current collecting layer plays a role of lithium supplement. Lithium atoms can be oxidized into lithium ions in the charging process and enter an electrolyte, so as to supplement lithium consumed by the formation of a solid electrolyte interphase (SEI) of a lithium ion battery. In addition, since the lithium released from the current collector during the lithium supplement is all from a surface layer, the lithium supplement effect can be achieved by arranging the lithium-containing metal layer on the surface of the aluminum foil. The lithium consumption is reasonable, and the cost is low.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of batteries, in particular to a positive electrode sheet and a preparation method thereof, a secondary battery and a power utilization device. BACKGROUND

[0002] Lithium ion batteries are green and environmentally friendly secondary batteries without pollution, which meet the development needs of energy and environmental protection in today's world and are rapidly increasing in use in various industries. People's requirements for the specific energy of lithium ion batteries are also becoming higher and higher. In lithium ion batteries, the first charge-discharge efficiency is usually very low, which leads to the loss of lithium in the positive electrode material of the lithium ion battery, so it is necessary to supplement lithium to the lithium ion battery. At present, the positive electrode lithium supplement strategy generally adds a positive electrode material with high specific capacity during the positive electrode slurry process to release active lithium during the first delithiation, and the subsequent charge-discharge reaction is no longer involved, but the non-active substance will be left after the lithium supplement, which will affect the energy density and performance. It can be seen that the existing lithium supplement performance of lithium ion batteries is poor. SUMMARY

[0003] In view of the above problems, the present application provides a positive electrode sheet and a preparation method thereof, a secondary battery and a power utilization device to improve the lithium supplement performance of lithium ion batteries.

[0004] In the first aspect, the present application provides a positive electrode sheet, comprising a current collector and a positive electrode material arranged on the current collector, the current collector comprising a substrate and a current collecting layer, and the positive electrode material being arranged on the current collecting layer. The substrate is an aluminum foil, and the current collecting layer is a lithium-containing metal.

[0005] In the technical scheme of the present application, the current collecting layer is a lithium-containing metal to play a role in supplementing lithium. Lithium atoms can be oxidized into lithium ions and enter the electrolyte during the charging process to supplement the lithium consumed by the formation of the solid electrolyte interphase (SEI) in the negative electrode of the lithium ion battery.

[0006] In addition, since the lithium released from the current collector during lithium supplement all comes from the surface layer, the present application can achieve the effect of supplementing lithium by arranging a lithium-containing metal layer on the surface of the aluminum foil, which is reasonable in the amount of lithium used and low in cost.

[0007] In some embodiments, the current collecting layer is an aluminum-lithium alloy.

[0008] In the technical scheme of the present application, the aluminum in the aluminum-lithium alloy of the current collecting layer is consistent with the aluminum foil component in the substrate, which enhances the consistency of the current collector as a whole and reduces the performance loss caused by the interface difference.

[0009] In some embodiments, in the aluminum-lithium alloy, the mass ratio of aluminum and lithium is 1:1-99:1.

[0010] In the technical scheme of the present application, the lithium content is high, which can achieve the effect of continuous lithium supplement, and the cycle capacity retention rate is high.

[0011] In some embodiments, the metal element in the current collector layer further includes at least one of magnesium, vanadium, copper, iron, zinc, tin, nickel, titanium and manganese.

[0012] By adding at least one of magnesium, vanadium, copper, iron, zinc, tin, nickel, titanium and manganese, the softness of the current collector layer can be increased, which is beneficial for winding the pole piece and the diaphragm into the battery cell.

[0013] In some embodiments, the thickness of the current collector layer is 0.1-3 μm.

[0014] Since the lithium supplement effect is poor when the thickness of the current collector layer is less than 0.1 μm, and the cost is high when the thickness of the current collector layer is greater than 3 μm, by setting the thickness of the current collector layer to 0.1-3 μm, the lithium supplement effect is good and the cost is low.

[0015] In some embodiments, the surface of the current collector layer facing the positive electrode material has a pore structure.

[0016] The lithium atoms in the positive electrode material are oxidized into lithium ions into the electrolyte during the charging process, resulting in a pore structure on the surface of the current collector layer. Then, the electrolyte enters the pore structure, so that the lithium atoms of the current collector contact the electrolyte and are oxidized into lithium ions into the electrolyte, thereby continuously supplementing the lithium consumed by the negative electrode in the lithium ion battery cycle.

[0017] In some embodiments, the positive electrode material includes at least one of lithium cobaltate, lithium manganate, lithium iron phosphate and a combination of nickel cobalt manganese, which is beneficial for forming a suitable positive pole piece and better achieving the lithium supplement effect to improve the cycle performance of the battery.

[0018] In a second aspect, the application provides a preparation method of a positive pole piece, providing a substrate, the substrate being an aluminum foil; setting a current collector layer on the surface of the substrate, the current collector layer being a lithium-containing metal, wherein the powder slurry or molten slurry of the lithium-containing metal is coated on the surface of the substrate; and setting a positive electrode material on the surface of the current collector layer.

[0019] In the technical scheme of the embodiments of the application, the positive pole piece prepared by the preparation method of the positive pole piece provided by the application plays a lithium supplement role by the current collector layer being a lithium-containing metal. Lithium atoms can be oxidized into lithium ions into the electrolyte during the charging process to supplement the lithium consumed by the formation of the solid electrolyte interphase SEI of the negative electrode of the lithium ion battery.

[0020] In addition, since the lithium released from the current collector during lithium supplement comes from the surface layer, the lithium supplement effect can be achieved by setting a lithium-containing metal layer on the surface of the aluminum foil, the amount of lithium is reasonable, and the cost is low.

[0021] Thirdly, this application provides a secondary battery, including a positive electrode, a negative electrode, and a separator, wherein the separator is disposed between the positive electrode and the negative electrode, and the positive electrode is a positive electrode prepared by any of the above schemes or by a method for preparing a positive electrode.

[0022] Fourthly, this application provides an electrical device including a secondary battery provided by any of the above solutions.

[0023] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, specific embodiments of this application are given below. Attached Figure Description

[0024] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiments below. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of this application. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0025] Figure 1 This is a schematic diagram of the structure of an electrical device according to some embodiments of this application;

[0026] Figure 2 This is an exploded structural diagram of a battery according to some embodiments of this application;

[0027] Figure 3 This is an exploded structural diagram of a battery cell according to some embodiments of this application;

[0028] Figure 4 This is a schematic diagram of the structure of the positive electrode sheet in some embodiments of this application.

[0029] The reference numerals in the detailed embodiments are as follows:

[0030] 1000 electrical appliances;

[0031] Battery 100, controller 200, motor 300;

[0032] Box 10, Part 11, Part 2 12;

[0033] Battery cell 20, end cap 21, electrode terminal 21a, housing 22, cell assembly 23, tab 23a;

[0034] Positive electrode 400, substrate 401, current collector 402, positive electrode material 403. Detailed Implementation

[0035] The embodiments of the present application will be described in detail below with reference to the drawings. The following examples are only used to more clearly illustrate the technical solutions of the present application, and therefore only serve as examples, and cannot be used to limit the protection scope of the present application.

[0036] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present application; the terms "comprising," "comprises" and "including" as used herein are synonymous with and meant to have the same meaning as the term "including"; the term "coupled" as used herein means the joining of two members together with one or more intervening members.

[0037] In the description of the embodiments of the present application, the technical terms "first", "second", etc. are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features. In the description of the embodiments of the present application, the meaning of "a plurality of" is two or more, unless otherwise explicitly and specifically limited.

[0038] Reference herein to "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the present application. The appearance of the phrase in various places in the specification does not necessarily all refer to the same embodiment, nor is it necessarily independent or alternative embodiments to each other. The skilled person in the art explicitly and implicitly understands that the embodiments described herein can be combined with other embodiments.

[0039] In the description of the embodiments of the present application, the term "and / or" is only a description of the association relationship of the associated objects, which means that there can be three relationships, for example, A and / or B, which can represent the three cases of A alone, A and B together, and B alone. In addition, the character " / " in this paper generally represents that the front and rear associated objects are a "or" relationship.

[0040] In the description of the embodiments of the present application, the term "a plurality of" refers to two or more (including two), and similarly, "a plurality of groups" refers to two or more groups (including two groups), and "a plurality of pieces" refers to two or more pieces (including two pieces).

[0041] In the description of the embodiments of the present application, the orientations or positional relationships indicated by the technical terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like are based on the orientations or positional relationships shown in the drawings, and are only for the convenience of describing the embodiments of the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the embodiments of the present application.

[0042] In the description of the embodiments of the present application, unless otherwise explicitly specified and limited, the technical terms "mounting", "connecting", "connecting", "fixing" and the like should be understood broadly, for example, can be fixedly connected, can be detachably connected, or can be integrated; can be mechanically connected, or can be electrically connected; can be directly connected, or can be indirectly connected through an intermediate medium; can be the internal communication of two elements or the interaction relationship between two elements. For those skilled in the art, the specific meanings of the above terms in the embodiments of the present application can be understood according to the specific circumstances.

[0043] At present, from the development of market situation, the application of power battery is more and more widely. Power battery is not only applied to energy storage power supply system such as hydroelectric, thermal, wind and solar power station, but also widely used in electric bicycles, electric motorcycles, electric vehicles and other electric vehicles, military equipment, aerospace and other fields. With the continuous expansion of the application field of power battery, the demand of its market is also increasing.

[0044] The applicant notices that in recent years, the new energy industry has developed rapidly, and the increasing range of new energy vehicles has also increased the demand for the energy density of power batteries. The actual energy density of commercial lithium-ion batteries is slow to improve due to the embedded energy storage mechanism of the material itself, and gradually approaches the limit of 300 Wh / kg; therefore, to meet the consumer demand of the electric vehicle market, the development of secondary batteries with higher energy density has become a social consensus. However, in the process of charging and discharging of lithium-ion batteries, a solid electrolyte interphase (SEI) is formed on the negative electrode, which consumes a certain amount of lithium, which affects the energy density and cycle performance of the battery. In recent years, silicon material is commonly used as an important means to improve the energy density of lithium-ion batteries, but the first charge-discharge efficiency of the silicon negative electrode is very low, which leads to the loss of lithium in the positive electrode material of the lithium-ion battery, so lithium needs to be supplemented to the lithium-ion battery. At present, the positive electrode lithium supplement strategy generally adds high specific capacity positive electrode material during the positive electrode slurry process to release active lithium during the first delithiation, and the subsequent charging and discharging reaction is no longer involved, but the non-active substance will be left after the lithium supplement, which will affect the energy density and performance. It can be seen that the existing lithium supplement performance of lithium-ion batteries is poor.

[0045] In order to solve the problems of lithium ion loss and unsatisfactory lithium supplement effect of the prior art, the applicant finds that the current collector of the positive electrode sheet can be studied.

[0046] The application provides a positive electrode sheet, a preparation method of a positive electrode sheet, a secondary battery and an electric device. The current collector is a lithium-containing metal to supplement lithium. In the charging process, lithium atoms can be oxidized into lithium ions to enter the electrolyte to supplement the lithium consumed by the formation of the solid electrolyte interphase (SEI) on the negative electrode of the lithium-ion battery.

[0047] In addition, since the lithium released from the current collector during lithium supplement comes from the surface layer, the lithium-containing metal layer provided on the surface of the aluminum foil can supplement lithium, the amount of lithium used is reasonable, and the cost is low.

[0048] Based on the above considerations, in order to solve the problems of lithium ion loss and unsatisfactory lithium supplement effect of the prior art, the inventor has designed a positive electrode sheet, which includes a current collector and a positive electrode material provided on the current collector. The current collector includes a substrate and a current collecting layer, and the positive electrode material is provided on the current collecting layer. The substrate is an aluminum foil, and the current collecting layer is a lithium-containing metal.

[0049] In the technical scheme of the embodiments of the application, the current collecting layer is a lithium-containing metal to supplement lithium. In the charging process, lithium atoms can be oxidized into lithium ions to enter the electrolyte to supplement the lithium consumed by the formation of the solid electrolyte interphase (SEI) on the negative electrode of the lithium-ion battery.

[0050] In addition, since the lithium released from the current collector during lithium supplement is all from the surface layer, the application can achieve the effect of lithium supplement by arranging a metal layer containing lithium on the surface of the aluminum foil, and the amount of lithium is reasonable and the cost is low.

[0051] By the technical scheme provided in the application, the consumed lithium ions can be continuously supplemented, so that the battery always maintains a high specific energy, thereby improving the poor cycle performance of the battery and other problems.

[0052] The positive electrode material disclosed in the embodiments of the application can be applied to a battery monomer, and the battery monomer can be used in an electric device using a battery as a power supply or a variety of energy storage systems using a battery as an energy storage element. The electric device can be, but is not limited to, a mobile phone, a tablet, a notebook computer, an electric toy, an electric tool, an electric vehicle, an electric car, a ship, a spacecraft, and the like. Among them, the electric toy can include a fixed or mobile electric toy, such as a game console, an electric car toy, an electric ship toy, and an electric plane toy, and the like, and the spacecraft can include an airplane, a rocket, a space shuttle, a spacecraft, and the like.

[0053] The following embodiments are described by taking a vehicle as an example for convenience of description.

[0054] Please refer to Figure 1 , Figure 1 The structural schematic diagram of the electric device 1000 provided in some embodiments of the application is shown. The electric device 1000 can be a fuel automobile, a gas automobile, or a new energy automobile, and the new energy automobile can be a pure electric automobile, a hybrid electric automobile, or a range extended automobile. The electric device 1000 is internally provided with a battery 100, which can be arranged at the bottom, the head, or the tail of the electric device 1000. The battery 100 can be used for power supply of the electric device 1000, for example, the battery 100 can be used as an operating power supply of the electric device 1000. The electric device 1000 can further include a controller 200 and a motor 300, and the controller 200 is used to control the battery 100 to supply power to the motor 300, for example, to meet the working power demand of the electric device 1000 during starting, navigation, and driving.

[0055] In some embodiments of the application, the battery 100 can not only be used as an operating power supply of the electric device 1000, but also be used as a driving power supply of the electric device 1000, instead of or partially instead of fuel or natural gas to provide driving power for the electric device 1000.

[0056] Please refer to Figure 2 , Figure 2Figure 1 is a schematic diagram of a battery according to some embodiments of the present application. The battery 100 comprises a box 10 and a battery cell 20, which is accommodated in the box 10. The box 10 is configured to provide a space for accommodating the battery cell 20, and can have various structures. In some embodiments, the box 10 can comprise a first part 11 and a second part 12, which are coupled to each other to define a space for accommodating the battery cell 20. The second part 12 can be a hollow structure with an open end, and the first part 11 can be a plate structure, which is coupled to the open end of the second part 12 to define the space for accommodating the battery cell 20 together with the second part 12. Alternatively, the first part 11 and the second part 12 can both be hollow structures with an open end, and the open end of the first part 11 is coupled to the open end of the second part 12. Of course, the box 10 formed by the first part 11 and the second part 12 can have various shapes, such as a cylinder, a cuboid, etc.

[0057] In the battery 100, the battery cell 20 can be multiple, and the multiple battery cells 20 can be connected in series, in parallel, or in a mixed manner. The mixed manner means that the multiple battery cells 20 are connected in series and in parallel. The multiple battery cells 20 can be directly connected in series, in parallel, or in a mixed manner, and then the multiple battery cells 20 are accommodated in the box 10. Of course, the battery 100 can also be that the multiple battery cells 20 are connected in series, in parallel, or in a mixed manner to form a battery module, and then the multiple battery modules are connected in series, in parallel, or in a mixed manner to form a whole, which is accommodated in the box 10. The battery 100 can further comprise other structures, for example, the battery 100 can further comprise a busbar component for electrically connecting the multiple battery cells 20.

[0058] Each battery cell 20 can be a secondary battery or a primary battery, and can be a lithium-sulfur battery, a sodium-ion battery, or a magnesium-ion battery, but is not limited thereto. The battery cell 20 can have a cylindrical shape, a flat shape, a cuboid shape, or other shapes.

[0059] Figure 2 is a schematic diagram of a battery according to some embodiments of the present application. The battery 100 comprises a box 10 and a battery cell 20, which is accommodated in the box 10. The box 10 is configured to provide a space for accommodating the battery cell 20, and can have various structures. In some embodiments, the box 10 can comprise a first part 11 and a second part 12, which are coupled to each other to define a space for accommodating the battery cell 20. The second part 12 can be a hollow structure with an open end, and the first part 11 can be a plate structure, which is coupled to the open end of the second part 12 to define the space for accommodating the battery cell 20 together with the second part 12. Alternatively, the first part 11 and the second part 12 can both be hollow structures with an open end, and the open end of the first part 11 is coupled to the open end of the second part 12. Of course, the box 10 formed by the first part 11 and the second part 12 can have various shapes, such as a cylinder, a cuboid, etc. Figure 3 Figure 3 Figure 3 is a schematic diagram of a battery according to some embodiments of the present application. The battery 100 comprises a box 10 and a battery cell 20, which is accommodated in the box 10. The box 10 is configured to provide a space for accommodating the battery cell 20, and can have various structures. In some embodiments, the box 10 can comprise a first part 11 and a second part 12, which are coupled to each other to define a space for accommodating the battery cell 20. The second part 12 can be a hollow structure with an open end, and the first part 11 can be a plate structure, which is coupled to the open end of the second part 12 to define the space for accommodating the battery cell 20 together with the second part 12. Alternatively, the first part 11 and the second part 12 can both be hollow structures with an open end, and the open end of the first part 11 is coupled to the open end of the second part 12. Of course, the box 10 formed by the first part 11 and the second part 12 can have various shapes, such as a cylinder, a cuboid, etc. Figure 3

[0060] ​​The end cover 21 refers to a component that covers the opening of the shell 22 to isolate the internal environment of the battery monomer 20 from the external environment. Without limitation, the shape of the end cover 21 can be adapted to the shape of the shell 22 to fit the shell 22. Optionally, the end cover 21 can be made of a material with certain hardness and strength, such as aluminum alloy, so that the end cover 21 is not easily deformed when subjected to extrusion collision, so that the battery monomer 20 can have higher structural strength, and the safety performance can also be improved. The end cover 21 can be provided with functional components such as electrode terminals 21a. The electrode terminals 21a can be used to electrically connect with the cell assembly 23 for output or input of the electrical energy of the battery monomer 20. In some embodiments, the end cover 21 can also be provided with a pressure relief mechanism for relieving the internal pressure of the battery monomer 20 when the internal pressure or temperature of the battery monomer 20 reaches a threshold value. The material of the end cover 21 can also be various, such as copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc., and the embodiments of the present application do not make special limitations. In some embodiments, an insulating member can also be provided on the inner side of the end cover 21, which can be used to isolate the electrical connection components in the shell 22 from the end cover 21 to reduce the risk of short circuit. For example, the insulating member can be plastic, rubber, etc.

[0061] The shell 22 is a component for fitting the end cover 21 to form the internal environment of the battery monomer 20, wherein the formed internal environment can be used to accommodate the cell assembly 23, electrolyte and other components. The shell 22 and the end cover 21 can be independent components, and an opening can be provided on the shell 22, and the end cover 21 is covered on the opening to form the internal environment of the battery monomer 20. Without limitation, the end cover 21 and the shell 22 can also be integrated, specifically, the end cover 21 and the shell 22 can form a common connecting surface before other components enter the shell, and when it is necessary to encapsulate the internal environment of the shell 22, the end cover 21 is covered on the shell 22. The shell 22 can be various shapes and various sizes, such as rectangular parallelepiped, cylindrical, hexagonal prism, etc. Specifically, the shape of the shell 22 can be determined according to the specific shape and size of the cell assembly 23. The material of the shell 22 can be various, such as copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc., and the embodiments of the present application do not make special limitations.

[0062] The electrode assembly 23 is a component in which electrochemical reactions occur in the battery cell 100. One or more electrode assemblies 23 can be included in the case 22. The electrode assembly 23 is mainly formed by winding or stacking a positive electrode sheet and a negative electrode sheet, and a separator is generally provided between the positive electrode sheet and the negative electrode sheet. The positive electrode sheet and the negative electrode sheet have portions with active materials that constitute a main body of the electrode assembly, and portions without active materials that each constitute a tab 23a. The positive electrode tab and the negative electrode tab can be located together at one end of the main body or at opposite ends of the main body. During charging and discharging of the battery, the positive electrode active material and the negative electrode active material react with an electrolyte, and the tab 23a connects an electrode terminal to form a current loop.

[0063] According to some embodiments of the present application, the present application provides a positive electrode sheet, comprising a current collector and a positive electrode material disposed on the current collector, the current collector comprising a substrate and a current collecting layer, and the positive electrode material disposed on the current collecting layer, wherein the substrate is an aluminum foil, and the current collecting layer is a lithium-containing metal.

[0064] The positive electrode material, also referred to as the positive electrode active material, is a component of the positive electrode tab. The positive electrode tab comprises a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector, and the positive electrode film layer comprises the positive electrode material.

[0065] As an example, the positive electrode current collector has two opposite surfaces in the thickness direction thereof, and the positive electrode film layer is disposed on any one or both of the two opposite surfaces of the positive electrode current collector.

[0066] In some embodiments, the positive electrode current collector can be a metal foil or a composite current collector. For example, as the metal foil, an aluminum foil can be used. The composite current collector can comprise a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector can be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene glycol terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0067] In some embodiments, the positive active material can employ a positive active material for a battery known in the art. As an example, the positive active material can include at least one of a lithium-containing phosphate of an olivine structure, a lithium transition metal oxide, and a modified compound of each thereof. However, the present application is not limited to these materials, and other conventional materials that can be used as a positive active material for a battery can also be used. These positive active materials can be used alone only one or in combination of two or more. Among them, examples of the lithium transition metal oxide can include, but are not limited to, at least one of lithium cobalt oxide (e.g., LiCoO2), lithium nickel oxide (e.g., LiNiO2), lithium manganese oxide (e.g., LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (e.g., LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2(also can be abbreviated as NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O2(also can be abbreviated as NCM523), LiNi 0.5 Co 0.25 Mn 0.25 O2(also can be abbreviated as NCM211), LiNi 0.6 Co 0.2 Mn 0.2 O2(also can be abbreviated as NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O2(also can be abbreviated as NCM811), lithium nickel cobalt aluminum oxide (e.g., LiNi 0.85 Co 0.15 Al 0.05 O2), and a modified compound thereof, etc. Examples of the lithium-containing phosphate of an olivine structure can include, but are not limited to, at least one of lithium iron phosphate such as LiFePO4 (also can be abbreviated as LFP), a composite of lithium iron phosphate and carbon, lithium manganese phosphate (e.g., LiMnPO4), a composite of lithium manganese phosphate and carbon, lithium manganese iron phosphate, a composite of lithium manganese iron phosphate and carbon.

[0068] In some embodiments, the positive electrode film layer can further optionally include a binder. As an example, the binder can include at least one of polyvinylidene difluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene-fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene-fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylate resin.

[0069] In some embodiments, the positive electrode film layer also optionally includes a conductive agent. As an example, the conductive agent can include at least one of super-P, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0070] In some embodiments, the positive electrode tab can be prepared by dispersing the above-mentioned components for preparing the positive electrode tab, such as the positive electrode active material, the conductive agent, the binder, and any other components, in a solvent (such as N-methyl pyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry on a positive electrode current collector, and after processes such as drying, cold pressing, etc., the positive electrode tab can be obtained.

[0071] The current collector layer is a lithium-containing metal, which plays a role in supplementing lithium. Lithium atoms can be oxidized into lithium ions into the electrolyte during charging to supplement lithium consumed by the formation of a solid electrolyte interphase (SEI) in the negative electrode of a lithium-ion battery.

[0072] In addition, since the lithium released from the current collector during lithium supplementation all comes from the surface layer, the application can achieve the effect of supplementing lithium by providing a lithium-containing metal layer on the surface of the aluminum foil, and the amount of lithium used is reasonable, and the cost is low.

[0073] According to some embodiments of the application, optionally, the current collector layer is an aluminum-lithium alloy.

[0074] The aluminum-lithium alloy is the lightest metal element in the world. When lithium is added to aluminum as an alloying element, an aluminum-lithium alloy is formed. After adding lithium, the specific gravity of the alloy can be reduced, the stiffness can be increased, and the strength, corrosion resistance, and fatigue resistance can be maintained, and the ductility is suitable. As the current collector of the composite positive electrode, the lithium-aluminum alloy can conduct electrons, carry coating, and accurately supplement lithium for the battery.

[0075] Since the aluminum in the aluminum-lithium alloy of the current collector layer is consistent with the aluminum foil component in the base material, the consistency of the current collector as a whole is enhanced, and the performance loss caused by the interface difference is reduced.

[0076] According to some embodiments of the application, optionally, in the aluminum-lithium alloy, the mass ratio of aluminum and lithium is 1:1-99:1.

[0077] In some embodiments, the mass ratio of the aluminum element and the lithium element can be 1:1-98.91:1, 1.2:1-98.52:1, 1.31:1-98:1, 2:1-96:1, 2.2:1-97.1:1, 3.23:1-95:1, 4:1-93:1, 5.1:1-91.6:1, 7:1-98:1, 8:1-99.2:1, 9:1-99.8:1, 9.51:1-90:1, 10:1-88.21:1, 11:1-85:1, 12:1-95:1, 20:1-93:1, 21.1:1-90:1, 23:1-85:1, 25:1-83:1, 27:1-80:1, 29:1-75:1, 30:1-70:1, 33:1-69:1, 35:1-66:1, 37:1-63:1, 40:1-60:1, 50:1-55:1, and the like.

[0078] In some embodiments, the mass ratio of the aluminum element and the lithium element can be 1.1:1, 1.2:1, 1.31:1, 2:1, 2.2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 9.51:1, 10:1, 11:1, 12:1, 20:1, 21.1:1, 23:1, 25:1, 27:1, 29:1, 30:1, 33:1, 35:1, 37:1, 40:1, 50:1, 55:1, 60:1, 63:1, 66:1, 69:1, 70:1, 75:1, 80:1, 83:1, 85:1, 90:1, 93:1, 95:1, 97.1:1, 98:1, 98.52:1, 99:1, and the like.

[0079] By controlling the mass ratio of the aluminum element and the lithium element to be 1:1-99:1, the lithium content is high, and the effect of continuous lithium supplement can be achieved, and the cycle capacity retention rate is high.

[0080] According to some embodiments of the present application, optionally, the metal element in the current collecting layer further includes at least one of magnesium, vanadium, copper, iron, zinc, tin, nickel, titanium, and manganese.

[0081] By adding at least one of magnesium, vanadium, copper, iron, zinc, tin, nickel, titanium, and manganese, the softness of the current collecting layer can be increased, which is beneficial to winding the pole piece and the separator into the battery cell.

[0082] According to some embodiments of the present application, optionally, the thickness of the current collecting layer is 0.1-3 μm.

[0083] In some embodiments, the thickness of the current collector layer can be 0.11-3 pm, 0.1-2.99 pm, 0.1-2.96 pm, 0.1-2.93 pm, 0.1-2.9 pm, 0.1-2.8 pm, 0.1-2.72 pm, 0.1-2.7 pm, 0.1-2.6 pm, 0.1-2.53 pm, 0.1-2.5 pm, 0.1-2.42 pm, 0.1-2.4 pm, 0.1-2.33 pm, 0.1-2.33 pm, 0.1-2.3 pm, 0.1-2.2 pm, 0.1-2.15 pm, 0.1-2.1 pm, 0.1-2.0 pm, 0.1-1.9 pm, 0.1-1.85 pm, 0.1-1.8 pm, 0.1-1.75 pm, 0.1-1.72 pm, 0.1-1.71 pm, 0.1-1.7 pm, 0.1-1.65 pm, 0.1-1.61 pm, 0.1-1.6 pm, 0.2-1.55 pm, 0.3-1.5 pm, 0.15 pm-3 pm, 0.17 pm-3 pm, 0.2 pm-3 pm, 0.25 pm-3 pm, 0.3 pm-3 pm, 0.4 pm-3 pm, 0.5 pm-3 pm, 0.6 pm-3 pm, 0.7 pm-3 pm, 0.8 pm-3 pm, 0.85 pm-3 pm, 0.9 pm-3 pm, 1.0 pm-3 pm, 1.05 pm-3 pm, 1.07 pm-3 pm, 1.1 pm-3 pm, 1.2 pm-3 pm, 1.25 pm-3 pm, 1.3 pm-3 pm, 1.35 pm-3 pm, 1.4 pm-3 pm, 1.45 pm-3 pm, 1.48 pm-3 pm, 0.5 pm-2 pm, 0.6 pm-2.1 pm, 0.9 pm-2.5 pm, 1.0 pm-2.0 pm, etc.

[0084] In some embodiments, the thickness of the current collector layer can be 0.1 μm, 0.11 μm, 0.15 μm, 0.17 μm, 0.2 μm, 0.25 μm, 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.85 μm, 0.9 μm, 1.0 μm, 1.05 μm, 1.07 μm, 1.1 μm, 1.2 μm, 1.25 μm, 1.3 μm, 1.35 μm, 1.4 μm, 1.45 μm, 1.48 μm, 1.5 μm, 1.55 μm, 1.6 μm, 1.61 μm, 1.65 μm, 1.7 μm, 1.71 μm, 1.72 μm, 1.75 μm, 1.8 μm, 1.85 μm, 1.9 μm, 2.0 μm, 2.1 μm, 2.15 μm, 2.2 μm, 2.3 μm, 2.33 μm, 2.4 μm, 2.42 μm, 2.5 μm, 2.53 μm, 2.6 μm, 2.7 μm, 2.72 μm, 2.8 μm, 2.9 μm, 2.93 μm, 2.96 μm, 2.99 μm, 3 μm, etc.

[0085] Since the effect of supplementing lithium is poor when the thickness of the current collector layer is less than 0.1 μm, and the cost is high when the thickness of the current collector layer is greater than 3 μm, the thickness of the current collector layer is set to 0.1-3 μm to achieve the effects of good supplementing lithium and low cost.

[0086] According to some embodiments of the present application, optionally, the surface of the current collector layer facing the positive electrode material has a pore structure.

[0087] The lithium atoms in the positive electrode material are oxidized into lithium ions into the electrolyte during charging, resulting in the appearance of a pore structure on the surface of the current collector layer. Then, the electrolyte enters the pore structure, so that the lithium atoms of the current collector contact the electrolyte and are oxidized into lithium ions into the electrolyte to continuously supplement the lithium consumed by the negative electrode in the lithium ion battery cycle.

[0088] According to some embodiments of the present application, optionally, the positive electrode material includes at least one of lithium cobaltate, lithium manganate, lithium iron phosphate, and a combination of nickel cobalt manganese.

[0089] Suitable positive electrode materials are conducive to the formation of suitable positive electrode sheets and better achieve the effect of supplementing lithium to improve the cycle performance of the battery.

[0090] According to some embodiments of the present application, the present application provides a preparation method of a positive electrode sheet, providing a substrate, the substrate being an aluminum foil; setting a current collector layer on the surface of the substrate, the current collector layer being a lithium-containing metal, wherein the lithium-containing metal powder slurry or molten slurry is coated on the surface of the substrate; and setting a positive electrode material on the surface of the current collector layer.

[0091] In the technical scheme of the embodiment of the present application, the positive electrode sheet prepared by the preparation method of the positive electrode sheet provided by the present application plays a lithium supplementing role by using the current collector as a lithium-containing metal, and lithium atoms can be oxidized into lithium ions in the charging process to enter the electrolyte to supplement lithium consumed by the formation of the solid electrolyte interphase (SEI) of the lithium ion battery.

[0092] In addition, since the lithium released from the current collector during lithium supplementing is all from the surface layer, the present application can play a lithium supplementing role by arranging a metal layer containing lithium on the surface of the aluminum foil, and the amount of lithium used is reasonable and the cost is low.

[0093] According to some embodiments of the present application, the present application provides a secondary battery including a positive electrode sheet, a negative electrode sheet, and a separator, the separator being arranged between the positive electrode sheet and the negative electrode sheet, and the positive electrode sheet being the positive electrode sheet prepared by any one of the above-mentioned preparation methods of the positive electrode sheet. The secondary battery can be the battery 100 or the battery cell 20 as described above.

[0094] The secondary battery includes a positive electrode sheet, a negative electrode sheet, an electrolyte, and a separator. During the charging and discharging of the battery, active ions are embedded and extracted between the positive electrode sheet and the negative electrode sheet. The electrolyte plays a role in conducting ions between the positive electrode sheet and the negative electrode sheet. The separator is arranged between the positive electrode sheet and the negative electrode sheet, mainly playing a role in preventing short circuiting of the positive and negative electrodes, and at the same time allowing ions to pass through.

[0095] The secondary battery includes a positive electrode sheet, which can play a role in supplementing lithium, realize continuous supplement of consumed lithium ions, and make the battery always maintain a high specific energy, thereby improving the poor cycle performance of the battery and other problems.

[0096] According to some embodiments of the present application, the secondary battery can be a battery module, a battery pack, etc. According to some embodiments of the present application, the present application provides a power utilization device including the secondary battery provided by any one of the above-mentioned embodiments, and the battery is used to provide electric energy for the power utilization device.

[0097] The power utilization device can be a device or system of any one of the above-mentioned application batteries.

[0098] The preparation process and test data are described below:

[0099] Embodiment 1

[0100] S1: Lithium-aluminum alloy preparation: Put the lithium sheet into a nickel crucible, heat and melt at 200℃ in a glove box, pick up the oxide layer on the surface of the molten lithium metal, insert the polished aluminum sheet into the molten lithium, the mass ratio of Li:Al is 1:99, after complete insertion, cool to room temperature, and seal in the glove box and transfer to a high-temperature furnace, perform 700℃ high-temperature reaction in an argon environment, and the reaction is completed after 6h to obtain a lithium-aluminum alloy.

[0101] S2: Preparation of negative electrode sheet: After dry mixing graphite and conductive agent at a ratio of 95:3, deionized water is added to adjust the solid content to 45%-55%, and finally 2% of polymerized styrene butadiene rubber (SBR) binder is added. After stirring uniformly, a negative electrode slurry is obtained, and then the negative electrode sheet is prepared by coating, drying, cold pressing and cutting. Common conductive agents include graphene, acetylene black, super-p, carbon fiber, carbon nanotube, and ketjen black. In this embodiment, super-p is used as the conductive agent. The solid content is generally adjusted to 45%-55%, and in this embodiment, the solid content is adjusted to 50%.

[0102] S3: Preparation of positive electrode sheet: An aluminum foil is used as the substrate, and a current collector layer is arranged on the surface of the substrate. The current collector layer is the lithium-aluminum alloy prepared in step S1. The lithium-aluminum alloy powder slurry or molten slurry is coated on the surface of the aluminum foil to form an aluminum-lithium alloy current collector. After the positive electrode material, conductive carbon and the binder polyvinylidene fluoride (PVDF) are mixed uniformly at a ratio of 96:2.5:1.5, a solvent NMP is added to adjust the solid content to 70%-80%, and then the positive electrode slurry is obtained after stirring uniformly. The positive electrode sheet is prepared by coating, drying, cold pressing and cutting on the aluminum-lithium alloy current collector. The solid content is generally adjusted to 70%-80%, and in this embodiment, the solid content is adjusted to 75%.

[0103] Please refer to Figure 4 , Figure 4 FIG. 4 is a schematic structural diagram of a positive electrode sheet according to some embodiments of the present application. In the positive electrode sheet 400, a current collector layer 402 is arranged on the surface of the substrate 401. The current collector layer 402 is the lithium-aluminum alloy prepared in step S1. The positive electrode material 403 is arranged on the surface of the current collector layer 402.

[0104] S4: The electrode sheets prepared in steps S2 and S3 are wound with a separator to form an electric core, and the electric core is packaged with an aluminum plastic film to form a dry electric core. After processes such as liquid injection and aging, a lithium ion battery is prepared.

[0105] In examples 2 to 20, the preparation method of the positive electrode sheet is consistent with the method of example 1, and the performance test method of the battery is also consistent with the method of example 1. The difference lies in the thickness of the current collector, the thickness of the alloy layer and / or the ratio of lithium-aluminum alloy. The test results are shown in Table 1.

[0106] Comparative example 1

[0107] R1: Preparation of negative electrode sheet: After dry mixing graphite and super-p at a ratio of 95:3, deionized water is added to adjust the solid content to 50%, and finally 2% of polymerized styrene butadiene rubber (SBR) binder is added. After stirring uniformly, a negative electrode slurry is obtained, and then the negative electrode sheet is prepared by coating, drying, cold pressing and cutting.

[0108] R2: Preparation of positive electrode sheet, the positive electrode material, conductive carbon and binder polyvinylidene fluoride (PVDF) were added in the ratio of 96:2.5:1.5, mixed uniformly, then solvent NMP was added to adjust the solid content to 75%, stirred uniformly to obtain positive electrode slurry, and then coated on aluminum foil, dried, cold pressed and cut to prepare positive electrode sheet.

[0109] R3: The electrode sheet prepared in steps R1 and R2 was wound with a separator to form an electric core, and packaged with an aluminum plastic film to form a dry electric core. After liquid injection and aging processes, a lithium ion battery was prepared. A series of performance tests were performed on the prepared lithium ion battery, including battery initial efficiency, battery storage performance test and battery cycle performance test. The test results are shown in Table 1.

[0110] Battery initial efficiency test method: initial efficiency = first discharge capacity / first charge capacity.

[0111] Battery storage performance test method: at 25°C, the secondary batteries prepared in each example and the comparative example were charged at a rate of 1C to a charge cut-off voltage of 4.35V, then charged at a constant voltage to a current of ≤0.05C, and then transferred to a 60°C environment for storage. After 180 days of storage, the electric core was placed in a 25°C environment, charged at a rate of 1C to a charge cut-off voltage of 4.35V, then charged at a constant voltage to a current of ≤0.05C, and then discharged at a rate of 1C to a discharge cut-off voltage of 2.8V. The discharge capacity retention rate after 180 days of storage was recorded.

[0112] Battery cycle performance test method: at 25°C, the secondary batteries prepared in each example and the comparative example were charged at a rate of 1C to a charge cut-off voltage range of 2.8-4.35V, then charged at a constant voltage to a current of ≤0.05C, and then discharged at a rate of 1C to a discharge cut-off voltage of 3.3V. This is one charge-discharge cycle. According to this method, the battery was tested for 1000 cycles of charge-discharge cycles, and the corresponding discharge capacity retention rate was recorded.

[0113] Table 1: Comparison of battery-related properties of each example and the comparative example

[0114]

[0115] Note: In the examples, the thickness of the current collector = the thickness of the substrate + the thickness of the current collecting layer, wherein the thickness of the substrate is 10 μm; in the comparative example, no lithium alloy layer is provided.

[0116] It can be seen from the comparison of the above examples and the comparative examples that the battery prepared from the positive electrode sheet has higher initial efficiency, and the cycle and storage performance of the battery can be improved. The lithium alloy material in the current collector of the positive electrode sheet plays a role of lithium supplement. Lithium atoms can be oxidized into lithium ions in the charging process to enter the electrolyte to supplement the lithium consumed by the formation of solid electrolyte interphase (SEI) in the negative electrode of the lithium ion battery. In addition, since the lithium released from the current collector during lithium supplement all comes from the surface layer, the application can supplement lithium by setting a lithium-containing metal layer on the surface of the aluminum foil, which is reasonable in the amount of lithium used and low in cost. Since the lithium consumed by the formation of solid electrolyte interphase (SEI) in the negative electrode can be continuously supplemented, the battery always maintains good cycle performance and storage performance.

[0117] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the application, but not to limit them; although the application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement to part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the application, and they should be covered in the scope of the claims and the specification of the application. Especially, as long as there is no structural conflict, each technical feature mentioned in each embodiment can be combined in any way. The application is not limited to the specific embodiments disclosed in the text, but includes all technical solutions falling within the scope of the claims.

Claims

1. A positive electrode sheet characterized by comprising: The positive electrode sheet comprises a current collector and a positive electrode material arranged on the current collector, wherein the current collector comprises a substrate and a current collecting layer, the positive electrode material is arranged on the current collecting layer, the substrate is an aluminum foil, and the current collecting layer is a lithium-containing metal.

2. The positive electrode sheet according to claim 1, wherein The current collecting layer is an aluminum-lithium alloy.

3. The positive electrode sheet according to claim 2, wherein In the aluminum-lithium alloy, the mass ratio of aluminum and lithium is 1:1-99:

1.

4. The positive electrode sheet according to claim 2, wherein The metal element in the current collecting layer further comprises at least one of magnesium, vanadium, copper, iron, zinc, tin, nickel, titanium and manganese.

5. The positive electrode sheet according to claim 1, wherein The thickness of the current collecting layer is 0.1-3 μm.

6. The positive electrode sheet according to claim 1, wherein The surface of the current collecting layer towards the positive electrode material has a pore structure.

7. The positive electrode sheet according to claim 1, wherein The positive electrode material comprises at least one of lithium cobaltate, lithium manganate, lithium iron phosphate and a combination of nickel-cobalt-manganese.

8. A method for preparing a positive electrode sheet, comprising: providing a substrate, wherein the substrate is an aluminum foil; arranging a current collecting layer on the surface of the substrate, wherein the current collecting layer is a lithium-containing metal, and the lithium-containing metal is coated on the surface of the substrate in the form of a powder slurry or a molten slurry; and arranging a positive electrode material on the surface of the current collecting layer.

9. A secondary battery characterized by comprising: A secondary battery comprising the positive electrode sheet, a negative electrode sheet and a separator arranged between the positive electrode sheet and the negative electrode sheet, wherein the positive electrode sheet is the positive electrode sheet according to any one of claims 1-7 or is prepared by the method according to claim 8.

10. An electrical device, characterized by A secondary battery according to claim 9.

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