Positive pole piece, battery and electric device

Abstract

The invention provides a positive pole piece, a battery and a power utilization device, and relates to the field of batteries. The positive pole piece comprises a current collector, and a first positive active material layer and a second positive active material layer which are stacked on the current collector; the first positive electrode active material layer comprises an olivine structure phosphate material, the second positive electrode active material layer comprises a layered transition metal oxide and an additive, the additive comprises a flexible polymer matrix, the crystallinity of the flexible polymer matrix is 10%-60%, the liquid absorption swelling rate of the flexible polymer matrix in an electrolyte at 20-30 DEG C is 50%-500%, and the liquid absorption swelling rate of the flexible polymer matrix in the electrolyte at 20-30 DEG C is 50%-500%. The capacity retention ratio of the battery after circulation can be improved.

Description

Technical Field

[0001] The present application relates to the field of batteries, and in particular to a positive electrode sheet, a battery and an electrical device. Background Art

[0002] As the market demands high energy density, excellent cycle life, and high safety performance of batteries, batteries that use only olivine-structured lithium iron phosphate as the positive electrode active material or ternary batteries that use layered transition metal oxides as the positive electrode active material cannot meet the above performance. Therefore, olivine-structured phosphate materials and layered transition metal oxides are usually mixed in the hope of improving the overall performance of the battery. However, there is a problem of low capacity retention rate after cycling during actual use. Summary of the invention

[0003] In view of the above problems, the present application proposes a positive electrode plate, a battery and an electrical device, which can improve the technical problem of low capacity retention rate of batteries containing positive electrode plates containing olivine structure phosphate materials and layered transition metal oxides after cycling.

[0004] In a first aspect, an embodiment of the present application provides a positive electrode plate, which includes a current collector, and a first positive electrode active material layer and a second positive electrode active material layer stacked on the current collector; the first positive electrode active material layer includes an olivine structure phosphate material, and the second positive electrode active material layer includes a layered transition metal oxide and an additive, the additive includes a flexible polymer matrix, the crystallinity of the flexible polymer matrix is ​​10%-60%, and the liquid absorption swelling rate of the flexible polymer matrix in an electrolyte at 20-30°C is 50%-500%.

[0005] In the technical solution of the embodiment of the present application, a flexible polymer matrix is ​​added to the second positive electrode active material layer. Since the crystallinity of the flexible polymer matrix is ​​10%-60%, and the liquid absorption swelling rate of the flexible polymer matrix in the electrolyte at 20-30°C is 50%-500%, in a battery containing the above-mentioned positive electrode plate, the flexible polymer matrix can absorb the electrolyte and form a gel polymer electrolyte with the electrolyte immersed in the flexible polymer matrix, thereby improving the ionic conductivity of the second positive electrode active material layer, preventing the over-discharge of the layered transition metal oxide caused by the excessive difference in ion concentration between the interface of the second positive electrode active material layer and the interior of the second positive electrode active material layer, reducing the phase change at the interface of the second positive electrode active material layer, and thus improving the cycle capacity retention rate of the battery.

[0006] In some embodiments, the olivine structure phosphate material includes Li a Fe b M 1-b P 1-m O 4-n, wherein M includes at least one of other metal elements except Fe, wherein 0<a≤1.1, 0≤b≤1, 0≤m≤0.1, 0≤n≤0.1.

[0007] Optionally, M includes at least one of Mn, Al, Cu, Mg, Zn, Ni, Ti, V, Zr, Co, Ga, Sn, Sb, Nb and Ge.

[0008] Optionally, the olivine structure phosphate material includes at least one of lithium iron phosphate and lithium manganese iron phosphate.

[0009] In some embodiments, the layered transition metal oxide includes LiCoO2, LiMnO2, LiNiO2, Li a Ni x Co y M1 1-x-y O 2+d , z Li2MnO3 (1-z) At least one of LiM2O2, wherein M1 includes at least one of Mn, Zr, Al, B, Ta, Mo, W, Nb, Sb, and La, and M2 includes at least one of Co, Ni, and Mn, 0.5≤x≤1.0, 0≤y<0.5, x+y<1, 0.2≤a'<1.2, -0.02≤d<0.02, and 0<z<1;

[0010] Optionally, the layered transition metal oxide includes at least one of lithium cobalt oxide, lithium nickel oxide, lithium-rich material, nickel-cobalt-manganese ternary material and manganese-cobalt-aluminum ternary material.

[0011] In some embodiments, the amount of the olivine structure phosphate material added to the first positive electrode active material layer is 90%-99%; and / or the amount of the layered transition metal oxide added to the second positive electrode active material layer is 90%-99%. Within the above range, the battery has a high energy density and good cycle stability.

[0012] In some embodiments, the mass percentage of the additive in the second positive electrode active material layer is 0.5%-23%, and can be 3%-23%. By controlling the amount of additive added within the above range, the amount of gel polymer electrolyte in the final battery is controlled within a reasonable range, which is conducive to reducing the difference between the ionic conductivity of the layered transition metal oxide and the electronic conductivity of the olivine structure phosphate material, preventing the layered transition metal oxide from being over-discharged, reducing the phase change at the interface of the second positive electrode active material layer, and effectively improving the cycle capacity retention rate and the cycle life.

[0013] In some embodiments, the additive is a solid electrolyte, which includes a flexible polymer matrix and an electrolyte salt. Since the solid electrolyte contains a flexible polymer matrix, it can absorb the electrolyte and form a gel polymer electrolyte after being assembled into a battery, effectively improving the ionic conductivity of the second positive electrode active material layer so that the ionic conductivity and electronic conductivity of the two positive electrode active material layers match, thereby improving the cycle capacity retention rate.

[0014] Optionally, the electrolyte salt is an alkaline salt, optionally a lithium salt or a sodium salt.

[0015] In some embodiments, in the solid electrolyte, the mass ratio of the flexible polymer matrix to the electrolyte salt is (2:95)-(40:60), and can be (10:90)-(40:60). The solid electrolyte obtained within the above range can effectively improve the cycle capacity retention rate of the battery.

[0016] In some embodiments, the additive is a flexible polymer matrix. Under the above-mentioned setting conditions, the positive electrode plate is immersed in the electrolyte, and the electrolyte is immersed in the flexible polymer matrix to form a gel polymer electrolyte, which can form a good interface contact with the positive electrode active material, etc., and can improve the ionic conductivity of the second positive electrode active material layer, so that the ionic conductivity and electronic conductivity of the two positive electrode active material layers match, and improve the cycle capacity retention rate of the battery.

[0017] In some embodiments, the flexible polymer matrix includes one or more of polyethylene oxide, polyethylene glycol, polyvinyl pyrrolidone, polymethyl methacrylate, polyvinylidene fluoride, polyvinyl alcohol, polyacrylonitrile, polyvinyl chloride, polyacrylamide, polytrimethylene carbonate, perfluoropolyether, and poly(vinylidene fluoride-co-hexafluoropropylene) copolymer.

[0018] Optionally, the flexible polymer matrix includes one or more of polyethylene oxide, polyethylene glycol, perfluoropolyether, and poly(vinylidene fluoride-co-hexafluoropropylene) copolymer.

[0019] The above-mentioned flexible polymer matrix is ​​not only easy to obtain, but also the formed gel polymer electrolyte has better lithium ion conductivity, which is beneficial to improving the cycle capacity retention rate of the battery.

[0020] In some embodiments, the first positive electrode active material layer is located between the second positive electrode active material layer and the current collector. The above arrangement is beneficial to shortening the lithium insertion and extraction path of the layered transition metal oxide and improving the cycle stability of the battery.

[0021] In a second aspect, the present application provides a battery, which includes an electrolyte and the positive electrode plate in the above embodiment.

[0022] In a third aspect, the present application provides an electrical device, which includes the battery in the above embodiment, and the battery is used to provide electrical energy.

[0023] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the detailed description of the preferred embodiments below. The accompanying drawings are only for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the present application. Moreover, the same reference numerals are used throughout the drawings to represent the same components. In the drawings:

[0025] Figure 1 A schematic diagram of the structure of a vehicle according to some embodiments of the present application;

[0026] Figure 2 A schematic diagram of the exploded structure of a battery according to some embodiments of the present application;

[0027] Figure 3 A schematic diagram of the exploded structure of a battery cell according to some embodiments of the present application;

[0028] Figure 4 This is a schematic diagram of the structure of the positive electrode sheet of some embodiments of the present application;

[0029] Figure 5 This is a schematic diagram of the structure of the positive electrode plate of some embodiments of the present application.

[0030] The reference numerals in the specific implementation manner are as follows:

[0031] 1000-Vehicles;

[0032] 100-battery; 200-controller; 300-motor;

[0033] 10-box; 11-first part; 12-second part;

[0034] 20-battery cell; 21-end cover; 21a-electrode terminal; 22-housing; 23-electrode assembly; 23a-electrode ear;

[0035] 30 - positive electrode sheet; 31 - current collector; 32 - first positive electrode active material layer; 33 - second positive electrode active material layer. DETAILED DESCRIPTION

[0036] The following embodiments of the technical solution of the present application are described in detail in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present application, and are therefore only used as examples, and cannot be used to limit the scope of protection of the present application.

[0037] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by technicians in the technical field to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" in the specification and claims of this application and the above-mentioned figure descriptions and any variations thereof are intended to cover non-exclusive inclusions.

[0038] 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 "multiple" is more than two, unless otherwise clearly and specifically defined.

[0039] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0040] 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, indicating that there may be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0041] In the description of the embodiments of the present application, the term "multiple" refers to more than two (including two). Similarly, "multiple groups" refers to more than two groups (including two groups), and "multiple pieces" refers to more than two pieces (including two pieces).

[0042] In the description of the embodiments of the present application, the technical terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, which 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 referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the embodiments of the present application.

[0043] In the description of the embodiments of the present application, unless otherwise clearly specified and limited, technical terms such as "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, and it can be the internal connection of two elements or the interaction relationship between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the embodiments of the present application can be understood according to the specific circumstances.

[0044] At present, from the perspective of market development, the application of batteries is becoming more and more extensive. Batteries are not only used in energy storage power systems such as hydropower, thermal power, wind power and solar power stations, but also widely used in electric vehicles such as electric bicycles, electric motorcycles, electric cars, as well as military equipment and aerospace and other fields. With the continuous expansion of battery application areas, its market demand is also constantly expanding.

[0045] Based on the market's requirements for high energy density, excellent cycle life, and high safety performance of batteries, olivine-structured phosphate materials and layered transition metal oxides are usually mixed in the hope of improving the overall performance of the battery. However, in actual use, there is a technical problem of low capacity retention rate after cycling. Even if the two are layered, although the above problems can be improved to a certain extent compared to direct physical mixing, the battery's cycle capacity retention rate is still low and needs to be further improved.

[0046] The main reason for the above technical problems is that the ionic conductivity of the layered transition metal oxide does not match the electronic conductivity of the olivine structure phosphate material. On the one hand, it causes lithium ions to be easily enriched on the surface of the layered transition metal oxide, resulting in over-discharge of the layered transition metal oxide. On the other hand, it causes too large a difference in ion concentration between the interface of the second positive electrode active material layer and the interior of the second positive electrode active material layer, resulting in more phase changes at the interface of the second positive electrode active material layer, resulting in a decrease in the cycle capacity retention rate.

[0047] Therefore, in order to improve the technical problem of low capacity retention rate after cycling in batteries using positive electrode plates containing positive electrode active materials with different electrical conductivities, the present application adopts a method of stacking a first positive electrode active material layer and a second positive electrode active material layer on a current collector; the first positive electrode active material layer includes an olivine structure phosphate material, the second positive electrode active material layer includes a layered transition metal oxide and an additive, the additive includes a flexible polymer matrix, the crystallinity of the flexible polymer matrix is ​​10%-60%, and the liquid absorption swelling rate of the flexible polymer matrix in the electrolyte at 20-30°C is 50%-500%.

[0048] It should be noted that when the positive electrode is used in the battery, a certain porosity needs to be maintained to ensure that the electrolyte can infiltrate into the inside of the electrode, thereby conducting the ion path. When the porosity is too large, the contact between the particles inside the electrode material is not close, the lithium ion and electron transmission path is long, the resistance is large, and a large part of the energy is lost. If the porosity is too small, the electrolyte infiltration is difficult, which will also cause negative effects, resulting in poor battery cycle life and rate performance. Therefore, this application uses additives to add to the second positive electrode active material layer. Since the crystallinity of the flexible polymer matrix in the additive is 10%-60%, the liquid absorption swelling rate of the flexible polymer matrix in the electrolyte at 20-30°C is 50%-5 00%, therefore, in a battery containing the above-mentioned positive electrode plate, the flexible polymer matrix can absorb the electrolyte and form a gel polymer electrolyte with the electrolyte immersed in the flexible polymer matrix, and the electrolyte is adsorbed by the additive to swell to form a gel electrolyte to fill the pores, reduce the porosity, shorten the lithium ion and electron transmission path, and make the positive electrode active material in close contact with the gel electrolyte, reduce the interface resistance, achieve high interface conductivity, effectively improve the ion conductivity of the second positive electrode active material layer, avoid excessive difference in ion concentration at the interface of the second positive electrode active material layer and inside the second positive electrode active material layer, reduce the phase change at the interface of the second positive electrode active material layer, and improve the battery's cycle capacity retention rate.

[0049] The battery disclosed in the embodiment of the present application can be used in, but not limited to, electrical devices such as vehicles, ships or aircraft. A power supply system comprising the battery disclosed in the present application can be used to form the electrical device, which is conducive to improving the capacity retention rate of the battery using the positive electrode sheet containing olivine structure phosphate material and layered transition metal oxide after cycling and improving the cycle life.

[0050] The embodiment of the present application provides an electric device using a battery as a power source, and the electric device may be, but is not limited to, a mobile phone, a tablet, a laptop, an electric toy, an electric tool, a battery car, an electric car, a ship, a spacecraft, etc. Among them, the electric toy may include a fixed or mobile electric toy, such as a game console, an electric car toy, an electric ship toy, and an electric airplane toy, etc., and the spacecraft may include an airplane, a rocket, a space shuttle, and a spacecraft, etc.

[0051] For the convenience of description, the following embodiments are described by taking a vehicle 1000 as an example of an electrical device according to an embodiment of the present application.

[0052] Please refer to Figure 1 , Figure 1 A schematic diagram of the structure of a vehicle 1000 provided for some embodiments of the present application. The vehicle 1000 may be a fuel vehicle, a gas vehicle or a new energy vehicle, and the new energy vehicle may be a pure electric vehicle, a hybrid vehicle or an extended-range vehicle, etc. A battery 100 is provided inside the vehicle 1000, and the battery 100 may be provided at the bottom, head or tail of the vehicle 1000. The battery 100 may be used to power the vehicle 1000, for example, the battery 100 may be used as an operating power source for the vehicle 1000. The vehicle 1000 may also include a controller 200 and a motor 300, and the controller 200 is used to control the battery 100 to power the motor 300, for example, for starting, navigating and driving the vehicle 1000.

[0053] In some embodiments of the present application, the battery 100 can not only serve as an operating power source for the vehicle 1000, but also serve as a driving power source for the vehicle 1000, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle 1000.

[0054] In the present application, the battery 100 refers to a single physical module including one or more battery cells 20 to provide a certain voltage and capacity, which may be in the form of a battery pack, a battery module, etc. The battery 100 may also include a box 10 for encapsulating one or more battery cells 20, and the box 10 may prevent liquid or other foreign matter from affecting the charging or discharging of the battery cells 20.

[0055] Please refer to Figure 2 , Figure 2An exploded view of a battery 100 provided in some embodiments of the present application. The battery 100 includes a housing 10 and a battery cell 20, and the battery cell 20 is contained in the housing 10. The housing 10 is used to provide a storage space for the battery cell 20, and the housing 10 can adopt a variety of structures. In some embodiments, the housing 10 can include a first part 11 and a second part 12, and the first part 11 and the second part 12 cover each other, and the first part 11 and the second part 12 jointly define a storage space for accommodating the battery cell 20. The second part 12 can be a hollow structure with one end open, and the first part 11 can be a plate-like structure, and the first part 11 covers the open side of the second part 12, so that the first part 11 and the second part 12 jointly define a storage space; the first part 11 and the second part 12 can also be hollow structures with one side open, and the open side of the first part 11 covers the open side of the second part 12. Of course, the housing 10 formed by the first part 11 and the second part 12 can be in a variety of shapes, such as a cylinder, a cuboid, etc.

[0056] In the battery 100, there may be multiple battery cells 20, and the multiple battery cells 20 may be connected in series, in parallel, or in a mixed connection. A mixed connection means that the multiple battery cells 20 are both connected in series and in parallel. The multiple battery cells 20 may be directly connected in series, in parallel, or in a mixed connection, and then the whole formed by the multiple battery cells 20 is accommodated in the box 10; of course, the battery 100 may also be a battery module formed by connecting multiple battery cells 20 in series, in parallel, or in a mixed connection, and then the multiple battery modules are connected in series, in parallel, or in a mixed connection to form a whole, and accommodated in the box 10. The battery 100 may also include other structures, for example, the battery 100 may also include a busbar component for realizing electrical connection between the multiple battery cells 20.

[0057] Each battery cell 20 may be a secondary battery or a primary battery. The battery cell 20 may be cylindrical, flat, rectangular or in other shapes.

[0058] Please refer to Figure 3 , Figure 3 The schematic diagram of the exploded structure of the battery cell 20 provided in some embodiments of the present application. The battery cell 20 refers to the smallest unit that constitutes the battery. Figure 3 The battery cell 20 includes an end cover 21, a shell 22, an electrode assembly 23 and other functional components.

[0059] The end cap 21 refers to a component that covers the opening of the shell 22 to isolate the internal environment of the battery cell 20 from the external environment. Without limitation, the shape of the end cap 21 can be adapted to the shape of the shell 22 to match the shell 22. Optionally, the end cap 21 can be made of a material with a certain hardness and strength (such as aluminum alloy), so that the end cap 21 is not easily deformed when squeezed and collided, so that the battery cell 20 can have a higher structural strength and the safety performance can also be improved. Functional components such as electrode terminals 21a can be provided on the end cap 21. The electrode terminal 21a can be used to electrically connect to the electrode assembly 23 for outputting or inputting electrical energy of the battery cell 20. In some embodiments, the end cap 21 can also be provided with a pressure relief mechanism for releasing the internal pressure when the internal pressure or temperature of the battery cell 20 reaches a threshold. The material of the end cap 21 can also be a variety of materials, such as copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc., and the embodiments of the present application do not impose special restrictions on this. In some embodiments, an insulating member may be provided inside the end cap 21, and the insulating member may be used to isolate the electrical connection components in the housing 22 from the end cap 21 to reduce the risk of short circuit. For example, the insulating member may be plastic, rubber, or the like.

[0060] The shell 22 is a component used to cooperate with the end cap 21 to form the internal environment of the battery cell 20, wherein the formed internal environment can be used to accommodate the electrode assembly 23, the electrolyte and other components. The shell 22 and the end cap 21 can be independent components, and an opening can be set on the shell 22, and the internal environment of the battery cell 20 is formed by covering the opening with the end cap 21 at the opening. Without limitation, the end cap 21 and the shell 22 can also be integrated. Specifically, the end cap 21 and the shell 22 can form a common connection surface before other components are put into the shell, and when the interior of the shell 22 needs to be encapsulated, the end cap 21 covers the shell 22. The shell 22 can be of various shapes and sizes, such as a rectangular parallelepiped, a cylindrical shape, a hexagonal prism, etc. Specifically, the shape of the shell 22 can be determined according to the specific shape and size of the electrode assembly 23. The material of the shell 22 can be various, such as copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc., and the embodiment of the present application does not impose any special restrictions on this.

[0061] The electrode assembly 23 is a component in the battery cell 20 where electrochemical reactions occur. One or more electrode assemblies 23 may be included in the housing 22. The electrode assembly 23 is mainly formed by winding or stacking positive and negative electrode sheets, and a separator is usually provided between the positive and negative electrode sheets. The parts of the positive and negative electrode sheets with active materials constitute the main body of the electrode assembly, and the parts of the positive and negative electrode sheets without active materials each constitute a tab 23a. The positive tab and the negative tab may be located together at one end of the main body or respectively at both ends of the main body. During the charge and discharge process of the battery, the positive active material and the negative active material react with the electrolyte, and the tab 23a connects the electrode terminals to form a current loop.

[0062] See also Figure 4 as well as Figure 5 According to some embodiments of the present application, the positive electrode plate 30 includes a current collector 31, and a first positive electrode active material layer 32 and a second positive electrode active material layer 33 stacked on the current collector 31; the first positive electrode active material layer 32 includes an olivine structure phosphate material, and the second positive electrode active material layer 33 includes a layered transition metal oxide and an additive, and the additive includes a flexible polymer matrix, the crystallinity of the flexible polymer matrix is ​​10%-60%, and the liquid absorption swelling rate of the flexible polymer matrix in the electrolyte at 20-30°C is 50%-500%.

[0063] The current collector 31 may be a metal foil or a composite current collector. For example, as the metal foil, a copper foil or an aluminum foil may be used. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0064] The positive electrode active material layer refers to the film layer containing the positive electrode active material for reacting with the electrolyte during the charge and discharge process of the battery. In addition to the positive electrode active material, the positive electrode active material layer may also generally contain a binder and a conductive agent. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer and fluorine-containing acrylate resin. As an example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.

[0065] Crystallinity is used to indicate the proportion of crystalline regions in a flexible polymer matrix. Polymer crystallinity can be measured using DSC by quantifying the heat associated with polymer melting. The heat can be estimated as a percentage of crystallinity by comparing it to a polymer of known crystallinity to obtain a relative value, or by comparing it to the heat of fusion of a 100% crystalline polymer sample.

[0066] Swelling is the phenomenon that the volume of the flexible polymer matrix expands in the electrolyte. The mass of the flexible polymer matrix after swelling equilibrium in the electrolyte is W1, the mass after drying in the vacuum oven is W0, and the swelling ratio SW = (W1-W0) / W0*100%. When the volume of the flexible polymer matrix no longer changes when immersed in the electrolyte, swelling equilibrium is reached.

[0067] In the technical solution of the embodiment of the present application, due to the large difference in the electrical conductivity of the olivine-structured phosphate material and the layered transition metal oxide, a layered setting is adopted. Compared with direct physical mixing, the phase change is mainly concentrated at the interface between the two layers of positive electrode active material layers to reduce the phase change, which is beneficial to improving the cycle capacity retention rate of the battery containing the positive electrode plate.

[0068] A flexible polymer matrix is ​​added to the second positive electrode active material layer 33. Since the crystallinity of the flexible polymer matrix is ​​10%-60%, and the liquid absorption swelling rate of the flexible polymer matrix in the electrolyte at 20-30°C is 50%-500%, in a battery containing the above-mentioned positive electrode plate, the flexible polymer matrix can absorb the electrolyte and form a gel polymer electrolyte with the electrolyte immersed in the flexible polymer matrix, thereby improving the ionic conductivity of the second positive electrode active material layer 33, preventing the over-discharge of the layered transition metal oxide caused by the excessive difference in ion concentration between the interface of the second positive electrode active material layer 33 and the inside of the second positive electrode active material layer 33, reducing the phase change at the interface of the second positive electrode active material layer 33, and thus improving the cycle capacity retention rate of the battery.

[0069] The current collector 31 has two opposite surfaces. In some embodiments, a first positive electrode active material layer 32 and a second positive electrode active material layer 33 are sequentially disposed on one surface of the current collector 31 .

[0070] like Figure 4 as well as Figure 5 As shown, in some embodiments, a first positive electrode active material layer 32 and a second positive electrode active material layer 33 are sequentially disposed on both surfaces of the current collector 31 .

[0071] Optionally, the thickness of the first positive electrode active material layer 32 is 40-200 μm, and the thickness of the second positive electrode active material layer 33 is 40-200 μm. Within the above range, the battery 100 has a good energy density and a good cycle retention rate.

[0072] According to some embodiments of the present application, the olivine structure phosphate material includes Li a Fe b M 1-b P 1-m O 4-n , wherein M includes at least one of other metal elements except Fe, wherein 0<a≤1.1, 0≤b≤1, 0≤m≤0.1, 0≤n≤0.1.

[0073] Optionally, M includes at least one of Mn, Al, Cu, Mg, Zn, Ni, Ti, V, Zr, Co, Ga, Sn, Sb, Nb and Ge.

[0074] Exemplarily, olivine structure phosphate materials include but are not limited to LiFePO4, LiMn 0.1 Fe 0.9 PO4、LiMn 0.2 Fe 0.8 PO4、LiMn 0.3 Fe 0.7 PO4、LiMn 0.4 Fe 0.6 PO4、LiMn 0.5 Fe 0.5 PO4、LiMn 0.6 Fe 0.4 PO4、LiMn 0.7 Fe 0.3 PO4、LiMn 0.8 Fe 0.2 PO4、LiMn 0.9 Fe 0.1 PO4, LiMnPO4, etc.

[0075] Optionally, the olivine structure phosphate material includes at least one of lithium iron phosphate and lithium manganese iron phosphate.

[0076] According to some embodiments of the present application, the layered transition metal oxide includes LiCoO2, LiMnO2, LiNiO2, Li a Ni x Co y M1 1-x-y O 2+d , z Li2MnO3 (1-z) At least one of LiM2O2, wherein M1 includes at least one of Mn, Zr, Al, B, Ta, Mo, W, Nb, Sb, and La, and M2 includes at least one of Co, Ni, and Mn, 0.5≤x≤1.0, 0≤y<0.5, x+y<1, 0.2≤a<1.2, -0.02≤d<0.02, and 0<z<1.

[0077] Optionally, the layered transition metal oxide includes at least one of lithium cobalt oxide, lithium nickel oxide, lithium-rich material, nickel-cobalt-manganese ternary material and manganese-cobalt-aluminum ternary material.

[0078] The above-mentioned layered transition metal oxides have high specific capacity and high voltage platform, which can improve the energy density of the battery.

[0079] It should be noted that the battery will be accompanied by Li deintercalation and consumption during the charging and discharging process, and the molar content of Li is different when the battery is discharged to different states. In the list of positive electrode materials in this application, the molar content of Li is the initial state of the material, that is, the state before feeding. The positive electrode material is used in the battery system, and the molar content of Li will change after the charge and discharge cycle. In the list of positive electrode materials in this application, the molar content of O is only a theoretical state value. The release of oxygen from the lattice will cause the molar content of oxygen to change, and the actual molar content of O will fluctuate.

[0080] In some embodiments, the amount of the olivine structured phosphate material added to the first positive electrode active material layer 32 is 90%-99%; and / or the amount of the layered transition metal oxide added to the second positive electrode active material layer 33 is 90%-99%.

[0081] Within the above range, the battery has high energy density and good cycle stability.

[0082] Exemplarily, the amount of olivine-structured phosphate material added to the first positive electrode active material layer 32 is any one of 90%, 91%, 93%, 95%, 97%, 99% or between any two values, and the amount of layered transition metal oxide added to the second positive electrode active material layer 33 is any one of 90%, 91%, 93%, 95%, 97%, 99% or between any two values.

[0083] According to some embodiments of the present application, the mass percentage of the additive in the second positive electrode active material layer 33 is 0.5%-23%.

[0084] By controlling the amount of additives added within the above range, not only the battery energy density is improved, but it is also beneficial to reduce the difference in conductivity between the two positive electrode active material layers, reduce the difference in ion concentration at the interface of the second positive electrode active material layer 33 and inside the second positive electrode active material layer, and effectively improve the cycle capacity retention rate and the cycle life.

[0085] Illustratively, the mass percentage of the additive in the second positive electrode active material layer 33 is any value among 0.5%, 1%, 3%, 5%, 7%, 10%, 13%, 15%, 17%, 20%, 23% or between any two values.

[0086] Optionally, the mass percentage of the additive in the second positive electrode active material layer 33 is 3%-23%.

[0087] Among them, see Figure 4 as well as Figure 5 The preparation method of the positive electrode sheet 30 includes: obtaining a first slurry for preparing a first positive electrode active material layer 32 and a second slurry for preparing a second positive electrode active material layer 33, placing the first slurry and the second slurry at defined positions according to the positions of the first positive electrode active material layer 32 and the second positive electrode active material layer 33 in the upper and lower directions, and then applying the two layers of slurry to the current collector 31 in a synchronous or stepwise manner, and then drying and cold pressing to obtain the positive electrode sheet 30. The additive is uniformly dispersed in the second positive electrode active material layer 33.

[0088] Exemplarily, the first slurry includes, by mass percentage, 90%-99% olivine structure phosphate material, 0.1%-2% conductive agent and 0.5%-1% binder; the second slurry includes 76%-98.5% layered transition metal oxide, 0.1%-20% additive, 0.1%-2% conductive agent and 1%-2% binder.

[0089] According to some embodiments of the present application, the additive is a solid electrolyte, and the solid electrolyte includes a flexible polymer matrix and an electrolyte salt.

[0090] The solid electrolyte has the characteristics of light weight and flexibility, and is easy to form a good interface contact with the positive electrode active material, etc., and has good tensile strength and ionic conductivity. It can be understood that the above-mentioned solid electrolyte is directly added to the slurry used to prepare the second positive electrode active material layer 33 during the process of preparing the positive electrode plate, and the solid electrolyte can be a mixture of a flexible polymer matrix and an electrolyte salt directly mixed.

[0091] Optionally, the electrolyte salt is an alkali metal salt.

[0092] It is understandable that the electrolyte salt varies according to the type of battery. Optionally, the electrolyte salt is a lithium salt or a sodium salt. When the battery is a lithium ion battery, the electrolyte salt is a lithium salt, and when the battery is a sodium ion battery, the electrolyte is a sodium salt.

[0093] The lithium salt includes but is not limited to at least one of LiPF6, LiClO4, LiTFSI, LiFSI, LiBOB, and LiODFB.

[0094] The sodium salt includes but is not limited to at least one of sodium bis(trifluoromethanesulfonyl)imide, sodium borohydride, and sodium tetrafluoroborate.

[0095] According to some embodiments of the present application, in the solid electrolyte, the mass ratio of the flexible polymer matrix to the electrolyte salt is (2:95)-(40:60).

[0096] The solid electrolyte obtained within the above range can effectively improve the cycle capacity retention rate of the battery.

[0097] Illustratively, the mass ratio of the flexible polymer matrix to the electrolyte salt is any one of 2:95, 2.5:100, 5:100, 10:100, 25:100, 30:100, 35:100, 40:100, 30:70, 40:60 or between any two values.

[0098] According to some embodiments of the present application, the additive is a flexible polymer matrix.

[0099] That is, in the process of preparing the positive electrode sheet, the flexible polymer matrix is ​​directly added to the slurry for preparing the second positive electrode active material layer 33 , and then coated to form a film.

[0100] Under the above-mentioned setting conditions, the positive electrode plate is immersed in the electrolyte, the electrolyte penetrates into the flexible polymer matrix and forms a gel polymer electrolyte, and the gel polymer electrolyte can form a good interface contact with the positive electrode active material, etc., and can improve the ionic conductivity of the second positive electrode active material layer 33, reduce the difference in ion concentration at the interface of the second positive electrode active material layer 33 and inside the second positive electrode active material layer 33, and improve the battery's cycle capacity retention rate.

[0101] According to some embodiments of the present application, the flexible polymer matrix includes one or more of polyethylene oxide, polyethylene glycol, polyvinyl pyrrolidone, polymethyl methacrylate, polyvinylidene fluoride, polyvinyl alcohol, polyacrylonitrile, polyvinyl chloride, polyacrylamide, polytrimethylene carbonate, perfluoropolyether, and poly(vinylidene fluoride-co-hexafluoropropylene) copolymer.

[0102] Optionally, the flexible polymer matrix includes one or more of polyethylene oxide, polyethylene glycol, perfluoropolyether, and poly(vinylidene fluoride-co-hexafluoropropylene) copolymer.

[0103] The above-mentioned flexible polymer matrices are not only easy to obtain, but also the formed gel polymer electrolyte has better lithium ion conductivity, which is beneficial to improving the cycle capacity retention rate of the battery.

[0104] Among them, Figure 4 The first positive electrode active material layer 32 can be located on the side of the second positive electrode active material layer 33 close to the current collector 31, or can be located on the side of the second positive electrode active material layer 33 close to the current collector 31. Figure 5 The illustrated embodiment is located on the side of the second positive electrode active material layer 33 facing away from the current collector 31 .

[0105] See also Figure 4 According to some embodiments of the present application, the first positive electrode active material layer 32 is located between the second positive electrode active material layer 33 and the current collector 31 .

[0106] Since the first positive electrode active material layer 32 includes an olivine structure phosphate material and the second positive electrode active material layer 33 includes a layered transition metal oxide, the above arrangement is beneficial to shortening the lithium insertion and extraction path of the layered transition metal oxide and is beneficial to improving the cycle stability of the battery.

[0107] According to some embodiments of the present application, the present application also provides a battery, comprising an electrolyte and a positive electrode plate of any of the above schemes.

[0108] The electrolyte contains electrolyte salt, and the electrolyte salt varies according to the type of battery. For example, when the battery is a lithium-ion battery, the electrolyte salt is lithium salt. At this time, since the battery contains electrolyte, after the positive electrode plate and the remaining components are assembled and the electrolyte is injected to form a battery, the positive electrode plate is immersed in the electrolyte and the flexible polymer matrix absorbs the electrolyte containing the electrolyte salt to form a gel polymer electrolyte. The gel polymer electrolyte can not only form a good interface contact with the positive electrode active material, etc., but also improve the ionic conductivity of the second positive electrode active material layer, reduce the difference in ion concentration at the interface of the second positive electrode active material layer and inside the second positive electrode active material layer, reduce the phase change at the interface of the second positive electrode active material layer, and improve the battery's cycle capacity retention rate.

[0109] According to some embodiments of the present application, the present application further provides an electrical device, comprising a battery according to any of the above schemes, and the battery is used to provide electrical energy to the electrical device.

[0110] The power-consuming device may be any of the aforementioned devices or systems using batteries.

[0111] According to some embodiments of the present application, see 3 to Figure 4 The present application provides a positive electrode sheet 30, which includes a current collector 31, and a first positive electrode active material layer 32 and a second positive electrode active material layer 33 stacked on the current collector 31, wherein the first positive electrode active material layer 32 is located on the side of the second positive electrode active material layer 33 close to the current collector 31. The first positive electrode active material layer 32 includes an olivine structure phosphate material, and the second positive electrode active material layer 33 includes a layered transition metal oxide and a flexible polymer matrix, wherein the crystallinity of the flexible polymer matrix is ​​10%-60%, and the liquid absorption swelling rate of the flexible polymer matrix in the electrolyte at 20-30°C is 50%-500%. The mass percentage of the flexible polymer matrix in the second positive electrode active material layer 33 is 0.1%-20%.

[0112] Some specific embodiments are listed below to better illustrate the present application.

[0113] Examples and Comparative Examples

[0114]

Preparation of positive electrode

[0115] The steps for preparing the positive electrode sheet of Example 1 include:

[0116] Prepare the first coating slurry: weigh LITFSI and PEO at a mass ratio of 10:90 to obtain a solid electrolyte, add LiNiCoMnO2 material, conductive carbon black, PVDF and solid electrolyte to NMP at a mass ratio of 96:0.5:0.5:3, and prepare a slurry after stirring.

[0117] Prepare the second coating slurry: add LiFePO4, conductive carbon black and PVDF into NMP at a mass ratio of 97.5:1:1.5, and prepare into slurry after stirring.

[0118] Preparation of positive electrode sheet: Use extrusion coating to coat the first / second layer slurry of step 1 on the current collector simultaneously or in steps, dry and cold press to obtain the positive electrode sheet.

[0119] The first positive electrode active material layer is located between the second positive electrode active material layer and the current collector, the thickness of the first positive electrode active material layer is 80 μm, and the thickness of the second positive electrode active material layer is 80 μm.

[0120] The main parameter controls of Examples 2-10, 12-14 and Comparative Examples 1-4 and Example 1 are shown in Table 1.

[0121] The only difference between Example 11 and Example 1 is that the second positive electrode active material layer is located between the first positive electrode active material layer and the current collector.

[0122] The preparation method of the positive electrode sheet in Comparative Example 1 is different from that in Example 1 only in that LiFePO4 and LiNiCoMnO2 are mixed at a mass ratio of 1:1 as a mixed positive electrode active material, and the mixed positive electrode active material, conductive carbon black, and PVDF are added to NMP at a mass ratio of 97.5:1:1.5, and stirred to prepare a slurry. Then, the slurry is applied to the current collector by extrusion coating, dried, and cold pressed to obtain a positive electrode sheet.

[0123] The preparation method of the positive electrode plate in Comparative Example 2 is different from that in Example 1 only in that: a first coating slurry is prepared: LiNiCoMnO2 material, conductive carbon black, and PVDF are added with NMP in a mass ratio of 97.5:1:1.5, and the mixture is stirred to form a slurry.

[0124] The only difference between Comparative Example 3 and Example 1 is that the first coating slurry and the first coating slurry are mixed in a mass ratio of 1:1, the obtained mixed slurry is coated on the current collector, dried, and cold pressed to obtain a positive electrode sheet, wherein the thickness of the positive electrode active material layer formed by the mixed slurry is 160 μm.

[0125] The only difference between Comparative Example 4 and Example 1 is that PVDF is used to replace PEO.

[0126]

Negative electrode sheet preparation

[0127] The negative electrode active material graphite, the conductive agent acetylene black, the binder styrene butadiene rubber, and the thickener sodium carboxymethyl cellulose are mixed in a weight ratio of graphite: acetylene black: styrene butadiene rubber: sodium carboxymethyl cellulose = 95:2:2:1, and an appropriate amount of deionized water is added and stirred to form a uniform negative electrode slurry; after coating the slurry on the negative electrode current collector copper foil, it is dried and cold pressed to obtain a negative electrode sheet.

[0128]

Electrolyte preparation

[0129] The electrolyte was prepared according to the following method: in an argon atmosphere glove box (H2O<0.1ppm, O2<0.1ppm), the organic solvents ethylene carbonate (EC) / ethyl methyl carbonate (EMC) were evenly mixed in a volume ratio of 3 / 7, 1 mol / L LiPF6 lithium salt was added and dispersed evenly, and then 2% fluoroethylene carbonate was dissolved in the above organic solvent and stirred evenly to obtain an electrolyte.

[0130]

Battery preparation

[0131] The positive electrode sheet, the separator, and the negative electrode sheet are stacked in order, so that the separator is placed between the positive and negative electrode sheets to play an isolating role, and then they are wound to obtain a bare battery cell; the bare battery cell is placed in an outer packaging foil, and the prepared electrolyte is injected into the dried battery, and then the battery is obtained after vacuum packaging, standing, forming, shaping and other processes.

[0132]

Resistance test of positive electrode

[0133] The cold pressed positive electrode is cut into 1540.25mm by a cutting machine. 2 Then put the small disc into the diaphragm resistance tester to test the diaphragm resistance, test 10ea and take the average value.

[0134]

Battery 25 / 45℃ cycle performance test

[0135] At 25 / 45°C, the batteries prepared in the examples and comparative examples are charged to 4.35V at a constant current of 1C, further charged to a current of 0.05C at a constant voltage of 4.35V, and then discharged to 2V at a constant current of 1C. This is a charge and discharge cycle process, and the discharge capacity this time is the initial capacity C1. Repeat the above steps for the same battery, and record the discharge capacity Cn of the battery after the nth cycle at the same time, and detect the discharge capacity of the 200th cycle. The battery capacity retention rate after each cycle is Pn = Cn / C1*100%. After 200 cycles, record C200 and calculate P200 = C200 / C1*100%.

[0136] The test results of various embodiments and comparative examples are shown in Table 2.

[0137] Table 1 Differentiating parameters between the embodiments and the comparative examples

[0138]

[0139]

[0140] Table 2 Test results of embodiments and comparative examples

[0141]

[0142] It can be seen from Table 1 and Table 2 that the positive electrode plate provided in the present application can effectively improve the capacity retention rate of the battery after cycling while reducing the DC internal resistance of the battery.

[0143] According to Example 1, Comparative Example 1 and Comparative Example 2, it can be seen that since Comparative Example 1 and Comparative Example 2 do not contain additives, no matter LiNiCoMnO2 and LiFePO4 are directly mixed or layered, there are problems such as large DC internal resistance of the battery and low capacity retention rate of the battery after cycling.

[0144] According to Example 1 and Comparative Example 3, it can be seen that although Comparative Example 3 contains additives, since LiNiCoMnO2 and LiFePO4 are directly mixed in Comparative Example 3, the DC internal resistance of the battery is large and the capacity retention rate of the battery after cycling is low. In Example 1, due to the layered setting, it can effectively reduce the DC internal resistance of the battery and improve the capacity retention rate of the battery after cycling.

[0145] According to Example 1 and Comparative Example 4, although PVDF is used in Comparative Example 4 to replace PEO in Example 1, its DC internal resistance is large and the capacity retention rate of the battery after cycling is low. This is because the crystallinity of PVDF and its liquid absorption and swelling rate in the electrolyte at 20-30°C do not meet the requirements of the flexible polymer matrix of this application.

[0146] According to Examples 1-10, no matter the additive is a separate flexible polymer matrix or a solid electrolyte, it can reduce the DC internal resistance and improve the capacity retention rate of the battery after cycling. When the addition amount is 0.1%, the optimization effect is limited due to the small amount of addition. The mass percentage of the additive in the second positive electrode active material layer is 0.5%-23%, which has a lower DC internal resistance and a better capacity retention rate. When the mass percentage of the additive in the second positive electrode active material layer is 3%-23%, the DC internal resistance and capacity retention rate can be further optimized.

[0147] According to Example 1 and Example 11, the relative positions of the first positive electrode active material layer and the second positive electrode active material layer affect the DC internal resistance and the capacity retention rate, wherein the arrangement of the first positive electrode active material layer between the second positive electrode active material layer and the current collector is conducive to further reducing the DC internal resistance and improving the capacity retention rate.

[0148] According to Example 1 and Examples 12-14, the mass ratio of the flexible polymer matrix and the electrolyte salt in the solid electrolyte will also affect the DC internal resistance and the capacity retention rate. When the mass ratio of the flexible polymer matrix and the electrolyte salt is (2:95)-(40:60), both a lower DC internal resistance and a higher capacity retention rate are achieved. When the mass ratio of the flexible polymer matrix and the electrolyte salt is (10:90)-(40:60), the DC internal resistance and the capacity retention rate can be further optimized.

[0149] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them; although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents; 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 present application, and they should all be included in the scope of the claims and specification of the present application. In particular, as long as there is no structural conflict, the various technical features mentioned in the various embodiments can be combined in any way. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions that fall within the scope of the claims.

Claims

1. A positive electrode sheet, characterized in that: The invention comprises a current collector, and a first positive electrode active material layer and a second positive electrode active material layer stacked on the current collector; The first positive electrode active material layer includes an olivine structure phosphate material, the second positive electrode active material layer includes a layered transition metal oxide and an additive, the additive includes a flexible polymer matrix, the crystallinity of the flexible polymer matrix is ​​10%-60%, and the liquid absorption swelling rate of the flexible polymer matrix in the electrolyte at 20-30°C is 50%-500%.

2. The positive electrode sheet according to claim 1, characterized in that: The olivine structure phosphate material includes Li a Fe b M 1-b P 1-m O 4-n , wherein M includes at least one of other metal elements except Fe, wherein 0<a≤1.1, 0≤b≤1, 0≤m≤0.1, 0≤n≤0.1; Optionally, M includes at least one of Mn, Al, Cu, Mg, Zn, Ni, Ti, V, Zr, Co, Ga, Sn, Sb, Nb and Ge; Optionally, the olivine structure phosphate material includes at least one of lithium iron phosphate and lithium manganese iron phosphate.

3. The positive electrode sheet according to claim 1, characterized in that: The layered transition metal oxides include LiCoO2, LiMnO2, LiNiO2, Li a Ni x Co y M1 1-x-y O 2+d , z Li2MnO3 (1-z) At least one of LiM2O2, wherein M1 includes at least one of Mn, Zr, Al, B, Ta, Mo, W, Nb, Sb, and La, and M2 includes at least one of Co, Ni, and Mn, 0.5≤x≤1.0, 0≤y<0.5, x+y<1, 0.2≤a<1.2, -0.02≤d<0.02, and 0<z<1; Optionally, the layered transition metal oxide includes at least one of lithium cobalt oxide, lithium nickel oxide, lithium-rich material, nickel-cobalt-manganese ternary material and manganese-cobalt-aluminum ternary material.

4. The positive electrode sheet according to any one of claims 1 to 3, characterized in that: The amount of the olivine structure phosphate material added to the first positive electrode active material layer is 90%-99%; and / or the amount of the layered transition metal oxide added to the second positive electrode active material layer is 90%-99%.

5. The positive electrode sheet according to any one of claims 1 to 4, characterized in that: The mass percentage of the additive in the second positive electrode active material layer is 0.5%-23%, and can be 3%-23%.

6. The positive electrode sheet according to any one of claims 1 to 5, characterized in that: The additive is a solid electrolyte, and the solid electrolyte includes the flexible polymer matrix and an electrolyte salt; Optionally, the electrolyte salt is an alkali metal salt, optionally a lithium salt or a sodium salt.

7. The positive electrode sheet according to claim 6, characterized in that: In the solid electrolyte, the mass ratio of the flexible polymer matrix to the electrolyte salt is (2:95)-(40:60), and can be optionally (10:90)-(40:60).

8. The positive electrode sheet according to any one of claims 1 to 5, characterized in that: The additive is a flexible polymer matrix.

9. The positive electrode sheet according to any one of claims 1 to 8, characterized in that: The flexible polymer matrix includes one or more of polyethylene oxide, polyethylene glycol, polyvinyl pyrrolidone, polymethyl methacrylate, polyvinylidene fluoride, polyvinyl alcohol, polyacrylonitrile, polyvinyl chloride, polyacrylamide, polytrimethylene carbonate, perfluoropolyether, and poly(vinylidene fluoride-co-hexafluoropropylene) copolymer; Optionally, the flexible polymer matrix includes one or more of polyethylene oxide, polyethylene glycol, perfluoropolyether, and poly(vinylidene fluoride-co-hexafluoropropylene) copolymer.

10. The positive electrode sheet according to any one of claims 1 to 5, characterized in that: The first positive electrode active material layer is located between the second positive electrode active material layer and the current collector.

11. A battery, characterized in that: include: An electrolyte and a positive electrode sheet as described in any one of claims 1 to 9.

12. An electrical device, characterized in that: The electrical device comprises the battery as claimed in claim 11, wherein the battery is used to provide electrical energy.

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