Positive electrode composite materials, positive electrode sheets, electrode assemblies, battery cells, batteries and electrical equipment

Abstract

The present application discloses a positive electrode composite material, a positive electrode sheet, an electrode assembly, a battery cell, a battery and an electrical device. The positive electrode composite material includes a positive electrode active material and a hydrophobic agent. The molecular formula of the hydrophobic agent is R-X, wherein the R group is a hydrocarbon group that does not contain halogen and has a carbon number of ≥3 in the carbon chain, and the X group is used to form a covalent bond and / or a hydrogen bond with the positive electrode active material. Among them, the hydrophobic agent can effectively reduce the adsorption of moisture in the environment by the positive electrode active material, thereby effectively reducing the water content in the positive electrode sheet, and can effectively improve the phenomenon that the residual moisture in the positive electrode sheet reacts with the electrolyte to destroy the SEI film, thereby effectively improving the coulombic efficiency and cycle performance of the battery.

Description

Technical Field

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

[0002] With the rapid growth of portable electronic devices and electric vehicles, the demand for power batteries is also growing. Among them, the electrochemical performance of batteries is also attracting more and more attention.

[0003] At present, the SEI film of power batteries is easily damaged, which makes the coulombic efficiency and cycle performance of the battery deteriorate. Summary of the invention

[0004] In view of the above problems, the present application provides a positive electrode composite material, a positive electrode sheet, an electrode assembly, a battery cell, a battery and an electrical device, which can improve the coulombic efficiency and cycle performance of the battery.

[0005] The embodiment of the present application is implemented as follows:

[0006] In a first aspect, an embodiment of the present application provides a positive electrode composite material, comprising a positive electrode active substance and a hydrophobic agent, wherein the molecular formula of the hydrophobic agent is RX, wherein the R group is a halogen-free hydrocarbon group with a carbon number of ≥3 in the carbon chain, and the X group is used to form a covalent bond and / or a hydrogen bond with the positive electrode active substance.

[0007] In the technical scheme of the embodiment of the present application, the R group is a hydrocarbon group that does not contain halogen and has ≥3 carbon atoms in the carbon chain, has hydrophobicity, and avoids the introduction of halogen to react with the residual moisture in the positive electrode sheet to produce an acid that destroys the SEI film. The X group is used to form a bond with the positive active material, which can improve the dispersibility and stability of the hydrophobic agent in the positive electrode slurry and the positive electrode sheet. The X group plays an anchoring role, so that the hydrophobic agent can be connected to the positive active material, and the hydrophobic agent can form a coating layer on the surface of the positive active material to coat and protect the hydrophobic agent. The hydrophobic group can effectively play a hydrophobic role on the surface of the positive active material. Therefore, in the present application, the hydrophobic agent can effectively reduce the adsorption of moisture in the environment by the positive active material, thereby effectively reducing the water content in the positive electrode sheet, and can effectively improve the phenomenon that the residual moisture in the positive electrode sheet reacts with the electrolyte to destroy the SEI film, thereby effectively improving the coulomb efficiency and cycle performance of the battery.

[0008] In some embodiments, the covalent bond includes one or more of a carbon-nitrogen double bond, a carbon-nitrogen single bond, a carbon-sulfur double bond, and a carbon-sulfur single bond. In this embodiment, the carbon-nitrogen double bond, the carbon-nitrogen single bond, the carbon-sulfur double bond, and the carbon-sulfur single bond are all conveniently formed by attacking the carbon-oxygen double bond on the surface of the positive electrode active material, so that the preparation process of the positive electrode plate is simple; it can effectively improve the dispersibility and stability of the hydrophobic agent in the positive electrode slurry and the positive electrode plate, and is conducive to the hydrophobic agent effectively connecting and coating the surface of the positive electrode active material, thereby improving the coulombic efficiency and cycle performance of the battery.

[0009] In some embodiments, the X group contains one or more of a primary amino group, a sulfonic acid group, and a mercapto group. In this embodiment, the primary amino group can effectively attack the carbon-oxygen double bond on the surface of the positive electrode active material to form a carbon-nitrogen double bond, the mercapto group can effectively attack the carbon-oxygen double bond on the surface of the positive electrode active material to form a carbon-sulfur single bond, and the sulfonic acid group can effectively form a hydrogen bond with the hydroxyl group on the surface of the positive electrode active material, thereby facilitating the improvement of the coulombic efficiency and cycle performance of the battery monomer.

[0010] In some embodiments, the R group is an alkyl group containing a C3-C20 carbon chain. In this embodiment, the R group has a specific carbon chain length and unsaturation, so that the R group has suitable hydrophobicity and stability, and thus the hydrophobic agent can effectively play a hydrophobic role, which is beneficial to improve the coulombic efficiency and cycle performance of the battery monomer.

[0011] In some embodiments, the R group is an alkyl group containing a C10-C20 carbon chain. In this embodiment, the R group has a certain carbon chain length, so that the R group has good hydrophobicity, and thus the hydrophobic agent can play a good hydrophobic role, which is conducive to better improving the coulombic efficiency and cycle performance of the battery monomer.

[0012] In some embodiments, the carbon chain of the R group is connected to a specified substituent, and the specified substituent includes an alkyl group and / or a phenyl group. In this embodiment, the R group is connected to a specified substituent with hydrophobicity, which can improve the overall hydrophobicity of the R group, so that the hydrophobic agent can play a better hydrophobic role, thereby helping to better improve the coulombic efficiency and cycle performance of the battery monomer.

[0013] In some embodiments, the hydrophobic agent includes one or more of dodecyl primary amine, octadecyl mercaptan, dodecyl sulfonic acid, 1,3-dimethylbutylamine, tert-amylamine, decyl primary amine, tetradecyl primary amine, octadecyl primary amine, butanethiol, pentanethiol, octanethiol, decanethiol, dodecanethiol, tetradecanethiol, 1-eicosanethiol, butylsulfonic acid, octanesulfonic acid, tetradecylsulfonic acid, octadecylsulfonic acid, 3-methyl-2-butene-1-thiol and 3-butynamine. In this embodiment, a specific type of hydrophobic agent is selected, and the hydrophobic agent has good dispersibility and stability in the positive electrode slurry and the positive electrode sheet, and the hydrophobic agent is effectively connected and coated on the surface of the positive electrode active material, and the hydrophobic agent can play a good hydrophobic role, so it is beneficial to improve the coulomb efficiency and cycle performance of the battery monomer.

[0014] In some embodiments, the mass ratio of the positive electrode active material and the hydrophobic agent is 1: 0.0001 to 0.05. In this embodiment, the mass ratio of the positive electrode active material and the hydrophobic agent meets a certain lower limit requirement, avoiding too low a dosage of the hydrophobic agent, so that the hydrophobic agent can better reduce the water content in the positive electrode plate; the mass ratio of the positive electrode active material and the hydrophobic agent meets a certain upper limit requirement, avoiding too high a dosage of the hydrophobic agent, because after further increasing the dosage of the hydrophobic agent, the effect of reducing the water content in the positive electrode plate is less improved, but the coating layer formed by the hydrophobic agent on the surface of the positive electrode active material layer will be too thick, which will increase the internal resistance of the positive electrode plate and cause the kinetics of the battery cell to deteriorate, which will affect the cycle performance and the energy density.

[0015] In some embodiments, the mass ratio of the positive electrode active material to the hydrophobic agent is 1: 0.0001 to 0.005. In this embodiment, the mass ratio of the positive electrode active material to the hydrophobic agent meets certain standards, which can better take into account the effect of the hydrophobic agent on reducing the water content in the positive electrode sheet and the electrochemical performance of the battery cell.

[0016] In some embodiments, the mass ratio of the positive electrode active material to the hydrophobic agent is 1: 0.005 to 0.05. In this embodiment, the mass ratio of the positive electrode active material to the hydrophobic agent meets certain standards and can better reduce the water content in the positive electrode sheet.

[0017] In some embodiments, the positive electrode active material includes one or more of lithium iron phosphate, lithium nickel oxide, lithium cobalt oxide, lithium manganese oxide and ternary lithium.

[0018] In a second aspect, an embodiment of the present application provides a positive electrode plate, including a positive electrode current collector, and a positive electrode active material layer disposed on the surface of the positive electrode current collector, the positive electrode active material layer includes the positive electrode composite material as described in the above embodiment, and the X group and the positive electrode active material form a covalent bond and / or a hydrogen bond.

[0019] In a third aspect, an embodiment of the present application provides an electrode assembly, comprising a positive electrode plate as described in the above embodiment.

[0020] In a fourth aspect, an embodiment of the present application provides a battery cell, comprising an electrode assembly as described in the above embodiment.

[0021] In a fifth aspect, an embodiment of the present application provides a battery, comprising a battery cell as described in the above embodiment.

[0022] In a sixth aspect, an embodiment of the present application provides an electrical device, comprising a battery cell as in the above embodiment or a battery as in the above embodiment.

[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] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

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

[0026] Figure 2 An exploded view of a battery provided for some embodiments of the present application;

[0027] Figure 3 An exploded view of a battery cell provided for some embodiments of the present application;

[0028] Figure 4 A schematic diagram of the structure of an electrode assembly provided in some embodiments of the present application;

[0029] Figure 5 A schematic diagram of the structure of a first positive electrode sheet provided in some embodiments of the present application;

[0030] Figure 6 A schematic structural diagram of the second positive electrode plate provided in some embodiments of the present application.

[0031] icon:

[0032] 1000-Vehicles;

[0033] 100-battery; 200-controller; 300-motor;

[0034] 10-box; 11-first part; 12-second part; 13-accommodating space;

[0035] 20-battery cell; 21-housing; 22-electrode assembly; 23-electrode terminal; 24-pressure relief structure;

[0036] 211-housing; 212-cover; 213-sealed space;

[0037] 221-positive electrode plate; 222-negative electrode plate; 223-separating film;

[0038] 2211 - positive electrode current collector; 2212 - positive electrode active material layer. DETAILED DESCRIPTION

[0039] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme in the embodiments of the present application will be described clearly and completely below. If the specific conditions are not specified in the embodiments, they are carried out according to the conventional conditions or the conditions recommended by the manufacturer. If the manufacturer is not specified for the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0040] 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.

[0041] 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.

[0042] In the description of the embodiments of the present application, technical terms such as "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.

[0043] In the description of the embodiments of the present application, the orientations or positional relationships indicated by the technical terms "inside" and "outside" are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the embodiments of the present application and simplifying the description, rather than indicating or implying that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the embodiments of the present application.

[0044] In the description of the embodiments of the present application, the technical term "and / or", such as "Feature 1 and / or Feature 2", refers to three situations: it can be "Feature 1" alone, "Feature 2" alone, or "Feature 1" plus "Feature 2".

[0045] In the description of the embodiments of the present application, unless otherwise specified, the meaning of “multiple” in “one or more” is two or more than two.

[0046] 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 one; it can be directly connected or indirectly connected through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in the embodiments of the present application can be understood according to specific circumstances.

[0047] 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.

[0048] In the embodiments of the present application, the same reference numerals represent the same components, and for the sake of brevity, detailed descriptions of the same components are omitted in different embodiments. It should be understood that the heights, lengths, widths, and other dimensions of the various components in the embodiments of the present application shown in the drawings, as well as the overall heights, lengths, widths, and other dimensions of the integrated device are only exemplary descriptions and should not constitute any limitation to the present application.

[0049] At present, the water content in the environment must be strictly controlled during the production of power batteries. Taking lithium-ion batteries as an example, for the positive electrode active material, especially the nano-sized lithium iron phosphate particles, its particles are small and easily absorb water, and it is difficult to remove them by baking. The residual water in the positive electrode will react with the LiPF6 in the electrolyte to generate HF, thereby causing the SEI film to be damaged, and ultimately making the lithium-ion battery coulombic efficiency and cycle performance worse.

[0050] In order to improve the above problems, in some technical solutions, a high-pressure heating box, a vacuum dehydration box and a cooling box are interconnected to form a tunnel structure, and a concentration difference static box containing a desiccant is set behind the cooling box, and the water content of the positive electrode plate is further reduced by using the concentration difference dehydration method between the boxes. In some technical solutions, the positive electrode plate is first baked at normal pressure and high temperature, then baked at vacuum and high temperature, and then dry gas is injected to break the vacuum, and finally the dry gas is extracted, so as to achieve the effect of effective water removal in a short time. However, in the above technical solutions, the means to improve the baking effect of the positive electrode plate are mainly concentrated on increasing production steps, improving process conditions and improving equipment capacity. Such complex production steps and processes reduce production efficiency on the one hand, and on the other hand, they also lead to increased production costs, which is not conducive to large-scale promotion.

[0051] Based on the above considerations, some technical solutions propose to add a dehydrating agent to the electrolyte, and use the reaction between the dehydrating agent and water to reduce the water content in the battery. However, the addition of the dehydrating agent will increase the viscosity of the electrolyte, causing the battery dynamics to deteriorate, and may deteriorate the rate performance of the battery.

[0052] The applicant noted that, in some cases, by adding a hydrophobic component to the positive electrode plate, the adsorption of environmental moisture on the surface of the positive electrode material during battery preparation can be reduced, which can also reduce the water content in the positive electrode plate and avoid the problem of adding a dehydrating agent to the electrolyte.

[0053] However, the applicant has found that when a hydrophobic component is added to the positive electrode sheet, the water content in the positive electrode sheet is usually reduced to a lesser extent. In some technical solutions, it is considered that a halogen group is added to the hydrophobic component to improve the hydrophobicity of the hydrophobic component. However, the introduced halogens such as fluorine will also react with the residual water in the positive electrode sheet to produce acid that destroys the SEI film. Therefore, it is actually unable to better improve the phenomenon of SEI film destruction, and cannot effectively improve the coulombic efficiency and cycle performance of the battery.

[0054] Further research found that the above situation occurred because the hydrophobic component has poor dispersibility and stability in the positive electrode slurry, which makes it unable to effectively coat the positive electrode active material. Therefore, it is difficult to effectively reduce the adsorption of moisture in the environment by the positive electrode active material, which limits the effect of reducing the water content in the positive electrode sheet.

[0055] On this basis, the applicant discovered through in-depth research that when adding a hydrophobic component to the positive electrode plate, by adding a hydrophobic agent with a specific hydrophobic group and a specified functional group, the specified functional group is used to form a bond with the positive electrode active material, so that the hydrophobic component is connected to the positive electrode active material and effectively coats the positive electrode active material, which can improve the dispersibility and stability of the hydrophobic component in the positive electrode slurry and the positive electrode plate and improve the protective effect of the hydrophobic component on the positive electrode active material. The hydrophobic group can effectively play a hydrophobic role on the surface of the positive electrode active material, thereby effectively reducing the adsorption of moisture in the environment by the positive electrode active material.

[0056] Based on this, the embodiment of the present application provides a positive electrode composite material and a positive electrode plate, the positive electrode composite material includes a positive electrode active material and a hydrophobic agent, the hydrophobic agent has a hydrophobic group and a specified functional group, and the specified functional group is used to form a bond with the positive electrode active material. The positive electrode plate includes the positive electrode composite material, and the hydrophobic agent can effectively reduce the adsorption of moisture in the environment by the positive electrode active material, thereby effectively reducing the water content in the positive electrode plate, and effectively improving the phenomenon that the residual moisture in the positive electrode plate reacts with the electrolyte to destroy the SEI film, thereby effectively improving the coulombic efficiency and cycle performance of the battery.

[0057] From the perspective of market development, the application of power batteries is becoming more and more extensive. Power 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 the application field of power batteries, the market demand is also constantly expanding.

[0058] For the convenience of explanation, the following embodiments are described by taking a vehicle as an example of an electrical device in an embodiment of the present application.

[0059] See also 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.

[0060] 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.

[0061] In the present application, the battery 100 refers to a single physical module including multiple battery cells 20 to provide higher voltage and capacity, which can be in the form of a battery pack, a battery module, etc. The battery 100 may include a box 10 for encapsulating multiple 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.

[0062] See also Figure 2 , Figure 2 An exploded view of a battery 100 provided for some embodiments of the present application. The battery 100 includes a box 10 and a plurality of battery cells 20, and the plurality of battery cells 20 are accommodated in the box 10. Among them, the box 10 is used to accommodate the battery cells 20, and the box 10 can be a variety of structures. In some embodiments, the box 10 can include a first part 11 and a second part 12, 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 receiving space 13 for accommodating the battery cells 20. The second part 12 can be a hollow structure with one end open, the first part 11 is a plate-like structure, and the first part 11 covers the open side of the second part 12 to form a box 10 with a receiving space 13; 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 to form a box 10 with a receiving space 13. Of course, the first part 11 and the second part 12 can be a variety of shapes, such as a cylinder, a cuboid, etc.

[0063] In the battery 100, multiple battery cells 20 can be connected in series, in parallel, or in a hybrid connection. A hybrid connection means that multiple battery cells 20 are both connected in series and in parallel. Multiple battery cells 20 can be directly connected in series, in parallel, or in a hybrid connection, and then the whole formed by multiple battery cells 20 is accommodated in the box 10. Alternatively, multiple battery cells 20 can be connected in series, in parallel, or in a hybrid connection to form a module, and multiple modules can be connected in series, in parallel, or in a hybrid connection to form a whole, and then accommodated in the box 10. The battery 100 can also include other structures. For example, multiple battery cells 20 can be electrically connected through a busbar component to achieve parallel, series, or hybrid connection of multiple battery cells 20.

[0064] The battery cell 20 refers to the smallest unit constituting the battery pack. The battery cell 20 may be a secondary battery 100 or a primary battery 100; it may also be a lithium-sulfur battery 100, a sodium-ion battery 100 or a magnesium-ion battery 100, but is not limited thereto.

[0065] See also Figure 3 The battery cell 20 may include a housing 21 , an electrode assembly 22 and an electrolyte, and both the electrode assembly 22 and the electrolyte are contained in the housing 21 .

[0066] The housing 21 may include a shell 211 and a cover 212. The shell 211 is a component used to cooperate with the cover 212 to form an internal sealed space 213 of the battery cell 20, wherein the formed sealed space 213 can be used to accommodate the electrode assembly 22, electrolyte and other components. The cover 212 refers to a component that covers the opening of the shell 211 to isolate the internal environment of the battery cell 20 from the external environment. The shape of the cover 212 can be adapted to the shape of the shell 211 to cooperate with the shell 211, and the cover 212 may also be provided with functional components such as electrode terminals 23 and pressure relief structures 24. A sealing ring may be configured between the opening of the shell 211 and the cover 212 to achieve sealing between the shell 211 and the cover 212.

[0067] The shell 211 and the cover 212 can be of various shapes and sizes, such as a rectangular parallelepiped, a cylindrical shape, a hexagonal prism, etc. Specifically, the shapes of the shell 211 and the cover 212 can be determined according to the specific shape and size of the electrode assembly 22. The shell 211 and the cover 212 can be made of various materials, such as but not limited to metals such as copper, iron, aluminum, stainless steel, and aluminum alloy. The sealing ring can be made of various materials, such as but not limited to PP (polypropylene), PC (polycarbonate), PET (polyethylene terephthalate) and other materials that are resistant to electrolyte corrosion, high toughness and fatigue resistance. A coating can be formed on the outer surface of the shell 211, and the material of the coating can be various, such as but not limited to corrosion-resistant materials such as Ni and Cr.

[0068] See also Figure 4 , the electrode assembly 22 may be composed of a positive electrode sheet 221, a negative electrode sheet 222 and a separator 223. The battery cell 20 mainly relies on the movement of metal ions between the positive electrode sheet 221 and the negative electrode sheet 222 to work. The positive electrode sheet 221 includes a positive current collector 2211 and a positive active material layer 2212 disposed on the surface of the positive current collector 2211. The material of the positive current collector 2211 may be aluminum, and the positive active material in the positive active material layer 2212 may be lithium cobalt oxide, lithium iron phosphate, ternary lithium, lithium manganate, lithium-rich manganese-based materials, lithium sulfur and other materials. The negative electrode sheet 222 includes a negative current collector and a negative active material layer disposed on the surface of the negative current collector. The material of the negative current collector may be copper, and the negative active material material in the negative active material layer may be carbon, silicon and the like. In addition, the electrode assembly 22 may be a winding structure or a laminated structure, and the embodiments of the present application are not limited thereto.

[0069] In the embodiment of the present application, the positive electrode active material layer 2212 includes a positive electrode composite material. The positive electrode composite material includes not only a positive electrode active material but also a specified hydrophobic agent.

[0070] Next, the positive electrode composite material proposed in the examples of the present application is described in detail.

[0071] In a first aspect, an embodiment of the present application provides a positive electrode composite material, comprising a positive electrode active substance and a hydrophobic agent, wherein the molecular formula of the hydrophobic agent is RX, wherein the R group is a halogen-free hydrocarbon group with a carbon number of ≥3 in the carbon chain, and the X group is used to form a covalent bond and / or a hydrogen bond with the positive electrode active substance.

[0072] The positive electrode active material may be an active material containing lithium, an active material containing sodium, or an active material containing both lithium and sodium.

[0073] Halogen refers to the halogen family elements, including fluorine, chlorine, bromine and other elements.

[0074] In the R group, the carbon chain has, for example, 3 to 50 carbon atoms, or 3 to 40 carbon atoms, or 3 to 30 carbon atoms, or 3 to 20 carbon atoms. In addition, the carbon chain may or may not be connected to a side chain, a heteroatom, or the like.

[0075] The type of hydrocarbon group is not limited, and it may be an alkyl group, an alkenyl group, an alkynyl group, or the like.

[0076] The X group is used to form a covalent bond and / or a hydrogen bond with the positive electrode active material, which means that the X group has a functional group that forms a covalent bond and / or a hydrogen bond with the positive electrode active material, and it may contain only a functional group that forms a covalent bond with the positive electrode active material, or it may contain only a functional group that forms a hydrogen bond with the positive electrode active material, or it may contain both a functional group that forms a covalent bond with the positive electrode active material and a functional group that forms a hydrogen bond with the positive electrode active material.

[0077] In the present application, the X group and the positive electrode active material can be bonded in a conventional process for forming the positive electrode plate 221, and the process for forming the positive electrode plate 221 includes the steps of mixing to form a positive electrode slurry, coating the positive electrode slurry, drying, supercooling pressing and slitting, that is, no additional heating or other operations are required to allow the X group to react with the positive electrode active material in advance.

[0078] A covalent bond is a chemical bond formed by two or more atoms using their outer electrons together, including carbon-nitrogen double bond, carbon-nitrogen single bond, carbon-phosphorus double bond, carbon-phosphorus single bond, carbon-sulfur double bond, carbon-sulfur single bond, etc.

[0079] Hydrogen bond refers to a special intermolecular or intramolecular interaction force generated between atoms with high electronegativity using hydrogen as the medium.

[0080] In the technical solution of the embodiment of the present application, the R group is a hydrocarbon group that does not contain halogen and has ≥3 carbon atoms in the carbon chain, has hydrophobicity, and avoids the introduction of halogen to react with the residual moisture in the positive electrode plate 221 to produce an acid that destroys the SEI film. The X group is used to form a bond with the positive active material, which can improve the dispersibility and stability of the hydrophobic agent in the positive electrode slurry and the positive electrode plate 221. The X group plays an anchoring role, so that the hydrophobic agent can be connected to the positive active material, and the hydrophobic agent can form a coating layer on the surface of the positive active material to coat and protect the hydrophobic agent. The hydrophobic group can effectively play a hydrophobic role on the surface of the positive active material. Therefore, in the present application, the hydrophobic agent can effectively reduce the adsorption of moisture in the environment by the positive active material, thereby effectively reducing the water content in the positive electrode plate 221, and can effectively improve the phenomenon that the residual moisture in the positive electrode plate 221 reacts with the electrolyte to destroy the SEI film, thereby effectively improving the coulomb efficiency and cycle performance of the battery 100.

[0081] In some embodiments, the covalent bond includes one or more of a carbon-nitrogen double bond, a carbon-nitrogen single bond, a carbon-sulfur double bond, and a carbon-sulfur single bond.

[0082] The chemical formula of carbon-nitrogen double bond is C=N, the chemical formula of carbon-nitrogen double bond is CN, the chemical formula of carbon-sulfur double bond is C=S, and the chemical formula of carbon-sulfur single bond is CS.

[0083] In this embodiment, both the carbon-nitrogen double bond and the carbon-sulfur single bond are easily formed by attacking the carbon-oxygen double bond on the surface of the positive electrode active material, so that the preparation process of the positive electrode plate 221 is simple; it can effectively improve the dispersibility and stability of the hydrophobic agent in the positive electrode slurry and the positive electrode plate 221, and is beneficial for the hydrophobic agent to effectively connect and coat the surface of the positive electrode active material, thereby helping to improve the coulombic efficiency and cycle performance of the battery 100.

[0084] In some embodiments, the X group contains one or more of a primary amino group, a sulfonic acid group, and a thiol group.

[0085] The chemical formula of primary amino group is -NH2, the chemical formula of sulfonic acid group is -SO3H, and the chemical formula of thiol group is -SH.

[0086] In this embodiment, the primary amino group can effectively attack the carbon-oxygen double bonds on the surface of the positive electrode active material to form carbon-nitrogen double bonds, the thiol group can effectively attack the carbon-oxygen double bonds on the surface of the positive electrode active material to form carbon-sulfur single bonds, and the sulfonic acid group can effectively form hydrogen bonds with the hydroxyl group on the surface of the positive electrode active material, thereby facilitating the improvement of the coulombic efficiency and cycle performance of the battery cell 20.

[0087] In some embodiments, the R group is an alkyl group containing a C3-C20 carbon chain.

[0088] C3-C20 means that the number of carbon atoms in the carbon chain is 3-20. As an example, the number of carbon atoms in the carbon chain is, but not limited to, any one of 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19 and 20, or a range between any two of them.

[0089] In this embodiment, the R group has a specific carbon chain length and unsaturation, so that the R group has suitable hydrophobicity and stability, thereby enabling the hydrophobic agent to effectively play a hydrophobic role, thereby facilitating improving the coulombic efficiency and cycle performance of the battery cell 20 .

[0090] In some embodiments, the R group is an alkyl group containing a C10-C20 carbon chain.

[0091] In this embodiment, the R group has a certain carbon chain length, so that the R group has good hydrophobicity, and thus the hydrophobic agent can play a good hydrophobic role, which is beneficial to better improve the coulombic efficiency and cycle performance of the battery cell 20.

[0092] In some embodiments, the carbon chain of the R group is linked to the specified substituents, which include alkyl and / or phenyl groups.

[0093] Regarding the designated substituents, the types of alkyl groups are, for example but not limited to, methyl, ethyl, etc., and the molecular formula of phenyl is -C6H5.

[0094] In this embodiment, the R group is connected with a designated substituent having hydrophobicity, which can improve the overall hydrophobicity of the R group, so that the hydrophobic agent can play a better hydrophobic role, thereby helping to better improve the coulombic efficiency and cycle performance of the battery cell 20.

[0095] In some embodiments, the hydrophobic agent includes one or more of dodecyl primary amine, octadecyl mercaptan, dodecyl sulfonic acid, 1,3-dimethylbutylamine, tert-amylamine, decyl primary amine, tetradecyl primary amine, octadecyl primary amine, butyl mercaptan, pentyl mercaptan, octadecyl mercaptan, decyl mercaptan, dodecanethiol, tetradecanethiol, 1-eicosanethiol, butyl sulfonic acid, octyl sulfonic acid, tetradecyl sulfonic acid, octadecyl sulfonic acid, 3-methyl-2-butene-1-thiol and 3-butynamine.

[0096] In this embodiment, a specific type of hydrophobic agent is selected, which has good dispersibility and stability in the positive electrode slurry and the positive electrode plate 221. The hydrophobic agent is effectively connected and coated on the surface of the positive electrode active material, and the hydrophobic agent can play a good hydrophobic role, so it is beneficial to improve the coulombic efficiency and cycle performance of the battery cell 20.

[0097] In some embodiments, the mass ratio of the positive electrode active material to the hydrophobic agent is 1:0.0001-0.05.

[0098] As an example, the mass ratio of the positive electrode active material to the hydrophobic agent is, for example but not limited to, any one of 1:0.0001, 1:0.0005, 1:0.001, 1:0.005, 1:0.01 and 1:0.05 or a range between any two thereof.

[0099] In this embodiment, the mass ratio of the positive electrode active material and the hydrophobic agent meets a certain lower limit requirement, avoiding too low an amount of the hydrophobic agent, so that the hydrophobic agent can better reduce the water content in the positive electrode plate 221; the mass ratio of the positive electrode active material and the hydrophobic agent meets a certain upper limit requirement, avoiding too high an amount of the hydrophobic agent, because after further increasing the amount of the hydrophobic agent, the effect of reducing the water content in the positive electrode plate 221 is slightly improved, but the coating layer formed by the hydrophobic agent on the surface of the positive electrode active material layer 2212 will be too thick, which will increase the internal resistance of the positive electrode plate 221 and cause the dynamics of the battery cell 20 to deteriorate, which will affect the cycle performance and energy density.

[0100] In some embodiments, the mass ratio of the positive electrode active material to the hydrophobic agent is 1:0.0001-0.005.

[0101] Optionally, the mass ratio of the positive electrode active material to the hydrophobic agent is 0.0005-0.005, or 0.001-0.005. As an example, the mass ratio of the positive electrode active material to the hydrophobic agent is, for example but not limited to, any one of 1:0.001, 1:0.002, 1:0.003, 1:0.004 and 1:0.005 or a range between any two of them.

[0102] In this embodiment, the mass ratio of the positive electrode active material and the hydrophobic agent meets certain standards, which can better take into account the effect of the hydrophobic agent in reducing the water content in the positive electrode plate 221 and the electrochemical performance of the battery cell 20.

[0103] In some embodiments, the mass ratio of the positive electrode active material to the hydrophobic agent is 1:0.005-0.05.

[0104] As an example, the mass ratio of the positive electrode active material to the hydrophobic agent is, for example but not limited to, any one of 1:0.005, 1:0.01, 1:0.015, 1:0.02, 1:0.025, 1:0.03, 1:0.035, 1:0.04, 1:0.045 and 1:0.05, or a range between any two thereof.

[0105] In some embodiments, the positive electrode active material includes one or more of lithium iron phosphate, lithium nickel oxide, lithium cobalt oxide, lithium manganese oxide and ternary lithium.

[0106] See also Figure 5 and Figure 6In a second aspect, an embodiment of the present application provides a positive electrode plate 221, comprising a positive electrode collector 2211, and a positive electrode active material layer 2212 disposed on the surface of the positive electrode collector 2211, wherein the positive electrode active material layer 2212 comprises the positive electrode composite material as described in the above embodiment, and the X group and the positive electrode active material form a covalent bond and / or a hydrogen bond.

[0107] In the positive electrode sheet 221, a positive electrode active material layer 2212 may be provided on one side surface of the positive electrode current collector 2211, such as Figure 5 As shown; the positive electrode active material layer 2212 may also be provided on both sides of the positive electrode current collector 2211, such as Figure 6 shown.

[0108] In the positive electrode active material layer 2212, the X group and the positive electrode active material form a covalent bond and / or a hydrogen bond, so that the hydrophobic agent forms a coating layer on the surface of the positive electrode active material. Among them, the X group of the whole hydrophobic agent or a part of the hydrophobic agent and the positive electrode active material form a covalent bond and / or a hydrogen bond, that is, in the positive electrode active material layer 2212, there may be some free X groups that are not connected to the positive electrode active material.

[0109] In a third aspect, an embodiment of the present application provides an electrode assembly 22, comprising a positive electrode plate 221 as described in the above embodiment.

[0110] In a fourth aspect, an embodiment of the present application provides a battery cell 20, comprising an electrode assembly 22 as described in the above embodiment.

[0111] In a fifth aspect, an embodiment of the present application provides a battery 100, comprising a battery cell 20 as described in the above embodiment.

[0112] In a sixth aspect, an embodiment of the present application provides an electrical device, including a battery cell 20 as in the above embodiment or a battery 100 as in the above embodiment.

[0113] According to some embodiments of the present application, the positive electrode composite material includes lithium iron phosphate and a hydrophobic agent, the hydrophobic agent is one of dodecyl primary amine, octadecyl mercaptan, dodecyl sulfonic acid and 1,3-dimethylbutylamine, and the mass ratio of lithium iron phosphate to the hydrophobic agent is 1:0.0001~0.005.

[0114] Based on the positive electrode plate 221 provided in the embodiment of the present application, the functional group and material structure can be confirmed by infrared analysis (refer to GB / T6040-2002 "General Rules for Infrared Spectroscopic Analysis Methods") and mass spectrometry analysis (refer to GB / T 6041-2020 "General Rules for Mass Spectrometric Analysis Methods"), and the content of the hydrophobic agent and its mass ratio to the positive electrode active substance can be reversely calculated.

[0115] Some specific embodiments are listed below to better illustrate the present application.

[0116] 1. Preparation of battery cells

[0117]

Preparation of positive electrode

[0118] Lithium iron phosphate, conductive carbon, polyvinylidene fluoride (PVDF) and hydrophobic agent (in some comparative examples, no hydrophobic agent is added if there is no hydrophobic agent) are prepared in a certain mass ratio, dissolved in N-methylpyrrolidone (NMP), stirred for 4 hours, and the viscosity is adjusted to 10000mPa·s with NMP. The slurry is stirred evenly, coated on aluminum foil and dried at 90°C, and then cold pressed and cut to obtain a positive electrode sheet.

[0119]

Preparation of negative electrode sheet

[0120] Active material artificial graphite, conductive agent carbon black, binder styrene-butadiene rubber (SBR), thickener sodium hydroxymethyl cellulose (CMC) are dissolved in solvent deionized water at a weight ratio of 96.2:0.8:0.8:1.2, mixed evenly and prepared into negative electrode slurry; the negative electrode slurry is evenly coated on copper foil once or multiple times and dried at 90°C, and negative electrode sheets are obtained through cold pressing and slitting.

[0121]

Preparation of electrolyte

[0122] In an argon atmosphere glove box (H2O<0.1ppm, O2<0.1ppm), the organic solvents ethylene carbonate (EC) / ethyl methyl carbonate (EMC) were mixed in a volume ratio of 3 / 7, 12.5% ​​LiPF6 lithium salt was added and dissolved in the organic solvent, and stirred evenly to obtain the electrolyte of Example 1.

[0123]

Preparation of isolation film

[0124] A polyethylene film is used as the isolation film.

[0125]

Preparation of lithium-ion batteries

[0126] The positive electrode sheet, separator, and negative electrode sheet are stacked in order, so that the separator is between the positive electrode sheet and the negative electrode sheet to play an isolating role, and then they are wound, the tabs are welded, and they are placed in an aluminum shell, and baked at 105°C to remove water, and then the electrolyte is injected and sealed to obtain an uncharged battery cell. The uncharged battery cell is then subjected to the processes of static, hot and cold pressing, formation, shaping, and capacity testing to obtain a lithium-ion battery cell.

[0127] 2. Test Method

[0128]

Anti-gel time test

[0129] Take 200mL of positive electrode slurry and store it in an environment with a humidity of 30% to 50%. Test the viscosity after standing for different time periods. When the viscosity is >9000mPa·s, it is judged as gel, and the corresponding standing time is the anti-gel time. The viscosity test refers to GB / T 10247-2008 "Standard for Viscosity Measurement Method", and a DV-II+ BROOKFIELD viscometer is used to test the viscosity of the middle part of the positive electrode slurry.

[0130] In the present application, the anti-gel time of the positive electrode slurry is used to judge the dispersibility and stability of the positive electrode slurry. The longer the anti-gel time is, the better the dispersibility and stability of the positive electrode slurry is.

[0131] [Positive electrode water absorption performance test]

[0132] Take 1g of the positive electrode sheet before injection, cut the positive electrode sheet into 2cm*5cm strips with scissors, refer to the standard GB / T29249-2012, use a Karl Fischer titrator to test the water content of the positive electrode sheet, the test temperature is 170℃, measure three sets of parallel samples for each positive electrode sheet, record the three sets of parallel test results and calculate the average result.

[0133] [First round of efficiency test and capacity retention test of battery cells]

[0134] At 25°C, the lithium-ion battery is charged to 3.65V at a constant current of 1 / 3C, then charged to a current of 0.05C at a constant voltage of 3.65V, left for 5 minutes, and then discharged to 2.5V at a rate of 1 / 3C. This is a charge-discharge cycle process, and the discharge capacity this time is the discharge capacity of the first cycle. Repeat the above steps for the lithium-ion battery to perform a charge-discharge cycle test, and take the discharge capacity of the 2000th cycle.

[0135] The first-round efficiency of a lithium-ion battery = (first discharge capacity) / (first charge capacity) × 100%.

[0136] The capacity retention rate of the lithium ion battery after 2000 cycles = (discharge capacity at the 2000th cycle / discharge capacity at the first cycle) × 100%.

[0137] 3. Experimental conditions and test results

[0138] The types of additives used in each experimental group and the mass ratios of each material in the positive electrode slurry are shown in Table 1, Table 2 is the anti-gel time test results of the positive electrode slurry, Table 3 is the water absorption performance test results of the positive electrode sheet, and Table 4 is the electrochemical performance test results of the battery cell.

[0139] Table 1

[0140]

[0141]

[0142] The material mass ratio in the positive electrode slurry refers to the mass ratio of the positive electrode active material, the conductive carbon, the binder PVDF and the hydrophobic agent in order.

[0143] Table 2

[0144]

[0145] According to Table 1 and Table 2, we can know that:

[0146] In Examples 1 to 18, a hydrophobic agent containing both R and X groups was added. Compared with Comparative Example 1 in which no hydrophobic agent was added, the anti-gel time was significantly increased, indicating that the positive electrode slurries of Examples 1 to 18 had better dispersibility and stability. In Comparative Example 2, a hydrophobic agent was added in the same amount as in Example 3, but the hydrophobic agent contained only R groups but no X groups. However, even compared with Comparative Example 1 in which no hydrophobic agent was added, the anti-gel time did not increase but was slightly shortened. The improvement in surface dispersibility and stability mainly came from the X group. Adding the R group alone may even have a certain adverse effect on the dispersibility and stability of the positive electrode slurry.

[0147] In Examples 1 to 15, when the mass ratio of the positive electrode active material to the hydrophobic agent is within a certain range, the anti-gel time gradually increases with the gradual increase in the amount of the hydrophobic agent used; among them, when the mass ratio of the hydrophobic agent to the positive electrode active material is not more than 0.005:1, the anti-gel time increases at a faster rate with the increase in the amount of the hydrophobic agent used.

[0148] Table 3

[0149]

[0150]

[0151] According to Table 1 and Table 3, we can know that:

[0152] In Examples 1 to 18, a hydrophobic agent containing both R groups and X groups was added, and the water content of the positive electrode plate was significantly reduced compared with that in Comparative Example 1 in which no hydrophobic agent was added. In Comparative Example 2, a hydrophobic agent was added in the same amount as in Example 3, but the hydrophobic agent contained only R groups but no X groups, and the water content of the positive electrode plate was not significantly reduced compared with Comparative Example 1, and the water content of the positive electrode plate was significantly higher than that in Example 3.

[0153] In Examples 1 to 15, when the mass ratio of the positive electrode active material to the hydrophobic agent is within a certain range, as the amount of the hydrophobic agent gradually increases, the water content of the positive electrode plate gradually decreases; among them, when the mass ratio of the hydrophobic agent to the positive electrode active material is not more than 0.005:1, the water content of the positive electrode plate decreases faster with the increase in the amount of the hydrophobic agent; when the mass ratio of the hydrophobic agent to the positive electrode active material is 0.005:1 and above, the water content of the positive electrode plate is lower.

[0154] Table 4

[0155]

[0156]

[0157] According to Table 1 and Table 4, we can know that:

[0158] In Examples 1 to 18, a hydrophobic agent containing both R groups and X groups was added, and the first-round efficiency and capacity retention rate of the battery monomer were significantly improved compared with the comparative example 1 in which no hydrophobic agent was added. In comparative example 2, the same amount of hydrophobic agent as in Example 3 was added, but the hydrophobic agent contained only R groups but no X groups, and the first-round efficiency and capacity retention rate of the battery monomer were not significantly improved compared with comparative example 1, and the first-round efficiency and capacity retention rate of the battery monomer were significantly lower than those in Example 3.

[0159] In Examples 1 to 15, when the mass ratio of the hydrophobic agent to the positive electrode active material is not more than 0.005:1, as the amount of the hydrophobic agent is gradually increased, the first-round efficiency and capacity retention rate of the battery monomer are gradually improved; when the mass ratio of the hydrophobic agent to the positive electrode active material is more than 0.005:1, as the amount of the hydrophobic agent is gradually increased, the first-round efficiency and capacity retention rate of the battery monomer begin to decline to a certain extent.

Claims

1. A positive electrode composite material, characterized in that: It comprises a positive electrode active material and a hydrophobic agent, wherein the molecular formula of the hydrophobic agent is RX, wherein the R group is a hydrocarbon group containing no halogen and having a carbon number of ≥3 in the carbon chain, and the X group is used to form a covalent bond and / or a hydrogen bond with the positive electrode active material; The X group contains one or more of a primary amino group, a sulfonic acid group and a mercapto group.

2. The positive electrode composite material according to claim 1, characterized in that: The covalent bond includes one or more of a carbon-nitrogen double bond, a carbon-nitrogen single bond, a carbon-sulfur double bond and a carbon-sulfur single bond.

3. The positive electrode composite material according to claim 1, characterized in that: The R group is an alkyl group containing a C3 to C20 carbon chain.

4. The positive electrode composite material according to claim 3, characterized in that: The R group is an alkyl group containing a C10-C20 carbon chain.

5. The positive electrode composite material according to claim 1, characterized in that: The carbon chain of the R group is connected to the specified substituents, which include alkyl and / or phenyl groups.

6. The positive electrode composite material according to claim 1, characterized in that: The hydrophobic agent includes one or more of dodecyl primary amine, octadecyl mercaptan, dodecyl sulfonic acid, 1,3-dimethylbutylamine, tert-amylamine, decyl primary amine, tetradecyl primary amine, octadecyl primary amine, butyl mercaptan, pentyl mercaptan, octadecyl mercaptan, decyl mercaptan, dodecanethiol, tetradecanethiol, 1-eicosanethiol, butyl sulfonic acid, octyl sulfonic acid, tetradecyl sulfonic acid, octadecyl sulfonic acid, 3-methyl-2-butene-1-thiol and 3-butynamine.

7. The cathode composite material according to any one of claims 1 to 6, characterized in that The mass ratio of the positive electrode active material to the hydrophobic agent is 1:0.0001-0.

05.

8. The positive electrode composite material according to claim 7, characterized in that: The mass ratio of the positive electrode active material to the hydrophobic agent is 1:0.0001-0.

005.

9. The positive electrode composite material according to claim 7, characterized in that: The mass ratio of the positive electrode active material to the hydrophobic agent is 1:0.005-0.

05.

10. The positive electrode composite material according to claim 1, characterized in that: The positive electrode active material includes one or more of lithium iron phosphate, lithium nickel oxide, lithium cobalt oxide, lithium manganese oxide and ternary lithium.

11. A positive electrode sheet, comprising a positive electrode current collector and a positive electrode active material layer disposed on the surface of the positive electrode current collector, characterized in that: The positive electrode active material layer comprises the positive electrode composite material according to any one of claims 1 to 10, and the X group and the positive electrode active material form a covalent bond and / or a hydrogen bond.

12. An electrode assembly, characterized in that: Comprising the positive electrode sheet as claimed in claim 11.

13. A battery cell, characterized in that: Comprising the electrode assembly as claimed in claim 12.

14. A battery, characterized in that: Comprising the battery cell as claimed in claim 13.

15. An electrical equipment, characterized in that: Comprising the battery cell as claimed in claim 13 or the battery as claimed in claim 14.

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