Composite positive electrode material and preparation method thereof, positive electrode sheet containing same, battery and electric device

Abstract

The present application provides a composite positive electrode material, a preparation method thereof, a positive electrode sheet, a battery, and an electrical device containing the same. The composite positive electrode material comprises a positive electrode active material and a coating layer, wherein the coating layer coats at least a portion of the surface of the positive electrode active material, and the coating layer comprises a composite material, wherein the composite material comprises particles containing a single substance M and a lithium ion conductor material attached to the surface of the particles containing the single substance M, wherein M comprises at least one of S, Se, and Te.

Description

Technical Field

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

[0002] Secondary batteries rely on the reciprocating intercalation and deintercalation of active ions between the positive and negative electrodes to charge and discharge. Lithium-ion batteries, for example, offer outstanding characteristics such as high energy density, long cycle life, zero pollution, and no memory effect. Therefore, as a clean energy source, secondary batteries have gradually spread from electronic products to large-scale devices such as electric vehicles, adapting to the sustainable development strategy of the environment and energy.

[0003] Among them, energy density is considered to be the biggest bottleneck restricting the development of current secondary batteries. Breakthroughs and innovations in materials are of great significance to achieving the technical goal of high energy density. Nickel-rich ternary cathode materials (such as LiNi m Co n M 1-m-n O2, m ≥ 0.6, M is Mn or Al) has become a research hotspot in recent years due to its high reversible capacity and low cost. However, the cycling and storage performance of batteries based on nickel-rich ternary cathode materials are poor, which limits their application. Summary of the Invention

[0004] In order to achieve the above-mentioned objectives, the present application provides a composite positive electrode material, which can improve the cycle performance, storage performance and rate performance of the battery containing the composite positive electrode material; the present application also provides a method for preparing the composite positive electrode material, a positive electrode sheet containing the composite positive electrode material, a battery and an electrical device.

[0005] An embodiment of the first aspect of the present application provides a composite positive electrode material, which includes a positive electrode active material and a coating layer, which is coated on at least a portion of the surface of the positive electrode active material. The coating layer contains a composite material, and the composite material includes particles containing an M element and a lithium ion conductor material attached to the surface of the particles containing the M element, where M includes at least one of S, Se, and Te.

[0006] Without intending to be bound by any theory or explanation, the composite positive electrode material of the embodiment of the present application includes a positive electrode active material and a coating layer, and the coating layer contains a composite material, which can effectively improve the cycle performance, storage performance and rate performance of the battery. Specifically, the coating layer of the composite positive electrode material includes the above-mentioned particles containing M element. During the processing or storage process of the battery, the coating layer can inhibit the contact between the positive electrode active material and the air, thereby inhibiting the generation of residual lithium compounds (RLCs) on the surface; the coating layer of the composite material also includes a lithium ion conductor material attached to the surface of the particles. The lithium ion conductor material can construct a good ion conductive network at the material level, thereby improving the ion transmission rate of the composite positive electrode material. Compared with the technical solution of directly coating the sulfide element on the surface of the positive electrode active material in the related art, the composite positive electrode material of the embodiment of the present application has the advantage of higher ion conductivity.

[0007] In addition, when the positive electrode active material is a ternary positive electrode material, during the battery formation process, the M element can also react with the positive electrode active material, replacing some of the oxygen atoms on the surface of the positive electrode active material, thereby doping into the positive electrode active material. Compared with oxygen atoms, M atoms have stronger electronegativity and larger atomic radius. Doping into the positive electrode active material can not only enhance the ionic conductivity of the positive electrode active material, but also widen the interlayer spacing of the positive electrode active material, inhibiting the migration of lithium ions and transition metal layers. As a result, the cycle stability of the positive electrode active material can also be improved, delaying the voltage drop and capacity decay of the battery.

[0008] Therefore, the composite positive electrode material of the embodiment of the present application is applied to a secondary battery, which can effectively improve the cycle performance, storage performance and rate performance of the battery.

[0009] In any embodiment of the present application, the lithium ion conductor material includes an ion conductivity of 1×10 -5 S / cm or above, optionally 0.001S / cm-1S / cm lithium ion conductor material.

[0010] When the ionic conductivity of the lithium ion conductor material falls within the given range, it not only helps improve the ion transport rate of the composite cathode material, but also facilitates the reaction of the M element with the cations on the surface of the cathode active material, allowing it to be doped into the cathode active material and thus improve the cycling stability of the cathode active material. Therefore, the composite cathode material of the embodiments of the present application can be used in secondary batteries to further improve the battery's rate performance and cycling performance.

[0011] In any embodiment of the present application, the lithium ion conductor material includes at least one of lithium zinc germanium oxide, lithium aluminum titanium phosphate, lithium aluminum germanium phosphate, lithium lanthanum titanate, glassy lithium conductive electrolyte powder, and garnet structure lithium conductive electrolyte powder.

[0012] Optionally, the lithium ion conductor material includes at least one of lithium aluminum titanium phosphate and lithium aluminum germanium phosphate.

[0013] The lithium ion conductor material selected from the above types has suitable ionic conductivity, which can make the coating layer have higher ionic conductivity and make the M element have higher kinetic reaction rate.

[0014] In any embodiment of the present application, the volume distribution particle size Dv50 of the particles containing the element M is ≤ 2 μm, and can be selected from 0.3 μm to 1 μm. This facilitates a tighter coating of the coating layer on the surface of the positive electrode active material, inhibiting side reactions between the positive electrode active material and air, thereby suppressing the generation of RLCs.

[0015] Optionally, the volume distribution particle size Dv50 of the lithium ion conductor material is ≤ 100 nm, and can be selected to be 20 nm to 50 nm. This can increase the contact area between the lithium ion conductor material, the M element, and the positive electrode active material, which is beneficial for further improving the ion transmission rate of the composite positive electrode material and the kinetic reaction rate of the M element, thereby improving the rate performance and cycle performance of the battery.

[0016] Optionally, the volume distribution particle size Dv50 of the positive electrode active material is 5 μm-15 μm. As a result, the composite positive electrode material can have a higher theoretical gram capacity and a suitable ion transport path, which is conducive to improving the capacity of the composite positive electrode material, thereby improving the energy density of the battery.

[0017] Optionally, the volume distribution particle size Dv50 of the composite cathode material is 8 μm-20 μm. Thus, the composite cathode material can have a suitable ion transport path, which is conducive to improving the ion transport rate of the composite cathode material, thereby improving the rate performance of the battery.

[0018] In any embodiment of the present application, based on the total mass of the composite positive electrode material, the mass percentage of the positive electrode active material is 80%-98%, and can be optionally 90%-95%.

[0019] In any embodiment of the present application, based on the total mass of the composite positive electrode material, the mass percentage of the particles containing the M element is 0.02%-5%, and can be optionally 0.05%-2%.

[0020] In any embodiment of the present application, based on the total mass of the composite positive electrode material, the mass percentage of the lithium ion conductor material is 0.01%-1%, and can be optionally 0.05%-1%.

[0021] When the content of each component in the composite cathode material meets the given range, the composite cathode material can achieve both a high theoretical specific capacity and a high ionic conductivity, while also reducing the risk of RLCs forming on the surface of the cathode active material. Furthermore, when the content of the lithium ion conductor material meets the given range, the risk of gelation in the cathode slurry can be reduced, thereby improving the processability of the composite cathode material and, in turn, increasing battery production capacity.

[0022] In any embodiment of the present application, the composite material is attached to the surface of the positive electrode active material via a binder to form a coating layer.

[0023] Optionally, the lithium ion conductor material is attached to the surface of the particles containing M element via a binder.

[0024] The composite material is attached to the surface of the positive electrode active material through the binder, so that the composite material can be firmly anchored on the surface of the positive electrode active material, thereby improving the interface stability between the coating layer and the positive electrode active material.

[0025] In any embodiment of the present application, the adhesive includes a castor oil-based UV oligomer adhesive.

[0026] Optionally, the castor oil-based UV oligomer adhesive includes a castor oil-based UV oligomer having a molecular weight of 200 Da to 800 Da.

[0027] Castor oil-based UV oligomer binders not only possess excellent bonding properties but also, after UV curing, form a tight cross-linked network, thereby enhancing the cohesion of the cathode film. This improves the structural stability of both the composite cathode material and the cathode electrode sheet, thereby enhancing the battery's cycling performance and extending its cycle life. Furthermore, castor oil-based UV oligomer binders possess excellent electrical conductivity, which increases the electron transfer rate of the composite cathode material, thereby reducing the bulk impedance of the composite cathode material and, in turn, improving the battery's cycling, storage, and rate capabilities.

[0028] In any embodiment of the present application, the positive electrode active material includes a nickel-cobalt-manganese ternary material and / or a nickel-cobalt-aluminum ternary material.

[0029] Optionally, in the nickel-cobalt-manganese ternary material, the molar content of Ni element in the transition metal elements is greater than or equal to 0.6.

[0030] Optionally, in the nickel-cobalt-aluminum ternary material, the molar content of Ni element in the transition metal elements is greater than or equal to 0.6.

[0031] The composite cathode material of the present invention has a specific coating layer, which can inhibit the formation of RLCs on the surface of the cathode active material and improve the ionic conductivity of the composite cathode material. This is conducive to the application of high-nickel-content ternary cathode active materials in secondary batteries, allowing the secondary batteries to have high energy density, good cycle performance, storage performance, and rate performance.

[0032] An embodiment of the second aspect of the present application provides a method for preparing a composite positive electrode material, including: preparing a composite material, including mixing particles containing a single substance M with a lithium ion conductor material, allowing the lithium ion conductor material to adhere to the surface of the particles containing the single substance M to obtain a composite material, where M includes at least one of S, Se, and Te; preparing a composite positive electrode material, including uniformly mixing the composite material with a positive electrode active material, allowing the composite material to coat at least a portion of the surface of the positive electrode active material to obtain a composite positive electrode material.

[0033] According to the method of the embodiment of the present application, a composite positive electrode material is prepared, including a positive electrode active material and a coating layer, and the coating layer contains a composite material, which can effectively improve the cycle performance, storage performance and rate performance of the battery. Specifically, the coating layer of the composite positive electrode material includes the above-mentioned particles containing M element. During the processing or storage process of the battery, the coating layer can inhibit the contact between the positive electrode active material and the air, thereby inhibiting the generation of RLCs; the coating layer of the composite material also includes a lithium ion conductor material attached to the surface of the particles. The lithium ion conductor material can construct a good ion conductive network at the material level, thereby improving the ion transmission rate of the composite positive electrode material. Compared with the technical solution of directly coating the surface of the positive electrode active material with a sulfide element in the related art, the composite positive electrode material prepared according to the method of the embodiment of the present application has the advantage of higher ion conductivity.

[0034] In addition, when the positive electrode active material is a ternary positive electrode material, during the battery formation process, the M element can also react with the positive electrode active material, replacing some of the oxygen atoms on the surface of the positive electrode active material, thereby doping into the positive electrode active material. Compared with oxygen atoms, M atoms have stronger electronegativity and larger atomic radius. Doping into the positive electrode active material can not only enhance the ionic conductivity of the positive electrode active material, but also widen the interlayer spacing of the positive electrode active material, inhibiting the migration of lithium ions and transition metal layers. As a result, the cycle stability of the positive electrode active material can also be improved, delaying the voltage drop and capacity decay of the battery.

[0035] Therefore, the composite positive electrode material prepared according to the method of the embodiment of the present application is applied to a secondary battery, which can effectively improve the cycle performance, storage performance and rate performance of the battery.

[0036] In any embodiment of the present application, preparing the composite material includes: mixing particles containing M element, a lithium ion conductor material, and a castor oil-based UV oligomer binder and ball milling the mixture to obtain a slurry containing the composite material.

[0037] The preparation of the composite positive electrode material includes: uniformly mixing the slurry and the positive electrode active material, and then curing the castor oil-based UV oligomer binder to coat at least a portion of the surface of the positive electrode active material with the composite material to obtain the composite positive electrode material.

[0038] Castor oil-based UV oligomer binders not only possess excellent bonding properties but also, after UV curing, form a tight cross-linked network, thereby enhancing the cohesion of the cathode film. This improves the structural stability of both the composite cathode material and the cathode electrode sheet, thereby enhancing the battery's cycling performance and extending its cycle life. Furthermore, castor oil-based UV oligomer binders possess excellent electrical conductivity, which increases the electron transfer rate of the composite cathode material, thereby reducing the bulk impedance of the composite cathode material and, in turn, improving the battery's cycling, storage, and rate capabilities.

[0039] In any embodiment of the present application, the mass ratio of the particles containing M element to the lithium ion conductor material is 1:0.3-1:0.6.

[0040] Optionally, the mass ratio of the particles containing M element to the castor oil-based UV oligomer binder is 1:0.1-1:0.3.

[0041] When the mass ratio of the particles containing the M element to the lithium ion conductor material falls within the specified range, an appropriate amount of the lithium ion conductor material can be attached to the particle surface, thereby improving the ionic conductivity of the composite cathode material and reducing the risk of RLCs forming on the surface of the cathode active material. Furthermore, when the mass ratio of the particles to the lithium ion conductor material falls within the specified range, the risk of gelation in the cathode slurry can be reduced, thereby improving the processability of the composite cathode material.

[0042] An embodiment of the third aspect of the present application provides a positive electrode plate, comprising a positive electrode current collector and a positive electrode film layer located on at least one side of the positive electrode current collector, the positive electrode film layer comprising the composite positive electrode material of the first aspect, or the composite positive electrode material prepared according to the method of the second aspect.

[0043] The positive electrode plate of the embodiment of the present application includes the composite positive electrode material of the first aspect, or the composite positive electrode material prepared according to the method of the second aspect, and is applied to a secondary battery, which can enable the secondary battery to have good cycle performance, storage performance and rate performance.

[0044] A fourth aspect of an embodiment of the present application provides a battery, comprising the positive electrode plate of the third aspect.

[0045] The battery of the embodiment of the present application includes the positive electrode plate of the third aspect, which can have good cycle performance, storage performance and rate performance.

[0046] A fifth aspect of an embodiment of the present application provides an electrical device, comprising the battery of the fourth aspect.

[0047] The electric device according to the embodiment of the present application includes the battery according to the fourth aspect, and thus has at least the same advantages as the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 It is a schematic structural diagram of a composite positive electrode material in one embodiment of the present application.

[0049] Figure 2 It is a schematic structural diagram of a composite positive electrode material in another embodiment of the present application.

[0050] Figure 3 It is a schematic diagram of an embodiment of a battery cell of the present application.

[0051] Figure 4 yes Figure 3 An exploded view of an embodiment of a battery cell of the present application is shown.

[0052] Figure 5 It is a schematic diagram of an embodiment of a battery module of the present application.

[0053] Figure 6 It is a schematic diagram of an embodiment of the battery pack of the present application.

[0054] Figure 7 yes Figure 6 An exploded view of an embodiment of the battery pack of the present application is shown.

[0055] Figure 8 It is a schematic diagram of an embodiment of an electric device of the present application, which may include a battery pack or a battery module according to an embodiment of the present application as a power source.

[0056] 100 composite positive electrode material; 110 positive electrode active material; 120 coating layer; 121 composite material; 121a particles containing M element; 121b lithium ion conductor material; 121c castor oil-based UV oligomer binder; 1 battery pack; 2 upper case; 3 lower case; 4 battery module; 5 battery cell; 51 casing; 52 electrode assembly; 53 cover plate. DETAILED DESCRIPTION

[0057] Below, with appropriate reference to the accompanying drawings, the embodiments of the composite positive electrode material and its preparation method, the positive electrode sheet, the battery and the electrical device containing the same are specifically disclosed. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structure are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0058] " range " disclosed in the present application is limited in the form of lower limit and upper limit, and given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of special range. The scope limited in this way can be to include end value or not include end value, and can be arbitrarily combined, that is, any lower limit can form a range with any upper limit combination. For example, if the scope of 60-120 and 80-110 is listed for specific parameters, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range value 1 and 2 are listed, and if the maximum range value 3,4 and 5 are listed, then the following range can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In this application, unless otherwise specified, the numerical range " ab " represents the abbreviation of any real number combination between a and b, wherein a and b are all real numbers. For example, a numerical range of "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is simply an abbreviation for these numerical combinations. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0059] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0060] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0061] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), indicating that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0062] Unless otherwise specified, the terms "include" and "comprising" used in this application may be open-ended or closed-ended. For example, "include" and "comprising" may mean that other components not listed may also be included or that only the listed components are included.

[0063] Unless otherwise specified, the term "or" is used in this application to be inclusive. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, the condition "A or B" is satisfied if any of the following conditions are met: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0064] Unless otherwise stated, the numerical values ​​of the various parameters mentioned in this application can be measured using various test methods commonly used in the art, for example, they can be measured according to the test methods given in the examples of this application. Unless otherwise stated, the test temperature of each parameter is 25°C.

[0065] Unless otherwise specified, all ratio parameters involved in this application are compared in the same unit. For example, the thickness ratio of A to B is 1.2:1, and the thickness units of A and B are the same.

[0066] With the application and promotion of secondary batteries in various electronic products and new energy vehicles and other industries, higher requirements are placed on the energy density of secondary batteries.

[0067] Nickel-rich ternary cathode materials (such as LiNi m Co n M 1-m-n O2, m≥0.6, M is Mn or Al) has become a research hotspot in recent years due to its advantages such as high reversible capacity and low cost. Related technologies have involved nickel-rich ternary positive electrode materials with a nickel content of more than 90%, such as LiNi 0.9 Mn 0.1 O2 and LiNi 0.95 Co 0.025 Mn 0.025O2, and obtained a very impressive initial discharge specific capacity.

[0068] However, nickel-rich ternary cathode materials are prone to produce surface residual lithium compounds (RLCs), which not only have no electrochemical activity but also hinder the Li + As well as the diffusion of electrons, this limits the capacity of the nickel-rich ternary positive electrode material, aggravates the growth of the internal resistance of the battery, and deteriorates the cycle performance and storage performance of the battery.

[0069] Related technologies involve modifying nickel-rich ternary cathode materials to remove RLCs from their surfaces and inhibit their subsequent formation. Surface coating is a commonly used modification strategy. Surface coating forms a coating layer on the surface of the nickel-rich ternary cathode material, inhibiting its contact with air and thus suppressing the formation of RLCs.

[0070] However, the coating layer involved in the related art has low ionic conductivity, which leads to a decrease in the rate performance of the battery.

[0071] In view of this, an embodiment of the present application provides a composite positive electrode material, which can improve the cycle performance, storage performance and rate performance of the battery containing the composite positive electrode material; the present application also provides a method for preparing the composite positive electrode material, a positive electrode sheet containing the composite positive electrode material, a battery and an electrical device.

[0072] Composite cathode materials

[0073] Embodiments of the first aspect of the present application provide a composite positive electrode material, comprising a positive electrode active material and a coating layer, the coating layer coating at least a portion of the surface of the positive electrode active material. The coating layer comprises a composite material, the composite material comprising particles containing a single element M and a lithium ion conductor material attached to the surface of the particles containing the single element M, wherein M comprises at least one of S, Se, and Te.

[0074] Studies have shown that sulfur elements, such as S, Se, and Te, have strong reducing properties. The transition metals in nickel-rich ternary cathode materials exist in the form of cations. 3+ 、Ni 2+ 、Co 3+ 、Mn 4+ When cations such as Li2SO3 and Li2SO4 come into contact with sulfide elements, the sulfide elements can react with these cations to form electrochemically stable compounds (such as Li2SO3, Li2SO4, etc.), thereby forming a coating layer. +It can be used to compensate for the loss of active lithium ions caused by the formation of the SEI film during the first cycle of charge and discharge. On the other hand, the generated electrochemically stable compounds can play a similar role as the CEI film, improving the stability of the positive electrode environment. However, these electrochemically stable compounds, such as Li2SO3 and Li2SO4, still have the disadvantage of low ionic conductivity, which makes it difficult to improve the battery's rate performance.

[0075] Without intending to be limited by any theory or explanation, the composite positive electrode material of the embodiment of the present application includes a positive electrode active material and a coating layer, and the coating layer contains a composite material, which can effectively improve the cycle performance, storage performance and rate performance of the battery. Specifically, the coating layer of the composite positive electrode material includes the above-mentioned particles containing the M element. During the processing or storage process of the battery, the coating layer can inhibit the contact between the positive electrode active material and the air, thereby inhibiting the generation of RLCs; the coating layer of the composite material also includes a lithium ion conductor material attached to the surface of the particles containing the M element. The lithium ion conductor material can construct a good ion conductive network at the material level, thereby improving the ion transmission rate of the composite positive electrode material. Compared with the technical solution of directly coating the sulfide element on the surface of the positive electrode active material in the related art, the composite positive electrode material of the embodiment of the present application has the advantage of higher ion conductivity.

[0076] In addition, when the positive electrode active material is a ternary positive electrode material, during the battery formation process, the M element can also react with the positive electrode active material, replacing some of the oxygen atoms on the surface of the positive electrode active material, thereby doping into the positive electrode active material. Compared with oxygen atoms, M atoms have stronger electronegativity and larger atomic radius. Doping into the positive electrode active material can not only enhance the ionic conductivity of the positive electrode active material, but also widen the interlayer spacing of the positive electrode active material, inhibiting the migration of lithium ions and transition metal layers. As a result, the cycle stability of the positive electrode active material can also be improved, delaying the voltage drop and capacity decay of the battery.

[0077] Therefore, the composite positive electrode material of the embodiment of the present application is applied to a secondary battery, which can effectively improve the cycle performance, storage performance and rate performance of the battery.

[0078] In an embodiment of the present application, the positive electrode active material may adopt one or more of the nickel-containing lithium transition metal oxides and modified compounds thereof for secondary batteries that are well known in the art. Examples of nickel-containing lithium transition metal oxides may include, but are not limited to, one or more of lithium nickel oxide, lithium nickel cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and modified compounds thereof, having a nickel content of more than 0.6. The above-mentioned "nickel content of more than 0.6" may mean that the molar content of the Ni element is greater than or equal to 0.6 based on the total molar amount of the transition metal elements in the nickel-containing lithium transition metal oxide. For example, for lithium nickel cobalt manganese oxide, "nickel content of more than 0.6" may mean that the molar amount of the Ni element / (molar amount of the Ni element + molar amount of the Co element + molar amount of the Mn element) ≥ 0.6.

[0079] In the embodiments of the present application, the lithium ion conductor material may refer to a substance having ionic conductivity, and specifically may include a fast ion conductor material whose conductive ion is lithium. Examples of the lithium ion conductor material may include one or more lithium ion conductor materials known in the art, and are not limited here.

[0080] In the embodiments of the present application, the lithium ion conductor material is attached to the surface of the particle containing the M element, which may mean that the lithium ion conductor material is anchored to the particle surface through interaction with the particle surface containing the M element, or is anchored to the particle surface containing the M element through the action of a binder. For example, the lithium ion conductor material may be attached to the surface of the particle containing the M element through chemical bonding or hydrogen bonding, or the lithium ion conductor material may be attached to the surface of the particle containing the M element through a binder.

[0081] Figure 1 FIG. 1 shows a schematic structural diagram of a composite positive electrode material according to an embodiment of the present application. Figure 1 As shown, the composite positive electrode material 100 may include a positive electrode active material 110 and a coating layer 120, wherein the coating layer 120 coats at least a portion of the surface of the positive electrode active material 110. The coating layer 120 may include a composite material 121, and the composite material 121 may include particles 121a containing an M element and a lithium ion conductor material 121b. The lithium ion conductor material 121b may be attached to the surface of the particles 121a containing an M element. In some embodiments, the lithium ion conductor material 121b may be attached to the surface of the particles 121a containing an M element, forming a coating layer that coats at least a portion of the surface of the particles 121a containing an M element.

[0082] The structure of the composite cathode material provided in the embodiments of the present application can be characterized using equipment and methods known in the art. For example, the composite cathode material can be subjected to argon ion cross-section polishing, and an EDS elemental distribution profile of the cross-section of the composite cathode material can be measured using an EDS spectrometer. The structure of the composite cathode material can be determined based on the elemental distribution in the EDS elemental distribution profile.

[0083] In some embodiments, the lithium ion conductor material may include an ionic conductivity of 1×10 -5 S / cm or more. For example, the lithium ion conductor material may include an ion conductivity of 1×10 -5 S / cm or more, 1×10 -4 S / cm or more, 0.001 S / cm or more, 0.1 S / cm or more, or 1 S / cm or more lithium ion conductor material.

[0084] Alternatively, in some embodiments, the lithium ion conductor material may include a lithium ion conductor material having an ionic conductivity of 0.001 S / cm to 1 S / cm. For example, the lithium ion conductor material may include a lithium ion conductor material having an ionic conductivity of 0.001 S / cm, 0.005 S / cm, 0.01 S / cm, 0.15 S / cm, 0.2 S / cm, 0.5 S / cm, 0.8 S / cm, 1 S / cm, or a range between any two of the foregoing values.

[0085] Without intending to be bound by any theory or explanation, when the ionic conductivity of the lithium ion conductor material satisfies the given range, the ionic conductivity of the coating layer and the kinetic reaction rate of the M element can be improved. This not only helps to improve the ion transport rate of the composite positive electrode material, but also facilitates the reaction of the M element with the cations on the surface of the positive electrode active material, allowing it to be doped into the positive electrode active material and improve the cycle stability of the positive electrode active material. Therefore, the composite positive electrode material of the embodiment of the present application can be applied to secondary batteries to further improve the rate performance and cycle performance of the battery.

[0086] Ionic conductivity has a meaning well known in the art and can be measured by equipment and methods known in the art. For example, the ionic conductivity of a lithium ion conductor material can be determined by electrochemical impedance spectroscopy (EIS). Specifically, an appropriate amount of lithium ion conductor material can be placed between two stainless steel sheets as blocking electrodes to form a symmetrical battery; the electrochemical workstation used can be DH7001, and the frequency range can be 0.01Hz-106Hz, and the EIS of the lithium ion conductor material at 25°C is tested. The ionic conductivity calculation formula is as follows: δ=L / (R·S), wherein δ is the ionic conductivity (unit is S / cm), L is the thickness of the lithium ion conductor material between the two stainless steel sheets (unit is cm), R is the intrinsic resistance of the lithium ion conductor material (unit is Ω), and S is the effective cross-sectional area of ​​the lithium ion conductor material (unit is cm 2 ).

[0087] In some embodiments, the lithium ion conductor material may include at least one of lithium zinc germanium oxide (LISICON structure lithium conductive ceramic powder), lithium aluminum titanium phosphate (LATP), lithium aluminum germanium phosphate (LAGP), lithium lanthanum titanate, glassy lithium conductive electrolyte powder, or garnet structure lithium conductive electrolyte powder.

[0088] Alternatively, in some embodiments, the lithium ion conductor material may include at least one of lithium aluminum titanium phosphate (LAGP) and lithium aluminum germanium phosphate (LAGP).

[0089] Without intending to be bound by any theory or explanation, the lithium ion conductor materials selected from the above categories have suitable ionic conductivity, which can result in a higher ionic conductivity of the coating layer and a higher kinetic reaction rate of the M element. This can further improve the rate capability and cycle performance of the battery.

[0090] In some embodiments, the volume distribution particle size Dv50 of the particles containing the M element is ≤ 2 μm, for example, it can be 2 μm, 1.8 μm, 1.5 μm, 1.2 μm, 1 μm, 800 nm, 500 nm, 300 nm, 200 nm, or a range consisting of any two of the above values.

[0091] Optionally, in some embodiments, the volume distribution particle size of the particles can also be 0.3 μm-1 μm, 0.3 μm-0.8 μm, 0.3 μm-0.5 μm, 0.4 μm-1 μm, 0.4 μm-0.8 μm, 0.4 μm-0.6 μm, 0.5 μm-1 μm, and the like.

[0092] Without intending to be bound by any theory or explanation, when the particles containing the M element have the aforementioned smaller volume distribution particle size, they generally have a larger specific surface area, thereby increasing the contact area between the composite material and the positive electrode active material. This facilitates the coating layer to be more tightly coated on the surface of the positive electrode active material, inhibiting side reactions between the positive electrode active material and air, thereby inhibiting the generation of RLCs. Therefore, the composite positive electrode material of the embodiment of the present application is applied to a secondary battery to improve the battery's cycle performance and storage performance.

[0093] In some embodiments, the volume distribution particle size Dv50 of the lithium ion conductor material is ≤100 nm, for example, 100 nm, 90 nm, 80 nm, 70 nm, 60 nm, 50 nm, 40 nm, 30 nm, 20 nm, 10 nm, or a range consisting of any two of the above values.

[0094] Optionally, in some embodiments, the volume distribution particle size of the lithium ion conductor material can be 20 nm-50 nm, for example, 20 nm, 22 nm, 25 nm, 28 nm, 30 nm, 33 nm, 36 nm, 39 nm, 40 nm, 41 nm, 44 nm, 47 nm, 50 nm, or a range consisting of any two of the above values.

[0095] Without intending to be bound by any theory or explanation, when the lithium ion conductor material has the aforementioned smaller volume distribution particle size, it generally has a larger specific surface area, thereby increasing the contact area between the lithium ion conductor material and the M element and the positive electrode active material. This is beneficial for further improving the ion transport rate of the composite positive electrode material and the kinetic reaction rate of the M element, thereby improving the rate performance and cycle performance of the battery.

[0096] In some embodiments, the volume distribution particle size Dv50 of the positive electrode active material can be 5μm-15μm, for example, it can be 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm, 15μm, or a range consisting of any two of the above values.

[0097] Without intending to be bound by any theory or explanation, when the volume distribution particle size of the positive electrode active material is within the above-mentioned suitable range, the composite positive electrode material can have a higher theoretical specific capacity and a suitable ion transport pathway. This is conducive to improving the capacity of the composite positive electrode material, thereby increasing the energy density of the battery.

[0098] In some embodiments, the volume distribution particle size Dv50 of the composite positive electrode material can be 8μm-20μm, for example, it can be 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm, 15μm, 16μm, 17μm, 18μm, 19μm, 20μm, or a range consisting of any two of the above values.

[0099] Without intending to be bound by any theory or explanation, when the volume distribution particle size of the composite cathode material is within the above-mentioned suitable range, it can have a suitable ion transport path, thereby facilitating an improvement in the ion transport rate of the composite cathode material, thereby further improving the rate performance of the battery.

[0100] The volume distribution particle size Dv50 has a meaning well known in the art and may represent the particle size corresponding to the cumulative volume distribution percentage of a material reaching 50%. The volume distribution particle size Dv50 may be measured using equipment and methods known in the art. The volume distribution particle size Dv50 may be measured using laser diffraction particle size analysis. For example, the measurement may be performed using a laser particle size analyzer (e.g., Malvern Master Size 3000) in accordance with standard GB / T 19077-2016.

[0101] In some embodiments, based on the total mass of the composite positive electrode material, the mass percentage of the positive electrode active material may be 80%-98%, optionally 90%-95%.

[0102] In some embodiments, based on the total mass of the composite positive electrode material, the mass percentage of the particles containing M element may be 0.02%-5%, and optionally 0.05%-2%.

[0103] In some embodiments, based on the total mass of the composite positive electrode material, the mass percentage of the lithium ion conductor material may be 0.01%-1%, and optionally 0.05%-1%.

[0104] Without intending to be bound by any theory or explanation, when the content of each component in the composite cathode material falls within the given range, the composite cathode material can achieve both a high theoretical specific capacity and a high ionic conductivity, while also reducing the risk of RLCs forming on the surface of the cathode active material. Furthermore, when the content of the lithium ion conductor material falls within the given range, the risk of gelation in the cathode slurry can be reduced, thereby improving the processability of the composite cathode material and, in turn, increasing battery production capacity.

[0105] In the composite positive electrode material, the mass percentage of the positive electrode active material, the particles containing the M element, and the lithium ion conductor material can be measured by equipment and methods known in the art, for example, by inductively coupled plasma optical emission spectrometry (ICP). Specifically, the elemental composition and content of the composite positive electrode material can be determined by elemental analysis using inductively coupled plasma optical emission spectrometry (ICP, Ametek, model: SPECTROARCOS ICP-OES) with reference to standards YS / T1006.2-2014, GB / T23367.2-2009, or YS / T1028.5-2015, thereby determining the mass percentage of the positive electrode active material, the particles, and the lithium ion conductor material.

[0106] In some embodiments, the composite material may be attached to the surface of the positive electrode active material via a binder to form a coating layer.

[0107] Alternatively, in some embodiments, the lithium ion conductor material may be attached to the surface of the particles containing the M element via a binder.

[0108] Without intending to be bound by any theory or explanation, the composite material is attached to the surface of the positive electrode active material via a binder, allowing the composite material to be firmly anchored to the surface of the positive electrode active material, thereby improving the interfacial stability between the coating layer and the positive electrode active material. This helps further reduce the risk of RLCs forming on the surface of the positive electrode active material and improves the cycling stability of the composite cathode material, thereby improving the cycling performance and storage performance of the battery.

[0109] Examples of the binder may include one or more binders known in the art, including, but not limited to, at least one of polyvinylidene fluoride, polytetrafluoroethylene, sodium carboxymethyl cellulose, and styrene-butadiene rubber. Those skilled in the art may select an appropriate binder based on actual application needs, provided that the composite material can adhere to the surface of the positive electrode active material to form a coating layer, and the binder is not limited here.

[0110] In some embodiments, the adhesive may include a castor oil-based UV oligomer adhesive.

[0111] Alternatively, the castor oil-based UV oligomer adhesive may include a castor oil-based UV oligomer having a molecular weight of 200 Da to 800 Da.

[0112] Without intending to be limited by any theory or explanation, castor oil-based UV oligomer binders have good bonding properties, which can not only make the lithium ion conductor material tightly adhere to the surface of the particles containing the M element, and firmly anchor the composite material to the surface of the positive electrode active material, but also make the composite positive electrode material and the positive electrode current collector have good bonding strength. In addition, after ultraviolet light curing, castor oil-based UV oligomer binders can also form a tight cross-linked network, thereby improving the cohesion of the positive electrode film layer. As a result, not only the structural stability of the composite positive electrode material can be improved, but also the structural stability of the positive electrode sheet can be improved, thereby improving the cycle performance of the battery and extending the cycle life of the battery. In addition, castor oil-based UV oligomer binders also have good conductive properties. Such as Figure 2 As shown, castor oil-based UV oligomer binder 121c can be distributed between particles of lithium ion conductor material 121b and between composite material 121 and positive electrode active material 110, forming a network with both binding and conductive properties. This can also increase the electron transfer rate of the composite positive electrode material, thereby reducing the bulk impedance of the composite positive electrode material and improving the battery's cycling performance, storage performance, and rate capability.

[0113] The above molecular weight has a well-known meaning in the art and can be determined by equipment and methods known in the art, for example, by mass spectrometry according to the test standard GB / T 6041-2020.

[0114] In the embodiments of the present application, the castor oil-based UV oligomer adhesive is a substance known in the art and may include a castor oil-based UV oligomer, a photoinitiator, and optional additives. The castor oil-based UV oligomer adhesive can be obtained in various ways, such as commercially available or prepared by methods known in the art.

[0115] As an example, a castor oil-based UV oligomer adhesive can be prepared through the following steps (1) to (3).

[0116] (1) Using a reactive diluent, isocyanate, and castor oil as raw materials, the reaction is carried out until the mass fraction of the isocyanate group in the feed amount reaches half of the theoretical value before the start of the reaction, thereby obtaining an isocyanate semi-blocked intermediate.

[0117] In step (1), the temperature and time of the reaction are not specifically limited, and those skilled in the art can adjust them according to the reaction materials, feed amount, etc. As an example, the reaction temperature can be 30°C-70°C, and the reaction time can be 2h-7h. The reactive diluent can be selected from at least one of isobornyl methacrylate (IBOMA), tripropylene glycol diacrylate (TPGDA), and 1,6-hexanediol diacrylate (HDDA). The isocyanate can be selected from isocyanates known in the art. In some embodiments, the isocyanate may include one or more diisocyanates. In some embodiments, the molar ratio of isocyanate to castor oil can be (2.7:1)-(2.9:1), and the amount of the reactive diluent can be 10%-40% of the total mass of the reaction materials in step (1).

[0118] (2) mixing the isocyanate semi-blocked intermediate with hydroxy acrylate, adding an antioxidant, and reacting the isocyanate semi-blocked intermediate with hydroxy acrylate until the isocyanate group content is less than 0.5%, and adding anhydrous ethanol to block the end to obtain a castor oil-based polyurethane acrylic resin.

[0119] In step (2), the reaction temperature and time are not specifically limited and can be adjusted by those skilled in the art according to the reaction materials, feed amount, etc. As an example, the reaction temperature can be 70°C-100°C and the reaction time can be 4h-9h. In some embodiments, the hydroxy acrylate can include at least one of hydroxyethyl acrylate (HEA), hydroxypropyl acrylate (HPA), and hydroxypropyl methacrylate (HPMA); the molar ratio of isocyanate to hydroxy acrylate can be (1:1.05)-(1:1.2). The antioxidant can include any one of 2,6-di-tert-butyl-p-cresol (Antioxidant 264), pentaerythritol (Antioxidant 1000), and 3,5-di-tert-butyl-4-hydroxyphenylpropionic acid octadecyl ester (Antioxidant 1076), and the amount used can be 0.1%-0.5% of the total mass of the reaction materials.

[0120] (3) Mix castor oil-based polyurethane acrylic resin, photoinitiator, dispersant and leveling agent, stir evenly at 30°C-50°C in the dark, add pigment and defoamer, and mix evenly to obtain castor oil-based UV oligomer adhesive.

[0121] In step (3), the amount of castor oil-based polyurethane acrylic resin, photoinitiator, dispersant, and leveling agent added is not particularly limited and can be adjusted as needed by those skilled in the art. As an example, the mass ratio of castor oil-based polyurethane acrylic resin, photoinitiator, dispersant, leveling agent, pigment, and defoamer can be (80-90):(3-7):(0.1-1):(0.1-1):(1-5):(0.1-0.5).

[0122] As another example, castor oil-based UV oligomer adhesives can also be prepared using a one-pot, two-step process. The castor oil-based UV oligomers prepared using this one-pot, two-step process have a narrow molecular weight distribution and can exhibit suitable viscosity, excellent bonding properties, and good electrical conductivity. The one-pot, two-step process can specifically include the following steps (4) to (6).

[0123] (4) 30-50 parts by mass of diisocyanate and 40-50 parts by mass of castor oil are mixed uniformly, and the mixture is heated to 40-50° C. and reacted for 2-4 hours to obtain an intermediate.

[0124] (5) Add 20-30 parts by mass of hydroxy acrylate, 0.05%-0.15% of the total mass of the reaction raw materials as a catalyst and 0.05%-0.2% of the total mass of the reaction raw materials as an antioxidant to the intermediate, heat to 70-80°C, react for 3-4 hours, then add 3%-5% of the total mass of the reaction raw materials as an anhydrous ethanol, stir evenly, and obtain a mixture containing castor oil-based UV oligomer. Wherein, the diisocyanate may include one or more diisocyanates known in the art, for example, at least one of isophorone diisocyanate (IPDI), toluene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), p-phenylene diisocyanate (PPDI), and cyclohexane dimethylene diisocyanate (HXDI). The hydroxy acrylate may include at least one of hydroxyethyl acrylate, hydroxypropyl acrylate, and hydroxypropyl methacrylate. The catalyst may include at least one of dibutyltin dilaurate, triethanolamine, bismuth cyclohexane, cobalt octoate, and triethylenediamine. The antioxidant may include hydroquinone and / or 2,6-di-tert-butyl-p-cresol.

[0125] (6) The above mixture, photoinitiator, dispersant and leveling agent are mixed, stirred evenly at 30°C-50°C in the dark, and then pigment and defoaming agent are added and mixed evenly to obtain a castor oil-based UV oligomer adhesive.

[0126] In step (6), the amounts of the mixture, photoinitiator, dispersant, and leveling agent added are not particularly limited and can be adjusted as needed by those skilled in the art. As an example, the mass ratio of the mixture, photoinitiator, dispersant, leveling agent, pigment, and defoamer can be (80-90):(3-7):(0.1-1):(0.1-1):(1-5):(0.1-0.5).

[0127] In some embodiments, the positive electrode active material may include a nickel-cobalt-manganese ternary material and / or a nickel-cobalt-aluminum ternary material.

[0128] Optionally, in the nickel-cobalt-manganese ternary material, the molar content of Ni element in the transition metal elements is greater than or equal to 0.6.

[0129] Optionally, in the nickel-cobalt-aluminum ternary material, the molar content of Ni element in the transition metal elements is greater than or equal to 0.6.

[0130] Without intending to be bound by any theory or explanation, the composite cathode materials of the embodiments of the present application have a specific coating layer, which can inhibit the generation of RLCs on the surface of the cathode active material and improve the ionic conductivity of the composite cathode material. This is conducive to the application of high-nickel-content ternary cathode active materials in secondary batteries, thereby allowing the secondary batteries to have high energy density, good cycle performance, storage performance, and rate performance.

[0131] Preparation method

[0132] In a second aspect, an embodiment of the present application provides a method for preparing a composite positive electrode material, comprising the following steps S10 to S20.

[0133] S10, preparing a composite material, including mixing particles containing M element with a lithium ion conductor material, and allowing the lithium ion conductor material to adhere to the surface of the particles containing M element to obtain a composite material, wherein M includes at least one of S, Se, and Te.

[0134] In step S10, the lithium ion conductor material can be attached to the surface of the particles containing the M element in a variety of ways. For example, the particles containing the M element can be mixed with the lithium ion conductor material and ball-milled to attach the lithium ion conductor material to the surface of the particles containing the M element, or the particles containing the M element can be mixed with the lithium ion conductor material and a binder and ball-milled to attach the lithium ion conductor material to the surface of the particles containing the M element via the binder. Those skilled in the art can select an appropriate method based on actual needs, and this is not limited here. The lithium ion conductor material can be selected from the lithium ion conductor material described in the first aspect. The implementation of the lithium ion conductor material has been described and explained in detail above and will not be repeated here.

[0135] S20, preparing a composite positive electrode material, including uniformly mixing the composite material with the positive electrode active material, and coating the composite material on at least a portion of the surface of the positive electrode active material to obtain the composite positive electrode material.

[0136] In step S20, coating the composite material on at least a portion of the surface of the positive electrode active material can be achieved in a variety of ways. In some embodiments, the composite material, the positive electrode active material and the binder can be evenly mixed so that the composite material is attached to at least a portion of the surface of the positive electrode active material through the binder, thereby forming a coating layer. In some embodiments, the composite material and / or the positive electrode active material can also be modified so that the composite material is attached to at least a portion of the surface of the positive electrode active material through chemical bonding, thereby forming a coating layer. Those skilled in the art can select a suitable embodiment according to the needs of the actual application, on the premise that the composite material can be attached to the surface of the positive electrode active material to form a coating layer, and this is not limited here.

[0137] According to the method of the embodiment of the present application, a composite positive electrode material is prepared, including a positive electrode active material and a coating layer, and the coating layer contains a composite material, which can effectively improve the cycle performance, storage performance and rate performance of the battery. Specifically, the coating layer of the composite positive electrode material includes the above-mentioned particles containing the M element. During the processing or storage process of the battery, the coating layer can inhibit the contact between the positive electrode active material and the air, thereby inhibiting the generation of RLCs; the coating layer of the composite material also includes a lithium ion conductor material attached to the surface of the particles containing the M element. The lithium ion conductor material can construct a good ion conductive network at the material level, thereby improving the ion transmission rate of the composite positive electrode material. Compared with the technical solution of directly coating the sulfide element on the surface of the positive electrode active material in the related art, the composite positive electrode material prepared according to the method of the embodiment of the present application has the advantage of higher ion conductivity.

[0138] In addition, when the positive electrode active material is a ternary positive electrode material, during the battery formation process, the M element can also react with the positive electrode active material, replacing some of the oxygen atoms on the surface of the positive electrode active material, thereby doping into the positive electrode active material. Compared with oxygen atoms, M atoms have stronger electronegativity and larger atomic radius. Doping into the positive electrode active material can not only enhance the ionic conductivity of the positive electrode active material, but also widen the interlayer spacing of the positive electrode active material, inhibiting the migration of lithium ions and transition metal layers. As a result, the cycle stability of the positive electrode active material can also be improved, delaying the voltage drop and capacity decay of the battery.

[0139] Therefore, the composite positive electrode material prepared according to the method of the embodiment of the present application is applied to a secondary battery, which can effectively improve the cycle performance, storage performance and rate performance of the battery.

[0140] In some embodiments, preparing the composite material may specifically include: mixing particles containing M element, a lithium ion conductor material, and a castor oil-based UV oligomer binder and ball milling the mixture to obtain a slurry containing the composite material.

[0141] The preparation of the composite positive electrode material may specifically include: uniformly mixing the slurry and the positive electrode active material, and then curing the castor oil-based UV oligomer binder to coat at least a portion of the surface of the positive electrode active material with the composite material to obtain the composite positive electrode material.

[0142] The castor oil-based UV oligomer adhesive can be selected from the castor oil-based UV oligomer adhesive described in the first aspect. The implementation of the castor oil-based UV oligomer adhesive has been described and illustrated in detail above and will not be repeated here.

[0143] Castor oil-based UV oligomer binders not only possess excellent bonding properties but also, after UV curing, form a tight cross-linked network, thereby enhancing the cohesion of the cathode film. This improves the structural stability of both the composite cathode material and the cathode electrode sheet, thereby enhancing the battery's cycling performance and extending its cycle life. Furthermore, castor oil-based UV oligomer binders possess excellent electrical conductivity, which increases the electron transfer rate of the composite cathode material, thereby reducing the bulk impedance of the composite cathode material and, in turn, improving the battery's cycling, storage, and rate capabilities.

[0144] In some embodiments, the mass ratio of the particles containing M element to the lithium ion conductor material may be 1:0.3-1:0.6.

[0145] Without intending to be bound by any theory or explanation, when the mass ratio of the particles containing M to the lithium ion conductor material falls within the given range, an appropriate amount of the lithium ion conductor material can be attached to the surface of the particles containing M, thereby improving the ionic conductivity of the composite positive electrode material and reducing the risk of RLCs forming on the surface of the positive electrode active material. Furthermore, when the mass ratio of the particles containing M to the lithium ion conductor material falls within the given range, the risk of gelation in the positive electrode slurry can be reduced, thereby improving the processability of the composite positive electrode material.

[0146] In some embodiments, the mass ratio of the particles containing M element to the castor oil-based UV oligomer binder may be 1:0.1-1:0.3.

[0147] Without intending to be bound by any theory or explanation, when the mass ratio of the particles to the castor oil-based UV oligomer binder falls within the given range, the lithium ion conductor material can be tightly attached to the surface of the particles containing the M element, and the composite material can be firmly anchored to the surface of the positive electrode active material, thereby improving the structural stability of the composite positive electrode material and reducing the bulk impedance of the composite positive electrode material. This can improve the battery's cycling performance, storage performance, and rate capability.

[0148] Positive electrode

[0149] In a third aspect, an embodiment of the present application provides a positive electrode sheet, comprising a positive electrode current collector and a positive electrode film layer located on at least one side of the positive electrode current collector. The positive electrode film layer comprises the composite positive electrode material of the first aspect, or the composite positive electrode material prepared according to the method of the second aspect.

[0150] The positive electrode plate of the embodiment of the present application includes the composite positive electrode material of the first aspect, or the composite positive electrode material prepared according to the method of the second aspect, and is applied to a secondary battery, which can enable the secondary battery to have good cycle performance, storage performance and rate performance.

[0151] In some embodiments, the positive electrode film layer may further include a positive electrode conductive agent. The present application does not particularly limit the type of the positive electrode conductive agent. For example, the positive electrode conductive agent may include at least one of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0152] In some embodiments, the positive electrode film layer may further optionally include a positive electrode binder. This application does not particularly limit the type of positive electrode binder. As an example, the positive electrode 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 acrylic resin.

[0153] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. As an example of a metal foil, aluminum foil may be used. The composite current collector may include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. As an example, the metal material may include at least one of aluminum, an aluminum alloy, nickel, a nickel alloy, titanium, a titanium alloy, silver, and a silver alloy. As an example, the polymer material base layer may include at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0154] The positive electrode film is typically formed by coating a positive electrode slurry onto a positive electrode current collector, drying it, and cold pressing it. The positive electrode slurry is typically formed by dispersing the positive electrode active material, an optional conductive agent, an optional binder, and any other components in a solvent and stirring them uniformly. The solvent may be, but is not limited to, N-methylpyrrolidone (NMP).

[0155] Battery

[0156] The battery mentioned in the embodiments of the present application may include one or more battery cells to provide a single physical module with higher voltage and capacity. When there are multiple battery cells, the multiple battery cells are connected in series, in parallel or in hybrid through a busbar.

[0157] Typically, a battery cell includes an electrode assembly and an electrolyte. The electrode assembly includes a positive electrode, a negative electrode, and a separator. During the charge and discharge process of the battery cell, active ions (such as lithium ions) are embedded and extracted back and forth between the positive electrode and the negative electrode. The separator is set between the positive electrode and the negative electrode to prevent the positive and negative electrodes from short-circuiting while allowing active ions to pass through. The electrolyte plays the role of conducting active ions between the positive electrode sheet and the negative electrode sheet.

[0158] [Positive electrode]

[0159] In the battery cells of the embodiments of the present application, the positive electrode sheet of the electrode assembly may include the positive electrode sheet of the third aspect. The embodiments of the positive electrode sheet have been described and illustrated in detail above and will not be repeated here. It is understood that the battery cells of the embodiments of the present application can achieve the beneficial effects of any of the aforementioned embodiments of the positive electrode sheet of the embodiments of the present application.

[0160] [Negative electrode]

[0161] The negative electrode sheet may include a negative electrode current collector and a negative electrode film layer disposed on at least one side of the negative electrode current collector and comprising a negative electrode active material. For example, the negative electrode current collector may have two opposing surfaces in its thickness direction, and the negative electrode film layer may be disposed on either or both of the two opposing surfaces of the negative electrode current collector.

[0162] The negative electrode active material may be any negative electrode active material known in the art for use in secondary batteries. For example, the negative electrode active material may include, but is not limited to, at least one of natural graphite, artificial graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate. Silicon-based materials may include at least one of elemental silicon, silicon oxide, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials may include at least one of elemental tin, tin oxide, and tin alloys.

[0163] In some embodiments, the negative electrode film layer may further optionally include a negative electrode conductive agent. The present application does not particularly limit the type of the negative electrode conductive agent. As an example, the negative electrode conductive agent may include at least one of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0164] In some embodiments, the negative electrode film layer may further optionally include a negative electrode binder. The present application does not particularly limit the type of the negative electrode binder. As examples, the negative electrode binder may include at least one of styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, water-based acrylic resin (e.g., polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).

[0165] In some embodiments, the negative electrode film layer may optionally include other additives. For example, the other additives may include a thickener, such as sodium carboxymethyl cellulose (CMC-Na), a PTC thermistor material, and the like.

[0166] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. As an example of a metal foil, copper foil may be used. The composite current collector may include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. As an example, the metal material may include at least one of copper, a copper alloy, nickel, a nickel alloy, titanium, a titanium alloy, silver, and a silver alloy. As an example, the polymer material base layer may include at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0167] The negative electrode film layer is typically formed by coating the negative electrode slurry onto the negative electrode current collector, drying it, and cold pressing it. The negative electrode slurry is typically formed by dispersing the negative electrode active material, an optional conductive agent, an optional binder, and other optional additives in a solvent and stirring them uniformly. The solvent can be, but is not limited to, N-methylpyrrolidone (NMP) or deionized water.

[0168] The negative electrode plate does not exclude other additional functional layers in addition to the negative electrode film layer. For example, in some embodiments, the negative electrode plate also includes a conductive primer layer (e.g., composed of a conductive agent and a binder) sandwiched between the negative electrode current collector and the negative electrode film layer and disposed on the surface of the negative electrode current collector. In some embodiments, the negative electrode plate of the present application also includes a protective layer covering the surface of the negative electrode film layer.

[0169] [Isolation film]

[0170] The separator is disposed between the positive electrode and the negative electrode to serve as an isolation film. The present invention has no particular limitation on the type of separator, and any known porous separator with good chemical and mechanical stability can be selected.

[0171] In some embodiments, the material of the separator can be selected from one or more of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0172] [Electrolytes]

[0173] The electrolyte conducts ions between the positive and negative electrodes. The present invention does not specifically limit the type of electrolyte, and the electrolyte can be selected based on the needs. For example, the electrolyte can be in liquid or gel form.

[0174] In some embodiments, the electrolyte is an electrolyte solution comprising an electrolyte salt and a solvent.

[0175] In some embodiments, the electrolyte salt may be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalatoborate, lithium dioxalatoborate, lithium difluorodioxalatophosphate, and lithium tetrafluorooxalatophosphate.

[0176] In some embodiments, the solvent can be selected from at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methylpropyl carbonate, ethylpropyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclopentane, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.

[0177] In some embodiments, the electrolyte may further include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, and additives that improve battery high or low temperature performance.

[0178] In some embodiments, the positive electrode sheet, the separator, and the negative electrode sheet may be formed into an electrode assembly through a winding process or a lamination process.

[0179] In some embodiments, the battery cell further includes a housing for housing the electrode assembly and electrolyte. The housing of the battery cell may be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. Alternatively, the housing of the battery cell may be a soft shell, such as a pouch-type soft shell. The soft shell may be made of plastic, such as polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0180] The embodiment of the present application has no particular limitation on the shape of the battery cell, which can be cylindrical, square or any other shape. For example, Figure 3 The battery cell 5 is a square structure as an example.

[0181] In some embodiments, reference Figure 4, the outer shell may include a shell 51 and a cover plate 53. The shell 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 51 has an opening connected to the receiving cavity, and the cover plate 53 can be covered on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the isolation membrane can form an electrode assembly 52 through a winding process or a lamination process. The electrode assembly 52 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the battery cell 5 can be one or more, and those skilled in the art can select according to specific actual needs.

[0182] The preparation method of the battery cell of the embodiment of the present application is well known. In some embodiments, the electrode assembly can be placed in a housing, dried, injected with electrolyte, and then vacuum packaged, allowed to stand, formed, and shaped to obtain a battery cell.

[0183] In some embodiments, the battery referred to in the embodiments of this application refers to a single physical module comprising one or more battery cells to provide higher voltage and capacity. For example, the battery referred to in the embodiments of this application may be a battery module or a battery pack. Batteries generally include a housing for enclosing one or more battery cells. The housing prevents liquids or other foreign matter from affecting the charging or discharging of the battery cells.

[0184] In some embodiments, a battery may contain multiple battery cells, which may be connected in series, in parallel, or in a hybrid configuration. A hybrid configuration refers to a combination of series and parallel connections. Multiple battery cells may be directly connected in series, in parallel, or in a hybrid configuration, and then the entire battery cell structure is housed within a housing. Alternatively, multiple battery cells may be first connected in series, in parallel, or in a hybrid configuration to form a battery module, which is then further connected in series, in parallel, or in a hybrid configuration to form a single unit and housed within a housing.

[0185] Figure 5 FIG. 4 is a schematic diagram of a battery module 4 as an example. Figure 5 As shown, there are multiple battery cells 5, which are first connected in series, parallel, or in series to form a battery module 4. The multiple battery cells 5 in the battery module 4 can be electrically connected via a busbar component to achieve the series, parallel, or in series connection of the multiple battery cells 5 in the battery module 4. In the battery module 4, the multiple battery cells 5 can be arranged sequentially along the length of the battery module 4. Of course, they can also be arranged in any other manner. Furthermore, the multiple battery cells 5 can be secured using fasteners.

[0186] In some embodiments, the battery modules described above may also be assembled into a battery pack, and the number of battery modules contained in the battery pack may be adjusted according to the application and capacity of the battery pack.

[0187] Figure 6 and Figure 7 FIG. 1 is a schematic diagram of a battery pack 1 as an example. Figure 6 and Figure 7 As shown, a battery pack 1 may include a housing and multiple battery modules 4 disposed therein. The multiple battery modules 4 in the battery pack 1 may be electrically connected via a busbar assembly to enable series, parallel, or mixed connection of the multiple battery modules 4 in the battery pack 1. The housing includes an upper housing 2 and a lower housing 3. The upper housing 2 covers the lower housing 3 and forms an enclosed space for accommodating the battery modules 4. The multiple battery modules 4 may be arranged in any manner within the battery box.

[0188] Electrical devices

[0189] The embodiments of the present application also provide an electric device, which includes a battery cell provided in the embodiments of the present application, and the battery cell is used to provide electrical energy. The battery cell can be used as a power source for the electric device, and can also be used as an energy storage unit for the electric device. The electric device may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but is not limited thereto.

[0190] As the electrical device, a battery cell, a battery module including a plurality of battery cells, or a battery pack can be selected according to its usage requirements.

[0191] Figure 8 This is an example of an electric device. This electric device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of this electric device, a battery pack or battery module can be used.

[0192] As another example, an electric device may be a mobile phone, a tablet computer, a laptop computer, etc. Such a device is usually required to be light and thin, and may use a battery cell as a power source.

[0193] Example

[0194] Below, the embodiment of the present application is described. The embodiment described below is exemplary and is only used to explain the present application, and is not to be construed as limiting the present application. Where specific techniques or conditions are not specified in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. Reagents or instruments used that do not specify the manufacturer are conventional products that can be obtained commercially.

[0195] Example 1

[0196] Preparation of composite cathode materials

[0197] The M-containing particles (S-containing particles) with a volume distribution particle size Dv50 of 1 μm, the lithium ion conductor material (lithium zinc germanate) and the binder (castor oil-based UV oligomer binder) were mixed and ball-milled in a mass ratio of 3.6:90:6.4 to obtain a slurry containing a composite material. The ionic conductivity δ of the lithium ion conductor material is 1.2×10 -2 S / cm, and the molecular weight of the castor oil-based UV oligomer in the binder is 500Da.

[0198] The above slurry is mixed with the positive electrode active material LiNi 0.9 Co 0.05 Mn 0.05 After uniformly mixing the NCM955 and the castor oil-based UV oligomer binder, the binder is cured under ultraviolet light to coat at least a portion of the surface of the positive electrode active material with the composite material, thereby obtaining a composite positive electrode material. The weight percentage w1 of the particles containing the M element is 0.02%, and the weight percentage w2 of the lithium ion conductor material is 0.5%, based on the total weight of the composite positive electrode material.

[0199] Preparation of positive electrode

[0200] The composite positive electrode material, conductive agent acetylene black, and binder polyvinylidene fluoride (PVDF) are mixed uniformly in an appropriate amount of solvent N-methylpyrrolidone (NMP) at a mass ratio of 96.5:1.5:2 to obtain a positive electrode slurry; the positive electrode slurry is coated on the positive electrode current collector aluminum foil, and the positive electrode sheet is obtained through processes such as drying, cold pressing, slitting, and cutting.

[0201] Preparation of negative electrode sheet

[0202] The negative electrode active material artificial graphite, silicon oxide, conductive agent acetylene black, binder styrene butadiene rubber (SBR) and sodium carboxymethyl cellulose (CMC) are mixed evenly in an appropriate amount of solvent deionized water according to a mass ratio of 90:5:2:2:1 to obtain a negative electrode slurry; the negative electrode slurry is coated on the negative electrode current collector copper foil, and the negative electrode sheet is obtained through the processes of drying, cold pressing, slitting and cutting.

[0203] Preparation of isolation membrane

[0204] Polyethylene film is used as the isolation film.

[0205] Preparation of electrolyte

[0206] Lithium salt (LiPF6 and LiFSI mixed in a mass ratio of 2:8) was dissolved in a solvent prepared by ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) in a volume ratio of 1:1:1 to obtain an electrolyte with a lithium salt concentration of 1 mol / L.

[0207] Preparation of secondary batteries

[0208] The positive electrode sheet, separator, and negative electrode sheet are stacked and wound in sequence to obtain an electrode assembly; the electrode assembly is placed in an outer package, dried, and then injected with electrolyte. After vacuum packaging, standing, formation, shaping and other processes, a secondary battery is obtained.

[0209] Example 2-19

[0210] Based on the preparation process of the composite positive electrode material in Example 1, the type of positive electrode active material, the type of particles containing M element, the volume distribution particle size Dv50 of the particles containing M element, the type of lithium ion conductor material, the type of binder, w1, and w2 were adjusted as shown in Table 1 to prepare the composite positive electrode materials of Examples 2-19. Among them, the adjustment of w1 and w2 can be achieved by adjusting the amount of at least one of the positive electrode active material, the particles containing M element, and the lithium ion conductor material. The positive electrode active material of Example 18 is LiNi 0.9 Co 0.05 Al 0.05 (NCA955).

[0211] The preparation of the positive electrode sheet, negative electrode sheet, separator, electrolyte and secondary battery of Examples 2-19 is the same as that of Example 1.

[0212] Comparative Example 1-2

[0213] Based on the preparation process of the composite positive electrode material in Example 1, the preparation parameters of the composite positive electrode material were adjusted as shown in Table 1 to prepare the composite positive electrode material of Comparative Example 1-2.

[0214] The preparation of the positive electrode sheet, negative electrode sheet, separator, electrolyte and secondary battery of Comparative Example 1-2 is the same as that of Example 1.

[0215] Test section

[0216] (1) Initial DCR test

[0217] At 25°C, the secondary battery was charged at a constant current rate of 0.33C to 4.25V, then charged at a constant voltage of 4.25V to a cutoff current of 0.05C, allowed to stand for 5 minutes, and then discharged at a constant current rate of 0.33C to a termination voltage of 2.8V to obtain the initial discharge capacity C0.

[0218] At 25°C, the secondary battery was allowed to rest for 30 minutes, then charged to 4.25V at a constant current rate of 0.33C0. Then, it was charged to a cutoff current of 0.05C0 at a constant voltage rate of 4.25V and allowed to rest for 10 minutes. Then, it was discharged to 50% SOC at a constant current rate of 0.33C0. It was allowed to rest for 60 minutes, and the voltage at this point was recorded as U0. Then, it was discharged at a rate of 4C0 for 10 seconds, and the voltage U at the 10th second of discharge was recorded. Calculate the initial DCR of the battery = (U-U0) / the current corresponding to the 4C0 rate.

[0219] (2) Storage performance test

[0220] At 25°C, the secondary battery was charged at a constant current rate of 0.33C to 4.25V, then charged at a constant voltage of 4.25V to a cutoff current of 0.05C, allowed to stand for 5 minutes, and then discharged at a constant current rate of 0.33C to a termination voltage of 2.8V to obtain the initial discharge capacity C0.

[0221] The secondary battery was charged to 4.25V at a constant current of 0.33C, then charged to a cutoff current of 0.05C at a constant voltage of 4.25V, and then stored in an environment of 60°C for 60 days. After that, the secondary battery was taken out and cooled to 25°C. At 25°C, it was discharged to 2.8V at a constant current of 0.33C, then charged to a cutoff voltage of 4.25V at a constant current of 0.33C, and then charged to a cutoff current of 0.05C at a constant voltage of 4.25V. After standing for 5 minutes, it was discharged to a cutoff voltage of 2.8V at a constant current of 0.33C, and the discharge capacity after high temperature storage was obtained. 60 Storage capacity retention rate of secondary battery = C 60 / C0×100%.

[0222] Subsequently, the secondary battery was allowed to stand for 30 minutes at 25°C, then charged to 4.25V at a constant current rate of 0.33C, then charged to a cutoff current of 0.05C at a constant voltage rate of 4.25V, allowed to stand for 10 minutes, and then discharged to 50% SOC at a constant current rate of 0.33C, allowed to stand for 60 minutes, and the voltage at this time was recorded as U a Then, discharge at a rate of 4C for 10s and record the voltage U at the 10th second of discharge. b .

[0223] Calculate the battery storage DCR = (U a -U b ) / 4C rate corresponding current. Storage DCR growth rate of secondary battery = (storage DCR-initial DCR) / initial DCR×100%.

[0224] (3) Cyclic performance test

[0225] Keep the secondary battery at 45℃ for 2h, let it stand for 5min, then charge it to 4.25V at a constant current of 1 / 3C, then charge it to a cutoff current of 0.05C at a constant voltage of 4.25V, let it stand for 5min, and discharge it to 2.8V at a constant current of 0.5C, let it stand for 5min. This is one charge and discharge cycle. Repeat the above steps for the same secondary battery, and record the discharge capacity D0 of the first cycle and the discharge capacity D of the 2000th cycle. 2000 . Cycle capacity retention rate P of secondary battery 2000 =D 2000 / D0×100%.

[0226] (4) Rate performance test

[0227] At 25°C, the secondary battery was charged at a constant current rate of 0.33C to 4.25V, then charged at a constant voltage of 4.25V to a cutoff current of 0.05C, allowed to stand for 5 minutes, and then discharged at a constant current rate of 0.33C to a termination voltage of 2.8V, obtaining the initial discharge capacity C0. After standing for 5 minutes, the secondary battery was charged at a constant current rate of 0.33C to 4.25V, then charged at a constant voltage of 4.25V to a cutoff current of 0.05C, allowed to stand for 5 minutes, and discharged at a rate of 1C to 2.8V, obtaining the discharge capacity at a rate of 1C as C1; then charged at a constant current rate of 0.33C to 4.25V and then charged at a constant voltage of 0.05C, allowed to stand for 5 minutes, and discharged at a rate of 2C to 2.8V, obtaining the discharge capacity at a rate of 2C as C2.

[0228] 1C capacity retention rate = C1 / C0×100%

[0229] 2C capacity retention rate = C2 / C0×100%

[0230] The larger the values ​​of 1C capacity retention rate and 2C capacity retention rate, the better the rate performance of the battery.

[0231] The test results are shown in Table 2.

[0232] Table 1

[0233]

[0234] Table 2

[0235]

[0236] From the test results in Table 1 and Table 2, it can be seen that the composite cathode material of the embodiment of the present application has a specific structure and composition, which can effectively reduce the DCR of the battery and improve the cycle performance, rate performance and storage performance of the battery.

[0237] In contrast, Comparative Example 1-2 uses elemental sulfur to coat the positive electrode active material, and its battery has a higher DCR, and its cycle performance, rate performance, and storage performance are far inferior to those of Example 1-19.

[0238] For several compounds given but not listed in the examples, since their chemical properties and reaction properties when participating in electrochemical reactions are similar to those of the compounds listed in the examples, they are all suitable for the technical solution of the present invention and are therefore not listed here one by one.

[0239] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and any embodiments having substantially the same structure and effect as the technical concept within the scope of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the present application, any other embodiments that can be conceived by those skilled in the art and that combine some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A composite cathode material comprising: Positive electrode active material, including nickel-cobalt-manganese ternary material and / or nickel-cobalt-aluminum ternary material; as well as a coating layer, coating at least a portion of the surface of the positive electrode active material, wherein the coating layer comprises a composite material, The composite material includes particles containing a simple substance M and a lithium ion conductor material attached to the surface of the particles containing the simple substance M, wherein M includes at least one of S, Se, and Te.

2. The composite cathode material according to claim 1, wherein The lithium ion conductor material includes an ion conductivity of 1×10 -5 S / cm or above lithium ion conductor materials.

3. The composite cathode material according to claim 2, wherein The lithium ion conductor material includes a lithium ion conductor material having an ion conductivity of 0.001 S / cm-1 S / cm.

4. The composite cathode material according to claim 1, wherein The lithium ion conductor material includes at least one of lithium zinc germanate, lithium aluminum titanium phosphate, lithium aluminum germanium phosphate, lithium lanthanum titanate, glassy lithium conductive electrolyte powder, and garnet structure lithium conductive electrolyte powder.

5. The composite cathode material according to claim 4, wherein The lithium ion conductor material includes at least one of lithium aluminum titanium phosphate and lithium aluminum germanium phosphate.

6. The composite cathode material according to any one of claims 1 to 5, wherein The volume distribution particle size Dv50 of the particles containing the M element is ≤ 2 μm; and / or The volume distribution particle size Dv50 of the lithium ion conductor material is ≤100 nm; and / or The volume distribution particle size Dv50 of the positive electrode active material is 5 μm-15 μm; and / or The volume distribution particle size Dv50 of the composite positive electrode material is 8 μm-20 μm.

7. The composite cathode material according to claim 6, wherein The volume distribution particle size Dv50 of the particles containing the M element is 0.3 μm-1 μm; and / or The volume distribution particle size Dv50 of the lithium ion conductor material is 20nm-50nm.

8. The composite cathode material according to claim 1, wherein Based on the total mass of the composite positive electrode material, The mass percentage of the positive electrode active material is 80%-98%; and / or The mass percentage of the particles containing M element is 0.02%-5%; and / or The mass percentage of the lithium ion conductor material is 0.01%-1%.

9. The composite cathode material according to claim 8, wherein Based on the total mass of the composite positive electrode material, The mass percentage of the positive electrode active material is 90%-95%; and / or The mass percentage of the particles containing M element is 0.05%-2%; and / or The mass percentage of the lithium ion conductor material is 0.05%-1%.

10. The composite cathode material according to claim 1, wherein The composite material is attached to the surface of the positive electrode active material through a binder, thereby forming the coating layer.

11. The composite cathode material according to claim 10, wherein The lithium ion conductor material is attached to the surface of the particles containing the M element through the binder.

12. The composite cathode material according to claim 10 or 11, wherein The adhesive includes a castor oil-based UV oligomer adhesive.

13. The composite cathode material according to claim 12, wherein: The castor oil-based UV oligomer adhesive includes a castor oil-based UV oligomer with a molecular weight of 200Da-800Da.

14. The composite cathode material according to claim 1, wherein In the nickel-cobalt-manganese ternary material, the molar content of Ni element in the transition metal elements is greater than or equal to 0.

6.

15. The composite cathode material according to claim 1, wherein In the nickel-cobalt-aluminum ternary material, the molar content of Ni element in the transition metal elements is greater than or equal to 0.

6.

16. A method for preparing a composite cathode material, comprising: Preparing a composite material, comprising mixing particles containing a simple substance M with a lithium ion conductor material, and allowing the lithium ion conductor material to adhere to the surface of the particles containing the simple substance M to obtain a composite material, wherein M comprises at least one of S, Se, and Te; The preparation of the composite positive electrode material includes uniformly mixing the composite material with the positive electrode active material, and coating the composite material on at least a portion of the surface of the positive electrode active material to obtain the composite positive electrode material, wherein the positive electrode active material includes a nickel-cobalt-manganese ternary material and / or a nickel-cobalt-aluminum ternary material.

17. The method according to claim 16, wherein The preparation of the composite material comprises: mixing the particles containing the M element, the lithium ion conductor material and the castor oil-based UV oligomer binder and ball milling them to obtain a slurry containing the composite material; The preparation of the composite positive electrode material includes: uniformly mixing the slurry and the positive electrode active material, and then curing the castor oil-based UV oligomer binder so that the composite material is coated on at least a portion of the surface of the positive electrode active material to obtain the composite positive electrode material.

18. The method according to claim 17, wherein The mass ratio of the particles containing M element to the lithium ion conductor material is 1:0.3-1:0.6; and / or The mass ratio of the particles containing M element to the castor oil-based UV oligomer adhesive is 1:0.1-1:0.

3.

19. A positive electrode sheet comprising a positive electrode current collector and a positive electrode film layer located on at least one side of the positive electrode current collector, wherein the positive electrode film layer comprises the composite positive electrode material according to any one of claims 1 to 15, or the composite positive electrode material prepared by the method according to any one of claims 16 to 18.

20. A battery comprising the positive electrode sheet according to claim 19.

21. An electrical device comprising the battery according to claim 20.

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