Composite material and preparation method thereof, positive pole piece, secondary battery and electric device

Abstract

The invention discloses a composite material and a preparation method thereof, a positive pole piece, a secondary battery and an electric device, and belongs to the technical field of batteries. The composite material comprises a lithium-containing compound, a catalyst and a conductive agent, and the lithium-containing compound comprises a lithium element, a carbon element and an oxygen element; the catalyst comprises one or more of transition metal oxides, transition metal carbides, transition metal nitrides or transition metal phosphides; and the average particle diameter D1 of the lithium-containing compound is smaller than or equal to 200nm. According to the technical scheme, the capacity of the battery can be improved.

Description

Technical Field

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

[0002] With the increasing severity of environmental pollution, the new energy industry has attracted more and more attention. In the new energy industry, battery technology is an important factor in its development.

[0003] The development of battery technology requires consideration of numerous design factors, such as capacity, energy density, cycle life, and reliability. During the initial charge and discharge of a battery cell, a solid electrolyte interface (SEI) film forms on the surface of the negative electrode. This SEI film consumes a significant amount of lithium ions, impacting the battery's capacity. Therefore, developing a composite material that can replenish lithium ions and thereby increase battery capacity is a pressing technical challenge. Summary of the Invention

[0004] The present application is made in view of the above-mentioned problems, and its purpose is to provide a composite material to improve the capacity of a battery.

[0005] In order to achieve the above-mentioned objectives, the present application provides a composite material and a preparation method thereof, a positive electrode sheet, a secondary battery and an electrical device.

[0006] In a first aspect, a composite material is provided, comprising: a lithium-containing compound, a catalyst and a conductive agent, wherein the lithium-containing compound comprises lithium, carbon and oxygen; the catalyst comprises one or more of a transition metal oxide, a transition metal carbide, a transition metal nitride or a transition metal phosphide; and the average particle size D1 of the lithium-containing compound satisfies: D1 ≤ 200 nm.

[0007] In the embodiment of the present application, the lithium-containing compound can decompose to produce lithium ions, thereby replenishing lithium ions to the battery; the catalyst can catalyze the decomposition of the lithium-containing compound, so that the lithium-containing compound can decompose more easily, thereby providing more lithium ions to the battery. The average particle size D1 of the lithium-containing compound satisfies: D1 ≤ 200nm. This is beneficial to increase the contact area between the electrolyte and the lithium-containing compound, and thus is beneficial to the transmission and diffusion of lithium ions. The composite material has a good lithium replenishment effect and can increase the capacity of the battery; it is also beneficial to the contact between the conductive agent and the catalyst and the lithium-containing compound, which is beneficial to catalyze the decomposition of the lithium-containing compound, improve the conductive properties of the composite material, and thus can increase the capacity of the battery. Therefore, the technical solution of the embodiment of the present application can increase the capacity of the battery.

[0008] In one possible implementation, 20 nm ≤ D1 ≤ 200 nm. When the average particle size of the lithium-containing compound is greater than or equal to 20 nm, the preparation of the lithium-containing compound is facilitated, thereby reducing the complexity of the preparation. When the average particle size of the lithium-containing compound is less than or equal to 200 nm, the battery capacity is increased.

[0009] In a possible implementation, 50 nm ≤ D1 ≤ 150 nm. In this way, the lithium-containing compound has a more suitable average particle size, and the battery has a higher capacity.

[0010] In one possible implementation, the composite material further comprises a sodium-containing compound, wherein the sodium-containing compound comprises elemental sodium. During the preparation of the composite material, a sodium source is added to facilitate the preparation of lithium-containing compound primary particles with a smaller average particle size, and thus the prepared composite material further comprises elemental sodium.

[0011] In one possible implementation, in the composite material, the ratio W of the molar content of the sodium element to the molar content of the lithium element satisfies the following: 0.005 ≤ W ≤ 0.12. Thus, in the composite material, the sodium element has an appropriate molar content, which facilitates obtaining a lithium-containing compound with a relatively suitable particle size; and the lithium element also has an appropriate molar content, which facilitates obtaining a battery with a higher capacity.

[0012] In a possible implementation, 0.025≤W≤0.05. This is beneficial for obtaining a lithium-containing compound with a more appropriate particle size, thereby improving the capacity of the battery.

[0013] In one possible implementation, the chemical formula of the lithium-containing compound is Li2C x O y , where 1≤x≤4, 3≤y≤6. Lithium-containing compounds that satisfy the above chemical formula can decompose into lithium ions and gases (e.g., carbon monoxide and carbon dioxide) under the action of voltage and catalyst. The lithium ions produced by decomposition can replenish lithium ions, thereby increasing the battery capacity. The gases produced by decomposition will not remain in the positive electrode sheet, and the decomposition residue will not affect the long-term reliability and other performance of the battery cell.

[0014] In one possible implementation, the lithium-containing compound includes one or more of Li2C2O4, Li2CO3, Li2C4O4, Li2C3O5, or Li2C4O6. Under the action of voltage and catalyst, the above-mentioned lithium-containing compound can decompose into lithium ions and gases (such as carbon monoxide and carbon dioxide). The lithium ions produced by decomposition can replenish lithium ions, which is beneficial for improving the capacity of the battery. The gas produced by decomposition will not remain in the positive electrode sheet, and the long-term reliability and other performance of the battery cell will not be affected by the residue produced by decomposition. In addition, the above-mentioned lithium-containing compound has good stability, can exist stably in air and organic solvents, and is compatible with the coating process of the positive electrode slurry.

[0015] In a possible implementation, the composite material has a morphology of secondary particles. The lithium-containing compound, the conductive agent, and the catalyst are mixed together to form a composite material having a morphology of secondary particles.

[0016] In one possible implementation, the morphology of the lithium-containing compound is primary particles. On the one hand, this is conducive to full contact between the lithium-containing compound and the catalyst to achieve a better catalytic effect, thereby helping to reduce the decomposition voltage of the lithium-containing compound and increase the capacity of the battery; on the other hand, the conductive agent is dispersed around the lithium-containing compound of the primary particles, which is conducive to improving the electronic conductivity of the lithium-containing compound, thereby helping to improve the capacity of the battery.

[0017] In a possible implementation, the volume average particle size Dv50 of the composite material satisfies: 2 μm≤Dv50≤10 μm.

[0018] When the volume average particle size Dv50 of the composite material is not less than 2 μm, the risk of agglomeration of the composite material and the difficulty of preparing the composite material can be reduced; when the volume average particle size Dv50 of the composite material does not exceed 10 μm, the composite material has a suitable particle size, and the released lithium ions in the lithium-containing compound have a suitable diffusion distance, which is conducive to a higher transmission rate of lithium ions and allows more lithium ions to be released, thereby helping to improve the capacity of the battery.

[0019] In a possible implementation, 4 μm ≤ Dv50 ≤ 8 μm. In this way, the battery can have a higher capacity.

[0020] In a possible implementation, based on the total mass of the composite material, the mass content A of the conductive agent satisfies: 1 wt%≤A≤40 wt%.

[0021] When the mass content A of the conductive agent is not less than 1wt%, the composite material has higher conductivity and lower resistivity; when the mass content A of the conductive agent does not exceed 40wt%, the conductive agent has a suitable mass proportion, the catalyst and the lithium-containing compound also have a suitable mass proportion, and the battery cell has a suitable capacity.

[0022] In a possible implementation, 2 wt% ≤ A ≤ 20 wt%. In this way, the conductive agent has a more appropriate mass ratio, and the battery has a higher capacity.

[0023] In a possible implementation, based on the total mass of the composite material, the mass content B of the catalyst satisfies: 0.5 wt%≤B≤20 wt%.

[0024] When the mass content B of the catalyst is not less than 0.5wt%, the contact area between the catalyst and the lithium-containing compound is appropriate, and the catalyst has a good catalytic effect, which is beneficial to the catalytic decomposition of the lithium-containing compound and the improvement of the battery capacity; when the mass content B of the catalyst does not exceed 20wt%, it is beneficial to add more lithium-containing compounds to the composite material, which is beneficial to improve the battery capacity.

[0025] In a possible implementation, 1 wt% ≤ B ≤ 10 wt%. In this way, the catalyst has a more appropriate mass ratio and the battery has a higher capacity.

[0026] In one possible implementation, the chemical formula of the transition metal oxide is M α O β , wherein 0<α≤3, 0<β≤5, M includes one or more of Ni, Co, Fe, Mn, V, Cr, Cu or Ti; optionally, M α O β The catalyst comprises one or more of NiO, Co3O4, Fe2O3, MoO3 or V2O5. The catalyst can reduce the decomposition voltage of the lithium-containing compound, so that the lithium-containing compound decomposes at a lower voltage.

[0027] In one possible implementation, the transition metal carbide includes one or more of molybdenum carbide, vanadium carbide, tungsten carbide, titanium carbide, cobalt carbide, iron carbide, or nickel carbide; and / or the transition metal nitride includes one or more of molybdenum nitride, vanadium nitride, titanium nitride, manganese nitride, cobalt nitride, iron nitride, or nickel nitride; and / or the transition metal phosphide includes one or more of nickel phosphide, cobalt phosphide, manganese phosphide, tungsten phosphide, or molybdenum phosphide. These transition metal carbides, nitrides, and phosphides have good catalytic effects and can catalyze the decomposition of lithium-containing compounds.

[0028] In one possible implementation, the conductive agent includes a carbon material; alternatively, the conductive agent includes a carbon-based conductive agent; alternatively, the carbon-based conductive agent includes one or more of carbon nanotubes, carbon fibers, acetylene black, Ketjen black, conductive carbon black, C60, or graphene. Carbon materials have good electrical conductivity and are well compatible with other materials in the battery. Including carbon materials in the composite material helps reduce the resistivity of the composite material, improve the conductivity of the composite material, and increase the battery capacity.

[0029] In one possible implementation, the powder resistivity R of the composite material at 20 MPa satisfies: R≤360Ω·cm. Thus, the powder resistivity of the composite material is low, which is beneficial for improving the conductivity of the composite material, thereby facilitating an increase in the capacity of the battery.

[0030] In one possible implementation, R is ≤ 1Ω·cm. This is beneficial for further improving the conductivity of the composite material and providing a higher capacity for the battery.

[0031] A second aspect provides a method for preparing a composite material, comprising: adding a lithium source, a catalyst, a conductive agent, and a sodium source to a solvent to obtain a slurry, wherein the catalyst comprises one or more of a transition metal oxide, a transition metal carbide, a transition metal nitride, or a transition metal phosphide; and drying the slurry to obtain the composite material. The composite material prepared by this method has a lithium-containing compound with a smaller primary particle size, which is beneficial for increasing battery capacity.

[0032] In one possible implementation, drying the slurry to obtain the composite material includes drying the slurry by spray drying to obtain the composite material. Spray drying facilitates the preparation of a lithium-containing compound with a smaller particle size and facilitates the preparation of the composite material.

[0033] In one possible implementation, the drying temperature T satisfies the following conditions: 150°C ≤ T ≤ 250°C; alternatively, 175°C ≤ T ≤ 225°C. The drying temperature affects the growth and nucleation process of the secondary particles of the composite material. Selecting a temperature within the above range facilitates obtaining secondary particles of the composite material of an appropriate particle size.

[0034] In one possible implementation, based on the combined mass of the lithium source, the catalyst, the conductive agent, and the sodium source, the mass content C of the sodium source satisfies the following range: 0.001 wt% ≤ C ≤ 0.25 wt%; alternatively, 0.02 wt% ≤ C ≤ 0.1 wt%. Selecting a mass content of the sodium source within this range facilitates obtaining primary particles of the lithium-containing compound having a suitable particle size.

[0035] In one possible implementation, the lithium source includes one or more of Li2C2O4, Li2CO3, Li2C4O4, Li2C3O5, Li2C4O6, or LiOH. The lithium source can be dissolved in a solvent and can provide lithium ions, thereby obtaining a slurry containing lithium ions, thereby facilitating the preparation of a composite material from the slurry.

[0036] In one possible implementation, the sodium source includes one or more of NaOH, Na2CO3, NaCl, NaNO3, Na2SO4, NaHSO4, NaHCO3, Na2C2O4, Na2C4O4, Na2C3O5, and Na2C4O6. The sodium source can be dissolved in a solvent. During the drying process, the sodium source can be precipitated before the lithium source, thereby providing nucleation sites for the growth of the lithium-containing compound, facilitating the formation of the lithium-containing compound and obtaining a lithium-containing compound with a smaller particle size.

[0037] In a third aspect, a positive electrode plate is provided, comprising a positive electrode active material; a composite material according to the first aspect and any possible implementation thereof, and / or a composite material prepared by the method according to the second aspect and any possible implementation thereof.

[0038] In a fourth aspect, a secondary battery is provided, comprising the positive electrode sheet according to the third aspect and any possible implementation thereof.

[0039] In a possible implementation, the secondary battery is a secondary battery before formation.

[0040] In a fifth aspect, an electrical device is provided, comprising the secondary battery described in the fourth aspect. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments of the present application. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the drawings without creative work.

[0042] Figure 1 A schematic diagram of a method for preparing a composite material according to an embodiment of the present application;

[0043] Figure 2 A schematic diagram of a battery cell according to an embodiment of the present application;

[0044] Figure 3 A schematic diagram of a battery according to an embodiment of the present application;

[0045] Figure 4A schematic diagram of an electrical device according to an embodiment of the present application;

[0046] Figure 5 This is a SEM diagram of a composite material according to an embodiment of the present application;

[0047] Figure 6 A partially enlarged SEM diagram of a composite material according to an embodiment of the present application;

[0048] Figure 7 A schematic SEM diagram of a pair of composite materials of this application;

[0049] Figure 8 This is a schematic SEM diagram of a pair of composite materials used in this application. DETAILED DESCRIPTION

[0050] The embodiments of the composite material and its preparation method, positive electrode sheet, secondary battery, and electric device of the present application are specifically disclosed in detail with appropriate reference to the accompanying drawings. 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.

[0051] " 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.

[0052] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0053] 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.

[0054] 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.

[0055] The development of battery technology needs to consider many design factors, such as capacity, energy density, cycle life, reliability, etc. During the first charge and discharge process of the battery cell, a solid electrolyte interface SEI film will be produced on the surface of the negative electrode. The presence of the SEI film will consume a large amount of lithium ions, affecting the capacity of the battery. In order to increase the capacity of the battery, lithium-containing compounds with a high lithium content are added to the positive electrode slurry. For example, lithium oxalate is added to provide more lithium ions to the battery cell. However, lithium-containing compounds such as lithium oxalate need to decompose at a higher potential, and lithium-containing compounds such as lithium oxalate have poor electrical conductivity, which has a poor effect on improving the capacity of the battery. Therefore, how to provide a material to increase the capacity of the battery is a technical problem that needs to be solved urgently.

[0056] In view of this, an embodiment of the present application provides a composite material, including a lithium-containing compound, a catalyst and a conductive agent. The average particle size of the lithium-containing compound is less than or equal to 200 nm, which can increase the contact area between the electrolyte and the lithium-containing compound, thereby facilitating the transmission and diffusion of lithium ions, and can increase the capacity of the battery; and it is also beneficial to the contact between the conductive agent and the catalyst and the lithium-containing compound, which is beneficial to catalyzing the decomposition of the lithium-containing compound, improving the conductive properties of the composite material, and thus increasing the capacity of the battery.

[0057] The composite material in the embodiments of the present application can be used as a lithium supplement, that is, it can replenish the lithium ions consumed by the negative electrode. As an example, the composite material can be mixed with a positive electrode active material (such as lithium iron phosphate, ternary materials, etc.) to prepare a positive electrode slurry for use.

[0058] The secondary battery in the embodiments of this application can refer to a battery cell or a battery pack. A battery cell can be the smallest unit of a battery pack. A battery cell includes a positive electrode sheet, a negative electrode sheet, a separator, an electrolyte, etc.

[0059] During the charging process of a lithium-ion secondary battery, lithium ions are released from the positive electrode active material, moved and embedded in the negative electrode material; while during the discharging process, lithium ions are released from the negative electrode material, moved and embedded in the positive electrode active material.

[0060] It should be understood that the "embedding" process described in this application refers to the process in which lithium ions are embedded in the positive electrode active material and the negative electrode material due to electrochemical reactions, and the "extraction" and "deintercalation" processes described in this application refer to the process in which lithium ions are extracted from the positive electrode active material and the negative electrode material due to electrochemical reactions.

[0061] [Composite Materials]

[0062] An embodiment of the present application provides a composite material, which includes a lithium-containing compound, a catalyst, and a conductive agent.

[0063] The lithium-containing compound includes lithium, carbon and oxygen. The lithium-containing compound may include an organic lithium-containing compound, such as lithium oxalate, or an inorganic lithium-containing compound, such as lithium carbonate.

[0064] The lithium-containing compound may refer to a compound including lithium, carbon, and oxygen, for example, lithium oxalate and lithium carbonate.

[0065] Lithium-containing compounds can decompose under the action of voltage, decomposing into lithium ions and carbon oxides (such as CO, CO2). The lithium ions produced by the decomposition can replenish lithium ions in the battery, thereby helping to increase the battery capacity.

[0066] The catalyst includes one or more of a transition metal oxide, a transition metal carbide, a transition metal nitride, or a transition metal phosphide. The catalyst can reduce the decomposition voltage of the lithium-containing compound.

[0067] Transition metal carbides, transition metal nitrides, and transition metal phosphides can be obtained by treating transition metal oxides. Transition metal carbides can be molybdenum carbide or tungsten carbide, and transition metal nitrides can be molybdenum nitride or manganese nitride. Transition metal phosphides can be nickel phosphide, cobalt phosphide, manganese phosphide, tungsten phosphide, or molybdenum phosphide.

[0068] Transition metal oxides, transition metal carbides, transition metal nitrides, and transition metal phosphides not only have high conductivity, but also have abundant surface active sites and high specific surface area, which can catalyze the decomposition of lithium-containing compounds.

[0069] Transition metal oxides, transition metal carbides, transition metal nitrides, and transition metal phosphides can catalyze the decomposition of lithium-containing compounds under the action of voltage, that is, they can reduce the decomposition voltage of lithium-containing compounds.

[0070] As an example, the catalyst is a transition metal oxide, such as Ni x O, wherein 0.67≤x≤1, embodiments of the present application include but are not limited to this, as long as it can catalyze the decomposition of lithium-containing compounds.

[0071] The conductive agent is a material that can conduct electricity. For example, the conductive agent can be a carbon material.

[0072] In the composite material, the lithium-containing compound is in contact with the catalyst and the conductive agent. In this way, the catalyst can catalyze the decomposition of the lithium-containing compound, and the conductive agent is conducive to the transmission of electrons, thereby facilitating the reduction of the decomposition voltage of the composite material and the utilization of the capacity of the composite material.

[0073] The average particle size D1 of the lithium-containing compound satisfies: D1≤200 nm. D1 can be 20 nm, 50 nm, 60 nm, 80 nm, 100 nm, 120 nm, 160 nm, 200 nm, or any value within the aforementioned range.

[0074] When the average particle size of the lithium-containing compound is less than or equal to 200 nm, the lithium-containing compound has a smaller particle size, which can shorten the escape path of lithium ions and increase the contact area between the electrolyte and the lithium-containing compound, thereby facilitating the transmission and diffusion of lithium ions during the charging process. The composite material has a good lithium replenishment effect, thereby helping to increase the capacity of the battery. In addition, it is also beneficial for the catalyst to fully contact with the lithium-containing compound, which is beneficial for catalyzing the decomposition of the lithium-containing compound and reducing the decomposition voltage of the lithium-containing compound; it is also beneficial for the conductive agent to fully contact with the lithium-containing compound, which is beneficial for the transmission of electrons, thereby helping to increase the capacity of the battery.

[0075] As an example, the average particle size D1 is the average particle size of primary particles of the lithium-containing compound.

[0076] In the embodiment of the present application, the lithium-containing compound can decompose to produce lithium ions and gas, thereby replenishing lithium ions to the battery; the catalyst can catalyze the decomposition of the lithium-containing compound, so that the lithium-containing compound can decompose more easily, thereby providing more lithium ions to the battery. The average particle size D1 of the lithium-containing compound satisfies: D1 ≤ 200nm, which is beneficial to increase the contact area between the electrolyte and the lithium-containing compound, thereby facilitating the transmission and diffusion of lithium ions, and thus increasing the capacity of the battery; it is also beneficial to the contact between the conductive agent and the catalyst and the lithium-containing compound, which is beneficial to catalyzing the decomposition of the lithium-containing compound, improving the conductivity of the composite material, and thus increasing the capacity of the battery. Therefore, the technical solution of the embodiment of the present application can increase the capacity of the battery.

[0077] In some embodiments, the average particle size D1 of the lithium-containing compound satisfies: 20 nm ≤ D1 ≤ 200 nm.

[0078] When the average particle size of the lithium-containing compound is greater than or equal to 20 nm, the preparation of the lithium-containing compound is facilitated, which helps reduce the complexity of the preparation; when the average particle size of the lithium-containing compound is less than or equal to 200 nm, it helps to increase the capacity of the battery.

[0079] In some embodiments, the average particle size D1 of the lithium-containing compound satisfies: 50 nm ≤ D1 ≤ 150 nm.

[0080] D1 can be 50 nm, 60 nm, 70 nm, 75 nm, 80 nm, 90 nm, 115 nm, 125 nm, 135 nm, 145 nm, 150 nm, or any value within the above range.

[0081] When D1 is within the range of 50 nm to 150 nm, the lithium-containing compound has a more suitable primary particle size, which is beneficial to the preparation of the lithium-containing compound and allows the battery to have a higher capacity.

[0082] In some embodiments, the composite material further comprises a sodium-containing compound, which comprises sodium, carbon, and oxygen. During the preparation of the composite material, a sodium source is added to facilitate the preparation of lithium-containing compound primary particles with a smaller average particle size, thereby further comprising the sodium-containing compound in the prepared composite material.

[0083] As an example, sodium can be detected in the composite material.

[0084] As another example, the content of sodium-containing compounds in the composite material is very small, and it is difficult to detect the presence of a new phase (such as sodium oxalate), and only the presence of sodium element can be detected.

[0085] As an example, the sodium-containing compound may have a similar chemical formula to the lithium-containing compound. For example, the chemical formula of the sodium-containing compound is Na2Cx O y , 1≤x≤4, 3≤y≤6.

[0086] In the above embodiment, a small amount of sodium ions may be generated after the composite material is decomposed, and the small amount of sodium ions may be dissolved in the electrolyte.

[0087] In some embodiments, in the composite material, the ratio W of the molar content of the sodium element to the molar content of the lithium element satisfies the following: 0.005 ≤ W ≤ 0.12. For example, W can be 0.005, 0.006, 0.01, 0.02, 0.025, 0.03, 0.04, 0.05, 0.06, 0.08, 0.09, 0.1, 0.12, or any value within the foregoing ranges.

[0088] As an example, in order to conveniently express the molar ratio of sodium element and lithium element, the sodium-containing compound and the lithium-containing compound can be expressed as Li b Na a C2O4, where 1≤x≤4, 3≤y≤6, a+b=2, and 0.01≤a≤0.2. For example, a is 0.01, b is 1.99; a is 0.2, b is 1.8; a is 0.05, b is 1.95.

[0089] When W is greater than or equal to 0.005, during the preparation of the composite material, a certain content of sodium element can inhibit the growth of primary particles of the lithium-containing compound, which is conducive to obtaining primary particles with smaller particle size; when W is less than or equal to 0.12, the risk of reducing the lithium content in the lithium-containing compound due to excessive sodium element can be reduced, thereby reducing the risk of less increase in battery capacity due to reduced lithium content.

[0090] The sodium element has a suitable molar content, which is conducive to obtaining a lithium-containing compound with a relatively suitable particle size; and the lithium element has a suitable molar content, which is conducive to obtaining a battery with a higher capacity.

[0091] In some embodiments, 0.025≤W≤0.05. In this way, the sodium element has a more appropriate content, which is conducive to obtaining a lithium-containing compound with smaller particle size and a battery with higher capacity.

[0092] In some embodiments, the lithium-containing compound has the formula Li2C x O y , where 1≤x≤4, 3≤y≤6.

[0093] x and y satisfy the following relationship: x + y = 2n, 2 ≤ n ≤ 5. x can be 1, 2, 3, 4, or any value within the aforementioned range; y can be 3, 4, 5, 6, or any value within the aforementioned range; and n can be 2, 3, 4, 5, or any value within the aforementioned range. As an example, x, y, and n are all positive integers.

[0094] Lithium-containing compounds that satisfy the above chemical formula can be decomposed into lithium ions and gases (such as carbon monoxide and carbon dioxide) under the action of voltage and catalyst. The lithium ions produced by decomposition can replenish lithium ions, which is beneficial to improving the capacity of the battery; the gas produced by decomposition will not remain in the positive electrode sheet, and the long-term reliability and other performance of the battery cell will not be affected by the residues produced by decomposition.

[0095] In some embodiments, the lithium-containing compound includes one or more of Li2C2O4, Li2CO3, Li2C4O4, Li2C3O5, or Li2C4O6.

[0096] Under the influence of voltage and catalysts, these lithium-containing compounds can decompose into lithium ions and gases (such as carbon monoxide and carbon dioxide). The lithium ions produced by decomposition can replenish lithium ions, which helps increase the battery's capacity. The decomposed gases will not remain in the positive electrode sheet, and the decomposition residue will not affect the long-term reliability and other performance of the battery cell. In addition, these lithium-containing compounds have good stability and can exist stably in air and organic solvents, making them compatible with the coating process of the positive electrode slurry.

[0097] As an example, the gas generated by the decomposition of the lithium-containing compound can be sucked out of the battery cell through a tool such as a suction nozzle during the formation step.

[0098] In some embodiments, the composite material has a secondary particle morphology. The lithium-containing compound, the conductive agent, and the catalyst are mixed together to form a composite material having a secondary particle morphology.

[0099] The primary particles of the lithium-containing compound, the conductive agent and the catalyst are mixed to form a spherical or nearly spherical composite material. In this way, after the lithium-containing compound decomposes, the conductive agent and the catalyst in the composite material can retain the three-dimensional structure of the composite material, and the holes or vacancies formed at the original position of the lithium-containing compound will not be directly reflected on the positive electrode sheet. Therefore, the risk of the conductive network of the positive electrode sheet being destroyed is reduced, and the impact on the transmission of electrons and ions in the positive electrode sheet is small, thereby increasing the capacity of the battery. In addition, after the lithium-containing compound decomposes, vacancies or holes are left in the composite material. The vacancies can enhance the infiltration of the electrolyte, and the electrolyte on the vacancies can provide channels for ion transmission, which is beneficial to the transmission of ions (such as lithium ions), thereby increasing the capacity of the battery.

[0100] In some embodiments, the lithium-containing compound has the morphology of primary particles.

[0101] Primary particles may refer to unagglomerated particles, and secondary particles may refer to particles formed by agglomeration of primary particles.

[0102] In the embodiment of the present application, the primary particles of the lithium-containing compound have a rod-like or rod-like morphology, and the secondary particles of the composite material have a spherical or nearly spherical morphology.

[0103] In the secondary particles of the composite material, the lithium-containing compound has the morphology of primary particles, or in other words, the majority of the lithium-containing compound particles are unagglomerated. This, on the one hand, facilitates full contact between the lithium-containing compound and the catalyst, achieving a better catalytic effect, thereby lowering the decomposition voltage of the lithium-containing compound and increasing the battery capacity. On the other hand, the conductive agent dispersed around the lithium-containing compound in the primary particles helps to improve the electronic conductivity of the lithium-containing compound, thereby increasing the battery capacity.

[0104] In some embodiments, the volume average particle size Dv50 of the composite material satisfies: 2 μm≤Dv50≤10 μm.

[0105] Dv50 can refer to the particle size corresponding to when the cumulative particle size volume distribution number of a sample reaches 50%, or it can refer to the particle size smaller than it accounting for 50%.

[0106] Dv50 can be 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, or any value within the above range.

[0107] The volume average particle size of the composite material may refer to the volume average particle size of the composite material powder or composite material particles.

[0108] When the volume average particle size Dv50 of the composite material is not less than 2 μm, the risk of agglomeration of the composite material and the difficulty of preparing the composite material can be reduced; when the volume average particle size Dv50 of the composite material does not exceed 10 μm, the composite material has a suitable particle size, and the released lithium ions in the lithium-containing compound have a suitable diffusion distance, which is conducive to a higher transmission rate of lithium ions and allows more lithium ions to be released, thereby helping to improve the capacity of the battery.

[0109] In some embodiments, 4 μm ≤ Dv50 ≤ 8 μm. In this way, the composite material has a relatively suitable particle size, which is conducive to making the battery have a higher capacity.

[0110] In some embodiments, based on the total mass of the composite material, the mass content A of the conductive agent satisfies: 1 wt %≤A≤40 wt %.

[0111] A can be 1 wt%, 5 wt%, 10 wt%, 15 wt%, 25 wt%, 30 wt%, 35 wt%, 40 wt% or any value within the above range.

[0112] When the mass content A of the conductive agent is not less than 1wt%, the composite material has higher conductivity and lower resistivity; when the mass content A of the conductive agent does not exceed 40wt%, the conductive agent has a suitable mass proportion, the catalyst and the lithium-containing compound also have a suitable mass proportion, and the battery cell has a suitable capacity.

[0113] In some embodiments, 2 wt % ≤ A ≤ 20 wt %. In this way, the conductive agent has a more appropriate weight ratio and the battery has a higher capacity.

[0114] In some embodiments, based on the total mass of the composite material, the mass content B of the catalyst satisfies: 0.5 wt % ≤ B ≤ 20 wt %.

[0115] B can be 0.5 wt%, 1 wt%, 5 wt%, 8 wt%, 10 wt%, 15 wt%, 20 wt% or any value within the above range.

[0116] When the mass content B of the catalyst is not less than 0.5wt%, the contact area between the catalyst and the lithium-containing compound is appropriate, and the catalyst has a good catalytic effect, which is beneficial to the catalytic decomposition of the lithium-containing compound and the improvement of the battery capacity; when the mass content B of the catalyst does not exceed 20wt%, it is beneficial to add more lithium-containing compounds to the composite material, which is beneficial to improve the battery capacity.

[0117] In some embodiments, 1 wt% ≤ B ≤ 10 wt%. In this way, the catalyst has a more appropriate mass ratio and the battery has a higher capacity.

[0118] In some embodiments, the transition metal oxide has the formula M α O β , wherein 0<α≤3, 0<β≤5, and M includes one or more of Ni, Co, Fe, Mn, V, Cr, Cu or Ti.

[0119] α can be 0.5, 1, 2, 3 or any value within the above range, and β can be 0.5, 1, 2, 3, 4, 5 or any value within the above range. In some examples, α and β are positive integers.

[0120] The catalyst can reduce the decomposition voltage of the lithium-containing compound, so that the lithium-containing compound can be decomposed at a lower voltage.

[0121] In some embodiments, M α O βIncluding: one or more of NiO, Co3O4, Fe2O3, MoO3 or V2O5.

[0122] The catalyst can reduce the decomposition voltage of the lithium-containing compound, so that the lithium-containing compound can be decomposed at a lower voltage.

[0123] In some embodiments, the transition metal carbide includes one or more of molybdenum carbide, vanadium carbide, tungsten carbide, titanium carbide, cobalt carbide, iron carbide, or nickel carbide; and / or the transition metal nitride includes one or more of molybdenum nitride, vanadium nitride, titanium nitride, manganese nitride, cobalt nitride, iron nitride, or nickel nitride; and / or the transition metal phosphide includes one or more of nickel phosphide, cobalt phosphide, manganese phosphide, tungsten phosphide, or molybdenum phosphide. The above transition metal carbides, transition metal nitrides, and transition metal phosphides have good catalytic effects and can catalyze the decomposition of lithium-containing compounds.

[0124] In some embodiments, the conductive agent includes a carbon material.

[0125] Optionally, the conductive agent includes a carbon-based conductive agent. For example, the conductive agent includes a carbon-based material. For example, the conductive agent can be conductive graphite, conductive carbon black, graphene, etc.

[0126] Optionally, the carbon-based conductive agent includes one or more of carbon nanotubes, carbon fibers, acetylene black, Ketjen black, conductive carbon black, C60 or graphene.

[0127] Carbon materials have good electrical conductivity and are well compatible with other materials in the battery. Including carbon materials in composite materials is beneficial to reducing the resistivity of the composite materials, improving the electrical conductivity of the composite materials, and increasing the capacity of the battery.

[0128] In some embodiments, in the composite material, the lithium-containing compound and the conductive agent are chemically bonded, and the lithium-containing compound and the catalyst are chemically bonded. For example, during the preparation of the composite material, the lithium-containing compound is grown in situ on the conductive agent and the catalyst. Thus, compared to physically mixing the lithium-containing compound with the conductive agent and the catalyst, this in situ growth method is beneficial for enhancing the bonding strength between the lithium-containing compound, the conductive agent, and the catalyst, ultimately improving the conductivity of the composite material, reducing the decomposition voltage of the composite material, and improving the lithium replenishment effect of the composite material and the capacity of the battery.

[0129] In some embodiments, the powder resistivity R of the composite material at 20 MPa satisfies: R≤360Ω·cm. Thus, the powder resistivity of the composite material is low, which is beneficial to improving the conductivity of the composite material, thereby facilitating improving the capacity of the battery.

[0130] R may be 360 ​​Ω·cm, 350 Ω·cm, 200 Ω·cm, 100 Ω·cm, 50 Ω·cm, 10 Ω·cm, 1 Ω·cm, 0.5 Ω·cm, or any value within the above range.

[0131] In some embodiments, R≤1Ω·cm. This is beneficial to further improve the conductivity of the composite material and the battery has a higher capacity.

[0132] [Method for preparing composite materials]

[0133] Figure 1 This is a schematic diagram of a method for preparing a composite material according to an embodiment of the present application. This method can be used to prepare the composite material according to any of the above embodiments. Figure 1 As shown, the method 100 includes the following steps.

[0134] In step 110 , a lithium source, a catalyst, a conductive agent, and a sodium source are added to a solvent to obtain a slurry.

[0135] The lithium source may be the lithium-containing compound in the above embodiment, or lithium hydroxide, as long as it can be dissolved in the solvent and provide lithium ions.

[0136] The solvent may be deionized water. As an example, the lithium-containing compound is dissolved in deionized water, and then a conductive agent, a catalyst, and a sodium source are added, and stirred to obtain a uniform slurry.

[0137] The sodium source is a substance containing the element sodium. For example, the sodium source is a sodium salt, such as a salt formed by combining sodium ions and acid radical ions. For example, Na2CO3. Another example is the sodium-containing compound mentioned in the above embodiments.

[0138] The lithium source and the sodium source are dissolved in the solvent, and the conductive agent and the catalyst are insoluble in the solvent.

[0139] The catalyst may be the catalyst mentioned in the above embodiment, and the catalyst includes one or more of transition metal oxides, transition metal carbides, transition metal nitrides or transition metal phosphides.

[0140] Step 120: drying the slurry to obtain a composite material.

[0141] During the drying process, sodium-containing compounds including sodium elements will preferentially crystallize and nucleate around the conductive agent and the catalyst. However, due to the low content of the sodium source, the crystallized and nucleated sodium-containing compounds are difficult or unable to grow quickly. Due to the high content of the lithium source, the lithium-containing compounds will encounter the already nucleated sodium source during the crystallization and nucleation process, and thus the lithium-containing compounds will find it difficult to grow further, thereby obtaining primary particles of lithium-containing compounds with smaller particle sizes.

[0142] The drying process may be a process step performed at a certain temperature, that is, drying may be performed while heating, for example, at a temperature of 150°C to 250°C.

[0143] The description of the lithium-containing compound, catalyst, and conductive agent can be found in the description of the composite material embodiment, and will not be repeated here.

[0144] In the embodiment of the present application, the composite material prepared by the method 100 has good performance, which is beneficial to improving the capacity of the battery body; and the method is simple to operate and facilitates the preparation of the composite material.

[0145] In some embodiments, drying the slurry to obtain the composite material includes drying the slurry by spray drying to obtain the composite material. Spray drying facilitates the preparation of a lithium-containing compound with a smaller particle size and facilitates the preparation of the composite material.

[0146] As an example, a corresponding device is used for spray drying. For example, the slurry is fed into the device through a feed port at a certain feed rate, and the temperature of the device is set to perform a drying process, thereby spray drying the slurry.

[0147] In some embodiments, the drying temperature T satisfies: 150°C≤T≤250°C.

[0148] During the treatment process using the spray drying device, hot air of a certain temperature is set at the outlet of the device to dry the slurry. The drying temperature of this embodiment can be the temperature of the hot air.

[0149] T may be 150°C, 200°C, 250°C, or any value within the above range.

[0150] The drying temperature affects the growth and nucleation of the composite's secondary particles. Selecting a temperature within the above range facilitates obtaining composite secondary particles of an appropriate particle size. Higher drying temperatures lead to faster growth of the secondary particles and larger particle sizes.

[0151] Optionally, 175° C. ≤ T ≤ 225° C. By selecting the drying temperature within the above range, secondary particles of the composite material with a more appropriate particle size can be obtained.

[0152] In some embodiments, based on the sum of the mass of the lithium source, the catalyst, the conductive agent, and the sodium source, the mass content C of the sodium source satisfies: 0.001 wt%≤C≤0.25 wt%; alternatively, 0.02 wt%≤C≤0.1 wt%.

[0153] C may be 0.001 wt%, 0.01 wt%, 0.02 wt%, 0.5 wt%, 0.1 wt%, 0.2 wt%, 0.25 wt% or any value within the above range.

[0154] As an example, the lithium source is lithium oxalate, and the mass content of the sodium source is set based on the sum of the masses of the lithium oxalate, the catalyst, the conductive agent, and the sodium source.

[0155] The mass content of the sodium source affects the growth of the primary particles of the lithium-containing compound. As the mass content of the sodium source increases, the particle size of the primary particles of the lithium-containing compound decreases, but this leads to a decrease in the lithium content of the composite material, resulting in a smaller increase in battery capacity.

[0156] By selecting a mass content of the sodium source that satisfies the above range, it is beneficial to take into account both the capacity of the battery and the particle size of the primary particles of the lithium-containing compound.

[0157] In some embodiments, based on the sum of the weights of the lithium source, the catalyst, the conductive agent, and the sodium source, the conductive agent has a weight content of 1 wt% to 40 wt%, optionally 2 wt% to 20 wt%.

[0158] In some embodiments, based on the sum of the weights of the lithium source, the catalyst, the conductive agent, and the sodium source, the catalyst has a weight content of 0.5 wt % to 20 wt %, optionally 1 wt % to 10 wt %.

[0159] It should be noted that, in the embodiments of the present application, parameters such as the temperature of the drying process may also be set according to actual needs, and the embodiments of the present application include but are not limited to this.

[0160] In some embodiments, the lithium source includes one or more of Li2C2O4, Li2CO3, Li2C4O4, Li2C3O5, Li2C4O6, or LiOH. The lithium source can be dissolved in a solvent and can provide lithium ions, thereby obtaining a slurry including lithium ions, thereby facilitating the preparation of a composite material from the slurry.

[0161] In some embodiments, the sodium source includes one or more of NaOH, Na2CO3, NaCl, NaNO3, Na2SO4, NaHSO4, NaHCO3, Na2C2O4, Na2C4O4, Na2C3O5, and Na2C4O6. The sodium source can be dissolved in a solvent. During the drying process, sodium-containing compounds including sodium element can be precipitated prior to lithium-containing compounds, thereby providing nucleation sites for the growth of lithium-containing compounds, facilitating the formation of lithium-containing compounds, and facilitating the production of lithium-containing compounds with smaller particle sizes.

[0162] [Positive electrode]

[0163] An embodiment of the present application provides a positive electrode plate, comprising the composite material of any of the above embodiments, and / or a composite material prepared by the method of any of the above embodiments.

[0164] In some embodiments, the positive electrode sheet further includes a positive electrode active material. The positive electrode active material can be a positive electrode active material commonly known in the art for use in batteries. For example, the positive electrode active material can be lithium iron phosphate, a ternary material, a lithium-rich manganese-based material, or the like.

[0165] The positive electrode sheet includes a positive electrode current collector and a positive electrode film layer arranged on the positive electrode current collector.

[0166] The positive electrode current collector may be a metal foil or a composite current collector. For example, the positive electrode current collector may be an aluminum foil.

[0167] The composite current collector may include a polymer base layer and a metal layer formed on at least one surface of the polymer base layer. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer substrate (such as a substrate made of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0168] The positive electrode film layer may include positive electrode active materials and composite materials, and the composite materials may be used as a lithium supplement.

[0169] The positive electrode film layer may also optionally include a binder. As an example, the binder may include one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylate resin.

[0170] The positive electrode film layer may also optionally include a conductive material, which may include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0171] [Negative electrode]

[0172] The negative electrode plate includes a negative electrode current collector and a negative electrode film layer arranged on the negative electrode current collector.

[0173] The negative electrode current collector can be a metal foil or a composite current collector. The negative electrode current collector can be copper foil. The composite current collector can be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, silver alloy, etc.) on a polymer material substrate (such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0174] The negative electrode film layer includes a negative electrode active material. The negative electrode active material can be a negative electrode active material for a battery that is well known in the art. As an example, the negative electrode active material may include one or more of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, etc. The silicon-based material may include one or more of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may include one or more of elemental tin, tin oxide compounds, and tin alloys. However, the present application is not limited to these materials, and other traditional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0175] The negative electrode film layer may also optionally include a conductive material, which may include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0176] [Electrolytes]

[0177] 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 liquid, gel, or solid.

[0178] In some embodiments, the electrolyte is an electrolyte solution comprising an electrolyte salt and a solvent.

[0179] The electrolyte salt may include one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bisfluorosulfonyl imide, lithium bistrifluoromethanesulfonyl imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalatoborate, lithium bisoxalatoborate, lithium difluorodioxalatophosphate, and lithium tetrafluorooxalatophosphate.

[0180] The solvent may include one or more 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.

[0181] The electrolyte may also optionally include negative electrode film-forming additives, positive electrode film-forming additives, and may also include performance additives that can improve certain battery properties, such as improving battery overcharge performance, improving battery high or low temperature performance, etc.

[0182] [Isolation film]

[0183] The separator is used to separate the positive electrode sheet from the negative electrode sheet. The present invention has no particular restrictions on the type of separator, and any known porous separator with good chemical and mechanical stability can be used.

[0184] The material of the separator can include 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, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0185] The positive electrode sheet, the negative electrode sheet and the separator can be made into an electrode assembly through a winding process or a lamination process.

[0186] [Secondary battery]

[0187] An embodiment of the present application provides a secondary battery, comprising the positive electrode sheet in the above embodiment.

[0188] In some embodiments, the secondary battery is a secondary battery before formation. Formation can be understood as the initialization of the secondary battery, the process of activating the active material of the secondary battery; it can also be understood as the process of charging the secondary battery.

[0189] The secondary battery of the embodiment of the present application may be a battery cell, which may be a battery cell that has not been charged or discharged. For example, the battery cell is a newly assembled and unused battery cell. For example, the battery cell is a battery cell that has not undergone a formation process.

[0190] After the battery cell is assembled and used for a period of time, the lithium-containing compound in the composite material decomposes in the pole piece in the battery cell, and only a small amount of or no lithium-containing compound remains in the pole piece; the mass of the catalyst in the composite material does not change substantially.

[0191] 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. The battery cell can be a lithium-ion battery, a lithium-sulfur battery, a sodium-ion battery, or the like.

[0192] Figure 2 This is a schematic diagram of a battery cell according to an embodiment of the present application. Figure 2As shown, the battery cell 3 is a square battery cell and includes a housing 31 , an end cap assembly 32 and an electrode assembly 33 disposed in the housing 31 .

[0193] The electrode assembly 33 can be made of a positive electrode sheet, a negative electrode sheet and a separator through a winding process or a lamination process.

[0194] The end cap assembly 32 includes an electrode terminal 322, such as Figure 2 As shown, the end cap assembly 32 includes two electrode terminals 322 , one of which is a positive electrode terminal and the other is a negative electrode terminal.

[0195] The battery cell 3 further includes a current collecting member 34, which is used to connect the electrode tab 331 of the electrode assembly 33 and the electrode terminal 322. For example, when the electrode sheet 1 of the embodiment of the present application is a positive electrode sheet, one current collecting member 34 is used to connect the positive electrode tab and the positive electrode terminal, and the other current collecting member 34 is used to connect the negative electrode tab and the negative electrode terminal.

[0196] In some embodiments, battery cells may be assembled into a battery module. The number of battery cells contained in a battery module may be one or more. The specific number may be selected by those skilled in the art based on the application and capacity of the battery module.

[0197] [Battery]

[0198] An embodiment of the present application provides a battery, comprising the battery cell in the above embodiment. Figure 3 Schematic diagram of a battery according to an embodiment of the present application. Figure 3 As shown, the battery 5 may include a plurality of battery cells (not shown in the figure).

[0199] The battery cells 3 can be directly assembled into the battery 5 , or they can be assembled into battery modules first, and then multiple battery modules can be assembled into the battery 5 .

[0200] [Electrical devices]

[0201] An embodiment of the present application provides an electrical device, comprising the battery described in the above embodiment.

[0202] Figure 4 Schematic diagram of an electrical device according to an embodiment of the present application. Figure 4 As shown, the present application provides an electrical device 6, comprising the battery in the above embodiment.

[0203] Optionally, the electrical device may also be an energy storage device, a lighting device, a spacecraft, etc., and the embodiments of the present application include but are not limited to the above.

[0204] 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.

[0205] [Example]

[0206] Example 1

[0207] In Example 1, the composite material includes a lithium-containing compound, a catalyst, a conductive agent, and a small amount of a sodium-containing compound, wherein the lithium-containing compound is Li2C2O4, the catalyst is NiO, and the conductive agent is Ketjen black (KB). In the composite material, the ratio W of the molar content of the sodium element to the molar content of the lithium element is approximately 0.025 (i.e., a ratio of 0.05 to 1.95). The lithium-containing compound and the sodium-containing compound can be expressed as Li 1.95 Na 0.05 C2O4. In the composite material, the mass content A of the conductive agent is 10 wt%, and the mass content B of the catalyst is 5 wt%, based on the total mass of the composite material. The secondary particles of the composite material have a volume average particle size Dv50 of 6 μm, and the average particle size D1 of the lithium-containing compound is 100 nm (where D1 is the average particle size of the primary particles of the lithium-containing compound).

[0208] During the preparation of the composite material of Example 1, the added lithium source was Li2C2O4, and the added sodium source was Na2C2O4. The mass content C of the sodium source was 0.06 wt % based on the total mass of the sodium source, the lithium-containing compound, the catalyst, and the conductive agent. During the spray drying process, the drying temperature T was 200° C.

[0209] Examples 2-5

[0210] The difference between Example 2-5 and Example 1 is that the mass content A of the conductive agent is different.

[0211] Examples 6-9

[0212] The difference between Examples 6-9 and Example 1 is that the mass content B of the catalyst is different.

[0213] Examples 10-13

[0214] The difference between Examples 10-13 and Example 1 is that the drying temperature T is different. Accordingly, the volume average particle size Dv50 of the secondary particles of the composite material is different.

[0215] Examples 14-17

[0216] The difference between Examples 14-17 and Example 1 is that the mass content of the sodium source is different. Accordingly, the average particle size D1 of the primary particles of the lithium-containing compound is different, and the molar content of the sodium element is different.

[0217] Example 18

[0218] The difference between Example 18 and Example 1 is that the type of sodium source is different, and the mass content of the conductive agent and the catalyst is different.

[0219] Example 19

[0220] The difference between Example 19 and Example 1 is that the type and mass content of the sodium source are different, the mass content of the catalyst is different, the volume average particle size of the secondary particles of the composite material and the average particle size of the primary particles of the lithium-containing compound are different.

[0221] Example 20

[0222] The difference between Example 20 and Example 1 is that the type and mass content of the sodium source are different, the mass content of the conductive agent is different, and the volume average particle size of the secondary particles of the composite material is different.

[0223] Examples 21-23

[0224] The difference between Examples 21-23 and Example 1 is that different types of lithium-containing compounds are added during the preparation of the composite materials.

[0225] Examples 24-28

[0226] The difference between Examples 24-28 and Example 1 is that the types of catalysts are different.

[0227] Example 29

[0228] Example 29 differs from Example 1 in that lithium iron phosphate is additionally added as a positive electrode active material to prepare a battery cell. Based on the total mass of the lithium iron phosphate and the composite material, the composite material contains 5 wt% and the lithium iron phosphate contains 95 wt%.

[0229] Comparative Example 1

[0230] The difference between Comparative Example 1 and Example 1 is that its material is not a composite material, but only a lithium-containing compound Li2C2O4.

[0231] Comparative Example 2

[0232] The difference between Comparative Example 2 and Example 1 is that its material is a mixture of a lithium-containing compound Li2C2O4 and a catalyst, and there is no conductive agent.

[0233] Comparative Example 3

[0234] The difference between Comparative Example 3 and Example 1 is that its material is a mixture of a lithium-containing compound Li2C2O4 and a conductive agent, and there is no catalyst.

[0235] Comparative Example 4

[0236] Comparative Example 4 differs from Example 1 in that no sodium source is added during the preparation process. The prepared composite material includes Li2C2O4, a conductive agent, and a catalyst, but does not contain sodium. In the composite material prepared in Comparative Example 4, the average particle size of the primary particles of Li2C2O4 is larger.

[0237] Comparative Examples 5-7

[0238] The difference between Comparative Examples 5-7 and Comparative Example 1 is that the lithium-containing compounds are Li2C4O4, Li2CO3, and Li2C4O6, respectively.

[0239] Comparative Example 8

[0240] The difference between Comparative Example 8 and Comparative Example 1 is that after obtaining the compound Li2C2O4, the lithium-containing compound Li2C2O4 is subjected to sand milling treatment. After the sand milling treatment, the average particle size of the primary particles of the lithium-containing compound Li2C2O4 is larger.

[0241] Comparative Example 9

[0242] Comparative Example 9 differs from Comparative Example 4 in that lithium iron phosphate is additionally added as a positive electrode active material to prepare a battery cell. Based on the total mass of the lithium iron phosphate and the composite material, the composite material contains 5 wt% and the lithium iron phosphate contains 95 wt%.

[0243] In Comparative Examples 1-8, no sodium source was added during the slurry preparation process. Instead, the slurries were prepared by preparing the corresponding raw materials into slurries and then spray drying them. Furthermore, it should be noted that in Comparative Example 1, the material used was a simple lithium-containing compound. Although spray-dried, it was difficult to prepare the lithium-containing compound into spheres using this spray-drying method.

[0244] As shown in Tables 1, 2, and 3, in Examples 1-28 and Comparative Examples 1-8, lithium-ion battery cells were prepared using only the composite material. As shown in Table 4, in Example 29 and Comparative Example 9, lithium-ion battery cells were prepared using the composite material as the lithium supplement and lithium iron phosphate as the positive electrode active material.

[0245] In Table 1, A is the mass content of the conductive agent, B is the mass content of the catalyst, D1 is the average particle size of the primary particles of the lithium-containing compound, Dv50 is the volume average particle size of the powder of the composite material, R is the powder resistivity of the composite material, and W is the molar ratio of the sodium element to the lithium element.

[0246] Table 1 Parameters of the composite materials of Examples 1-28 and Comparative Examples 1-8

[0247]

[0248]

[0249] Table 2 Parameters of the preparation method of the composite materials of Examples 1-28 and Comparative Examples 1-8

[0250]

[0251]

[0252] Table 3 Experimental results of Examples 1-28 and Comparative Examples 1-8

[0253]

[0254] Table 4 Experimental results of Example 29 and Comparative Example 9

[0255]

[0256]

[0257] [Preparation of Battery Cells of Examples 1-28 and Comparative Examples 1-8]

[0258] (1) Preparation of positive electrode sheets: The composite material, binder polyvinylidene fluoride (PVDF), and conductive agent (acetylene black) were dissolved in N-methylpyrrolidone (NMP) at a mass ratio of 97:2:1, and the mixture was thoroughly stirred and mixed to prepare a positive electrode slurry. The positive electrode slurry was evenly coated on the positive electrode current collector aluminum foil, and then dried, cold pressed, and cut to obtain positive electrode sheets. No other active materials were added in the preparation of this positive electrode sheet.

[0259] (2) Preparation of negative electrode sheets: artificial graphite, a negative electrode active material, acetylene black, a conductive agent, styrene-butadiene rubber (SBR), and a thickener, sodium carboxymethyl cellulose (CMC-Na), are dissolved in deionized water at a mass ratio of 96:1.5:1.5:1.0, and the mixture is stirred thoroughly to prepare a negative electrode slurry; the negative electrode slurry is coated on the negative electrode current collector copper foil, and then dried, cold pressed, and cut to obtain a negative electrode sheet.

[0260] (3) Isolation film: A polypropylene film with a thickness of 13 μm was used.

[0261] (4) Preparation of electrolyte: Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a volume ratio of 1:1:1, and LiPF6 was uniformly dissolved in the above solution to obtain an electrolyte. The concentration of LiPF6 in the electrolyte was 1 mol / L.

[0262] (5) Preparation of lithium-ion battery cells: The positive electrode sheets, separators, and negative electrode sheets are stacked and wound in order to obtain an electrode assembly; the electrode assembly is placed in an outer package, and the electrolyte prepared above is added. After packaging, standing, forming, aging, and other processes, a lithium-ion battery cell is obtained.

[0263] [Preparation of Battery Cells of Example 29 and Comparative Example 9]

[0264] (1) Preparation of positive electrode sheets: The composite material and the positive electrode active material lithium iron phosphate (LFP), the binder polyvinylidene fluoride (PVDF), and the conductive agent (acetylene black) are dissolved in a solvent N-methylpyrrolidone (NMP) at a mass ratio of 97:2:1, and the mixture is thoroughly stirred and mixed to prepare a positive electrode slurry; the positive electrode slurry is evenly coated on the positive electrode current collector aluminum foil, and then dried, cold pressed, and cut to obtain a positive electrode sheet. In the preparation of this positive electrode sheet, the composite material serves as a lithium supplement.

[0265] (2) Preparation of negative electrode sheets: artificial graphite, a negative electrode active material, acetylene black, a conductive agent, styrene-butadiene rubber (SBR), and a thickener, sodium carboxymethyl cellulose (CMC-Na), are dissolved in deionized water at a mass ratio of 96:1.5:1.5:1.0, and the mixture is stirred thoroughly to prepare a negative electrode slurry; the negative electrode slurry is coated on the negative electrode current collector copper foil, and then dried, cold pressed, and cut to obtain a negative electrode sheet.

[0266] (3) Isolation film: Polypropylene film is used.

[0267] (4) Preparation of electrolyte: Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a volume ratio of 1:1:1, and LiPF6 was uniformly dissolved in the above solution to obtain an electrolyte. The concentration of LiPF6 in the electrolyte was 1 mol / L.

[0268] (5) Preparation of lithium-ion batteries: The positive electrode sheet, separator, and negative electrode sheet are stacked and wound in order to obtain an electrode assembly; the electrode assembly is placed in an outer package, and the electrolyte prepared above is added. After packaging, standing, forming, aging, and other processes, a lithium-ion battery cell is obtained.

[0269] [First lap charging capacity test]

[0270] The assembled lithium-ion battery was charged at a constant current of 0.1C to 4.25V, left to stand for 5 minutes, and the first-cycle charging capacity of the lithium-ion battery was recorded. The first-cycle charging capacity of the lithium-ion battery was obtained by dividing the first-cycle charging capacity of the battery by the mass of the corresponding active material.

[0271] In Examples 1-25, the mass of the corresponding active material refers to the mass of the composite material; in Comparative Examples 1-7, the mass of the corresponding active material refers to the mass of the active material selected for the comparative example. The specific active materials are described above and are not repeated here. For Example 26 and Comparative Example 8, the mass of the corresponding active material also includes the mass of the lithium iron phosphate.

[0272] [Volume average particle size test]

[0273] The volume average particle size can be determined by a particle size analyzer-laser diffraction method. Specifically, the standard GB / T19077-2016 can be referred to, and a laser diffraction scattering particle size analyzer can be used to measure the material according to the manufacturer's instructions. As an example, an appropriate amount of composite material is taken, and the volume average particle size of the material is tested using a Malvern 2000 (MasterSizer 2000) laser particle size analyzer. Specifically, an appropriate amount of the sample to be tested (the sample concentration is guaranteed to be 8-12% shading) is taken, 20 ml of deionized water is added, and external ultrasonic treatment is performed for 5 minutes (53KHz / 120W) to ensure that the sample is completely dispersed, and then the sample is measured according to the GB / T19077-2016 / ISO 13320:2009 standard.

[0274] [Average particle size test]

[0275] The average particle size of the lithium-containing compound can be measured by the following method. As an example, a composite material is photographed using a scanning electron microscope. The lithium-containing compound is found in the photograph. The lithium-containing compound has a rod-like shape. The lengths of the long and short sides of the rod-shaped lithium-containing compound are measured, and the average of the lengths of the long and short sides is taken as the particle size of the lithium-containing compound. Specifically, the entire area under the field of view at a magnification of 30K can be taken, and 30 primary particles of the lithium-containing compound can be selected for measurement. The average of the multiple measured particle sizes of the lithium-containing compound is taken as the average particle size.

[0276] [Testing of powder resistivity of composite materials]

[0277] The powder of the composite material was dried, and an appropriate amount of powder was weighed. The powder resistivity of the sample was then measured using a powder resistivity tester (ST2722 digital four-probe tester, manufactured by Suzhou Jingge Electronics Co., Ltd.) according to GB / T 30835-2014 at a test pressure of 20 MPa.

[0278] [Decomposition voltage test]

[0279] The decomposition voltage of the lithium-containing compound is the average charge voltage during the initial charge process, that is, the ratio of charge energy to charge capacity. The charge energy and charge capacity can be obtained using a test device connected to the lithium-ion battery.

[0280] [Testing the mass content of the conductive agent, catalyst, and lithium-containing compound in the composite material]

[0281] The components of the composite material and the mass content of each component can be measured in the following way.

[0282] As an example, an appropriate amount of composite material powder is taken, and the elemental composition of the composite material is determined by energy dispersive spectrometer. Thereafter, the material and mass content of each component are determined by thermogravimetric analysis.

[0283] As an example, take an appropriate amount of composite material powder and dissolve the powder in deionized water (or a corresponding soluble solvent). Since the lithium-containing compound can be dissolved in water, the lithium-containing compound can be separated from the composite material, the weight of the lithium-containing compound can be measured, and the mass content of the lithium-containing compound can be calculated. Afterwards, the undissolved substance in the powder is added to another solvent that can dissolve the catalyst, the weight of the catalyst is measured, and the mass content of the catalyst is calculated. Finally, a substance containing only a conductive agent can be obtained, and the mass content of the conductive agent can be obtained by weighing it.

[0284] In lithium-containing compounds, the content of doped sodium can be obtained by inductively coupled plasma emission spectrometry (ICP) testing. As an example, the test can be carried out in an inductively coupled plasma atomic emission spectrometer (e.g., ICAP7400 from Thermo Fisher Scientific, USA). An exemplary test method is as follows: 2 g of the composite material is added to an acid solution (e.g., aqua regia) and digested. The digestion can be carried out under stirring (e.g., mechanical stirring or microwave stirring), and the digestion time can be 30 min; the digested solution is added to an ICAP4700 spectrometer to quantitatively analyze the chemical composition elements in the composite material. The mass of the sodium element is determined by quantifying each element, and the molar mass of the sodium element is finally calculated.

[0285] It should be noted that the first-cycle charging capacity, volume average particle size, resistivity, decomposition voltage, mass content of the conductive agent in the composite material, mass content of the catalyst, and mass content of the lithium-containing compound in the embodiments of the present application are common knowledge in the art, have meanings known in the art, and can be measured by test methods and instruments known in the art.

[0286] In the embodiment of the present application, the capacity of the battery is reflected by the first cycle charging capacity of the battery cell.

[0287] Figure 5 This is a SEM diagram of a composite material according to an embodiment of the present application. Figure 6 FIG1 is a partially enlarged SEM diagram of a composite material according to an embodiment of the present application. Figure 7 This is a SEM diagram of a composite material of a ratio in this application. Figure 8 This is a schematic SEM diagram of a pair of composite materials used in this application.

[0288] Combine Figure 5 As shown, the composite material of the embodiment of the present application has the morphology of secondary particles, and the composite material is spherical or nearly spherical. Figure 6 As shown, a plurality of primary particles of the lithium-containing compound and a plurality of conductive agent particles (carbon material) can also be seen, and the lithium-containing compound particles and the conductive agent particles are in contact with each other. The lithium-containing compound has a rod-like or nearly rod-like shape.

[0289] Combine Figure 7 As shown, Figure 7 The composite material is prepared without adding a sodium source. In the prepared composite material, the primary particles of the lithium-containing compound have a larger particle size and are in a rhombus or nearly rhombus shape. Figure 8 As shown, Figure 8 This is a SEM diagram of lithium oxalate after sanding treatment. Figure 8 It can be seen that the sand-milled lithium oxalate particles still have a relatively large average particle size, which is about 0.6 μm to 1.5 μm.

[0290] As shown in Examples 1-28 and Comparative Examples 1-8, the composite materials of the embodiments of the present application can improve the first-cycle charging capacity of the battery cell.

[0291] As shown in Comparative Example 1 and 5-7, the lithium-containing compound has a higher decomposition voltage and a larger resistivity, and the first-cycle charging capacity of the battery prepared using only the lithium-containing compound as the active material is low.

[0292] As shown in Comparative Example 2, only the lithium-containing compound and the catalyst are mixed. The mixed material has a higher resistivity and the first-cycle charging capacity of the battery is lower.

[0293] As shown in Comparative Example 3, the decomposition voltage of the lithium-containing compound is high when only carbon materials are mixed with the lithium-containing compound, which is not conducive to increasing the battery capacity. Although the resistivity of the composite material powder is reduced in Comparative Example 3 by only mixing carbon and the lithium-containing compound, the high decomposition voltage of the lithium-containing compound makes it difficult to use normally.

[0294] As shown in Comparative Example 4, during the preparation of the composite material, no sodium source was added, the average particle size of the primary particles of the lithium-containing compound in the prepared composite material was larger, and the first-cycle charging capacity of the battery was lower.

[0295] As shown in Comparative Example 8, when only the lithium oxalate is sand-milled, the treated lithium oxalate still has a large average particle size, and the first-cycle charging capacity of the battery is low.

[0296] As shown in Examples 1-5, when the mass content of the conductive agent is set to 1wt% to 40wt%, the battery cell has a higher first-cycle charging capacity and the composite material has a lower powder resistivity; when the mass content of the conductive agent is set to 2wt% to 20wt%, the composite material has a lower powder resistivity and the battery cell has a higher capacity.

[0297] As shown in Examples 6-9, when the mass content of the catalyst is set to 0.5wt% to 20wt%, the battery cell has a higher capacity and the lithium-containing compound has a lower decomposition voltage; when the mass content of the catalyst is set to 1wt% to 10wt%, the lithium-containing compound has a lower decomposition voltage, and the battery cell has a higher first-cycle charging capacity.

[0298] As shown in Examples 10-13, the particle size of the secondary particles of the composite material is related to the temperature of the spray drying process. As the temperature of the spray drying process increases, the secondary particles of the composite material grow faster, and it is easier to obtain secondary particles of the composite material with larger particle size. When the spray drying temperature is in the range of 150°C to 250°C, secondary particles of the composite material with a volume average particle size Dv50 of 2μm to 10μm can be obtained. Furthermore, when the spray drying temperature is in the range of 175°C to 225°C, secondary particles of the composite material with a volume average particle size Dv50 of 4μm to 8μm can be obtained.

[0299] As shown in Examples 14-17, the size of the primary particles of the lithium-containing compound is related to the mass content of the sodium source. In the process of preparing the composite material, the greater the mass content of the sodium source, the more conducive it is to obtaining primary particles of the lithium-containing compound with a smaller average particle size. When the mass content of the sodium source is in the range of 0.001wt% to 0.25wt%, the average particle size D1 of the primary particles of the lithium-containing compound is in the range of 20nm to 200nm, the composite material has a lower decomposition voltage, and the battery has a higher first-cycle charging capacity. Furthermore, when the mass content of the sodium source is in the range of 0.02wt% to 0.1wt%, the average particle size D1 of the primary particles of the lithium-containing compound is in the range of 50nm to 100nm, and the battery has a higher first-cycle charging capacity.

[0300] As shown in Example 18, when the mass content of the conductive agent is 0.5wt%, the mass content of the catalyst is 0.2wt%, the volume average particle size of the secondary particles of the composite material is 6μm, the average particle size of the primary particles of the lithium-containing compound is 100nm, and the molar content ratio of the sodium element to the lithium element in the lithium-containing compound is 0.025, the composite material has a higher decomposition voltage and a higher powder resistivity, and the improvement of the first-cycle charging capacity of the battery is limited.

[0301] As shown in Example 19, when the mass content of the conductive agent is 10wt%, the mass content of the catalyst is 25wt%, the volume average particle size of the secondary particles of the composite material is 15μm, the average particle size of the primary particles of the lithium-containing compound is 300nm, and the molar content ratio of the sodium element to the lithium element in the lithium-containing compound is 0.0025, the improvement of the first-cycle charging capacity of the battery is limited.

[0302] As shown in Example 20, when the mass content of the conductive agent is 50wt%, the mass content of the catalyst is 5wt%, the volume average particle size of the secondary particles of the composite material is 1μm, the average particle size of the primary particles of the lithium-containing compound is 100nm, and the molar content ratio of the sodium element to the lithium element in the lithium-containing compound is 0.025, the improvement of the first-cycle charging capacity of the battery is limited.

[0303] As shown in Examples 21-23, the embodiments of the present application are applicable to a variety of different lithium-containing compounds, and the composite materials containing different lithium-containing compounds have different capacities; as shown in Examples 24-28, the embodiments of the present application are applicable to a variety of different catalysts.

[0304] As shown in Example 29 and Comparative Example 9, after the composite material of the embodiment of the present application is mixed with the positive electrode active material lithium iron phosphate, the battery cell prepared has a higher capacity.

[0305] Although only lithium iron phosphate is shown as the positive electrode active material in the embodiment, the composite material of the present application is also applicable to battery cells with other active materials.

[0306] 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 material, characterized in that include: Containing lithium compounds, catalysts and conductive agents, in, The lithium-containing compound includes lithium, carbon and oxygen; The catalyst includes one or more of a transition metal oxide, a transition metal carbide, a transition metal nitride or a transition metal phosphide; The average particle size D1 of the lithium-containing compound satisfies: D1≤200 nm.

2. The composite material according to claim 1, characterized in that 20nm≤D1≤200nm.

3. The composite material according to claim 1 or 2, characterized in that 50nm≤D1≤150nm.

4. The composite material according to any one of claims 1 to 3, characterized in that The composite material further comprises a sodium-containing compound, and the sodium-containing compound comprises sodium element.

5. The composite material according to claim 4, characterized in that In the composite material, a ratio W of the molar content of the sodium element to the molar content of the lithium element satisfies: 0.005≤W≤0.

12.

6. The composite material according to claim 5, characterized in that 0.025≤W≤0.05。 7. The composite material according to any one of claims 1 to 6, characterized in that The chemical formula of the lithium-containing compound is Li2C x O y , where 1≤x≤4, 3≤y≤6.

8. The composite material according to claim 7, characterized in that The lithium-containing compound includes one or more of Li2C2O4, Li2CO3, Li2C4O4, Li2C3O5 or Li2C4O6.

9. The composite material according to any one of claims 1 to 8, characterized in that The composite material has a morphology of secondary particles; and / or the lithium-containing compound has a morphology of primary particles.

10. The composite material according to any one of claims 1 to 9, characterized in that The volume average particle size Dv50 of the composite material satisfies: 2 μm≤Dv50≤10 μm.

11. The composite material according to claim 10, characterized in that 4μm≤Dv50≤8μm.

12. The composite material according to any one of claims 1 to 11, characterized in that Based on the total mass of the composite material, the mass content A of the conductive agent satisfies: 1 wt%≤A≤40 wt%.

13. The composite material according to claim 12, characterized in that 2wt%≤A≤20wt%.

14. The composite material according to any one of claims 1 to 13, characterized in that Based on the total mass of the composite material, the mass content B of the catalyst satisfies: 0.5 wt%≤B≤20 wt%.

15. The composite material according to claim 14, characterized in that 1wt%≤B≤10wt%.

16. The composite material according to any one of claims 1 to 15, characterized in that The chemical formula of the transition metal oxide is M α O β , wherein 0<α≤3, 0<β≤5, and M includes one or more of Ni, Co, Fe, Mn, V, Cr, Cu or Ti.

17. The composite material according to claim 16, characterized in that M α O β Including: one or more of NiO, Co3O4, Fe2O3, MoO3 or V2O5.

18. The composite material according to any one of claims 1 to 17, characterized in that The carbide of the transition metal includes one or more of molybdenum carbide, vanadium carbide, tungsten carbide, titanium carbide, cobalt carbide, iron carbide or nickel carbide; and / or, the nitride of the transition metal includes one or more of molybdenum nitride, vanadium nitride, titanium nitride, manganese nitride, cobalt nitride, iron nitride or nickel nitride; and / or, the phosphide of the transition metal includes one or more of nickel phosphide, cobalt phosphide, manganese phosphide, tungsten phosphide or molybdenum phosphide.

19. The composite material according to any one of claims 1 to 18, characterized in that The conductive agent includes a carbon material.

20. The composite material according to claim 19, characterized in that The conductive agent includes a carbon-based conductive agent.

21. The composite material according to claim 20, characterized in that The carbon-based conductive agent includes one or more of carbon nanotubes, carbon fibers, acetylene black, Ketjen black, conductive carbon black, C60 or graphene.

22. The composite material according to any one of claims 1 to 21, characterized in that The powder resistivity R of the composite material under 20 MPa satisfies: R≤360Ω·cm.

23. The composite material according to claim 22, characterized in that R≤1Ω·cm.

24. A method for preparing a composite material, characterized in that: include: adding a lithium source, a catalyst, a conductive agent, and a sodium source into a solvent to obtain a slurry, wherein the catalyst comprises one or more of a transition metal oxide, a transition metal carbide, a transition metal nitride, or a transition metal phosphide; The slurry is dried to obtain the composite material.

25. The preparation method according to claim 24, characterized in that The step of drying the slurry to obtain the composite material comprises: The slurry is dried by spray drying to obtain the composite material.

26. The preparation method according to claim 24 or 25, characterized in that The temperature T of the drying process satisfies: 150°C≤T≤250°C.

27. The preparation method according to claim 26, characterized in that 175℃≤T≤225℃。 28. The preparation method according to any one of claims 24 to 27, characterized in that: Based on the sum of the masses of the lithium source, the catalyst, the conductive agent and the sodium source, the mass content C of the sodium source satisfies: 0.001 wt % ≤ C ≤ 0.25 wt %.

29. The preparation method according to claim 28, characterized in that 0.02wt%≤C≤0.1wt%.

30. The preparation method according to any one of claims 24 to 29, characterized in that: The lithium source includes one or more of Li2C2O4, Li2CO3, Li2C4O4, Li2C3O5, Li2C4O6 or LiOH.

31. The preparation method according to any one of claims 24 to 30, characterized in that The sodium source includes one or more of NaOH, Na2CO3, NaCl, NaNO3, Na2SO4, NaHSO4, NaHCO3, Na2C2O4, Na2C4O4, Na2C3O5 or Na2C4O6.

32. A positive electrode plate, characterized in that: include: The composite material according to any one of claims 1 to 23, and / or the composite material obtained by the preparation method according to any one of claims 24 to 31.

33. A secondary battery, characterized in that: Including the positive electrode sheet as described in claim 32.

34. The secondary battery according to claim 33, characterized in that The secondary battery is a secondary battery before formation.

35. An electrical device, characterized in that: Includes the secondary battery as described in claim 33 or 34.

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