Positive electrode active material and preparation method therefor, positive electrode sheet, battery cell, battery and electrical apparatus

Abstract

A positive electrode active material and a preparation method therefor, a positive electrode sheet, a battery cell, a battery, and an electrical apparatus. The positive electrode active material comprises Li1-xNaxNiaM1bCocM2dMneO2, wherein M1 comprises Fe, M2 comprises Al, 0.01≤x≤0.4, 0.5≤a≤0.98, 0≤b≤0.3, 0≤c≤0.3, 0≤d≤0.1, 0≤e≤0.45, and a+b+c+d+e=1. The technical solution can reduce the impact on the energy density of batteries while reducing the production cost of batteries.

Description

Positive electrode active material and preparation method thereof, positive electrode sheet, battery cell, battery and electrical device

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This patent document claims priority to and the benefit of Chinese patent application No. 202311447829.1, filed on November 2, 2023, entitled "Positive Electrode Active Material and Preparation Method Thereof, Positive Electrode Sheet, Battery Cell, Battery, and Electric Device." The entire contents of the aforementioned patent application are incorporated by reference into this patent document. Technical Field

[0003] The present application relates to the field of battery technology, and more specifically, to a positive electrode active material and a preparation method thereof, a positive electrode sheet, a battery cell, a battery, and an electrical device. Background Art

[0004] In recent years, lithium-ion batteries have been used in an increasingly diverse range of applications, including energy storage and power supply applications such as wind, hydro, thermal, and solar power plants, as well as in electric bicycles, electric motorcycles, military equipment, and aerospace. This significant advancement in lithium-ion batteries has also led to higher performance requirements across all aspects of their application.

[0005] Therefore, how to reduce the cost of battery production without affecting the performance of the battery is an urgent problem that needs to be solved.

[0006] Summary of the Invention

[0007] This application is made in view of the above-mentioned problems, and its purpose is to provide a positive electrode active material and its preparation method, a positive electrode plate, a battery cell, a battery and an electrical device, which can reduce the impact on battery energy density while reducing battery production costs.

[0008] In a first aspect, a positive electrode active material is provided, comprising: Li 1-x Na x Ni a M1 b Co c M2 d Mn e O2; wherein, M1 includes Fe, M2 includes Al, 0.01≤x≤0.4, 0.5≤a≤0.98, 0≤b≤0.3, 0≤c≤0.3, 0≤d≤0.1, 0≤e≤0.45, a+b+c+d+e=1.

[0009] In the embodiment of the present application, the positive electrode active material includes Li 1-x Na x Ni a M1b Co c M2 d Mn e O2, where M1 includes Fe and M2 includes Al, and 0.01≤x≤0.4. Metallic sodium is relatively cheap compared to metallic lithium. By replacing some lithium with sodium and controlling the replacement ratio between 1% and 40%, battery production costs can be reduced while minimizing the impact on battery energy density.

[0010] In a possible implementation, at a voltage of 4.25 V, x and a satisfy: x≤0.67-0.6a.

[0011] In the embodiment of the present application, 4.25V is Li 1-x Na x Ni a Fe b Co c Al d Mn e The upper limit voltage of O2 can be further guaranteed by making x and a satisfy: x≤0.67-0.6a, that is, the sodium substitution amount x meets the theoretical requirements, which can further ensure the energy density of the battery.

[0012] In one possible implementation, 0.01≤x≤0.2.

[0013] In one possible implementation, 0.05≤x≤0.15.

[0014] In the present embodiment, sodium is substituted for part of the lithium in the positive electrode active material, lithium nickel cobalt manganese oxide, to reduce battery production costs. Furthermore, by maintaining the substitution ratio between 1% and 20%, particularly between 5% and 15%, the battery's high energy density can be further maintained while reducing battery production costs.

[0015] In a possible implementation manner, b and c satisfy: 0.01≤b+c≤0.3.

[0016] In the embodiment of the present application, the content of iron and cobalt elements will affect the power performance of the battery. By making the sum of b+c satisfy: 0.01≤b+c≤0.3, the normal energy density of the battery can be guaranteed, and the power of the battery can also be guaranteed.

[0017] In a possible implementation manner, d and e satisfy: 0.01≤d+e≤0.45.

[0018] In the embodiment of the present application, the content of aluminum and manganese elements will affect the structural stability of the battery. By making the sum of d+e satisfy: 0.01≤b+c≤0.45, the normal energy density of the battery can be ensured, and the structural stability of the battery can also be ensured.

[0019] The second aspect of the present application provides a method for preparing a positive electrode active material, the preparation method comprising: dissolving a lithium source, a sodium source, a nickel source, an iron source, a cobalt source, an aluminum source, and a manganese source in a solution of deionized water containing citric acid to obtain a mixed solution, wherein the mass ratio of the lithium source, the sodium source, the nickel source, the iron source, the cobalt source, the aluminum source, and the manganese source to the mass of the citric acid is 1:1; stirring and drying the mixed solution to obtain a positive electrode active material precursor; sintering the positive electrode active material precursor to obtain the positive electrode active material; wherein the positive electrode active material comprises Li 1-x Na x Ni a M1 b Co c M2 d Mn e O2, M1 includes Fe, M2 includes Al, 0.01≤x≤0.4, 0.5≤a≤0.98, 0≤b≤0.3, 0≤c≤0.3, 0≤d≤0.1, 0≤e≤0.45, a+b+c+d+e=1.

[0020] In one possible embodiment, the mixed solution is stirred at 60° C. until a solid gel is formed; the solid gel is dried at 100° C. and 400° C. for 12 h and 4 h, respectively, to obtain the positive electrode active material precursor.

[0021] In a possible implementation, the cathode active material precursor is calcined at 750° C. in an oxygen atmosphere for 20 hours to obtain the cathode active material.

[0022] The third aspect of the present application provides a positive electrode plate, comprising: a positive electrode current collector and a positive electrode film layer arranged on at least one side of the positive electrode current collector; the positive electrode film layer comprises the positive electrode active material described in any embodiment of the first aspect, or the positive electrode active material prepared by the preparation method of the positive electrode active material described in the second aspect.

[0023] The fourth aspect of the present application provides a battery cell, comprising the positive electrode sheet described in the third aspect of the present application.

[0024] The fifth aspect of the present application provides a battery, comprising the battery cell described in the fourth aspect of the present application.

[0025] The sixth aspect of the present application provides an electrical device comprising the battery described in the fifth aspect of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] 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.

[0027] FIG1 is a flow chart of a method for preparing a positive electrode active material according to an embodiment of the present application;

[0028] FIG2 is a schematic structural diagram of a positive electrode sheet according to an embodiment of the present application;

[0029] FIG3 is a schematic diagram of a battery cell according to an embodiment of the present application;

[0030] FIG4 is a schematic structural diagram of a battery cell according to an embodiment of the present application;

[0031] FIG5 is a schematic diagram of a battery according to an embodiment of the present application;

[0032] FIG6 is a schematic structural diagram of a battery according to an embodiment of the present application;

[0033] FIG7 is a schematic structural diagram of an electrical device according to an embodiment of the present application. DETAILED DESCRIPTION

[0034] The following describes in detail embodiments of the positive electrode active material and its preparation method, positive electrode sheet, battery cell, battery, and electrical device of the present application, with appropriate reference to the accompanying drawings. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repeated descriptions of substantially identical structures may be omitted. In addition, the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0035] " 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 specific 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.

[0036] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0037] 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.

[0038] Unless otherwise specified, all steps of the present application may be performed sequentially, randomly, or optionally 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.

[0039] In the 21st century, humanity faces two critical challenges: energy crisis and environmental pollution. Therefore, the development and research of clean, renewable energy sources is of far-reaching significance. Automobiles account for approximately 40% of oil consumption, and 42% of global air pollution comes from vehicle emissions. Countries around the world attach great importance to electric vehicles, and my country's 863 Plan also lists their development as a key direction. Research on power batteries, which serve as on-board power sources, has become a major bottleneck in the development of electric vehicles. Currently, the main candidates for power batteries include nickel-metal hydride batteries, lithium-ion batteries, and fuel cells. Lithium-ion batteries offer significant advantages in terms of cost-effectiveness. As energy storage materials, lithium-ion batteries offer advantages over traditional materials, such as high voltage, high specific capacity, long cycle life, and excellent safety. They are widely used in portable electronic devices, electric vehicles, aerospace, and military engineering, offering a wide range of applications and significant economic benefits.

[0040] Cathode materials, as a crucial component of lithium-ion batteries, are a hot topic of research. This is because the performance of the cathode active material largely determines the overall performance of the entire lithium-ion battery. Currently, ternary materials are considered the material of choice for lithium-ion batteries due to their smaller size, higher energy density, and improved safety. However, when using ternary materials as cathode active materials for lithium-ion batteries, how to achieve both high energy density and low production costs, and thereby facilitate their wider application in production, remains a pressing technical challenge.

[0041] In view of this, the present application provides a positive electrode active material, which includes Li 1-x Na x Ni a M1 b Co c M2 d Mn e O2; wherein M1 includes Fe, M2 includes Al, 0.01≤x≤0.4, 0.5≤a≤0.98, 0≤b≤0.3, 0≤c≤0.3, 0≤d≤0.1, 0≤e≤0.45, and a+b+c+d+e=1. By replacing some lithium with sodium, the production cost of the battery can be reduced without significantly affecting the battery's energy density.

[0042] The positive electrode active material and preparation method thereof, positive electrode sheet, battery cell, battery and electrical equipment of the present application are described below with reference to the accompanying drawings.

[0043] In addition, the technical solution of the present application is applicable to various types of batteries such as lithium-ion batteries and lithium metal batteries, and the present application does not limit this; for the convenience of description, the following description will take lithium-ion batteries as an example.

[0044] [Positive electrode active material]

[0045] The first aspect of the present application provides a positive electrode active material, which includes: Li 1-x Na x Ni a M1 b Co c M2 d Mn e O2; wherein, M1 includes Fe, M2 includes Al, 0.01≤x≤0.4, 0.5≤a≤0.98, 0≤b≤0.3, 0≤c≤0.3, 0≤d≤0.1, 0≤e≤0.45, a+b+c+d+e=1.

[0046] When the layered ternary material lithium nickel cobalt manganese oxide is in use, in order to maintain the stability of the structure, some lithium ions need to be maintained in the structure. Therefore, this part of the lithium can be replaced with sodium, thereby reducing the cost of the lithium nickel cobalt manganese oxide material.

[0047] The value of a represents the molar content of nickel in the material. When the value of a is greater than 0.7, the positive electrode active material can be called a nickel-rich material (also called a high-nickel material). When the value of a is 0.5-0.7, the positive electrode active material can be called a medium-nickel material. Using medium-nickel materials or high-nickel materials can make the battery have a higher energy density.

[0048] b and c represent the molar contents of iron and cobalt in the material. Keeping them within the above ranges can improve the power capacity of the positive electrode active material.

[0049] d and e represent the molar contents of aluminum and manganese in the material. Keeping them within the above ranges can improve the structural stability of the positive electrode active material.

[0050] In the above scheme, the positive electrode active material includes Li 1-x Na x Ni a M1 b Co c M2 d Mn e O2, where M1 includes Fe, M2 includes Al, and 0.01≤x≤0.4. The price of metallic sodium is lower than that of metallic lithium. By replacing some lithium with sodium and controlling the replacement ratio between 1% and 40%, the battery production cost can be reduced while minimizing the impact on battery energy density.

[0051] Specifically, the value of x can be 0.01, 0.02, 0.05, 0.1, 0.2, 0.3, 0.4 or any value within the above range.

[0052] Specifically, the value of a can be 0.5, 0.55, 0.6, 0.8, 0.9, 0.95 or any value within the above range.

[0053] Specifically, the value of b can be 0.01, 0.05, 0.1, 0.15, 0.2, 0.3 or any value within the above range.

[0054] Specifically, the value of c can be 0, 0.02, 0.05, 0.1, 0.2, 0.3 or any value within the above range.

[0055] Specifically, the value of d can be 0, 0.02, 0.05, 0.08, 0.1 or any value within the above range.

[0056] Specifically, the value of e can be 0.5, 0.9, 1.5, 2.6, 3.8, 4.5 or any value within the above range.

[0057] It should be noted that the values ​​of a, b, c, d and e can be any values ​​within the above range, but must satisfy: a+b+c+d+e=1.

[0058] In some embodiments, the positive electrode active material Li 1-x Na x Ni a M1 b Co c M2 d Mn e O2 can also include Li 1-x Na x Ni a M1 b Co c M2 d Mn e O f A g , wherein A includes at least one of S, N, P, F, Cl, Br or I, 0≤f≤2, 0≤g≤2.

[0059] Specifically, the positive electrode active materials include but are not limited to the following substances: Li 0.6 Na 0.4 Ni 0.5 Fe 0.1 Co 0.1 Al 0.05 Mn 0.25 O2、Li 0.7 Na 0.3 Ni 0.6 Fe 0.05 Co 0.2 Al 0.05 Mn 0.1 O1.9 S 0.1 .

[0060] It should be noted that in the positive electrode sheet, battery, or electrical device, lithium ions are consumed during the battery formation and cycling processes, so the measured sum of lithium and sodium in the positive electrode active material may be less than 1. At the same time, if the positive electrode sheet is replenished with lithium, the measured sum of lithium and sodium in the positive electrode material may be greater than 1 after the battery formation and cycling processes.

[0061] Similarly, in the list of positive electrode active materials in this application, the molar content of oxygen is only a theoretical value. The release of oxygen from the lattice will cause the molar content of oxygen to change, and the actual molar content of oxygen will fluctuate.

[0062] In some embodiments, at a voltage of 4.25 V, x and a satisfy: x≤0.67-0.6a.

[0063] The amount of lithium removed from the material varies at different voltages. The higher the battery's operating voltage, the more lithium is removed from the positive electrode active material, leaving less remaining lithium. Replacing the remaining lithium with sodium reduces costs without compromising battery performance.

[0064] After a large number of experiments, the applicant fitted the relationship between the initial lithium desorption amount a and the lithium desorption amount y of the battery as: y = 0.6a + 0.33, then the theoretical remaining lithium content is 1-y, that is, 0.67-0.6a, then the remaining lithium content in the material should be 0.67-0.6a, then x should theoretically satisfy: x≤0.67-0.6a.

[0065] In the above scheme, 4.25V is Li 1-x Na x Ni a Fe b Co c Al d Mn e The upper limit voltage of O2 can be further guaranteed by making x and a satisfy: x≤0.67-0.6a, that is, the sodium substitution amount x meets the theoretical requirements, which can further ensure the energy density of the battery.

[0066] In some embodiments, 0.01≤x≤0.2.

[0067] In some embodiments, 0.05≤x≤0.15.

[0068] In the above scheme, sodium is used to replace some of the lithium in the positive electrode active material, lithium nickel cobalt manganese oxide, to reduce battery production costs. Furthermore, by maintaining the replacement ratio between 1% and 20%, particularly between 5% and 15%, the battery's high energy density can be further maintained while reducing production costs.

[0069] In some embodiments, b and c satisfy: 0.01≤b+c≤0.3.

[0070] In the above scheme, the content of iron and cobalt elements will affect the power performance of the battery. By making the sum of b+c satisfy: 0.01≤b+c≤0.3, the normal energy density and power of the battery can be guaranteed.

[0071] In some embodiments, d and e satisfy: 0.01≤d+e≤0.45.

[0072] In the above scheme, the content of aluminum and manganese elements will affect the structural stability of the battery. By making the sum of d+e satisfy: 0.01≤b+c≤0.45, the normal energy density of the battery can be guaranteed, and the structural stability of the battery can also be guaranteed.

[0073] [Method for preparing positive electrode active material]

[0074] A second aspect of the present application provides a method for preparing a positive electrode active material. FIG1 is a flow chart of a method for preparing a positive electrode active material according to an embodiment of the present application. As shown in FIG1 , the method 100 includes:

[0075] 101: dissolving a lithium source, a sodium source, a nickel source, an iron source, a cobalt source, an aluminum source, and a manganese source in a solution containing deionized water containing citric acid to obtain a mixed solution;

[0076] In the above step 101, the mass ratio of the lithium source, sodium source, nickel source, iron source, cobalt source, aluminum source, and manganese source to the mass ratio of the citric acid is 1:1.

[0077] 102: The mixed solution is stirred and dried to obtain a positive electrode active material precursor.

[0078] 103: Sintering the positive electrode active material precursor to obtain the positive electrode active material.

[0079] Among them, the positive electrode active material includes Li 1-x Na x Ni a M1 b Co c M2 d Mn eO2, M1 includes Fe, M2 includes Al, 0.01≤x≤0.4, 0.5≤a≤0.98, 0≤b≤0.3, 0≤c≤0.3, 0≤d≤0.1, 0≤e≤0.45, a+b+c+d+e=1.

[0080] It should be noted here that the above-mentioned sodium source, nickel source, iron source, cobalt source, aluminum source, and manganese source can be selected from the raw materials known in the art for preparing lithium nickel cobalt manganese oxide, and the sodium source can be selected from the sodium-containing metal salts known in the art, such as sodium carbonate or sodium hydroxide.

[0081] In some embodiments, the mixed solution is stirred at 60° C. until a solid gel is formed; the solid gel is dried at 100° C. and 400° C. for 12 h and 4 h, respectively, to obtain a positive electrode active material precursor.

[0082] In some embodiments, the cathode active material precursor is calcined at 750° C. in an oxygen atmosphere for 20 hours to obtain the cathode active material.

[0083] In some embodiments, the positive electrode active material may also include positive electrode active materials for batteries known in the art. As an example, the positive electrode active material may also include lithium-containing phosphates with an olivine structure. However, the present application is not limited to these materials and may also include other traditional materials that can be used as battery-active positive electrode materials. These positive electrode active materials may be used in combination of two or more. Among them, examples of lithium-containing phosphates with an olivine structure may include, but are not limited to, at least one of a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO4), a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon.

[0084] [Positive electrode]

[0085] The third aspect of the present application provides a positive electrode sheet. Figure 2 is a schematic structural diagram of a positive electrode sheet according to one embodiment of the present application. As shown in Figure 2, the positive electrode sheet 121 includes a positive electrode current collector 122 and a positive electrode film layer 123 disposed on at least one side of the positive electrode current collector 122. The positive electrode film layer 123 includes the positive electrode active material according to any embodiment of the first aspect, or a positive electrode active material prepared according to the method for preparing the positive electrode active material according to the second aspect.

[0086] Typically, a battery cell consists of a positive electrode sheet 121, a separator, a negative electrode sheet, and an electrolyte. During the battery's charge and discharge processes, active ions are intercalated and released between the positive and negative electrodes. The electrolyte transfers ions between the positive and negative electrodes. The separator, located between the positive and negative electrodes, primarily prevents short circuits between the positive and negative electrodes while allowing ions to pass through.

[0087] It should be noted here that the “positive electrode sheet” and “negative electrode sheet” mentioned in the embodiments of the present application refer to the positive electrode sheet and the negative electrode sheet as a whole including active materials, current collectors or other additives.

[0088] The positive electrode sheet 121 includes a positive electrode current collector 122 and a positive electrode film layer 123 disposed on at least one surface of the positive electrode current collector 122 . The positive electrode film layer 123 includes a positive electrode active material.

[0089] As an example, the positive electrode current collector 122 has two opposite surfaces in its thickness direction, and the positive electrode film layer 123 is disposed on either or both of the two opposite surfaces of the positive electrode current collector 122 .

[0090] In some embodiments, the positive electrode current collector 122 may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material 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 material substrate (such as a substrate made of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0091] In some embodiments, the positive electrode film layer 123 may further include a binder. As an example, the binder may include at least one 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.

[0092] In some embodiments, the positive electrode film layer 123 may further include a conductive agent. For example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0093] In some embodiments, the positive electrode sheet 121 can be prepared by the following method: the components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder and any other components are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry, and the positive electrode slurry is coated on the positive electrode current collector 122. After drying, cold pressing and other processes, the positive electrode sheet 121 can be obtained.

[0094] [Negative electrode]

[0095] The negative electrode sheet includes a negative electrode current collector and a negative electrode film layer provided on at least one surface of the negative electrode current collector, wherein the negative electrode film layer includes a negative electrode active material.

[0096] As an example, the negative electrode current collector has two surfaces opposite to each other in its thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0097] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer base layer and a metal layer formed on at least one surface of the polymer base material. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer base material (such as a base material of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0098] In some embodiments, the negative electrode active material may 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 at least one 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 be selected from at least one of elemental silicon, silicon oxides, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxides, 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.

[0099] In some embodiments, the negative electrode film layer may further include a binder. The binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0100] In some embodiments, the negative electrode film layer may further include a conductive agent, which may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0101] In some embodiments, the negative electrode film layer may optionally include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0102] In some embodiments, the negative electrode sheet can be prepared by the following method: the components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder and any other components, are dispersed in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode current collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.

[0103] [Electrolytes]

[0104] The electrolyte acts as a conductive medium between the positive electrode 121 and the negative electrode. The present application 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.

[0105] In some embodiments, the electrolyte is an electrolyte solution comprising an electrolyte salt and a solvent.

[0106] In some embodiments, the electrolyte salt may be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalatoborate, lithium dioxalatoborate, lithium difluorodioxalatophosphate, and lithium tetrafluorooxalatophosphate.

[0107] In some embodiments, the solvent can be selected from at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methylpropyl carbonate, ethylpropyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclopentane, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.

[0108] In some embodiments, the electrolyte may further include electrolyte additives. For example, the electrolyte additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, and additives that improve battery high or low temperature performance.

[0109] [Isolation film]

[0110] In some embodiments, the battery cell further includes a separator. The present application has no particular limitation on the type of separator, and any known porous separator with good chemical and mechanical stability can be selected.

[0111] In some embodiments, the material of the separator can be selected from at least one 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.

[0112] In some embodiments, the positive electrode sheet 121 , the negative electrode sheet, and the separator may be formed into an electrode assembly through a winding process or a lamination process.

[0113] In some embodiments, the battery cell may include an outer packaging that can be used to encapsulate the electrode assembly and the electrolyte.

[0114] In some embodiments, the outer packaging of the battery cell may be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. Alternatively, the outer packaging of the battery cell may be a soft shell, such as a pouch-type soft shell. The soft shell may be made of plastic, such as polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0115] The present application has no particular limitation on the shape of the battery cell, which can be cylindrical, square, or any other shape. For example, FIG3 is a schematic diagram of a battery cell according to an embodiment of the present application.

[0116] Figure 4 is a schematic structural diagram of a battery cell according to an embodiment of the present application. As shown in Figure 4, the outer packaging of the battery cell 200 includes a shell 11 and a cover plate 13. The shell 11 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 11 has an opening connected to the receiving cavity, and the cover plate 13 can be covered on the opening to close the receiving cavity. The positive electrode sheet 121 and the negative electrode sheet can be formed into an electrode assembly 12 by a winding process or a lamination process. The electrode assembly 12 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 12. The number of electrode assemblies 12 contained in the battery cell 200 may be one or more, and those skilled in the art can select according to specific actual needs.

[0117] In some embodiments, the battery cells 200 may be assembled into a battery module. The battery module may contain one or more battery cells 200. The specific number may be selected by those skilled in the art based on the application and capacity of the battery module.

[0118] Figure 5 is a schematic diagram of a battery according to one embodiment of the present application, and Figure 6 is a schematic diagram of the structure of a battery according to one embodiment of the present application. Referring to Figures 5 and 6, a battery 400 may include a battery box and a plurality of battery cells 200 disposed within the battery box. The battery box includes an upper box body 401 and a lower box body 402. The upper box body 401 can be placed over the lower box body 402 to form an enclosed space for accommodating the battery cells 200. The plurality of battery cells 200 can be arranged in any manner within the battery box.

[0119] In addition, the present application also provides an electrical device, which includes at least one of the positive electrode sheet 121, battery cell 200, or battery 400 provided in the present application. The positive electrode sheet 121, battery cell 200, or battery 400 can be used as a power source for the electrical device, or as an energy storage unit for the electrical device. The electrical device may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but is not limited thereto.

[0120] For example, FIG7 is a schematic structural diagram of an electric device according to an embodiment of the present application. As shown in FIG7 , the electric device 1 is a vehicle 1. The vehicle 1 may be a fuel vehicle, a gas vehicle or a new energy vehicle. The new energy vehicle may be a pure electric vehicle, a hybrid vehicle or an extended-range vehicle, etc. A motor 500, a controller 600 and a battery 400 may be provided inside the vehicle 1. The controller 600 is used to control the battery 400 to supply power to the motor 500. For example, a battery 400 may be provided at the bottom, front or rear of the vehicle 1. The battery 400 may be used to power the vehicle 1. For example, the battery 400 may be used as an operating power source for the vehicle 1, for the circuit system of the vehicle 1, for example, for the working power requirements during the start-up, navigation and operation of the vehicle 1. In another embodiment of the present application, the battery 400 may not only be used as an operating power source for the vehicle 1, but also as a driving power source for the vehicle 1, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle 1.

[0121] As the electrical device, the positive electrode sheet 121 , the battery cell 200 or the battery 400 may be selected according to its usage requirements.

[0122] The electric device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. In order to meet the electric device's requirements for high power and high energy density of the battery, a battery cell 200 or a battery 400 may be used.

[0123] As another example, the device may be a mobile phone, a tablet computer, a notebook computer, etc. Such a device is usually required to be lightweight and thin, and may use a battery cell 200 as a power source.

[0124] [Example]

[0125] 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.

[0126] [Example 1]

[0127] 1). Preparation of lithium-ion batteries

[0128] 1.11) Preparation of positive electrode active material: lithium acetate, sodium acetate, nickel acetate, cobalt acetate, manganese acetate, and citric acid were dissolved in deionized water at a mass ratio of 35.59 g: 32.81 g: 68.38 g: 74.72 g: 34.61 g: 250.12 g to form a positive electrode active material solution; the positive electrode active material solution was continuously stirred at 60°C until a solid gel was formed, and then dried at 100°C for 12 h and at 400°C for 4 h to form a positive electrode active material precursor; and then calcined in an oxygen atmosphere at 750°C for 20 h to obtain the positive electrode active material Li 0.6 Na 0.4 Ni 0.5 Co 0.3 Mn 0.2 O2, where x is 0.4, a is 0.5, b is 0, c is 0.3, d is 0, e is 0.2, b+c is 0.3, and d+e is 0.2.

[0129] 1.12) Preparation of positive electrode sheet: The positive electrode active material Li prepared in Example 1 0.6 Na 0.4 Ni 0.5 Co 0.3 Mn 0.2 O2, conductive agent carbon nanotubes (CNT), and positive electrode binder polyvinylidene fluoride (PVDF) are dissolved in solvent N-methylpyrrolidone (NMP) in a weight ratio of 96%:2%:2%. After being fully stirred and mixed, a positive electrode slurry is prepared. The positive electrode slurry is coated on Al foil, and then dried, cold pressed, and cut to obtain a positive electrode sheet.

[0130] 1.2) Preparation of negative electrode sheets: artificial graphite, a conductive agent, acetylene black, a negative electrode binder, styrene-butadiene rubber (SBR), and a thickener, sodium carboxymethyl cellulose (CMC-Na), are mixed thoroughly in a suitable amount of deionized water solvent system at a weight ratio of 96.5%:0.7%:1.8%:1% to obtain a negative electrode slurry. The negative electrode slurry is coated on a Cu foil, and then dried, cold pressed, and cut to obtain a negative electrode sheet.

[0131] 1.3) Preparation of diaphragm: PE porous polymer film is used as the isolation membrane.

[0132] 1.4) Electrolyte: Dissolve EC / EMC / DMC in 1M LiPF6 at a volume ratio of 1:1:1 and stir evenly to obtain 1 mol / L LiPF6 electrolyte.

[0133] 1.5) Assembly: The positive electrode sheet, separator, and negative electrode sheet are stacked in order, with the separator positioned between the positive and negative electrodes to provide isolation. The electrodes are then wound to form an electrode assembly, and electrolyte is added. The lithium-ion battery is then produced through formation and resting processes.

[0134] [Example 2]

[0135] The preparation process of the lithium ion battery of Example 2 is basically the same as that of Example 1, except that, in Example 2, the mass ratio of lithium acetate, sodium acetate, nickel acetate, cobalt acetate, manganese acetate, and citric acid in the positive electrode active material is 46.19 g: 24.61 g: 68.38 g: 74.72 g: 34.61 g: 248.51 g; wherein x is 0.3, a is 0.5, b is 0, c is 0.3, d is 0, e is 0.2, b + c is 0.3, and d + e is 0.2.

[0136] [Example 3]

[0137] The preparation process of the lithium ion battery of Example 3 is basically the same as that of Example 1, except that, in Example 3, the mass ratio of lithium acetate, sodium acetate, nickel acetate, cobalt acetate, manganese acetate, and citric acid in the positive electrode active material is 52.79 g: 16.41 g: 68.38 g: 74.72 g: 34.61 g: 246.91 g; wherein x is 0.2, a is 0.5, b is 0, c is 0.3, d is 0, e is 0.2, b + c is 0.3, and d + e is 0.2.

[0138] [Example 4]

[0139] The preparation process of the lithium ion battery of Example 4 is basically the same as that of Example 1, except that, in Example 4, the mass ratio of lithium acetate, sodium acetate, nickel acetate, cobalt acetate, manganese acetate, and citric acid in the positive electrode active material is 65.33 g:0.82 g:68.38 g:74.72 g:34.61 g:243.86 g; wherein x is 0.01, a is 0.5, b is 0, c is 0.3, d is 0, e is 0.2, b+c is 0.3, and d+e is 0.2.

[0140] [Example 5]

[0141] The preparation process of the lithium-ion battery of Example 5 is basically the same as that of Example 1, except that in Example 5, the mass ratio of lithium acetate, sodium acetate, nickel acetate, cobalt acetate, manganese acetate, and citric acid in the positive electrode active material is 62.69 g:4.10 g:68.38 g:74.72 g:34.61 g:244.5 g; wherein x is 0.05, a is 0.5, b is 0, c is 0.3, d is 0, e is 0.2, b + c is 0.3, and d + e is 0.2.

[0142] [Example 6]

[0143] The preparation process of the lithium ion battery of Example 6 is basically the same as that of Example 1, except that, in Example 6, the mass ratio of lithium acetate, sodium acetate, nickel acetate, cobalt acetate, manganese acetate, and citric acid in the positive electrode active material is 56.09g:12.3g:68.38g:74.72g:34.61g:246.11g; wherein x is 0.15, a is 0.5, b is 0, c is 0.3, d is 0, e is 0.2, b+c is 0.3, and d+e is 0.2.

[0144] [Example 7]

[0145] The preparation process of the lithium ion battery of Example 7 is basically the same as that of Example 1, except that, in Example 7, the mass ratio of lithium acetate, sodium acetate, nickel acetate, ferric acetate, cobalt acetate, manganese acetate, and citric acid in the positive electrode active material is 56.09 g:12.3 g:68.38 g:19.09 g:49.82 g:34.61 g:240.29 g; wherein x is 0.15, a is 0.5, b is 0.1, c is 0.2, d is 0, e is 0.2, b + c is 0.3, and d + e is 0.2.

[0146] [Example 8]

[0147] The preparation process of the lithium ion battery of Example 8 is basically the same as that of Example 1, except that, in Example 8, the mass ratio of lithium acetate, sodium acetate, nickel acetate, ferric acetate, cobalt acetate, aluminum acetate, manganese acetate, and citric acid in the positive electrode active material is 56.09g:12.3g:68.38g:19.09g:49.82g:20.41g:17.3g:243.4g; wherein x is 0.15, a is 0.5, b is 0.1, c is 0.2, d is 0.1, e is 0.1, b+c is 0.3, and d+e is 0.2.

[0148] [Example 9]

[0149] The preparation process of the lithium ion battery of Example 9 is basically the same as that of Example 1, except that, in Example 9, the mass ratio of lithium acetate, sodium acetate, nickel acetate, cobalt acetate, manganese acetate, and citric acid in the positive electrode active material is 52.79 g: 16.41 g: 117.61 g: 14.94 g: 13.84 g: 215.6 g; wherein x is 0.2, a is 0.86, b is 0, c is 0.06, d is 0, e is 0.08, b + c is 0.06, and d + e is 0.08.

[0150] [Example 10]

[0151] The preparation process of the lithium ion battery of Example 10 is basically the same as that of Example 1, except that, in Example 10, the mass ratio of lithium acetate, sodium acetate, nickel acetate, cobalt acetate, manganese acetate, and citric acid in the positive electrode active material is 56.09 g:12.3 g:117.61 g:14.94 g:13.84 g:214.8 g; wherein x is 0.15, a is 0.86, b is 0, c is 0.06, d is 0, e is 0.08, b+c is 0.06, and d+e is 0.08.

[0152] [Example 11]

[0153] The preparation process of the lithium ion battery of Example 11 is basically the same as that of Example 1, except that, in Example 11, the mass ratio of lithium acetate, sodium acetate, nickel acetate, cobalt acetate, manganese acetate, and citric acid in the positive electrode active material is 59.39 g:8.2 g:68.38 g:74.72 g:34.61 g:213.99 g; wherein x is 0.1, a is 0.86, b is 0, c is 0.06, d is 0, e is 0.08, b+c is 0.06, and d+e is 0.08.

[0154] [Example 12]

[0155] The preparation process of the lithium ion battery of Example 12 is basically the same as that of Example 1, except that, in Example 12, the mass ratio of lithium acetate, sodium acetate, nickel acetate, cobalt acetate, manganese acetate, and citric acid in the positive electrode active material is 63.35g:3.28g:68.38g:74.72g:34.61g:213.03g; wherein x is 0.04, a is 0.86, b is 0, c is 0.06, d is 0, e is 0.08, b+c is 0.06, and d+e is 0.08.

[0156] [Example 13]

[0157] The preparation process of the lithium ion battery of Example 13 is basically the same as that of Example 1, except that, in Example 13, the mass ratio of lithium acetate, sodium acetate, nickel acetate, cobalt acetate, manganese acetate, and citric acid in the positive electrode active material is 63.35g:3.28g:134.02g:2.49g:1.73g:204.88g; wherein x is 0.04, a is 0.98, b is 0, c is 0.01, d is 0, e is 0.01, b+c is 0.01, and d+e is 0.01.

[0158] [Example 14]

[0159] The preparation process of the lithium ion battery of Example 14 is basically the same as that of Example 1, except that, in Example 14, the mass ratio of lithium acetate, sodium acetate, nickel acetate, cobalt acetate, manganese acetate, and citric acid in the positive electrode active material is 60.71 g:6.56 g:134.02 g:2.49 g:1.73 g:205.52 g; wherein x is 0.08, a is 0.98, b is 0, c is 0.01, d is 0, e is 0.01, b+c is 0.01, and d+e is 0.01.

[0160] [Comparative Example 1]

[0161] The preparation process of the lithium ion battery of Comparative Example 1 is basically the same as that of Example 1, except that, in Comparative Example 1, the mass ratio of lithium acetate, nickel acetate, cobalt acetate, manganese acetate, and citric acid in the positive electrode active material is 65.99 g: 68.38 g: 74.72 g: 34.61 g: 243.7 g; wherein x is 0, a is 0.5, b is 0, c is 0.3, d is 0, e is 0.2, b + c is 0.3, and d + e is 0.2.

[0162] [Comparative Example 2]

[0163] The preparation process of the lithium ion battery of Comparative Example 2 is basically the same as that of Example 1, except that, in Example 2, the mass ratio of lithium acetate, sodium acetate, nickel acetate, cobalt acetate, manganese acetate, and citric acid in the positive electrode active material is 33g:41.02g:68.38g:74.72g:34.61g:251.72g; wherein x is 0.5, a is 0.5, b is 0, c is 0.3, d is 0, e is 0.2, b+c is 0.3, and d+e is 0.2.

[0164] [Comparative Example 3]

[0165] The preparation process of the lithium ion battery of Comparative Example 3 is basically the same as that of Example 1, except that, in Comparative Example 3, the mass ratio of lithium acetate, nickel acetate, cobalt acetate, manganese acetate, and citric acid in the positive electrode active material is 65.99 g:117.61 g:14.94 g:13.84 g:212.39 g; wherein x is 0, a is 0.86, b is 0, c is 0.06, d is 0, e is 0.08, b + c is 0.3, and d + e is 0.08.

[0166] [Comparative Example 4]

[0167] The preparation process of the lithium ion battery of Comparative Example 4 is basically the same as that of Example 1, except that, in Comparative Example 4, the mass ratio of lithium acetate, nickel acetate, cobalt acetate, manganese acetate, and citric acid in the positive electrode active material is 65.99 g:134.02 g:2.49 g:1.73 g:204.24 g; wherein x is 0, a is 0.98, b is 0, c is 0.01, d is 0, e is 0.01, b + c is 0.01, and d + e is 0.01.

[0168] 2). Physical characterization

[0169] Li 1-x Na x Ni a Fe b Co c Al d Mn e Measurement of the content of each element in O2: After dissolving the positive electrode sheet containing only the active material in hydrogen peroxide solution, it can be tested by inductively coupled plasma spectrometer (ICP).

[0170] Table 1 Specific experimental parameters of Examples 1-14 and Comparative Examples 1-4

[0171] 3) Performance testing

[0172] 3.1) Material cost: Simply calculate the purchase cost of the raw materials. See Table 2 for the test results.

[0173] 3.2) Test of energy density of positive electrode active materials: At room temperature, lithium-ion batteries were subjected to cyclic charge and discharge tests using a blue-electric test system. The test process is as follows: the battery was charged at a rate of 0.1C to a voltage of 4.25V, left for 30 minutes, and then discharged at a rate of 0.1C to 2.8V; then charged at a rate of 0.33C to 4.25V, and charged at a constant voltage of 4.25V to a current ≤ 0.05C. After 30 minutes, it was discharged at a constant current rate of 0.33C to 2.8V. The capacity C and energy E at this time were recorded. The gram capacity and voltage platform were calculated based on gram capacity = C / W (where W is the weight of the positive electrode material in the battery) and voltage platform = E / C, respectively. The energy density of the positive electrode active material = gram capacity × voltage platform. The test results are shown in Table 2.

[0174] Table 2 Performance tests of Examples 1-14 and Comparative Examples 1-4

[0175] In the above embodiments and comparative examples, Examples 1-8 and Comparative Example 2 and Comparative Example 1 form a control group, Examples 9-12 and Comparative Example 3 form a control group, and Examples 13-14 and Comparative Example 4 form a control group.

[0176] The embodiments of this application use the cost reduction margin to measure the degree of cost reduction of the sodium-doped positive electrode active material, and the energy density reduction margin to measure the degree of energy density reduction of the sodium-doped positive electrode active material. The smaller the cost reduction margin, the smaller the material cost reduction, and the smaller the battery cost reduction; the smaller the energy density reduction margin, the smaller the impact on the material energy density, and the smaller the impact on the battery capacity density.

[0177] According to Examples 1-14 and Comparative Examples 1, 3, and 4, by replacing part of the lithium in the positive electrode active material with sodium, the energy density of the positive electrode active material can be kept relatively unchanged while the battery production cost can be reduced to a large extent.

[0178] According to Examples 1-14 and Comparative Example 2, by controlling the proportion of substituted sodium within 40%, the decrease in the energy density of the positive electrode active material can be reduced.

[0179] According to Examples 2-6 and 9-12, by setting 0.01≤x≤0.4 and x≤0.67-0.6a, the battery can further achieve both lower production cost and higher energy density.

[0180] According to Examples 4-6, 10-12 and 13-14, by setting x≤0.67-0.6a and 0.01≤x≤0.2, the impact on battery energy density can be reduced; further, by setting x≤0.67-0.6a and 0.05≤x≤0.15, the impact on battery energy density can be further reduced while reducing battery production costs.

[0181] According to Examples 6-8, a variety of positive electrode active materials are applicable to the technical solution of the present application, and replacing part of cobalt and manganese with iron and aluminum can further reduce the production cost of the battery.

[0182] 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 positive electrode active material, characterized in that: include: Li 1-x So x Ni a M1 b Co c M2 d Mr e O2; Among them, M1 includes Fe, M2 includes Al, 0.01≤x≤0.4, 0.5≤a≤0.98, 0≤b≤0.3, 0≤c≤0.3, 0≤d≤0.1, 0≤e≤0.45, a+b+c+d+e=1.

2. The positive electrode active material according to claim 1, characterized in that At a voltage of 4.25 V, the x and the a satisfy: x≤0.67-0.6a.

3. The positive electrode active material according to claim 1 or 2, characterized in that: 0.01≤x≤0.2。 4. The positive electrode active material according to any one of claims 1 to 3, characterized in that 0.05≤x≤0.15。 5. The positive electrode active material according to any one of claims 1 to 4, characterized in that The b and the c satisfy: 0.01≤b+c≤0.

3.

6. The positive electrode active material according to any one of claims 1 to 5, characterized in that The d and the e satisfy: 0.01≤d+e≤0.

45.

7. A preparation method for preparing the positive electrode active material according to any one of claims 1 to 6, characterized in that: include: Dissolving a lithium source, a sodium source, a nickel source, an iron source, a cobalt source, an aluminum source, and a manganese source in a solution of deionized water containing citric acid to obtain a mixed solution, wherein the ratio of the mass of the lithium source, the sodium source, the nickel source, the iron source, the cobalt source, the aluminum source, and the manganese source to the mass of the citric acid is 1:1; The mixed solution is stirred and dried to obtain a positive electrode active material precursor; Sintering the positive electrode active material precursor to obtain the positive electrode active material; Wherein, the positive electrode active material includes Li 1-x Na x Ni a M1 b Co c M2 d Mn e O2, M1 includes Fe, M2 includes Al, 0.01≤x≤0.4, 0.5≤a≤0.98, 0≤b≤0.3, 0≤c≤0.3, 0≤d≤0.1, 0≤e≤0.45, a+b+c+d+e=1.

8. The preparation method according to claim 7, characterized in that: The method of obtaining a positive electrode active material precursor by stirring and drying the mixed solution comprises: Stirring the mixed solution at 60° C. until a solid gel is formed; The solid gel was placed in an atmosphere of 100° C. and an atmosphere of 400° C. for drying for 12 h and 4 h, respectively, to obtain the positive electrode active material precursor.

9. The preparation method according to claim 7 or 8, characterized in that: The method of subjecting the positive electrode active material precursor to sintering treatment to obtain the positive electrode active material comprises: The positive electrode active material precursor was calcined at 750° C. in an oxygen atmosphere for 20 hours to obtain the positive electrode active material.

10. A positive electrode sheet, characterized in that: include: A positive electrode current collector, and a positive electrode film layer disposed on at least one side of the positive electrode current collector; The positive electrode film layer comprises the positive electrode active material according to any one of claims 1 to 6, or the positive electrode active material prepared by the method for preparing a positive electrode active material according to any one of claims 7 to 9.

11. A battery cell, characterized in that: Including the positive electrode sheet as described in claim 10.

12. A battery, characterized in that: Comprising the battery cell according to claim 11.

13. An electrical device, characterized in that: Comprising the battery as claimed in claim 12.

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