Positive electrode active material composition, positive electrode sheet, secondary battery, battery module, battery pack, and power using device

Abstract

The application provides a positive electrode active material composition, a positive electrode sheet, a secondary battery, a battery module, a battery pack, and a power utilization device. In particular, the application provides a positive electrode active material composition including a positive electrode active material and a dispersant. The positive electrode active material composition of the application can improve the poor dispersibility of the positive electrode active material powder and the large viscosity of the slurry in the positive electrode slurry preparation process, and further improve the flexibility of the positive electrode sheet.

Description

Technical Field

[0001] This application relates to the field of battery technology, and in particular to a positive electrode active material composition, a positive electrode sheet, a secondary battery, a battery module, a battery pack, and an electrical device. Background Technology

[0002] Secondary batteries are widely used in various fields such as new energy vehicles and energy storage power stations due to their advantages such as high energy density, long service life, and energy saving and environmental protection. The positive electrode of a secondary battery mainly consists of a current collector and an electrode film layer containing positive electrode active material. The positive electrode active material can be combined with a dispersion medium to form a positive electrode slurry, which is then coated onto the electrode current collector to form the positive electrode sheet.

[0003] Positive electrode active materials are usually used in the form of powder. Due to the large specific surface area and numerous small particles of positive electrode material powder, it is difficult to disperse the powder during the preparation of positive electrode slurry. The slurry has high viscosity and it is difficult to increase the solid content. As a result, defects such as cracking, delamination, uneven weight, particle scratches or pinholes are prone to occur during electrode coating. Summary of the Invention

[0004] This application was made in view of the above-mentioned problems, and one of its objectives is to provide a composition comprising a positive electrode active material and a flexible dispersant to improve the problems of poor dispersibility of positive electrode active material powder and high viscosity of slurry during the preparation of positive electrode slurry.

[0005] To achieve the above objectives, this application provides a positive electrode active material composition, a positive electrode sheet, a secondary battery, a battery module containing the secondary battery, a battery pack containing the battery module, and an electrical device containing the secondary battery, battery module, or battery pack.

[0006] A first aspect of this application provides a positive electrode active material composition, comprising a positive electrode active material and a dispersant, wherein...

[0007] The positive electrode active material has the chemical formula Li a A x Mn 1-y B y P 1-z C z O 4-n D nA comprises one or more elements selected from Zn, Al, Na, K, Mg, Nb, Mo, and W; B comprises one or more elements selected from Ti, V, Zr, Fe, Ni, Mg, Co, Ga, Sn, Sb, Nb, and Ge; C comprises one or more elements selected from B (boron), S, Si, and N; D comprises one or more elements selected from S, F, Cl, and Br; a is selected from the range of 0.9 to 1.1; x is selected from the range of 0.001 to 0.1; y is selected from the range of 0.001 to 0.5; z is selected from the range of 0.001 to 0.1; n is selected from the range of 0.001 to 0.1; and the positive electrode active material is electrically neutral.

[0008] The dispersant comprises a polymer, and the polymer comprises:

[0009] Equation 1 represents the first single-unit cell;

[0010] A second monomer unit selected from at least one of the monomer units represented by Formula 2 and the monomer units represented by Formula 3; and

[0011] A third monomer unit selected from at least one of the monomer units represented by Formula 4 and the monomer units represented by Formula 5.

[0012]

[0013] In some embodiments, the mass percentage of the first monomer unit is M1, which is 10% to 55% and optionally 25% to 55% based on the total mass of the polymer.

[0014] In some embodiments, the mass percentage of the second monomer unit is M2, which is 40% to 80%, and optionally 50% to 70%, based on the total mass of the polymer.

[0015] In some embodiments, the mass percentage of the third monomer unit is M3, which is 0% to 10% and optionally 0.001% to 2%, based on the total mass of the polymer.

[0016] In some implementations, M3 / (M2+M3) is 0% to 5%, and optionally 0.001% to 1%.

[0017] In some embodiments, the polymer is hydrogenated nitrile butadiene rubber.

[0018] In some embodiments, the weight-average molecular weight of the polymer is 50,000 to 500,000, and optionally 150,000 to 350,000.

[0019] In some embodiments, the mass percentage of the dispersant is X1, which is 0.05% to 1%, and optionally 0.1% to 0.5%, based on the total mass of the positive electrode active material.

[0020] In some embodiments, the positive electrode active material composition further includes a wetting agent having a surface tension of 20 mN / m to 40 mN / m, and the molecular structure of the wetting agent includes at least one of the following functional groups: -CN, -NH2, -NH-, N-, -OH, -C=O, -COO-, -C(=O)-OC(=O)-.

[0021] In some embodiments, the wetting agent includes one or more selected from small molecule organic solvents and low molecular weight polymers.

[0022] The small molecule organic solvent includes one or more selected from alkanolamines, alcohols, and nitriles. Optionally, the alkanolamines have 1 to 16 carbon atoms, or 2 to 6.

[0023] The low molecular weight polymer includes one or more selected from maleic anhydride-styrene copolymer, polyvinylpyrrolidone, polysiloxane, etc. Optionally, the weight average molecular weight of the low molecular weight polymer is below 6000, and optionally is 3000 to 6000.

[0024] In some embodiments, the mass percentage of the wetting agent is X2, which is 0.05% to 2%, and optionally 0.2% to 0.8%, based on the total mass of the positive electrode active material.

[0025] In some implementations, X1 / X2 is 0.05 to 20, optionally 0.1 to 1, and further 0.3 to 0.8.

[0026] In some implementations, A, C, and D are each independently any one of the elements within their respective ranges, and B is at least two elements within its range.

[0027] In some implementations, A is an element selected from Mg and Nb.

[0028] In some embodiments, B is at least two elements selected from Fe, Ti, V, Co and Mg, and optionally Fe and one or more elements selected from Ti, V, Co and Mg.

[0029] In some implementations, C stands for S.

[0030] In some implementations, D stands for F.

[0031] In some implementations, x is selected from the range of 0.001 to 0.005.

[0032] In some implementations, y is selected from the range of 0.01 to 0.5, and optionally from the range of 0.25 to 0.5.

[0033] In some implementations, z is selected from the range of 0.001 to 0.005.

[0034] In some implementations, n is selected from the range of 0.001 to 0.005.

[0035] In some implementations, (1-y):y is in the range of 1 to 4, optionally in the range of 1.5 to 3, and a:x is in the range of 9 to 1100, optionally in the range of 190 to 998.

[0036] In some embodiments, the lattice change rate of the positive electrode active material is less than 8%, and optionally less than 4%.

[0037] In some embodiments, the Li / Mn antisite defect concentration of the positive electrode active material is less than 2%, and optionally less than 0.5%.

[0038] In some embodiments, the surface oxygen valence state of the positive electrode active material is below -1.82, and optionally between -1.89 and -1.98.

[0039] In some embodiments, the compaction density of the positive electrode active material at 3T is 2.0 g / cm³. 3 The above is an option, specifically 2.2 g / cm³. 3 above.

[0040] In some embodiments, the surface of the positive electrode active material is coated with a carbon material.

[0041] The second aspect of this application provides a positive electrode slurry, including the positive electrode active material composition of the first aspect of this application; optionally, it also includes one or more of a solvent, a positive electrode conductive agent, and a positive electrode binder.

[0042] In some embodiments, the solvent includes N-methylpyrrolidone (NMP).

[0043] In some embodiments, the positive electrode binder includes one or more selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resins.

[0044] In some embodiments, the positive electrode conductive agent includes one or more selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0045] In some embodiments, the solid content of the positive electrode slurry is 40% to 70%, optionally 55% to 65%.

[0046] In some embodiments, the viscosity of the positive electrode slurry at 20°C is 3000 mPa·s to 50000 mPa·s, optionally 10000 mPa·s to 20000 mPa·s.

[0047] A third aspect of this application provides a positive electrode sheet, including a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector, wherein the positive electrode film layer comprises a positive electrode active material composition of the first aspect of this application, or is formed by coating a positive electrode slurry of the second aspect of this application.

[0048] Optionally, the coating method is selected from dip coating, film coating, electrostatic spraying and spin coating.

[0049] In some implementations, the total mass of the positive electrode film is used as the basis for measurement.

[0050] The positive electrode active material has a mass percentage content of W1, which is 90% to 99.5%, optionally 95% to 99%; and / or,

[0051] In some embodiments, the dispersant has a mass percentage content of W2, which is less than 1%, optionally 0.1% to 0.5%; and / or,

[0052] In some embodiments, the wetting agent has a mass percentage content of W3, where W3 is less than 2%, optionally 0.1% to 0.5%; and / or,

[0053] In some embodiments, the positive electrode binder has a mass percentage content of W4, which is less than 5.5%, optionally 1% to 3%; and / or,

[0054] In some embodiments, the positive electrode conductive agent has a mass percentage content of W5, which is less than 2.5%, and optionally 0.1% to 1%.

[0055] The fourth aspect of this application provides a secondary battery, and the positive electrode of the third aspect of this application.

[0056] The fifth aspect of this application provides a battery module, including the positive electrode of the third aspect of this application or the secondary battery of the fourth aspect of this application.

[0057] The sixth aspect of this application provides a battery pack, including the positive electrode of the third aspect of this application, the secondary battery of the fourth aspect of this application, or the battery module of the fifth aspect of this application.

[0058] The seventh aspect of this application provides an electrical device, including the positive electrode of the third aspect of this application, or the secondary battery of the fourth aspect of this application, or the battery module of the fifth aspect of this application, or the battery pack of the sixth aspect of this application.

[0059] The positive electrode active material composition provided in this application can solve the problems of poor dispersibility of positive electrode active material powder and high viscosity of slurry during the preparation of positive electrode slurry, thereby improving the processing performance of positive electrode slurry and the performance of secondary battery. Attached Figure Description

[0060] Figure 1 The measuring apparatus and measuring principle of the platinum plate method are illustrated by way of example.

[0061] Figure 2 This is a schematic diagram of a secondary battery according to one embodiment of this application.

[0062] Figure 3 yes Figure 2 An exploded view of a secondary battery according to one embodiment of this application is shown.

[0063] Figure 4 This is a schematic diagram of a battery module according to one embodiment of this application.

[0064] Figure 5 This is a schematic diagram of a battery pack according to one embodiment of this application.

[0065] Figure 6 yes Figure 5 An exploded view of a battery pack according to one embodiment of this application is shown.

[0066] Figure 7 This is a schematic diagram of an electrical device that uses a secondary battery as a power source according to one embodiment of this application.

[0067] Explanation of reference numerals in the attached figures:

[0068] 1 Battery pack; 2 Upper housing; 3 Lower housing; 4 Battery module; 5 Secondary battery; 51 Casing; 52 Electrode assembly; 53 Top cover assembly

[0069] Figure 8 The instruments and testing procedures used for testing the viscosity of the cathode slurry in the embodiments of this application are illustrated by way of example.

[0070] Figure 9 The folding method of the filter screen in the slurry filtration performance test of the present application is illustrated by way of example. Detailed Implementation

[0071] The embodiments of this application will be described in further detail below with reference to the examples. The detailed description of the following embodiments is used to illustrate the principles of this application, but should not be used to limit the scope of this application, that is, this application is not limited to the described embodiments.

[0072] The following detailed description discloses embodiments of the positive electrode active material composition, positive electrode sheet, secondary battery, battery module, battery pack, and electrical device of this application. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of actually identical structures may be omitted. This is to avoid making the following description unnecessarily lengthy and to facilitate understanding by those skilled in the art.

[0073] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60–120 and 80–110 are listed for a specific parameter, it is understood that ranges of 60–110 and 80–120 are also expected. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1–3, 1–4, 1–5, 2–3, 2–4, and 2–5. In this application, unless otherwise stated, the numerical range "a–b" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0~5" indicates that all real numbers between "0~5" have been listed in this article; "0~5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0074] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0075] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0076] Unless otherwise specified, all steps in this 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 it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0077] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0078] Unless otherwise specified, the term "or" is inclusive in this application. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, the condition "A or B" is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0079] It should be noted that, in this document, the median particle size Dv50 refers to the particle size corresponding to a cumulative volume distribution percentage of 50% for the positive electrode active material. In this application, the median particle size Dv50 of the positive electrode active material can be determined using laser diffraction particle size analysis. For example, it can be determined using a laser particle size analyzer (e.g., MalvemMaster Size 3000) in accordance with standard GB / T 19077-2016.

[0080] In this document, the term "cladding layer" refers to a layer of material covering the core, which may completely or partially cover the core. The use of "cladding layer" is for ease of description only and is not intended to limit the invention. Similarly, the term "thickness of cladding layer" refers to the thickness of the layer of material covering the core in the radial direction of the core.

[0081] In this document, the term "source" refers to a compound that is the source of a certain element. For example, the types of "sources" include, but are not limited to, carbonates, sulfates, nitrates, elements, halides, oxides, and hydroxides.

[0082] [Positive Electrode Active Material Composition]

[0083] A first aspect of this application provides a positive electrode active material composition, comprising a positive electrode active material and a dispersant, wherein...

[0084] The positive electrode active material has the chemical formula Li a A x Mn 1-y B y P 1-z C z O 4-n D n A comprises one or more elements selected from Zn, Al, Na, K, Mg, Nb, Mo, and W; B comprises one or more elements selected from Ti, V, Zr, Fe, Ni, Mg, Co, Ga, Sn, Sb, Nb, and Ge; C comprises one or more elements selected from B (boron), S, Si, and N; D comprises one or more elements selected from S, F, Cl, and Br; a is selected from the range of 0.9 to 1.1; x is selected from the range of 0.001 to 0.1; y is selected from the range of 0.001 to 0.5; z is selected from the range of 0.001 to 0.1; n is selected from the range of 0.001 to 0.1; and the positive electrode active material is electrically neutral.

[0085] The dispersant comprises a polymer, and the polymer comprises:

[0086] Equation 1 represents the first single-unit cell;

[0087] A second monomer unit selected from at least one of the monomer units represented by Formula 2 and the monomer units represented by Formula 3; and

[0088] A third monomer unit selected from at least one of the monomer units represented by Formula 4 and the monomer units represented by Formula 5.

[0089]

[0090]

[0091] The inventors discovered that the ratio between the first, second, and third monomer units may affect the dispersion effect of the dispersant, thereby affecting the flowability, viscosity, and filtration performance of the cathode slurry, and may also affect the battery performance.

[0092] In some embodiments, the mass percentage of the first monomer unit is M1, based on the total mass of the polymer, and M1 is 10% to 55% (e.g., 10%, 15%, 20%, 25%, 30%, 32%, 35%, 40%, 45%, 50%, or 55%), optionally 25% to 55%. The mass percentage of M1 affects the solubility of the polymer and the brittleness of the electrode. If the mass percentage of M1 exceeds 55%, it may result in poor dispersibility and / or poor electrode brittleness. If the mass percentage of M1 is less than 10%, the polymer becomes less soluble in solvents (e.g., NMP), resulting in an uneven slurry.

[0093] In some embodiments, based on the total mass of the polymer, the mass percentage of the second monomer unit is M2, which is 40% to 80% (e.g., 40%, 45%, 50%, 55%, 58%, 60%, 64%, 65%, 68%, 70%, 71%, 75%, or 80%), optionally 50% to 70%. The mass percentage of M2 affects the swelling of the polymer, and a mass percentage of M2 in the range of 40% to 80% can ensure the weak polarity of the polymer, thus better serving as a dispersant.

[0094] In some embodiments, the mass percentage of the third monomer unit is M3, based on the total mass of the polymer. M3 is 0% to 10% (e.g., 0.001%, 0.005%, 0.01%, 0.05%, 0.1%, 0.3%, 0.4%, 0.5%, 1%, 1.3%, 1.8%, 2%, 3%, 3.8%, 4%, 5%, 5.2%, 6%, 7%, 8%, 9%, or 10%), optionally 0.001% to 2%. The mass percentage of M3 affects the solubility of the polymer and its adhesion to the positive electrode current collector (e.g., aluminum foil). If the proportion of M3 is too low, the slurry adhesion is poor; if the mass percentage of M3 is too high, the polymer is easily dissolved in the electrolyte, affecting battery performance.

[0095] In some implementations, M3 / (M2+M3) is 0% to 5% (e.g., 0.001%, 0.005%, 0.01%, 0.05%, 0.1%, 0.5%, 1%, 2%, 3%, 4%, or 5%), and optionally 0.001% to 1%.

[0096] In some embodiments, the polymer is a random copolymer.

[0097] In some embodiments, the polymer is hydrogenated nitrile butadiene rubber.

[0098] Nitrile butadiene rubber (NBR) is a random copolymer formed by the polymerization (e.g., emulsion polymerization) of acrylonitrile and butadiene monomers, with the following general structural formula:

[0099]

[0100] In nitrile rubber (NBR), the linkages of butadiene (B) and acrylonitrile (A) units are generally BAB, BBA, or ABB, ABA, and BBB ternary groups. However, with increasing acrylonitrile content, AABAA pentad linkages are also observed, and it can even become the bulk polymer of acrylonitrile. In NBR, the sequence distribution of butadiene is predominantly trans-1,4-structure, and its microstructure is related to polymerization conditions. Higher polymerization temperatures decrease trans-1,4-structures and increase cis-1,4- and 1,2-structures.

[0101] Hydrogenated nitrile butadiene rubber (HNBR) is a product obtained by hydrogenating the carbon-carbon double bonds in the molecular chain of nitrile butadiene rubber; hence, it is also called highly saturated nitrile butadiene rubber. The chemical formula of hydrogenated nitrile butadiene rubber is as follows:

[0102]

[0103] There are three main methods for preparing HNBR: ethylene-acrylonitrile copolymerization, NBR solution hydrogenation, and NBR emulsion hydrogenation.

[0104] Because hydrogenated nitrile rubber has weak polarity and good affinity with carbon-containing materials, it can act on the particle surface of positive electrode active materials (especially carbon-containing positive electrode active materials), preventing particle agglomeration through steric hindrance. At the same time, hydrogenated nitrile rubber also has high strength and low glass transition temperature, which can improve the flexibility of the electrode sheet.

[0105] In some embodiments, the weight-average molecular weight of the polymer is 50,000 to 500,000 (e.g., 50,000, 60,000, 70,000, 80,000, 90,000, 100,000, 150,000, 200,000, 250,000, 300,000, 350,000, 400,000, 450,000, or 500,000), optionally 150,000 to 350,000. When the polymer molecular weight is below 50,000, the slurry has poor film-forming properties and exhibits a viscoelastic state in the positive electrode, making it prone to sticking to the rollers during cold pressing; while when the polymer molecular weight is high, the polymer's solubility deteriorates, which is not conducive to the dispersion of the slurry.

[0106] Hydrogenated nitrile rubber, a dispersant, exhibits significant absorption and swelling in the electrolyte. Excessive addition may affect the direct current resistance (DCR) at room temperature. In some embodiments, the mass percentage of the dispersant is X1, based on the total mass of the positive electrode active material. X1 is 0.05% to 1% (e.g., 0.05%, 0.1%, 0.2%, 0.25%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, or 1%), optionally 0.1% to 0.5%. When X1 is 0.05% to 1%, it achieves good dispersion while avoiding excessive addition of dispersant that could affect the DCR at room temperature and thus the energy density of the battery.

[0107] In some cases, the wettability of positive electrode active materials in NMP (N-methylpyrrolidone) is poor, resulting in poor slurry stability, manifested as low slurry solid content, decreased viscosity after standing, and ultimately, inability to be used normally. The inventors discovered that functional groups containing N groups (such as -CN / -NH2- / -N-, etc.), oxygen groups (such as -C=O / -COOH / -COOR / epoxy, etc.), or benzene rings have good affinity for positive electrode active materials (especially those with a highly graphitized carbon coating and microporous structure). Small molecule wetting agents containing these functional groups can effectively improve the wettability of positive electrode active materials in solvents (such as N-methylpyrrolidone).

[0108] In some embodiments, the positive electrode active material composition further includes a wetting agent having a surface tension of 20 mN / m to 40 mN / m, and the molecular structure of the wetting agent includes at least one (e.g., two or more) of the following functional groups: -CN, -NH2, -NH-, -N-, -OH, -C=O, -COO-, -C(=O)-OC(=O)-, epoxy group, phenyl. The surface tension of the wetting agent can be obtained using a surface tension meter according to existing measurement methods in the art.

[0109] An exemplary measurement method is the platinum plate method, which works as follows: When the sensing platinum plate is immersed in the liquid being measured, the surface tension around the platinum plate pulls it downwards as much as possible. When the liquid surface tension and other related forces reach equilibrium with the balancing forces, the sensing platinum plate stops immersing itself in the liquid. At this point, the instrument's balance sensor measures the immersion depth and converts it into the liquid's surface tension value.

[0110] In the specific testing process, the test steps of the platinum plate method are as follows: (1) gradually immerse the platinum plate into the liquid; (2) when immersed in the liquid surface, the balance value is sensed by the sensor; (3) convert the sensed balance value into a surface tension value and display it.

[0111] The formula for calculating surface tension is as follows:

[0112] P=mg+Lγ·cosθ-shρg

[0113] Balance force = Weight of platinum plate + Total surface tension - Buoyancy force on platinum plate

[0114] (Up) (Down) (Up)

[0115] m: Weight of the platinum plate

[0116] g: gravity (9.8 N / kg)

[0117] L: Perimeter of the platinum plate

[0118] γ: Surface tension of the liquid

[0119] θ: Contact angle between the liquid and the platinum plate

[0120] s: Cross-sectional area of ​​platinum plate

[0121] h: Depth of platinum plate immersion

[0122] ρ: density of the liquid

[0123] Figure 1 The measuring apparatus and measuring principle of the platinum plate method are illustrated by way of example.

[0124] In some embodiments, the wetting agent includes one or more selected from small molecule organic solvents and low molecular weight polymers.

[0125] The small molecule organic solvent includes one or more selected from alkanolamines, alcohols, and nitriles. Optionally, the alkanolamines have 1 to 16 carbon atoms, or 2 to 6; for example, isopropanolamine and 2-amino-2-methyl-1-propanol.

[0126] The low molecular weight polymer includes one or more selected from maleic anhydride-styrene copolymer, polyvinylpyrrolidone, and polysiloxane. Optionally, the weight average molecular weight of the low molecular weight polymer is below 6000, for example, 70 to 6000 (e.g., 70 to 100, 100 to 500, 500 to 1000, 1000 to 2000, 2000 to 3000, 3000 to 4000, 4000 to 5000, or 5000 to 6000), and optionally 3000 to 6000.

[0127] In some embodiments, the mass percentage of the wetting agent is X2 based on the total mass of the positive electrode active material, where X2 is 0.05% to 2% (e.g., 0.05%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, or 2%), optionally 0.2% to 0.8%. When X2 is 0.05% to 2%, it can achieve a good wetting effect while avoiding excessive addition of wetting agent, which could affect the stability of the positive electrode or electrolyte or the performance of the battery (e.g., cycle performance).

[0128] In some embodiments, X1 / X2 is 0.05–20 (e.g., 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2, 3, 4, 5, 10, 15, or 20), optionally 0.1–1, and more preferably 0.3–0.8. When the ratio of dispersant to wetting agent is within the above range, the positive electrode slurry has a lower viscosity and better flowability and filterability.

[0129] Regarding positive electrode active materials, the inventors of this application have repeatedly studied the effects of doping various elements at the Li, Mn, P and O sites of lithium manganese phosphate. They found that by simultaneously doping specific elements at specific amounts at the above four sites, significantly improved rate performance, improved cycle performance and / or high-temperature stability can be obtained, thereby obtaining an improved lithium manganese phosphate positive electrode active material.

[0130] The positive electrode active material of this application is obtained by elemental doping of the compound LiMnPO4, wherein A, B, C, and D are the elements doped at the Li, Mn, P, and O sites of the compound LiMnPO4, respectively. Not wishing to be confined to theory, it is now believed that the performance improvement of lithium manganese phosphate is related to reducing the lattice change rate of lithium manganese phosphate during lithium insertion / extraction and reducing surface activity. Reducing the lattice change rate can reduce the difference in lattice constants between the two phases at the grain boundary, reduce interfacial stress, and enhance Li... + The ability to transport substances at the interface improves the rate performance of the positive electrode active material. However, high surface activity can easily lead to severe interfacial side reactions, exacerbating gas generation, electrolyte consumption, and interface damage, thus affecting the battery's cycle performance. In this application, lattice change rate is reduced through Li and Mn doping. Mn doping also effectively reduces surface activity, thereby suppressing Mn dissolution and interfacial side reactions between the positive electrode active material and the electrolyte. P-site doping accelerates the change rate of Mn-O bond length, lowering the small polaron migration barrier and thus improving electronic conductivity. O-site doping has a good effect on reducing interfacial side reactions. P-site and O-site doping also affect the dissolution of Mn from antisite defects and the kinetic properties. Therefore, doping reduces the concentration of antisite defects in the material, improves the kinetic properties and specific capacity, and can also change the particle morphology, thereby increasing the compaction density. The applicant unexpectedly discovered that by simultaneously doping specific elements at specific amounts at the Li, Mn, P, and O sites of the compound LiMnPO4, it is possible to obtain significantly improved rate performance, while significantly reducing the dissolution of Mn and Mn-site dopants, resulting in significantly improved cycle performance and / or high-temperature stability, and also improving the specific capacity and compaction density of the material.

[0131] Optionally, A is one or more elements selected from Zn, Al, Na, K, Mg, Nb, Mo, and W; B is one or more elements selected from Ti, V, Zr, Fe, Ni, Mg, Co, Ga, Sn, Sb, Nb, and Ge; C is one or more elements selected from B (boron), S, Si, and N; and D is one or more elements selected from S, F, Cl, and Br.

[0132] In some implementations, A, C, and D are each independently any one of the elements within their respective ranges, and B is at least two elements within its range.

[0133] In some implementations, A is an element selected from Mg and Nb.

[0134] In some embodiments, B is at least two elements selected from Fe, Ti, V, Co and Mg, and optionally Fe and one or more elements selected from Ti, V, Co and Mg.

[0135] In some implementations, C stands for S.

[0136] In some implementations, D stands for F.

[0137] By selecting doping elements at the Li sites within the aforementioned range, the lattice change rate during the lithium removal process can be further reduced, thereby further improving the rate performance of the battery. By selecting doping elements at the Mn sites within the aforementioned range, electronic conductivity can be further increased and the lattice change rate further reduced, thereby improving the rate performance and specific capacity of the battery. By selecting doping elements at the P sites within the aforementioned range, the rate performance of the battery can be further improved. By selecting doping elements at the O sites within the aforementioned range, interfacial side reactions can be further mitigated, improving the high-temperature performance of the battery.

[0138] In some implementations, x is selected from the range of 0.001 to 0.005 (e.g., 0.001, 0.002, 0.003, 0.004, or 0.005).

[0139] In some implementations, y is selected from the range of 0.01 to 0.5 (e.g., 0.01, 0.02, 0.03, 0.04, 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, or 0.5), and optionally from the range of 0.25 to 0.5.

[0140] In some implementations, z is selected from the range of 0.001 to 0.005 (e.g., 0.001, 0.002, 0.003, 0.004, or 0.005).

[0141] In some implementations, n is selected from the range of 0.001 to 0.005 (e.g., 0.001, 0.002, 0.003, 0.004, or 0.005).

[0142] By selecting the y-value within the above range, the specific capacity and rate performance of the material can be further improved. By selecting the x-value within the above range, the kinetic performance of the material can be further improved. By selecting the z-value within the above range, the rate performance of the secondary battery can be further improved. By selecting the n-value within the above range, the high-temperature performance of the secondary battery can be further improved.

[0143] In some implementations, (1-y): y is in the range of 1 to 4 (e.g., 1, 1.5, 2, 2.5, 3, 3.5, or 4), optionally in the range of 1.5 to 3, and a:x is in the range of 9 to 1100 (e.g., 9–10, 10–20, 20–50, 50–100, 100–150, 150–190, 190–200, 200–300, 300–500, 500–700, 700–900, 900–998, 998–1000, or 1000–1100), optionally in the range of 190–998. Here, y represents the sum of the stoichiometric coefficients of the Mn-site dopants. When the above conditions are met, the energy density and cycle performance of the positive electrode active material can be further improved.

[0144] In some embodiments, the lattice change rate of the positive electrode active material is less than 8% (e.g., 0.001%, 0.005%, 0.01%, 0.05%, 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, or 8%), optionally less than 4%. Reducing the lattice change rate facilitates Li ion transport, meaning that Li ions have greater mobility in the material, which is beneficial for improving the rate performance of the secondary battery. The lattice change rate can be measured by methods known in the art, such as X-ray diffraction (XRD).

[0145] In some embodiments, the concentration of Li / Mn antisite defects in the positive electrode active material is below 2% (e.g., 0.001%, 0.005%, 0.01%, 0.05%, 0.1%, 0.5%, 1%, or 2%), optionally below 0.5%. The term Li / Mn antisite defect refers to the presence of Li in the LiMnPO4 lattice. + With Mn 2+ The positions of Li and Mn are interchanged. The Li / Mn antisite defect concentration refers to the concentration of Li / Mn antisite defects in the positive electrode active material. 2+ Interchangeable Li + Zhan Li + Percentage of the total. Mn of the inversion defect. 2+It will hinder Li + The transport of Li / Mn antisite defects, by reducing the concentration of Li / Mn antisite defects, is beneficial to improving the specific capacity and rate performance of the positive electrode active material. The concentration of Li / Mn antisite defects can be measured by methods known in the art, such as XRD.

[0146] In some embodiments, the surface oxygen valence state of the positive electrode active material is below -1.82 (e.g., -1.82, -1.85, -1.86, -1.89, -1.98, -1.97, -1.96, or -1.95), optionally between -1.89 and -1.98. By reducing the surface oxygen valence state, interfacial side reactions between the positive electrode active material and the electrolyte can be mitigated, thereby improving the cycle performance and high-temperature stability of the secondary battery. The surface oxygen valence state can be measured by methods known in the art, such as electron energy loss spectroscopy (EELS).

[0147] In some embodiments, the compaction density of the positive electrode active material at 3T is 2.0 g / cm³. 3 Above (e.g., 2.0 g / cm³) 3 2.1g / cm 3 2.2g / cm 3 2.3g / cm 3 2.4g / cm 3 Or 2.5g / cm 3 ), optionally 2.2 g / cm 3 The higher the compaction density, the greater the weight of the active material per unit volume; therefore, increasing the compaction density is beneficial for improving the volumetric energy density of the battery. Compaction density can be measured according to GB / T 24533-2009. In some embodiments, the surface of the positive electrode active material is coated with carbon material. This can improve the conductivity of the positive electrode active material.

[0148] In some embodiments, the positive electrode active material may be prepared by a method comprising the following steps:

[0149] Step (1): Dissolve and stir the manganese source, element B source and acid in a solvent to generate a suspension of manganese salt doped with element B. Filter the suspension and dry the filter cake to obtain manganese salt doped with element B.

[0150] Step (2): Add the lithium source, phosphorus source, source of element A, source of element C and source of element D, solvent and manganese salt doped with element B obtained in step (1) into the reaction vessel, grind and mix to obtain a slurry;

[0151] Step (3): Transfer the slurry obtained in step (2) to a spray drying equipment for spray drying and granulation to obtain granules;

[0152] Step (4): Sinter the particles obtained in step (3) to obtain the positive electrode active material.

[0153] In some embodiments, the stirring in step (1) is carried out at a temperature in the range of 60-120°C (e.g., 80°C).

[0154] In some embodiments, the stirring in step (1) is carried out at a stirring rate of 200-800 rpm (e.g., 600 rpm).

[0155] In some embodiments, the source of element A is selected from at least one of element A's elemental form, oxide, phosphate, oxalate, carbonate, and sulfate; the source of element B is selected from at least one of element B's elemental form, oxide, phosphate, oxalate, carbonate, and sulfate; the source of element C is selected from at least one of element C's sulfate, borate, nitrate, and silicate; and the source of element D is selected from at least one of element D's elemental form and ammonium salt.

[0156] In some implementations, the grinding and mixing in step (2) is carried out for 8-15 hours (e.g., 10 hours).

[0157] In some embodiments, the sintering of step (4) is carried out for 6-14 hours (e.g., 10 hours) in a temperature range of 600-900°C (e.g., 700°C).

[0158] [Positive electrode slurry]

[0159] The second aspect of this application provides a positive electrode slurry, including the positive electrode active material composition of the first aspect of this application; optionally, it also includes one or more of a solvent, a positive electrode conductive agent, and a positive electrode binder.

[0160] In some embodiments, the positive electrode slurry includes a solvent, optionally including N-methylpyrrolidone (NMP).

[0161] In some embodiments, the positive electrode slurry includes a positive electrode binder. Optionally, the positive electrode binder includes one or more selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resins.

[0162] In some embodiments, the positive electrode slurry includes a positive electrode conductive agent. Optionally, the positive electrode conductive agent includes one or more selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0163] In this application, by selecting appropriate dispersants and / or wetting agents, the solid content of the cathode slurry can be increased and / or the viscosity of the cathode slurry can be reduced.

[0164] In some embodiments, the solid content of the positive electrode slurry is 40% to 70% (e.g., 40%, 45%, 50%, 55%, 58%, 60%, 64%, 65%, 68%, or 70%), optionally 55% to 65%.

[0165] In some embodiments, the viscosity of the positive electrode slurry at 20°C is 3000 mPa·s to 50000 mPa·s (e.g., 3000 mPa·s, 4000 mPa·s, 5000 mPa·s, 6000 mPa·s, 7000 mPa·s, 8000 mPa·s, 9000 mPa·s, 10000 mPa·s, 11000 mPa·s, 12000 mPa·s). 13000mpa.s, 14000mpa.s, 15000mpa.s, 16000mpa.s, 17000mpa.s, 18000mpa.s, 19000mpa.s, 20000mpa.s, 30000mpa.s, 40000mpa.s or 50000mpa.s), optionally 10000mpa.s to 20000mpa.s.

[0166] [Positive electrode plate]

[0167] A third aspect of this application provides a positive electrode sheet, comprising a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector, wherein the positive electrode film layer comprises the positive electrode active material composition of the first aspect of this application, or is formed by coating the positive electrode slurry of the second aspect of this application. The positive electrode film layer may be disposed on one or both surfaces of the positive current collector.

[0168] In some implementations, the total mass of the positive electrode film is used as the basis for measurement.

[0169] The mass percentage of the positive electrode active material is W1, where W1 is 90% to 99.5% (e.g., 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 99.5%), optionally 95% to 99%; and / or,

[0170] In some embodiments, the dispersant has a mass percentage content of W2, which is less than 1% (e.g., 0.001%, 0.005%, 0.01%, 0.05%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, or 1%), optionally 0.1% to 0.5%; and / or,

[0171] In some embodiments, the wetting agent has a mass percentage content of W3, which is less than 2% (e.g., 0.001%, 0.005%, 0.01%, 0.05%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 1%, or 2%), optionally 0.1% to 0.5%; and / or,

[0172] In some embodiments, the positive electrode binder has a mass percentage content of W4, which is less than 5.5% (e.g., 0.001%, 0.005%, 0.01%, 0.05%, 0.1%, 0.5%, 1%, 1.2%, 1.5%, 2%, 2.3%, 2.5%, 2.7%, 3%, 4%, 5%, or 5.5%), optionally 1% to 3%; and / or,

[0173] In some embodiments, the mass percentage of the positive conductive agent is W5, which is less than 2.5% (e.g., 0.001%, 0.005%, 0.01%, 0.05%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 2%, or 2.5%), and optionally 0.1% to 1%.

[0174] In some embodiments, the positive current collector 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 substrate and a metal layer formed on at least one surface of the polymer substrate. 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 of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0175] In some embodiments, one or more undercoating layers are present between the positive current collector and the positive electrode film layer to increase the adhesion between them. In some embodiments, the undercoating layer comprises a polyacrylic acid-acrylate copolymer (e.g., a polyacrylic acid-acrylate copolymer with a weight average molecular weight of 300,000 to 350,000) and a conductive agent (e.g., conductive carbon black (Super P)), with a weight ratio of 60:40 to 40:60. An exemplary preparation method includes: dissolving / dispersing the polyacrylic acid-acrylate copolymer and the conductive agent in deionized water to prepare an undercoating slurry; coating the undercoating slurry onto one or both sides of the positive current collector (e.g., aluminum foil); and drying to obtain a positive current collector with a conductive undercoating. In some embodiments, the thickness of the undercoating layer is 1 to 5 μm.

[0176] In some embodiments, the positive electrode material layer may optionally include a binder. The type and amount of the conductive agent and binder are not specifically limited and can be selected according to actual needs. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0177] In some embodiments, the positive electrode material layer may optionally include a conductive agent. As an example, the conductive agent may include at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0178] In some embodiments, the positive electrode sheet can be prepared by dispersing the positive electrode active material, conductive agent, binder, and any other components in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry onto a positive electrode current collector, and then performing processes such as drying and cold pressing to obtain the positive electrode sheet. Optionally, the coating method is selected from dip coating, film coating, electrostatic spraying, and spin coating.

[0179] A fourth aspect of this application provides a secondary battery, including the positive electrode sheet of the third aspect of this application.

[0180] [Negative electrode plate]

[0181] In the secondary battery of this application, the negative electrode sheet may include a negative electrode current collector and a negative electrode material layer disposed on the negative electrode current collector and including a negative electrode active material. The negative electrode material layer may be disposed on one of the surfaces of the negative electrode current collector or on both surfaces of the negative electrode current collector.

[0182] 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 substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0183] In some embodiments, the negative electrode active material may be a negative electrode active material known in the art for use in batteries. As an example, the negative electrode active material may include at least one of the following materials: graphite (e.g., artificial graphite, natural graphite), soft carbon, hard carbon, mesophase carbon microspheres, carbon fibers, carbon nanotubes, silicon-based materials, tin-based materials, and lithium titanate, etc. The silicon-based material may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, this application is not limited to these materials, and other conventional 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.

[0184] In some embodiments, the negative electrode film layer may optionally 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).

[0185] In some embodiments, the negative electrode film may optionally include a conductive agent. The conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0186] In some implementations, the negative electrode material layer comprises the negative electrode active material artificial graphite, the conductive agent acetylene black, and the binder styrene-butadiene rubber (SBR).

[0187] In some embodiments, the negative electrode material layer may optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0188] In some embodiments, the negative electrode sheet can be prepared by dispersing the components used to prepare the negative electrode sheet, such as the negative electrode active material, conductive agent, binder and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto the negative electrode current collector, and then obtaining the negative electrode sheet after drying, cold pressing and other processes.

[0189] [Isolation membrane]

[0190] In the secondary battery of this application, a separator is disposed between the positive electrode and the negative electrode to provide isolation. The type of separator is not specifically limited; any known porous separator with good chemical and mechanical stability can be selected. In some embodiments, the separator material 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.

[0191] The secondary battery in this application can be a lithium-ion battery.

[0192] The secondary battery of this application can be prepared using conventional methods. In some embodiments, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding or stacking process. Exemplary preparation methods include:

[0193] Step 1: Stack the positive electrode, separator, and negative electrode in sequence, with the separator between the positive and negative electrodes, and then wind them to obtain the electrode assembly;

[0194] Step 2: Place the electrode assembly in the secondary battery casing, dry it, inject electrolyte, and then process it through formation and settling to obtain the secondary battery.

[0195] In some embodiments, the secondary battery of this application may include an outer packaging. The outer packaging may be used to encapsulate the aforementioned electrode assembly and electrolyte.

[0196] In some embodiments, the outer packaging of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging of the secondary battery can also be a soft pack, such as a pouch. The material of the soft pack can be plastic; examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0197] This application does not impose any particular limitation on the shape of the secondary battery; it can be cylindrical, square, or any other arbitrary shape. For example, Figure 6 This is an example of a square-structured secondary battery 5.

[0198] In some implementations, refer to Figure 7The outer packaging may include a housing 51 and a cover 53. The housing 51 may include a base plate and side plates connected to the base plate, the base plate and side plates forming a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover 53 can be placed over the opening to close the receiving cavity. A positive electrode, a negative electrode, and a separator can be formed into an electrode assembly 52 using a winding or stacking process. The electrode assembly 52 is encapsulated within the receiving cavity. Electrolyte is immersed in the electrode assembly 52. ​​The secondary battery 5 may contain one or more electrode assemblies 52, which can be selected by those skilled in the art according to specific practical needs.

[0199] In some implementations, the secondary batteries can be assembled into a battery module, and the number of secondary batteries contained in the battery module can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery module.

[0200] Figure 4 This is battery module 4, used as an example. (See reference...) Figure 4 In battery module 4, multiple secondary batteries 5 can be arranged sequentially along the length of battery module 4. Of course, they can also be arranged in any other manner. Furthermore, these multiple secondary batteries 5 can be fixed in place using fasteners.

[0201] Optionally, the battery module 4 may also include a housing with a receiving space in which a plurality of secondary batteries 5 are received.

[0202] In some embodiments, the battery modules described above can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0203] Figure 5 and Figure 6 This is battery pack 1 as an example. (See reference...) Figure 5 and Figure 6 The battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box includes an upper body 2 and a lower body 3, with the upper body 2 covering the lower body 3 to form a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0204] In addition, this application also provides an electrical device, which includes a secondary battery, battery module, or battery pack provided in this application. The secondary battery, battery module, or battery pack can be used as a power source for the electrical device, or as an energy storage unit for the electrical device. The electrical device can be selected from mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., 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 to these. The secondary battery, battery module, or battery pack can be selected as the electrical device according to its usage requirements.

[0205] Figure 7 This is an example of an electrical device. The device could be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of the secondary battery for this device, a battery pack or battery module can be used.

[0206] Another example device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use a rechargeable battery as their power source.

[0207] Example

[0208] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0209] Preparation of secondary batteries

[0210] Example 1

[0211] Preparation of positive electrode active materials

[0212] Preparation of doped manganese oxalate: 1.3 mol of MnSO4·H2O and 0.7 mol of FeSO4·H2O were thoroughly mixed in a mixer for 6 hours. The mixture was transferred to a reaction vessel, and 10 L of deionized water and 2 mol of oxalic acid dihydrate (calculated as oxalic acid) were added. The reaction vessel was heated to 80 °C and stirred at 600 rpm for 6 hours until the reaction was terminated (no more bubbles were generated), yielding an Fe-doped manganese oxalate suspension. The suspension was then filtered, and the filter cake was dried at 120 °C and then ground to obtain a median particle size Dv. 50 The particles are Fe-doped manganese oxalate particles with a diameter of approximately 100 nm.

[0213] Preparation of doped lithium manganese phosphate: 1 mol of the above-mentioned manganese oxalate particles, 0.497 mol of lithium carbonate, 0.001 mol of Mo(SO4)3, an 85% phosphoric acid aqueous solution containing 0.999 mol of phosphoric acid, 0.001 mol of H4SiO4, 0.0005 mol of NH4HF2, and 0.005 mol of sucrose were added to 20 L of deionized water. The mixture was transferred to a sand mill and thoroughly ground and stirred for 10 hours to obtain a slurry. The slurry was then transferred to a spray drying equipment for spray drying and granulation. The drying temperature was set at 250℃, and the granules were dried for 4 hours to obtain particles. Under a protective atmosphere of nitrogen (90 vol%) + hydrogen (10 vol%), the above powder was sintered at 700℃ for 10 hours to obtain carbon-coated Li. 0.994 Mo 0.001 Mn 0.65 Fe 0.35 P 0.999 Si 0.o01 O 3.999 F 0.001 The elemental content of positive electrode active materials can be detected using inductively coupled plasma atomic emission spectroscopy (ICP).

[0214] 2) Preparation of button cells

[0215] The above-mentioned positive electrode active material, polyvinylidene fluoride (PVDF), and acetylene black were added to N-methylpyrrolidone (NMP) in a weight ratio of 90:5:5, and stirred in a drying chamber to form a slurry. The slurry was then coated onto aluminum foil, dried, and cold-pressed to form a positive electrode sheet. The coating amount was 0.02 g / cm³. 2 The compacted density is 2.0 g / cm³. 3 .

[0216] A lithium sheet is used as the negative electrode, and a solution of 1 mol / L LiPF6 in ethylene carbonate (EC), diethyl carbonate (DEC) and dimethyl carbonate (DMC) in a volume ratio of 1:1:1 is used as the electrolyte. The lithium sheet and the positive electrode prepared above are assembled into a coin cell in a coin cell box to form a coin cell (hereinafter also referred to as "coin cell").

[0217] 3) Preparation of full cells

[0218] The above-mentioned positive electrode active material was mixed evenly with the conductive agent acetylene black and the binder polyvinylidene fluoride (PVDF) in an N-methylpyrrolidone solvent system at a weight ratio of 92:2.5:5.5. The mixture was then coated onto aluminum foil, dried, and cold-pressed to obtain the positive electrode sheet. The coating amount was 0.04 g / cm³. 2 The compacted density is 2.4 g / cm³. 3 .

[0219] Artificial graphite (anode active material), hard carbon, acetylene black (conductive agent), styrene-butadiene rubber (SBR) (binder), and sodium carboxymethyl cellulose (CMC) (thickener) were mixed evenly in deionized water at a weight ratio of 90:5:2:2:1. The mixture was then coated onto copper foil, dried, and cold-pressed to obtain the negative electrode sheet. The coating amount was 0.02 g / cm³. 2 The compacted density is 1.7 g / cm³. 3 .

[0220] Using a porous polyethylene (PE) polymer film as a separator, the positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrodes to provide isolation. The resulting bare battery is then wound up. The bare battery is placed in an outer package, injected with the same electrolyte as used in the preparation of the coin cell, and sealed to obtain a full battery (hereinafter also referred to as "full battery").

[0221] Example 2

[0222] Except for changing the amount of high-purity Li2CO3 to 0.4885 mol, replacing Mo(SO4)3 with MgSO4, changing the amount of FeSO4·H2O to 0.68 mol, adding 0.02 mol of Ti(SO4)2 when preparing doped manganese oxalate, and replacing H4SiO4 with HNO3 in “1) Preparation of positive electrode active material”, everything else is the same as in Example 1.

[0223] Example 3

[0224] Except for changing the amount of high-purity Li2CO3 to 0.496 mol, replacing Mo(SO4)3 with W(SO4)3, and replacing H4SiO4 with H2SO4 in “1) Preparation of positive electrode active material”, everything else is the same as in Example 1.

[0225] Example 4

[0226] Except for changing the amount of high-purity Li2CO3 to 0.4985 mol in “1) Preparation of positive electrode active material”, replacing 0.001 mol of Mo(SO4)3 with 0.0005 mol of Al2(SO4)3 and NH4HF2 with NH4HCl2, everything else is the same as in Example 1.

[0227] Example 5

[0228] Except for changing 0.7 mol FeSO4·H2O to 0.69 mol in “1) Preparation of positive electrode active material”, adding 0.01 mol VCl2 when preparing doped manganese oxalate, changing the amount of Li2CO3 to 0.4965 mol, replacing 0.001 mol Mo(SO4)3 with 0.0005 mol Nb2(SO4)5 and H4SiO4 with H2SO4, everything else is the same as in Example 1.

[0229] Example 6

[0230] Except for changing the amount of FeSO4·H2O to 0.68 mol in “1) Preparation of positive electrode active material”, adding 0.01 mol of VCl2 and 0.01 mol of MgSO4 when preparing doped manganese oxalate, changing the amount of Li2CO3 to 0.4965 mol, replacing 0.001 mol of Mo(SO4)3 with 0.0005 mol of Nb2(SO4)5 and H4SiO4 with H2SO4, everything else is the same as in Example 1.

[0231] Example 7

[0232] Except for replacing MgSO4 with CoSO4 in “1) Preparation of positive electrode active material”, everything else is the same as in Example 6.

[0233] Example 8

[0234] Except for replacing MgSO4 with NiSO4 in “1) Preparation of positive electrode active material”, everything else is the same as in Example 6.

[0235] Example 9

[0236] Except for changing the amount of FeSO4·H2O to 0.698 mol in “1) Preparation of positive electrode active material”, adding 0.002 mol of Ti(SO4)2 when preparing doped manganese oxalate, changing the amount of Li2CO3 to 0.4955 mol, replacing 0.001 mol of Mo(SO4)3 with 0.0005 mol of Nb2(SO4)5, replacing H4SiO4 with H2SO4, and preparing NH4HF2 into NH4HCl2, everything else is the same as in Example 1.

[0237] Example 10

[0238] Except for changing the amount of FeSO4·H2O to 0.68 mol in “1) Preparation of positive electrode active material”, adding 0.01 mol of VCl2 and 0.01 mol of MgSO4 when preparing doped manganese oxalate, changing the amount of Li2CO3 to 0.4975 mol, replacing 0.001 mol of Mo(SO4)3 with 0.0005 mol of Nb2(SO4)5 and NH4HF2 with NH4HBr2, everything else is the same as in Example 1.

[0239] Example 11

[0240] Except for changing the amount of FeSO4·H2O to 0.69 mol in “1) Preparation of positive electrode active material”, adding 0.01 mol of VCl2 when preparing doped manganese oxalate, changing the amount of Li2CO3 to 0.499 mol, replacing Mo(SO4)3 with MgSO4 and NH4HF2 with NH4HBr2, everything else is the same as in Example 1.

[0241] Example 12

[0242] Except for the following changes in “1) Preparation of positive electrode active material”, where the amount of MnSO4·H2O is changed to 1.36 mol, the amount of FeSO4·H2O is changed to 0.6 mol, 0.04 mol of VCl2 is added when preparing doped manganese oxalate, the amount of Li2CO3 is changed to 0.4985 mol, Mo(SO4)3 is replaced with MgSO4 and H4SiO4 is replaced with HNO3, the rest is the same as in Example 1.

[0243] Example 13

[0244] Except for changing the amount of MnSO4·H2O to 1.16 mol and the amount of FeSO4·H2O to 0.8 mol in “1) Preparation of positive electrode active material”, the rest is the same as in Example 12.

[0245] Example 14

[0246] Except for changing the amount of MnSO4·H2O to 1.3 mol and the amount of VCl2 to 0.1 mol in “1) Preparation of positive electrode active material”, the rest is the same as in Example 12.

[0247] Example 15

[0248] Except for changing the amount of MnSO4·H2O to 1.2 mol in “1) Preparation of positive electrode active material”, adding 0.1 mol of VCl2 when preparing doped manganese oxalate, changing the amount of Li2CO3 to 0.494 mol, replacing 0.001 mol of Mo(SO4)3 with 0.005 mol of MgSO4 and H4SiO4 with H2SO4, everything else is the same as in Example 1.

[0249] Example 16

[0250] Except for changing the amount of MnSO4·H2O to 1.2 mol in “1) Preparation of positive electrode active material”, adding 0.1 mol of VCl2 when preparing doped manganese oxalate, changing the amount of Li2CO3 to 0.467 mol, replacing 0.001 mol of Mo(SO4)3 with 0.005 mol of MgSO4, replacing 0.001 mol of H4SiO4 with 0.005 mol of H2SO4, and replacing 1.175 mol of 85% phosphoric acid with 1.171 mol of 85% phosphoric acid, everything else is the same as in Example 1.

[0251] Example 17

[0252] Except for changing the amount of MnSO4·H2O to 1.2 mol in “1) Preparation of positive electrode active material”, adding 0.1 mol of VCl2 when preparing doped manganese oxalate, changing the amount of Li2CO3 to 0.492 mol, replacing 0.001 mol of Mo(SO4)3 with 0.005 mol of MgSO4, replacing H4SiO4 with H2SO4, and changing 0.0005 mol of NH4HF2 to 0.0025 mol, everything else is the same as in Example 1.

[0253] Example 18

[0254] Except for changing the amount of FeSO4·H2O to 0.5 mol in “1) Preparation of positive electrode active material”, adding 0.1 mol of VCl2 and 0.1 mol of CoSO4 when preparing doped manganese oxalate, changing the amount of Li2CO3 to 0.492 mol, replacing 0.001 mol of Mo(SO4)3 with 0.005 mol of MgSO4, replacing H4SiO4 with H2SO4, and changing 0.0005 mol of NH4HF2 to 0.0025 mol, everything else is the same as in Example 1.

[0255] Example 19

[0256] Except for changing the amount of FeSO4·H2O to 0.4 mol and the amount of CoSO4 from 0.1 mol to 0.2 mol in “1) Preparation of positive electrode active material”, the rest is the same as in Example 18.

[0257] Example 20

[0258] Except for changing the amount of MnSO4·H2O to 1.5 mol, the amount of FeSO4·H2O to 0.1 mol, and the amount of CoSO4 to 0.3 mol in “1) Preparation of positive electrode active material”, the rest is the same as in Example 18.

[0259] Example 21

[0260] Except for replacing 0.1 mol of CoSO4 with 0.1 mol of NiSO4 in “1) Preparation of positive electrode active material”, the rest is the same as in Example 18.

[0261] Example 22

[0262] Except for changing the amount of mnSO4·H2O to 1.5 mol, the amount of FeSO4·H2O to 0.2 mol, and the amount of 0.1 mol of CoSO4 to 0.2 mol of NiSO4 in “1) Preparation of positive electrode active material”, the rest is the same as in Example 18.

[0263] Example 23

[0264] Except for changing the amount of mnSO4·H2O to 1.4 mol, the amount of FeSO4·H2O to 0.3 mol, and the amount of CoSO4 to 0.2 mol in “1) Preparation of positive electrode active material”, the rest is the same as in Example 18.

[0265] Example 24

[0266] Except for the following changes in “1) Preparation of positive electrode active material”, where 1.3 mol of MnSO4·H2O is replaced with 1.2 mol, 0.7 mol of FeSO4·H2O is replaced with 0.5 mol, 0.1 mol of VCl2 and 0.2 mol of CoSO4 are added when preparing doped manganese oxalate, the amount of Li2CO3 is changed to 0.497 mol, 0.001 mol of Mo(SO4)3 is replaced with 0.005 mol of MgSO4, H4SiO4 is replaced with H2SO4, and 0.0005 mol of NH4HF2 is changed to 0.0025 mol, everything else is the same as in Example 1.

[0267] Example 25

[0268] Except for changing the amount of MnSO4·H2O to 1.0 mol, the amount of FeSO4·H2O to 0.7 mol, and the amount of CoSO4 to 0.2 mol in “1) Preparation of positive electrode active material”, the rest is the same as in Example 18.

[0269] Example 26

[0270] Except for the following changes in “1) Preparation of positive electrode active material”, where the amount of MnSO4·H2O is changed to 1.4 mol, the amount of FeSO4·H2O is changed to 0.3 mol, 0.1 mol of VCl2 and 0.2 mol of CoSO4 are added when preparing doped manganese oxalate, the amount of Li2CO3 is changed to 0.4825 mol, 0.001 mol of Mo(SO4)3 is replaced with 0.005 mol of MgSO4, the amount of H4SiO4 is changed to 0.1 mol, the amount of phosphoric acid is changed to 0.9 mol, and the amount of NH4HF2 is changed to 0.04 mol, everything else is the same as in Example 1.

[0271] Example 27

[0272] Except for the following changes in “1) Preparation of positive electrode active material”, where the amount of MnSO4·H2O is changed to 1.4 mol, the amount of FeSO4·H2O is changed to 0.3 mol, 0.1 mol of VCl2 and 0.2 mol of CoSO4 are added when preparing doped manganese oxalate, the amount of Li2CO3 is changed to 0.485 mol, 0.001 mol of Mo(SO4)3 is replaced with 0.005 mol of MgSO4, the amount of H4SiO4 is changed to 0.08 mol, the amount of phosphoric acid is changed to 0.92 mol, and the amount of NH4HF2 is changed to 0.05 mol, everything else is the same as in Example 1.

[0273] Comparative Example 1

[0274] Preparation of manganese oxalate: 1 mol of MnSO4·H2O was added to a reaction vessel, along with 10 L of deionized water and 1 mol of oxalic acid dihydrate (calculated as oxalic acid). The reaction vessel was heated to 80°C and stirred at 600 rpm for 6 hours until the reaction was terminated (no more bubbles were generated), yielding a manganese oxalate suspension. The suspension was then filtered, and the filter cake was dried at 120°C and subsequently ground to obtain a median particle size Dv. 50 Manganese oxalate particles with a diameter of 50-200 nm.

[0275] Preparation of lithium manganese phosphate: 1 mol of the above-mentioned manganese oxalate particles, 0.5 mol of lithium carbonate, an 85% phosphoric acid aqueous solution containing 1 mol of phosphoric acid, and 0.005 mol of sucrose were added to 20 L of deionized water. The mixture was transferred to a sand mill and thoroughly ground and stirred for 10 hours to obtain a slurry. The slurry was then transferred to a spray drying equipment for spray drying and granulation. The drying temperature was set at 250℃, and the granules were dried for 4 hours to obtain particles. Under a protective atmosphere of nitrogen (90 vol%) + hydrogen (10 vol%), the above powder was sintered at 700℃ for 10 hours to obtain carbon-coated LiMnPO4.

[0276] Comparative Example 2

[0277] Except for Comparative Example 1, where 1 mol of MnSO4·H2O was replaced with 0.85 mol of MnSO4·H2O and 0.15 mol of FeSO4·H2O, and the mixture was added to a mixer and thoroughly mixed for 6 hours before being added to the reactor, everything else was the same as in Comparative Example 1.

[0278] Comparative Example 3

[0279] Except for the following changes in “1) Preparation of positive electrode active material”, where the amount of MnSO4·H2O is changed to 1.9 mol, 0.7 mol of FeSO4·H2O is replaced with 0.1 mol of ZnSO4, the amount of Li2CO3 is changed to 0.495 mol, 0.001 mol of Mo(SO4)3 is replaced with 0.005 mol of MgSO4, the amount of phosphoric acid is changed to 1 mol, and H4SiO4 and NH4HF2 are not added, everything else is the same as in Example 1.

[0280] Comparative Example 4

[0281] Except for the following changes in “1) Preparation of positive electrode active material”, where the amount of MnSO4·H2O is changed to 1.2 mol, the amount of FeSO4·H2O is changed to 0.8 mol, the amount of Li2CO3 is changed to 0.45 mol, the 0.001 mol of Mo(SO4)3 is replaced with 0.005 mol of Nb2(SO4)5, the 0.999 mol of phosphoric acid is changed to 1 mol, the 0.0005 mol of NH4HF2 is changed to 0.025 mol, and H4SiO4 is not added, everything else is the same as in Example 1.

[0282] Comparative Example 5

[0283] Except for the following changes in “1) Preparation of positive electrode active material”, where the amount of MnSO4·H2O is changed to 1.4 mol, the amount of FeSO4·H2O is changed to 0.6 mol, the amount of Li2CO3 is changed to 0.38 mol, and 0.001 mol of Mo(SO4)3 is replaced with 0.12 mol of MgSO4, the rest is the same as in Example 1.

[0284] Comparative Example 6

[0285] Except for the following changes in “1) Preparation of positive electrode active material”, where the amount of MnSO4·H2O is changed to 0.8 mol, 0.7 mol of FeSO4·H2O is replaced with 1.2 mol of ZnSO4, the amount of Li2CO3 is changed to 0.499 mol, and 0.001 mol of Mo(SO4)3 is replaced with 0.001 mol of MgSO4, the rest is the same as in Example 1.

[0286] Comparative Example 7

[0287] Except for the following changes in “1) Preparation of positive electrode active material”, where the amount of MnSO4·H2O is changed to 1.4 mol, the amount of FeSO4·H2O is changed to 0.6 mol, the amount of Li2CO3 is changed to 0.534 mol, 0.001 mol of Mo(SO4)3 is replaced with 0.001 mol of MgSO4, the amount of phosphoric acid is changed to 0.88 mol, the amount of H4SiO4 is changed to 0.12 mol, and the amount of NH4HF2 is changed to 0.025 mol, everything else is the same as in Example 1.

[0288] Comparative Example 8

[0289] Except for the following changes in “1) Preparation of positive electrode active material”, where the amounts of MnSO4·H2O are changed to 1.2 mol, FeSO4·H2O to 0.8 mol, Li2CO3 to 0.474 mol, 0.001 mol Mo(SO4)3 to 0.001 mol MgSO4, phosphoric acid to 0.93 mol, H4SiO4 to 0.07 mol, and NH4HF2 to 0.06 mol, the rest are the same as in Example 1.

[0290] Properties of positive electrode active materials and battery performance testing methods

[0291] Methods for measuring lattice change rate

[0292] Under a constant temperature environment of 25℃, the positive electrode active material sample was placed in an XRD (model Bruker D8 Discover) and tested at a rate of 1° / minute. The test data were then organized and analyzed. Referring to the standard PDF card, the lattice constants a0, b0, c0 and v0 were calculated (a0, b0 and c0 represent the length of each aspect of the unit cell, and v0 represents the volume of the unit cell, which can be directly obtained from the XRD refinement results).

[0293] Using the coin cell preparation method described in the above embodiments, the positive electrode active material sample was prepared into a coin cell, and the coin cell was charged at a low rate of 0.05C until the current decreased to 0.01C. Then, the positive electrode sheet of the coin cell was removed and immersed in DMC for 8 hours. After drying, powder was scraped off, and particles with a diameter less than 500nm were screened out. Samples were taken, and their lattice constant v1 was calculated in the same manner as the fresh samples tested above. The lattice change rate before and after complete lithium insertion / extraction is shown in the table, with (v0-v1) / v0×100% representing the lattice change rate before and after complete lithium insertion / extraction.

[0294] 2. Method for measuring the concentration of Li / Mn antisite defects

[0295] The XRD results obtained from the "lattice change rate measurement method" are compared with the PDF (Powder Diffraction File) card of the standard crystal to determine the Li / Mn antisite defect concentration. Specifically, the XRD results obtained from the "lattice change rate measurement method" are imported into the General Structure Analysis System (GSAS) software to automatically obtain refined results, which include the occupancy of different atoms. The Li / Mn antisite defect concentration is then obtained by reading the refined results.

[0296] 3. Surface oxygen valence state measurement method

[0297] Five grams of positive electrode active material sample were taken and prepared into a coin cell according to the coin cell preparation method described in the above embodiments. The coin cell was charged at a low rate of 0.05C until the current decreased to 0.01C. Then, the positive electrode sheet of the coin cell was removed and immersed in DMC for 8 hours. Then, it was dried, scraped off, and particles with a particle size of less than 500 nm were screened out. The obtained particles were measured using electron energy loss spectroscopy (EELS, using a Talos F200S instrument) to obtain the energy loss near-edge structure (ELNES), which reflects the density of states and energy level distribution of the element. Based on the density of states and energy level distribution, the number of occupied electrons was calculated by integrating the valence band density of states data, thereby deducing the valence state of the surface oxygen after charging.

[0298] 4. Compacted density measurement method

[0299] Place 5g of powder into a compaction mold (CARVER mold, model 13mm, USA), and then place the mold on a compaction density instrument. Apply a pressure of 3T, and read the thickness of the powder under pressure (thickness after depressurization) on the instrument. Calculate the compaction density using ρ = m / v.

[0300] 5. Method for measuring the amount of Mn (and Mn-doped Fe) dissolved after cycling

[0301] The full battery, after being cycled at 45°C until its capacity decayed to 80%, was discharged at a 0.1C rate until the cutoff voltage of 2.0V. Then, the battery was disassembled, the negative electrode was removed, and 30 unit areas (1540.25 mm²) were randomly selected from the negative electrode. 2 The discs were tested using an Agilent ICP-OES730 inductively coupled plasma emission spectrometry (ICP). The amounts of Fe (if the Mn site of the positive electrode active material is doped with Fe) and Mn were calculated based on the ICP results, thus determining the amount of Mn (and Mn-doped Fe) dissolved after cycling. The testing standard was based on EPA-6010D-2014.

[0302] 6. Method for measuring the initial specific capacity of button cells

[0303] At 2.5–4.3V, the button cell is charged at 0.1C to 4.3V, then charged at 4.3V at a constant voltage until the current is less than or equal to 0.05mA. After resting for 5 minutes, it is discharged at 0.1C to 2.0V. The discharge capacity at this point is the initial specific capacity, denoted as D0.

[0304] 7.3C Charging Constant Current Ratio Measurement Method

[0305] Under a constant temperature of 25℃, a fresh full battery is left to stand for 5 minutes, then discharged at 1 / 3C to 2.5V. After standing for 5 minutes, it is charged at 1 / 3C to 4.3V, and then charged at a constant voltage of 4.3V until the current is less than or equal to 0.05mA. After standing for 5 minutes, the charge capacity at this point is recorded as C0. The battery is then discharged at 1 / 3C to 2.5V, left to stand for 5 minutes, and then charged at 3C to 4.3V. After standing for 5 minutes, the charge capacity at this point is recorded as C1. The constant current ratio for 3C charging is C1 / C0 × 100%.

[0306] The higher the constant current ratio during 3C charging, the better the battery's rate performance.

[0307] 8. Full battery 45℃ cycle performance test

[0308] Under constant temperature conditions of 45℃, the full battery is charged at 1C to 4.3V within a range of 2.5V to 4.3V. Then, it is charged at a constant voltage of 4.3V until the current is less than or equal to 0.05mA. After resting for 5 minutes, it is discharged at 1C to 2.5V, and the discharge capacity at this point is recorded as D0. This charge-discharge cycle is repeated until the discharge capacity decreases to 80% of D0. The number of cycles completed at this point is recorded (referred to as the "45℃ cycle number").

[0309] 9. Full battery gas expansion test at 60°C

[0310] Full cells at 100% state of charge (SOC) were stored at 60°C. The open-circuit voltage (OCV) and internal resistance (IMP) were measured before, during, and after storage to monitor SOC, and the cell volume was also measured. Every 48 hours of storage, the full cells were removed, allowed to stand for 1 hour, and then the OCV and IMP were measured. After cooling to room temperature, the cell volume was measured using the water displacement method. The water displacement method involves first measuring the cell's weight (F1) separately using a balance with automatic unit conversion, and then completely immersing the cell in deionized water (with a known density of 1 g / cm³). 3 In the experiment, the weight F2 of the battery at this moment is measured, and the buoyant force F on the battery is measured. 浮 That is, F1-F2, and then according to Archimedes' principle, F 浮 =ρ×g×V 排 The battery volume V is calculated to be V = (F1 - F2) / (ρ × g).

[0311] Based on the OCV and IMP test results, the battery in this embodiment maintained a state of charge (SOC) of over 99% throughout the entire experiment until the end of storage.

[0312] After 30 days of storage, the battery volume was measured, and the percentage increase in battery volume after storage was calculated relative to the battery volume before storage.

[0313] Additionally, measure the battery's remaining capacity. Charge the full battery at 1C to 4.3V within the 2.5–4.3V range, then charge it at a constant voltage of 4.3V until the current is less than or equal to 0.05mA. Let it rest for 5 minutes, and record the charging capacity at this point as the battery's remaining capacity.

[0314] Table 1 shows the composition of the positive electrode active materials of Examples 1-11 and Comparative Examples 1-8. Table 2 shows the performance data of the positive electrode active materials of Examples 1-11 and Comparative Examples 1-8, whether coin cells or full cells, measured according to the above performance test methods. Table 3 shows the composition of the positive electrode active materials of Examples 12-27. Table 4 shows the performance data of the positive electrode active materials of Examples 12-27, whether coin cells or full cells, measured according to the above performance test methods.

[0315]

[0316]

[0317]

[0318]

[0319]

[0320]

[0321]

[0322]

[0323] Positive electrode slurry, positive electrode sheet, and full cell were prepared using the positive electrode active materials prepared in the above embodiments and comparative examples, and the performance of the slurry and cell was tested.

[0324] In the following comparative examples and embodiments, the preparation of the electrodes and batteries, the slurry, and the performance testing of the batteries were carried out according to the following methods:

[0325] 1) Preparation of positive electrode sheet

[0326] The positive electrode active material, conductive agent acetylene black, binder polyvinylidene fluoride (PVDF), wetting agent, and dispersant are mixed evenly in an N-methylpyrrolidone solvent system. The mixture is then coated onto an aluminum foil with a base coating, dried, and cold-pressed to obtain the positive electrode sheet. The weight ratio of the positive electrode active material, conductive agent acetylene black, binder polyvinylidene fluoride (PVDF), dispersant, and wetting agent is (92-Y1-Y2):2.5:5.5:Y1:Y2. The coating amount is 0.02 g / cm³. 2 The compacted density is 2.4 g / cm³. 3 .

[0327] Aluminum foil with a conductive undercoat is prepared according to the following method:

[0328] Preparation of conductive primer coating slurry: Polyacrylic acid-acrylate copolymer (weight average molecular weight 340,000) and conductive agent (Super P) are mixed in a weight ratio of 40:60, dissolved / dispersed in deionized water to prepare conductive primer coating slurry.

[0329] A conductive undercoating slurry is applied to both sides of an aluminum foil, and after drying, a conductive undercoating with a thickness of 2 μm is formed on each side. An aluminum foil with a conductive undercoating is obtained.

[0330] 2) Preparation of negative electrode sheet

[0331] Artificial graphite (anode active material), hard carbon, acetylene black (conductive agent), styrene-butadiene rubber (SBR) (binder), and sodium carboxymethyl cellulose (CMC) (thickener) were mixed evenly in deionized water at a weight ratio of 90:5:2:2:1. The mixture was then coated onto copper foil, dried, and cold-pressed to obtain the negative electrode sheet. The coating amount was 0.01 g / cm³. 2 The compacted density is 1.7 g / cm³. 3 .

[0332] 3) Assembly of the full battery

[0333] Using a porous polyethylene (PE) polymer film as a separator, the positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrodes to provide isolation. The resulting bare cell is then wound up. The bare cell is placed in an outer packaging, infused with electrolyte, and sealed to obtain a full battery (hereinafter referred to as "full battery").

[0334] The weight of the positive electrode active material in a single full cell is 11.85g; the weight of the negative electrode active material is 6.73g.

[0335] 4) Slurry viscosity test

[0336] a. Place the viscometer on the designated operating table, adjust the support to center the horizontal bubble, and ensure the viscometer is horizontal;

[0337] b. Sampling: Take 500mL of the sample to be tested in a 500mL glass beaker and test at a constant temperature of 25℃;

[0338] c. Testing: Select the corresponding rotor and speed. After visually inspecting the rotor for deformation / stains, tilt the rotor and slowly immerse it until the part below the rotor groove is completely immersed. Do not stir the slurry with the rotor during the immersion process. Press the start button to test for 10 minutes. Read and record the data once every minute. The final viscosity is the average of 10 sets of data.

[0339] Figure 8 The instrument and testing procedure used for slurry viscosity testing are illustrated by way of example.

[0340] 5) Slurry flowability test (gel test)

[0341] Test method: Take 500mL of the sample to be tested in a 500mL glass beaker. Insert a 25cm long and 2cm wide graduated steel ruler vertically along the edge of the beaker to a depth of 4-5cm below the liquid surface. Slowly lift the slurry and observe the flow of the slurry brought out by the steel ruler, taking a photo as a record. The presence of gel is considered a failure.

[0342] 6) Slurry filtration performance test

[0343] Prepare a 200-mesh filter screen (25cm x 25cm), fold it into a triangle, as shown below. Figure 9 As shown; quickly pour 500mL of slurry along one side of the three-layer filter screen. Start timing from when all the slurry has been poured in, and record the filtration time when 300mL of slurry has passed through the filter screen. If the time is greater than 2 minutes, it is considered unqualified.

[0344] 7) Discharge DC impedance test

[0345] At 25℃, the lithium-ion battery was charged to 4.3V at a constant current and constant voltage of 1.0C (1.0C refers to the nominal capacity); the battery charge was adjusted to 50% SoC at a 1.0C rate, and after standing for 5 minutes, it was discharged at a constant current of 4C for 30s (voltage data was collected every 1s). The impedance after 30s of discharge is the test data.

[0346] 8) Number of cycles with 80% capacity retention at 45℃ (referred to as "number of cycles at 45℃")

[0347] Under constant temperature conditions of 45℃, the full battery was charged at 1C to 4.3V within a range of 2.5V to 4.3V. Then, it was charged at a constant voltage of 4.3V until the current was less than or equal to 0.05mA. After resting for 5 minutes, it was discharged at 1C to 2.5V, and the discharge capacity at this point was recorded as D0. This charge-discharge cycle was repeated until the discharge capacity decreased to 80% of D0. The number of cycles completed at this point was recorded.

[0348]

[0349]

[0350]

[0351]

[0352]

[0353]

[0354] As shown in the table above, hydrogenated nitrile butadiene rubber can be compounded with PVP, isopropanolamine, 2-amino-2-methyl-1-propanol or styrene-maleic anhydride copolymer to obtain good slurry processing properties and / or battery performance.

[0355] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A positive electrode active material composition, comprising a positive electrode active material, a dispersant, and a wetting agent, wherein, The positive electrode active material has the chemical formula Li a A x Mn 1-y B y P 1-z C z O 4-n D n A includes one or more elements selected from Zn, Al, Na, K, Mg, Nb, Mo, and W; B includes one or more elements selected from Ti, V, Zr, Fe, Ni, Mg, Co, Ga, Sn, Sb, Nb, and Ge; C includes one or more elements selected from B (boron), S, Si, and N; D includes one or more elements selected from S, F, Cl, and Br; a is selected from the range of 0.9 to 1.1; x is selected from the range of 0.001 to 0.1; y is selected from the range of 0.001 to 0.5; z is selected from the range of 0.001 to 0.1; n is selected from the range of 0.001 to 0.1; and the positive electrode active material is electrically neutral. The dispersant comprises a polymer, and the polymer comprises: Equation 1 represents the first single-unit cell; A second monomer unit selected from at least one of the monomer units represented by Formula 2 and the monomer units represented by Formula 3; and A third monomer unit selected from at least one of the monomer units represented by Formula 4 and the monomer units represented by Formula 5. Formula 1 Formula 2 Formula 3 Formula 4 Formula 5; The surface tension of the wetting agent is 20mN / m to 40mN / m, and the molecular structure of the wetting agent includes at least one of the following functional groups: -CN, -NH2, -NH-, -N-, -OH, -C=O, -COO-, -C(=O)-OC(=O)-.

2. The positive electrode active material composition according to claim 1, wherein, Based on the total mass of the polymer The first monomer unit has a mass percentage content of M1, where M1 is 10% to 55%; and / or, The second monomer unit has a mass percentage content of M2, where M2 is 40%~80%; and / or, The mass percentage of the third monomer unit is M3, where M3 is 0% to 10%.

3. The positive electrode active material composition according to claim 1, wherein, Based on the total mass of the polymer The first monomer unit has a mass percentage content of M1, where M1 is 25% to 55%; and / or, The second monomer unit has a mass percentage content of M2, where M2 is 50%~70%; and / or, The mass percentage of the third monomer unit is M3, and M3 is 0.001%~2%.

4. The positive electrode active material composition according to claim 2, wherein, M3 / (M2+M3) is 0%~5%.

5. The positive electrode active material composition according to claim 2, wherein, M3 / (M2+M3) is 0.001%~1%.

6. The positive electrode active material composition according to claim 1, wherein, The polymer is hydrogenated nitrile butadiene rubber; and / or, The polymer has a weight-average molecular weight of 50,000 to 500,000; and / or, Based on the total mass of the positive electrode active material, the mass percentage of the dispersant is X1, where X1 is 0.05% to 1%.

7. The positive electrode active material composition according to claim 1, wherein, The polymer has a weight-average molecular weight of 150,000 to 350,000; and / or, Based on the total mass of the positive electrode active material, the mass percentage of the dispersant is X1, where X1 is 0.1% to 0.5%.

8. The positive electrode active material composition according to claim 1, wherein, The wetting agent includes one or more selected from small molecule organic solvents and low molecular weight polymers. The small molecule organic solvent includes one or more selected from alkanolamines, alcohols, and nitrile compounds; The low molecular weight polymer includes one or more selected from maleic anhydride-styrene copolymer, polyvinylpyrrolidone, and polysiloxane.

9. The positive electrode active material composition according to claim 8, wherein, The alkanolamine compounds have 1 to 16 carbon atoms; the low molecular weight polymers have a weight-average molecular weight of less than 6000.

10. The positive electrode active material composition according to claim 8, wherein, The alkanolamine compound has 2 to 6 carbon atoms; the low molecular weight polymer has a weight-average molecular weight of 3000 to 6000.

11. The positive electrode active material composition according to claim 1, wherein, Based on the total mass of the positive electrode active material, the mass percentage of the wetting agent is X2, where X2 is 0.05% to 2%.

12. The positive electrode active material composition according to claim 1, wherein, Based on the total mass of the positive electrode active material, the mass percentage of the wetting agent is X2, where X2 is 0.2% to 0.8%.

13. The positive electrode active material composition according to claim 11, wherein, Based on the total mass of the positive electrode active material, the mass percentage of the dispersant is X1, where X1 is 0.05%~1% and X1 / X2 is 0.05~20.

14. The positive electrode active material composition according to claim 13, wherein, X1 / X2 is 0.1~1.

15. The positive electrode active material composition according to claim 13, wherein, X1 / X2 is 0.3~0.

8.

16. The positive electrode active material composition according to claim 1, wherein, A, C, and D are each an element within their respective ranges, and B is at least two elements within its range.

17. The positive electrode active material composition according to claim 1, wherein, A is any element selected from Mg and Nb, and / or, B is selected from at least two elements chosen from Fe, Ti, V, Co, and Mg, and / or, C is S, and / or, D is F.

18. The positive electrode active material composition according to claim 1, wherein, B is Fe and one or more elements selected from Ti, V, Co and Mg.

19. The positive electrode active material composition according to claim 1, wherein, x is selected from the range of 0.001 to 0.005; and / or, y is selected from the range of 0.01 to 0.5; and / or, z is selected from the range of 0.001 to 0.005; and / or, n is selected from the range of 0.001 to 0.

005.

20. The positive electrode active material composition according to claim 1, wherein, y is selected from the range of 0.25 to 0.

5.

21. The positive electrode active material composition according to claim 1, wherein, (1-y): y is in the range of 1 to 4, and a:x is in the range of 9 to 1100.

22. The positive electrode active material composition according to claim 1, wherein, (1-y): y is in the range of 1.5 to 3.

23. The positive electrode active material composition according to claim 1, wherein, a:x is in the range of 190 to 998.

24. The positive electrode active material composition according to claim 1, wherein, The lattice variation rate of the positive electrode active material is less than 8%.

25. The positive electrode active material composition according to claim 1, wherein, The lattice change rate of the positive electrode active material is less than 4%.

26. The positive electrode active material composition according to claim 1, wherein, The concentration of Li / Mn antisite defects in the positive electrode active material is below 2%.

27. The positive electrode active material composition according to claim 1, wherein, The concentration of Li / Mn antisite defects in the positive electrode active material is below 0.5%.

28. The positive electrode active material composition according to claim 1, wherein, The surface oxygen valence state of the positive electrode active material is below -1.

82.

29. The positive electrode active material composition according to claim 1, wherein, The surface oxygen valence state of the positive electrode active material is -1.89 to -1.

98.

30. The positive electrode active material composition according to claim 1, wherein, The compaction density of the positive electrode active material at 3T is 2.0 g / cm³. 3 above.

31. The positive electrode active material composition according to claim 1, wherein, The compaction density of the positive electrode active material at 3T is 2.2 g / cm³. 3 above.

32. The positive electrode active material composition according to claim 1, wherein, The surface of the positive electrode active material is coated with carbon material.

33. A positive electrode slurry comprising a positive electrode active material composition according to any one of claims 1-32.

34. The positive electrode slurry according to claim 33 further includes one or more of a solvent, a positive electrode conductive agent, and a positive electrode binder.

35. The positive electrode slurry according to claim 34, wherein, The solvent includes N-methylpyrrolidone (NMP); and / or, The positive electrode binder comprises one or more selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin; and / or, The positive electrode conductive agent includes one or more selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

36. The positive electrode slurry according to claim 33, wherein, The solid content of the positive electrode slurry is 40%~70%; and / or, The viscosity of the positive electrode slurry at 20°C is 3000 mPa·s to 50000 mPa·s.

37. The positive electrode slurry according to claim 33, wherein, The solid content of the positive electrode slurry is 55%~65%; and / or, The viscosity of the positive electrode slurry at 20°C is 10000 mPa·s to 20000 mPa·s.

38. A positive electrode sheet, comprising a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector, wherein, The positive electrode film layer comprises the positive electrode active material composition according to any one of claims 1-32, or is formed by coating the positive electrode slurry according to any one of claims 33-37.

39. The positive electrode sheet according to claim 38, wherein the coating method is selected from dip coating, film coating, electrostatic spraying and spin coating.

40. The positive electrode sheet according to claim 38, wherein, Based on the total mass of the positive electrode film layer The positive electrode active material has a mass percentage content of W1, where W1 is 90%~99.5%; and / or, The dispersant has a mass percentage content of W2, where W2 is less than 1%; and / or, The mass percentage of the wetting agent is W3, and W3 is less than 2%.

41. The positive electrode sheet according to claim 38, wherein, Based on the total mass of the positive electrode film layer The positive electrode active material has a mass percentage content of W1, where W1 is 95%~99%; and / or, The dispersant has a mass percentage content of W2, where W2 is 0.1% to 0.5%; and / or, The wetting agent has a mass percentage content of W3, where W3 is 0.1% to 0.5%.

42. The positive electrode sheet according to claim 38, wherein the positive electrode slurry comprises one or more of a positive electrode conductive agent and a positive electrode binder; based on the total mass of the positive electrode film, the mass percentage of the positive electrode binder is W4, where W4 is less than 5.5%; and / or, The positive electrode conductive agent has a mass percentage content of W5, which is less than 2.5%.

43. The positive electrode sheet according to claim 38, wherein the positive electrode slurry comprises one or more of a positive electrode conductive agent and a positive electrode binder; based on the total mass of the positive electrode film, The positive electrode binder has a mass percentage content of W4, where W4 is 1% to 3%; and / or, The positive electrode conductive agent has a mass percentage content of W5, which is 0.1% to 1%.

44. A secondary battery comprising a positive electrode according to any one of claims 38-43.

45. A battery module comprising a positive electrode according to any one of claims 38-43, or a secondary battery according to claim 44.

46. ​​A battery pack comprising a positive electrode according to any one of claims 38-43, a secondary battery according to claim 44, or a battery module according to claim 45.

47. An electrical device comprising a positive electrode according to any one of claims 38-43, a secondary battery according to claim 44, a battery module according to claim 45, or a battery pack according to claim 46.

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