Positive electrode sheet, secondary battery, and electric device

Abstract

The application provides a positive electrode sheet, a secondary battery and an electric device. The positive electrode sheet comprises a positive electrode current collector, a positive electrode film layer arranged on at least one surface of the positive electrode current collector, and a conductive primer layer between the positive electrode current collector and the positive electrode film layer, wherein the positive electrode film layer comprises a positive electrode active material with a chemical formula of Li a A x Mn 1‑y B y P 1‑z C z O 4‑n D n The conductive primer layer comprises a first polymer, a first water-based binder and a first conductive agent.

Description

Technical Field

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

[0002] In recent years, with the increasingly wide application of secondary batteries, they have been widely used in energy storage power systems such as hydropower, thermal power, wind power, and solar power plants, as well as in power tools, electric bicycles, electric motorcycles, electric cars, military equipment, aerospace, and many other fields. Due to the significant development of secondary batteries, higher requirements have been placed on their energy density and cycle performance.

[0003] The related technology involves placing a conductive undercoat between the active material and the current collector of the positive electrode to improve one or more performance characteristics of the secondary battery.

[0004] To further improve battery performance, existing technologies require superior positive electrode plates. Summary of the Invention

[0005] In view of the above-mentioned problems, this application provides a novel positive electrode sheet, a secondary battery, and an electrical device. The novel positive electrode sheet includes a novel positive electrode active material and a novel conductive undercoating, which are described below.

[0006] A first aspect of this application provides a positive electrode sheet, comprising a positive current collector, a positive electrode film layer disposed on at least one surface of the positive current collector, and a conductive undercoat layer located between the positive current collector and the positive electrode film layer, wherein...

[0007] The positive electrode film layer includes a chemical formula Li a A x Mn 1-y B y P 1-z C z O 4-n D n The positive electrode active material comprises, wherein 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.

[0008] The conductive undercoat includes a first polymer, a first water-based binder, and a first conductive agent.

[0009] The first polymer comprises:

[0010] Equation 1 represents the first single-unit cell;

[0011] 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;

[0012] 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; and

[0013] The fourth monomer unit represented by Equation 6, R 1 R 2 R 3 Each group independently represents H, carboxyl, ester, and the following substituted or unsubstituted groups: C1–C10 alkyl, C1–C10 alkoxy, C2–C10 alkenyl, C6–C10 aryl, R 4 The following groups, whether substituted or unsubstituted, represent H: alkyl (C1-C10), alkoxy (C1-C10), alkenyl (C2-C10), and aryl (C6-C10).

[0014]

[0015] In some embodiments, based on the total mass of the first polymer,

[0016] The first monomer unit has a mass percentage content of M1, where M1 is 10% to 55%, optionally 25% to 55%; and / or,

[0017] The second monomer unit has a mass percentage content of M2, where M2 is 40%–80%, optionally 50%–70%; and / or,

[0018] The third monomer unit has a mass percentage content of M3, where M3 is 0% to 10%, optionally 0.001% to 2%; and / or,

[0019] The fourth monomer unit has a mass percentage content of M4, where M4 is 0% to 10%, and optionally 0.1% to 1%.

[0020] In some implementations, M3 / (M2+M3) is 0% to 5%, and optionally 0.001% to 1%.

[0021] In some embodiments, the first polymer is selected from one or more of hydrogenated nitrile butadiene rubber and hydrogenated carboxylated nitrile butadiene rubber; and / or,

[0022] In some embodiments, the weight-average molecular weight of the first polymer is 50,000 to 1,500,000, and optionally 200,000 to 400,000.

[0023] In some embodiments, the first waterborne adhesive comprises one or more selected from waterborne polyacrylic resins and their derivatives, waterborne amino-modified polypropylene resins and their derivatives, and polyvinyl alcohol and its derivatives, optionally including waterborne acrylic-acrylate copolymers; and / or,

[0024] The weight-average molecular weight of the first water-based adhesive is 200,000 to 1,500,000, and optionally 300,000 to 400,000.

[0025] In some embodiments, the first conductive agent includes one or more selected from superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers, and optionally includes one or more selected from carbon nanotubes, graphene, and carbon nanofibers.

[0026] In some embodiments, the total mass of the conductive undercoating is used as the basis for measurement.

[0027] The mass percentage of the first polymer is X1, where X1 is 5% to 20%, optionally 5% to 10%; and / or,

[0028] The first water-based adhesive has a mass percentage content of X2, where X2 is 30% to 80%, optionally 40% to 50%; and / or,

[0029] The mass percentage of the first conductive agent is X3, where X3 is 10% to 50%, and optionally 40% to 50%.

[0030] In some embodiments, the thickness of the conductive undercoat is 1 μm to 20 μm, and optionally 3 μm to 10 μm.

[0031] In some embodiments, the positive electrode film layer further includes one or more selected from wetting agents and dispersants; optionally, the positive electrode film layer also includes both wetting agents and dispersants.

[0032] In some embodiments, the surface tension of the wetting agent is 20 mN / m to 40 mN / m. Optionally, the wetting agent includes at least one of the following functional groups: -CN, -NH2, -NH-, -N-, -OH, -COO-, -C(=O)-OC(=O)-.

[0033] In some embodiments, the wetting agent includes one or more selected from small molecule organic solvents and low molecular weight polymers.

[0034] In some embodiments, the small molecule organic solvent includes one or more selected from alkanolamines, alcohols, and nitriles. Optionally, the alkanolamine has 1 to 16 carbon atoms, or optionally 2 to 6.

[0035] In some embodiments, 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, and optionally is between 3000 and 6000.

[0036] In some embodiments, the dispersant comprises a second polymer, and the second polymer comprises:

[0037] The fifth monomer unit represented by Equation 7;

[0038] A sixth monomeric unit selected from at least one of the monomeric units represented by Formula 8 and the monomeric units represented by Formula 9; and

[0039] A seventh monomer unit selected from at least one of the monomer units represented by Formula 10 and the monomer units represented by Formula 11.

[0040]

[0041] In some embodiments, based on the total mass of the second polymer,

[0042] The fifth monomer unit has a mass percentage content of M5, where M5 is 10% to 55%, optionally 25% to 55%; and / or,

[0043] The sixth monomer unit has a mass percentage content of M6, where M6 is 40%–80%, optionally 50%–70%; and / or,

[0044] The seventh monomer unit has a mass percentage content of M7, which is 0% to 10%, and optionally 0.001% to 2%.

[0045] In some implementations, M7 / (M6+M7) is 0% to 5%, and optionally 0.001% to 1%.

[0046] In some embodiments, the second polymer is hydrogenated nitrile butadiene rubber; and / or,

[0047] The weight-average molecular weight of the second polymer is 50,000 to 500,000, and optionally 150,000 to 350,000.

[0048] In some implementations, based on the total mass of the positive electrode film,

[0049] The dispersant has a mass percentage content of Y1, where Y1 is 0.05% to 1%, optionally 0.1% to 0.5%; and / or,

[0050] The impregnating agent has a mass percentage content of Y2, which is 0.05% to 2%, and optionally 0.2% to 0.8%.

[0051] In some implementations, Y1 / Y2 is 0.05 to 20, optionally 0.1 to 1, and further 0.3 to 0.8.

[0052] In some embodiments, the mass ratio of the first polymer to the second polymer in the positive electrode sheet is 1.5 to 5, and optionally 2 to 3.

[0053] 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;

[0054] Optionally,

[0055] A is any element selected from Mg and Nb, and / or,

[0056] B is at least two elements selected from Fe, Ti, V, Co, and Mg, optionally Fe and one or more elements selected from Ti, V, Co, and Mg, and / or,

[0057] C is S, and / or,

[0058] D is F.

[0059] In some implementations, x is selected from the range of 0.001 to 0.005; and / or,

[0060] 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; and / or,

[0061] In some implementations, z is selected from the range of 0.001 to 0.005; and / or,

[0062] In some implementations, n is selected from the range of 0.001 to 0.005.

[0063] 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.

[0064] In some embodiments, the lattice change rate of the positive electrode active material is less than 8%, and optionally less than 4%.

[0065] 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%.

[0066] 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.

[0067] In some embodiments, the compaction density of the positive electrode active material at 3T is 2.0 g / cm³. 3 The above is optional, 2.2 g / cm³. 3 above.

[0068] In some embodiments, the surface of the positive electrode active material is coated with carbon.

[0069] In some implementations, the specific surface area of ​​the positive electrode active material is 15 m². 2 / g~25m 2 / g, the coating weight on one side of the positive electrode current collector is 20mg / cm³. 2 ~40mg / cm 2 When the specific surface area of ​​the positive electrode active material is 15m² 2 / g~25m 2 / g, the coating weight on one side of the positive electrode current collector is 20mg / cm³. 2 ~40mg / cm 2 During the coating process, film peeling is prone to occur. This application employs a novel conductive undercoat to increase the adhesion strength between the positive electrode active material layer and the current collector.

[0070] A second aspect of this application provides a secondary battery comprising the positive electrode sheet described in any of the preceding claims.

[0071] A third aspect of this application provides an electrical device including the aforementioned secondary battery.

[0072] As a positive electrode active material for lithium-ion secondary batteries, lithium manganese phosphate has a disadvantage compared to other positive electrode active materials in terms of poor rate performance. Currently, this problem is usually solved by methods such as coating or doping. However, there is still a desire to further improve the rate performance, cycle performance, and high-temperature stability of lithium manganese phosphate positive electrode active materials.

[0073] The inventors of this application have repeatedly studied the effects of doping the Li, Mn, P and O sites of lithium manganese phosphate with various elements, and found that by simultaneously doping specific elements in 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 cathode active material.

[0074] The positive electrode active material of this application can be used, for example, in lithium-ion secondary batteries.

[0075] Specifically, the fourth aspect of this application proposes a positive electrode active material having the chemical formula Li a A x Mn 1- y B y P 1-z C z O 4-n D n ,

[0076] Wherein, A includes one or more elements selected from Zn, Al, Na, K, Mg, Nb, Mo, and W.

[0077] The element B includes one or more elements selected from Ti, V, Zr, Fe, Ni, Mg, Co, Ga, Sn, Sb, Nb, and Ge.

[0078] The C includes one or more elements selected from B (boron), S, Si, and N.

[0079] The D includes one or more elements selected from S, F, Cl, and Br.

[0080] The 'a' is selected from the range of 0.9 to 1.1, for example, 0.97, 0.977, 0.984, 0.988, 0.99, 0.991, 0.992, 0.993, 0.994, 0.995, 0.996, 0.997, 0.998, 1.01; the 'x' is selected from the range of 0.001 to 0.1, for example, 0.001, 0.005; and the 'y' is selected from the range of 0.001 to 0.5, for example, 0.001, 0. 0.05, 0.02, 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, 0.34, 0.345, 0.349, 0.35, 0.4, where z is selected from the range of 0.001 to 0.1, for example, 0.001, 0.005, 0.08, 0.1, and n is selected from the range of 0.001 to 0.1, for example, 0.001, 0.005, 0.08, 0.1, and the positive electrode active material is electrically neutral.

[0081] Unless otherwise stated, in the above chemical formulas, when A consists of two or more elements, the limitation on the range of x values ​​described above applies not only to the stoichiometric coefficient of each element as A, but also to the sum of the stoichiometric coefficients of all elements as A. For example, when A consists of two or more elements A1, A2...An, the stoichiometric coefficients x1, x2...xn of each of A1, A2...An must each fall within the range of x values ​​defined in this application, and the sum of x1, x2...xn must also fall within this range. Similarly, for the case where B, C, and D consist of two or more elements, the limitation on the range of stoichiometric coefficients of B, C, and D in this application also has the above meaning.

[0082] 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.

[0083] 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.

[0084] In some embodiments, A, C, and D are each independently any one element within their respective ranges, and B is at least two elements. This allows for easier and more accurate control of the composition of the positive electrode active material.

[0085] Optionally,

[0086] A is an element selected from Mg and Nb, and / or,

[0087] The element 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, and / or,

[0088] The C is S, and / or,

[0089] The D is F.

[0090] 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.

[0091] In some embodiments, 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, optionally from the range of 0.25 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. By selecting a value of y within the above ranges, the specific capacity and rate performance of the material can be further improved. By selecting a value of x within the above ranges, the kinetic performance of the material can be further improved. By selecting a value of z within the above ranges, the rate performance of the secondary battery can be further improved. By selecting a value of n within the above ranges, the high-temperature performance of the secondary battery can be further improved.

[0092] In some embodiments, the positive electrode active material satisfies the following: (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 190-998. Here, y represents the sum of the stoichiometric coefficients of the Mn-site doping elements. When the above conditions are met, the energy density and cycle performance of the positive electrode active material can be further improved.

[0093] In some embodiments, the lattice change rate of the positive electrode active material is less than 8%, and optionally, less than 4%. Reducing the lattice change rate facilitates Li ion transport, meaning that Li ions have greater migration ability within the material, which is beneficial for improving the rate performance of the secondary battery. The lattice change rate can be measured using methods known in the art, such as X-ray diffraction (XRD).

[0094] In some embodiments, the Li / Mn antisite defect concentration of the positive electrode active material is below 2%, and optionally, the Li / Mn antisite defect concentration is 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.

[0095] In some embodiments, the surface oxygen valence state of the positive electrode active material is below -1.82, 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).

[0096] In some embodiments, the compaction density of the positive electrode active material at 3 tons is 2.0 g / cm³. 3 The above is optional, 2.2 g / cm³. 3 The higher the compaction density, the greater the weight of active material per unit volume. Therefore, increasing the compaction density is beneficial for improving the volumetric energy density of the battery cell. Compaction density can be measured according to GB / T 24533-2009.

[0097] In some embodiments, the surface of the positive electrode active material is coated with carbon. This improves the conductivity of the positive electrode active material.

[0098] Beneficial effects

[0099] One or more embodiments of this application have one or more of the following beneficial effects:

[0100] (1) One or more of the solutions in this application can obtain significantly improved rate performance, improved cycle performance and / or high temperature stability by simultaneously doping specific elements in specific amounts at the four positions of the positive electrode active material lithium manganese phosphate at the Li site, Mn site, P site and O site, thereby obtaining a novel doped and modified positive electrode active material.

[0101] (2) When the BET specific surface area of ​​the positive electrode active material is large and there are many small particles, the bonding strength between the positive electrode active material and the current collector (aluminum foil) is weak, and the film delamination phenomenon occurs during the coating process. This application adopts a novel conductive undercoating to increase the bonding strength between the positive electrode active material layer and the current collector.

[0102] (3) During the process of coating the positive electrode active material slurry (containing solvent N-methylpyrrolidone, abbreviated as NMP) on the conductive base coating surface, the first polymer in the conductive base coating will dissolve again after contacting the solvent NMP, thereby diffusing with the positive electrode active material slurry. After curing, the active material layer can be integrated with the base coating, thereby effectively increasing the bonding strength between the positive electrode film layer and the positive electrode current collector.

[0103] (4) When the first water-based binder in the conductive base coating is an acrylic-acrylate copolymer (weight average molecular weight: 200,000 to 1,500,000), the binder has strong polarity and can achieve good adhesion with the current collector (aluminum foil). In addition, the acrylic-acrylate copolymer has good stability in the electrolyte, high temperature resistance, corrosion resistance, and low electrolyte absorption efficiency (low swelling degree).

[0104] (3) When the conductive agent in the conductive base coating is selected from one or two of carbon black, acetylene black, carbon fiber, graphite and carbon nanotubes, it can reduce the interface resistance, improve the charge and discharge rate performance of the battery and extend the cycle life of the battery. Attached Figure Description

[0105] Figure 1 This is a schematic diagram of the positive electrode sheet according to an embodiment of this application.

[0106] Figure 2 This is a schematic flowchart illustrating the measurement of electrode adhesion force according to an embodiment of this application;

[0107] Figure 3 This is a schematic diagram of a secondary battery according to one embodiment of this application.

[0108] Figure 4 yes Figure 3 An exploded view of a secondary battery according to one embodiment of this application is shown.

[0109] Figure 5 This is a schematic diagram of a battery module according to one embodiment of this application.

[0110] Figure 6 This is a schematic diagram of a battery pack according to one embodiment of this application.

[0111] Figure 7 yes Figure 6 An exploded view of a battery pack according to one embodiment of this application is shown.

[0112] Figure 8 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.

[0113] Figure 9 XRD patterns of undoped LiMnPO4 and the positive electrode active material prepared in Example 2.

[0114] Figure 10 The image shows the EDS (Energy Dispersive X-ray Spectroscopy) spectrum of the positive electrode active material prepared in Example 2.

[0115] Explanation of reference numerals in the attached figures:

[0116] 1 Battery pack; 2 Upper casing; 3 Lower casing; 4 Battery module; 5 Secondary battery; 51 Housing; 52 Electrode assembly; 53 Top cover assembly; 11 Positive current collector; 112 Surface; 12 Conductive base coating; 13 Positive film layer; 510 Steel plate; 520 Double-sided adhesive; 530 Electrode sheet; Detailed Implementation

[0117] The following detailed description, with appropriate reference to the accompanying drawings, discloses embodiments of the negative electrode active material and its manufacturing method, positive electrode sheet, negative electrode sheet, secondary battery, battery module, battery pack, and device of this application. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0118] 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 expected that ranges of 60-110 and 80-120 are also included. 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 "ab" 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.

[0119] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0120] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0121] 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.

[0122] 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.

[0123] 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).

[0124] [Rechargeable Battery]

[0125] Secondary batteries, also known as rechargeable batteries or storage batteries, are batteries that can be recharged after being discharged to activate the active materials and continue to be used.

[0126] Typically, a secondary battery consists of a positive electrode, a negative electrode, a separator, and an electrolyte. During charging and discharging, active ions (such as lithium ions) repeatedly insert and extract between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, primarily prevents short circuits while allowing active ions to pass through. The electrolyte, also positioned between the positive and negative electrodes, mainly serves to conduct active ions.

[0127] [Positive electrode plate]

[0128] In some embodiments, this application provides a positive electrode sheet, including a positive current collector, a positive electrode film layer disposed on at least one surface of the positive current collector, and a conductive undercoat layer located between the positive current collector and the positive electrode film layer, wherein,

[0129] The positive electrode film layer includes a chemical formula Li a A x Mn 1-y B y P 1-z C z O 4-n D n The positive electrode active material comprises, wherein 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.

[0130] The conductive undercoat includes a first polymer, a first water-based binder, and a first conductive agent.

[0131] The first polymer comprises:

[0132] Equation 1 represents the first single-unit cell;

[0133] 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;

[0134] 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; and

[0135] The fourth monomer unit represented by Equation 6, R 1 R 2 R 3 Each group independently represents H, carboxyl, ester, and the following substituted or unsubstituted groups: C1–C10 alkyl, C1–C10 alkoxy, C2–C10 alkenyl, C6–C10 aryl, R 4 The following groups, whether substituted or unsubstituted, represent H: alkyl (C1-C10), alkoxy (C1-C10), alkenyl (C2-C10), and aryl (C6-C10).

[0136]

[0137]

[0138] In the positive electrode sheet based on the above scheme, the positive electrode film layer and the positive electrode current collector have enhanced bonding strength. Without theoretical limitations, during the process of coating the positive electrode active material slurry (containing the solvent N-methylpyrrolidone, abbreviated as NMP) onto the conductive undercoat surface, the first polymer in the conductive undercoat will dissolve again upon contact with the solvent NMP, thereby interdiffusion with the positive electrode active material slurry. After curing, the active material layer can fuse with the undercoat layer, thus effectively increasing the bonding strength between the positive electrode film layer and the positive electrode current collector.

[0139] In some embodiments, the first polymer is a random copolymer.

[0140] 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:

[0141]

[0142] In nitrile rubber, the linkage between butadiene (B) and acrylonitrile (A) units is generally a ternary combination of BAB, BBA, or ABB, ABA, and BBB. However, with increasing acrylonitrile content, a pentagonal linkage of AABAA can also occur, and it can even become the bulk polymer of acrylonitrile. In nitrile rubber, the sequence distribution of butadiene is mainly trans-1,4 structure, and its microstructure is related to the polymerization conditions.

[0143] Hydrogenated nitrile butadiene rubber (HNBR) is a product obtained by adding hydrogen to the carbon-carbon double bonds in the molecular chain of nitrile butadiene rubber until it is partially or completely saturated. The chemical formula of fully saturated hydrogenated nitrile butadiene rubber is as follows:

[0144]

[0145] There are three main methods for preparing hydrogenated nitrile butadiene rubber (HNBR): ethylene-acrylonitrile copolymerization, NBR solution hydrogenation, and NBR emulsion hydrogenation.

[0146] Hydrogenated carboxylated butyl rubber (HXNBR) is a polymer obtained by selectively hydrogenating C=C bonds in a copolymer formed by copolymerizing nitrile (e.g., acrylonitrile), conjugated diene (e.g., butadiene) and unsaturated carboxylic acid. Hydrogenated carboxylated butyl rubber is essentially hydrogenated nitrile butadiene rubber with the addition of carboxyl groups.

[0147] Esters of unsaturated carboxylic acids are, for example, esters of α,β-unsaturated monocarboxylic acids. Alkyl esters and alkoxyalkyl esters of α,β-unsaturated monocarboxylic acids are acceptable. Alkyl esters of α,β-unsaturated monocarboxylic acids, such as C1-C18 alkyl esters, are also acceptable, specifically alkyl esters of acrylic acid or methacrylic acid, such as C1-C18 alkyl esters, including methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, tert-butyl acrylate, 2-ethylhexyl acrylate, n-dodecyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, and 2-ethylhexyl methacrylate. Alkoxyalkyl esters of α,β-unsaturated monocarboxylic acids are also acceptable, specifically alkoxyalkyl esters of acrylic acid or methacrylic acid, such as C2-C12-alkoxyalkyl esters of acrylic acid or methacrylic acid, and further acceptable, methoxymethyl acrylate, methoxyethyl acrylate, ethoxyethyl acrylate, and methoxyethyl acrylate. Mixtures of alkyl esters (such as those mentioned above) and alkoxyalkyl esters (such as those in the forms mentioned above) may also be used. Hydroxyalkyl acrylates and hydroxyalkyl methacrylates wherein the hydroxyalkyl group has 1-12 carbon atoms may also be used, such as 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, and 3-hydroxypropyl acrylate. Similarly, epoxy-containing esters, such as glycidyl methacrylate, may be used. Cyanoalkyl acrylates and cyanoalkyl methacrylates wherein the cyanoalkyl group has 2-12 carbon atoms may also be used, such as α-cyanoethyl acrylate, β-cyanoethyl acrylate, and cyanobutyl methacrylate. Fluorine-substituted benzyl acrylates or methacrylates may also be used, such as fluorobenzyl acrylate and fluorobenzyl methacrylate. Fluoroalkyl acrylates and methacrylates may also be used, such as trifluoroethyl acrylate and tetrafluoropropyl methacrylate. Amino-containing α,β-unsaturated carboxylic acid esters, such as dimethylaminomethyl acrylate and diethylaminoethyl acrylate, may also be used.

[0148] In some embodiments, based on the total mass of the first polymer,

[0149] The first monomer unit has a mass percentage content of M1, where M1 is 10% to 55%, optionally 25% to 55%; and / or,

[0150] The second monomer unit has a mass percentage content of M2, where M2 is 40%–80%, optionally 50%–70%; and / or,

[0151] The third monomer unit has a mass percentage content of M3, where M3 is 0% to 10%, optionally 0.001% to 2%; and / or,

[0152] The fourth single-cell unit has a mass percentage of M4, which is 0% to 10%, optionally 0.1% to 1%. The positive electrode sheet based on this scheme is used in a secondary battery, significantly improving one or more performance characteristics. The conductive undercoating layer based on this scheme can dissolve moderately during the coating process, thereby forming a reinforced bond with the positive electrode film layer.

[0153] In some embodiments, based on the total mass of the first polymer,

[0154] The first monomer unit has a mass percentage content of M1, which is 10% to 55%, optionally 10%-15%, 15%-20%, 20%-25%, 25%-30%, 30%-35%, 35%-40%, 40%-45%, 45%-50%, or 50%-55%; and / or,

[0155] The second monomer unit has a mass percentage content of M2, which is 40% to 80%, optionally 40%-45%, 45%-50%, 50%-55%, 55%-60%, 60%-65%, 65%-70%, 70%-75%, or 75%-80%; and / or,

[0156] The third monomer unit has a mass percentage content of M3, where M3 is 0% to 10%, optionally 0.001%-1%, 1%-2%, 2%-3%, 3%-4%, 4%-5%, 5%-6%, 6%-7%, 7%-8%, 8%-9%, or 9%-10%; and / or,

[0157] The fourth monomer unit has a mass percentage of M4, which is 0%–10%, optionally 0.01%–1%, 1%–2%, 2%–3%, 3%–4%, 4%–5%, 5%–6%, 6%–7%, 7%–8%, 8%–9%, ​​or 9%–10%. The positive electrode sheet based on this scheme is used in a secondary battery, and one or more performance characteristics of the secondary battery are significantly improved. The conductive undercoating layer based on this scheme can dissolve moderately during the coating process, thereby forming a reinforced bond with the positive electrode film layer.

[0158] In some implementations, M3 / (M2+M3) is 0% to 5%, optionally 0.001% to 1%. Positive electrode sheets based on this scheme are used in secondary batteries, resulting in significant improvements in one or more performance characteristics of the secondary battery.

[0159] In some implementations, M3 / (M2+M3) is 0.01%-1%, 1%-2%, 2%-3%, 3%-4%, or 4%-5%.

[0160] In some embodiments, the first polymer is selected from one or more of hydrogenated nitrile butadiene rubber and hydrogenated carboxylated nitrile butadiene rubber; and / or,

[0161] In some embodiments, the weight-average molecular weight of the first polymer is 50,000 to 1,500,000, optionally 200,000 to 400,000. Positive electrode sheets based on this design are used in secondary batteries, resulting in significant improvements in one or more performance characteristics of the secondary battery.

[0162] In some embodiments, the weight-average molecular weight of the first polymer is 100,000-300,000, 300,000-500,000, 500,000-700,000, 700,000-900,000, 900,000-1,100,000, 1,100,000-1,300,000, or 1,300,000-1,500,000.

[0163] In some embodiments, the first waterborne adhesive comprises one or more selected from waterborne polyacrylic resins and their derivatives, waterborne amino-modified polypropylene resins and their derivatives, and polyvinyl alcohol and its derivatives, optionally including waterborne acrylic-acrylate copolymers; and / or,

[0164] The first aqueous binder has a weight-average molecular weight of 200,000 to 1,500,000, optionally 300,000 to 400,000. Positive electrode sheets based on this design are used in secondary batteries, resulting in significant improvements in one or more performance characteristics of the secondary battery.

[0165] In some embodiments, the weight-average molecular weight of the first aqueous adhesive is 100,000-300,000, 300,000-500,000, 500,000-700,000, 700,000-900,000, 900,000-1,100,000, or 1,100,000-1,300,000.

[0166] In some embodiments, the first conductive agent comprises one or more selected from superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers, and optionally includes one or more selected from carbon nanotubes, graphene, and carbon nanofibers. A positive electrode based on this scheme is used in a secondary battery, and one or more performance characteristics of the secondary battery are significantly improved.

[0167] In some embodiments, the total mass of the conductive undercoating is used as the basis for measurement.

[0168] The mass percentage of the first polymer is X1, where X1 is 5% to 20%, optionally 5% to 10%; and / or,

[0169] The first water-based adhesive has a mass percentage content of X2, where X2 is 30% to 80%, optionally 40% to 50%; and / or,

[0170] The first conductive agent has a mass percentage of X3, where X3 is 10% to 50%, and optionally 40% to 50%. The positive electrode sheet based on this scheme is used in a secondary battery, resulting in a significant improvement in one or more performance characteristics of the secondary battery.

[0171] In some embodiments, the thickness of the conductive undercoat is 1 μm to 20 μm, optionally 3 μm to 10 μm. Positive electrode sheets based on this design are used in secondary batteries, resulting in significant improvements in one or more performance characteristics of the secondary battery.

[0172] In some embodiments, the positive electrode film layer further includes one or more selected from wetting agents and dispersants; optionally, the positive electrode film layer also includes both a wetting agent and a dispersant. Positive electrode sheets based on this design are used in secondary batteries, resulting in significant improvements in one or more performance characteristics of the secondary battery.

[0173] In some embodiments, the surface tension of the wetting agent is 20 mN / m to 40 mN / m. Optionally, the wetting agent includes at least one of the following functional groups: -CN, -NH2, -NH-, -N-, -OH, -COO-, -C(=O)-OC(=O)-.

[0174] In some implementations, surface tension can be measured using the Wilhelmy Plate Method. Specific test procedures can be found in commonly used standards in the field, such as GB / T / 22237-2008 Surfactants—Determination of surface tension, and ASTM D1331-14. Standard test methods for surface tension and interfacial tension of coating solutions, solvents, surfactant solutions and related materials.

[0175] In some embodiments, the wetting agent includes one or more selected from small molecule organic solvents and low molecular weight polymers. Positive electrode sheets based on this design are used in secondary batteries, resulting in significant improvements in one or more performance characteristics of the secondary battery.

[0176] In some embodiments, the small molecule organic solvent includes one or more selected from alkanolamines, alcohols, and nitriles. Optionally, the alkanolamine has 1 to 16 carbon atoms, or optionally 2 to 6.

[0177] In some embodiments, 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, and optionally between 3000 and 6000. Positive electrode sheets based on this design are used in secondary batteries, resulting in significant improvements in one or more performance characteristics of the secondary battery.

[0178] In some embodiments, the dispersant comprises a second polymer, and the second polymer comprises:

[0179] The fifth monomer unit represented by Equation 7;

[0180] A sixth monomeric unit selected from at least one of the monomeric units represented by Formula 8 and the monomeric units represented by Formula 9; and

[0181] A seventh monomer unit selected from at least one of the monomer units represented by Formula 10 and the monomer units represented by Formula 11.

[0182]

[0183] The positive electrode sheet based on this scheme is used in secondary batteries, and one or more of the performance characteristics of the secondary battery are significantly improved.

[0184] In some embodiments, based on the total mass of the second polymer,

[0185] The fifth monomer unit has a mass percentage content of M5, where M5 is 10% to 55%, optionally 25% to 55%; and / or,

[0186] The sixth monomer unit has a mass percentage content of M6, where M6 is 40%–80%, optionally 50%–70%; and / or,

[0187] The seventh single-cell unit has a mass percentage of M7, which is 0% to 10%, and optionally 0.001% to 2%. The positive electrode sheet based on this scheme is used in a secondary battery, resulting in a significant improvement in one or more performance characteristics of the secondary battery.

[0188] In some embodiments, based on the total mass of the second polymer,

[0189] The fifth monomer unit has a mass percentage content of M5, which is 10% to 55%, optionally 10%-15%, 15%-20%, 20%-25%, 25%-30%, 30%-35%, 35%-40%, 40%-45%, 45%-50%, or 50%-55%; and / or,

[0190] The sixth monomer unit has a mass percentage content of M6, where M6 is 40%–80%, optionally 40%–45%, 45%–50%, 50%–55%, 55%–60%, 60%–65%, 65%–70%, 70%–75%, or 75%–80%; and / or,

[0191] The seventh monomer unit has a mass percentage content of M7, which is 0% to 10%, and optionally 0.01%-1%, 1%-2%, 2%-3%, 3%-4%, 4%-5%, 5%-6%, 6%-7%, 7%-8%, 8%-9%, or 9%-10%.

[0192] In some implementations, M7 / (M6+M7) is 0% to 5%, and optionally 0.001% to 1%.

[0193] In some embodiments, the second polymer is hydrogenated nitrile butadiene rubber; and / or,

[0194] The second polymer has a weight-average molecular weight of 50,000 to 500,000, optionally 150,000 to 350,000. Positive electrode sheets based on this design are used in secondary batteries, resulting in significant improvements in one or more performance characteristics.

[0195] In some implementations, based on the total mass of the positive electrode film,

[0196] The dispersant has a mass percentage content of Y1, where Y1 is 0.05% to 1%, optionally 0.1% to 0.5%; and / or,

[0197] The wetting agent has a mass percentage of Y2, which is 0.05% to 2%, optionally 0.2% to 0.8%. The positive electrode sheet based on this scheme is used in a secondary battery, and one or more performance characteristics of the secondary battery are significantly improved.

[0198] In some embodiments, Y1 / Y2 is 0.05 to 20, optionally 0.1 to 1, and further 0.3 to 0.8. Positive electrode sheets based on this scheme are used in secondary batteries, resulting in significant improvements in one or more performance characteristics of the secondary battery.

[0199] In some embodiments, the mass ratio of the first polymer to the second polymer in the positive electrode is 1.5 to 5, optionally 2 to 3. Positive electrode sheets based on this design are used in secondary batteries, resulting in significant improvements in one or more performance characteristics of the secondary battery.

[0200] 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;

[0201] Optionally,

[0202] A is any element selected from Mg and Nb, and / or,

[0203] B is at least two elements selected from Fe, Ti, V, Co, and Mg, optionally Fe and one or more elements selected from Ti, V, Co, and Mg, and / or,

[0204] C is S, and / or,

[0205] D represents F. Positive electrode sheets based on this scheme are used in secondary batteries, resulting in significant improvements in one or more performance characteristics.

[0206] In some implementations, x is selected from the range of 0.001 to 0.005; and / or,

[0207] 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; and / or,

[0208] In some implementations, z is selected from the range of 0.001 to 0.005; and / or,

[0209] In some implementations, n is selected from the range of 0.001 to 0.005. Positive electrode sheets based on this scheme are used in secondary batteries, resulting in significant improvements in one or more performance characteristics of the secondary battery.

[0210] In some embodiments, (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. Positive electrode sheets based on this scheme are used in secondary batteries, resulting in significant improvements in one or more performance characteristics of the secondary battery.

[0211] In some embodiments, the lattice variation rate of the positive electrode active material is less than 8%, optionally less than 4%. Positive electrode sheets based on this scheme are used in secondary batteries, resulting in significant improvements in one or more performance characteristics of the secondary battery.

[0212] In some embodiments, the Li / Mn antisite defect concentration of the positive electrode active material is below 2%, optionally below 0.5%. Positive electrode sheets based on this scheme are used in secondary batteries, resulting in significant improvements in one or more performance characteristics of the secondary battery.

[0213] In some embodiments, the surface oxygen valence state of the positive electrode active material is below -1.82, optionally between -1.89 and -1.98. Positive electrode sheets based on this design are used in secondary batteries, resulting in significant improvements in one or more performance characteristics of the secondary battery.

[0214] In some embodiments, the compaction density of the positive electrode active material at 3T is 2.0 g / cm³. 3 The above is optional, 2.2 g / cm³. 3 The above describes a method for using positive electrode sheets in secondary batteries, which significantly improves one or more performance characteristics of the secondary batteries.

[0215] In some embodiments, the surface of the positive electrode active material is coated with carbon. Positive electrode sheets based on this design are used in secondary batteries, resulting in significant improvements in one or more performance characteristics of the secondary battery.

[0216] In some implementations, the method for preparing the positive electrode active material includes the following steps:

[0217] 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.

[0218] 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;

[0219] Step (3): Transfer the slurry obtained in step (2) to a spray drying equipment for spray drying and granulation to obtain granules;

[0220] Step (4): Sinter the particles obtained in step (3) to obtain the core Li. a A x Mn 1-y B y P 1-z C z O 4-n D n The core is wherein 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 core is electrically neutral.

[0221] In some embodiments, the stirring in step (1) is carried out at a temperature in the range of 60-120°C, and / or,

[0222] The stirring in step (1) is carried out at a stirring rate of 200-800 rpm.

[0223] 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.

[0224] In some implementations, the grinding and mixing in step (2) is carried out for 8-15 hours.

[0225] In some implementations, the sintering of step (4) is carried out at a temperature range of 600-900°C for 6-14 hours.

[0226] In some embodiments, this application provides a secondary battery including the positive electrode sheet described in any of the above claims.

[0227] In some embodiments, this application provides an electrical device including the aforementioned secondary battery.

[0228] A positive electrode typically includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector, the positive electrode film layer including a positive electrode active material.

[0229] Figure 1 A schematic diagram of a positive electrode sheet according to an embodiment is shown. As shown, a positive electrode sheet includes a positive current collector 11, a positive electrode film layer 13 disposed on at least one surface 112 of the positive current collector 11, and a conductive undercoat layer 12 located between the positive current collector 11 and the positive electrode film layer 13.

[0230] As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0231] 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.).

[0232] In some embodiments, the positive electrode film layer may optionally include a binder. 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.

[0233] In some embodiments, the positive electrode film 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.

[0234] In some embodiments, the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive 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 the positive electrode current collector, and then obtaining the positive electrode sheet after drying, cold pressing and other processes.

[0235] [Negative electrode plate]

[0236] The negative electrode sheet includes a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector, the negative electrode film layer including a negative electrode active material.

[0237] As an example, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0238] 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 material substrate and a metal layer formed on at least one surface of the polymer material 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 material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0239] 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: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc. Silicon-based materials may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials 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.

[0240] In some embodiments, the negative electrode film layer may optionally include a binder. As an example, 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).

[0241] In some embodiments, the negative electrode film may optionally include a conductive agent. As an example, 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.

[0242] In some embodiments, the negative electrode film may optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0243] 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.

[0244] [Electrolytes]

[0245] The electrolyte acts as a conductor of ions between the positive and negative electrodes. This application does not impose specific restrictions on the type of electrolyte; it can be selected according to requirements. For example, the electrolyte can be liquid, gel, or entirely solid.

[0246] In some embodiments, the electrolyte is liquid and includes an electrolyte salt and a solvent.

[0247] In some embodiments, the electrolyte salt may be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate.

[0248] In some embodiments, the solvent may be selected from at least one of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butyl carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0249] In some embodiments, the electrolyte may optionally include additives. As examples, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.

[0250] [Isolation membrane]

[0251] In some embodiments, the secondary battery also includes a separator. This application does not impose any particular limitation on the type of separator; any known porous separator with good chemical and mechanical stability can be selected.

[0252] In some embodiments, the material of the separator can be selected from at least one of glass fiber, nonwoven 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.

[0253] In some implementations, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding or stacking process.

[0254] In some embodiments, the secondary battery may include an outer packaging. This outer packaging may be used to encapsulate the electrode assembly and electrolyte described above.

[0255] 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.

[0256] 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 3 This is an example of a square-structured secondary battery 5.

[0257] In some implementations, refer to Figure 4 The 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.

[0258] 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.

[0259] Figure 5 This is battery module 4, used as an example. (See reference...) Figure 5 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.

[0260] Optionally, the battery module 4 may also include a housing with a receiving space in which a plurality of secondary batteries 5 are received.

[0261] 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.

[0262] Figure 6 and Figure 7 This is battery pack 1 as an example. (See reference...) Figure 6 and Figure 7 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.

[0263] In addition, this application also provides an electrical device, which includes at least one of the 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 may include, but is not limited to, 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.

[0264] As the electrical device, a secondary battery, battery module, or battery pack can be selected according to its usage requirements.

[0265] Figure 8 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.

[0266] Specific embodiments of novel positive electrode active materials

[0267] 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.

[0268] Preparation of primary and secondary batteries

[0269] Example 1

[0270] 1) Preparation of positive electrode active materials

[0271] 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.

[0272] 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 0.001 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).

[0273] 2) Preparation of button cells

[0274] 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 one-sided density of the positive electrode film was 0.02 g / cm³. 2 The compacted density is 2.0 g / cm³. 3 .

[0275] 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. Together with the positive electrode sheet prepared above, they are assembled into a coin cell (hereinafter also referred to as "coin cell") in a coin cell box.

[0276] 3) Preparation of full cells

[0277] The above-mentioned positive electrode active material, conductive agent acetylene black, and binder polyvinylidene fluoride (PVDF) were mixed evenly 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 form a positive electrode film, thus obtaining the positive electrode sheet. The single-sided density of the positive electrode film was 0.04 g / cm³. 2 The compacted density is 2.4 g / cm³. 3 .

[0278] 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 form a negative electrode film, thus obtaining the negative electrode sheet. The single-sided density of the negative electrode film was 0.02 g / cm³. 2 The compacted density is 1.7 g / cm³. 3 .

[0279] 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 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").

[0280] Example 2

[0281] 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.

[0282] Figure 9 The XRD patterns of undoped LiMnPO4 and the cathode active material prepared in Example 2 are shown. As can be seen from the figure, the positions of the main characteristic peaks in the XRD pattern of the cathode active material of Example 2 are consistent with those of undoped LiMnPO4, indicating that the doping process did not introduce impurity phases, and the performance improvement mainly comes from elemental doping rather than impurity phases.

[0283] Figure 10 The EDS spectrum of the positive electrode active material prepared in Example 2 is shown. The dots in the spectrum represent the doping elements. The spectrum shows that the elemental doping is uniform in the positive electrode active material of Example 2.

[0284] Example 3

[0285] 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.

[0286] Example 4

[0287] 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.

[0288] Example 5

[0289] 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.

[0290] Example 6

[0291] 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.

[0292] Example 7

[0293] Except for replacing MgSO4 with CoSO4 in “1) Preparation of positive electrode active material”, everything else is the same as in Example 6.

[0294] Example 8

[0295] Except for replacing MgSO4 with NiSO4 in “1) Preparation of positive electrode active material”, everything else is the same as in Example 6.

[0296] Example 9

[0297] Except for the following changes in “1) Preparation of positive electrode active material”, where the amount of FeSO4·H2O is changed to 0.698 mol, 0.002 mol of Ti(SO4)2 is added when preparing doped manganese oxalate, the amount of Li2CO3 is changed to 0.4955 mol, 0.001 mol of Mo(SO4)3 is replaced with 0.0005 mol of Nb2(SO4)5, H4SiO4 is replaced with H2SO4, and NH4HF2 is converted into NH4HCl2, the rest is the same as in Example 1.

[0298] Example 10

[0299] 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.

[0300] Example 11

[0301] 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.

[0302] Example 12

[0303] 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, everything else is the same as in Example 1.

[0304] Example 13

[0305] 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.

[0306] Example 14

[0307] 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.

[0308] Example 15

[0309] 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.

[0310] Example 16

[0311] 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, 0.1 mol of VCl2 is added when preparing doped manganese oxalate, the amount of Li2CO3 is changed to 0.467 mol, 0.001 mol of Mo(SO4)3 is replaced with 0.005 mol of MgSO4, 0.001 mol of H4SiO4 is replaced with 0.005 mol of H2SO4, and 1.175 mol of 85% phosphoric acid is replaced with 1.171 mol of 85% phosphoric acid, everything else is the same as in Example 1.

[0312] Example 17

[0313] 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, 0.1 mol of VCl2 is added when preparing doped manganese oxalate, the amount of Li2CO3 is changed to 0.492 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.

[0314] Example 18

[0315] 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.

[0316] Example 19

[0317] 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.

[0318] Example 20

[0319] 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.

[0320] Example 21

[0321] 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.

[0322] Example 22

[0323] Except for changing the amount of MnSO4·H2O to 1.5 mol, the amount of FeSO4·H2O to 0.2 mol, and replacing 0.1 mol of CoSO4 with 0.2 mol of NiSO4 in “1) Preparation of positive electrode active material”, the rest is the same as in Example 18.

[0324] Example 23

[0325] 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.

[0326] Example 24

[0327] 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.

[0328] Example 25

[0329] 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.

[0330] Example 26

[0331] 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.

[0332] Example 27

[0333] 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.

[0334] Comparative Example 1

[0335] 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 then ground to obtain the median particle size Dv. 50 Manganese oxalate particles with a diameter of 50-200 nm.

[0336] 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.

[0337] Comparative Example 2

[0338] Except for Comparative Example 1, in which 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 the mixer and thoroughly mixed for 6 hours before being added to the reactor, everything else was the same as in Comparative Example 1.

[0339] Comparative Example 3

[0340] 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.

[0341] Comparative Example 4

[0342] Except for the following changes in “1) Preparation of positive electrode active material”: 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, 0.001 mol of Mo(SO4)3 is replaced with 0.005 mol of Nb2(SO4)5, 0.999 mol of phosphoric acid is changed to 1 mol, 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.

[0343] Comparative Example 5

[0344] 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.

[0345] Comparative Example 6

[0346] 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.

[0347] Comparative Example 7

[0348] Except for the following changes in “1) Preparation of positive electrode active material”, where the amounts of MnSO4·H2O are changed to 1.4 mol, FeSO4·H2O to 0.6 mol, Li2CO3 to 0.534 mol, 0.001 mol Mo(SO4)3 to 0.001 mol MgSO4, phosphoric acid to 0.88 mol, H4SiO4 to 0.12 mol, and NH4HF2 to 0.025 mol, the rest are the same as in Example 1.

[0349] Comparative Example 8

[0350] 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.

[0351] II. Properties of Positive Electrode Active Materials and Battery Performance Testing Methods

[0352] 1. Methods for measuring lattice change rate

[0353] 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 1° / min. 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).

[0354] 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.

[0355] 2. Method for measuring the concentration of Li / Mn antisite defects

[0356] 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.

[0357] 3. Surface oxygen valence state measurement method

[0358] 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.

[0359] 4. Compacted density measurement method

[0360] 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.

[0361] 5. Method for measuring the amount of Mn (and Mn-doped Fe) dissolved after cycling

[0362] 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.

[0363] 6. Method for measuring the initial specific capacity of button cells

[0364] 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.

[0365] 7.3C Charging Constant Current Ratio Measurement Method

[0366] Under a constant temperature of 25℃, a fresh full battery is allowed 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, allowed 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%.

[0367] The higher the constant current ratio during 3C charging, the better the battery's rate performance.

[0368] 8. Full battery 45℃ cycle performance test

[0369] 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, and then 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.

[0370] 9. Full battery gas expansion test at 60°C

[0371] Full cells at 100% State of Charge (SOC) were stored at 60°C. The open-circuit voltage (OCV) and internal resistance (IMP) of the cells 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 displacement method. The 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 process, measure the weight F2 of the battery cell at this moment, and the buoyancy F of the battery cell. 浮 That is, F1-F2, and then according to Archimedes' principle, F 浮 =ρ×g×V 排 The cell volume V is calculated to be V = (F1 - F2) / (ρ × g).

[0372] 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.

[0373] After 30 days of storage, the cell volume was measured, and the percentage increase in cell volume after storage was calculated relative to the cell volume before storage.

[0374] In addition, measure the residual capacity of the battery cell. Charge the full battery at 1C to 4.3V within the range of 2.5V to 4.3V, then charge it at a constant voltage of 4.3V until the current is less than or equal to 0.05mA. Let it stand for 5 minutes, and record the charging capacity at this point as the residual capacity of the battery cell.

[0375] 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.

[0376]

[0377]

[0378]

[0379]

[0380]

[0381]

[0382]

[0383]

[0384]

[0385] As can be seen from Tables 2, 4, 6 and 8 above, each positive electrode active material in the embodiments of this application has achieved better results than the comparative ratio in one or even all aspects of cycle performance, high temperature stability, specific capacity and compaction density.

[0386] Comparing Examples 18-20 and 23-25, it can be seen that, with other elements being equal, (1-y):y being in the range of 1 to 4 can further improve the energy density and cycle performance of the secondary battery.

[0387] Specific embodiments of the novel conductive undercoating

[0388] 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.

[0389] To distinguish them from the specific embodiments of the novel cathode material mentioned above, the specific embodiments of the novel conductive undercoating are numbered with the suffix "P".

[0390] Example 1P (Positive electrode active material of Example 1)

[0391] 1. Provide the first polymer

[0392] In the following embodiments, the first polymer is a hydrogenated carboxylated nitrile butadiene rubber containing a first monomer unit, a second monomer unit, a third monomer unit, and a fourth monomer unit. The weight percentages of the first monomer unit, the second monomer unit, the third monomer unit, and the fourth monomer unit in the polymer, as well as the weight-average molecular weight of the first polymer, are shown in Table 1P.

[0393] The first monomer unit is the monomer unit represented by Equation 1;

[0394]

[0395] The second monomer unit is selected from at least one of the groups consisting of monomer units represented by Equation 2 and monomer units represented by Equation 3.

[0396] One kind

[0397]

[0398] The third monomer unit is selected from at least one of the groups consisting of monomer units represented by Equation 4 and monomer units represented by Equation 5.

[0399] A sort of;

[0400]

[0401] The fourth monomer unit is the monomer unit represented by Equation 6:

[0402]

[0403] In this embodiment, R 1 R 2 and R 3 Both are H, R 4 It is n-butyl.

[0404] Table 1P

[0405]

[0406] 2. Preparation of aluminum foil with conductive undercoating

[0407] The first polymer, the first water-based binder (polyacrylic acid-acrylate copolymer, weight average molecular weight 340,000) and the first conductive agent (SP) are mixed in a weight ratio of 15:40:45, dissolved / dispersed in deionized water to prepare a conductive base coating slurry.

[0408] A conductive undercoating slurry is applied to both sides of an aluminum foil, and after drying, a conductive undercoating with a thickness of 5 μm is formed on each side. An aluminum foil with a conductive undercoating is obtained.

[0409] 3) Preparation of positive electrode sheet

[0410] The positive electrode active material (Li) from Example 1 above 0.994 Mo 0.001 Mn 0.65 Fe 0.35 P 0.999 Si 0.001 O 3.999 F 0.001A positive electrode slurry is prepared by uniformly mixing acetylene black (a conductive agent) and polyvinylidene fluoride (PVDF) (a binder) in an N-methylpyrrolidone solvent system at a weight ratio of 92:2.5:5.5. The positive electrode slurry is then coated onto both sides of an aluminum foil with a conductive undercoat, dried, and cold-pressed to form a positive electrode film, thus obtaining the positive electrode sheet. The single-sided density of the positive electrode film is 0.025 g / cm³. 2 The compacted density is 2.4 g / cm³. 3 .

[0411] 4) Preparation of negative electrode sheet

[0412] 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 form a negative electrode film, thus obtaining the negative electrode sheet. The one-sided density of the negative electrode film was 0.013 g / cm³. 2 The compacted density is 1.7 g / cm³. 3 .

[0413] 5) Assembly of the full battery

[0414] 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").

[0415] The weight of the positive electrode active material in a single full cell is 565.66g; the weight of the negative electrode active material is 309.38g.

[0416] Examples 2P-27P (Positive electrode active materials of Examples 2-27)

[0417] The difference between Examples 2P to 27P and Example 1 lies in step 3). The parameters of other steps are the same as those in Example 1P.

[0418] In step 3), the positive electrode active materials used in Examples 2P to 27P are the same as those in Examples 2 to 27 above.

[0419] Comparative examples 1P-9P (without conductive undercoat)

[0420] The difference between Comparative Examples 1P-9P and Example 1P lies in steps 2) and 3). The other step parameters are the same as those in Example 1P.

[0421] In Comparative Examples 1P-9P, in steps 2) and 3), aluminum foil with a conductive undercoat was not prepared. Instead, the positive electrode slurry was directly coated onto the aluminum foil and dried and cold-pressed to form a positive electrode film, thus obtaining a positive electrode sheet.

[0422] The positive electrode active materials used in Comparative Examples 1P-8P in step 3) are the same as those used in Comparative Examples 1-8 above.

[0423] In step 3), the positive electrode active material used in Comparative Example 9P is the same as that in Example 1 above.

[0424] Comparative Example 10P (without the first polymer)

[0425] The difference between Comparative Example 10P and Example 1P lies in step 2). The other steps and parameters are the same as in Example 1P.

[0426] In Comparative Example 10P, in step 2), the first aqueous binder (polyacrylic acid-acrylate copolymer) and the first conductive agent (SP) were mixed in a weight ratio of 40:45, dissolved / dispersed in deionized water, and a conductive primer slurry was prepared. The conductive primer slurry was coated onto an aluminum foil, and after drying, a conductive primer coating with a thickness of 5 μm was formed. An aluminum foil with a conductive primer coating was obtained.

[0427] Comparative Example 11P (replacing the first polymer with the I polymer)

[0428] The difference between Comparative Example 11P and Example 1P lies in step 2). The other steps and parameters are the same as in Example 1P.

[0429] In Comparative Example 11P, in step 2), the first polymer, the first aqueous binder (polyacrylic acid-acrylate copolymer), and the first conductive agent (SP) were mixed in a weight ratio of 15:40:45 and dissolved / dispersed in deionized water to prepare a conductive undercoating slurry. The conductive undercoating slurry was coated onto an aluminum foil, and after drying, a conductive undercoating with a thickness of 5 μm was formed. An aluminum foil with a conductive undercoating was obtained.

[0430] The difference between polymer I and polymer I lies in their composition. The composition of polymer I and its weight-average molecular weight are shown in Table 2P below.

[0431] Table 2P

[0432]

[0433] Comparative Example 12P (replacing the first water-based adhesive with the first adhesive)

[0434] The difference between Comparative Example 12P and Example 1P lies in step 2). The other steps and parameters are the same as in Example 1P.

[0435] In Comparative Example 12P, in step 2), the first polymer, the first binder (polyacrylic acid, weight average molecular weight 350,000), and the first conductive agent (SP) were mixed in a weight ratio of 15:40:45 and dissolved / dispersed in deionized water to prepare a conductive undercoating slurry. The conductive undercoating slurry was coated onto an aluminum foil, and after drying, a conductive undercoating with a thickness of 5 μm was formed. An aluminum foil with a conductive undercoating was obtained.

[0436] Analysis and testing

[0437] 1. Adhesion test of positive electrode sheet

[0438] Figure 2 (a) through (d) show the flowchart of the peel test. Figure 2 As shown in (a), a steel plate 510 is first provided, with dimensions of 30mm wide × 100mm long. Figure 2 As shown in (b), a double-sided tape 520 is then provided, with dimensions of 20mm wide × 30mm long. The double-sided tape 520 is attached to the steel plate 510, with one wide edge of the double-sided tape 520 aligned with one wide edge of the steel plate 510. Figure 2 As shown in (c), a test electrode 530 is then provided, with dimensions of 20mm wide × 180mm long. The test electrode 530 is placed over the double-sided adhesive 520 (aligned on both sides), with the coated side of the electrode 530 facing the double-sided adhesive 520. Because the length of the test electrode 530 is greater than the length of the double-sided adhesive 520, a portion of the test electrode 530 is not bonded to the double-sided adhesive. Figure 2 As shown in (d), the steel plate 510 is fixed on the base of the tensile testing machine. A clamp holds the end of the electrode 530 to be tested that is not bonded to the double-sided adhesive. The clamp is then stretched towards the other end (as indicated by the arrow). The direction of the stretching force is perpendicular to the steel plate 510 and maintains a certain distance from its surface. While stretching the electrode outwards from the paper, the steel plate moves upwards to keep the stretching direction perpendicular to the electrode peeling position. During the stretching process, the electrode 530 is gradually peeled off the steel plate. The stretching speed of the clamp is 50 mm / min. The tension of the clamp is recorded during the stretching process. After the tension stabilizes, a further 40 mm peeling length is performed, and the average tension at this peeling length is taken as the adhesive force (in N).

[0439] 2. Battery DC resistance test

[0440] At 25℃, the battery was charged to 4.3V using a constant current and constant voltage at 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 charged to 4C constant current (I mDischarge for 30 seconds (collect voltage data every 1 second), and record the initial voltage U0 and the voltage U after 30 seconds of discharge. 30 The DC impedance (DCR) value is calculated using the following formula.

[0441] DC impedance value = (U0 - U 30 ) / I m

[0442] The DC resistance value of the battery in Example 1P is 100%. The changes in other examples and comparative examples relative to Example 1P are expressed as percentages.

[0443] 3. Number of cycles in which the battery retains 80% of its capacity at 45°C (hereinafter referred to as "80% capacity cycles")

[0444] 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, and then 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.

[0445] Following the above testing and analysis methods, the bonding strength of the positive electrode sheets prepared in Examples 1P to 27P and Comparative Examples 9P to 12P, the DC impedance value of the battery, and the number of cycles with 80% capacity retention at 45°C were tested. The results are shown in Table 3P below.

[0446] Table 3P

[0447]

[0448]

[0449] As shown in Table 3P, the positive electrode sheets of Examples 1P to 27P exhibited improved adhesion, and the batteries of Examples 1P to 27P exhibited reduced DC resistance and improved cycle capacity retention.

[0450] Comparative Example 9P (without conductive primer), Comparative Example 10P (without first polymer), Comparative Example 11P (replacing first polymer with I polymer), and Comparative Example 12P (replacing first water-based adhesive with I adhesive) failed to achieve the above-mentioned improved effect.

[0451] Examples 28P-34P (Compositional variations of the first polymer)

[0452] The difference between Examples 28P to 34P and Example 1P lies in step 2). The other steps and parameters are the same as in Example 1P.

[0453] In step 2), the composition of the first polymer used in Examples 28P to 34P differs from that in Example 1P, specifically in the weight percentages of the second and third monomer units. The composition of the first polymer in Examples 28P to 34P is shown in Table 4P below.

[0454] Table 4P

[0455]

[0456] Examples 35P to 39P (variation of conductive undercoat thickness)

[0457] The difference between Examples 35P to 39P and Example 1P lies in step 2). The other steps and parameters are the same as in Example 1P.

[0458] In step 2), the thickness of the conductive undercoat layer in Examples 28P to 34P is different from that in Example 1P, as detailed in Table 5P.

[0459] Table 5P

[0460]

[0461] Examples 40P to 45P (variations in the composition of the conductive undercoat)

[0462] The difference between Examples 40P to 45P and Example 1P lies in step 2). The other steps and parameters are the same as in Example 1P.

[0463] In step 2), the composition of the conductive base coating (the ratio of the first polymer, the first water-based binder, and the first conductive agent) of Examples 40P to 45P is different from that of Example 1, as detailed in Table 6P.

[0464] Table 6P

[0465]

[0466] Following the above testing and analysis methods, the bonding force of the positive electrode sheets prepared in Examples 1P, 28P to 45P, the DC impedance value of the battery, and the number of cycles with 80% capacity retention at 45°C were tested. The results are shown in Table 7P below.

[0467] Table 7P

[0468]

[0469]

[0470] As shown in Table 7P, the positive electrode sheets of Examples 28P to 45P exhibited improved adhesion, and the batteries of Examples 28P to 45P showed reduced DC resistance and improved cycle capacity retention. When the value of M3 / (M2+M3) was 0% to 5%, the mass impedance of the battery showed a significant reduction.

[0471] Examples 46P-54P

[0472] The difference between Examples 46P-54P and Example 1P lies in step 3). The parameters of other steps are the same as those in Example 1P.

[0473] In step 3) of Examples 46P-54P, the positive electrode active material (Li) from Example 1 above is used. 0.994 Mo 0.001 Mn 0.65 Fe 0.35 P 0.999 Si 0.001 O 3.999 F 0.001 A positive electrode slurry was prepared by uniformly mixing the conductive agent acetylene black, the binder polyvinylidene fluoride (PVDF), the dispersant, and the wetting agent in an N-methylpyrrolidone solvent system at a weight ratio of (92-Y1-Y2):2.5:5.5:Y1:Y2. The positive electrode slurry was then coated onto both sides of an aluminum foil with a conductive undercoat, dried, and cold-pressed to form a positive electrode film, resulting in the positive electrode sheet. The single-sided density of the positive electrode film was 0.025 g / cm³. 2 The compacted density is 2.4 g / cm³. 3 .

[0474] The wetting agent for Examples 46P-54P was maleic anhydride-styrene copolymer (molecular weight 5000). The dispersant for Examples 46P-54P was a second polymer.

[0475] In the positive electrode of Examples 46P-54P, the first polymer (from the conductive undercoating layer) and the second polymer (from the positive electrode film layer)

[0476] The second polymer is a hydrogenated nitrile butadiene rubber containing a fifth monomer unit, a sixth monomer unit, and a seventh monomer unit. The weight percentages of the five, sixth, and seventh monomer units in the polymer, as well as the weight-average molecular weight of the second polymer, are shown in Table 8P.

[0477] The fifth monomer unit is the monomer unit represented by Equation 1;

[0478]

[0479] The sixth monomer unit is selected from at least one of the groups consisting of the monomer units represented by Equation 8 and the monomer units represented by Equation 9.

[0480] One kind

[0481]

[0482]

[0483] The seventh monomer unit is selected from the group consisting of the monomer units represented by Equation 10 and Equation 11.

[0484] One less;

[0485]

[0486] Table 8P

[0487]

[0488] Examples 46P-54P specify the proportions of dispersant (second polymer) Y1 and wetting agent (maleic anhydride-styrene copolymer) Y2 used in step 3), as well as their ratio Y. 1 / Y2 is shown in Table 9P below.

[0489] In the positive electrode sheet of Examples 46P-54P, the mass ratio of the first polymer (from the conductive undercoating layer) and the second polymer (from the positive electrode film layer) is 2:1.

[0490] Table 9P

[0491]

[0492]

[0493] According to the above detection and analysis methods, the bonding force of the positive electrode sheet prepared in Examples 1P and 46P-54P above, the DC impedance value of the battery, and the number of cycles with 80% capacity retention at 45°C were tested. The results are shown in Table 10P below.

[0494] Table 10P

[0495] Electrode adhesion DC impedance Number of cycles Example 1P 10 100％ 765 Example 46P 74 93％ 862 Example 47P 60 95％ 870 Example 48P 176 124％ 310 Example 49P 183 160％ 208 Example 50P 100 100％ 700 Example 51P 105 99％ 930 Example 52P 110 98％ 881 Example 53P 108 106％ 490 Example 54P 100 116％ 110

[0496] As shown in Table 10P, based on the above-mentioned novel conductive undercoating, the combination of a novel positive electrode film containing dispersants and wetting agents can further improve the adhesion of the electrode sheets and / or reduce the DC impedance of the battery and / or improve the cycle performance of the battery.

[0497] Based on the experimental data above, this application provides a novel positive electrode sheet, a secondary battery, and an electrical device. The positive electrode sheet includes a novel positive electrode active material and a novel conductive undercoating.

[0498] The new positive electrode active materials have achieved better performance in one or all of the following aspects: cycle performance, high temperature stability, specific capacity and compaction density.

[0499] The new conductive undercoat coating achieves superior performance in one or all of the following aspects: improving electrode adhesion, reducing battery DC impedance, and improving battery cycle performance.

[0500] 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 sheet, comprising a positive current collector, a positive electrode film layer disposed on at least one surface of the positive current collector, and a conductive undercoat layer located between the positive current collector and the positive electrode film layer, wherein, The positive electrode film includes a chemical formula Li a A x Mn 1-y B y P 1-z C z O 4-n D n The positive electrode active material comprises, wherein 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 conductive undercoat includes a first polymer, a first water-based binder, and a first conductive agent. The first 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; 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; and The fourth monomer unit represented by Equation 6, R 1 R 2 R 3 Each group independently represents H, carboxyl, ester, and the following substituted or unsubstituted groups: C1-C10 alkyl, C1-C10 alkoxy, C2-C10 alkenyl, C6-C10 aryl, R 4 The following groups, whether substituted or unsubstituted, represent H: alkyl (C1-C10), alkoxy (C1-C10), alkenyl (C2-C10), and aryl (C6-C10). Formula 1 Formula 2 Formula 3 Formula 4 Formula 5 Formula 6; Based on the total mass of the first polymer, the mass percentage of the first monomer unit is M1, where M1 is 10% to 55%; the mass percentage of the second monomer unit is M2, where M2 is 40% to 80%; the mass percentage of the third monomer unit is M3, where M3 is 0.001% to 2%; and the mass percentage of the fourth monomer unit is M4, where M4 is 0.1% to 10%.

2. The positive electrode sheet according to claim 1, wherein, Based on the total mass of the first 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 fourth monomer unit is M4, where M4 is 0.1% to 1%.

3. The positive electrode sheet according to claim 1, wherein, M3 / (M2+M3) is 0.001%~5%.

4. The positive electrode sheet according to claim 1, wherein, M3 / (M2+M3) is 0.001%~1%.

5. The positive electrode sheet according to claim 1, wherein, The first polymer is one or more of hydrogenated nitrile butadiene rubber and hydrogenated carboxylated nitrile butadiene rubber; and / or, The weight-average molecular weight of the first polymer is 50,000 to 1,500,000.

6. The positive electrode sheet according to claim 1, wherein, The weight-average molecular weight of the first polymer is 200,000 to 400,000.

7. The positive electrode sheet according to claim 1, wherein, The first waterborne adhesive comprises one or more of waterborne polyacrylic acid resin and its derivatives, waterborne amino-modified polypropylene resin and its derivatives, and polyvinyl alcohol and its derivatives; and / or, The weight-average molecular weight of the first water-based adhesive is 200,000 to 1,500,000.

8. The positive electrode sheet according to claim 1, wherein, The first waterborne adhesive comprises a waterborne acrylic-acrylate copolymer; and / or, The weight-average molecular weight of the first water-based adhesive is 300,000 to 400,000.

9. The positive electrode sheet according to claim 1, wherein, The first conductive agent includes one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

10. The positive electrode sheet according to claim 1, wherein, The first conductive agent includes one or more of carbon nanotubes, graphene, and carbon nanofibers.

11. The positive electrode sheet according to claim 1, wherein, Based on the total mass of the conductive undercoating layer The mass percentage of the first polymer is X1, where X1 is 5% to 20%; and / or, The first water-based adhesive has a mass percentage content of X2, where X2 is 30%~80%; and / or, The mass percentage of the first conductive agent is X3, where X3 is 10% to 50%.

12. The positive electrode sheet according to claim 11, wherein, X1 is 5%~10%; and / or, X2 is 40%~50%; and / or, X3 is 40%~50%.

13. The positive electrode sheet according to claim 1, wherein, The thickness of the conductive undercoat is 1μm to 20μm.

14. The positive electrode sheet according to claim 1, wherein, The thickness of the conductive undercoat is 3μm to 10μm.

15. The positive electrode sheet according to claim 1, wherein, The positive electrode film layer also includes one or more of the following: wetting agent and dispersant.

16. The positive electrode sheet according to claim 15, wherein, The positive electrode film also includes a wetting agent and a dispersant.

17. The positive electrode sheet according to claim 15, wherein, The surface tension of the wetting agent is 20mN / m to 40mN / m.

18. The positive electrode sheet according to claim 15, wherein, The wetting agent includes at least one of the following functional groups: -CN, -NH2, -NH-, -N-, -OH, -COO-, -C(=O)-OC(=O)-.

19. The positive electrode sheet according to claim 15, wherein, The wetting agent includes one or more selected from small molecule organic solvents and low molecular weight polymers.

20. The positive electrode sheet according to claim 19, wherein, The small molecule organic solvent includes one or more of the following: alkanolamines, alcohols, and nitriles.

21. The positive electrode sheet according to claim 20, wherein, The alkanolamine compounds have 1 to 16 carbon atoms.

22. The positive electrode sheet according to claim 20, wherein, The alkanolamine compounds have 2 to 6 carbon atoms.

23. The positive electrode sheet according to claim 19, wherein, The low molecular weight polymer includes one or more of maleic anhydride-styrene copolymer, polyvinylpyrrolidone, and polysiloxane.

24. The positive electrode sheet according to claim 19, wherein, The weight-average molecular weight of the low molecular weight polymer is below 6000.

25. The positive electrode sheet according to claim 19, wherein, The weight-average molecular weight of the low molecular weight polymer is 3000~6000.

26. The positive electrode sheet according to claim 15, wherein, The dispersant comprises a second polymer, and the second polymer comprises: The fifth monomer unit represented by Equation 7; A sixth monomeric unit selected from at least one of the monomeric units represented by Formula 8 and the monomeric units represented by Formula 9; and A seventh monomer unit selected from at least one of the monomer units represented by Formula 10 and the monomer units represented by Formula 11. Formula 7 Formula 8 Formula 9 Formula 10 Formula 11.

27. The positive electrode sheet according to claim 26, wherein, Based on the total mass of the second polymer, The fifth monomer unit has a mass percentage content of M5, where M5 is 10%~55%; and / or, The sixth monomer unit has a mass percentage content of M6, where M6 is 40%~80%; and / or, The mass percentage of the seventh monomer unit is M7, and M7 is 0%~10%.

28. The positive electrode sheet according to claim 27, wherein, M5 is 25%~55%; and / or, M6 is 50%~70%; and / or, M7 is 0.001%~2%.

29. The positive electrode sheet according to claim 27, wherein, M7 / (M6+M7) is 0%~5%.

30. The positive electrode sheet according to claim 27, wherein, M7 / (M6+M7) is 0.001%~1%.

31. The positive electrode sheet according to claim 26, wherein, The second polymer is hydrogenated nitrile butadiene rubber; and / or, The weight-average molecular weight of the second polymer is 50,000 to 500,000.

32. The positive electrode sheet according to claim 26, wherein, The weight-average molecular weight of the second polymer is 150,000 to 350,000.

33. The positive electrode sheet according to claim 15, wherein, Based on the total mass of the positive electrode film layer The dispersant has a mass percentage content of Y1, where Y1 is 0.05%~1%; and / or, The mass percentage of the wetting agent is Y2, and Y2 is 0.05%~2%.

34. The positive electrode sheet according to claim 33, wherein, Y1 is 0.1%~0.5%; and / or, Y2 ranges from 0.2% to 0.8%.

35. The positive electrode sheet according to claim 33, wherein, Y1 / Y2 is 0.05~20.

36. The positive electrode sheet according to claim 33, wherein, Y1 / Y2 is 0.1~1.

37. The positive electrode sheet according to claim 33, wherein, Y1 / Y2 is 0.3~0.

8.

38. The positive electrode sheet according to claim 26, wherein, In the positive electrode sheet, the mass ratio of the first polymer to the second polymer is 1.5 to 5.

39. The positive electrode sheet according to claim 26, wherein, In the positive electrode sheet, the mass ratio of the first polymer to the second polymer is 2 to 3.

40. The positive electrode sheet according to claim 1, wherein, A includes any one of Zn, Al, Na, K, Mg, Nb, Mo, and W; B includes at least two of Ti, V, Zr, Fe, Ni, Mg, Co, Ga, Sn, Sb, Nb, and Ge; C includes any one of B (boron), S, Si, and N; and D includes any one of S, F, Cl, and Br.

41. The positive electrode sheet 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.

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

43. The positive electrode sheet 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.

44. The positive electrode sheet according to claim 1, wherein, y is selected from the range of 0.25 to 0.

5.

45. The positive electrode sheet 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.

46. ​​The positive electrode sheet according to claim 45, wherein, (1-y): y is in the range of 1.5 to 3.

47. The positive electrode sheet according to claim 45, wherein, a:x is in the range of 190 to 998.

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

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

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

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

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

82.

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

98.

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

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

56. The positive electrode sheet according to any one of claims 1-55, wherein, The surface of the positive electrode active material is coated with carbon.

57. A secondary battery comprising a positive electrode sheet according to any one of claims 1-56.

58. An electrical device comprising a secondary battery according to claim 57.

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