A positive electrode sheet, a battery, and an electric device

Abstract

The application provides a positive electrode sheet, a battery and a power utilization device. The positive electrode sheet of the application comprises a positive electrode current collector and a positive electrode film layer arranged on at least one surface of the positive electrode current collector, the positive electrode film layer comprises a positive electrode active material, the positive electrode active material comprises a Ni element, an Fe element, an Mn element and an optional Al element; and the positive electrode sheet satisfies: 0 Ni / (C Ni +C Fe +C Mn +C Al )≤90.10%.

Description

Technical Field

[0001] This application relates to the field of secondary battery technology, and more particularly to a positive electrode, a 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 safety performance. Summary of the Invention

[0003] This application was made in view of the above-mentioned problems, and its object is to provide a positive electrode, a battery, and an electrical device. Using the positive electrode of this application can improve the safety performance of the battery.

[0004] To achieve the above objectives, a first aspect of this application provides a positive electrode sheet, including a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector, the positive electrode film layer including a positive electrode active material, the positive electrode active material comprising Ni, Fe, Mn and optionally Al elements;

[0005] Furthermore, the positive electrode plate satisfies:

[0006] 0 < C Ni / (C Ni +C Fe +C Mn +C Al ≤90.10%;

[0007] Wherein, the C Ni The mass content of Ni element in the positive electrode film layer, the C Fe The mass content of Fe element in the positive electrode film layer, the C Mn The mass content of Mn element in the positive electrode film layer, the C Al The mass content of Al element in the positive electrode film layer.

[0008] Ni is a negative factor for battery safety performance. In addition, Fe, Mn and Al have the effect of improving thermal stability. This application can improve battery safety performance by controlling the mass ratio of Ni in Ni, Fe, Mn and Al in the positive electrode film layer within the above range.

[0009] In any embodiment, the positive electrode sheet satisfies: 2.88% ≤ C Ni / (C Ni +CFe +C Mn +C Al ≤86.10%.

[0010] Therefore, by controlling the mass ratio of Ni element in the positive electrode film layer among Ni, Fe, Mn and Al elements within the above-mentioned range, this application enables the battery to have higher energy density and higher safety.

[0011] In any embodiment, the positive electrode active material includes a first positive electrode active material; the first positive electrode active material comprises the compound LiNi. b Co d Mn e M f O2; wherein M includes one or more elements selected from Mn, Al, Mg, Ca, Na, Ti, W, Zr, Sr, Cr, Zn, Ba, B, S, and Y, and may optionally include Mg and / or Al; b is 0.314-0.970; d is 0-0.320, and may optionally be 0.047-0.320; e is 0.006-0.390; and the sum of b, d, e, and f is 1 and f is greater than or equal to 0.

[0012] In any embodiment, the first positive electrode active material satisfies: 1.65% ≤ m × b ≤ 79.10%, or optionally 1.65% ≤ m × b ≤ 73.87%, where m is the mass content of the first positive electrode active material in the positive electrode active material.

[0013] Therefore, the positive electrode sheet of this application has higher thermal stability and lower oxygen release.

[0014] In any embodiment, in the first positive electrode active material, the molar proportion of Al element in the elements other than Li and O element is 0-5%, optionally 0.5%-4%; and / or,

[0015] The molar proportion of Mg in the elements other than Li and O is 0-3%, and can be selected from 0.5% to 2.0%.

[0016] Appropriate doping with Al and / or Mg elements is beneficial to improving the thermal stability of the positive electrode sheet of this application.

[0017] In any embodiment, the positive electrode active material further includes a second positive electrode active material; the second positive electrode active material comprises the compound Li. a A x Mn 1-y B y P 1-z C z O 4-n Dn 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 0.9-1.1; x is 0-0.1; y is 0.001-0.5; z is 0.001-0.1; and n is 0-0.1.

[0018] In any embodiment, the second positive electrode active material includes a core and a shell covering the core; the core comprises the compound Li. a A x Mn 1-y B y P 1-z C z O 4-n D n The shell contains carbon.

[0019] In any embodiment, the second positive electrode active material includes a core and a shell covering the core, the shell including a first coating layer covering the core, a second coating layer covering the first coating layer, and a third coating layer covering the second coating layer; the core contains the compound Li. a A x Mn 1-y B y P 1-z C z O 4-n D n The first coating layer contains crystalline pyrophosphate Li g EP2O7 and / or E h (P2O7) i The second coating layer contains crystalline phosphate X j PO4, the third coating layer contains carbon;

[0020] Among them, the crystalline pyrophosphate Li g EP2O7 and E h (P2O7) iEach of E in the above contexts independently includes one or more elements selected from Fe, Ni, Mg, Co, Cu, Zn, Ti, Ag, Zr, Nb, and Al; each of X in the above contexts includes one or more elements selected from Li, Fe, Ni, Mg, Co, Cu, Zn, Ti, Ag, Zr, Nb, and Al; each of g in the above contexts is greater than 0 and less than or equal to 2; each of h in the above contexts is greater than 0 and less than or equal to 4; each of i in the above contexts is greater than 0 and less than or equal to 3; and each of j in the above contexts is greater than 0 and less than or equal to 3.

[0021] In any embodiment, the positive electrode active material is composed of the first positive electrode active material and the second positive electrode active material.

[0022] Therefore, this application improves the safety performance of the battery by using a combination of the first positive electrode active material and the second positive electrode active material.

[0023] A second aspect of this application also provides a battery, including the positive electrode of the first aspect of this application.

[0024] Therefore, this application can improve the safety performance of the battery by controlling the mass ratio of Ni element in Ni, Fe, Mn and Al elements in the positive electrode film layer.

[0025] In any embodiment, the battery further includes an electrolyte comprising an electrolyte salt; and the battery satisfies: 0 < ρ × m × b ≤ 79.1%, where ρ is the molar concentration of the electrolyte salt in the electrolyte, in mol / L; and m is the mass content of the first positive electrode active material in the positive electrode active material.

[0026] Therefore, commonly used electrolyte salts are easily decomposed, and the safety of the battery can be further improved by controlling the range of the product of ρ, m, and b.

[0027] In any embodiment, the electrolyte salt includes one or more of LiPF6, LiBF4, LiN(SO2F)2, LiN(CF3SO2)2, LiClO4, LiAsF6, LiB(C2O4)2 and LiBF2C2O4, and optionally includes one or more of LiPF6, LiN(SO2F)2 and LiN(CF3SO2)2.

[0028] A third aspect of this application provides an electrical device including the battery of the second aspect of this application. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of a secondary battery according to one embodiment of this application.

[0030] Figure 2 yes Figure 1An exploded view of a secondary battery according to one embodiment of this application is shown.

[0031] Figure 3 This is a schematic diagram of a battery module according to one embodiment of this application.

[0032] Figure 4 This is a schematic diagram of a battery pack according to one embodiment of this application.

[0033] Figure 5 yes Figure 4 An exploded view of a battery pack according to one embodiment of this application is shown.

[0034] Figure 6 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.

[0035] Explanation of reference numerals in the attached figures:

[0036] 1 Battery pack; 2 Upper housing; 3 Lower housing; 4 Battery module; 5 Secondary battery; 51 Housing; 52 Electrode assembly; 53 Top cover assembly. Detailed Implementation

[0037] The following detailed description, with appropriate reference to the accompanying drawings, specifically discloses embodiments of the positive electrode, secondary battery, battery module, battery pack, and power-consuming 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 for the purpose of enabling those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0038] 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.

[0039] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0040] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0041] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, if a method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, if it is mentioned that the method may also include step (c), it means 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.

[0042] 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.

[0043] 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).

[0044] [Rechargeable Battery]

[0045] 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.

[0046] 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.

[0047] [Positive electrode plate]

[0048] One embodiment of this application provides a positive electrode sheet, including a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector, the positive electrode film layer including a positive electrode active material, the positive electrode active material comprising Ni, Fe, Mn and optionally Al elements;

[0049] Furthermore, the positive electrode plate satisfies:

[0050] 0 < C Ni / (C Ni +C Fe +C Mn +C Al ≤90.10%;

[0051] Wherein, the C Ni The mass content of Ni element in the positive electrode film layer, the C Fe The mass content of Fe element in the positive electrode film layer, the C Mn The mass content of Mn element in the positive electrode film layer, the C Al The mass content of Al element in the positive electrode film layer.

[0052] Although the mechanism is not yet clear, the applicant unexpectedly discovered that Ni is a negative factor in battery safety performance, while Fe, Mn and Al have the effect of improving thermal stability. The applicant can improve battery safety performance by controlling the mass ratio of Ni in the positive electrode film layer among Ni, Fe, Mn and Al within the above range.

[0053] In some embodiments, the positive electrode sheet satisfies: 2.88% ≤ C Ni / (C Ni +C Fe +C Mn +C Al )≤86.10%, for example, C Ni / (C Ni +C Fe +C Mn +C Al The range is 3%, 4%, 7%, 10%, 12%, 15%, 17%, 20%, 21%, 23%, 25%, 27%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 77%, 80%, 82%, 85%, 87%, 88%, 90%, and any of the above values.

[0054] Therefore, by controlling the mass ratio of Ni element in the positive electrode film layer among Ni, Fe, Mn and Al elements within the above-mentioned range, this application enables the battery to have higher energy density and higher safety.

[0055] In some embodiments, the positive electrode active material includes a first positive electrode active material; the first positive electrode active material comprises the compound LiNi. b Co d Mn e M fO2; wherein M includes one or more elements selected from Mn, Al, Mg, Ca, Na, Ti, W, Zr, Sr, Cr, Zn, Ba, B, S, and Y, and may optionally include Mg and / or Al; b is 0.314-0.970, for example, 0.400, 0.500, 0.600, 0.700, 0.800, 0.900, 0.950, and any combination of the above values; d is 0-0.320, optionally 0.047-0.320, for example, 0.0 The range of values ​​including 70, 0.090, 0.100, 0.150, 0.200, 0.250, 0.300, 0.310, 0.320, and any of the above values; where e is 0.006-0.390, for example, 0.008, 0.010, 0.050, 0.100, 0.150, 0.200, 0.250, 0.300, 0.320, 0.350, 0.370, and any of the above values; and the sum of b, d, e, and f is 1, and f is greater than or equal to 0.

[0056] In some embodiments, the first positive electrode active material satisfies: 1.65% ≤ m×b ≤ 79.10%, which can be optionally 1.65% ≤ m×b ≤ 73.87%. For example, m×b can be a range of 2%, 3%, 5%, 7%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 50%, 60%, 65%, 70%, 71%, 72%, 73%, 75%, 76%, 78%, and any of the above values, where m is the mass content of the first positive electrode active material in the positive electrode active material.

[0057] Therefore, the positive electrode sheet of this application has higher thermal stability and lower oxygen release.

[0058] In some embodiments, in the first positive electrode active material, the molar proportion of Al in the elements other than Li and O is 0-5%, optionally 0.5%-4%, for example 0.2%, 0.7%, 1%, 2%, 3%, 4%, 5%, and any range of the above values; and / or,

[0059] The molar proportion of Mg in the elements other than Li and O is 0-3%, which can be selected from 0.5% to 2.0%, such as 0.2%, 0.4%, 0.7%, 0.9%, 1%, 1.5%, 2%, 2.5%, 2.7%, 3%, and any combination of the above values.

[0060] Appropriate doping with Al and / or Mg elements is beneficial to improving the thermal stability of the positive electrode sheet of this application.

[0061] In some embodiments, the positive electrode active material further includes a second positive electrode active material; the second positive electrode active material comprises the compound Li. a A x Mn 1-y B y P 1-z C z O 4-n D n 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 0.9-1.1; x is 0-0.1, for example, 0, 0.02, 0.04, 0.05, 0.07, 0.08, 0.09, 0.1, and any of the above. The range of values ​​is defined as follows: y is 0.001-0.5, for example, 0.005, 0.01, 0.05, 0.07, 0.1, 0.2, 0.3, 0.4, 0.5 and any of the above values; z is 0.001-0.1, for example, 0.001, 0.005, 0.008, 0.01, 0.03, 0.05, 0.07, 0.1 and any of the above values; n is 0-0.1, for example, 0, 0.01, 0.02, 0.05, 0.07, 0.09, 0.1 and any of the above values.

[0062] In some embodiments, the second positive electrode active material includes a core and a shell covering the core; the core contains the compound Li. a A x Mn 1-y B y P 1-z C z O 4-n D n The shell contains carbon.

[0063] In some embodiments, the second positive electrode active material includes a core and a shell covering the core, the shell including a first coating layer covering the core, a second coating layer covering the first coating layer, and a third coating layer covering the second coating layer; the core comprises the compound Li. a A x Mn 1-y B y P 1-z C z O 4-n D nThe first coating layer contains crystalline pyrophosphate Li g EP2O7 and / or E h (P2O7) i The second coating layer contains crystalline phosphate X j PO4, the third coating layer contains carbon;

[0064] Among them, the crystalline pyrophosphate Li g EP2O7 and E h (P2O7) i Each of the elements E in the equation independently includes one or more elements selected from Fe, Ni, Mg, Co, Cu, Zn, Ti, Ag, Zr, Nb, and Al; the element X in the equation includes one or more elements selected from Li, Fe, Ni, Mg, Co, Cu, Zn, Ti, Ag, Zr, Nb, and Al; the element g is greater than 0 and less than or equal to 2, for example, 0.1, 0.5, 0.7, 1, 1.3, 1.5, 1.7, 1.9, and any of the above values; the element h is greater than 0 and less than or equal to 4, for example, 0.1, 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, and any of the above values; the element i is greater than 0 and less than or equal to 3, for example, 0.1, 0.5, 1, 1.5, 2, 2.5, 3, and any of the above values; the element j is greater than 0 and less than or equal to 3, for example, 0.1, 0.5, 1, 1.5, 2, 2.5, 3, and any of the above values.

[0065] In some implementations, LiNi b Co d Mn e M f O2, Li a A x Mn 1-y B y P 1-z C z O 4-n D n Li g EP2O7, E h (P2O7) i and X j PO4 is all electrically neutral.

[0066] In some embodiments, the positive electrode active material is composed of the first positive electrode active material and the second positive electrode active material.

[0067] Therefore, this application improves the safety performance of the battery by using a combination of the first positive electrode active material and the second positive electrode active material.

[0068] In some embodiments, the preparation method of the second positive electrode active material of this application includes the following steps:

[0069] Steps for providing kernel materials: Kernel materials contain Li a A x Mn 1-y B y P 1-z C z O 4-n D n 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 0.9-1.1; x is 0-0.1; y is 0.001-0.5; z is 0.001-0.1; and n is 0-0.1.

[0070] First encapsulation step: Providing Li g EP2O7 and / or E h (P2O7) i The first mixture is used to mix the core material with the first mixture, dry it, and sinter it to obtain the material coated with the first coating layer; wherein, crystalline pyrophosphate Li g EP2O7 and E h (P2O7) i Each of the elements E in the equation independently includes one or more of Fe, Ni, Mg, Co, Cu, Zn, Ti, Ag, Zr, Nb, and Al, wherein g is greater than 0 and less than or equal to 2, h is greater than 0 and less than or equal to 4, and i is greater than 0 and less than or equal to 3.

[0071] Second coating step: Providing a coating containing crystalline phosphate X j The second mixture of PO4 is obtained by mixing the material coated by the first coating layer with the second mixture, drying, and sintering to obtain a material coated by two coating layers; wherein X includes one or more elements selected from Li, Fe, Ni, Mg, Co, Cu, Zn, Ti, Ag, Zr, Nb, and Al; and j is greater than 0 and less than or equal to 3.

[0072] The third coating step involves providing a third mixture containing a carbon source, mixing the material coated by the two coating layers with the third mixture, drying, and sintering to obtain the second positive electrode active material.

[0073] 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.

[0074] 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.).

[0075] 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.

[0076] 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.

[0077] 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.

[0078] [Negative electrode plate]

[0079] 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.

[0080] 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.

[0081] 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.).

[0082] 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.

[0083] 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).

[0084] 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.

[0085] In some embodiments, the negative electrode film may optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0086] 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.

[0087] [Electrolytes]

[0088] The electrolyte acts as a conductor of ions between the positive and negative electrodes. The electrolyte can be liquid, gel-like, or entirely solid.

[0089] In some embodiments, the electrolyte is liquid and includes an electrolyte salt and a solvent.

[0090] In some embodiments, the secondary battery satisfies: 0 < ρ × m × b ≤ 79.1%, where ρ is the molar concentration of the electrolyte salt in the electrolyte, in mol / L; and m is the mass content of the first positive electrode active material in the positive electrode active material.

[0091] Therefore, commonly used electrolyte salts are easily decomposed, and the safety of the battery can be further improved by controlling the range of the product of ρ, m, and b.

[0092] In some embodiments, the electrolyte salt includes one or more of LiPF6, LiBF4, LiN(SO2F)2, LiN(CF3SO2)2, LiClO4, LiAsF6, LiB(C2O4)2, and LiBF2C2O4, optionally including one or more of LiPF6, LiN(SO2F)2, and LiN(CF3SO2)2, and more preferably LiPF6.

[0093] In some embodiments, the molar concentration ρ of the electrolyte salt in the electrolyte is 0.5-1.5 mol / L, for example 0.7 mol / L, 0.9 mol / L, 1.0 mol / L, 1.2 mol / L, 1.4 mol / L.

[0094] 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.

[0095] 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.

[0096] [Isolation membrane]

[0097] 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.

[0098] 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.

[0099] In some implementations, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding or stacking process.

[0100] 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.

[0101] 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.

[0102] 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 1 This is an example of a square-structured secondary battery 5.

[0103] In some implementations, refer to Figure 2 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. The positive electrode, negative electrode, and separator may be formed into an electrode assembly 52 by a winding process or a 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.

[0104] 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.

[0105] Figure 3 This is battery module 4, used as an example. (See reference...) Figure 3In 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.

[0106] Optionally, the battery module 4 may also include a housing with a receiving space in which a plurality of secondary batteries 5 are received.

[0107] 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.

[0108] Figure 4 and Figure 5 This is battery pack 1 as an example. (See reference...) Figure 4 and Figure 5 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.

[0109] 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 the power source of the electrical device or as the energy storage unit of 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.

[0110] As an electrical device, a secondary battery, battery module, or battery pack can be selected according to its usage requirements.

[0111] Figure 6 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.

[0112] [Example]

[0113] 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.

[0114] Example 1

[0115] (I) Preparation of the positive electrode sheet:

[0116] (1) First positive electrode active material:

[0117] LiNi 0.55 Co 0.14 1Mn 0.249 Al 0.04 Mg 0.02 O2 was purchased from Defang Nano.

[0118] (2) Preparation of the second positive electrode active material:

[0119] Step S1: Preparation of Fe, Co, V and S co-doped manganese oxalate

[0120] 574.7g of manganese carbonate, 571.2g of ferrous carbonate, 3.6g of nickel carbonate, and 4.9g of vanadium dichloride were added to a mixer and mixed thoroughly for 6 hours. The resulting mixture was then transferred to a reaction vessel, and 5L of deionized water and 1260.6g of oxalic acid dihydrate were added. The mixture was heated to 80°C and stirred thoroughly at 500 rpm for 6 hours until homogeneous mixing and the reaction was terminated without bubble generation, yielding a Fe, Co, and V co-doped manganese oxalate suspension. The suspension was then filtered, dried at 120°C, and milled to obtain manganese oxalate iron vanadium nickel dihydrate particles with a particle size of 100nm.

[0121] Step S2: Preparation of core Li 0.997 Mn 0.60 Fe 0.393 V 0.004 Co 0.003 P 0.997 S 0.003 O4

[0122] 1794.0 g of the prepared manganese iron vanadium nickel oxalate dihydrate, along with 369.8 g of lithium carbonate, 1148.9 g of ammonium dihydrogen phosphate, and 0.8 g of silicic acid, were added to 20 L of deionized water and stirred thoroughly. The mixture was then uniformly mixed and reacted at 80 °C for 10 h to obtain a slurry. The slurry was transferred to a spray dryer for spray drying and granulation, and dried at 250 °C to obtain a powder. Under a protective atmosphere (90% nitrogen and 10% hydrogen), the powder was sintered in a roller kiln at 700 °C for 4 h to obtain the core material. The elemental composition of the core material was determined using inductively coupled plasma atomic emission spectrometry (ICP).

[0123] Step S3: Preparation of the first coating layer suspension

[0124] Preparation of Li2FeP2O7 solution: 7.4g lithium carbonate, 11.6g ferrous carbonate, 23.0g ammonium dihydrogen phosphate and 12.6g oxalic acid dihydrate were dissolved in 500mL deionized water, and the pH was controlled at 5. The mixture was then stirred and reacted at room temperature for 2h to obtain a solution. The solution was then heated to 80℃ and maintained at this temperature for 4h to obtain the first coating layer suspension.

[0125] Step S4: Coating with the first coating layer

[0126] The 1573.0g of doped core material obtained in step S2 was added to the first coating layer suspension (coating material content of 15.7g) obtained in step S3. The mixture was stirred and mixed thoroughly for 6 hours. After being mixed evenly, the mixture was dried in an oven at 120℃ for 6 hours and then sintered at 650℃ for 6 hours to obtain the pyrophosphate coated material.

[0127] Step S5: Preparation of the second coating layer suspension

[0128] 3.7 g lithium carbonate, 11.6 g ferrous carbonate, 11.5 g ammonium dihydrogen phosphate and 12.6 g oxalic acid dihydrate were dissolved in 1500 mL deionized water, stirred and reacted for 6 h to obtain a solution. The solution was then heated to 120 °C and maintained at this temperature for 6 h to obtain a second coating layer suspension.

[0129] Step S6: Coating with the second coating layer

[0130] The 1588.7g of pyrophosphate-coated material obtained in step S4 was added to the second coating suspension (coating material content of 47.2g) obtained in step S5. The mixture was stirred and mixed thoroughly for 6 hours. After mixing evenly, the mixture was dried in an oven at 120℃ for 6 hours and then sintered at 700℃ for 8 hours to obtain the two-layer coated material.

[0131] Step S7: Preparation of the third coating layer aqueous solution

[0132] Dissolve 37.4g of sucrose in 500g of deionized water, then stir and dissolve completely to obtain a sucrose aqueous solution.

[0133] Step S8: Coating with the third coating layer

[0134] 1635.9 g of the two-layer coated material obtained in step S6 was added to the sucrose solution obtained in step S7 and stirred together for 6 hours. After mixing evenly, the mixture was dried in a 150°C oven for 6 hours and then sintered at 630°C for 8 hours to obtain a three-layer coated material with a Li core. 1.001 Mn 0.50 Fe 0.493 V 0.004 Ni 0.003 P 0.999 Si 0.001 O4, the first coating layer is 1% Li2FeP2O7 (based on the core mass), the second coating layer is 3% LiFePO4 (based on the core mass), and the third coating layer is 1% carbon (based on the core mass).

[0135] (3) Preparation of the positive electrode sheet:

[0136] The first positive electrode active material, the second positive electrode active material, the binder polyvinylidene fluoride (PVDF), and the conductive agent acetylene black were dissolved in the solvent N-methylpyrrolidone (NMP) at a mass ratio of 43.2:52.8:2:2 and thoroughly stirred to prepare a positive electrode slurry. The positive electrode slurry was then uniformly coated onto the positive electrode current collector aluminum foil, and then dried, cold-pressed, and slit to obtain the positive electrode sheet.

[0137] (II) Preparation of the negative electrode sheet:

[0138] Artificial graphite (anode active material), acetylene black (conductive agent), styrene-butadiene rubber (SBR) (binder), and sodium carboxymethyl cellulose (CMC-Na) (thickener) are dissolved in deionized water at a mass ratio of 96:2:1:1. The mixture is stirred and mixed thoroughly to prepare a cathode slurry. The cathode slurry is then coated onto copper foil (anode current collector), and subsequently dried, cold-pressed, and slit to obtain the cathode sheet.

[0139] (III) Separation membrane: Polyethylene microporous film is used as the porous separation membrane substrate. Inorganic alumina powder, polyvinylpyrrolidone and acetone solvent are mixed evenly in a weight ratio of 3:1.5:5.5 to form a slurry, which is then coated on both sides of the substrate and dried to obtain the separation membrane.

[0140] (iv) Preparation of electrolyte:

[0141] Ethyl carbonate (EC), methyl ethyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a volume ratio of 1:1:1. LiPF6 was then uniformly dissolved in this solution to obtain the electrolyte. The concentration of LiPF6 in the electrolyte was 1 mol / L.

[0142] (V) Preparation of secondary batteries:

[0143] The positive electrode, separator, and negative electrode are stacked and wound in sequence to obtain an electrode assembly. The electrode assembly is placed in an outer packaging, and the electrolyte prepared above is added. After processes such as encapsulation, standing, formation, and aging, a secondary battery is obtained.

[0144] Examples 2-21 and Comparative Examples 1-2 are similar to the secondary battery preparation methods in Example 1, with different product parameters detailed in Table 1.

[0145] The first positive electrode active material in Examples 2-3, 6-9, and 11 is the same as the first positive electrode active material in Example 1.

[0146] Preparation methods of the first positive electrode active material in Examples 4-5, 10, 16-18, 21 and Comparative Example 2

[0147] (1) Prepare a mixed solution by adding water to NiSO4, CoSO4 and MnSO4 in a molar ratio of 0.869:0.048:0.033, wherein the concentration of NiSO4 in the mixed solution is 2 mol / L; prepare a 6 mol / L NaOH solution;

[0148] (2) 50L of mixed solution was introduced into the reaction vessel, and then 50L of NaOH solution and an appropriate amount of 0.5mol / L ammonia solution were introduced into the reaction vessel to make the pH value in the reaction vessel 9.0-12.0, the reaction temperature 40℃-80℃, and the reaction was carried out for 60h under stirring conditions at a stirring speed of 300-1000r / min. After completion, the precipitate was filtered out and washed. The washed precipitate was vacuum dried at 120℃ for 24h to obtain the precursor.

[0149] (3) Mix LiOH, precursor, Al2O3 and MgO, wherein the molar ratio of LiOH (based on the molar amount of Li), precursor (based on the total molar amount of Ni, Co and Mn in the mixed solution), Al2O3 (based on the molar amount of Al) to MgO is 1.05:0.95:0.04:0.01. After mixing, place the mixture in a ball mill jar and ball mill at 300 r / s for 2 h. Then place it in a box furnace and pre-calcine it at 950℃ for 12 h under an air atmosphere of 0.2 MPa at a heating rate of 1℃ / min. Then sinter it at 600℃ for 8 h at a heating rate of 1℃ / min. After sintering, cool it down to 300℃ at a heating rate of 1℃ / min and continue to cool naturally to room temperature. Then pass it through an air jet mill at a speed of 3000 r / min and a 500 m 3 The material is pulverized at an airflow rate of / h for 0.5h, then sieved through a 500-mesh filter to obtain the first positive electrode active material, LiNi. 0.869 Co 0.048 Mn 0.033 Al 0.04 Mg 0.01 O2.

[0150] Preparation method of the first positive electrode active material in Example 12

[0151] (1) Prepare a mixed solution by adding water to NiSO4, CoSO4 and MnSO4 in a molar ratio of 0.573:0.118:0.2893, wherein the concentration of NiSO4 in the mixed solution is 2 mol / L; prepare a 5 mol / L NaOH solution;

[0152] (2) 50L of mixed solution was introduced into the reaction vessel, and then 50L of NaOH solution and an appropriate amount of 0.5mol / L ammonia solution were introduced into the reaction vessel to make the pH value in the reaction vessel 9.0-12.0, the reaction temperature 40℃-80℃, and the reaction was carried out for 60h under stirring conditions at a stirring speed of 300-1000r / min. After completion, the precipitate was filtered out and washed. The washed precipitate was vacuum dried at 120℃ for 24h to obtain the precursor.

[0153] (3) Li2CO3, the precursor, and MgO were mixed, wherein the molar ratio of Li2CO3 (based on the molar amount of Li), the precursor (based on the total molar amount of Ni, Co, and Mn in the mixed solution), and MgO was 1.05:0.98:0.02. After mixing, the mixture was placed in a ball mill jar and ball-milled at 300 r / s for 2 h. Then, it was placed in a box furnace and pre-calcined at 950 °C for 12 h under an air atmosphere of 0.2 MPa at a heating rate of 1 °C / min. Then, it was sintered at 600 °C for 8 h at a heating rate of 1 °C / min. After sintering, it was cooled to 300 °C at a heating rate of 1 °C / min and then allowed to cool naturally to room temperature. Finally, it was passed through an air jet mill at a speed of 3000 r / min and a 500 m... 3 The material is pulverized at an airflow rate of / h for 0.5h, then sieved through a 500-mesh filter to obtain the first positive electrode active material, LiNi. 0.573 Co 0.118 Mn 0.289 Mg 0.02 O2.

[0154] Preparation method of the first positive electrode active material in Example 13

[0155] In step (1), NiSO4, CoSO4 and MnSO4 are mixed with water in a molar ratio of 0.588:0.118:0.289 to form a mixed solution, wherein the concentration of NiSO4 in the mixed solution is 2 mol / L; and a 5 mol / L NaOH solution is prepared.

[0156] In step (3), the molar ratio of Li2CO3 (based on the molar amount of Li), the precursor (based on the total molar amount of Ni, Co and Mn in the mixed solution) to MgO is 1.05:0.98:0.05;

[0157] The rest is the same as in "Preparation method of the first positive electrode active material in Example 12", and the first positive electrode active material LiNi is obtained. 0.588 Co 0.118 Mn 0.289 Mg 0.005 O2.

[0158] Preparation method of the first positive electrode active material in Example 15

[0159] (1) Prepare a mixed solution by adding water to NiSO4, CoSO4 and MnSO4 in a molar ratio of 0.562:0.115:0.283, wherein the concentration of NiSO4 in the mixed solution is 2 mol / L; prepare a 5 mol / L NaOH solution;

[0160] (2) 50L of mixed solution was introduced into the reaction vessel, and then 50L of NaOH solution and an appropriate amount of 0.5mol / L ammonia solution were introduced into the reaction vessel to make the pH value in the reaction vessel 9.0-12.0, the reaction temperature 40℃-80℃, and the reaction was carried out for 60h under stirring conditions at a stirring speed of 300-1000r / min. After completion, the precipitate was filtered out and washed. The washed precipitate was vacuum dried at 120℃ for 24h to obtain the precursor.

[0161] (3) Li2CO3, the precursor, and Al2O3 were mixed, wherein the molar ratio of Li2CO3 (based on the molar amount of Li), the precursor (based on the total molar amount of Ni, Co, and Mn in the mixed solution), and Al2O3 (based on the molar amount of Al) was 1.05:0.96:0.04. After mixing, the mixture was placed in a ball mill jar and ball-milled at 300 r / s for 2 h. Then, it was placed in a box furnace and pre-calcined at 950 °C for 12 h under an air atmosphere of 0.2 MPa at a heating rate of 1 °C / min. Then, it was sintered at 600 °C for 8 h at a heating rate of 1 °C / min. After sintering, it was cooled to 300 °C at a heating rate of 1 °C / min and then allowed to cool naturally to room temperature. Finally, it was passed through an air jet mill at a speed of 3000 r / min and a flow rate of 500 m. 3 The material is pulverized at an airflow rate of / h for 0.5h, then sieved through a 500-mesh filter to obtain the first positive electrode active material, LiNi. 0.562 Co 0.115 Mn 0.283 Al 0.04 O2.

[0162] Preparation method of the first positive electrode active material in Example 14

[0163] In step (1), NiSO4, CoSO4 and MnSO4 are mixed with water in a molar ratio of 0.597:0.115:0.283 to form a mixed solution;

[0164] In step (3), the molar ratio of Li2CO3 (based on the molar amount of Li), the precursor (based on the total molar amount of Ni, Co and Mn in the mixed solution) to Al2O3 is 1.05:0.98:0.05;

[0165] The rest is the same as in "Preparation method of the first positive electrode active material in Example 15", and the first positive electrode active material LiNi is obtained. 0.597 Co 0.115 Mn 0.283 Al 0.005 O2.

[0166] Preparation method of the first positive electrode active material in Example 19

[0167] (1) Prepare a mixed solution by adding water to NiSO4, CoSO4 and MnSO4 in a molar ratio of 0.585:0.12:0.295, wherein the concentration of NiSO4 in the mixed solution is 2 mol / L; prepare a 5 mol / L NaOH solution;

[0168] (2) 50L of mixed solution was introduced into the reaction vessel, and then 50L of NaOH solution and an appropriate amount of 0.5mol / L ammonia solution were introduced into the reaction vessel to make the pH value in the reaction vessel 9.0-12.0, the reaction temperature 40℃-80℃, and the reaction was carried out for 60h under stirring conditions at a stirring speed of 300-1000r / min. After completion, the precipitate was filtered out and washed. The washed precipitate was vacuum dried at 120℃ for 24h to obtain the precursor.

[0169] (3) Mix Li2CO3, precursor, Al2O3 and MgO, wherein the molar ratio of Li2CO3 (based on the molar amount of Li), precursor (based on the total molar amount of Ni, Co and Mn in the mixed solution), Al2O3 (based on the molar amount of Al) to MgO is 1.05:1:0.04:0.02. After mixing, place the mixture in a ball mill jar and ball mill at 300 r / s for 2 h. Then place it in a box furnace and pre-calcine it at 950℃ for 12 h under an air atmosphere of 0.2 MPa at a heating rate of 1℃ / min. Then sinter it at 600℃ for 8 h at a heating rate of 1℃ / min. After sintering, cool it down to 300℃ at a heating rate of 1℃ / min and continue to cool naturally to room temperature. Then pass it through an air jet mill at a speed of 3000 r / min and a 500 m 3 The material is pulverized at an airflow rate of / h for 0.5h, then sieved through a 500-mesh filter to obtain the first positive electrode active material, LiNi. 0.585 Co 0.12 Mn 0.295 O2.

[0170] Preparation method of the first positive electrode active material in Example 20

[0171] In step (1), NiSO4, CoSO4 and MnSO4 are mixed with water in a molar ratio of 0.522:0.115:0.283 to form a mixed solution;

[0172] In step (3), the molar ratio of LiOH (based on the molar amount of Li), the precursor (based on the total molar amount of Ni, Co and Mn in the mixed solution), Al2O3 (based on the molar amount of Al) to MgO is 1.05:0.92:0.05:0.03.

[0173] The rest is the same as the preparation method of the first positive electrode active material in Example 4.

[0174]

[0175]

[0176]

[0177] Battery test

[0178] (1) Energy density testing

[0179] In a constant temperature environment of 25℃, after the battery is left to stand for 10 minutes, it is discharged at a constant current of 0.33C to the cutoff voltage of 2.8V. After standing for 10 minutes, it is charged at a constant current of 0.33C to the target voltage of 4.3V. Constant voltage charging is continued until the current is ≤0.05C. After standing for 10 minutes, it is discharged at a constant current of 0.33C to the cutoff voltage of 2.8V. The discharge capacity is recorded. The specific capacity of the positive electrode active material is obtained by dividing the discharge capacity by the total mass of the positive electrode active material, in mAh / g.

[0180] (2) Hot box safety test:

[0181] The test referenced the "Heating" section of the safety testing in GB 38031-2020, and explored the upper limit boundaries, optimizing the test conditions as follows:

[0182] ①Preparation:

[0183] Test conditions: Prepare an explosion-proof oven that can heat the circuit connection points; the test cells are fresh bare cells (cycle count ≤ 10 times); temperature sensing wires are attached around the cells and on the terminals for temperature monitoring; and a temperature recording device is also provided.

[0184] Cell treatment before testing: Constant current charging is performed using a 0.33C rate to fully charge the cell to the nominal voltage (e.g., 4.3V in this invention).

[0185] ② Test procedure: Place the sample in a high-temperature chamber, and raise the temperature from room temperature to 100℃ at a rate of 5℃ / min, and maintain it for 2 hours; then raise the temperature at a rate of 5℃ / min, and maintain it for 30 minutes every 5℃, until the cell runs out of control (runout criteria: voltage drops by ≥50% within 1 minute, cell temperature rises by ≥50% within 1 minute) or heats to 200℃, then stop heating.

[0186] ③ Data processing: Based on the above conditions, find the failure point and obtain the corresponding heat preservation temperature and heat preservation time, which are recorded as: time@temperature, such as 21min@150℃.

[0187] ④ Result Benchmarking:

[0188] Samples that are tested for a longer period of time during the testing process are safer; samples that are tested for a longer period of time can be: samples with the same failure point temperature but longer time, samples with the same failure point time but higher temperature, and samples with different failure point temperatures and times but higher temperature.

[0189] Table 2: Performance test results of Examples 1-21 and Comparative Examples 1-2

[0190] serial number Capacity (mAh / g) Hot Box Safety Test Results Example 1 151 160℃@15min Example 2 140 200℃@30min Example 3 155 185℃@15min Example 4 175 150℃@10min Example 5 192 135℃@30min Example 6 136 200℃@30min Example 7 166 155℃@30min Example 8 136 200℃@30min Example 9 164 150℃@20min Example 10 201 140℃@15min Example 11 170 160℃@10min Example 12 160 155℃@20min Example 13 155 145℃@12min Example 14 156 145℃@15min Example 15 161 155℃@18min Example 16 200 180℃@10min Example 17 201 160℃@30min Example 18 195 130℃@30min Example 19 153 135℃@28min Example 20 143 155℃@15min Example 21 196 135℃@12min Comparative Example 1 135 200℃@30min Comparative Example 2 200 130℃@10min

[0191] Based on the above results, we can conclude that:

[0192] Compared with Comparative Examples 1-2, the batteries of Examples 1-21 of this application have higher energy density and higher safety.

[0193] Compared with Examples 18, 19, and 21, the batteries of Examples 1-17 of this application are safer.

[0194] Compared with Example 20, the batteries in Examples 1, 3-5, 7, and 9-17 of this application have higher specific capacity and higher energy density.

[0195] 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 and a positive electrode film layer disposed on at least one surface of the positive current collector, the positive electrode film layer comprising a positive electrode active material, the positive electrode active material comprising Ni, Fe, Mn and Al elements; Furthermore, the positive electrode plate satisfies: 0< C Ni / (C Ni +C Fe +C Mn +C Al ) ≤90.10%; in, The C Ni The mass content of Ni element in the positive electrode film layer, the C Fe The mass content of Fe element in the positive electrode film layer, the C Mn The mass content of Mn element in the positive electrode film layer, the C Al The mass content of Al element in the positive electrode film layer; The positive electrode active material includes a first positive electrode active material and a second positive electrode active material; The first positive electrode active material contains the compound LiNi b Co d Mn e M f O2; wherein M includes Mg and Al elements; b is 0.314-0.970; d is 0-0.320; e is 0.006-0.390; and the sum of b, d, e and f is 1 and f is greater than 0; The first positive electrode active material satisfies: 47.85% ≤ m×b ≤ 79.10%, where m is the mass content of the first positive electrode active material in the positive electrode active material; The second positive electrode active material includes a core and a shell covering the core; the core contains the compound Li. a A x Mn 1-y B y P 1-z C z O 4-n D n The shell contains carbon, 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 0.9-1.1; x is 0-0.1; y is 0.001-0.5; z is 0.001-0.1; and n is 0-0.

1. The shell includes a first coating layer covering the core, a second coating layer covering the first coating layer, and a third coating layer covering the second coating layer; the core contains the compound Li. a A x Mn 1-y B y P 1-z C z O 4-n D n The first coating layer contains crystalline pyrophosphate Li g EP2O7 and / or E h (P2O7) i The second coating layer contains crystalline phosphate X j PO4, the third coating layer contains carbon; Among them, the crystalline pyrophosphate Li g EP2O7 and E h (P2O7) i Each of E in the above contexts independently includes one or more elements selected from Fe, Ni, Mg, Co, Cu, Zn, Ti, Ag, Zr, Nb, and Al; each of X in the above contexts includes one or more elements selected from Li, Fe, Ni, Mg, Co, Cu, Zn, Ti, Ag, Zr, Nb, and Al; each of g in the above contexts is greater than 0 and less than or equal to 2; each of h in the above contexts is greater than 0 and less than or equal to 4; each of i in the above contexts is greater than 0 and less than or equal to 3; and each of j in the above contexts is greater than 0 and less than or equal to 3.

2. The positive electrode sheet according to claim 1, wherein, The positive electrode plate satisfies: 2.88%≤ C Ni / (C Ni +C Fe +C Mn +C Al ) ≤86.10%。 3. The positive electrode sheet according to claim 1, wherein, The value of d is 0.047-0.

320.

4. The positive electrode sheet according to claim 1, wherein, The first positive electrode active material satisfies: 47.85% ≤ m×b ≤ 73.87%.

5. The positive electrode sheet according to claim 1, wherein, In the first positive electrode active material, the molar proportion of Al in the elements other than Li and O is 0-5%, and not equal to 0; and / or, The molar proportion of Mg in the elements other than Li and O is 0-3%, and is not equal to 0.

6. The positive electrode sheet according to claim 5, wherein, In the first positive electrode active material, the molar ratio of Al element in the elements other than Li and O elements is 0.5%-4%.

7. The positive electrode sheet according to claim 5, wherein, The molar proportion of Mg in the elements other than Li and O is 0.5% to 2.0%.

8. The positive electrode sheet according to any one of claims 1 to 7, wherein, The positive electrode active material is composed of the first positive electrode active material and the second positive electrode active material.

9. A battery comprising the positive electrode sheet as described in claim 1 or 2.

10. The battery of claim 9, further comprising an electrolyte comprising an electrolyte salt; and the battery satisfying 22.16% ≤ ρ × m × b ≤ 79.1%, wherein, ρ is the molar concentration of the electrolyte salt in the electrolyte, in mol / L; m is the mass content of the first positive electrode active material in the positive electrode active material.

11. The battery according to claim 10, wherein, The electrolyte salt includes one or more of LiPF6, LiBF4, LiN(SO2F)2, LiN(CF3SO2)2, LiClO4, LiAsF6, LiB(C2O4)2, and LiBF2C2O4.

12. The battery according to claim 11, wherein, The electrolyte salt includes one or more of LiPF6, LiN(SO2F)2 and LiN(CF3SO2)2.

13. An electrical device comprising the battery according to any one of claims 9 to 12.

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