WO2025103530A1 - 二次电池及用电装置 - Google Patents

二次电池及用电装置 Download PDF

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Publication number
WO2025103530A1
WO2025103530A1 PCT/CN2025/073058 CN2025073058W WO2025103530A1 WO 2025103530 A1 WO2025103530 A1 WO 2025103530A1 CN 2025073058 W CN2025073058 W CN 2025073058W WO 2025103530 A1 WO2025103530 A1 WO 2025103530A1
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Prior art keywords
positive electrode
secondary battery
active material
battery
negative electrode
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PCT/CN2025/073058
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English (en)
French (fr)
Inventor
郭洁
韩昌隆
王冠
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Contemporary Amperex Technology Co Ltd
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Contemporary Amperex Technology Co Ltd
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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H01M10/0567—Liquid materials characterised by the additives
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/058—Construction or manufacture
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
    • H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
    • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/021—Physical characteristics, e.g. porosity, surface area
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2220/00—Batteries for particular applications
    • H01M2220/20—Batteries in motive systems, e.g. vehicle, ship, plane
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present application relates to the field of new energy technology, and in particular to a secondary battery and an electrical device.
  • secondary batteries such as lithium-ion batteries
  • energy storage power systems such as hydropower, thermal power, wind power and solar power stations
  • power tools electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace and other fields.
  • lithium-ion batteries have made great progress, higher requirements have been put forward for their fast charging performance, especially how to solve the problem of thermal runaway caused by excessive temperature rise during fast charging.
  • the present application provides a secondary battery and an electrical device that can improve fast charging performance and the thermal runaway problem caused by excessive temperature rise during fast charging.
  • the first aspect of the present application provides a secondary battery, comprising a positive electrode sheet, a negative electrode sheet, and an electrolyte disposed between the positive electrode sheet and the negative electrode sheet;
  • the electrolyte includes LiFSI with a mass content of a; the positive electrode sheet contains a positive electrode active material, the Dv99 of the positive electrode active material is y 1 ⁇ m, and y 1 is 5-15; the secondary battery meets the following condition: 100 ⁇ y 1 /a ⁇ 10000.
  • the above-mentioned secondary battery of the present application can improve the temperature rise by adding LiFSI to the electrolyte, but too much LiFSI will affect the battery life due to its inherent inability to resist oxidation; the use of positive electrode active materials with a smaller Dv99 value can improve the temperature rise, but too small a Dv99 value will deteriorate the battery life.
  • the present application achieves the temperature rise during fast charging by controlling the relationship between Dv99 and LiFSI content, while avoiding the life problems caused by LiFSI and Dv99.
  • the secondary battery satisfies at least one of the following conditions:
  • y1 is 5 to 12
  • y1 is 5-10.
  • the secondary battery satisfies at least one of the following conditions:
  • the secondary battery can have excellent fast charging performance, cycle life and hot box safety performance while having a lower temperature rise.
  • the secondary battery satisfies at least one of the following conditions:
  • y2 is 2-5.
  • y2 is 3-5.
  • the positive electrode active material includes a nickel-cobalt-manganese ternary positive electrode material.
  • the molar proportion of cobalt is 5% to 15%, and the molar proportion of nickel is 50% to 90%;
  • the molar proportion of cobalt element in the total molar amount of nickel, cobalt and manganese elements in the nickel-cobalt-manganese ternary positive electrode material, is 9% to 15%, and the molar proportion of nickel element is 50% to 70%.
  • the molar proportion of nickel element and the molar proportion of cobalt element are controlled within this range, so that the battery has better cycle life and hot box safety performance.
  • the compaction density of the negative electrode sheet is ⁇ 1.6 g/cm 3 .
  • the secondary battery further comprises a separator disposed between the positive electrode sheet and the negative electrode sheet, and the Gurley value of the separator is 100s to 600s;
  • the Gurley value of the isolation film is 400s to 500s.
  • the second aspect of the present application further provides an electrical device, comprising the secondary battery of the first aspect of the present application.
  • the electric device of the present application includes the secondary battery provided by the present application, and thus has at least the same advantages as the secondary battery.
  • FIG. 1 is a schematic diagram of a battery cell according to an embodiment of the present application.
  • FIG. 2 is an exploded view of the battery cell according to an embodiment of the present application shown in FIG. 1 .
  • FIG. 3 is a schematic diagram of a battery module according to an embodiment of the present application.
  • FIG. 4 is a schematic diagram of a battery pack according to an embodiment of the present application.
  • FIG. 5 is an exploded view of the battery pack shown in FIG. 4 according to an embodiment of the present application.
  • FIG. 6 is a schematic diagram of an electrical device using a secondary battery as a power source according to an embodiment of the present application.
  • “Scope” disclosed in the present application can be limited in the form of lower limit and upper limit, and a given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of a special range.
  • the scope limited in this way can be including end values or excluding end values, and any end value can be included or not included independently, and can be combined arbitrarily, that is, any lower limit can be combined with any upper limit to form a scope. For example, if the scope of 60-120 and 80-110 is listed for a specific parameter, it is understood that the scope of 60-110 and 80-120 is also expected.
  • the numerical range "a-b" represents the abbreviation of any real number combination between a and b, wherein a and b are real numbers.
  • the numerical range "0-5" means that all real numbers between "0-5" are listed in this document, and "0-5" is just an abbreviation for these numerical combinations.
  • a parameter is expressed as an integer ⁇ 2 it is equivalent to listing the parameter as, for example, integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.
  • a parameter is expressed as an integer selected from "2-10", it is equivalent to listing the integers 2, 3, 4, 5, 6, 7, 8, 9 and 10.
  • each step is written does not mean a strict order of execution and does not constitute any limitation on the implementation process, and the detailed order of execution of each step should be determined by its function and possible internal logic. If there is no special explanation, all steps of the present application can be performed sequentially or randomly, preferably sequentially.
  • the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or steps (b) and (a) performed sequentially.
  • the method may also include step (c), indicating that step (c) can be added to the method in any order, for example, the method may include steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), etc.
  • A includes a1, a2 and a3. Unless otherwise specified, it may also include other members or may not include additional members. It can be regarded as providing both the feature or solution of "A consists of a1, a2 and a3" and the feature or solution of "A not only includes a1, a2 and a3, but also includes other members".
  • A (such as B) means that B is a non-limiting example of A, and it can be understood that A is not limited to B.
  • a secondary battery includes a positive electrode sheet, a negative electrode sheet and an electrolyte.
  • the electrolyte is located between the positive electrode sheet and the negative electrode sheet.
  • active ions are embedded and extracted back and forth between the positive electrode sheet and the negative electrode sheet.
  • the electrolyte plays the role of conducting ions between the positive electrode sheet and the negative electrode sheet.
  • the electrolyte is liquid, i.e., an electrolyte.
  • the secondary battery also includes a separator, which is disposed between the positive electrode sheet and the negative electrode sheet, and mainly plays the role of preventing the positive and negative electrodes from short-circuiting, while allowing ions to pass through.
  • An embodiment of the present application provides a secondary battery, comprising a positive electrode sheet, a negative electrode sheet, and an electrolyte disposed between the positive electrode sheet and the negative electrode sheet.
  • the electrolyte comprises LiFSI with a mass content of a.
  • the positive electrode sheet contains a positive electrode active material, the Dv99 of the positive electrode active material is y 1 ⁇ m, and y 1 is 5 to 15; the secondary battery satisfies the following conditions: 100 ⁇ y 1 /a ⁇ 1000.
  • the above-mentioned secondary battery of the present application can improve the temperature rise by adding LiFSI to the electrolyte, but too much LiFSI will affect the battery life due to its inherent inability to resist oxidation; the use of positive electrode active materials with a smaller Dv99 value can improve the temperature rise, but too small a Dv99 value will deteriorate the battery life.
  • the present application achieves the temperature rise during fast charging by controlling the relationship between Dv99 and LiFSI content, while avoiding the life problems caused by LiFSI and Dv99.
  • y1 /a reflects the relationship between the Dv99 value and the LiFSI content of the positive electrode active material. If y1 /a is too large, it means that Dv99 is too large or the LiFSI content is too small, both of which will affect the temperature rise of the battery; while if y1 /a is too small, it means that y1 is too small or the LiFSI content is too small or too much, both of which will affect the cycle life of the battery. By controlling the Dv99 value and the LiFSI content within a suitable range, a secondary battery with better temperature rise performance and cycle life can be obtained.
  • Dv99 is a well-known meaning in the art and can be tested by methods known in the art. For example, it can be measured using a laser particle size analyzer (such as Malvern Master Size 3000).
  • Dv99 represents the particle size corresponding to the volume distribution percentage of particles from a small particle size when it accumulates to 99% based on the particle size volume distribution.
  • Dv50 represents the particle size corresponding to the volume distribution percentage of particles from a small particle size when it accumulates to 50% based on the particle size volume distribution.
  • the particle size volume distribution can be obtained by the following method: take a clean beaker, add an appropriate amount of the sample to be tested, and fully ultrasonicate to ensure that the sample is completely dispersed.
  • the test instrument is Malvern 2000 of the United States. After the sample is poured into the injection tower, it circulates with the solution to the test optical path system. When the particles are irradiated by the laser beam, the particle size distribution characteristics of the particles can be obtained by receiving and measuring the energy distribution of the scattered light (shading degree: 8-12%). Draw a particle size volume distribution diagram based on the test data.
  • the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector, wherein the positive electrode active material layer includes the positive electrode active material mentioned above.
  • the positive electrode current collector has two surfaces opposite to each other in its thickness direction, and the positive electrode active material layer is disposed on any one or both of the two opposite surfaces of the positive electrode current collector.
  • the positive electrode current collector may be a metal foil or a composite current collector.
  • aluminum foil may be used as the metal foil.
  • the composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer.
  • the composite current collector may be obtained by forming a metal material on a polymer material substrate.
  • the metal material may include one or more of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy.
  • non-limiting examples of the polymer material substrate may include one or more of substrates such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.
  • substrates such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.
  • the thickness of the single-sided positive electrode active material layer is 26-68 ⁇ m.
  • the Dv99 of the positive electrode active material is y 1 ⁇ m
  • y 1 can be 5 ⁇ m, 6 ⁇ m, 7 ⁇ m, 8 ⁇ m, 9 ⁇ m, 10 ⁇ m, 11 ⁇ m, 12 ⁇ m, 13 ⁇ m, 14 ⁇ m, 15 ⁇ m, or a range consisting of any two of the above values.
  • y 1 is 5 to 12; in other words, the Dv99 of the positive electrode active material is 5 to 12 ⁇ m.
  • the positive electrode active material with the above particle size can be purchased from the market or prepared by oneself.
  • the specific preparation method can adopt the known preparation method. Taking the nickel-cobalt-manganese ternary material as an example, the specific preparation steps can be:
  • Step 1 preparing a hydroxide precursor Ni x Co y M 1-xy (OH) 2 ; preparing a metal salt solution with Ni salt, Co salt and M salt, wherein the total concentration of metal ions is 1.0-5.0 mol/L; subjecting the metal salt solution to a coprecipitation reaction with an ammonia-alkali mixed solution in a reactor to prepare the precursor Ni x Co y M 1-xy (OH) 2 ; wherein 0 ⁇ x ⁇ 1, 0 ⁇ y ⁇ 1, 0 ⁇ 1-xy ⁇ 1.
  • Step 2 preparing a ternary positive electrode material LiNi x Co y M 1-xy O 2 ; grinding and mixing the precursor obtained in step 1 with a flux and LiOH ⁇ H 2 O; sintering the mixture in an oxygen atmosphere, controlling the temperature at 700-1000° C. for 8-20 hours; grinding, washing, filtering and drying the sintered material; after drying, calcining the material in an oxygen atmosphere, controlling the conditions at 750-1000° C. for 1-10 hours; thus obtaining the ternary positive electrode material LiNi x Co y M 1-xy O 2 ;
  • the above ternary cathode material can also be coated on the surface.
  • the ternary cathode material obtained in step 2 is ground and mixed with the coating raw material.
  • the mixture is sintered in an oxygen atmosphere at 700-1000°C for 3-15h.
  • the coating raw material can be one or both of LiOH ⁇ H2O and Li2O .
  • the Dv50 of the positive electrode active material is y 2 ⁇ m, and the secondary battery satisfies the following condition: 1.2 ⁇ y 1 /y 2 ⁇ 7. Alternatively, 2 ⁇ y 1 /y 2 ⁇ 6.
  • the value of y 1 /y 2 may be 1.2, 1.5, 1.8, 2, 2.5, 2.8, 2.9, 3, 3.4, 3.5, 3.8, 4, 4.2, 4.5, 6, 6.5, 7, or a range formed by any two of the above values.
  • y2 is 1.5-6; more optionally, y2 is 2-5; more optionally, y2 is 3-5.
  • the Dv50 of the positive electrode active material may be 1.5 ⁇ m, 2 ⁇ m, 2.5 ⁇ m, 2.9 ⁇ m, 2.9 ⁇ m, 3.5 ⁇ m, 4 ⁇ m, 4.5 ⁇ m, 5 ⁇ m, 5.5 ⁇ m, 5.6 ⁇ m, 5.8 ⁇ m, 6 ⁇ m, or a range consisting of any two of the above values.
  • the particle size distribution of the positive electrode active material can be limited, which can take into account excellent fast charging performance, cycle life and hot box safety performance, while having a lower temperature rise.
  • y1 / y2 means the difference between Dv99 and Dv50 values.
  • the smaller the difference the more uniform the particle size of the positive electrode active material, the easier it is to form a lithium ion transmission path, and improve the fast charging performance, but the larger Dv50 is easy to increase the fast charging temperature rise.
  • the larger the difference the uneven particle size of the positive electrode active material.
  • the combination of different particle sizes can improve the energy density, but the smaller Dv50 is conducive to reducing the temperature rise, but it will increase side reactions, reduce the cycle life and hot box safety performance.
  • the battery can have better comprehensive performance.
  • the positive electrode active material may be a positive electrode active material for a battery known in the art.
  • the positive electrode active material may include one or more of the following materials: lithium-containing phosphates of an olivine structure, lithium transition metal oxides and their respective modified compounds.
  • the present application is not limited to these materials, and other traditional materials that can be used as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more.
  • lithium transition metal oxides may include, but are not limited to, one or more of lithium cobalt oxide (such as LiCoO2 ), lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, nickel cobalt manganese ternary positive electrode materials (or lithium nickel cobalt manganese oxide), lithium nickel cobalt aluminum oxide and its modified compounds.
  • lithium cobalt oxide such as LiCoO2
  • lithium nickel oxide lithium manganese oxide
  • lithium nickel cobalt oxide lithium manganese cobalt oxide
  • lithium nickel manganese oxide lithium nickel cobalt oxide
  • nickel manganese oxide lithium nickel cobalt manganese ternary positive electrode materials (or lithium nickel cobalt manganese oxide)
  • lithium nickel cobalt aluminum oxide and its modified compounds lithium nickel cobalt aluminum oxide and its modified compounds.
  • Non-limiting examples of olivine-structured lithium-containing phosphates may include, but are not limited to, one or more of lithium iron phosphate, a composite material of lithium iron phosphate and carbon, lithium manganese phosphate, a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon.
  • Non-limiting examples of lithium cobalt oxide may include LiCoO 2 ; non-limiting examples of lithium nickel oxide may include LiNiO 2 ; non-limiting examples of lithium manganese oxide may include LiMnO 2 , LiMn 2 O 4 , etc.; non-limiting examples of lithium nickel cobalt aluminum oxide may include LiNi 0.85 Co 0.15 Al 0.05 O 2 .
  • Non-limiting examples of nickel-cobalt-manganese ternary positive electrode materials may include LiNi 1/3 Co 1/3 Mn 1/3 O 2 (also referred to as NCM 333 ), LiNi 0.5 Co 0.2 Mn 0.3 O 2 (also referred to as NCM 523 ), LiNi 0.5 Co 0.25 Mn 0.25 O 2 (also referred to as NCM 211 ), LiNi 0.5 Co 0.15 Mn 0.35 O 2 , LiNi 0.6 Co 0.2 Mn 0.2 O 2 (also referred to as NCM 622 ), LiNi 0.8 Co 0.1 Mn 0.1 O 2 (also referred to as NCM 811 ), LiNi 0.85 Co 0.05 Mn 0.1 O 2 , LiNi 0.64 Co 0.09 Mn 0. Mn 0.27 O 2 , LiNi 0.68 Co 0.10 Mn 0.22 O 2 , etc. It can be understood that the nickel-cobalt-manganesese
  • the battery will be accompanied by lithium (Li) deintercalation and consumption during the charging and discharging process, and the content of Li in the positive electrode active material is different when the battery is discharged to different states.
  • Li lithium
  • the content of Li is the initial state of the material.
  • the positive electrode active material is applied to the positive electrode plate in the battery system, and after the charge and discharge cycle, the content of Li in the positive electrode active material contained in the plate usually changes.
  • the content of Li can be measured by molar ratio, but is not limited to this.
  • the initial state of the material refers to the state before the material is added to the positive electrode slurry. It is understandable that the new material obtained by appropriate modification on the basis of the listed positive electrode active materials is also within the scope of positive electrode active materials.
  • the aforementioned appropriate modification refers to the acceptable modification method for the positive electrode active material, and non-limiting examples include coating modification.
  • the content of oxygen (O) is only a theoretical state value.
  • the release of oxygen from the lattice will cause the molar percentage of oxygen to change, and the actual content of O will fluctuate.
  • the content of O can be measured by molar percentage, but is not limited to this.
  • the positive electrode active material includes a nickel-cobalt-manganese ternary positive electrode material.
  • the molar proportion of cobalt is 5% to 15%, and the molar proportion of Ni is 50% to 90%.
  • the molar proportion of cobalt is 9% to 15%, and the molar proportion of Ni is 50% to 70%.
  • the molar proportion of Ni can be 50%, 55%, 60%, 64%, 65%, 68%, 70%, 75%, 80%, 85%, 90%.
  • the molar proportion of cobalt can be 5%, 6%, 9%, 10%, 12%, 15%.
  • Ni content and Co content of the positive electrode active material so that the battery has a better cycle life and hot box safety performance.
  • a higher Ni content can achieve a higher energy density, but too high a Ni content will deteriorate the cycle life and hot box safety performance of the battery.
  • the molar content of each element (such as nickel, cobalt and manganese) in the positive electrode active material can be tested and analyzed by methods well known in the art, such as the ICP method (trace element analysis-inductively coupled plasma emission spectrometry) using an inductively coupled plasma emission spectrometer iCAP 7400.
  • ICP method trace element analysis-inductively coupled plasma emission spectrometry
  • the molar proportion of cobalt element in the surface layer of the nickel-cobalt-manganese ternary positive electrode material is greater than the molar proportion of cobalt element in the inner layer.
  • the composition of the inner layer and the surface layer of the nickel-cobalt-manganese ternary positive electrode material is different, the molar proportion of cobalt element in the inner layer is small, and the molar proportion of cobalt element in the surface layer is large.
  • the gradient setting of Co in the nickel-cobalt-manganese ternary positive electrode material can effectively stabilize the structure of the positive electrode active material and improve the kinetic performance of the positive electrode sheet.
  • the molar ratio of the cobalt element in the inner layer and the surface layer can be differentiated by using precursors of different compositions for multiple coatings. It is understood that the specific implementation method is not limited thereto.
  • the positive electrode active material layer may also optionally include a binder.
  • the binder may include one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylate resin.
  • PVDF polyvinylidene fluoride
  • PTFE polytetrafluoroethylene
  • PTFE polytetrafluoroethylene
  • vinylidene fluoride-tetrafluoroethylene-propylene terpolymer vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer
  • the positive electrode active material layer may further include a conductive agent.
  • the conductive agent may include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.
  • the mass content of the positive electrode active material is 75% to 98%.
  • the mass content of the conductive agent is 0.1% to 15%.
  • the binder in the positive electrode active material layer, has a mass content of 0.5% to 15%.
  • the positive electrode sheet can be prepared in the following manner: the components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder and any other components are dispersed in a solvent to form a positive electrode slurry; the positive electrode slurry is coated on at least one side of the positive electrode collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.
  • the components for preparing the positive electrode sheet such as the positive electrode active material, the conductive agent, the binder and any other components are dispersed in a solvent to form a positive electrode slurry
  • the positive electrode slurry is coated on at least one side of the positive electrode collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.
  • the type of solvent may be selected from but not limited to any one of the aforementioned embodiments, such as N-methylpyrrolidone (NMP).
  • NMP N-methylpyrrolidone
  • the surface of the positive current collector coated with the positive electrode slurry may be on a single surface of the positive current collector or on both surfaces of the positive current collector.
  • the surface of the positive current collector coated with the positive electrode slurry may be on a single surface of the positive current collector or on both surfaces of the positive current collector.
  • the solid content of the positive electrode slurry may be 40wt% to 80wt%.
  • the viscosity of the positive electrode slurry at room temperature may be adjusted to 5000 to 25000 mPa ⁇ s.
  • the coating unit area density on a dry weight basis (excluding the solvent) may be 15 to 35 mg/cm 2 .
  • the compacted density of the positive electrode sheet may be 3.0 to 3.6 g/cm 3 , and may be optionally 3.3 to 3.5 g/cm 3 .
  • the negative electrode plate includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector.
  • the negative electrode current collector has two surfaces opposite to each other in its own thickness direction, and the negative electrode active material layer is disposed on any one or both of the two opposite surfaces of the negative electrode current collector.
  • the negative electrode current collector may be a metal foil or a composite current collector.
  • copper foil may be used as the metal foil.
  • the composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material substrate.
  • the composite current collector may be obtained by forming a metal material on a polymer material substrate.
  • non-limiting examples of the metal material may include one or more of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy.
  • non-limiting examples of the polymer material substrate may include one or more of substrates such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.
  • substrates such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.
  • the negative electrode film layer may include a negative electrode active material layer, and the negative electrode active material layer includes a negative electrode active material.
  • the thickness of the single-sided negative electrode active material layer is 22-110 ⁇ m.
  • the negative electrode active material may adopt the negative electrode active material for batteries known in the art.
  • the negative electrode active material may include one or more of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, etc.
  • the silicon-based material may include one or more of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys.
  • the tin-based material may include one or more of elemental tin, tin oxide compounds, and tin alloys.
  • the present application is not limited to these materials, and other traditional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.
  • the negative electrode active material layer may further include a binder.
  • the binder may include one or more 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).
  • the negative electrode active material layer may further include a conductive agent, which may include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.
  • a conductive agent which may include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.
  • the negative electrode active material layer may further include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).
  • a thickener eg, sodium carboxymethyl cellulose (CMC-Na)
  • the mass content of the negative electrode active material is 75% to 98%.
  • the mass content of the conductive agent is 0.1% to 15%.
  • the mass content of the binder is 0.5% to 15%.
  • the negative electrode sheet can be prepared in the following manner: the components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder and any other components are dispersed in a solvent (a non-limiting example of the solvent is deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on at least one side of the negative electrode current collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.
  • a solvent a non-limiting example of the solvent is deionized water
  • the negative electrode current collector surface coated with the negative electrode slurry may be on a single surface of the negative electrode current collector or on both surfaces of the negative electrode current collector.
  • the solid content of the negative electrode slurry may be 40wt% to 60wt%.
  • the viscosity of the negative electrode slurry at room temperature may be adjusted to 2000-10000mPa ⁇ s.
  • 0 ⁇ a ⁇ 10% the value of a can be 0.01%, 0.02%, 0.05%, 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or a range consisting of any two of the above values.
  • 0.01% ⁇ a ⁇ 10% optionally, 0.1% ⁇ a ⁇ 5%; further, 1% ⁇ a ⁇ 5%, more optionally, 1% ⁇ a ⁇ 5%.
  • the value of y 1 /a may be 100, 120, 150, 160, 167, 170, 200, 233, 300, 330, 333, 340, 400, 500, 600, 1000, 2000, 3000, 4000, 5000, 6000, 7000, 8000, 9000, 10000.
  • the value range of y 1 /a may be a range consisting of any two of the above values. Further, 200 ⁇ y 1 /a ⁇ 5000, or 100 ⁇ y 1 /a ⁇ 5000; 200 ⁇ y 1 /a ⁇ 600; or a range consisting of any two of the above values.
  • the electrolyte includes LiFSI with a mass content of a, 0.1% ⁇ a ⁇ 5%; the positive electrode sheet contains a positive active material, the Dv99 of the positive active material is y 1 ⁇ m, and y 1 is 5 to 10. In this way, the secondary battery satisfies the following condition: 100 ⁇ y 1 /a ⁇ 1000.
  • the electrolyte salt may also include one or more of lithium hexafluorophosphate (LiPF 6 ), lithium tetrafluoroborate (LiBF 4 ), lithium perchlorate (LiClO 4 ), lithium hexafluoroarsenate (LiAsF 6 ), lithium bistrifluoromethanesulfonyl imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorophosphate (LiPO 2 F 2 ), lithium difluorooxalatoborate (LiDFOB), lithium dioxalatoborate (LiBOB), lithium difluorobisoxalatophosphate (LiDFOP) and lithium tetrafluorooxalatophosphate (LiTFOP).
  • LiPF 6 lithium hexafluorophosphate
  • LiBF 4 lithium perchlorate
  • LiAsF 6 lithium bistrifluoromethanesulf
  • the solvent may include one or more of ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), fluoroethylene carbonate (FEC), methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclopentane sulfone, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.
  • EC ethylene carbonate
  • PC propylene carbonate
  • EMC diethyl carbonate
  • DMC dimethyl carbonate
  • DPC di
  • the electrolyte may further include additives, such as negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, additives that improve battery high or low temperature performance, etc.
  • additives such as negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, additives that improve battery high or low temperature performance, etc.
  • the additives in the electrolyte may include, but are not limited to, one or more of difluoroethylene carbonate (DFEC), trifluoromethylethylene carbonate (TFPC), and the like.
  • DFEC difluoroethylene carbonate
  • TFPC trifluoromethylethylene carbonate
  • the isolation membrane is set between the positive electrode plate and the negative electrode plate, mainly to prevent the positive and negative electrodes from short-circuiting, while allowing ions to pass through.
  • the Gurley value of the isolation film is 100s to 600s.
  • the Gurley value of the isolation film is 150s to 600s; more optionally, the Gurley value of the isolation film is 400s to 600s; or 400s to 500s.
  • the Gurley value of the isolation membrane By controlling the Gurley value of the isolation membrane within the above-mentioned smaller range, its impedance is smaller and its kinetic performance is better. When used in combination with an electrolyte containing LiFSI, it can achieve better fast charging capability.
  • the Gurley value of the isolation membrane can be obtained by testing in the following manner: the isolation membrane is placed in an air permeability tester, and the time required for 100 mL of air to pass through 1 square inch of the isolation membrane is tested at a pressure of 1.22 kPa, in seconds (s).
  • the material of the isolation membrane may include one or more of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride.
  • the isolation membrane may be a single-layer film or a multi-layer composite film, without particular limitation.
  • the materials of each layer may be the same or different, without particular limitation.
  • the thickness of the isolation film is 6 ⁇ m to 40 ⁇ m, and may be 12 ⁇ m to 20 ⁇ m.
  • the positive electrode sheet, the negative electrode sheet and the separator can be formed into an electrode assembly by a winding process or a lamination process.
  • the secondary battery may include an outer package, which may be used to encapsulate the electrode assembly and the electrolyte.
  • the outer packaging of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc.
  • the outer packaging of the secondary battery can also be a soft package, such as a bag-type soft package.
  • the material of the soft package can be plastic, and further, non-limiting examples of plastic can include one or more of polypropylene, polybutylene terephthalate, and polybutylene succinate.
  • the secondary battery includes at least one battery cell.
  • the secondary battery may include one or more battery cells.
  • the secondary battery may also be a battery cell.
  • battery cell refers to a basic unit that can realize the mutual conversion of chemical energy and electrical energy, and further, generally speaking, at least includes a positive electrode sheet, a negative electrode sheet and an electrolyte.
  • active ions are embedded and released back and forth between the positive electrode sheet and the negative electrode sheet.
  • the electrolyte plays the role of conducting active ions between the positive electrode sheet and the negative electrode sheet.
  • FIG1 is a battery cell 5 of a square structure as an example.
  • the outer package may include a shell 51 and a cover plate 53.
  • the shell 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity.
  • the shell 51 has an opening connected to the receiving cavity, and the cover plate 53 can be covered on the opening to close the receiving cavity.
  • the positive electrode sheet, the negative electrode sheet and the isolation film can form an electrode assembly 52 through a winding process or a lamination process.
  • the electrode assembly 52 is encapsulated in the receiving cavity.
  • the electrolyte is infiltrated in the electrode assembly 52.
  • the number of electrode assemblies 52 contained in the battery cell 5 can be one or more, and those skilled in the art can select according to actual needs.
  • the secondary battery may be a battery module 4 or a battery pack 1 .
  • the battery module includes at least one battery cell.
  • the number of battery cells contained in the battery module can be one or more, and those skilled in the art can select a suitable number according to the application and capacity of the battery module.
  • FIG3 is a battery module 4 as an example.
  • a plurality of battery cells 5 may be arranged in sequence along the length direction of the battery module 4. Of course, they may also be arranged in any other manner. Further, the plurality of battery cells 5 may be fixed by fasteners.
  • the battery module 4 may further include a housing having a receiving space, and the plurality of battery cells 5 are received in the receiving space.
  • the battery modules may be assembled into a battery pack.
  • the battery pack may contain one or more battery modules. Those skilled in the art may select a suitable number according to the application and capacity of the battery pack.
  • FIG4 and FIG5 are battery packs 1 as an example.
  • the battery pack 1 may include a battery box and a plurality of battery modules 4 disposed in the battery box.
  • the battery box includes an upper box body 2 and a lower box body 3, and the upper box body 2 can be covered on the lower box body 3 to form a closed space for accommodating the battery modules 4.
  • the plurality of battery modules 4 can be arranged in the battery box in any manner.
  • the present application also provides an electrical device, which includes a secondary battery provided by the present application.
  • the secondary battery can be used as a power source for the electrical device, or as an energy storage unit for the electrical device.
  • the electrical device may include mobile devices, electric vehicles, electric trains, ships and satellites, energy storage systems, etc., but are not limited thereto.
  • the mobile device may be, for example, a mobile phone, a laptop computer, etc.;
  • the electric vehicle may be, for example, a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc., but are not limited thereto.
  • a secondary battery can be selected according to its usage requirements.
  • Fig. 6 is an example of an electric device 6.
  • the electric device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc.
  • a battery pack or a battery module may be used.
  • a device may be a mobile phone, a tablet computer, a notebook computer, etc. Such a device is usually required to be thin and light, and a secondary battery may be used as a power source.
  • the positive electrode active material LiNi 0.68 Co 0.10 Mn 0.22 O 2 , the conductive agent carbon black (Super P), and the binder polyvinylidene fluoride (PVDF) were mixed uniformly in a proper amount of solvent N-methylpyrrolidone (NMP) at a mass ratio of 96.2:2.7:1.1 to obtain a positive electrode slurry; the positive electrode slurry was coated on the positive electrode current collector aluminum foil, and a positive electrode active material layer with a thickness of 38 ⁇ m was formed through drying, cold pressing, slitting, cutting and other processes to obtain a positive electrode sheet.
  • the Dv99 of the positive electrode active material is y 1 ⁇ m, and the Dv50 is y 2 ⁇ m. Please refer to Table 1 for specific values.
  • the negative electrode active material artificial graphite, conductive agent carbon black (Super P), binder styrene butadiene rubber (SBR) and sodium carboxymethyl cellulose (CMC) were mixed evenly in an appropriate amount of solvent deionized water according to a mass ratio of 96.4:0.7:1.8:1.1 to obtain a negative electrode slurry; the negative electrode slurry was coated on the negative electrode current collector copper foil, and a single-side thickness of 54 ⁇ m was formed through drying, cold pressing, striping and cutting processes to obtain a negative electrode active material layer.
  • the compaction density of the negative electrode sheet is 1.45g/ cm3 .
  • a 12 ⁇ m thick polypropylene isolation film was selected; for the Gurley value of the isolation film, please refer to Table 1 for specific values.
  • Ethylene carbonate (EC) and ethyl methyl carbonate (EMC) are mixed in a mass ratio of 30:70 to obtain an organic solvent, LiFSI accounting for 3wt% of the entire electrolyte is dissolved in the mixed solvent, and fully dried LiPF6 is dissolved in the above organic solvent to prepare an electrolyte with a LiPF6 concentration of 1 mol/L.
  • the positive electrode sheet, the separator, and the negative electrode sheet are stacked and wound in order to obtain an electrode assembly; the electrode assembly is placed in an outer package, dried, and then injected with electrolyte, and a secondary battery is obtained after vacuum packaging, standing, forming, shaping, and other processes; the ratio of the mass of the electrolyte to the capacity of the secondary battery is 2.2g/Ah.
  • Table 1 For some specific parameters, please refer to Table 1.
  • the preparation methods of the secondary batteries of Examples 2 to 6 are similar to those of the secondary battery of Example 1, except that the mass content a of LiFSI in the electrolyte is different. Please refer to Table 1 for the specific differences.
  • the secondary batteries of Examples 7 to 15 are prepared in a similar manner to the secondary battery of Example 1, except that the Dv99 (ie, y 1 ) of the positive electrode active material LiNi 0.68 Co 0.10 Mn 0.22 O 2 is different and/or the Dv50 of the positive electrode active material LiNi 0.68 Co 0.10 Mn 0.22 O 2 is different. Please refer to Table 1 for specific differences.
  • the preparation methods of the secondary batteries of Examples 16 to 19 are similar to those of the secondary battery of Example 1, except that the molar ratio of the nickel element and the molar ratio of the cobalt element in the positive electrode active material NCM ternary material are different.
  • the secondary batteries of Examples 20 to 22 are prepared in a similar manner to the secondary battery of Example 1, except that the Gurley values of the isolation membranes are different. Please refer to Table 1 for the specific differences.
  • the secondary batteries of Comparative Examples 1 to 2 are prepared in a similar manner to the secondary battery of Example 1, except that the mass content a of LiFSI in the electrolyte and the Dv99 (i.e., y1) of the positive electrode active material LiNi 0.68 Co 0.10 Mn 0.22 O 2 are different and the value of y1/a is different. For specific differences, see Table 1. For specific differences, see Table 1.
  • each battery is charged with a constant current of 1.0C0, 1.3C0, 1.5C0, 1.8C0, 2.0C0, 2.3C0, 2.5C0, 3.0C0, 3.5C0, 4C0, 4.5C0, and 5C0 in turn to a full battery charge cutoff voltage of 4.4V or a negative electrode cutoff potential of 0V (whichever is reached first).
  • a full battery charge cutoff voltage of 4.4V or a negative electrode cutoff potential of 0V (whichever is reached first).
  • the charge rate is the charging window under the SOC state, which is recorded as C(10%SOC), C(20%SOC), C(30%SOC), C(40%SOC), C(50%SOC), C(60%SOC), C(70%SOC), C(80%SOC).
  • the charging time T of the battery from 10%SOC to 80%SOC is calculated in min. The shorter the time, the better the fast charging performance of the battery.
  • the battery is charged step by step at the charge rates at each SOC obtained from the fast charge capability test.
  • the battery is charged at a charge rate of C (10% SOC) to 10% SOC, then at a charge rate of C (20% SOC) to 20% SOC, then at a charge rate of C (30% SOC) to 30% SOC, then at a charge rate of C (40% SOC) to 40% SOC, then at a charge rate of C (50% SOC) to 60% SOC.
  • the battery was then charged at a constant current of 0.33C to 50% SOC, then charged at a constant current of C(60% SOC) to 60% SOC, then charged at a constant current of C(70% SOC) to 70% SOC, then charged at a constant current of C(80% SOC) to 80% SOC, then charged at a constant current of 0.33C to 100% SOC, and then discharged at a rate of 0.33C to 2.5V. Cycle according to the above process and record the number of cycles when the battery decays to 80% SOC.
  • the number of cycles when decaying to 80% SOH is calculated by the following method: divide the discharge capacity of the nth cycle by the discharge capacity of the first cycle from small to large, and record the ratios respectively; when the ratio is equal to or less than 80% SOH for the first time, this number of cycles is the number of cycles when decaying to 80% SOH, that is, the fast charging cycle life parameter in Table 2.
  • Hot box safety test The battery cell is fully charged to the corresponding design upper limit voltage, and the battery cell is equipped with a clamp.
  • the temperature inside the hot box starts from room temperature and is increased at 2°C/min to 100°C. It is kept for 1 hour, and then increased at 5°C/min, and maintained for 30 minutes every 5°C until the battery cell fails (smoke or fire occurs when the valve is opened).
  • the test is stopped, the upper limit temperature is set to 250°C, and the temperature inside the hot box when the battery cell fails is recorded.
  • the temperature inside the hot box can represent the safety performance of the hot box. The specific values are shown in the hot box safety performance (°C) in Table 2.
  • the fast charge time in Table 2 can characterize the fast charge performance of the secondary battery. The shorter the fast charge time, the better the fast charge performance of the battery.
  • the fast charge cycle life (number of cycles at 80% SOH) can characterize the cycle life of the battery. The larger the fast charge cycle life (number of cycles at 80% SOH), the better the fast charge cycle life.
  • the fast charging temperature rise and hot box safety test in Table 2 can characterize the thermal runaway caused by the excessive temperature rise during fast charging.
  • the smaller the fast charging temperature rise the smaller the risk of thermal runaway caused by the excessive temperature rise during fast charging, and the better the temperature rise performance; the higher the furnace temperature when the hot box safety test cell fails, the smaller the risk of thermal runaway caused by the excessive temperature rise during fast charging, and the better the hot box safety performance.
  • the Dv99 of the positive electrode active material of Comparative Example 1 is larger, and y1/a is larger, and the fast charging time T of its secondary battery is larger, the cycle life is smaller, and the temperature rise is larger, indicating that the fast charging performance of the battery is poor, the cycle life is poor, and the temperature rise is large; in Comparative Example 2, a is larger, y 1 /a is smaller, the cycle life of the secondary battery is deteriorated, the furnace temperature when the battery cell fails is lower, and the hot box safety performance is poor.
  • each embodiment can ensure that the secondary battery has a better fast-charging cycle life.
  • controlling 200 ⁇ y 1 /a ⁇ 5000 can further improve the fast charging performance and cycle life of the battery, while having lower temperature rise and better hot box safety performance.
  • Controlling 200 ⁇ y 1 /a ⁇ 600 can further improve the comprehensive performance of the secondary battery.
  • the secondary batteries of Examples 7 to 9 differ from those of Example 1 in that the Dv99 (ie, y 1 ) of the positive electrode active material is different, and all have good comprehensive performance. Further, by controlling the Dv99 of the positive electrode active material to be 5 to 12 ⁇ m, the secondary batteries have better fast charging performance and lower temperature rise.
  • the secondary batteries of Examples 12 to 15 differ from those of Example 1 in that the positive electrode active material Dv50 (i.e., y 2 ) is different, and y 1 /y 2 is correspondingly different, and both have good comprehensive performance. Further, when y 2 is in the range of 2 to 5 and y 1 /y 2 is in the range of 2 to 6, the secondary batteries have better fast charging performance and cycle life, as well as lower temperature rise and better safety performance.
  • the secondary batteries of Examples 16 to 19 differ from those of Example 1 in that the nickel content and cobalt content of the positive electrode active material are different.
  • the molar ratio of the cobalt element is 9% to 15% and the molar ratio of the nickel element is 50% to 70%, the secondary batteries have better cycle life and better hot box safety performance.
  • the secondary batteries of Examples 20 to 22 differ from those of Example 1 in that the Gurley values of the separators are different, and both have good fast charging performance and the effect of reducing the risk of thermal runaway caused by excessive temperature rise during fast charging. Furthermore, the Gurley value of the separator is in the range of 400 to 600 seconds, and the secondary batteries have better cycle life and better hot box safety performance.

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Abstract

本申请涉及一种二次电池及用电装置。该二次电池包括正极极片、负极极片及设于所述正极极片与所述负极极片之间的电解液；所述电解液包括质量含量为a的LiFSI；所述正极极片含有正极活性材料，所述正极活性材料的Dv99为y1μm，y1为5～15；所述二次电池满足如下条件：100≤y1/a≤10000。上述二次电池，电解液中添加LiFSI可以改善温升，但LiFSI太多，由于其本身不耐氧化，会影响电池寿命；采用Dv99值较小的正极活性材料，可以改善温升，但是Dv99太小会恶化电池寿命。本申请通过控制Dv99与LiFSI含量的关系，实现快充过程中的温升，同时规避LiFSI和Dv99带来的寿命问题。

Description

二次电池及用电装置
相关申请
本申请要求2023年11月17日提交中国专利局、申请号为2023115348647，名称为“二次电池及用电装置”的中国专利申请的优先权，其全部内容通过引用结合在本申请中。
技术领域
本申请涉及新能源技术领域，特别是涉及一种二次电池及用电装置。
背景技术
近年来，锂离子电池等二次电池的应用范围越来越广泛，例如广泛应用于水力、火力、风力和太阳能电站等储能电源系统，以及电动工具、电动自行车、电动摩托车、电动汽车、军事装备、航空航天等多个领域。随着锂离子电池取得了极大的发展，因此对其快充性能也提出了更高的要求，特别是如何解决快充过程中的温升过快带来的热量失控问题。
发明内容
本申请提供一种能够改善快充性能及快充电过程中的温升过快带来的热量失控问题的二次电池及用电装置。
为了达到上述目的，本申请的第一方面提供了一种二次电池，包括正极极片、负极极片及设于所述正极极片与所述负极极片之间的电解液；
所述电解液包括质量含量为a的LiFSI；所述正极极片含有正极活性材料，所述正极活性材料的Dv99为y1μm，y1为5～15；所述二次电池满足如下条件：100≤y1/a≤10000。
不希望限于任何理论，本申请上述的二次电池，电解液中添加LiFSI可以改善温升，但LiFSI太多，由于其本身不耐氧化，会影响电池寿命；采用Dv99值较小的正极活性材料，可以改善温升，但是Dv99太小会恶化电池寿命。本申请通过控制Dv99与LiFSI含量的关系，实现快充过程中的温升，同时规避LiFSI和Dv99带来的寿命问题。
在本申请的一些实施方式中，所述二次电池满足如下条件中的至少一个：
(1)y1为5～12；
(2)0＜a≤10％；
(3)200≤y1/a≤5000。
在本申请的一些实施方式中，y1为5～10。
在本申请的一些实施方式中，0.01％≤a≤10％。
在本申请的一些实施方式中，0.1％≤a≤5％。
在本申请的一些实施方式中，所述二次电池满足如下条件中的至少一个：
(1)1％≤a≤5％；
(2)200≤y1/a≤600。
在本申请的一些实施方式中，2％≤a≤4％。
在本申请的一些实施方式中，所述正极活性材料的Dv50为y2μm，所述二次电池满足如下条件：1.2≤y1/y2≤7。
控制正极活性材料的Dv99与Dv50的比值，使得二次电池能够兼顾优异的快充性能、循环寿命及热箱安全性能，同时具有较低的温升。
在本申请的一些实施方式中，所述二次电池满足如下条件中的至少一个：
(1)y2为1.5～6；
(2)2≤y1/y2≤6。
在本申请的一些实施方式中，y2为2～5。可选的，y2为3～5。
y2在1.5～6、2～5范围及3～5范围，y1/y2在2-6范围，电池具有较优的循环寿命和热箱安全性能。
在本申请的一些实施方式中，所述正极活性材料包括镍钴锰三元正极材料。
在本申请的一些实施方式中，在所述镍钴锰三元正极材料的镍元素、钴元素和锰元素摩尔总量中，钴元素的摩尔占比为5％～15％，镍元素的摩尔占比为50％-90％；
在本申请的一些实施方式中，在所述镍钴锰三元正极材料的镍元素、钴元素和锰元素摩尔总量中，钴元素的摩尔占比为9％～15％，镍元素的摩尔占比为50％-70％。
镍元素的摩尔占比和钴元素的摩尔占比控制在该范围内，使得电池具有更优的循环寿命和热箱安全性能。
在本申请的一些实施方式中，所述负极极片的压实密度≤1.6g/cm3。
在本申请的一些实施方式中，所述二次电池还包括设于所述正极极片与所述负极极片之间的隔离膜，所述隔离膜的Gurley值为100s～600s；
在本申请的一些实施方式中，所述隔离膜的Gurley值为400s～500s。
本申请的第二方面还提供一种用电装置，包括本申请的第一方面的二次电池。
本申请的用电装置包括本申请提供的二次电池，因而至少具有与所述二次电池相同的优势。
本申请的一个或多个实施例的细节在下面的附图和描述中提出。本申请的其他特征、目的和优点将从说明书、附图以及权利要求书变得明显。
附图说明
为了更好地描述和说明本申请提供的实施例或示例，可以参考一幅或多幅附图。用于描述附图的附加细节或示例不应当被认为是对所公开的申请、目前描述的实施例或示例以及目前理解的这些申请的最佳模式中的任何一者的范围的限制。而且在全部附图中，用相同的附图标号表示相同的部件。在附图中：
图1为本申请一实施方式的电池单体的示意图。
图2为图1所示的本申请一实施方式的电池单体的分解图。
图3为本申请一实施方式的电池模块的示意图。
图4为本申请一实施方式的电池包的示意图。
图5为图4所示的本申请一实施方式的电池包的分解图。
图6为本申请一实施方式的二次电池用作电源的用电装置的示意图。
附图标记说明：
1电池包；2上箱体；3下箱体；4电池模块；5电池单体；51壳体；52电极组件；53
盖板；6用电装置。
具体实施方式
以下，适当地参照附图详细描述了本申请的二次电池和用电装置的一些实施方式。但是会有省略非必要的详细说明的情况。例如，有省略对已众所周知的事项的详细说明、实际相同结构的重复说明的情况。这是为了避免以下的说明不必要地变得冗长，便于本领域技术人员的理解。此外，附图及以下说明是为了本领域技术人员充分理解本申请而提供的，并不旨在限定权利要求书所记载的主题。
本申请所公开的“范围”可以采用下限和上限的形式来限定，给定范围是通过选定一个下限和一个上限进行限定的，选定的下限和上限限定了特别范围的边界。这种方式进行限定的范围可以是包括端值或不包括端值的，任一个端值可以独立地被包括或不被包括，并且可以进行任意地组合，即任何下限可以与任何上限组合形成一个范围。例如，如果针对特定参数列出了60-120和80-110的范围，理解为60-110和80-120的范围也是预料到的。此外，如果列出的最小范围值1和2，且如果还列出了最大范围值3，4和5，则下面的范围可全部预料到：1-3、1-4、1-5、2-3、2-4和2-5。在本申请中，除非有其他说明，数值范围“a-b”表示a到b之间的任意实数组合的缩略表示，其中a和b都是实数。例如数值范围“0-5”表示本文中已经全部列出了“0-5”之间的全部实数，“0-5”只是这些数值组合的缩略表示。另外，当表述某个参数为≥2的整数，则相当于列出了该参数为例如整数2、3、4、5、6、7、8、9、10、11、12等。比如，当表述某个参数为选自“2-10”的整数，相当于列出了整数2、3、4、5、6、7、8、9和10。
本申请中涉及“多个”、“多种”等，如无特别限定，指在数量上大于2或等于2。例如，“一种或多种”表示一种或大于等于两种。
如果没有特别的说明，本申请的所有实施方式以及可选实施方式可以相互组合形成新的技术方案。
在本文中提及“实施例”意味着，结合实施例描述的特定特征、结构或特性可以包含在本申请的至少一个实施例或实施方式中。在说明书中的各个位置出现该短语并不一定均是指相同的实施例，也不是与其它实施例互斥的独立的或备选的实施例。本领域技术人员显式地和隐式地理解的是，本文所描述的实施例可以与其它实施例相结合。在本文中提及的“实施方式”具有类似理解。
本领域技术人员可以理解，在各实施方式或实施例的方法中，各步骤的撰写顺序并不意味着严格的执行顺序而对实施过程构成任何限定，各步骤的详细执行顺序应当以其功能和可能的内在逻辑确定。如果没有特别的说明，本申请的所有步骤可以顺序进行，也可以随机进行，优选是顺序进行的。例如，所述方法包括步骤(a)和(b)，表示所述方法可包括顺序进行的步骤(a)和(b)，也可以包括顺序进行的步骤(b)和(a)。例如，所述提到所述方法还可包括步骤(c)，表示步骤(c)可以任意顺序加入到所述方法，例如，所述方法可以包括步骤(a)、(b)和(c)，也可包括步骤(a)、(c)和(b)，也可以包括步骤(c)、(a)和(b)等。
在本申请中，以“含有”、“包含”、“包括”等词语描述的开放式技术特征或技术方案中，如无其他说明，不排除所列成员之外的额外成员，可视为既提供了由所列成员构成的封闭式特征或方案，还提供了在所列成员之外还包括额外成员的开放式特征或方案。例如，A包括a1、a2和a3，如无其他说明，可以还包括其他成员，也可以不包括额外成员，可视为既提供了“A由a1、a2和a3组成”的特征或方案，还提供了“A不仅包括a1、a2和a3，还包括其他成员”的特征或方案。在本申请中，如无其他说明，A(如B)，表示B为A中的一种非限制性示例，可以理解A不限于为B。
在本申请中，“可选地”、“可选的”、“可选”，指可有可无，也即指选自“有”或“无”两种并列方案中的任一种。如果一个技术方案中出现多处“可选”，如无特别说明，且无矛盾之处或相互制约关系，则每项“可选”各自独立。
以下适当参照附图对本申请的二次电池和用电装置进行说明。
通常情况下，二次电池包括正极极片、负极极片和电解质。电解质位于正极极片与负极极片之间。在电池充放电过程中，活性离子在正极极片和负极极片之间往返嵌入和脱出。电解质在正极极片和负极极片之间起到传导离子的作用。一般地，电解质为液态的，即电解液。
此外，一般地，二次电池还包括隔离膜。隔离膜设置在正极极片和负极极片之间，主要起到防止正负极短路的作用，同时可以使离子通过。
本申请一实施方式提供了一种二次电池，包括正极极片、负极极片及设于正极极片与负极极片之间的电解液。电解液包括质量含量为a的LiFSI。正极极片含有正极活性材料，正极活性材料的Dv99为y1μm，y1为5～15；二次电池满足如下条件：100≤y1/a≤1000。
不希望限于任何理论，本申请上述的二次电池，电解液中添加LiFSI可以改善温升，但LiFSI太多，由于其本身不耐氧化，会影响电池寿命；采用Dv99值较小的正极活性材料，可以改善温升，但是Dv99太小会恶化电池寿命。本申请通过控制Dv99与LiFSI含量的关系，实现快充过程中的温升，同时规避LiFSI和Dv99带来的寿命问题。
y1/a反映了正极活性材料的Dv99值和LiFSI含量的关系。y1/a太大，意味着Dv99太大或者LiFSI含量太少，均会影响电池的温升；而y1/a太小意味着，y1太小或者LiFSI含量太少太多，均会影响电池的循环寿命。通过控制Dv99值和LiFSI含量在合适的范围内，能够得到温升性能和循环寿命较佳的二次电池。
Dv99为本领域公知的含义，可以采用本领域已知的方法测试。例如，使用激光粒度分析仪(如Malvern Master Size 3000)测定。其中，Dv99表示根据粒径体积分布，从小粒径起，粒子的体积分布百分数累积到99％时所对应的粒径大小。Dv50表示根据粒径体积分布，从小粒径起，粒子的体积分布百分数累积到50％时所对应的粒径大小。
粒径体积分布可通过如下方法测试得到：取一洁净烧杯，加入适量待测样品，充分超声以确保样品完全分散。测试仪器为美国马尔文2000。样品倒入进样塔后随溶液循环到测试光路系统，颗粒在激光束的照射下，通过接受和测量散向光的能量分布就可以得出颗粒的粒度分布特征(遮光度：8-12％)。根据测试数据绘制粒径体积分布图。
正极极片
正极极片包括正极集流体以及设置在正极集流体至少一个表面的正极活性材料层，正极活性材料层包括上述的正极活性材料。
作为非限制性示例，正极集流体具有在其自身厚度方向相对的两个表面，正极活性材料层设置在正极集流体相对的两个表面的其中任意一者或两者上。
在其中一些实施例中，正极集流体可采用金属箔片或复合集流体。例如，作为金属箔片，可采用铝箔。复合集流体可包括高分子材料基层和形成于高分子材料基层至少一个表面上的金属层。复合集流体可通过将金属材料形成在高分子材料基材上而获得。所述正极集流体中，该金属材料的非限制性示例可以包括铝、铝合金、镍、镍合金、钛、钛合金、银及银合金等中的一种或多种。所述正极集流体中，该高分子材料基材的非限制性示例可以包括聚丙烯(PP)、聚对苯二甲酸乙二醇酯(PET)、聚对苯二甲酸丁二醇酯(PBT)、聚苯乙烯(PS)、聚乙烯(PE)等基材中的一种或多种。
在其中一些实施例中，单面正极活性材料层的厚度为26～68μm。
作为示例，正极活性材料的Dv99为y1μm，y1可为5μm、6μm、7μm、8μm、9μm、10μm、11μm、12μm、13μm、14μm、15μm，或为上述任意两点值构成的范围。在其中一些实施例中，y1为5～12；换言之，正极活性材料的Dv99为5～12μm。通过控制正极活性材料的Dv99在合适的范围内，可以避免电池有较大温升，同时避免严重的副反应发生，使得二次电池具有较优的循环寿命和较低的温升。进一步地，y1为5～10。
具有以上粒径的正极活性材料可以通过市场购买获取，也可以自行制备。具体的制备方法可以采用公知的制备方法，以镍钴锰三元材料为例，具体制备步骤可以为：
步骤一，制备氢氧化物前驱体NixCoyM1-x-y(OH)2；用Ni盐、Co盐和M盐配置金属盐溶液，金属离子总浓度为1.0～5.0mol/L；将金属盐溶液与氨碱混合溶液在反应釜中进行共沉淀反应制备获得前驱体NixCoyM1-x-y(OH)2；其中，0＜x＜1，0＜y＜1，0＜1-x-y＜1。
步骤二，制备三元正极材料LiNixCoyM1-x-yO2；将步骤一获得的前驱体与助熔剂、LiOH·H2O研磨混合均匀；将混合物于氧气气氛下烧结，控制温度在700～1000℃，时间为8～20h；将烧结后的物料研磨、水洗、抽滤后干燥；干燥后将物料于氧气气氛下回烧，控制条件为750～1000℃回烧1～10h；即得到三元正极材料LiNixCoyM1-x-yO2；
可选的，也可以对以上三元正极材料进行表面包覆，具体的；将步骤二获得的三元正极材料与包覆原料研磨混合；将混合物于氧气气氛下烧结，控制烧结条件为700～1000℃、3～15h；包覆原料可以为LiOH·H2O或Li2O中的一种或两种。
在其中一些实施例中，正极活性材料的Dv50为y2μm，所述二次电池满足如下条件：1.2≤y1/y2≤7。可选地，2≤y1/y2≤6。
作为示例，y1/y2的取值可以为1.2、1.5、1.8、2、2.5、2.8、2.9、3、3.4、3.5、3.8、4、4.2、4.5、6、6.5、7，或为上述任意两点值构成的范围。
可选地，y2为1.5～6；更可选地，y2为2～5，更可选地，y2为3～5。
作为示例，正极活性材料的Dv50可为1.5μm、2μm、2.5μm、2.9μm、2.9μm、3.5μm、4μm、4.5μm、5μm、5.5μm、5.6μm、5.8μm、6μm，或为上述任意两点值构成的范围。通过控制材料的Dv50在合适的范围内，可以避免电池有较大温升，同时避免严重的副反应发生，使得二次电池具有较优的循环寿命和较低的温升。
控制正极活性材料的Dv99与Dv50的比值，从而控制正极活性材料的Dv50在合适范围，以此来限定正极活性材料的颗粒大小分布，能够兼顾优异的快充性能、循环寿命及热箱安全性能，同时具有较低的温升。
当y2在1.5～6、2～5以及3～5范围，y1/y2在2～6范围，电池具有较优的循环寿命和热箱安全性能都较好。y1/y2意味着Dv99和Dv50值的差异，比值越大说明两者差异较大，比值越小说明两者差异越小。差异越小，说明正极活性材料的粒径越均匀，越容易形成锂离子传输路径，提高快充性能，但Dv50较大容易提高快充温升。差异越大，说明正极活性材料的粒径不均匀，大小不同的粒径搭配，能够提高能量密度，但Dv50较小有利于降低温升，却会增加副反应，降低循环寿命和热箱安全性能。通过控制正极活性材料的Dv99和Dv50的比值范围，能够使得电池具有较好的综合性能。
在其中一些实施例中，正极活性材料可采用本领域公知的用于电池的正极活性材料。作为非限制性示例，正极活性材料可包括以下材料中的一种或多种：橄榄石结构的含锂磷酸盐、锂过渡金属氧化物及其各自的改性化合物。但本申请并不限定于这些材料，还可以使用其他可被用作电池正极活性材料的传统材料。这些正极活性材料可以仅单独使用一种，也可以将两种以上组合使用。其中，锂过渡金属氧化物的示例可包括但不限于锂钴氧化物(如LiCoO2)、锂镍氧化物、锂锰氧化物、锂镍钴氧化物、锂锰钴氧化物、锂镍锰氧化物、镍钴锰三元正极材料(或称为锂镍钴锰氧化物)、锂镍钴铝氧化物及其改性化合物等中的一种或多种。
橄榄石结构的含锂磷酸盐的非限制性示例可包括但不限于磷酸铁锂、磷酸铁锂与碳的复合材料、磷酸锰锂、磷酸锰锂与碳的复合材料、磷酸锰铁锂、磷酸锰铁锂与碳的复合材料中一种或多种。
锂钴氧化物的非限制性示例可以包括LiCoO2；锂镍氧化物的非限制性示例可以包括LiNiO2；锂锰氧化物的非限制性示例可以包括LiMnO2、LiMn2O4等；锂镍钴铝氧化物的非限制性示例可以包括LiNi0.85Co0.15Al0.05O2。
镍钴锰三元正极材料(或称为锂镍钴锰氧化物)的非限制性示例可以包括LiNi1/3Co1/3Mn1/3O2(也可以简称为NCM333)、LiNi0.5Co0.2Mn0.3O2(也可以简称为NCM523)、LiNi0.5Co0.25Mn0.25O2(也可以简称为NCM211)、LiNi0.5Co0.15Mn0.35O2、LiNi0.6Co0.2Mn0.2O2(也可以简称为NCM622)、LiNi0.8Co0.1Mn0.1O2(也可以简称为NCM811)、LiNi0.85Co0.05Mn0.1O2、LiNi0.64Co0.09Mn0.27O2、LiNi0.68Co0.10Mn0.22O2等。可理解，镍钴锰三元正极材料还可掺杂有其他金属元素。
可以理解地，电池在充放电过程中会伴随锂(Li)的脱嵌及消耗，电池在放电到不同状态时正极活性材料中Li的含量不同。本申请中关于正极活性材料的列举中，如无其他说明，Li的含量为材料初始状态。将正极活性材料应用于电池体系中的正极极片，经过充放电循环，极片所含正极活性材料中Li的含量通常会发生变化。其中，Li的含量可以采用摩尔占比进行计量，但不限于此。关于“Li的含量为材料初始状态”，材料初始状态指投料于正极浆料之前的状态。可以理解，在所列举正极活性材料基础上进行适当改性而获得的新材料也在正极活性材料范畴之内，前述适当改性指针对正极活性材料可接受的改性方式，非限制性示例如包覆改性。
本申请中关于正极活性材料的列举中，氧(O)的含量仅为理论状态值，晶格释氧会导致氧的摩尔占比发生变化，实际O的含量会出现浮动。其中，O的含量可以采用摩尔占比进行计量，但不限于此。
在其中一些实施例中，正极活性材料包括镍钴锰三元正极材料。
进一步地，在镍钴锰三元正极材料的镍元素、钴元素和锰元素摩尔总量中，钴元素的摩尔占比为5％～15％，Ni元素的摩尔占比为50％～90％。可选的，钴元素的摩尔占比为9％～15％，Ni元素的摩尔占比为50％～70％。作为示例，Ni元素的摩尔占比的取值可为50％、55％、60％、64％、65％、68％、70％、75％、80％、85％、90％。钴元素的摩尔占比的取值可为5％、6％、9％、10％、12％、15％。控制正极活性材料的Ni含量和Co含量，使得电池具有较优的循环寿命和热箱安全性能。Ni含量较高可以获得更高的能量密度，但Ni含量过高，会恶化电池的循环寿命和热箱安全性能。
其中，正极活性材料中各元素(比如镍钴锰元素)的摩尔含量可以采用本领域内公知的方法，比如采用ICP方法(微量元素分析-电感耦合等离子体发射光谱法)，采用电感耦合等离子体发射光谱仪iCAP 7400进行测试分析。
可选地，镍钴锰三元正极材料的表层钴元素的摩尔占比＞内层钴元素的摩尔占比。换言之，镍钴锰三元正极材料的内层和表层的组成有所差异，其内层钴元素的摩尔占比较小，而表层钴元素的摩尔占比较大。镍钴锰三元正极材料Co的梯度设置，能够有效稳定正极活性材料的结构，改善正极极片的动力学性能。
可理解，在一些示例中，可通过采用不同组成的前驱体多次包覆的方式实现内层和表层钴元素的摩尔占比的差异化。可理解，具体的实现方式不限于此。
在其中一些实施例中，正极活性材料层还可选地包括粘结剂。作为非限制性示例，粘结剂可以包括聚偏氟乙烯(PVDF)、聚四氟乙烯(PTFE)、偏氟乙烯-四氟乙烯-丙烯三元共聚物、偏氟乙烯-六氟丙烯-四氟乙烯三元共聚物、四氟乙烯-六氟丙烯共聚物及含氟丙烯酸酯树脂中的一种或多种。
在其中一些实施例中，正极活性材料层还可选地包括导电剂。作为非限制性示例，导电剂可以包括超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯及碳纳米纤维中的一种或多种。
在其中一些实施例中，在正极活性材料层中，正极活性材料的质量含量为75％～98％。
在其中一些实施例中，在正极活性材料层中，导电剂的质量含量为0.1％～15％。
在其中一些实施例中，在正极活性材料层中，粘结剂的质量含量为0.5％～15％。
在其中一些实施例中，可以通过以下方式制备正极极片：将上述用于制备正极极片的组分，例如正极活性材料、导电剂、粘结剂和任意其他的组分分散于溶剂中，形成正极浆料；将正极浆料涂覆在正极集流体的至少一侧表面上，经烘干、冷压等工序后，即可得到正极极片。
溶剂的种类可以选自但不限于前述实施方式中的任一种，例如N-甲基吡咯烷酮(NMP)。正极浆料所涂覆的正极集流体表面可以为正极集流体的单个表面上，也可以为正极集流体的两个表面上。正极浆料所涂覆的正极集流体表面可以为正极集流体的单个表面上，也可以为正极集流体的两个表面上。正极浆料的固含量可以为40wt％～80wt％。正极浆料在室温下的粘度可以调整到5000～25000mPa·s。涂覆正极浆料时，以干重计(扣除溶剂)的涂布单位面密度可以为15～35mg/cm2。正极极片的压实密度可以为3.0～3.6g/cm3，可选为3.3～3.5g/cm3。
负极极片
通常地，负极极片包括负极集流体以及设置在负极集流体至少一个表面上的负极膜层。
作为非限制性示例，负极集流体具有在其自身厚度方向相对的两个表面，负极活性材料层设置在负极集流体相对的两个表面中的任意一者或两者上。
在其中一些实施例中，负极集流体可采用金属箔片或复合集流体。例如，作为金属箔片，可以采用铜箔。复合集流体可包括高分子材料基层和形成于高分子材料基材至少一个表面上的金属层。复合集流体可通过将金属材料形成在高分子材料基材上而获得。所述负极集流体中，该金属材料的非限制性示例可以包括铜、铜合金、镍、镍合金、钛、钛合金、银及银合金等中的一种或多种。所述负极集流体中，该高分子材料基材的非限制性示例可以包括聚丙烯(PP)、聚对苯二甲酸乙二醇酯(PET)、聚对苯二甲酸丁二醇酯(PBT)、聚苯乙烯(PS)、聚乙烯(PE)等基材中的一种或多种。
进一步地，负极膜层可包括负极活性材料层，负极活性材料层包括负极活性材料。
在其中一些实施例中，单面负极活性材料层的厚度为22～110μm。
在其中一些实施例中，负极活性材料可采用本领域公知的用于电池的负极活性材料。作为非限制性示例，负极活性材料可包括以下材料中的一种或多种：人造石墨、天然石墨、软炭、硬炭、硅基材料、锡基材料和钛酸锂等。硅基材料可以包括单质硅、硅氧化合物、硅碳复合物、硅氮复合物以及硅合金中的一种或多种。锡基材料可以包括单质锡、锡氧化合物以及锡合金中的一种或多种。但本申请并不限定于这些材料，还可以使用其他可被用作电池负极活性材料的传统材料。这些负极活性材料可以仅单独使用一种，也可以将两种以上组合使用。
在其中一些实施例中，负极活性材料层还可选地包括粘结剂。粘结剂可以包括丁苯橡胶(SBR)、聚丙烯酸(PAA)、聚丙烯酸钠(PAAS)、聚丙烯酰胺(PAM)、聚乙烯醇(PVA)、海藻酸钠(SA)、聚甲基丙烯酸(PMAA)及羧甲基壳聚糖(CMCS)中的一种或多种。
在其中一些实施例中，负极活性材料层还可选地包括导电剂。导电剂可以包括超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯及碳纳米纤维中的一种或多种。
在其中一些实施例中，负极活性材料层还可选地包括其他助剂，例如增稠剂(如羧甲基纤维素钠(CMC-Na))等。
在其中一些实施例中，在负极膜层中，负极活性材料的质量含量为75％～98％。
在其中一些实施例中，在负极膜层中，导电剂的质量含量为0.1％～15％。
在其中一些实施例中，在负极膜层中，粘结剂的质量含量为0.5％～15％。
在其中一些实施例中，负极极片的压实密度为小于1.6g/cm2；可选为1.3～1.5g/cm2。控制负极极片较小的压实密度设置，能够使得负极极片内部具有较大的孔隙，从而改善电解液的浸润，改善Li+的传输，进而提升二次电池整体的动力学性能，有利于改善快充性能。可理解，负极极片的压实密度是指负极极片上的负极膜层的压实密度。压实密度测试：拆解电芯取极片，并冲切成面积为S的小圆片，测量小圆片的重量M和厚度L，取另外一层极片，将表面的膜片层擦除剩余空的集流体箔材，同样冲切成S的小圆片，称量空铝箔质量M0，则压实密度PD＝(M-M0)/(S*n*L)，其中n为涂布于集流体的膜片层的数量，为1或2，单面涂布或双面涂布。在一具体示例中，S为1540.25mm2。
在其中一些实施例中，可以通过以下方式制备负极极片：将上述用于制备负极极片的组分，例如负极活性材料、导电剂、粘结剂和任意其他组分分散于溶剂(溶剂的非限制性示例如去离子水)中，形成负极浆料；将负极浆料涂覆在负极集流体的至少一侧表面上，经烘干、冷压等工序后，即可得到负极极片。
负极浆料所涂覆的负极集流体表面可以为负极集流体的单个表面上，也可以为负极集流体的两个表面上。负极浆料的固含量可以为40wt％～60wt％。负极浆料在室温下的粘度可以调整到2000-10000mPa·s。
电解质
电解质具有在正极极片和负极极片之间传导离子的作用。本申请电解质采用电解液。电解液包括电解质盐和溶剂。如上所述，电解液包括质量含量为a的LiFSI。
在其中一些实施例中，0＜a≤10％；作为示例，a的取值可为0.01％、0.02％、0.05％、0.1％、0.5％、1％、2％、3％、4％、5％、6％、7％、8％、9％、10％，或为上述任意两点值构成的范围。可选地，0.01％≤a≤10％，可选地，0.1％≤a≤5％；进一步地，1％≤a≤5％，更可选地，1％＜a≤5％。
进一步地，2％≤a≤4％，更可选地，2％＜a≤4％。
作为示例，y1/a的取值可为100、120、150、160、167、170、200、233、300、330、333、340、400、500、600、1000、2000、3000、4000、5000、6000、7000、8000、9000、10000。y1/a的取值范围可为上述任意两点值构成的范围。进一步地，200≤y1/a≤5000，或者100≤y1/a≤5000；200≤y1/a≤600；或为上述任意两个点值构成的范围。
在其中一些实施例中，电解液包括质量含量为a的LiFSI，0.1％≤a≤5％；正极极片含有正极活性材料，正极活性材料的Dv99为y1μm，y1为5～10。如此使得二次电池满足如下条件：100≤y1/a≤1000。
在其中一些实施例中，电解质盐还可以包括六氟磷酸锂(LiPF6)、四氟硼酸锂(LiBF4)、高氯酸锂(LiClO4)、六氟砷酸锂(LiAsF6)、双三氟甲磺酰亚胺锂(LiTFSI)、三氟甲磺酸锂(LiTFS)、二氟磷酸锂(LiPO2F2)、二氟草酸硼酸锂(LiDFOB)、二草酸硼酸锂(LiBOB)、二氟二草酸磷酸锂(LiDFOP)及四氟草酸磷酸锂(LiTFOP)中的一种或多种。
在其中一些实施例中，溶剂可以包括碳酸乙烯酯(EC)、碳酸丙烯酯(PC)、碳酸甲乙酯(EMC)、碳酸二乙酯(DEC)、碳酸二甲酯(DMC)、碳酸二丙酯(DPC)、碳酸甲丙酯(MPC)、碳酸乙丙酯(EPC)、氟代碳酸乙烯酯(FEC)、甲酸甲酯、乙酸甲酯、乙酸乙酯、乙酸丙酯、丙酸甲酯、丙酸乙酯、丙酸丙酯、丁酸甲酯、丁酸乙酯、1,4-丁内酯、环丁砜、二甲砜、甲乙砜及二乙砜中的一种或多种。
在其中一些实施例中，电解液还可选地包括添加剂。例如添加剂可以包括负极成膜添加剂、正极成膜添加剂，还可以包括能够改善电池某些性能的添加剂，例如改善电池过充性能的添加剂、改善电池高温或低温性能的添加剂等。
在一些实施方式中，电解液中的添加剂可以包括但不限于二氟碳酸乙烯酯(DFEC)、三氟甲基碳酸乙烯酯(TFPC)等中的一种或多种。
隔离膜
隔离膜设置在正极极片和负极极片之间，主要起到防止正负极短路的作用，同时可以使离子通过。
在其中一些实施例中，隔离膜的Gurley值为100s～600s。
可选地，隔离膜的Gurley值为150s～600s；更可选地，隔离膜的Gurley值为400s～600s；或为400s～500s。
控制隔离膜的Gurley值在上述较小的范围内，其阻抗较小，动力学性能较好，与含有LiFSI的电解液搭配使用，可以实现更优异的快速充电能力。
隔离膜的Gurley值可通过如下方式测试得到：将隔离膜置于透气度测试仪中，在1.22kPa压力下测试100mL空气通过1平方英寸隔离膜所需的时间，单位为秒(s)。
在其中一些实施例中，隔离膜的材质可以包括玻璃纤维、无纺布、聚乙烯、聚丙烯及聚偏二氟乙烯中的一种或多种。隔离膜可以是单层薄膜，也可以是多层复合薄膜，没有特别限制。在隔离膜为多层复合薄膜时，各层的材料可以相同或不同，没有特别限制。
在一些实施方式中，隔离膜的厚度为6μm～40μm，可选为12μm～20μm。
在其中一些实施例中，正极极片、负极极片和隔离膜可通过卷绕工艺或叠片工艺制成电极组件。
在其中一些实施例中，二次电池可包括外包装。该外包装可用于封装上述电极组件及电解质。
在其中一些实施例中，二次电池的外包装可以是硬壳，例如硬塑料壳、铝壳、钢壳等。二次电池的外包装也可以是软包，例如袋式软包。软包的材质可以是塑料，进一步地，塑料的非限制性示例可以包括聚丙烯、聚对苯二甲酸丁二醇酯以及聚丁二酸丁二醇酯等中的一种或多种。
二次电池中包括至少一个电池单体。二次电池可以包括1个或多个电池单体。在一示例中，二次电池也可为电池单体。
在本申请中，如无其他说明，“电池单体”指能够实现化学能和电能相互转化的基本单元，进一步地，通常而言至少包括正极极片、负极极片和电解质。在电池充放电过程中，活性离子在正极极片和负极极片之间往返嵌入和脱出。电解质在正极极片和负极极片之间起到传导活性离子的作用。
本申请对电池单体的形状没有特别的限制，其可以是圆柱形、方形或其他任意的形状。例如，图1是作为一个示例的方形结构的电池单体5。
在其中一些实施例中，参照图2，外包装可包括壳体51和盖板53。其中，壳体51可包括底板和连接于底板上的侧板，底板和侧板围合形成容纳腔。壳体51具有与容纳腔连通的开口，盖板53能够盖设于开口，以封闭容纳腔。正极极片、负极极片和隔离膜可经卷绕工艺或叠片工艺形成电极组件52。电极组件52封装于容纳腔内。电解液浸润于电极组件52中。电池单体5所含电极组件52的数量可以为一个或多个，本领域技术人员可根据实际需求进行选择。
二次电池可以为电池模块4或电池包1。
电池模块包括至少一个电池单体。电池模块所含电池单体的数量可以为一个或多个，本领域技术人员可根据电池模块的应用和容量选择合适的数量。
图3是作为一个示例的电池模块4。参照图3，在电池模块4中，多个电池单体5可以是沿电池模块4的长度方向依次排列设置。当然，也可以按照其他任意的方式进行排布。进一步可以通过紧固件将该多个电池单体5进行固定。
可选地，电池模块4还可以包括具有容纳空间的外壳，多个电池单体5容纳于该容纳空间。
在其中一些实施例中，上述电池模块还可以组装成电池包，电池包所含电池模块的数量可以为一个或多个，本领域技术人员可根据电池包的应用和容量选择合适的数量。
图4和图5是作为一个示例的电池包1。参照图4和图5，在电池包1中可以包括电池箱和设置于电池箱中的多个电池模块4。电池箱包括上箱体2和下箱体3，上箱体2能够盖设于下箱体3，并形成用于容纳电池模块4的封闭空间。多个电池模块4可以按照任意的方式排布于电池箱中。
另外，本申请还提供一种用电装置，用电装置包括本申请提供的二次电池。二次电池可以用作用电装置的电源，也可以用作用电装置的能量存储单元。用电装置可以包括移动设备、电动车辆、电气列车、船舶及卫星、储能系统等，但不限于此。其中，移动设备例如可以是手机、笔记本电脑等；电动车辆例如可以是纯电动车、混合动力电动车、插电式混合动力电动车、电动自行车、电动踏板车、电动高尔夫球车、电动卡车等，但不限于此。
作为用电装置，可以根据其使用需求来选择二次电池。
图6是作为一个示例的用电装置6。该用电装置为纯电动车、混合动力电动车、或插电式混合动力电动车等。为了满足该用电装置对二次电池的高功率和高能量密度的需求，可以采用电池包或电池模块。
作为另一个示例的装置可以是手机、平板电脑、笔记本电脑等。该装置通常要求轻薄化，可以采用二次电池作为电源。
以下为具体实施例。
以下，说明本申请的实施例。下面描述的实施例是示例性的，仅用于解释本申请，而不能理解为对本申请的限制。实施例中未注明技术或条件的，按照本领域内的文献所描述的技术或条件或者按照产品说明书进行。所用试剂或仪器未注明生产厂商者，均为可以通过市购获得的常规产品。
实施例1
1)正极极片的制备
将正极活性材料LiNi0.68Co0.10Mn0.22O2、导电剂炭黑(Super P)、粘结剂聚偏二氟乙烯(PVDF)按照质量比96.2:2.7:1.1在适量的溶剂N-甲基吡咯烷酮(NMP)中混合均匀，得到正极浆料；将正极浆料涂布于正极集流体铝箔上，通过烘干、冷压、分条、裁切等工序，形成厚度为38μm的正极活性材料层，得到正极极片。正极活性材料的Dv99为y1μm，Dv50为y2μm，具体值请参见表1。
2)负极极片的制备
将负极活性材料人造石墨、导电剂炭黑(Super P)、粘结剂丁苯橡胶(SBR)和羧甲基纤维素钠(CMC)按照质量比96.4:0.7:1.8:1.1在适量的溶剂去离子水中混合均匀，得到负极浆料；将负极浆料涂布于负极集流体铜箔上，通过烘干、冷压、分条、裁切工序，形成单面厚度为54μm的负极活性材料层，得到负极极片。负极极片的压实密度为1.45g/cm3。
3)隔离膜
选用12μm厚的聚丙烯隔离膜；隔离膜的Gurley值，具体值请参见表1。
4)电解液的制备
将碳酸乙烯酯(EC)、碳酸甲乙酯(EMC)按照质量30：70进行混合得到有机溶剂，将占电解液整体3wt％的LiFSI溶于混合溶剂中，将充分干燥的LiPF6溶解于上述有机溶剂中配制成LiPF6浓度为1mol/L的电解液。
5)二次电池的制备
将正极极片、隔离膜、负极极片按顺序堆叠并卷绕，得到电极组件；将电极组件置于外包装中，干燥后注入电解液，经过真空封装、静置、化成、整形等工序，得到二次电池；电解液的质量与二次电池的容量的比值为2.2g/Ah。一些具体参数请参见表1。
实施例2～6
实施例2～6的二次电池与实施例1的二次电池制备方法相似，区别在于，电解液中LiFSI的质量含量a不同，具体区别请参见表1。
实施例7～15
实施例7～15的二次电池与实施例1的二次电池制备方法相似，区别在于，正极活性材料LiNi0.68Co0.10Mn0.22O2的Dv99(即y1)不同和/或正极活性材料LiNi0.68Co0.10Mn0.22O2的Dv50不同，具体区别请参见表1。
实施例16～19
实施例16～19的二次电池与实施例1的二次电池制备方法相似，区别在于，正极活性材料NCM三元材料中镍元素的摩尔占比及钴元素的摩尔占比不同。
实施例20～22
实施例20～22的二次电池与实施例1的二次电池制备方法相似，区别在于，隔离膜的Gurley值不同，具体区别请参见表1。
对比例1～2
对比例1～2的二次电池与实施例1的二次电池制备方法相似，区别在于，电解液中LiFSI的质量含量a和正极活性材料LiNi0.68Co0.10Mn0.22O2的Dv99(即y1)不同且y1/a的值不同，具体区别请参见表1。具体区别请参见表1。
表1
上文对各个实施例的描述倾向于强调各个实施例之间的不同之处，其相同或相似之处可以相互参考，为了简洁，本文不再赘述。
以下为性能测试。
(1)快充能力测试：将上述各实施例和对比例的电池以1C(即1h内完全放掉理论容量的电流值)的电流进行第一次充电和放电，具体包括：在35℃下，将电池以1C倍率恒流充电至电压4.4V，之后恒压充电至电流≤0.05C，静置5min，再以0.33C倍率恒流放电至电压2.8V，记录其实际容量为C0。然后将每个电池依次以1.0C0、1.3C0、1.5C0、1.8C0、2.0C0、2.3C0、2.5C0、3.0C0、3.5C0、4C0、4.5C0、5C0恒流充电至全电池充电截止电压4.4V或者0V负极截止电位(以先达到者为准)，每次充电完成后需以1C0放电至全电池放电截止电压2.8V，记录不同充电倍率下充电至10％、20％、30％、……、80％SOC(State of Charge，荷电状态，当“SOC＝0”时表示电池放电完全，当“SOC＝100％”时表示电池完全充满)时所对应的负极电位，绘制出不同SOC态下的充电倍率-负极电位曲线，线性拟合后得出不同SOC态下负极电位为0V时所对应的充电倍率，该充电倍率即为该SOC态下的充电窗口，分别记为C(10％SOC)、C(20％SOC)、C(30％SOC)、C(40％SOC)、C(50％SOC)、C(60％SOC)、C(70％SOC)、C(80％SOC)，根据公式(60/C(20％SOC)+60/C(30％SOC)+60/C(40％SOC)+60/C(50％SOC)+60/C(60％SOC)+60/C(70％SOC)+60/(C80％SOC))×10％计算得到该电池从10％SOC充电至80％SOC的充电时间T，单位为min。该时间越短，则电池的快速充电性能越优秀。
(2)快充循环寿命：以快充能力测试得出的各SOC下的充电倍率进行分步充电，以C(10％SOC)的充电倍率恒流充电至10％SOC，再以C(20％SOC)的充电倍率恒流充电至20％SOC，再以C(30％SOC)的充电倍率恒流充电至30％SOC，再以C(40％SOC)的充电倍率恒流充电至40％SOC，再以C(50％SOC)的充电倍率恒流充电至50％SOC，再以C(60％SOC)的充电倍率恒流充电至60％SOC，再以C(70％SOC)的充电倍率恒流充电至70％SOC，再以C(80％SOC)的充电倍率恒流充电至80％SOC，再以0.33C的充电倍率恒流充电至100％SOC，再以0.33C的倍率放电至2.5V，按照上述流程循环，记录衰减至80％SOH时的循环圈数。
其中，衰减至80％SOH时的循环圈数通过如下方法计算：由小到大将第n圈的放电容量除以第一圈的放电容量，分别记录比值；当该比值首次出现等于或小于80％SOH时，此循环圈数即为衰减至80％SOH时的循环圈数，即表2中的快充循环寿命参数。
该循环圈数越大，说明其快充循环寿命越优秀。
(3)快充温升测试:采用快充循环寿命测试一样的充放电流程充放电1个cycle，用感温线测试并记录此过程中电芯大面的温升(即充放电前后的温度差异)。
(4)热箱安全测试：电芯先满充至对应的设计上限电压，电芯带夹具，热箱内部从常温开始升温，按照2℃/min升温，升温至100℃，保持1小时，再以5℃/min升温，每5℃保持30min，直至电芯失效(开阀冒烟或起火)，停止测试，上限温度设置为250℃，记录电芯失效时的热箱内的温度。该热箱内的温度即可代表热箱安全性能，具体数值见表2中的热箱安全性能(℃)。
测试结果如表2所示。
表2
表2中的快充时间可以表征二次电池的快充性能。快充时间越短，则电池的快充性能越优秀。快充循环寿命(80％SOH的循环圈数)可表征电池的循环寿命，快充循环寿命(80％SOH的循环圈数)越大，说明其快充循环寿命越优秀。
表2中的快充温升及热箱安全测试可以表征快充电过程中的温升过快带来的热量失控情况。快充温升越小，说明其快充电过程中的温升过快带来的热量失控风险越小，温升性能越好；热箱安全测试电芯失效时的炉温越高，说明其快充电过程中的温升过快带来的热量失控风险越小，热箱安全性能越好。
结合表1～表2可知，对比例1～2的二次电池与实施例1的二次电池制备方法相似，区别在于，电解液中LiFSI的质量含量a和正极活性材料的Dv99(即y1)中的至少一个不同，对比例1的正极活性材料的Dv99较大，且y1/a较大，其二次电池的快充时间T较大，循环寿命较小，温升较大，说明电池的快充性能较差，循环寿命较差，温升较大；对比例2中a较大，y1/a较小，二次电池的循环寿命恶化，电芯失效时的炉温较低，热箱安全性能较差。
各实施例相比于对比例，能够兼顾二次电池具有较好的快充循环寿命。
通过实施例1～10可知，控制200≤y1/a≤5000可以进一步提升电池的快充性能和循环寿命，同时具有较低的温升和较好的热箱安全性能，控制200≤y1/a≤600，可进一步提升二次电池的综合性能。
实施例7～9的二次电池与实施例1区别在于，正极活性材料的Dv99(即y1)不同，均具有良好综合性能。进一步地，控制正极活性材料的Dv99在5～12μm，二次电池具有更好的快充性能，具有更低的温升。
实施例12～15的二次电池与实施例1区别在于，正极活性材料Dv50(即y2)不同，y1/y2相应也不同，均具有良好的综合性能。进一步地，y2在2～5，y1/y2在2～6的范围内，二次电池具有更优的快充性能、循环寿命，同时具有较低的温升和较优的安全性能。
实施例16～19的二次电池与实施例1区别在于，正极活性材料的镍含量和钴含量不同，当进一步的，钴元素的摩尔占比为9％～15％，镍元素的摩尔占比为50％～70％时，二次电池具有更优的循环寿命和较优的热箱安全性能。
实施例20～22的二次电池与实施例1区别在于，隔离膜的Gurley值不同，均具有良好的快充性能和降低快充电过程中的温升过快带来的热量失控风险的效果。进一步地，隔离膜的Gurley值在400～600s的范围内，二次电池具有更优的循环寿命和较优的热箱安全性能。
需要说明的是，本申请不限定于上述实施方式。上述实施方式仅为示例，在本申请的技术方案范围内具有与技术思想实质相同的构成、发挥相同作用效果的实施方式均包含在本申请的技术范围内。此外，在不脱离本申请主旨的范围内，对实施方式施加本领域技术人员能够想到的各种变形、将实施方式中的一部分构成要素加以组合而构筑的其它方式也包含在本申请的范围内。

Claims (16)

  1. 一种二次电池，其包括正极极片、负极极片及设于所述正极极片与所述负极极片之间的电解液；所述电解液包括质量含量为a的LiFSI；所述正极极片含有正极活性材料，所述正极活性材料的Dv99为y1μm，y1为5～15；所述二次电池满足如下条件：100≤y1/a≤10000。
  2. 如权利要求1所述的二次电池，其中，所述二次电池满足如下条件中的至少一个：
    (1)y1为5～12；
    (2)0＜a≤10％；
    (3)200≤y1/a≤5000。
  3. 如权利要求1至2任一项所述的二次电池，其中，y1为5～10。
  4. 如权利要求1至3任一项所述的二次电池，其中，0.01％≤a≤10％。
  5. 如权利要求1至4任一项所述的二次电池，其中，0.1％≤a≤5％。
  6. 如权利要求1至5任一项所述的二次电池，其中，所述二次电池满足如下条件中的至少一个：
    (1)1％≤a≤5％；
    (2)200≤y1/a≤600。
  7. 如权利要求6所述的二次电池，其中，2％≤a≤4％。
  8. 如权利要求1至7任一项所述的二次电池，其中，所述正极活性材料的Dv50为y2μm，所述二次电池满足如下条件：1.2≤y1/y2≤7。
  9. 如权利要求8所述的二次电池，其中，所述二次电池满足如下条件中的至少一个：
    (1)y2为1.5～6；
    (2)2≤y1/y2≤6。
  10. 如权利要求9所述的二次电池，其中，y2为2～5。
  11. 如权利要求1至10任一项所述的二次电池，其中，所述正极活性材料包括镍钴锰三元正极材料。
  12. 如权利要求11所述的二次电池，其中，在所述镍钴锰三元正极材料的镍元素、钴元素和锰元素摩尔总量中，钴元素的摩尔占比为5％～15％，镍元素的摩尔占比为50％～90％。
  13. 如权利要求12所述的二次电池，其中，在所述镍钴锰三元正极材料的镍元素、钴元素和锰元素摩尔总量中，钴元素的摩尔占比为9％～15％，镍元素的摩尔占比为50％～70％。
  14. 如权利要求1至13任一项所述的二次电池，其中，所述二次电池还包括设于所述正极极片与所述负极极片之间的隔离膜，所述隔离膜的Gurley值为100s～600s。
  15. 如权利要求14所述的二次电池，其中，所述隔离膜的Gurley值为400s～500s。
  16. 一种用电装置，其包括权利要求1至15任一项所述的二次电池。
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