WO2024087842A1 - 二次电池及用电设备 - Google Patents

二次电池及用电设备 Download PDF

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Publication number
WO2024087842A1
WO2024087842A1 PCT/CN2023/114853 CN2023114853W WO2024087842A1 WO 2024087842 A1 WO2024087842 A1 WO 2024087842A1 CN 2023114853 W CN2023114853 W CN 2023114853W WO 2024087842 A1 WO2024087842 A1 WO 2024087842A1
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Prior art keywords
active material
material layer
positive electrode
lithium oxide
manganese
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PCT/CN2023/114853
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English (en)
French (fr)
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刘雯
曾城
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欣旺达动力科技股份有限公司
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Publication of WO2024087842A1 publication Critical patent/WO2024087842A1/zh

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    • 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
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/136—Electrodes based on inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy
    • 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
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/5825—Oxygenated metallic salts or polyanionic structures, e.g. borates, phosphates, silicates, olivines
    • 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
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/028—Positive electrodes
    • 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 battery technology, and in particular to a secondary battery and an electrical device.
  • Lithium manganese iron phosphate (LiMn x Fe 1-x PO 4 ) is doped with a certain proportion of manganese on the basis of lithium iron phosphate. Without changing the original olivine structure, it inherits the advantages of lithium iron phosphate such as low cost, high thermal stability and high safety, and also gives play to the advantages of manganese elements, thereby improving the safety and stability of the positive electrode material, expanding the voltage window, and increasing the theoretical energy density.
  • a first aspect of the present application provides a secondary battery, comprising a positive electrode plate, the positive electrode plate comprising a positive electrode collector and a positive electrode active material layer arranged on at least one surface of the positive electrode collector; the positive electrode active material layer comprises a first active material layer and a second active material layer, the first active material layer is arranged between the positive electrode collector and the second active material layer; the first active material layer comprises a first manganese iron lithium oxide, and the second active material layer comprises a second manganese iron lithium oxide; wherein, based on the total molar amount of metal elements other than lithium, the molar percentage of manganese in the first manganese iron lithium oxide is n1%, and the molar percentage of manganese in the second manganese iron lithium oxide is n2%, satisfying n1>n2.
  • n2 ⁇ 20 n2 ⁇ 20.
  • the average particle size of the first manganese iron lithium oxide is D1
  • the average particle size of the second manganese iron lithium oxide is D2, satisfying D1>D2.
  • the mass percentage of the first manganese iron lithium oxide in the first active material layer is ⁇ 80%.
  • the general formula of the first manganese iron lithium oxide includes Li a Mn x Fe 1-x PO 4 , wherein 0.6 ⁇ x ⁇ 0.8, 0.95 ⁇ a ⁇ 1.2; and/or the general formula of the second manganese iron lithium oxide includes Li b Mn y Fe 1-y PO 4 , wherein 0 ⁇ y ⁇ 0.2, 0.95 ⁇ b ⁇ 1.2.
  • a second aspect of the present application provides an electrical device, comprising the secondary battery as described above.
  • the embodiments of the present application provide a secondary battery, a method for preparing a secondary battery, and an electrical device having the secondary battery.
  • the secondary battery is formed by stacking a first active material layer and a second active material layer on a positive current collector of a positive electrode plate.
  • the first active material layer and the second active material layer constitute the positive active material layer of the positive electrode plate, and the manganese content in the first manganese iron lithium oxide in the first active material layer is higher than the manganese content in the first manganese iron lithium oxide in the second active material layer.
  • the second active material layer with a low manganese content is coated on the first active material layer.
  • the first active material layer and the second active material layer both contain manganese iron lithium oxide, which reduces the grain boundary impedance between different materials and enhances the interlayer bonding force between the first active material layer and the second active material layer.
  • the manganese-poor interface of the second active material layer can reduce the manganese content in contact with the electrolyte, thereby reducing the dissolution of manganese.
  • the electrical equipment includes but is not limited to electric toys, electric tools, battery vehicles, electric vehicles, energy storage equipment, ships, spacecraft, etc.
  • a secondary battery in one embodiment of the present application, includes a positive electrode plate, a negative electrode plate, a separator, an electrolyte, and a casing.
  • 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.
  • the positive electrode active material layer includes a first active material layer and a second active material layer, wherein the first active material layer is disposed between the positive electrode current collector and the second active material layer.
  • the first active material layer includes a first manganese iron lithium oxide, wherein the molar percentage of manganese in the first manganese iron lithium oxide is n1% based on the total molar amount of metal elements other than lithium; the second active material layer includes The second manganese iron lithium oxide has a molar percentage of manganese element of n2% based on the total molar amount of metal elements except lithium, and satisfies n1>n2.
  • the molar percentage of manganese in the first manganese iron lithium oxide is n1%, it is higher than the molar percentage of manganese in the second manganese iron lithium oxide, which is n2%. That is, the manganese ratio (manganese content) in the first active material layer (equivalent to the inner layer) close to the positive electrode current collector is higher, and the manganese ratio (manganese content) in the second active material layer (equivalent to the outer layer) far away from the positive electrode current collector is lower, forming a positive electrode sheet with a double-layer composite structure of high manganese in the inner layer and low manganese in the outer layer.
  • the low manganese manganese iron lithium oxide used in the outer layer can reduce the manganese content in contact with the electrolyte, thereby reducing the dissolution of manganese.
  • the manganese iron lithium oxides in the first active material layer and the second active material layer are both olivine structures, which reduces the grain boundary impedance between different materials and the material bonding is better.
  • n1-n2 includes 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80 or a range consisting of any of the above values.
  • n1 ⁇ 50 specifically, n1 includes 50, 55, 60, 65, 70, 75, 80, 90, 95, 99 or a range consisting of any of the above values.
  • 60 ⁇ n1 ⁇ 70 Preferably, 60 ⁇ n1 ⁇ 70.
  • 0 ⁇ n2 ⁇ 20 specifically, n1 includes 1, 5, 10, 15, 20 or a range consisting of any of the above values.
  • manganese iron lithium oxide has a higher bulk electronic conductivity and lithium ion diffusion rate, which can further reduce manganese dissolution, accelerate the conduction efficiency of lithium ions, and improve the rate and cycle stability of the battery system.
  • the general formula of the first manganese iron lithium oxide includes Li a Mn x Fe 1-x PO 4 , wherein 0.6 ⁇ x ⁇ 0.8, 0.95 ⁇ a ⁇ 1.2, specifically, x includes any one of 0.6, 0.65, 0.7, 0.75 , and 0.8, then the general formula of the first manganese iron lithium oxide includes any one of LiMn 0.6 Fe 0.4 PO 4 , LiMn 0.65 Fe 0.35 PO 4 , LiMn 0.7 Fe 0.3 PO 4 , LiMn 0.75 Fe 0.25 PO 4 , and LiMn 0.8 Fe 0.2 PO 4 .
  • the general formula of the second manganese iron lithium oxide includes LiMn y Fe 1-y PO 4 , wherein 0 ⁇ y ⁇ 0.2, 0.95 ⁇ b ⁇ 1.2, specifically, y includes any one of 0.1, 0.13, 0.15 , 0.18 , and 0.2, and the general formula of the first manganese iron lithium oxide includes any one of LiMn 0.1 Fe 0.9 PO 4 , LiMn 0.13 Fe 0.87 PO 4 , LiMn 0.15 Fe 0.85 PO 4 , LiMn 0.18 Fe 0.82 PO 4 , and LiMn 0.2 Fe 0.8 PO 4 .
  • the mass percentage of the first manganese iron lithium oxide in the first active material layer is ⁇ 80%, and the mass percentage of the second manganese iron lithium oxide in the second active material layer is ⁇ 20%.
  • the mass percentage of the first manganese iron lithium oxide is 85%, then the mass percentage of the second manganese iron lithium oxide is 15%; if the mass percentage of the first manganese iron lithium oxide is 90%, then the mass percentage of the second manganese iron lithium oxide is 10%; if the mass percentage of the first manganese iron lithium oxide is 83%, then the mass percentage of the second manganese iron lithium oxide is 10%.
  • the mass percentage of the second manganese iron lithium oxide is 17%; the mass percentage of the first manganese iron lithium oxide is 88%, and the mass percentage of the second manganese iron lithium oxide is 12%.
  • Adjusting the ratio of the first manganese iron lithium oxide content in the first active material layer and the second manganese iron lithium oxide content in the second active material layer can achieve the optimal ratio within a certain range, ensuring that the dissolution of manganese is reduced without losing the voltage range, and realizing the stable cycle of the secondary battery.
  • the mass percentage of the first manganese iron lithium oxide in the first active material layer is controlled to be greater than the mass percentage of the second manganese iron lithium oxide in the second active material layer, so that the mass percentage of the first manganese iron lithium oxide is ⁇ 80%, and the second active material layer is used as a relatively thin protective layer, and the mass percentage of the second manganese iron lithium oxide is ⁇ 20%, which can ensure that sufficient manganese plays a role in stabilizing the electrode, improve the cycle stability of the positive electrode active material, expand the voltage range of the secondary battery, and achieve high energy density.
  • the ratio of the first manganese iron lithium oxide to the second manganese iron lithium oxide can be adjusted by parameters such as surface density and thickness.
  • the average particle size of the first manganese iron lithium oxide is D1
  • the average particle size of the second manganese iron lithium oxide is D2, satisfying D1>D2.
  • the second manganese iron lithium oxide exists in a granular form with a particle size of 200nm to 500nm, specifically, it can be 200, 250, 300, 350, 400, 450, 500 or a range consisting of any two numbers therein.
  • the first manganese iron lithium oxide exists in a granular form with a particle size of 500 to 900nm, specifically, it can be 500, 550, 600, 650, 700, 750, 800, 850, 900 or a range consisting of any two numbers therein.
  • the small particle size of the second manganese iron lithium oxide in the second active material layer can help to increase the compaction density and form a compact manganese iron lithium oxide outer layer.
  • Manganese iron lithium oxide particles with different particle sizes at the interface between the first active material layer and the second active material layer can help to combine more closely.
  • the positive electrode active material layer further includes a positive electrode conductor and a positive electrode binder.
  • positive electrode conductive agent there is no limitation on the type of positive electrode conductive agent, and any known conductive agent can be used.
  • positive electrode conductive agents may include, but are not limited to, graphite such as natural graphite and artificial graphite; carbon black such as acetylene black; carbon materials such as amorphous carbon such as needle coke; carbon nanotubes; graphene, etc.
  • the above positive electrode conductive agents may be used alone or in any combination.
  • positive electrode binder used in the manufacture of the positive electrode active material layer.
  • positive electrode binders may include, but are not limited to, one or more of the following: resin polymers such as polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, polyimide, aromatic polyamide, cellulose, and nitrocellulose; rubber polymers such as styrene-butadiene rubber (SBR), nitrile rubber (NBR), fluororubber, isoprene rubber, polybutadiene rubber, and ethylene-propylene rubber; Thermoplastic elastomer polymers such as styrene-butadiene-styrene block copolymers or their hydrides, ethylene-propylene-diene terpolymers (EPDM), styrene-ethylene-
  • resin polymers such as polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, polyimide, aromatic polyamide, cellulose, and
  • positive electrode current collector which can be any known material suitable for use as a positive electrode current collector.
  • positive electrode current collectors may include, but are not limited to, metal materials such as aluminum, stainless steel, nickel plating, titanium, tantalum, etc.; carbon materials such as carbon cloth and carbon paper; composite materials formed by polymers and metal layers.
  • the positive electrode current collector is a metal material.
  • the positive electrode current collector is aluminum.
  • the form of the positive electrode current collector is a metal material
  • the form of the positive electrode current collector may include, but is not limited to, metal foil, metal cylinder, metal strip roll, metal plate, metal foil, metal plate mesh, stamped metal, foamed metal, etc.
  • the positive electrode current collector is a carbon material
  • the form of the positive electrode current collector may include, but is not limited to, carbon plate, carbon film, carbon cylinder, etc.
  • the positive electrode current collector is a metal foil.
  • the metal foil is mesh-shaped.
  • the thickness of the metal foil is greater than 1 ⁇ m, greater than 3 ⁇ m, or greater than 5 ⁇ m.
  • the thickness of the metal foil is less than 1 mm, less than 100 ⁇ m, or less than 50 ⁇ m.
  • the thickness of the metal foil is within the range composed of any two of the above values.
  • the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector, wherein the negative electrode active material layer contains a negative electrode active material, and the negative electrode active material contains graphite.
  • the negative electrode sheet is a single-sided sheet or a double-sided sheet.
  • the negative electrode active material layer is arranged on one surface of the negative electrode current collector.
  • the negative electrode active material layer is arranged on both surfaces of the negative electrode current collector.
  • the negative electrode sheet may also have a single-sided negative electrode sheet area and a double-sided negative electrode sheet area at the same time.
  • the negative electrode current collector includes, but is not limited to, metal foil, metal cylinder, metal strip, metal plate, metal film, metal mesh, stamped metal, foamed metal, etc.
  • the negative electrode current collector is metal foil.
  • the negative electrode current collector is aluminum foil or copper foil. As used herein, the term "copper foil" includes copper alloy foil.
  • the negative electrode current collector is a conductive resin.
  • the conductive resin The grease includes a film obtained by evaporating copper on a polypropylene film.
  • the negative electrode active material layer may be one or more layers, and each layer of the multiple negative electrode active material layers may contain the same or different negative electrode active materials.
  • the negative electrode active material is any substance that can reversibly intercalate and deintercalate metal ions such as lithium ions.
  • the chargeable capacity of the negative electrode active material is greater than the discharge capacity of the positive electrode active material to prevent lithium metal from being precipitated on the negative electrode sheet during charging.
  • the thickness of the negative electrode active material layer refers to the thickness of the negative electrode active material layer coated on a single side of the negative electrode current collector. In some embodiments, the thickness of the single-sided negative electrode active material layer is 15 ⁇ m or more. In some embodiments, the thickness of the single-sided negative electrode active material layer is 20 ⁇ m or more. In some embodiments, the thickness of the single-sided negative electrode active material layer is 30 ⁇ m or more. In some embodiments, the thickness of the single-sided negative electrode active material layer is 150 ⁇ m or less. In some embodiments, the thickness of the single-sided negative electrode active material layer is 120 ⁇ m or less. In some embodiments, the thickness of the single-sided negative electrode active material layer is 100 ⁇ m or less.
  • the thickness of the negative electrode active material layer is within the range consisting of any two of the above values.
  • the electrolyte can penetrate into the vicinity of the interface of the negative electrode current collector, thereby improving the charge and discharge characteristics of the secondary battery at high current density; at the same time, the volume ratio of the negative electrode current collector to the negative electrode active material is within an appropriate range, which can ensure the capacity of the secondary battery.
  • the negative electrode active material layer includes a negative electrode active material, a negative electrode conductor, and a negative electrode binder.
  • the negative electrode active material can be selected from one or more of graphite, soft carbon, hard carbon, carbon fiber, silicon-based materials, and tin-based materials, and graphite is more preferred.
  • the conductive agent includes one or more of carbon black, graphite, carbon fiber, carbon nanotube or graphene, preferably carbon black.
  • the binder can improve the bonding between the negative electrode active materials.
  • the type of the binder is not particularly limited, as long as it is a material that is stable to the electrolyte or the solvent used in the electrode manufacturing.
  • the binder includes sodium carboxymethyl cellulose and styrene-butadiene rubber.
  • the negative electrode active material graphite, conductive agent CNT, thickener CMC, and binder SBR were mixed in a mass ratio of 96.5:0.8:0.9:1.8, and the solvent deionized water was added and vacuum stirred until the system was uniform to obtain the negative electrode slurry, which was then evenly coated on the upper and lower surfaces of the negative electrode current collector copper foil. After drying at room temperature, it was transferred to an oven for further drying to compact the density.
  • the negative electrode sheet was obtained after cold pressing and slitting under the condition of 1.7g/ cm3 .
  • the electrolyte comprises a lithium salt and a solvent. In some embodiments, the electrolyte further comprises an additive.
  • the lithium salt includes at least one of lithium hexafluorophosphate, organic lithium borate, lithium perchlorate, and sulfonyl imide lithium salts.
  • the content of the lithium salt is not particularly limited as long as it does not impair the effects of the present application.
  • the electrolyte further comprises any non-aqueous solvent known in the prior art that can be used as a solvent for the electrolyte.
  • the non-aqueous solvent includes, but is not limited to, one or more of the following: cyclic carbonates and linear carbonates.
  • examples of the cyclic carbonate may include, but are not limited to, one or more of the following: ethylene carbonate (EC), propylene carbonate (PC) and butylene carbonate.
  • the cyclic carbonate has 3-6 carbon atoms.
  • examples of the linear carbonates may include, but are not limited to, one or more of the following: dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate (DEC), methyl n-propyl carbonate, ethyl n-propyl carbonate, di-n-propyl carbonate, etc.
  • fluorine-substituted linear carbonates may include, but are not limited to, one or more of the following: bis(fluoromethyl) carbonate, bis(difluoromethyl) carbonate, bis(trifluoromethyl) carbonate, bis(2-fluoroethyl) carbonate, bis(2,2-difluoroethyl) carbonate, bis(2,2,2-trifluoroethyl) carbonate, 2-fluoroethyl methyl carbonate, 2,2-difluoroethyl methyl carbonate, and 2,2,2-trifluoroethyl methyl carbonate, etc.
  • examples of the additive may include, but are not limited to, one or more of the following: fluorocarbonate, ethylene carbonate containing a carbon-carbon double bond, a compound containing a sulfur-oxygen double bond, and an acid anhydride.
  • a diaphragm is usually provided between the positive electrode and the negative electrode.
  • the electrolyte of the present application is usually infiltrated into the diaphragm for use.
  • the diaphragm material can be any common diaphragm material, such as polyethylene, polypropylene, polyvinylidene fluoride and a diaphragm composed of a variety of composite films. More preferably, a polypropylene film is used.
  • a method for preparing a secondary battery comprises the following steps:
  • the first lithium manganese iron phosphate, the conductive agent and the binder are added into a stirring tank filled with N-methylpyrrolidone (NMP) to prepare a slurry A with uniform mixing and stable viscosity;
  • NMP N-methylpyrrolidone
  • the second lithium manganese iron phosphate, the conductive agent and the binder are added into a stirring tank filled with NMP to prepare a slurry C with uniform mixing and stable viscosity;
  • Slurry A is coated on one side of an aluminum foil used as a positive electrode current collector and dried, and then slurry A of corresponding thickness and mass is coated on the other surface of the aluminum foil and dried to obtain aluminum foil layers coated with slurry on both sides, and rolled until the thickness of both sides is 0.12 mm, respectively, to form first active material layers on both surfaces of the positive electrode current collector;
  • coating C is coated on the first active material layer, both sides need to be coated, dried, and then rolled until the single-side coating thickness of the positive electrode collector is about 0.14 mm. After slitting and cutting, the positive electrode sheet is obtained.
  • the prepared positive electrode sheet, negative electrode sheet and separator are wound or stacked to make battery cells, and then the corresponding secondary batteries are made after processes such as liquid injection, formation, and capacity division.
  • NMP N-methylpyrrolidone solution
  • Slurry A is coated on one side of an aluminum foil and dried. After drying, slurry A is coated on the other surface of the aluminum foil and dried to obtain a first active material layer with slurry A coated on both sides, and the two sides are rolled to 0.12 mm respectively; slurry C is then coated on the first active material layer, both sides need to be coated, dried, and then rolled to a coating thickness of about 0.14 mm on a single surface of the positive electrode collector to form a second active material layer, and the positive electrode sheet is obtained after slitting and cutting; wherein the mass ratio of LiMn 0.6 Fe 0.4 PO 4 to LiMn 0.1 Fe 0.9 PO 4 in the positive electrode sheet is 9:1;
  • the negative electrode active material graphite, conductive agent CNT, thickener CMC, and binder SBR are mixed in a mass ratio of 96.5:0.8:0.9:1.8, and deionized water is added as a solvent.
  • the mixture is vacuum stirred until the system is uniform to obtain a negative electrode slurry, which is then evenly coated on the upper and lower surfaces of the negative electrode current collector copper foil. After drying at room temperature, the mixture is transferred to an oven for further drying, and the negative electrode sheet is obtained after cold pressing, slitting, and cutting at a compaction density of 1.7 g/ cm3 .
  • Ethylene carbonate (EC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC) are mixed in a volume ratio of 1:1:1 to obtain an organic solvent, and then fully dried lithium salt LiPF6 is dissolved in the mixed organic solvent to prepare an electrolyte with a concentration of 1 mol/L.
  • a polyethylene film is selected as the separating film.
  • the positive electrode sheet, the separator, and the negative electrode sheet are stacked in order, so that the separator is between the positive and negative electrode sheets to play an isolating role, and then wound to obtain a bare battery cell; the bare battery cell is placed in an outer packaging shell, and after drying, the electrolyte is injected, and after vacuum packaging, standing, forming, shaping and other processes, a lithium-ion battery is obtained.
  • the present embodiment differs from the embodiment 1 in that LiMn 0.7 Fe 0.3 PO 4 is used instead of LiMn 0.6 Fe 0.4 PO 4 .
  • the difference between this embodiment and embodiment 1 is that the average particle size of LiMn 0.6 Fe 0.4 PO 4 is 500 nm, and the average particle size of LiMn 0.1 Fe 0.9 PO 4 is 300 nm.
  • the difference between this embodiment and embodiment 1 is that the average particle size of LiMn 0.6 Fe 0.4 PO 4 is 900 nm, and the average particle size of LiMn 0.1 Fe 0.9 PO 4 is 500 nm.
  • the difference between this embodiment and embodiment 1 is that the average particle size of LiMn 0.6 Fe 0.4 PO 4 is 400 nm, and the average particle size of LiMn 0.1 Fe 0.9 PO 4 is 600 nm.
  • the difference between this embodiment and embodiment 1 is that the average particle size of LiMn 0.6 Fe 0.4 PO 4 is 600 nm, and the average particle size of LiMn 0.1 Fe 0.9 PO 4 is 200 nm.
  • the difference between this embodiment and embodiment 1 is that the average particle size of LiMn 0.6 Fe 0.4 PO 4 is 400 nm, and the average particle size of LiMn 0.1 Fe 0.9 PO 4 is 200 nm.
  • LiMn 0.6 Fe 0.4 PO 4 with an average particle size of 600 nm is mixed with a conductive agent acetylene black and a binder PVDF in a mass ratio of 88:4:8, and then added into a stirring tank filled with N-methylpyrrolidone solution (NMP) to prepare a slurry with uniform mixing and stable viscosity;
  • NMP N-methylpyrrolidone solution
  • Example 3 Stack the positive electrode sheet, the negative electrode sheet described in Example 1 and the isolation film in order, so that the isolation film is between the positive and negative electrode sheets to play an isolating role, and then wind to obtain a bare battery cell; place the bare battery cell in an outer packaging shell, inject the electrolyte described in Example 1 after drying, and obtain a lithium-ion battery through vacuum packaging, standing, forming, shaping and other processes.
  • Example 3 Stack the positive electrode sheet, the negative electrode sheet described in Example 1 and the isolation film in order, so that the isolation film is between the positive and negative electrode sheets to play an isolating role, and then wind to obtain a bare battery cell; place the bare battery cell in an outer packaging shell, inject the electrolyte described in Example 1 after drying, and obtain a lithium-ion battery through vacuum packaging, standing, forming, shaping and other processes.
  • the instrument used is an optical spectrum analyzer (ICP), and the specific test steps are as follows:
  • the lithium-ion batteries prepared in Examples 1-19 and Comparative Examples 1-2 were subjected to charge and discharge tests using a charge and discharge test system at 25 ⁇ 0.5°C.
  • the charge and discharge conditions were: charge termination voltage 4.3V; discharge termination voltage 2.8V; charge and discharge current density: 0.1C.
  • the lithium ion batteries prepared in Examples 1-19 and Comparative Examples 1-2 were subjected to charge and discharge tests using a charge and discharge test system at 25 ⁇ 0.5°C.
  • the charge and discharge conditions were as follows: charge termination voltage 4.3V; discharge termination voltage 2.8V; charge and discharge current density: 1C.
  • the cycle performance was the cycle performance of 200 cycles under 1C conditions. The results are shown in Table 1.
  • the negative electrode of the lithium-ion battery was disassembled and dissolved with a 0.1 mol/L HCl aqueous solution.
  • the amount of manganese ions in the HCl solution was tested by atomic absorption spectroscopy (AAS) to compare the cyclic manganese dissolution of the lithium-ion batteries in Examples 1-19 and Comparative Examples 1-2.
  • the embodiment of the present application uses the second active material layer with a lower manganese content as the protective outer layer and the first active material layer with a higher manganese content as the inner layer to form a positive electrode active material layer with a double-layer composite structure.
  • the first manganese iron lithium oxide in the first active material layer and the second manganese iron lithium oxide in the second active material layer both have excellent electrochemical properties, which can improve the cycle performance of the secondary battery.
  • the double-layer composite structure of the embodiment has the effect of effectively reducing manganese dissolution and also improves the electrochemical performance of the secondary battery.

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Abstract

一种二次电池及用电设备，二次电池包括正极极片，正极极片的正极集流体上层叠设置第一活性材料层和第二活性材料层，第一活性材料层中的第一锰铁锂氧化物中锰含量高于第二活性材料层中的第二锰铁锂氧化物中的锰含量。

Description

二次电池及用电设备
本申请要求于2022年10月26日提交中国专利局、申请号为202211320152.0、申请名称为“二次电池及用电设备”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
本申请涉及电池技术领域，具体涉及一种二次电池及用电设备。
背景技术
磷酸锰铁锂(LiMnxFe1-xPO4)在磷酸铁锂的基础上掺杂了一定比例的锰元素，在不改变原有橄榄石结构的基础上，继承了磷酸铁锂的低成本、高热稳定性、高安全性等优点，还发挥了锰元素的优势，提高了正极材料的安全性和稳定性，扩大了电压窗口，提高了理论能量密度。
技术解决方案
本申请的第一方面提供一种二次电池，包括正极极片，所述正极极片包括正极集流体和设置于所述正极集流体至少一个表面上的正极活性材料层；所述正极活性材料层包括第一活性材料层和第二活性材料层，所述第一活性材料层设置于所述正极集流体和所述第二活性材料层之间；所述第一活性材料层包括第一锰铁锂氧化物，所述第二活性材料层包括第二锰铁锂氧化物；其中，基于除锂之外金属元素的总摩尔量，所述第一锰铁锂氧化物中锰元素的摩尔百分含量为n1％，所述第二锰铁锂氧化物中锰元素的摩尔百分含量为n2％，满足n1>n2。
可选的，30≤n1-n2≤80。
可选的，50≤n1≤90。
可选的，n2≤20。
可选的，所述第一锰铁锂氧化物的平均粒径为D1，所述第二锰铁锂氧化物的平均粒径为D2，满足D1>D2。
可选的，500nm≤D1≤900nm。
可选的，200nm≤D2≤500nm。
可选的，以所述正极活性材料层中的第一锰铁锂氧化物和第二锰铁锂氧化物的总质量为100％计，所述第一活性材料层中的第一锰铁锂氧化物的质量百分比≥80％。
可选的，所述第一锰铁锂氧化物的通式包括LiaMnxFe1-xPO4，其中0.6≤x≤0.8，0.95≤a≤1.2；和/或，所述第二锰铁锂氧化物的通式包括LibMnyFe1-yPO4，其中0＜y≤0.2，0.95≤b≤1.2。
本申请的第二方面提供一种用电设备，包括如前所述的二次电池。
本申请的实施方式
下面将结合本申请实施例中的附图，对本申请实施例中的技术方案进行清楚、完整地描述，显然，所描述的实施例仅仅是本申请一部分实施例，而不是全部的实施例。基于本申请中的实施例，本领域技术人员在没有做出创造性劳动前提下所获得的所有其他实施例，都属于本申请保护的范围。此外，应当理解的是，此处所描述的具体实施方式仅用于说明和解释本申请，并不用于限制本申请。
本申请实施例提供一种二次电池、二次电池的制备方法及具有该二次电池的用电设备，所述二次电池通过在正极极片的正极集流体上层叠设置第一活性材料层和第二活性材料层，第一活性材料层与第二活性材料层构成正极极片的正极活性材料层，且第一活性材料层中的第一锰铁锂氧化物中锰含量高于第二活性材料层中的第一锰铁锂氧化物中的锰含量，将低锰含量的第二活性材料层涂敷在第一活性材料层上，第一活性材料层和第二活性材料层均包含锰铁锂氧化物，减少了不同材料之间的晶界阻抗，增强了第一活性材料层和第二活性材料层的层间结合力，第二活性材料层的贫锰界面可以降低与电解液接触的锰含量，起到减少锰溶出的作用，组装成二次电池能够获得能量密度高、安全性能好、循环寿命长、性价比高的二次电池。
所述用电设备包括但不限于电动玩具、电动工具、电瓶车、电动汽车、储能设备、轮船、航天器等。
本申请一实施例中，提供一种二次电池，所述二次电池包括正极极片、负极极片、隔膜、电解液、以及外壳。
I、正极极片
正极极片包括正极集流体和设置于正极集流体至少一个表面上的正极活性材料层。
正极活性材料层
正极活性材料层包括第一活性材料层和第二活性材料层，所述第一活性材料层设置于所述正极集流体和所述第二活性材料层之间。
在一些实施例中，第一活性材料层包括第一锰铁锂氧化物，基于除锂之外金属元素的总摩尔量，所述第一锰铁锂氧化物中锰元素的摩尔百分含量为n1％；第二活性材料层包括 第二锰铁锂氧化物，基于除锂之外金属元素的总摩尔量，第二锰铁锂氧化物中锰元素的摩尔百分含量为n2％，并满足n1>n2。
由于第一锰铁锂氧化物中的锰的摩尔百分含量n1％，高于第二锰铁锂氧化物中的锰的摩尔百分含量n2％。即靠近正极集流体的第一活性材料层(相当于内层)中的锰比例(锰含量)较高，远离正极集流体的第二活性材料层(相当于外层)中的锰比例(锰含量)较低，，形成内层高锰，外层低锰的双层复合结构的正极极片。外层采用的低锰的锰铁锂氧化物可降低与电解液接触的锰含量，从而起到减少锰溶出的作用。此外，第一活性材料层和第二活性材料层中的锰铁锂氧化物均为橄榄石结构，减少了不同材料之间的晶界阻抗，材料结合处比较好。
在一些实施例中，30≤n1-n2≤80，具体地，n1-n2的值包括30、35、40、45、50、55、60、65、70、75、80或由上述任意数值所组成的范围。
在一些实施例中，n1≥50，具体地，n1包括50、55、60、65、70、75、80、90、95、99或由上述任意数值所组成的范围。优选地，60≤n1≤70。由此，可提高正极活性材料的电压平台，进而提高电池的能量密度。
在一些实施例中，0＜n2≤20，具体地，n1包括1、5、10、15、20或由上述任意数值所组成的范围。当0＜n2≤20，锰铁锂氧化物具有较高的体相电子电导率和锂离子扩散速率，可进一步降低锰溶出，并加快锂离子的传导效率，提高电池体系的倍率和循环稳定性。
在一些实施例中，第一锰铁锂氧化物的通式包括LiaMnxFe1-xPO4，其中0.6≤x≤0.8，0.95≤a≤1.2，具体地，x包括0.6、0.65、0.7、0.75、0.8中的任意一者，则第一锰铁锂氧化物的通式包括LiMn0.6Fe0.4PO4、LiMn0.65Fe0.35PO4、LiMn0.7Fe0.3PO4、LiMn0.75Fe0.25PO4、LiMn0.8Fe0.2PO4中的任意一者。
在一些实施例中，所述第二锰铁锂氧化物的通式包括LiMnyFe1-yPO4，其中0＜y≤0.2，0.95≤b≤1.2，具体地，y包括0.1、0.13、0.15、0.18、0.2中的任意一者，则第一锰铁锂氧化物的通式包括LiMn0.1Fe0.9PO4、LiMn0.13Fe0.87PO4、LiMn0.15Fe0.85PO4、LiMn0.18Fe0.82PO4、LiMn0.2Fe0.8PO4中的任意一者。
在一些实施例中，以正极活性材料层中的第一锰铁锂氧化物和第二锰铁锂氧化物的总质量为100％计，第一活性材料层中的第一锰铁锂氧化物的质量百分比≥80％，第二活性材料层中的第二锰铁锂氧化物的质量百分比≤20％。例如，第一锰铁锂氧化物的质量百分比为85％、则第二锰铁锂氧化物的质量百分比为15％；第一锰铁锂氧化物的质量百分比为90％、则第二锰铁锂氧化物的质量百分比为10％；第一锰铁锂氧化物的质量百分比为83％、则第 二锰铁锂氧化物的质量百分比为17％；第一锰铁锂氧化物的质量百分比为88％、则第二锰铁锂氧化物的质量百分比为12％。
调整第一活性材料层中第一锰铁锂氧化物含量和第二活性材料层中第二锰铁锂氧化物含量的比例，可在一定范围内实现最优比例搭配，保证不损失电压范围的基础上，降低锰的溶解，实现二次电池的稳定循环。此外，控制第一活性材料层中第一锰铁锂氧化物的质量百分含量大于第二活性材料层中第二锰铁锂氧化物的质量百分含量，使得第一锰铁锂氧化物的质量百分比≥80％，第二活性材料层作为比较薄的一层保护层，第二锰铁锂氧化物的质量百分比≤20％，可保证足够的锰起到稳定电极的作用，提高正极活性材料的循环稳定性，扩大二次电池的电压范围，实现高能量密度。第一锰铁锂氧化物和第二锰铁锂氧化物的比例可通过面密度、厚度等参数进行调节。
在一些实施例中，所述第一锰铁锂氧化物的平均粒径为D1，所述第二锰铁锂氧化物的平均粒径为D2，满足D1>D2。
在一些实施例中，第二锰铁锂氧化物以颗粒状存在，粒径为200nm～500nm，具体地，可以为200、250、300、350、400、450、500或其中任意两个数组成的范围。第一锰铁锂氧化物的以颗粒状存在，粒径为为500～900nm，具体地，可以为500、550、600、650、700、750、800、850、900或其中任意两个数组成的范围。第二活性材料层中第二锰铁锂氧化物的粒径小能够有利于提高压实密度，形成紧密的锰铁锂氧化物外层。第一活性材料层与第二活性材料层之间的界面处具有不同粒径大小的锰铁锂氧化物颗粒可以有利于结合更紧密。
在一些实施例中，正极活性材料层还包括正极导电剂和正极粘结剂。
正极导电剂
正极导电剂的种类没有限制，可以使用任何已知的导电剂。正极导电剂的实例可包括，但不限于，天然石墨、人造石墨等石墨；乙炔黑等炭黑；针状焦等无定形碳等碳材料；碳纳米管；石墨烯等。上述正极导电剂可单独使用或任意组合使用。
正极粘结剂
正极活性材料层的制造中使用的正极粘结剂的种类没有特别限制，在涂布法的情况下，只要是在电极制造时使用的液体介质中可溶解或分散的材料即可。正极粘合剂的实例可包括，但不限于，以下中的一种或多种：聚乙烯、聚丙烯、聚对苯二甲酸乙二醇酯、聚甲基丙烯酸甲酯、聚酰亚胺、芳香族聚酰胺、纤维素、硝酸纤维素等树脂系高分子；丁苯橡胶(SBR)、丁腈橡胶(NBR)、氟橡胶、异戊二烯橡胶、聚丁橡胶、乙烯-丙烯橡胶等橡胶状高分 子；苯乙烯-丁二烯-苯乙烯嵌段共聚物或其氢化物、乙烯-丙烯-二烯三元共聚物(EPDM)、苯乙烯-乙烯-丁二烯-乙烯共聚物、苯乙烯-异戊二烯-苯乙烯嵌段共聚物或其氢化物等热塑性弹性体状高分子；间规-1,2-聚丁二烯、聚乙酸乙烯酯、乙烯-乙酸乙烯酯共聚物、丙烯-α-烯烃共聚物等软质树脂状高分子；聚偏氟乙烯(PVDF)、聚四氟乙烯、氟化聚偏二氟乙烯、聚四氟乙烯-乙烯共聚物等氟系高分子；具有碱金属离子(特别是锂离子)的离子传导性的高分子组合物等。上述正极粘结剂可单独使用或任意组合使用。
正极集流体
正极集流体的种类没有特别限制，其可为任何已知适于用作正极集流体的材质。正极集流体的实例可包括，但不限于，铝、不锈钢、镍镀层、钛、钽等金属材料；碳布、碳纸等碳材料；聚合物与金属层形成的复合材料。在一些实施例中，正极集流体为金属材料。在一些实施例中，正极集流体为铝。
正极集流体的形式没有特别限制。当正极集流体为金属材料时，正极集流体的形式可包括，但不限于，金属箔、金属圆柱、金属带卷、金属板、金属箔、金属板网、冲压金属、发泡金属等。当正极集流体为碳材料时，正极集流体的形式可包括，但不限于，碳板、碳薄膜、碳圆柱等。在一些实施例中，正极集流体为金属箔。在一些实施例中，所述金属箔为网状。金属箔的厚度没有特别限制。在一些实施例中，金属箔的厚度为大于1μm、大于3μm或大于5μm。在一些实施例中，金属箔的厚度为小于1mm、小于100μm或小于50μm。在一些实施例中，金属箔的厚度在上述任意两个数值所组成的范围内。
II、负极极片
负极极片包括负极集流体和设置于负极集流体的至少一个表面的负极活性材料层，负极活性材料层包含负极活性材料，负极活性材料包含石墨。
负极极片为单面极片或双面极片，当负极极片为单面极片时，负极活性材料层设置于负极集流体的一个表面，当负极极片为双面极片时，负极活性材料层设置于负极集流体的两个表面。负极极片上也可同时存在单面负极极片区域和双面负极极片区域。
负极集流体
在一些实施例中，负极集流体包括，但不限于，金属箔、金属圆柱、金属带卷、金属板、金属薄膜、金属板网、冲压金属、发泡金属等。在一些实施例中，负极集流体为金属箔。在一些实施例中，负极集流体为铝箔或铜箔。如本文所使用，术语“铜箔”包含铜合金箔。
在一些实施例中，负极集流体为导电性树脂。在一些实施例中，导电性树 脂包括在聚丙烯膜上蒸镀铜而得的膜。
负极活性材料层
负极活性材料层可以是一层或多层，多层负极活性材料层中的每层可以包含相同或不同的负极活性材料。负极活性材料为任何能够可逆地嵌入和脱嵌锂离子等金属离子的物质。在一些实施例中，负极活性材料的可充电容量大于正极活性材料的放电容量，以防止在充电期间锂金属析出在负极极片上。
在一些实施例中，负极活性材料层的厚度指的是涂布在负极集流体的单独一侧的负极活性材料层的厚度。在一些实施例中，单面负极活性材料层的厚度为15μm以上。在一些实施例中，单面负极活性材料层的厚度为20μm以上。在一些实施例中，单面负极活性材料层的厚度为30μm以上。在一些实施例中，单面负极活性材料层的厚度为150μm以下。在一些实施例中，单面负极活性材料层的厚度为120μm以下。在一些实施例中，单面负极活性材料层的厚度为100μm以下。在一些实施例中，负极活性材料层的厚度在由上述任意两个数值所组成的范围内。当负极活性材料层的厚度在上述范围内时，电解液可浸透到负极集流体界面附近，提高二次电池在高电流密度下的充放电特性；同时负极集流体相对于负极活性材料的体积比在适当范围内，可确保二次电池的容量。
在一些实施例中，负极活性材料层包括负极活性材料、负极导电剂和负极粘结剂。
负极活性材料
在一些实施例中，负极活性材料可选自石墨、软碳、硬碳、碳纤维、硅基材料、锡基材料中的一种或几种，进一步优选为石墨。
负极导电剂
在一些实施例中，导电剂包括炭黑、石墨、碳纤维、碳纳米管或石墨烯中的一种或多种，优选为炭黑。
负极粘结剂
粘结剂可提高负极活性材料之间的粘结。粘结剂的种类没有特别限制，只要是对于电解液或电极制造时使用的溶剂稳定的材料即可。在一些实施例中，粘结剂包括羧甲基纤维素钠和丁苯橡胶。
负极极片的制备
将负极活性材料石墨、导电剂CNT、增稠剂CMC、粘结剂SBR按质量比96.5：0.8：0.9：1.8进行混合加入溶剂去离子水真空搅拌至体系呈均一状，获得负极浆料，然后均匀涂敷在负极集流体铜箔的上下两个表面上，室温晾干后转移至烘箱继续干燥，以压实密度 1.7g/cm3的条件下冷压、分切后得负极极片。
III、电解液
在一些实施例中，电解液包括锂盐和溶剂。在一些实施例中，电解液进一步包括添加剂。
锂盐
在一些实施例中，锂盐包括六氟磷酸锂、有机硼酸锂、高氯酸锂、磺酰亚胺类锂盐中的至少一种。锂盐的含量没有特别限制，只要不损害本申请的效果即可。
溶剂
在一些实施例中，所述电解液进一步包含现有技术中已知的任何可作为电解液的溶剂的非水溶剂。
在一些实施例中，所述非水溶剂包括，但不限于，以下中的一种或多种：环状碳酸酯和链状碳酸酯。
在一些实施例中，所述环状碳酸酯的实例可包括，但不限于，以下中的一种或多种：碳酸亚乙酯(EC)、碳酸亚丙酯(PC)和碳酸亚丁酯。在一些实施例中，所述环状碳酸酯具有3-6个碳原子。
在一些实施例中，所述链状碳酸酯的实例可包括，但不限于，以下中的一种或多种：碳酸二甲酯、碳酸甲乙酯、碳酸二乙酯(DEC)、碳酸甲基正丙基酯、碳酸乙基正丙基酯、碳酸二正丙酯等链状碳酸酯等。被氟取代的链状碳酸酯的实例可包括，但不限于，以下中的一种或多种：双(氟甲基)碳酸酯、双(二氟甲基)碳酸酯、双(三氟甲基)碳酸酯、双(2-氟乙基)碳酸酯、双(2,2-二氟乙基)碳酸酯、双(2,2,2-三氟乙基)碳酸酯、2-氟乙基甲基碳酸酯、2,2-二氟乙基甲基碳酸酯和2,2,2-三氟乙基甲基碳酸酯等。
添加剂
在一些实施例中，所述添加剂的实例可包括，但不限于，以下的一种或多种：氟代碳酸酯、含碳碳双键的碳酸乙烯酯、含硫氧双键的化合物和酸酐。
IV、隔膜
为了防止短路，在正极与负极之间通常设置有隔膜。这种情况下，本申请的电解液通常渗入该隔膜而使用。隔膜材料可选用较为常见的任意隔膜材料，如聚乙烯、聚丙烯、聚偏氟乙烯以及多种复合膜组成的隔膜。进一步优选为聚丙烯膜。
在一些实施例中，二次电池的制备方法包括如下步骤：
1)制备磷酸锰铁锂浆料
将第一磷酸锰铁锂与导电剂、粘结剂添加入装有N-甲基吡咯烷酮(NMP)的搅拌罐里，配置成混合均匀、粘度稳定的浆料A；；将第二磷酸锰铁锂与导电剂、粘结剂添加入装有NMP的搅拌罐里，配置成混合均匀、粘度稳定的浆料C；
2)制备正极极片
将浆料A涂制在作为正极集流体的铝箔的一面，烘干，然后在铝箔的另一个表面涂覆相应厚度和质量的浆料A，并进行烘干，得到两面分别涂有浆料的铝箔层，进行辊压至两面分别为0.12mm，在正极集流体的两个表面分别形成第一活性材料层；
再将涂料C涂覆在第一活性材料层上，两面均需涂覆，烘干，再进行辊压至正极集流体的单面涂层厚度为0.14mm左右，分切、裁片后得到正极极片。
3)制作电池
将做好的正极极片与负极极片、隔膜进行卷绕或者叠片制作电芯，依次经注液、化成、分容等工艺后制成相应的二次电池。
下面结合具体实施例对本申请提供的二次电池的制备方法做出如下说明：
实施例1
(1)正极极片的制备
将颗粒平均粒径为600nm的LiMn0.6Fe0.4PO4、导电剂乙炔黑和粘结剂PVDF按质量比88:4:8混合后，加入装有N-甲基吡咯烷酮溶液(NMP)的搅拌罐里，配置成混合均匀、粘度稳定的浆料A；将颗粒平均粒径为400nm的LiMn0.1Fe0.9PO4与导电剂乙炔黑、粘结剂PVDF按照质量比88:4:8混合后，添加入装有NMP的搅拌罐里，配置成混合均匀、粘度稳定的浆料C；
将浆料A涂制在铝箔的一面，烘干，烘干后再铝箔的另一个表面涂覆浆料A，并进行烘干，得到两面分别涂有浆料A的第一活性材料层，进行辊压至两面分别为0.12mm；再将浆料C涂覆在第一活性材料层上，两面均需涂覆，烘干，再进行辊压至正极集流体的单个表面上的涂层厚度为0.14mm左右，形成第二活性材料层，分切、裁片后得到正极极片；其中，正极极片中LiMn0.6Fe0.4PO4与LiMn0.1Fe0.9PO4的质量比为9:1；
(2)负极极片的制备
将负极活性材料石墨、导电剂CNT、增稠剂CMC、粘结剂SBR按质量比96.5：0.8：0.9：1.8进行混合，加入溶剂去离子水，真空搅拌至体系呈均一状，获得负极浆料，然后均匀涂敷在负极集流体铜箔的上下两个表面上，室温晾干后转移至烘箱继续干燥，以压实密度1.7g/cm3的条件下冷压、分切、裁片后得负极极片。
(3)电解液的制备
将碳酸乙烯酯(EC)、碳酸甲乙酯(EMC)、碳酸二乙酯(DEC)按照按体积比1:1:1进行混合得到有机溶剂，接着将充分干燥的锂盐LiPF6溶解于混合后的有机溶剂中，配制成浓度为1mol/L的电解液。
(4)隔离膜的制备
选自聚乙烯膜作为隔离膜。
(5)锂离子电池的制备
将上述正极极片、隔离膜、负极极片按顺序叠好，使隔离膜处于正、负极极片之间起到隔离的作用，然后卷绕得到裸电芯；将裸电芯置于外包装壳中，干燥后注入电解液，经过真空封装、静置、化成、整形等工序，获得锂离子电池。
实施例2
本实施例与实施例1的区别在于，正极极片中LiMn0.6Fe0.4PO4与LiMn0.1Fe0.9PO4的质量比为8:2。
实施例3
本实施例与实施例1的区别在于，使用LiMn0.2Fe0.8PO4代替LiMn0.1Fe0.9PO4。
实施例4
本实施例与实施例2的区别在于，使用LiMn0.2Fe0.8PO4代替LiMn0.1Fe0.9PO4。
实施例5
本实施例与实施例1的区别在于，使用LiMn0.7Fe0.3PO4代替LiMn0.6Fe0.4PO4。
实施例6
本实施例与实施例5的区别在于，正极极片中LiMn0.7Fe0.3PO4与LiMn0.1Fe0.9PO4的质量比为8:2。
实施例7
本实施例与实施例5的区别在于，使用LiMn0.2Fe0.8PO4代替LiMn0.1Fe0.9PO4。
实施例8
本实施例与实施例6的区别在于，使用LiMn0.2Fe0.8PO4代替LiMn0.1Fe0.9PO4。
实施例9
本实施例与实施例3的区别在于，正极极片中LiMn0.6Fe0.4PO4与LiMn0.2Fe0.8PO4的质量比为7:3。
实施例10
本实施例与实施例3的区别在于，正极极片中LiMn0.6Fe0.4PO4与LiMn0.2Fe0.8PO4的质量比为9.5:0.5。
实施例11
本实施例与实施例3的区别在于，使用LiMn0.3Fe0.7PO4代替LiMn0.2Fe0.8PO4。
实施例12
本实施例与实施例3的区别在于，使用LiMn0.5Fe0.5PO4代替LiMn0.6Fe0.4PO4。
实施例13
本实施例与实施例1的区别在于，使用LiMn0.8Fe0.2PO4代替LiMn0.6Fe0.4PO4。
实施例14
本实施例与实施例1的区别在于，使用LiMn0.9Fe0.1PO4代替LiMn0.6Fe0.4PO4。
实施例15
本实施例与实施例1的区别在于，LiMn0.6Fe0.4PO4的平均粒径为500nm，LiMn0.1Fe0.9PO4的平均粒径为300nm。
实施例16
本实施例与实施例1的区别在于，LiMn0.6Fe0.4PO4的平均粒径为900nm，LiMn0.1Fe0.9PO4的平均粒径为500nm。
实施例17
本实施例与实施例1的区别在于，LiMn0.6Fe0.4PO4的平均粒径为400nm，LiMn0.1Fe0.9PO4的平均粒径为600nm。
实施例18
本实施例与实施例1的区别在于，LiMn0.6Fe0.4PO4的平均粒径为600nm，LiMn0.1Fe0.9PO4的平均粒径为200nm。
实施例19
本实施例与实施例1的区别在于，LiMn0.6Fe0.4PO4的平均粒径为400nm，LiMn0.1Fe0.9PO4的平均粒径为200nm。
对比例1
1)将颗粒平均粒径为600nm的LiMn0.6Fe0.4PO4与导电剂乙炔黑、粘结剂PVDF按质量比88：4：8混合后，加入装有N-甲基吡咯烷酮溶液(NMP)的搅拌罐里，配置成混合均匀、粘度稳定的浆料；
2)将浆料涂制在作为正极集流体的铝箔的一面，烘干，烘干后在铝箔的另一个表面涂 覆相应厚度和质量的浆料，并进行烘干，得到两面分别涂有浆料的铝箔层，进行辊压至两面分别为0.14mm，分切、裁片后得到正极极片；
3)将正极极片与实施例1所述负极极片和隔离膜按顺序叠好，使隔离膜处于正、负极极片之间起到隔离的作用，然后卷绕得到裸电芯；将裸电芯置于外包装壳中，干燥后注入实施例1所述电解液，经过真空封装、静置、化成、整形等工序，获得锂离子电池。
对比例2
1)将颗粒平均粒径为600nm的LiMn0.7Fe0.3PO4与导电剂乙炔黑、粘结剂PVDF按质量比为88：4：8混合后，加入装有N-甲基吡咯烷酮溶液(NMP)的搅拌罐里，配置成混合均匀、粘度稳定的浆料
2)将浆料涂制在铝箔的一面，烘干，烘干后再铝箔的另一个表面涂覆相应厚度和质量的浆料，并进行烘干，得到两面分别涂有浆料的铝箔层，进行辊压至两面分别为0.14mm，分切、裁片后得到正极极片；
3)将正极极片与实施例1所述负极极片和隔离膜按顺序叠好，使隔离膜处于正、负极极片之间起到隔离的作用，然后卷绕得到裸电芯；将裸电芯置于外包装壳中，干燥后注入实施例1所述电解液，经过真空封装、静置、化成、整形等工序，获得锂离子电池。
接下来说明本发明所涉及的测试。
制备二次电池前的正极极片锰溶出测试：
采用的仪器为光谱分析仪(ICP)，具体测试步骤为：
称量实施例1-19以及对比例1-2的正极极片各5g，然后分别置于装有100mL盐酸(浓度范围为0.01mol/L)的烧杯中，搅拌，静置，过滤得到样品溶液。
取1mL样品溶液，加少量硝酸酸化，定容，用ICP测试，得到样品溶液中锰元素的浓度(单位mg/L)。
容量测试：
把实施例1-19以及对比例1-2制作好的锂离子电池，在25±0.5℃条件下，用充放电测试系统进行充放电测试，充放电条件：充电终止电压4.3V；放电终止电压2.8V；充放电电流密度：0.1C。
循环性能测试：
把实施例1-19以及对比例1-2制作好的锂离子电池，在25±0.5℃条件下，用充放电测试系统进行充放电测试，充放电条件：充电终止电压4.3V；放电终止电压2.8V；充放电电流密度：1C，循环性能为1C条件下循环200周的循环性能，结果参见表1。
循环200圈后正极材料锰溶出测试：
锂离子电池经200圈循环测试后，拆解锂离子电池的负极极片，用0.1mol/L的HCl水溶液进行溶解，用原子吸收光谱法(AAS)测试HCl溶液中的锰离子的量，以此对比实施例1-19以及对比例1-2中锂离子电池的循环锰溶出情况。
表1
由表1可知，本申请实施例以锰含量较低的第二活性材料层作为保护外层，以锰含量较高的第一活性材料层作为内层，形成双层复合结构的正极活性材料层，第一活性材料层中的第一锰铁锂氧化物和第二活性材料层中的第二锰铁锂氧化物均具有优异的电化学性能，可以提高二次电池的循环性能。实施例与对比例相比，双层复合结构起到了有效减少锰溶出的效果，也提高了二次电池的电化学性能。
将实施例1、2与实施例3、4对比，将实施例5、6与实施例7、8对比，LiMn0.2Fe0.8PO4保护层的效果要比LiMn0.1Fe0.9PO4保护层的效果好，这与LiMn0.2Fe0.8PO4具有较小的晶粒有关，晶粒尺寸越小，锂离子在活性物质中的脱/嵌路径越短，可以提高锂离子的扩散速率。
将实施例1、2、3、4分别和实施例5、6、7、8对比，以及将实施例3、7、12可知，Mn：Fe的比例为6：4时电化学性能较优，例如表1所示的克容量和容量保持率方面的电化学性能。
将实施例1、3分别与实施例2、4对比，以及将实施例3、4、9、10对比可知，锰含量较高的第一活性材料层在正极活性材料层中的质量占比90％为较优比例，克容量和容量保持率方面的电化学性能较好。锰含量较低的第二活性材料层虽然能够提高导电率，但会损失一些稳定性和能量密度，第二活性材料层在正极活性材料层中的质量占比越高，会导致二次电池的克容量有一些降低，因此，第二活性材料层在正极活性材料层中的质量占比不宜过高，能发挥抑制锰溶解的作用即可。
以上对本申请实施例所提供的一种二次电池及用电设备进行了详细介绍，本文中应用了具体个例对本申请的原理及实施方式进行了阐述，以上实施例的说明只是用于帮助理解本申请的方法及其核心思想；同时，对于本领域的技术人员，依据本申请的思想，在具体实施方式及应用范围上均会有改变之处，综上所述，本说明书内容不应理解为对本申请的限制。

Claims (11)

  1. 一种二次电池，包括正极极片，其中，
    所述正极极片包括正极集流体和设置于所述正极集流体至少一个表面上的正极活性材料层；
    所述正极活性材料层包括第一活性材料层和第二活性材料层，所述第一活性材料层设置于所述正极集流体和所述第二活性材料层之间；
    所述第一活性材料层包括第一锰铁锂氧化物，所述第二活性材料层包括第二锰铁锂氧化物；
    基于除锂之外金属元素的总摩尔量，所述第一锰铁锂氧化物中锰元素的摩尔百分含量为n1％，所述第二锰铁锂氧化物中锰元素的摩尔百分含量为n2％，满足n1>n2。
  2. 根据权利要求1所述的二次电池，其中，30≤n1-n2≤80。
  3. 根据权利要求1所述的二次电池，其中，n1≥50。
  4. 根据权利要求1所述的二次电池，其中，n2≤20。
  5. 根据权利要求1所述的二次电池，其中，所述第一锰铁锂氧化物的平均粒径为D1，所述第二锰铁锂氧化物的平均粒径为D2，满足D1>D2。
  6. 根据权利要求5所述的二次电池，其中，500nm≤D1≤900nm。
  7. 根据权利要求5所述的二次电池，其中，200nm≤D2≤500nm。
  8. 根据权利要求1所述的二次电池，其中，以所述正极活性材料层中的第一锰铁锂氧化物和第二锰铁锂氧化物的总质量为100％计，所述第一活性材料层中的第一锰铁锂氧化物的质量百分比≥80％。
  9. 根据权利要求1所述的二次电池，其中，所述第一锰铁锂氧化物的通式包括LiaMnxFe1-xPO4，0.6≤x≤0.8，0.95≤a≤1.2。
  10. 根据权利要求1所述的二次电池，其中，所述第二锰铁锂氧化物的通式包括LibMnyFe1-yPO4，0＜y≤0.2，0.95≤b≤1.2。
  11. 一种用电设备，其中，包括权利要求1～10任意一项所述的二次电池。
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Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN106340639A (zh) * 2016-10-28 2017-01-18 合肥国轩高科动力能源有限公司 一种磷酸铁锂/碳包覆的核壳型磷酸锰铁锂复合正极材料及其制备方法
CN111092194A (zh) * 2018-10-23 2020-05-01 宁德时代新能源科技股份有限公司 一种正极极片、其制备方法以及锂离子二次电池
CN111200109A (zh) * 2018-11-16 2020-05-26 宁德时代新能源科技股份有限公司 一种电池
CN111293365A (zh) * 2020-02-21 2020-06-16 陆晨杰 一种锰酸锂电池的制备方法
CN114655943A (zh) * 2020-12-23 2022-06-24 比亚迪股份有限公司 磷酸锰铁锂复合材料及其制备方法、正极和锂离子电池
CN115020678A (zh) * 2022-07-12 2022-09-06 远景动力技术(江苏)有限公司 正极活性材料、电化学装置和电子设备
CN115458707A (zh) * 2022-10-26 2022-12-09 欣旺达电动汽车电池有限公司 二次电池及用电设备

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN106340639A (zh) * 2016-10-28 2017-01-18 合肥国轩高科动力能源有限公司 一种磷酸铁锂/碳包覆的核壳型磷酸锰铁锂复合正极材料及其制备方法
CN111092194A (zh) * 2018-10-23 2020-05-01 宁德时代新能源科技股份有限公司 一种正极极片、其制备方法以及锂离子二次电池
CN111200109A (zh) * 2018-11-16 2020-05-26 宁德时代新能源科技股份有限公司 一种电池
CN111293365A (zh) * 2020-02-21 2020-06-16 陆晨杰 一种锰酸锂电池的制备方法
CN114655943A (zh) * 2020-12-23 2022-06-24 比亚迪股份有限公司 磷酸锰铁锂复合材料及其制备方法、正极和锂离子电池
CN115020678A (zh) * 2022-07-12 2022-09-06 远景动力技术(江苏)有限公司 正极活性材料、电化学装置和电子设备
CN115458707A (zh) * 2022-10-26 2022-12-09 欣旺达电动汽车电池有限公司 二次电池及用电设备

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