WO2023108639A1 - 锂离子二次电池用正极复合材料及锂离子二次电池 - Google Patents

锂离子二次电池用正极复合材料及锂离子二次电池 Download PDF

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WO2023108639A1
WO2023108639A1 PCT/CN2021/139283 CN2021139283W WO2023108639A1 WO 2023108639 A1 WO2023108639 A1 WO 2023108639A1 CN 2021139283 W CN2021139283 W CN 2021139283W WO 2023108639 A1 WO2023108639 A1 WO 2023108639A1
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positive electrode
ion secondary
secondary battery
composite material
battery
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PCT/CN2021/139283
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English (en)
French (fr)
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董苗苗
欧阳少聪
付成华
别常峰
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宁德时代新能源科技股份有限公司
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Priority to CN202180097618.2A priority Critical patent/CN117242598A/zh
Priority to EP21944413.0A priority patent/EP4228028A4/en
Priority to PCT/CN2021/139283 priority patent/WO2023108639A1/zh
Priority to US18/066,288 priority patent/US20230197959A1/en
Publication of WO2023108639A1 publication Critical patent/WO2023108639A1/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
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • 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
    • 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
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • 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
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • 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
    • H01M4/362—Composites
    • H01M4/364—Composites as mixtures
    • 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
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • 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
    • H01M4/485—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of mixed oxides or hydroxides for inserting or intercalating light metals, e.g. LiTi2O4 or LiTi2OxFy
    • 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
    • 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
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/624—Electric conductive fillers
    • H01M4/625—Carbon or graphite
    • 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 technical field of lithium batteries, in particular to a positive electrode composite material for a lithium ion secondary battery, a positive electrode of a lithium ion secondary battery, a lithium ion secondary battery, a battery module, a battery pack and an electrical device.
  • Lithium-ion secondary batteries are widely used in electric vehicles due to their high charge and discharge performance, no memory effect, and environmental friendliness.
  • lithium-ion secondary batteries generally have poor low-temperature performance, they cannot meet the application requirements in low-temperature environments. For example, when a lithium iron phosphate secondary battery is applied to an electric vehicle, in a low-temperature environment, the discharge curve of the lithium iron phosphate battery drops sharply at the end of the discharge voltage plateau, and due to the increase in the diffusion resistance of lithium ions in the positive electrode The power performance becomes worse; when the battery is tested under the CLTC working condition (CLTC: China light-duty vehicle test cycle, single test time 1800s), when the battery reaches the peak discharge power at the end of the battery discharge , due to the sharp drop in voltage, the battery cannot cross the power peak to continue operating CLTC conditions, resulting in discharge cutoff and a decrease in the overall discharge capacity of the battery.
  • CLTC China light-duty vehicle test cycle, single test time 1800s
  • This application was made in view of the said subject, and the object of this application aims at improving the low-temperature performance of a lithium ion secondary battery.
  • the first aspect of the present application provides a positive electrode composite material for lithium ion secondary batteries, which includes: positive electrode active material, which is selected from at least one of lithium iron phosphate material and nickel cobalt lithium manganese oxide material and at least one of the compounds represented by A a M b (PO 4 ) c X d , wherein A is selected from at least one of Li, Na, K and Ca, and M is selected from at least one of V and Mn One, X is selected from any one of the halogen elements, and a, b, and c are each independently selected from an integer of 1-6, and d is an integer selected from 0-3.
  • the positive electrode composite material for lithium ion secondary batteries preferably, when the discharge rate of the lithium ion secondary battery is 0.33C, the positive electrode composite material can have reversible charge and discharge in the voltage range below 3.0V. platform.
  • the positive electrode active material and the compound represented by A a M b (PO 4 ) c X d total 100% by weight, and the compound represented by A a M b (PO 4
  • the content of the compound represented by ) c X d is preferably 3% by weight to 10% by weight.
  • the compound represented by A a M b (PO 4 ) c X d is selected from Li 3 V 2 (PO 4 ) 3 , Na 3 V 2 (PO 4 ) 3 , K 3 V 2 (PO 4 ) 3 , Li 3 V(PO 4 ) 2 , Na 3 V(PO 4 ) 2 , K 3 V(PO 4 ) 2 , LiMnPO 4 , NaMnPO 4 , KMnPO 4 , Li 2 VMn 2 (PO 4 ) 3 , Na 2 VMn 2 (PO 4 ) 3 , K 2 VMn 2 (PO 4 ) 3 , LiVMn(PO 4 ) 2 , NaVMn(PO 4 ) 2 , KVMn(PO 4 ) 2 , At least one of LiVPO 4 F, CaV 4 (PO 4 ) 6 , NaVPO 4 F, and KVPO 4 F.
  • the lithium iron phosphate material is selected from at least one of LiFePO 4 , doped LiFePO 4 , carbon-coated LiFePO 4 or carbon-coated doped LiFePO 4
  • the lithium nickel cobalt manganese oxide material is LiNi m Co n Mn 1-mn O 2 , where 0.3 ⁇ m ⁇ 0.9, 0 ⁇ n ⁇ 0.3.
  • the second aspect of the present application provides a positive electrode of a lithium ion secondary battery, which includes: a positive electrode current collector and a positive electrode membrane comprising a positive electrode composite material disposed on at least one surface of the positive electrode current collector, the positive electrode composite
  • the material is the positive electrode composite material according to the first aspect of the present application.
  • a third aspect of the present application provides a lithium ion secondary battery, including the positive electrode of the lithium ion secondary battery according to the second aspect of the present application.
  • a fourth aspect of the present application provides a battery module including the lithium ion secondary battery of the third aspect of the present application.
  • a fifth aspect of the present application provides a battery pack, including the battery module of the fourth aspect of the present application.
  • the sixth aspect of the present application provides an electric device, including at least one of the lithium-ion secondary battery of the third aspect of the present application, the battery module of the fourth aspect of the present application, and the battery pack of the fifth aspect of the present application kind.
  • the positive electrode composite material of the present application can increase the maximum power of the lithium-ion secondary battery at a low state of charge under low temperature conditions, and improve the discharge capacity and discharge capacity retention rate at low temperature conditions.
  • any lower limit can be combined with any upper limit to form an unexpressed range; and any lower limit can be combined with any other lower limit to form an unexpressed range, just as any upper limit can be combined with any other upper limit to form an unexpressed range.
  • every point or individual value between the endpoints of a range is included within that range, although not expressly stated herein. Thus, each point or individual value may serve as its own lower or upper limit in combination with any other point or individual value or with other lower or upper limits to form a range not expressly recited.
  • the first aspect of the present application relates to a positive electrode composite material for a lithium ion secondary battery.
  • the positive electrode composite material includes a positive electrode active material.
  • positive active materials known in the art for batteries may be used as the positive active material.
  • the positive active material may include at least one of the following materials: olivine-structured lithium-containing phosphate, lithium transition metal oxide, and their respective modification compounds. These positive electrode active materials may be used alone or in combination of two or more.
  • the positive electrode active material is selected from at least one of lithium iron phosphate material and nickel cobalt lithium manganese oxide material.
  • the lithium iron phosphate material may be selected from lithium iron phosphate (such as LiFePO 4 , which may be referred to as LFP for short), doped LiFePO 4 , carbon-coated LiFePO 4 or carbon-coated doped LiFePO 4 .
  • lithium iron phosphate such as LiFePO 4 , which may be referred to as LFP for short
  • doped LiFePO 4 carbon-coated LiFePO 4 or carbon-coated doped LiFePO 4 .
  • Nickel cobalt lithium manganate material can be LiNi m Co n Mn 1-mn O 2 , where 0.3 ⁇ m ⁇ 0.9, 0 ⁇ n ⁇ 0.3, such as LiNi 1/3 Co 1/3 Mn 1/3 O 2 , LiNi 0.5 Co 0.2 Mn 0.3 O 2 , LiNi 0.5 Co 0.25 Mn 0.25 O 2 , LiNi 0.6 Co 0.2 Mn 0.2 O 2 , LiNi 0.65 Co 0.07 Mn 0.37 O 2 , LiNi 0.8 Co 0.1 Mn 0.1 O 2 , etc.
  • the present application is not limited to these materials, and other conventional materials that can be used as positive electrode active materials of batteries can also be used.
  • the positive electrode composite material for lithium ion secondary battery includes: a positive electrode active material selected from at least one of lithium iron phosphate material and nickel cobalt lithium manganese oxide material; and A a M b (PO 4 ) At least one of the compounds represented by c X d , wherein A is selected from at least one of Li, Na, K and Ca, M is selected from at least one of V and Mn, and X is selected from halogen Any one of group elements, and a, b, c are each independently selected from an integer of 1-6, and d is an integer selected from 0-3.
  • an appropriate amount of the compound represented by the above-mentioned A a M b (PO 4 ) c X d is added to the positive electrode composite material.
  • a reversible charge-discharge plateau can be observed in the lower voltage range.
  • a voltage plateau at a lower voltage level is correspondingly introduced into the entire discharge voltage distribution curve of the battery.
  • M in the compound is a valence-changing element V
  • V in the discharge curve of 0.33C discharge
  • Mn the reversible charge-discharge platform range in the battery discharge curve
  • the positive electrode composite material can have a reversible charge-discharge platform in the voltage range below 3.0V.
  • the compound represented by A a M b (PO 4 ) c X d preferably, with respect to a total of 100% by weight of the positive active material and the compound represented by A a M b (PO 4 ) c X d , the compound represented by A a M b (PO 4 ) c X d
  • the content of the compound is 3% by weight to 10% by weight. If the content of the compound represented by A a M b (PO 4 ) c X d is less than 3% by weight, since the content is too low, a clear reversible charge-discharge plateau may not be observed in the low state of charge of the battery, thereby failing to function. To alleviate the sharp drop in voltage at the end of the discharge. If the content of the compound represented by A a M b (PO 4 ) c X d is greater than 10% by weight, the overall capacity of the battery may be reduced due to a corresponding decrease in the content of the positive electrode active material.
  • the compound represented by A a M b (PO 4 ) c X d is selected from Li 3 V 2 (PO 4 ) 3 , Na 3 V 2 (PO 4 ) 3 , K 3 V 2 (PO 4 ) 3 , Li 3 V(PO 4 ) 2 , Na 3 V(PO 4 ) 2 , K 3 V(PO 4 ) 2 , LiMnPO 4 , NaMnPO 4 , KMnPO 4 , Li 2 VMn 2 (PO 4 ) 3 , Na 2 VMn 2 (PO 4 ) 3 , K 2 VMn 2 (PO 4 ) 3 , LiVMn(PO 4 ) 2 , NaVMn(PO 4 ) 2 , KVMn(PO 4 ) 2 , LiVPO 4 F, CaV 4 ( At least one of PO 4 ) 6 , NaVPO 4 F, and KVPO 4 F.
  • the second aspect of the present application relates to a positive electrode of a lithium-ion secondary battery, which includes: a positive electrode current collector and a positive electrode membrane comprising the above-mentioned positive electrode composite material disposed on at least one surface of the positive electrode current collector.
  • the third aspect of the present application relates to a lithium ion secondary battery, which includes the positive electrode of the lithium ion secondary battery according to the second aspect of the present application.
  • a lithium-ion secondary battery includes an outer packaging bag and a battery cell and an electrolyte disposed in the outer packaging bag, and the battery cell includes a positive pole piece, a negative pole piece and a separator.
  • the specific types and compositions of the separator and the electrolyte are not subject to specific restrictions, and can be selected according to actual needs.
  • the isolation film may be selected from polyethylene film, polypropylene film, polyvinylidene fluoride film and their multilayer composite films.
  • a lithium salt solution dissolved in an organic solvent is generally used as the nonaqueous electrolyte.
  • Lithium salts are, for example, LiClO 4 , LiPF 6 , LiBF 4 , LiAsF 6 , LiSbF 6 and other inorganic lithium salts, or LiCF 3 SO 3 , LiCF 3 CO 2 , Li 2 C 2 F 4 (SO 3 ) 2 , LiN(CF 3 Organic lithium salts such as SO 2 ) 2 , LiC(CF 3 SO 2 ) 3 , LiC n F 2n+1 SO 3 (n ⁇ 2).
  • the organic solvent used in the non-aqueous electrolyte is, for example, cyclic carbonates such as ethylene carbonate, propylene carbonate, butylene carbonate, vinylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, etc.
  • Equal chain carbonates chain esters such as methyl propionate, cyclic esters such as ⁇ -butyrolactone, chains such as dimethoxyethane, diethyl ether, diglyme, and triglyme ethers, cyclic ethers such as tetrahydrofuran and 2-methyltetrahydrofuran, nitriles such as acetonitrile and propionitrile, or mixtures of these solvents.
  • the lithium ion secondary battery of the present application will be briefly described below.
  • a positive electrode sheet is prepared according to a conventional method in the art.
  • a conductive agent such as Super P, etc.
  • a binder such as PVDF
  • Other additives may also be added as needed.
  • These materials are usually mixed together and dispersed in a solvent (such as NMP), stirred evenly, coated on the positive electrode current collector, and dried to obtain the positive electrode sheet.
  • Materials such as metal foil such as aluminum foil or porous metal plate can be used as the positive electrode current collector. Aluminum foil is preferably used.
  • the negative electrode sheet of the present application can be prepared by a known method in the art. Usually, the negative electrode active material and optional conductive agent (such as Super P, etc.), binder (such as SBR, etc.), other optional additives and other materials are mixed together and dispersed in a solvent (such as deionized water), and stirred evenly Afterwards, it is evenly coated on the negative electrode current collector, and after drying, the negative electrode sheet containing the negative electrode film layer is obtained.
  • a solvent such as deionized water
  • Materials such as metal foil such as copper foil or porous metal plate can be used as the negative electrode current collector. Copper foil is preferably used.
  • the proportion of active materials in the positive and negative film layers should not be too low, otherwise the capacity will be too low; the proportion of active materials should not be too high, otherwise the conductive agent and binder will be damaged. Reduced, the conductivity of the electrode sheet and the degree of adhesion to the current collector are reduced, which in turn leads to a decrease in the electrical performance of the cell.
  • the current collector When preparing positive and negative electrode sheets, the current collector can be coated on both sides or on one side.
  • the lithium-ion secondary battery of the present application can form a battery module, and the battery module can form a battery pack.
  • the electric device includes at least one of the lithium-ion secondary battery, the battery module, and the battery pack provided in this application.
  • a lithium-ion secondary battery, a battery module, or a battery pack can be used as a power source of a power consumption device, and can also be used as an energy storage unit of the power consumption device.
  • Electric devices can include mobile devices (such as mobile phones, tablet computers, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf vehicles, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but not limited thereto.
  • mobile devices such as mobile phones, tablet computers, laptops, etc.
  • electric vehicles such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf vehicles, electric trucks, etc.
  • electric trains ships and satellites, energy storage systems, etc., but not limited thereto.
  • the positive electrode sheet is prepared in a conventional manner, and the positive electrode sheet includes a positive electrode composite material, conductive carbon and a binder.
  • the positive electrode composite material includes a positive electrode active material and an additive, the positive electrode active material is at least one of lithium iron phosphate material and nickel cobalt lithium manganese oxide material, and the additive is represented by A a M b (PO 4 ) c X d in the compound
  • the content of the additive is 3 to 10% by weight relative to a total of 100% by weight of the positive electrode active material and the compound represented by A a M b (PO 4 ) c X d .
  • the positive electrode active material accounts for 85% of the total mass of the positive electrode coating, and the compacted density is 2.4 g/cm 3 .
  • the positive electrode active material is LiFePO 4
  • the additive is Li 3 V 2 (PO 4 ) 3 .
  • the content of LiFePO 4 was 97%, and the content of Li 3 V 2 (PO 4 ) 3 was 3% with respect to the total weight of both.
  • the positive electrode active material is LiFePO 4
  • the additive is Li 3 V 2 (PO 4 ) 3 .
  • the content of LiFePO 4 was 95%, and the content of Li 3 V 2 (PO 4 ) 3 was 5% with respect to the total weight of both.
  • the positive electrode active material is LiFePO 4
  • the additive is Li 3 V 2 (PO 4 ) 3 .
  • the content of LiFePO 4 was 90%, and the content of Li 3 V 2 (PO 4 ) 3 was 10% with respect to the total weight of both.
  • the positive electrode active material is LiFePO 4
  • the additive is Li 3 V 2 (PO 4 ) 3 .
  • the content of LiFePO 4 was 98%, and the content of Li 3 V 2 (PO 4 ) 3 was 2% with respect to the total weight of both.
  • the positive electrode active material is LiFePO 4
  • the additive is Li 3 V 2 (PO 4 ) 3 .
  • the content of LiFePO 4 was 88%, and the content of Li 3 V 2 (PO 4 ) 3 was 12% with respect to the total weight of both.
  • Embodiment 6 is a diagrammatic representation of Embodiment 6
  • the positive electrode active material is LiFePO 4
  • the additive is LiMnPO 4 .
  • the content of LiFePO 4 was 95% and the content of LiMnPO 4 was 5% relative to the total weight of both.
  • Embodiment 7 is a diagrammatic representation of Embodiment 7:
  • the positive electrode active material is LiFePO 4
  • the additive is KVMn(PO 4 ) 2 .
  • the content of LiFePO 4 was 95%, and the content of KVMn(PO 4 ) 2 was 5% with respect to the total weight of both.
  • Embodiment 8 is a diagrammatic representation of Embodiment 8
  • the positive electrode active material is LiFePO 4
  • the additive is NaVPO 4 F.
  • the content of LiFePO 4 was 95% and the content of NaVPO 4 F was 5% with respect to the total weight of both.
  • Embodiment 9 is a diagrammatic representation of Embodiment 9:
  • the positive electrode active material is LiFePO 4
  • the additive is CaV 4 (PO 4 ) 6
  • the content of LiFePO 4 was 95%
  • the content of CaV 4 (PO 4 ) 6 was 5% with respect to the total weight of both.
  • the positive electrode active material is LiNi 0.65 Co 0.07 Mn 0.37 O 2
  • the additive is Li 3 V 2 (PO 4 ) 3 .
  • the content of LiNi 0.65 Co 0.07 Mn 0.37 O 2 was 95%, and the content of Li 3 V 2 (PO 4 ) 3 was 5% based on the total weight of both.
  • the positive electrode active material is LiNi 0.65 Co 0.07 Mn 0.37 O 2
  • the additive is NaMnPO 4 .
  • the content of LiNi 0.65 Co 0.07 Mn 0.37 O 2 was 95%, and the content of NaMnPO 4 was 5% relative to the total weight of both.
  • the positive electrode active material is LiNi 0.65 Co 0.07 Mn 0.37 O 2
  • the additive is Li 2 VMn 2 (PO 4 ) 3 .
  • the content of LiNi 0.65 Co 0.07 Mn 0.37 O 2 was 95%, and the content of Li 2 VMn 2 (PO 4 ) 3 was 5% based on the total weight of both.
  • the positive electrode active material is LiNi 0.65 Co 0.07 Mn 0.37 O 2
  • the additive is KVPO 4 F.
  • the content of LiNi 0.65 Co 0.07 Mn 0.37 O 2 was 95%, and the content of KVPO 4 F was 5% with respect to the total weight of both.
  • the positive electrode active material is LiNi 0.65 Co 0.07 Mn 0.37 O 2
  • the additive is CaV 4 (PO 4 ) 6
  • the content of LiNi 0.65 Co 0.07 Mn 0.37 O 2 was 95%
  • the content of CaV 4 (PO 4 ) 6 was 5% based on the total weight of both.
  • the positive electrode active material is a mixture of LiFePO 4 and LiNi 0.65 Co 0.07 Mn 0.37 O 2 with a weight ratio of 1:1, and the additive is Li 3 V 2 (PO 4 ) 3 .
  • the content of the mixture of LiFePO 4 and LiNi 0.65 Co 0.07 Mn 0.37 O 2 was 95%, and the content of Li 3 V 2 (PO 4 ) 3 was 5% relative to the total weight of both.
  • the positive electrode active material is LiFePO 4 , and the positive electrode material does not contain additives.
  • the positive electrode active material is LiNi 0.65 Co 0.07 Mn 0.37 O 2 , and the positive electrode material does not contain additives.
  • the battery cells of Examples 1-15 and Comparative Examples 1-2 were tested, and the corresponding low-temperature performance was tested, and the test method was as follows.
  • the battery capacity test at 25°C is as follows: place the battery at 25°C until the battery temperature is constant at 25°C; charge with a current of 1/3C to the end-of-charge voltage (3.65V when the positive active material is LiFePO 4 ; 4.35V when the active material is LiNi 0.65 Co 0.07 Mn 0.37 O 2 or a mixture of LiFePO 4 and LiNi 0.65 Co 0.07 Mn 0.37 O 2 ); stand for 10 minutes; charge to the end-of-charge voltage with a current of 0.05C; stand for 10 Minutes; discharge at a current of 1/3C to the end-of-discharge voltage, and record the discharge capacity at this step as the discharge capacity Cn of the battery at 25°C@0.33C.
  • the actual discharge capacity test of -7°C battery CLTC is as follows: put the battery in an environment of 25°C and let it stand until the battery temperature is 25°C; charge it with a current of 1/3C to the end-of-charge voltage; let it stand for 10 minutes; Charge the current to the end-of-charge voltage; stand still for 10 minutes; place the battery at -7°C until the battery temperature is constant at -7°C; discharge to the end-of-discharge voltage according to the CLTC working condition of the battery cell, and record the discharge capacity of this step As the actual discharge capacity of the battery at -7°C.
  • the voltage platform comprising the additive of variable valence elements (V and/or Mn) is shown, and they The voltage platform includes a voltage platform below 3.0V, that is, a lower voltage platform.
  • the positive electrode active material can be a mixed system of lithium iron phosphate and nickel-cobalt lithium manganese oxide.
  • the battery performance is also improved. low temperature performance.
  • the preferred content range of the additive in the present application is 3 to 10% by weight. See Examples 1-3, which can not only improve the power characteristics under low charge state in low temperature environment, but also improve the actual discharge capacity and discharge capacity retention rate under CLTC working conditions, without reducing the discharge capacity of the battery at normal temperature.
  • the present application is not limited to the above-mentioned embodiments.
  • the above-mentioned embodiments are merely examples, and within the scope of the technical solutions of the present application, embodiments that have substantially the same configuration as the technical idea and exert the same effects are included in the technical scope of the present application.
  • various modifications conceivable by those skilled in the art are added to the embodiments, and other forms constructed by combining some components in the embodiments are also included in the scope of the present application. .

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Abstract

本申请提供一种锂离子二次电池用正极复合材料及锂离子二次电池，所述锂离子二次电池用正极复合材料包括：正极活性物质，其选自磷酸铁锂材料和镍钴锰酸锂材料中的至少一种；和由A aM b(PO 4) cX d表示的化合物中的至少一种，其中，A选自Li、Na、K和Ca中的至少一种，M选自V和Mn中的至少一种，X选自卤族元素中的任一种，并且a、b、c各自独立地选自1～6的整数，d为选自0～3的整数。

Description

锂离子二次电池用正极复合材料及锂离子二次电池 技术领域
本申请涉及锂电池技术领域，尤其涉及一种锂离子二次电池用正极复合材料、锂离子二次电池的正极、锂离子二次电池、电池模块、电池包和用电装置。
背景技术
锂离子二次电池由于具备较高的充放电性能，且无记忆效应、环境友好，被广泛地应用于电动车辆。
由于锂离子二次电池通常低温性能较差，因此尚不能满足在低温环境中的应用需求。例如，在将磷酸铁锂二次电池应用于电动车辆的情况下，在低温环境中，磷酸铁锂电池的放电曲线在放电末期电压平台急剧降低，而且由于锂离子在正极的扩散阻抗增大导致功率性能变差；当在CLTC工况流程下(CLTC：中国轻型汽车行驶工况China light-duty vehicle test cycle，单次测试时间1800s)对电池进行测试时，在电池放电末期达到放电功率峰值时，由于电压的急剧降低，使电池无法越过功率峰值以继续运行CLTC工况，从而导致放电截止、电池的整体放电容量降低。
因此，锂离子二次电池的低温性能有待改进。
发明内容
本申请是鉴于上述课题进行的，本申请的目的旨在改善锂离子二次电池的低温性能。
为了达到上述目的，本申请的第一方面提供一种锂离子二次电池用正极复合材料，其包括：正极活性物质，其选自磷酸铁锂材料和镍钴锰酸锂材料中的至少一种；和由A aM b(PO 4) cX d表示的化合物中的至少一种，其中，A选自Li、Na、K和Ca中的至少一种，M选自V和Mn中的至少一种，X选自卤族元素中的任一种，并且a、b、c各自独立地选自1～6的整数，d为选自0～3的整数。
在本申请提供的锂离子二次电池用正极复合材料中，优选地，在锂离子二次电池的的放电倍率为0.33C时，正极复合材料可在3.0V以下的电压范围内具有可逆充放电平台。
在本申请提供的锂离子二次电池用正极复合材料中，以正极活性物质和由A aM b(PO 4) cX d表示的化合物总计100重量％计，由A aM b(PO 4) cX d表示的化合物的含量优选为3重量％～10重量％。
在本申请提供的锂离子二次电池用正极复合材料中，由A aM b(PO 4) cX d表示的化合物选 自Li 3V 2(PO 4) 3、Na 3V 2(PO 4) 3、K 3V 2(PO 4) 3、Li 3V(PO 4) 2、Na 3V(PO 4) 2、K 3V(PO 4) 2、LiMnPO 4、NaMnPO 4、KMnPO 4、Li 2VMn 2(PO 4) 3、Na 2VMn 2(PO 4) 3、K 2VMn 2(PO 4) 3、LiVMn(PO 4) 2、NaVMn(PO 4) 2、KVMn(PO 4) 2、LiVPO 4F、CaV 4(PO 4) 6、NaVPO 4F、KVPO 4F中的至少一种。
在本申请提供的锂离子二次电池用正极复合材料中，磷酸铁锂材料选自LiFePO 4、掺杂的LiFePO 4、碳包覆的LiFePO 4或碳包覆的掺杂的LiFePO 4中的至少一种；镍钴锰酸锂材料为LiNi mCo nMn 1-m-nO 2，其中0.3≤m≤0.9，0≤n≤0.3。
本申请的第二方面提供一种锂离子二次电池的正极，其包括：正极集流体和设置于所述正极集流体的至少一个表面上的包含正极复合材料的正极膜片，所述正极复合材料为根据本申请第一方面的正极复合材料。
本申请的第三方面提供一种锂离子二次电池，包括本申请第二方面的锂离子二次电池的正极。
本申请的第四方面提供一种电池模块，包括本申请的第三方面的锂离子二次电池。
本申请的第五方面提供一种电池包，包括本申请的第四方面的电池模块。
本申请的第六方面提供一种用电装置，包括本申请的第三方面的锂离子二次电池、本申请的第四方面的电池模块和本申请的第五方面的电池包中的至少一种。
由此，本申请的正极复合材料能够提高锂离子二次电池在低温条件下低荷电状态时的最大功率，提高低温条件下的放电容量以及放电容量保持率。
具体实施方式
为了使本申请的发明目的、技术方案和有益技术效果更加清晰，以下结合具体实施例对本申请进行详细说明。应当理解的是，本说明书中描述的实施例仅仅是为了解释本申请，并非为了限定本申请。
为了简便，本文仅明确地公开了一些数值范围。然而，任意下限可以与任何上限组合形成未明确记载的范围；以及任意下限可以与其它下限组合形成未明确记载的范围，同样任意上限可以与任意其它上限组合形成未明确记载的范围。此外，尽管未明确记载，但是范围端点间的每个点或单个数值都包含在该范围内。因而，每个点或单个数值可以作为自身的下限或上限与任意其它点或单个数值组合或与其它下限或上限组合形成未明确记载的范围。
在本文的描述中，需要说明的是，除非另有说明，“以上”、“以下”为包含本数，“一种或几种”中“几种”的含义是两种及两种以上。
本申请的上述发明内容并不意欲描述本申请中的每个公开的实施方式或每种实现方式。如下描述更具体地举例说明示例性实施方式。在整篇申请中的多处，通过一系列实施例提供了指导，这些实施例可以以各种组合形式使用。在各个实例中，列举仅作为代表性组，不应解释为穷举。
本申请的第一方面涉及锂离子二次电池用正极复合材料。正极复合材料包括正极活性物质。在本申请中，正极活性物质可采用本领域公知的用于电池的正极活性物质。作为示例，正极活性物质可包括以下材料中的至少一种：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。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。优选的，正极活性物质选自磷酸铁锂材料和镍钴锰酸锂材料中的至少一种。其中，磷酸铁锂材料可以选自磷酸铁锂(如LiFePO 4，可简称为LFP)、掺杂的LiFePO 4、碳包覆的LiFePO 4或碳包覆的掺杂的LiFePO 4。镍钴锰酸锂材料可以为LiNi mCo nMn 1-m-nO 2，其中0.3≤m≤0.9，0≤n≤0.3，例如LiNi 1/3Co 1/3Mn 1/3O 2、LiNi 0.5Co 0.2Mn 0.3O 2、LiNi 0.5Co 0.25Mn 0.25O 2、LiNi 0.6Co 0.2Mn 0.2O 2、LiNi 0.65Co 0.07Mn 0.37O 2、LiNi 0.8Co 0.1Mn 0.1O 2等。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物质的传统材料。
在本申请的一种实施方式中，锂离子二次电池用正极复合材料包括：选自磷酸铁锂材料和镍钴锰酸锂材料中的至少一种的正极活性物质；和由A aM b(PO 4) cX d表示的化合物中的至少一种，其中，A选自Li、Na、K和Ca中的至少一种，M选自V和Mn中的至少一种，X选自卤族元素中的任一种，并且，a、b、c各自独立地选自1～6的整数，d为选自0～3的整数。
本申请中正极复合材料中添加适量的由上述A aM b(PO 4) cX d表示的化合物。在所添加的上述化合物的放电曲线中，在较低电压范围可以观察到可逆充放电平台。当在电池正极复合材料中适量混合此类化合物后，相应地将较低电压水平的电压平台引入到电池的整个放电电压分布曲线中。
例如，当化合物中的M为变价元素V时，在0.33C放电的放电曲线中，在1.5～2.1V电压范围内显示出可逆充放电平台。对于在正极复合材料中包含该化合物的电池，由于该化合物的存在，在电池的放电曲线中，在放电末期在1.5～2.1V电压区间引入较低的可逆充放电平台。同理，当M为变价元素Mn时，在电池放电曲线中可逆充放电平台范围为2.3～3.0V。当M同时包括V和Mn时，相应地具有多个可逆充放电平台。
在低温条件下，在电池的放电末期(即电池低荷电状态下)，当电池的放电电压分布曲线达到正极活性材料自身的较高电压平台的末端且然后迅速下降时，基于上述添加剂的 存在而引入的较低电压的平台，能够减缓放电末期的电压下降趋势，使电池电压不致于急剧降低至截止电压而导致放电截止，并且有利于在电池放电时在低荷电状态下越过功率峰值，从而在CLTC工况标准的1800s测试时间内，在电池放电末期可以越过功率峰值而多运行1个或更多个CLTC工况，从而能够提高电池在低温条件下的最大功率、放电容量以及放电容量保持率。
在一些实施方式中，优选地，在放电倍率为0.33C时，正极复合材料可在3.0V以下的电压范围内具有可逆的充放电平台。
在一些实施方式中，优选地，相对于总计100重量％的正极活性物质和由A aM b(PO 4) cX d表示的化合物，由A aM b(PO 4) cX d表示的化合物的含量为3重量％～10重量％。如果由A aM b(PO 4) cX d表示的化合物的含量少于3重量％，由于含量过低，在电池低荷电状态下可能不能观察到明显的可逆充放电平台，从而无法起到在放电末期缓解电压急剧下降趋势的作用。如果由A aM b(PO 4) cX d表示的化合物的含量大于10重量％，则由于相应地减少了正极活性物质的含量而可能降低电池的整体容量。
在一些实施方式中，优选地，由A aM b(PO 4) cX d表示的化合物选自Li 3V 2(PO 4) 3、Na 3V 2(PO 4) 3、K 3V 2(PO 4) 3、Li 3V(PO 4) 2、Na 3V(PO 4) 2、K 3V(PO 4) 2、LiMnPO 4、NaMnPO 4、KMnPO 4、Li 2VMn 2(PO 4) 3、Na 2VMn 2(PO 4) 3、K 2VMn 2(PO 4) 3、LiVMn(PO 4) 2、NaVMn(PO 4) 2、KVMn(PO 4) 2、LiVPO 4F、CaV 4(PO 4) 6、NaVPO 4F、KVPO 4F中的至少一种。
本申请的第二方面涉及锂离子二次电池正极，其包括：正极集流体和设置于正极集流体的至少一个表面上的包含上述正极复合材料的正极膜片。
本申请的第三方面涉及锂离子二次电池，其包括本申请第二方面的锂离子二次电池正极。
根据本申请的锂离子二次电池的构造和制备方法本身是公知的。通常，锂离子二次电池包括外包装袋以及设置在外包装袋内的电芯和电解液，所述电芯包括正极极片、负极极片和隔离膜。在根据本申请的锂离子二次电池中，隔离膜以及电解质的具体种类及组成均不受到具体的限制，可根据实际需求进行选择。具体地，所述隔离膜可选自聚乙烯膜、聚丙烯膜、聚偏氟乙烯膜以及它们的多层复合膜。
对于本申请的锂离子二次电池，非水电解液通常使用在有机溶剂中溶解的锂盐溶液。锂盐例如是LiClO 4、LiPF 6、LiBF 4、LiAsF 6、LiSbF 6等无机锂盐、或者LiCF 3SO 3、LiCF 3CO 2、Li 2C 2F 4(SO 3) 2、LiN(CF 3SO 2) 2、LiC(CF 3SO 2) 3、LiC nF 2n+1SO 3(n≥2)等有机锂盐。非水电解液中使用的有机溶剂例如是碳酸亚乙酯、碳酸亚丙酯、碳酸亚丁酯、碳酸亚乙烯酯等环状碳 酸酯，碳酸二甲酯、碳酸二乙酯、碳酸甲基乙酯等链状碳酸酯，丙酸甲酯等链状酯，γ-丁内酯等环状酯，二甲氧基乙烷、二乙醚、二甘醇二甲醚、三甘醇二甲醚等链状醚，四氢呋喃、2-甲基四氢呋喃等环状醚，乙腈、丙腈等腈类，或者这些溶剂的混合物。
以下对本申请的锂离子二次电池进行简要说明。
首先，按照本领域常规方法制备正极极片。通常，在上述正极活性物质中，需要添加导电剂(例如Super P等)、粘结剂(例如PVDF)等。视需要，也可以添加其他添加剂。通常将这些材料混合在一起分散于溶剂(例如NMP)中，搅拌均匀后均匀涂覆在正极集流体上，烘干后即得到正极极片。可以使用铝箔等金属箔或多孔金属板等材料作为正极集流体。优选使用铝箔。
本申请的负极极片可以采用本领域的公知方法进行制备。通常，将负极活性材料以及可选的导电剂(例如Super P等)、粘结剂(例如SBR等)、其他可选添加剂等材料混合在一起分散于溶剂(例如去离子水)中，搅拌均匀后均匀涂覆在负极集流体上，烘干后即得到含有负极膜层的负极极片。可以使用铜箔等金属箔或多孔金属板等材料作为负极集流体。优选使用铜箔。
在上述正负极极片中，正负极膜层中活性物质的占比不宜过低，否则会导致容量过低；活性物质的占比也不宜过高，否则会导致导电剂和粘结剂减少，极片导电性和与集流体的粘合程度降低，进而导致电芯电性能下降。
在制备正负极极片时，集流体可以双面涂布也可以单面涂布。
最后，将正极膜层、隔离膜、负极膜层按顺序叠好，使隔离膜处于正负极膜层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，获得锂离子二次电池。
本申请的其他方面涉及电池模块、电池包和用电装置。本申请的锂离子二次电池可以组成电池模块，电池模块可以组成电池包。用电装置包括本申请提供的锂离子二次电池、电池模块、电池包中的至少一种。锂离子二次电池、电池模块或电池包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(例如手机、平板电脑、笔记本电脑等)、电动车辆(例如纯电动车、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)、电气列车、船舶及卫星、储能系统等，但不限于此。
【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。实施例中未注明具体技术或条件的，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。本说明书中涉及的各种参数具有本领域公知的通用含义，可以按本领域公知的方法进行测量。例如，可以按照在本申请的实施例中给出的方法进行测试。
在本申请的实施例中，按照常规方式制备正极极片，正极极片包括正极复合材料、导电碳和粘结剂。正极复合材料包括正极活性物质和添加剂，正极活性物质为磷酸铁锂材料和镍钴锰酸锂材料中的至少一种，添加剂为由A aM b(PO 4) cX d表示的化合物中的一种或多种，相对于总计100重量％的正极活性物质和由A aM b(PO 4) cX d表示的化合物，该添加剂的含量为3～10重量％。正极活性物质占正极涂布总质量的85％，压实密度为2.4g/cm 3。采用常规石墨负极极片作为负极，采用常规电解液(将1mol/L LiPF 6溶解于有机溶剂(EC/DMC/EMC＝1/1/1(质量比))中)和隔离膜(厚度为14μm的聚乙烯膜)，按照常规的方法制备和组装卷绕结构的锂离子二次电池。
实施例1：
正极活性物质为LiFePO 4、添加剂为Li 3V 2(PO 4) 3。相对于两者的总重量，LiFePO 4的含量为97％，Li 3V 2(PO 4) 3的含量为3％。
实施例2：
正极活性物质为LiFePO 4、添加剂为Li 3V 2(PO 4) 3。相对于两者的总重量，LiFePO 4的含量为95％，Li 3V 2(PO 4) 3的含量为5％。
实施例3：
正极活性物质为LiFePO 4、添加剂为Li 3V 2(PO 4) 3。相对于两者的总重量，LiFePO 4的含量为90％，Li 3V 2(PO 4) 3的含量为10％。
实施例4：
正极活性物质为LiFePO 4、添加剂为Li 3V 2(PO 4) 3。相对于两者的总重量，LiFePO 4的含量为98％，Li 3V 2(PO 4) 3的含量为2％。
实施例5：
正极活性物质为LiFePO 4、添加剂为Li 3V 2(PO 4) 3。相对于两者的总重量，LiFePO 4的含量为88％，Li 3V 2(PO 4) 3的含量为12％。
实施例6：
正极活性物质为LiFePO 4、添加剂为LiMnPO 4。相对于两者的总重量，LiFePO 4的含量为95％，LiMnPO 4的含量为5％。
实施例7：
正极活性物质为LiFePO 4、添加剂为KVMn(PO 4) 2。相对于两者的总重量，LiFePO 4的含量为95％，KVMn(PO 4) 2的含量为5％。
实施例8：
正极活性物质为LiFePO 4、添加剂为NaVPO 4F。相对于两者的总重量，LiFePO 4的含量为95％，NaVPO 4F的含量为5％。
实施例9：
正极活性物质为LiFePO 4、添加剂为CaV 4(PO 4) 6。相对于两者的总重量，LiFePO 4的含量为95％，CaV 4(PO 4) 6的含量为5％。
实施例10：
正极活性物质为LiNi 0.65Co 0.07Mn 0.37O 2、添加剂为Li 3V 2(PO 4) 3。相对于两者的总重量，LiNi 0.65Co 0.07Mn 0.37O 2的含量为95％，Li 3V 2(PO 4) 3的含量为5％。
实施例11：
正极活性物质为LiNi 0.65Co 0.07Mn 0.37O 2、添加剂为NaMnPO 4。相对于两者的总重量，LiNi 0.65Co 0.07Mn 0.37O 2的含量为95％，NaMnPO 4的含量为5％。
实施例12：
正极活性物质为LiNi 0.65Co 0.07Mn 0.37O 2、添加剂为Li 2VMn 2(PO 4) 3。相对于两者的总重量，LiNi 0.65Co 0.07Mn 0.37O 2的含量为95％，Li 2VMn 2(PO 4) 3的含量为5％。
实施例13：
正极活性物质为LiNi 0.65Co 0.07Mn 0.37O 2、添加剂为KVPO 4F。相对于两者的总重量，LiNi 0.65Co 0.07Mn 0.37O 2的含量为95％，KVPO 4F的含量为5％。
实施例14：
正极活性物质为LiNi 0.65Co 0.07Mn 0.37O 2、添加剂为CaV 4(PO 4) 6。相对于两者的总重量，LiNi 0.65Co 0.07Mn 0.37O 2的含量为95％，CaV 4(PO 4) 6的含量为5％。
实施例15：
正极活性物质为重量配比1:1的LiFePO 4与LiNi 0.65Co 0.07Mn 0.37O 2的混合物，添加剂为Li 3V 2(PO 4) 3。相对于两者的总重量，LiFePO 4与LiNi 0.65Co 0.07Mn 0.37O 2的混合物的含量为95％， Li 3V 2(PO 4) 3的含量为5％。
对比例1：
正极活性物质为LiFePO 4，正极材料中不含添加剂。
对比例2：
正极活性物质为LiNi 0.65Co 0.07Mn 0.37O 2，正极材料中不含添加剂。
【锂离子二次电池电芯性能测试和低温性能测试】
对实施例1-15和对比例1-2的电池电芯进行测试，并测试相应的低温性能，测试方法如下。
(1)电芯性能测试：
25℃下电池容量测试如下：将电池置于25℃环境下静置至电池温度为25℃恒定；以1/3C的电流充电到充电终止电压(正极活性物质为LiFePO 4时为3.65V；正极活性物质为LiNi 0.65Co 0.07Mn 0.37O 2或LiFePO 4和LiNi 0.65Co 0.07Mn 0.37O 2的混合物时为4.35V)；静置10分钟；以0.05C的电流充电到充电终止电压；静置10分钟；以1/3C的电流放电到放电终止电压，记录此步放电容量作为25℃@0.33C的电池放电容量Cn。
确定平台电压如下：根据放电数据得到放电曲线，从曲线观察判定添加剂在对应实施例/对比例中的磷酸铁锂或镍钴锰酸锂体系中显示的平台电压。
(2)低温性能测试：
20％SOC 30s最大功率@-7℃测试如下：①将电池置于25℃环境下静置至电池温度为25℃恒定；②以1/3C的电流充电到充电终止电压；③静置10分钟；④以0.05C的电流充电到充电终止电压；⑤静置10分钟；⑥以1/3C的电流放电0.8Cn，调节电池在20％SOC荷电状态；⑦将电池置于-7℃环境下静置至电池温度为-7℃恒定；⑧以特定功率放电30s至放电终止电压，记录此步放电容量为C1；⑨静置5分钟；⑩若第⑧步电压已达放电终止电压，则记录此功率为最大功率；若未达放电终止电压，或者达到放电终止电压时间小于30s，则以0.05C的电流充电与放电容量C1相同的容量，即重新调节电池在20％SOC荷电状态；相应增大/减小功率后重复第⑧步放电，至电池在30s时放电至放电截止电压，记录此时功率为最大功率。
-7℃电芯CLTC实际放电容量测试如下：将电池置于25℃环境下静置至电池温度为25℃恒定；以1/3C的电流充电到充电终止电压；静置10分钟；以0.05C的电流充电到充电终止电压；静置10分钟；电池置于-7℃环境下静置至电池温度为-7℃恒定；以电芯CLTC工 况流程放电到放电终止电压，记录此步放电容量作为电池的-7℃实际放电容量。
-7℃电芯CLTC放电容量保持率计算：(-7℃ CLTC实际放电容量/Ah)除以(25℃放电容量/Ah@0.33C)得到电芯在-7℃CLTC放电容量保持率。
【测试结果分析】
实施例1～15和对比例1～2的测试结果如表1所示。
参见表1，从实施例1-15和对比例1-2的性能测试结果可以看出，在放电曲线上可以观察到包含变价元素(V和/或Mn)的添加剂所显示的电压平台，它们的电压平台包括3.0V以下的电压平台，即较低电压的平台。
从磷酸铁锂体系电池的实施例1～3、5-9与对比例1的对比可以看出，与不包含添加剂的对比例1相比，实施例1～3、5-9虽然由于添加剂取代了对应含量的正极活性物质LiFePO4，而相应地减少了常温(25℃)下的放电容量，但是由于添加剂的存在，明显地提高了电池在低温环境下(-7℃)，低荷电状态(20％SOC)下的最大功率、CLTC工况下的实际放电容量以及放电容量保持率。
同样的，从镍钴锰酸锂体系电池的实施例10～14与对比例2的对比也可以看出，添加剂的使用明显地提高了电池在低温环境下(-7℃)，低荷电状态(20％SOC)下的最大功率、CLTC工况下的实际放电容量和放电容量保持率。
另外，从实施例15可以看出，正极活性材料可以为磷酸铁锂和镍钴锰酸锂混合体系，相对于不包含添加剂的对比例1和对比例2，基于添加剂的存在，同样提高了电池的低温性能。
进一步比较实施例1～5可以看出，当正极复合材料中添加剂的含量为2重量％时(实施例4)，虽然由于含有相对较多的正极活性材料(98重量％)，使得常温(25℃)下的放电容量相对较高；但是，由于添加剂含量较低，在低温环境下(-7℃)，低荷电状态(20％SOC)下的最大功率、CLTC工况下的实际放电容量和放电容量保持率，相比于添加剂含量为3～10重量％的实施例1～3的性能差一些，因此，2重量％的添加剂含量是不优选的。
当正极复合材料中添加剂的含量为12重量％时(实施例5)，可以看出添加剂的存在起到了提高低温环境下(-7℃)，低荷电状态(20％SOC)下最大功率、CLTC工况下实际放电容量和放电容量保持率的效果；然而，由于添加剂含量较高，相对而言，正极活性材料的含量减少(88重量％)，使得常温(25℃)下的放电容量降低，因此，12重量％的添加剂含量也是不优选的。
本申请中添加剂的优选的含量范围是3～10重量％。参见实施例1～3，其中既能改善低 温环境下低荷电状态下的功率特性，提高CLTC工况下的实际放电容量和放电容量保持率，又不会降低电池常温下的放电容量。
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。
Figure PCTCN2021139283-appb-000001

Claims (11)

  1. 一种锂离子二次电池用正极复合材料，其特征在于，所述正极复合材料包括：
    正极活性物质，其选自磷酸铁锂材料和镍钴锰酸锂材料中的至少一种；和
    由A aM b(PO 4) cX d表示的化合物中的至少一种，
    其中，A选自Li、Na、K和Ca中的至少一种，M选自V和Mn中的至少一种，X选自卤族元素中的任一种，并且a、b、c各自独立地选自1～6的整数，d为选自0～3的整数。
  2. 根据权利要求1所述的正极复合材料，其特征在于，在锂离子二次电池的放电倍率为0.33C时，所述正极复合材料在3.0V以下的电压范围内具有可逆充放电平台。
  3. 根据权利要求1或2所述的正极复合材料，其特征在于，以所述正极活性物质和所述由A aM b(PO 4) cX d表示的化合物总计100重量％计，所述由A aM b(PO 4) cX d表示的化合物的含量为3重量％～10重量％。
  4. 根据权利要求1-3中任一项所述的正极复合材料，其特征在于，所述由A aM b(PO 4) cX d表示的化合物选自Li 3V 2(PO 4) 3、Na 3V 2(PO 4) 3、K 3V 2(PO 4) 3、Li 3V(PO 4) 2、Na 3V(PO 4) 2、K 3V(PO 4) 2、LiMnPO 4、NaMnPO 4、KMnPO 4、Li 2VMn 2(PO 4) 3、Na 2VMn 2(PO 4) 3、K 2VMn 2(PO 4) 3、LiVMn(PO 4) 2、NaVMn(PO 4) 2、KVMn(PO 4) 2、LiVPO 4F、CaV 4(PO 4) 6、NaVPO 4F、KVPO 4F中的至少一种。
  5. 根据权利要求1-4中任一项所述的正极复合材料，其特征在于，所述磷酸铁锂材料选自LiFePO 4、掺杂的LiFePO 4、碳包覆的LiFePO 4或碳包覆的掺杂的LiFePO 4中的至少一种。
  6. 根据权利要求1-4中任一项所述的正极复合材料，其特征在于，所述镍钴锰酸锂材料为LiNi mCo nMn 1-m-nO 2，其中0.3≤m≤0.9，0≤n≤0.3。
  7. 一种锂离子二次电池的正极，其特征在于，所述正极包括：
    正极集流体和设置于所述正极集流体的至少一个表面上的包含正极复合材料的正极膜片，所述正极复合材料为根据权利要求1-6中任一项所述的正极复合材料。
  8. 一种锂离子二次电池，其特征在于，包括根据权利要求7所述的锂离子二次电池的正极。
  9. 一种电池模块，其特征在于，包括根据权利要求8所述的锂离子二次电池。
  10. 一种电池包，其特征在于，包括根据权利要求9所述的电池模块。
  11. 一种用电装置，其特征在于，包括根据权利要求8所述的锂离子二次电池、根据权利要求9所述的电池模块和根据权利要求10所述的电池包中的至少一种。
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