WO2020098571A1 - 负极极片及锂离子二次电池 - Google Patents

负极极片及锂离子二次电池 Download PDF

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WO2020098571A1
WO2020098571A1 PCT/CN2019/116601 CN2019116601W WO2020098571A1 WO 2020098571 A1 WO2020098571 A1 WO 2020098571A1 CN 2019116601 W CN2019116601 W CN 2019116601W WO 2020098571 A1 WO2020098571 A1 WO 2020098571A1
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negative electrode
active material
electrode active
secondary battery
ion secondary
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PCT/CN2019/116601
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English (en)
French (fr)
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李志强
韩昌隆
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宁德时代新能源科技股份有限公司
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Publication of WO2020098571A1 publication Critical patent/WO2020098571A1/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
    • H01M4/133—Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • 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
    • 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
    • H01M10/056—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
    • 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
    • H01M4/36—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
    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
    • 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
    • H01M2004/021—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
    • 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
    • H01M2004/027—Negative electrodes
    • 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
    • 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
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2300/00—Electrolytes
    • H01M2300/0017—Non-aqueous electrolytes
    • H01M2300/0025—Organic electrolyte
    • 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 belongs to the technical field of batteries, and specifically relates to a negative pole piece and a lithium ion secondary battery.
  • Lithium ion secondary batteries can provide stable voltage and current, have a high voltage platform, high energy density and a wide temperature range, no memory effect, and are environmentally friendly, easy to carry, occupying the core position of power batteries.
  • the present application provides a negative electrode tab and a lithium ion secondary battery that can solve the problem of deterioration of battery cycle performance due to positive electrode manganese dissolution.
  • a first aspect of the present application provides a negative pole piece.
  • the negative pole piece 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.
  • the negative electrode active material layer includes graphite material;
  • the ratio r between the intensity of the 004 crystal plane diffraction peak of the negative electrode active material layer and the 110 crystal plane diffraction peak, the porosity s of the negative electrode active material layer, and the specific resistance of the negative electrode sheet satisfy the formula (1),
  • the unit of t is ⁇ ⁇ m.
  • a second aspect of the present application provides a lithium ion secondary battery.
  • the lithium ion secondary battery includes a positive pole piece, a negative pole piece, a separator, and an electrolyte.
  • the positive pole piece includes a manganese-containing positive active material, and the negative pole piece is The negative pole piece of the first aspect of the present application.
  • the negative electrode tab according to the present application can solve the problem that the manganese elution of the positive electrode deteriorates the cycle performance of the lithium ion secondary battery, thereby obtaining a lithium ion secondary battery having higher cycle performance.
  • the negative electrode active material includes graphite material, and the intensity ratio r of the 004 crystal plane diffraction peak to the 110 crystal plane diffraction peak of the negative electrode active material layer, the porosity s of the negative electrode active material layer, and the negative electrode The resistivity t of the pole piece satisfies the above formula (1).
  • the negative pole piece can block the manganese in the electrolyte outside the negative electrode active material layer, effectively prevent manganese from entering the negative electrode active material layer, and at the same time can reduce the deposition of manganese in the negative electrode, thereby effectively suppressing the manganese to the negative electrode Of destruction.
  • This can improve the stability of the negative electrode and reduce the capacity loss of the negative electrode during the cycle, thereby improving the capacity retention rate of the lithium ion secondary battery during the cycle and making the lithium ion secondary battery have higher cycle performance.
  • the negative electrode sheet satisfying the above formula (1) of the present application can also ensure that the negative electrode active material layer has higher kinetic performance of delithiation and lithium insertion, so that the lithium ion secondary battery has higher rate performance.
  • any lower limit can be combined with any upper limit to form an unspecified range; and any lower limit can be combined with other lower limits to form an unspecified range, and likewise any upper limit can be combined with any other upper limit to form an unspecified range.
  • every point or single value between the end points of the range is included in the range.
  • each point or single numerical value may be combined with any other point or single numerical value as its own lower limit or upper limit or with other lower or upper limits to form an unspecified range.
  • the first aspect of the present application provides a negative pole piece.
  • the negative electrode tab includes a negative electrode current collector and a negative electrode active material layer provided on at least one surface of the negative electrode current collector.
  • the negative electrode current collector includes two opposing surfaces in its thickness direction, and the negative electrode active material layer is stacked on any one or both of the two surfaces of the negative electrode current collector.
  • the negative electrode active material layer contains a negative electrode active material.
  • the negative electrode active material can perform reversible deintercalation / intercalation of lithium ions during the work process to ensure the normal progress of the electrochemical process.
  • the negative electrode active material includes graphite material; and the ratio of the intensity r of the 004 crystal plane diffraction peak to the 110 crystal plane diffraction peak of the negative electrode active material layer, the porosity s of the negative pole piece, and the resistivity t of the negative pole piece satisfy the formula (1):
  • the unit of t is ⁇ ⁇ m.
  • the ratio of the intensity of the 004 crystal plane diffraction peak to the 110 crystal plane diffraction peak of the negative electrode active material layer, the porosity of the negative electrode active material layer, and the specific resistance of the negative electrode sheet are all well-known in the art.
  • the ratio r of the intensity of the 004 crystal plane diffraction peak to the 110 crystal plane diffraction peak of the negative electrode active material layer indicates the degree of anisotropy of the crystal grain arrangement in the negative electrode active material layer .
  • the porosity s of the negative electrode active material layer represents the percentage of the pore volume in the negative electrode active material layer to the total volume of the negative electrode active material layer.
  • the specific resistance t of the negative pole piece represents the resistance characteristic of the negative pole piece.
  • a Japanese-built BT3562 internal resistance tester is used to clamp the upper and lower sides of the negative pole piece between the two conductive terminals of the internal resistance tester, and apply a certain pressure to fix it to test the resistance R of the negative pole piece
  • the applied pressure is 15 MPa to 27 MPa
  • the range of the sampling time is 5 s to 17 s.
  • the calculation of formula (1) only involves numerical calculations.
  • the ratio r of the intensity of the 004 crystal plane diffraction peak of the negative electrode active material layer to the 110 crystal plane diffraction peak is 50, and the pores of the negative electrode active material layer The rate s is 25%, and the resistivity t of the negative pole piece is 10 ⁇ ⁇ m, then,
  • the negative electrode active material includes graphite material, and the intensity ratio r of the 004 crystal plane diffraction peak to the 110 crystal plane diffraction peak of the negative electrode active material layer, the porosity s of the negative electrode active material layer, and the negative electrode
  • the resistivity t of the pole piece satisfies the above formula (1). Surprisingly, it was found that the negative pole piece can block the manganese in the electrolyte outside the negative electrode active material layer, effectively prevent manganese from entering the negative electrode active material layer, and at the same time reduce the deposition of manganese in the negative electrode, thereby reducing manganese ions and negative electrode Lithium ion exchange occurs.
  • the negative electrode sheet satisfying the above relationship (1) can also ensure that the negative electrode active material layer has high kinetic performance of delithiation and lithium insertion, thereby making the lithium ion secondary battery have higher rate performance.
  • K may be 0.05 or more, 0.1 or more, 0.15 or more, 0.2 or more, 0.5 or more, 1 or more; and K may be 10 or less, 8 or less, 6 or less, 5 or less, 3 or less, 2 or less, 1 or less. In some embodiments, 0.1 ⁇ K ⁇ 5. In other embodiments, 0.1 ⁇ K ⁇ 3. In other embodiments, 0.2 ⁇ K ⁇ 1.
  • the K value indicates that the r, s, and t of the negative pole piece satisfy an appropriate relationship, and the negative pole piece can better exert the above effect.
  • the ratio r of the intensity of the 004 crystal plane diffraction peak to the 110 crystal plane diffraction peak of the negative electrode active material layer may be 1-50, such as 4-35, or 6-20. This can further reduce the deposition of manganese on the negative electrode, and at the same time ensure that the negative electrode active material layer has a high kinetic performance of lithium removal and lithium insertion.
  • the porosity s of the negative electrode active material layer may be 10% to 60%, such as 15% to 50%, or 25% to 35%.
  • the anode active material layer has a porosity suitable for sufficient infiltration of the electrolyte, and can further reduce the deposition of manganese on the anode, and ensure that the anode active material layer has high kinetic performance of delithiation and lithium insertion.
  • the compacted density of the negative electrode active material layer is preferably 1.5 g / cm 3 to 1.75 g / cm 3 , such as 1.55 g / cm 3 to 1.65 g / cm 3 .
  • the negative electrode active material layer has a porosity suitable for sufficient infiltration of the electrolyte, and also makes the diffusion rate of manganese ions in the negative electrode active material layer low, thereby further reducing the ion exchange effect of manganese ions and lithium in the negative electrode. Inhibit the destruction of manganese on the negative electrode and improve the stability of the negative electrode.
  • the negative electrode active material layer has a porosity s of 15% to 40%, and the negative electrode active material layer has a compact density of 1.55 g / cm 3 to 1.7 g / cm 3 .
  • the negative electrode active material layer is suitable for fully infiltrating the electrolyte to meet the battery dynamic performance requirements, and can further reduce the damage of manganese to the negative electrode and improve the stability of the negative electrode.
  • the specific resistance t of the negative pole piece may be 5 ⁇ ⁇ m to 100 ⁇ ⁇ m, such as 5 ⁇ ⁇ m to 40 ⁇ ⁇ m. This is helpful to reduce the deposition of manganese on the negative electrode, and to ensure the above-mentioned effects of the negative pole piece. At the same time, making the negative pole piece have a lower resistivity is beneficial to reduce the overall impedance of the lithium ion secondary battery, so that the lithium ion secondary battery has higher dynamic performance and rate performance.
  • the emphasis is on the intensity ratio r of the 004 crystal plane diffraction peak to the 110 crystal plane diffraction peak of the negative electrode active material layer, the porosity s of the negative electrode active material layer, and the resistivity t of the negative electrode sheet Reasonable matching, so that they meet the above formula (1), so as to achieve the above technical effects.
  • the graphite material in the negative electrode active material may be one or more of artificial graphite and natural graphite.
  • the negative electrode active material may further include mesophase microcarbon balls (MCMB), hard carbon, soft carbon, silicon, silicon-carbon composite, SiO, Li-Sn alloy, Li-Sn-O alloy, Sn , SnO, SnO 2 , spinel-structured lithium titanate Li 4 Ti 5 O 12 , Li-Al alloy and one or more of lithium metal.
  • MCMB mesophase microcarbon balls
  • the mass percentage content of the graphite material in the negative electrode active material is more than 50wt%, such as more than 55wt%, more than 60wt%, more than 65wt%, more than 70wt%, more than 75wt%, more than 80wt%, more than 85wt% , More than 90wt%, more than 95wt%.
  • the negative active material layer may further include a conductive agent and a binder.
  • a conductive agent may be selected from one or more of graphite, superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers
  • the binder may be selected From styrene-butadiene rubber (SBR), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyvinyl butyral (PVB), water-based acrylic resin (water-based acrylic resin) and carboxymethyl fiber One or more of the prime (CMC).
  • SBR styrene-butadiene rubber
  • PVDF polyvinylidene fluoride
  • PTFE polytetrafluoroethylene
  • PVB polyvinyl butyral
  • water-based acrylic resin water-based acrylic resin
  • carboxymethyl fiber One or more of the prime (CMC).
  • the negative active material layer optionally further includes a thickener, such as carboxymethyl cellulose (CMC).
  • a thickener such as carboxymethyl cellulose (CMC).
  • the negative current collector collects and conducts current.
  • a metal foil material or a porous metal plate can be used, for example, a foil material or a porous plate using a metal such as copper, nickel, titanium or iron, or an alloy thereof, such as copper foil.
  • the negative electrode tab can be prepared according to conventional methods in the art. Generally, the negative electrode active material and optional conductive agent, binder and thickener are dispersed in a solvent.
  • the solvent can be N-methylpyrrolidone (NMP) or deionized water to form a uniform negative electrode slurry; The material is coated on the negative electrode current collector, and after drying, cold pressing and other processes, the negative electrode sheet is prepared.
  • a second aspect of the present application provides a lithium ion secondary battery, including a positive pole piece, a negative pole piece, a separator, and an electrolyte, wherein the negative pole piece is any negative pole piece provided in the first aspect of the present application.
  • the lithium ion secondary battery of the embodiment of the present application can have higher cycle performance while having higher rate performance.
  • the positive electrode tab includes a positive electrode current collector and a positive electrode active material layer provided on at least one surface of the positive electrode current collector.
  • the positive electrode current collector includes two opposite surfaces in its thickness direction, and the positive electrode active material layer is stacked on any one or both of the two surfaces of the positive electrode current collector.
  • the positive electrode active material layer contains a positive electrode active material.
  • the positive electrode active material can perform reversible deintercalation / intercalation of lithium ions during the working process.
  • the positive electrode active material is preferably a manganese-containing positive electrode active material, such as LiMn 2 O 4 , LiNi m Co n Mn 1-mn O 2 (0 ⁇ m ⁇ 1, 0 ⁇ n ⁇ 1, 0 ⁇ m + n ⁇ 1), and the like.
  • the manganese-containing positive electrode active material has high structural stability, and its oxidation activity on the electrolyte is low, which can reduce the side reaction of the electrolyte on the surface of the positive electrode active material, suppress gas production, and reduce heat production. This can reduce the risk of the lithium ion secondary battery getting out of control and make the lithium ion secondary battery have higher safety performance.
  • the positive electrode active material may include a first positive electrode active material and a second positive electrode active material.
  • the first positive electrode active material is a compound represented by chemical formula (1),
  • M is Mn, Fe, Cr, Ti, Zn , V, Al, Zr, and Ce, one or more, A includes S, N, F, Cl, Br, and I.
  • the second positive electrode active material is a compound represented by chemical formula (2),
  • M 'in includes one of Ni, Fe, Cr, Ti, Zn, V, Al, Mg, Zr, and Ce
  • a 'in includes one or more of S, N, F, Cl, Br and I.
  • the positive electrode active material includes a first positive electrode active material and a second positive electrode active material.
  • the positive electrode active material has higher voltage platform and energy density, and higher structural stability, can withstand more severe structural destructive force, and no oxygen release occurs, so it can effectively reduce thermal runaway caused by material structural damage.
  • the positive electrode active material has low oxidation activity on the electrolyte, which can reduce the side reaction of the electrolyte on the surface of the positive electrode active material, suppress gas generation, reduce heat generation, and effectively improve the safety performance of the lithium ion secondary battery.
  • the use of the positive electrode active material can also reduce the positive electrode polarization phenomenon, reduce the capacity loss due to polarization, and in particular, reduce the elution of manganese ions in the positive electrode active material, thereby increasing the capacity of the lithium ion secondary battery during cycling The retention rate makes the lithium ion secondary battery have higher cycle performance.
  • the use of the positive electrode active material including the first positive electrode active material and the second positive electrode active material, together with the negative electrode tab of the first aspect of the embodiment of the present application can make the lithium ion secondary battery have a higher voltage platform and energy Density, while taking into account the higher safety performance, cycle performance and rate performance.
  • M is one or both of Mn and Al
  • A is one or two of S or F. This can further increase the energy density of the lithium ion secondary battery.
  • the mass ratio of the first positive electrode active material to the second positive electrode active material in the positive electrode active material is from 3: 7 to 99.5: 0.5, preferably from 35:65 to 95: 5.
  • the compacted density of the positive electrode active material layer is preferably from 3.1 g / cm 3 to 3.65 g / cm 3 . This makes the porosity inside the positive electrode active material layer lower under a certain thickness of the positive electrode sheet, which is beneficial to reduce the dissolution rate of Mn in the positive electrode active material, thereby improving the cycle performance of the battery.
  • the positive electrode active material layer also enables the battery to have a higher reversible capacity.
  • the positive electrode active material layer may further include a conductive agent and a binder.
  • a conductive agent may be selected from one or more of graphite, superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers
  • the binder may be selected from SBR, water-based acrylic, carboxymethyl cellulose (CMC), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyvinyl butyral One or more of (PVB), ethylene-vinyl acetate copolymer (EVA) and polyvinyl alcohol (PVA).
  • the mass ratio of the conductive agent in the positive electrode active material layer to the positive electrode active material is greater than or equal to 1.5: 95.5, and the weight percentage of the binder in the positive electrode active material layer is less than or equal to 2 wt%.
  • the positive electrode current collector collects and conducts current.
  • the positive electrode current collector may use a metal foil or a porous metal plate, for example, a foil or porous plate using a metal such as aluminum, copper, nickel, titanium, or silver, or an alloy thereof, such as aluminum foil.
  • the positive pole piece can be prepared by coating. For example, first mix the positive electrode active material, binder, conductive agent and organic solvent in a predetermined ratio.
  • the organic solvent may be N-methylpyrrolidone (NMP). Stir the mixture to a uniform system to obtain a positive electrode slurry; The slurry is coated on the positive electrode current collector, and after drying, rolling and other processes, the positive electrode sheet is prepared.
  • NMP N-methylpyrrolidone
  • the electrolyte plays a role in transferring lithium ions between the positive and negative poles of the battery.
  • the electrolyte includes a lithium salt and a solvent.
  • the lithium salt in the electrolyte is selected from LiPF 6 (lithium hexafluorophosphate), LiBF 4 (lithium tetrafluoroborate), LiClO 4 (lithium perchlorate), LiAsF 6 (lithium hexafluoroarsenate), LiFSI (bifluoro Lithium sulfonimide), LiTFSI (lithium bistrifluoromethanesulfonimide), LiTFS (lithium trifluoromethanesulfonate), LiDFOB (lithium difluorooxalate borate), LiBOB (lithium bisoxalate borate), LiPO 2 F
  • LiPF 6 lithium hexafluorophosphate
  • LiBF 4 lithium tetrafluoroborate
  • LiClO 4 lithium perchlorate
  • LiAsF 6 lithium hexafluoroarsenate
  • LiFSI bifluoro Lithium sulfonimide
  • LiTFSI lithium
  • the solvent in the electrolyte is a non-aqueous organic solvent, such as 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), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), acetic acid
  • EC ethylene carbonate
  • PC propylene carbonate
  • EMC diethyl carbonate
  • DMC dimethyl carbonate
  • DPC dipropyl carbonate
  • MPC methyl propyl carbonate
  • MPC methyl propyl carbonate
  • EPC ethyl propyl carbonate
  • EPC ethyl propyl carbonate
  • the electrolyte further contains a manganese ion complex additive.
  • the manganese ion complex additive is preferably or includes a chain nitrile compound.
  • Manganese ion complex additives especially the use of chain nitrile manganese ion complex additives, can passivate manganese in the positive electrode active material, effectively reduce the dissolution of manganese ions, reduce the structural damage of the positive electrode active material, and reduce manganese on the negative electrode Deposition, thereby improving the cycling performance of lithium ion secondary batteries.
  • the manganese ion complex additive includes one or more of adiponitrile (ADN), succinonitrile (SN), glutaronitrile (GN) and hexanetrinitrile (HTN).
  • ADN adiponitrile
  • SN succinonitrile
  • GN glutaronitrile
  • HTN hexanetrinitrile
  • the mass percentage content of the manganese ion complexing additive in the electrolyte is preferably 0.1 wt% to 4 wt%.
  • the electrolyte further contains a negative electrode film-forming additive.
  • the negative electrode film-forming additive preferably includes an unsaturated bond-containing cyclic carbonate, a fluorine-containing cyclic carbonate, a cyclic sulfonate, and a cyclic sulfate.
  • the negative electrode film-forming additive can form an interface film with good lithium ion transmission properties and mechanical properties on the negative electrode to strengthen the protection of the negative electrode.
  • the interface film can also effectively prevent the intercalation reaction of the manganese ion complex additive at the negative electrode, prevent the addition of the manganese ion complex additive to cause damage to the negative electrode interface, and improve the stability of the negative electrode. Therefore, the inclusion of the negative electrode film-forming additive in the electrolyte can further improve the cycle performance of the lithium ion secondary battery.
  • the negative electrode film-forming additive includes vinylene carbonate (VC), ethylene ethylene carbonate (VEC), fluoroethylene carbonate (FEC), difluoroethylene carbonate (DFEC), trifluoromethyl carbonate Ethylene glycol (TFPC), methylene methanedisulfonate (MMDS), 1,3-propane sultone (1,3-PS), 1-propene-1,3-sultone (PST) And one or more of ethylene sulfate (DTD).
  • VEC vinylene carbonate
  • VEC ethylene ethylene carbonate
  • FEC fluoroethylene carbonate
  • DFEC difluoroethylene carbonate
  • TFPC trifluoromethyl carbonate
  • MMDS methylene methanedisulfonate
  • PST 1-propene-1,3-sultone
  • DTD ethylene sulfate
  • the mass percentage content of the negative electrode film-forming additive in the electrolyte is preferably 0.1 wt% to 2 wt%.
  • the electrolyte also contains fluorine-containing lithium salt type additives.
  • the fluorine-containing lithium salt type additive can effectively control the increase in impedance due to the enhanced film formation at the interface of the negative electrode, so that the negative electrode pole piece has a lower impedance, and thus the lithium ion secondary battery has a lower internal resistance. This enables the lithium ion secondary battery to have higher cycle performance while taking into account higher kinetic performance and rate performance.
  • the fluorine-containing lithium salt type additive includes one or more of lithium difluorophosphate LiPO 2 F 2 , lithium difluorooxalate LiDFOP, lithium tetrafluoroborate LiBF 4 and lithium difluorooxalate borate LiDFOB.
  • the mass percentage content of the fluorine-containing lithium salt type additive in the electrolyte is preferably 0.05 wt% to 1.5 wt%.
  • lithium difluorophosphate LiPO 2 F 2 , lithium difluorooxalate LiDFOP, lithium tetrafluoroborate LiBF 4 and lithium difluorooxalate borate LiDFOB can be used as both electrolyte lithium salt and fluorine-containing lithium salt type additives.
  • fluorine-containing lithium salt type additive meets a preset amount to ensure that the fluorine-containing lithium salt type additive can effectively control the increase in impedance due to the enhanced film formation at the negative electrode interface.
  • the electrolyte may optionally contain other additives, such as sulfonate cyclic quaternary ammonium salt, tris (trimethylsilane) phosphate (TMSP), tris (trimethylsilane) borate (TMSB) etc.
  • additives such as sulfonate cyclic quaternary ammonium salt, tris (trimethylsilane) phosphate (TMSP), tris (trimethylsilane) borate (TMSB) etc.
  • the lithium-ion secondary battery of the present application has no particular limitation on the separator, and any known porous separator with electrochemical stability and chemical stability can be selected, including, for example, glass fiber, non-woven fabric, and polyethylene (PE) , Polypropylene (PP) and Polyvinylidene Fluoride (PVDF), one or more of single-layer or multi-layer films.
  • any known porous separator with electrochemical stability and chemical stability can be selected, including, for example, glass fiber, non-woven fabric, and polyethylene (PE) , Polypropylene (PP) and Polyvinylidene Fluoride (PVDF), one or more of single-layer or multi-layer films.
  • PE polyethylene
  • PP Polypropylene
  • PVDF Polyvinylidene Fluoride
  • the positive pole pieces and the negative pole pieces are alternately stacked, and a separation film is provided between the positive pole pieces and the negative pole pieces to isolate the positive pole pieces and the negative pole pieces to obtain a battery core, which may also be wound
  • a battery cell is obtained; the battery cell is placed in a case, and an electrolyte is injected to fully infiltrate the electrolyte in the pores of the positive electrode active material layer, the negative electrode active material layer and the separator, and sealed to obtain a lithium ion secondary battery.
  • the total content of Mn element in the negative electrode active material layer does not exceed 1500 ppm.
  • ppm parts per million
  • ppm parts per million
  • the above formula (1 ) which can effectively suppress the deposition of the Mn element in the positive electrode active material in the negative electrode active material layer during the charge and discharge cycle of the battery, so that the negative electrode active material layer maintains a good deintercalation / intercalation channel during the subsequent cycle of the battery. Therefore, the cycle performance of the battery can be improved, and the negative electrode active material layer has high kinetic performance of delithiation and lithium insertion, so that the lithium ion secondary battery has higher rate performance.
  • the material is evenly coated on the positive current collector aluminum foil, and after drying, cold pressing, slitting and cutting, the positive pole piece is obtained.
  • the mass ratio of the first positive electrode active material LiNi 0.8 Co 0.1 Mn 0.1 O 2 and the second positive electrode active material LiMn 2 O 4 is 55:45, and the weight ratio of the positive electrode active material, conductive carbon black and binder PVDF is 96: 2: 2.
  • Negative electrode active material graphite, conductive carbon black, thickener CMC and binder SBR are dispersed in solvent deionized water according to a weight ratio of 96: 1: 1: 2 and mixed evenly to obtain a negative electrode slurry; the negative electrode slurry is evenly coated It is distributed on the copper foil of the negative electrode collector; after drying, cold pressing, slitting and cutting, the negative electrode sheet is obtained.
  • Ethylene carbonate (EC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC) are mixed uniformly in a mass ratio of 30:40:30 to obtain a non-aqueous organic solvent.
  • 1 mol / L LiPF 6 was dissolved in the non-aqueous organic solvent and mixed uniformly to obtain an electrolyte.
  • the positive pole piece, the separator and the negative pole piece are stacked in this order.
  • the separator is made of PP / PE / PP composite film, which is then wound into a battery core and put into a soft package shell. The top side is sealed and the electrolyte is injected. After that, a soft-pack battery is made.
  • Example 2 Different from Example 1, the related parameters of the lithium ion secondary battery are adjusted, as shown in Table 1 for details.
  • the capacity retention rate (%) of the lithium ion secondary battery after 45 cycles at 45 ° C. and 1 C / 1 C cycle discharge capacity at the 400th cycle / discharge capacity at the first cycle ⁇ 100%.
  • the 50% SOC lithium-ion secondary battery was left for 10 minutes, and discharged at a constant current of 4C for 30 seconds. Record the voltage U 1 for the last 1 second, the voltage U 2 for the 4 C rate constant current discharge, and the current I for the 4 C rate constant current discharge.
  • the lithium-ion secondary battery was left for 5 minutes, charged at a constant current of 1C to 4.2V, and then charged at a constant voltage until the current was less than or equal to 0.05C, and then left for 5 minutes. Then, the lithium ion secondary battery was placed in an oven, the oven temperature was set to be increased from 25 ° C to 130 ° C at a temperature increase rate of 2 ° C / min, and the temperature was maintained for 2 hours. Monitor the temperature of the battery surface during the heating process and heat preservation process, and record the maximum surface temperature of the battery.
  • the anode active material layer was digested by a microwave digestion apparatus. Specifically, the above lithium ion secondary battery is disassembled, the negative electrode active material layer scraping powder is taken, the scraped powder is placed in a digestion pot, and the digestion apparatus is started to digest the powder to obtain a negative electrode active material layer digestion solution. The mass of the negative electrode active material layer is recorded as m 1 (g).
  • the content of the manganese ion complexing additive, the content of the negative electrode film-forming additive, and the content of the fluorine-containing lithium salt type additive are all mass percentages in the electrolyte.
  • Comparative analysis of Examples 1 to 12 and Comparative Examples 1 to 2 shows that the positive electrode active material of the lithium ion secondary battery includes the first positive electrode active material and the second positive electrode active material.
  • the battery temperature of the lithium ion secondary battery in the thermal shock test The liter is effectively controlled, which makes the lithium ion secondary battery have higher safety performance.
  • a lithium ion secondary battery having a remaining capacity of 70% of the rated capacity Charged to 4.2V at a constant current of 1C rate, and then discharged to 3.0V at a constant current of 1C rate.
  • the content of manganese element deposited on the negative electrode active material layer was reduced to less than 1500ppm.
  • the content of manganese element deposited on the negative electrode active material layer during the charging and discharging of the battery is significantly reduced, so that the negative electrode active material layer maintains a good lithium removal / intercalation channel during the subsequent cycle of the battery, and improves the cycle performance of the battery.
  • the lithium ion secondary battery is operated at 45 ° C, 1C / 1C
  • the capacity retention rate after 400 charge-discharge cycles was significantly increased, and it can be seen that the cycle performance of the lithium ion secondary battery was significantly improved.
  • the DC resistance of the lithium ion secondary battery at 25 ° C, 50% SOC, 4C rate constant current discharge for 30s is also low, which makes the lithium ion secondary battery have both high dynamic performance and rate performance.
  • the lithium ion secondary battery of the present application can take into account both higher safety performance and cycle performance, and has lower impedance, so it can also have higher dynamic performance and rate performance.

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Abstract

本申请公开了一种负极极片及锂离子二次电池，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活性物质层，负极活性物质层包括石墨材料；其中，负极活性物质层的004晶面衍射峰与110晶面衍射峰的强度之比r、负极活性物质层的孔隙率s及负极极片的电阻率t之间满足：(1) 本申请提供的负极极片及锂离子二次电池能够同时兼顾较高的安全性能、循环性能及倍率性能。

Description

负极极片及锂离子二次电池
相关申请的交叉引用
本申请要求享有于2018年11月12日提交的名称为“负极极片及锂离子二次电池”的中国专利申请201811337700.4的优先权，该申请的全部内容通过引用并入本文中。
技术领域
本申请属于电池技术领域，具体涉及一种负极极片及锂离子二次电池。
背景技术
锂离子二次电池能够提供稳定的电压和电流，具有高电压平台、高能量密度及宽广的温度使用范围，无记忆效应，并且环境友好、携带方便，占据动力电池的核心地位。
锂离子二次电池采用含锰正极活性物质时，由于正极中的锰容易发生歧化反应，生成的锰离子溶于电解液中，迁移并沉积到负极。锰离子会与负极中的锂发生离子交换作用，占据负极嵌锂位置，并且离子交换脱出的锂将不能再参与电化学反应，造成不可逆容量损失，因此恶化了锂离子二次电池的循环性能。
发明内容
本申请提供一种能解决因正极锰溶出恶化电池循环性能的问题的负极极片及锂离子二次电池。
本申请第一方面提供一种负极极片，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活性物质层，负极活性物质层包括石墨材料；
其中，负极活性物质层的004晶面衍射峰与110晶面衍射峰的强度之比r、负极活性物质层的孔隙率s及负极极片的电阻率t之间满足式(1)，
Figure PCTCN2019116601-appb-000001
式(1)中，t的单位为Ω·m。
本申请第二方面提供一种锂离子二次电池，锂离子二次电池包括正极极片、负极极片、隔离膜和电解液，其中，正极极片包括含锰正极活性物质，负极极片为本申请第一方面的负极极片。
根据本申请的负极极片能够解决正极锰溶出恶化锂离子二次电池的循环性能的问题，从而获得具有较高循环性能的锂离子二次电池。本申请提供的负极极片中，负极活性物质包括石墨材料，并且，负极活性物质层的004晶面衍射峰与110晶面衍射峰的强度之比r、负极活性物质层的孔隙率s及负极极片的电阻率t之间满足上述的式(1)。令人惊讶地发现，该负极极片能够将电解液中的锰阻挡在负极活性物质层外部，有效阻止锰进入负极活性物质层内部，同时能减少锰在负极的沉积，从而有效抑制锰对负极的破坏。这样能提高负极的稳定性，减少负极在循环过程中的容量损失，从而能提高锂离子二次电池在循环过程中的容量保持率，使得锂离子二次电池具有较高的循环性能。本申请的满足上述式(1)的负极极片还能够保证负极活性物质层具有较高的脱锂和嵌锂的动力学性能，使得锂离子二次电池兼具较高的倍率性能。
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，以下结合实施例对本申请进行进一步详细说明。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，“一种或多种”中的“多种”的含义是两种以上，“一个或多个”中的“多个”的含义是两个以上。
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。
负极极片
本申请第一方面提供一种负极极片。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活性物质层。例如，负极集流体在自身厚度方向上包括相对的两个表面，负极活性物质层层叠设置于负极集流体的两个表面中的任意一者或两者上。
负极活性物质层中含有负极活性物质。负极活性物质在工作过程中能够进行锂离子的可逆脱嵌/入嵌，以保证电化学过程的正常进行。负极活性物质包括石墨材料；并且，负极活性物质层的004晶面衍射峰与110晶面衍射峰的强度之比r、负极极片的孔隙率s及负极极片的电阻率t之间满足式(1)：
Figure PCTCN2019116601-appb-000002
式(1)中，t的单位为Ω·m。
在本文中，负极活性物质层的004晶面衍射峰与110晶面衍射峰的强度之比、负极活性物质层的孔隙率及负极极片的电阻率，均为本领域公知的含义。
负极活性物质层的004晶面衍射峰与110晶面衍射峰的强度之比r，也即负极活性物质层的取向指数(简称OI)，表示负极活性物质层中晶粒排列的各向异性程度。可以通过X射线粉末衍射仪(X'pert PRO)，依据X 射线衍射分析法通则以及石墨的点阵参数测定方法JIS K 0131-1996、JB/T4220-2011，得到X射线衍射谱图；然后根据r＝C004/C110得到负极活性物质层的004晶面衍射峰与110晶面衍射峰的强度之比r，其中，C004为004晶面衍射峰的强度，C110为110晶面衍射峰的强度。
负极活性物质层的孔隙率s表示负极活性物质层中孔隙体积与负极活性物质层的总体积的百分比。负极极片的孔隙率可通过孔隙率测量仪测试得到。作为一个示例，称取一定质量的负极极片样品，使用万分尺测量样品的厚度，根据样品的表面积和厚度得到样品的表观体积V 1；将样品置于AccuPyc Ⅱ 1340型全自动真密度测试仪，密闭测试系统，按程序通入氮气，通过检测样品室和膨胀室内的气体压力，再根据玻意耳定律(PV＝C，其中P是气体的压强，V是气体的体积，C为常数)来计算真实体积V 2；之后根据s＝(V 1-V 2)/V 1×100％得出负极活性物质层的孔隙率s。
负极极片的电阻率t表示负极极片的电阻特性。可采用内阻测试仪测试得到负极极片的电阻R，根据公式t＝R·p/h计算出负极极片的电阻率t，其中p为负极极片与内阻测试仪的导电端子的接触面积，例如p＝49πmm 2，h为负极极片的厚度。作为一个示例，采用日置BT3562型内阻测试仪，将负极极片的上下两侧夹持于内阻测试仪的两个导电端子之间，并施加一定的压力固定，测试负极极片的电阻R，其中导电端子的直径为14mm，即上述接触面积p＝49πmm 2，施加的压力为15MPa～27MPa，采点时间的范围为5s～17s。
在本文中，式(1)的计算仅涉及数值的计算，举例来说，负极活性物质层的004晶面衍射峰与110晶面衍射峰的强度之比r为50，负极活性物质层的孔隙率s为25％，负极极片的电阻率t为10Ω·m，则，
Figure PCTCN2019116601-appb-000003
本申请提供的负极极片中，负极活性物质包括石墨材料，并且，负极活性物质层的004晶面衍射峰与110晶面衍射峰的强度之比r、负极活性物质层的孔隙率s及负极极片的电阻率t之间满足上述的式(1)。令人惊讶地发现，该负极极片能够将电解液中的锰阻挡在负极活性物质层外部，有效阻止锰进入负极活性物质层内部，同时减少锰在负极的沉积，从而减少 锰离子与负极中锂的发生离子交换作用。这样能有效抑制锰对负极的破坏，提高负极的稳定性，并且保证负极活性物质层在循环过程中具有良好的脱/嵌锂通道，减少负极在循环过程中的容量损失。因此，采用该负极极片能提高锂离子二次电池的容量保持率，使得锂离子二次电池具有较高的循环性能。满足上述关系式(1)的负极极片还能够保证负极活性物质层具有较高的脱锂和嵌锂的动力学性能，从而使得锂离子二次电池兼具较高的倍率性能。
为了方便起见，定义所述r、s及t之间满足关系式：
Figure PCTCN2019116601-appb-000004
即，0.05≤K≤10。进一步地，K可以为0.05以上，0.1以上，0.15以上，0.2以上，0.5以上，1以上；并且K可以为10以下，8以下，6以下，5以下，3以下，2以下，1以下。在一些实施例中，0.1≤K≤5。在另一些实施例中，0.1≤K≤3。在另一些实施例中，0.2≤K≤1。K值表示了负极极片的r、s和t之间满足适当关系，能使负极极片更好地发挥上述效果。
在一些实施例中，负极活性物质层的004晶面衍射峰与110晶面衍射峰的强度之比r可以为1～50，如4～35，或6～20。这样能进一步减少锰在负极的沉积，同时保证负极活性物质层具有较高的脱锂和嵌锂的动力学性能。
在一些实施例中，负极活性物质层的孔隙率s可以为10％～60％，如15％～50％，或25％～35％。这样，负极活性物质层在具有适于电解液充分浸润的孔隙率的同时，能进一步减少锰在负极的沉积，且保证负极活性物质层具有较高的脱锂和嵌锂的动力学性能。
在一些实施例中，负极活性物质层的压实密度优选为1.5g/cm 3～1.75g/cm 3，如1.55g/cm 3～1.65g/cm 3。这样，负极活性物质层具有适于电解液充分浸润的孔隙率的同时，还使得锰离子在该负极活性物质层的扩散速率较低，从而能进一步减少锰离子与负极中锂的离子交换作用，抑制锰对负极的破坏，提高负极的稳定性。
在一些优选的实施例中，负极活性物质层的孔隙率s为15％～40％， 且负极活性物质层的压实密度为1.55g/cm 3～1.7g/cm 3。该负极活性物质层在适于使电解液充分浸润，满足电池动力学性能需求的同时，能进一步减减小锰对负极的破坏，提高负极的稳定性。
在一些实施例中，负极极片的电阻率t可以为5Ω·m～100Ω·m，如5Ω·m～40Ω·m。这样有利于减少锰在负极的沉积，保证负极极片上述效果的发挥。同时，使负极极片具有较低的电阻率有利于降低锂离子二次电池的整体阻抗，使得锂离子二次电池兼具较高的动力学性能及倍率性能。
本申请的负极极片中，重点在于将负极活性物质层的004晶面衍射峰与110晶面衍射峰的强度之比r、负极活性物质层的孔隙率s及负极极片的电阻率t进行合理匹配，使它们满足上述的式(1)，从而达到上述的技术效果。
在一些实施例中，负极活性物质中的石墨材料可以是人造石墨及天然石墨中的一种或几种。
在一些实施例中，负极活性物质还可以包括中间相微碳球(MCMB)、硬碳、软碳、硅、硅-碳复合物、SiO、Li-Sn合金、Li-Sn-O合金、Sn、SnO、SnO 2、尖晶石结构的钛酸锂Li 4Ti 5O 12、Li-Al合金及金属锂中的一种或多种。
在一些实施例中，负极活性物质中石墨材料的质量百分含量为50wt％以上，如55wt％以上、60wt％以上、65wt％以上、70wt％以上、75wt％以上、80wt％以上、85wt％以上、90wt％以上、95wt％以上。
在一些实施例中，负极活性物质层还可以包括导电剂和粘结剂。本申请对负极活性物质层中的导电剂和粘结剂的种类不做具体限制，可以根据实际需求进行选择。作为示例，导电剂可以选自石墨、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；粘结剂可以选自丁苯橡胶(SBR)、聚偏二氟乙烯(PVDF)、聚四氟乙烯(PTFE)、聚乙烯醇缩丁醛(PVB)、水性丙烯酸树脂(water-based acrylic resin)及羧甲基纤维素(CMC)中的一种或多种。
在一些实施例中，负极活性物质层还可选地包括增稠剂，例如羧甲基纤维素(CMC)。
负极集流体汇集和传导电流。负极集流体可以使用金属箔材或多孔金属板等材料，例如使用铜、镍、钛或铁等金属或它们的合金的箔材或多孔板，如铜箔。
负极极片可以按照本领域常规方法制备。通常将负极活性物质及可选的导电剂、粘结剂和增稠剂分散于溶剂中，溶剂可以是N-甲基吡咯烷酮(NMP)或去离子水，形成均匀的负极浆料；将负极浆料涂覆在负极集流体上，经烘干、冷压等工序后，制得负极极片。
锂离子二次电池
本申请第二方面提供一种锂离子二次电池，包括正极极片、负极极片、隔离膜和电解液，其中负极极片为本申请第一方面提供的任意一种负极极片。
由于采用了本申请第一方面的负极极片，本申请实施例的锂离子二次电池能具有较高的循环性能，同时兼具较高的倍率性能。
正极极片包括正极集流体以及设置于正极集流体至少一个表面上的正极活性物质层。例如，正极集流体在自身厚度方向上包括相对的两个表面，正极活性物质层层叠设置于正极集流体的两个表面中的任意一者或两者上。
正极活性物质层中含有正极活性物质。正极活性物质在工作过程中能够进行锂离子的可逆脱嵌/入嵌。正极活性物质优选为含锰正极活性物质，如LiMn 2O 4、LiNi mCo nMn 1-m-nO 2(0<m<1，0≤n<1，0<m+n<1)等。含锰正极活性物质具有较高的结构稳定性，且其对电解液氧化活性较低，能够减少电解液在正极活性物质表面的副反应，抑制产气、减少产热量。这样能降低锂离子二次电池发生失控的风险，使锂离子二次电池具有较高的安全性能。
在一些实施例中，正极活性物质中可以包括第一正极活性物质和第二正极活性物质。
第一正极活性物质为化学式(1)所示的化合物，
Li 1+xNi aCo bM 1-a-bO 2-yA y     化学式(1)
化学式(1)中，-0.1≤x≤0.2，0<a<1，0≤b<1，0<a+b<1，0≤y<0.2，M为Mn、Fe、Cr、Ti、Zn、V、Al、Zr及Ce中的一种或多种，A包括S、N、F、Cl、Br及I中的一种或多种。
第二正极活性物质为化学式(2)所示的化合物，
Li 1+zMn cM’ 2-cO 4-dA’ d     化学式(2)
化学式(2)中，-0.1≤z≤0.2，0<c≤2，0≤d<1，M’包括Ni、Fe、Cr、Ti、Zn、V、Al、Mg、Zr及Ce中的一种或多种，A’包括S、N、F、Cl、Br及I中的一种或多种。
正极活性物质中包括第一正极活性物质和第二正极活性物质。该正极活性物质具有较高的电压平台和能量密度，以及较高的结构稳定性，能够承受更剧烈的结构破坏力，且无释氧发生，因此能有效减少材料结构破坏带来的热失控。并且该正极活性物质对电解液氧化活性低，能够减少电解液在正极活性物质表面的副反应，抑制产气、减少产热量，从而有效改善锂离子二次电池的安全性能。采用该正极活性物质还能够减少正极极化现象，减少因极化带来的容量损失，特别地，减少正极活性物质中锰离子的溶出，从而能提高锂离子二次电池在循环过程中的容量保持率，使得锂离子二次电池具有较高的循环性能。
也就是说，采用包括第一正极活性物质和第二正极活性物质的正极活性物质，搭配本申请实施例第一方面的负极极片，能使得锂离子二次电池具有较高的电压平台和能量密度，并同时兼顾较高的安全性能、循环性能及倍率性能。
在一些实施例中，化学式(1)中，0.5≤a<1，0<b<0.5，0.7≤a+b<1，0≤y<0.1，M为Mn及Al中的一种或两种，A为S或F中的一种或两种。这能进一步提高锂离子二次电池的能量密度。
在一些实施例中，正极活性物质中第一正极活性物质与第二正极活性物质的质量比为3:7～99.5:0.5，优选为35:65～95:5。
在一些实施例中，正极活性物质层的压实密度优选为3.1g/cm 3～3.65g/cm 3。这使得正极极片厚度一定的条件下，正极活性物质层内部的孔隙率较低，有利于降低正极活性物质中Mn的溶出速率，从而提高电池的循环 性能。该正极活性物质层还使得电池具有较高的可逆容量。
在一些实施例中，正极活性物质层中还可以包括导电剂和粘结剂。本申请对正极活性物质层中的导电剂及粘结剂的种类不做具体限制，可以根据实际需求进行选择。作为示例，导电剂可以选自石墨、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一种或多种；粘结剂可以选自丁苯橡胶(SBR)、水性丙烯酸树脂(water-based acrylic resin)、羧甲基纤维素(CMC)、聚偏二氟乙烯(PVDF)、聚四氟乙烯(PTFE)、聚乙烯醇缩丁醛(PVB)、乙烯-醋酸乙烯酯共聚物(EVA)及聚乙烯醇(PVA)中的一种或多种。
在一些可选地实施方式中，正极活性物质层中导电剂与正极活性物质的质量比大于等于1.5:95.5，粘结剂在正极活性物质层中的重量百分比小于等于2wt％。通过使正极活性物质层中的导电剂及粘结剂的含量在预定范围内，有利于使正极活性物质得到导电剂的充分包覆，形成均匀、快速的电子传输网络，从而提高锂离子二次电池的倍率性能及循环性能。
正极集流体汇集和传导电流。正极集流体可以采用金属箔材或多孔金属板，例如使用铝、铜、镍、钛或银等金属或它们的合金的箔材或多孔板，如铝箔。
正极极片可以采用涂布方式制备。例如先将正极活性物质、粘结剂、导电剂及有机溶剂按照预定比例混合，有机溶剂可以是N-甲基吡咯烷酮(NMP)，将混合物料搅拌至均一体系，获得正极浆料；之后将正极浆料涂布于正极集流体上，经过烘干、辊压等工序后，制得正极极片。
电解液在电池正、负两极之间起传输锂离子的作用。在一些实施例中，电解液包括锂盐和溶剂。
作为一些示例，电解液中的锂盐选自LiPF 6(六氟磷酸锂)、LiBF 4(四氟硼酸锂)、LiClO 4(高氯酸锂)、LiAsF 6(六氟砷酸锂)、LiFSI(双氟磺酰亚胺锂)、LiTFSI(双三氟甲磺酰亚胺锂)、LiTFS(三氟甲磺酸锂)、LiDFOB(二氟草酸硼酸锂)、LiBOB(双草酸硼酸锂)、LiPO 2F 2(二氟磷酸锂)、LiDFOP(二氟草酸磷酸锂)及LiTFOP(四氟草酸磷酸锂)中的一种或多种，优选为LiPF 6(六氟磷酸锂)、LiBF 4(四氟硼酸 锂)、LiBOB(双草酸硼酸锂)、LiDFOB(二氟草酸硼酸锂)、LiTFSI(双三氟甲磺酰亚胺锂)及LiFSI(双氟磺酰亚胺锂)中的一种或多种。
作为一些示例，电解液中的溶剂采用非水有机溶剂，例如碳酸乙烯酯(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)、甲酸甲酯(MF)、乙酸甲酯(MA)、乙酸乙酯(EA)、乙酸丙酯(PA)、丙酸甲酯(MP)、丙酸乙酯(EP)、丙酸丙酯(PP)、丁酸甲酯(MB)及丁酸乙酯(EB)中的一种或多种，优选为两种以上。
在一些实施例中，电解液中还含有锰离子络合添加剂，锰离子络合添加剂优选为或包括链状腈类化合物。锰离子络合添加剂，特别是采用链状腈类锰离子络合添加剂，能够钝化正极活性物质中的锰，有效减少锰离子的溶出，减小正极活性物质的结构破坏，同时减少负极上锰的沉积，从而提高锂离子二次电池的循环性能。
优选地，锰离子络合添加剂包括己二腈(ADN)、丁二腈(SN)、戊二腈(GN)及己烷三腈(HTN)中的一种或多种。
在一些实施例中，电解液中锰离子络合添加剂的质量百分含量优选为0.1wt％～4wt％。
在一些实施例中，电解液中还含有负极成膜添加剂，负极成膜添加剂优选包括含不饱和键的环状碳酸酯、含氟环状碳酸酯、环状磺酸酯及环状硫酸酯中的一种或多种。负极成膜添加剂能够在负极形成具有良好的锂离子传输性能及力学性能的界面膜，加强对负极的保护。该界面膜还能够有效阻止锰离子络合添加剂在负极发生嵌插反应，防止锰离子络合添加剂的加入造成负极界面破坏，提高负极稳定性。因此，在电解液中含有负极成膜添加剂能够进一步提高锂离子二次电池的循环性能。
优选地，负极成膜添加剂包括碳酸亚乙烯酯(VC)、碳酸乙烯亚乙酯(VEC)、氟代碳酸亚乙酯(FEC)、二氟碳酸亚乙酯(DFEC)、三氟甲基碳酸亚乙酯(TFPC)、甲烷二磺酸亚甲酯(MMDS)、1,3-丙烷磺酸内酯(1,3-PS)、1-丙烯-1,3-磺酸内酯(PST)及硫酸亚乙酯(DTD)中的一 种或多种。
在一些实施例中，电解液中负极成膜添加剂的质量百分含量优选为0.1wt％～2wt％。
在一些实施例中，电解液中还含有含氟锂盐型添加剂。含氟锂盐型添加剂能够有效控制因负极界面成膜加强带来的阻抗增大，使负极极片具有较低的阻抗，从而使锂离子二次电池具有较低的内阻。这样能使锂离子二次电池具有较高的循环性能的同时，兼顾较高的动力学性能和倍率性能。
优选地，含氟锂盐型添加剂包括二氟磷酸锂LiPO 2F 2、二氟草酸磷酸锂LiDFOP、四氟硼酸锂LiBF 4及二氟草酸硼酸锂LiDFOB中的一种或多种。
在一些实施例中，电解液中含氟锂盐型添加剂的质量百分含量优选为0.05wt％～1.5wt％。
可以理解的是，二氟磷酸锂LiPO 2F 2、二氟草酸磷酸锂LiDFOP、四氟硼酸锂LiBF 4及二氟草酸硼酸锂LiDFOB可以同时用作电解质锂盐和含氟锂盐型添加剂。其中保证含氟锂盐型添加剂满足预设量即可，以确保含氟锂盐型添加剂能够有效控制因负极界面成膜加强带来的阻抗增大。
在一些实施例中，电解液中还可选地含有其他添加剂，如磺酸酯环状季铵盐、三(三甲基硅烷)磷酸酯(TMSP)、三(三甲基硅烷)硼酸酯(TMSB)等。
本申请的锂离子二次电池对隔离膜没有特别的限制，可以选用任意公知的具有电化学稳定性和化学稳定性的多孔结构隔离膜，例如包含玻璃纤维、无纺布、聚乙烯(PE)、聚丙烯(PP)及聚偏二氟乙烯(PVDF)中的一种或多种的单层或多层薄膜。
正极极片和负极极片交替层叠设置，并在正极极片与负极极片之间设置隔离膜以起到隔离正极极片和负极极片的作用，得到电芯，也可以是经卷绕后得到电芯；将电芯置于外壳中，注入电解液，使电解液充分浸润于正极活性物质层、负极活性物质层和隔离膜的孔隙中，并封口，得到锂离子二次电池。
本申请的锂离子二次电池的剩余容量为额定容量的70％以上时，负极 活性物质层中Mn元素总含量不超过1500ppm。其中ppm(parts per million)是负极活性物质层中锰元素的质量占负极活性物质层的质量的百万分比。本申请通过设置负极活性物质层的004晶面衍射峰与110晶面衍射峰的强度之比r、负极活性物质层的孔隙率s及负极极片的电阻率t之间满足上述的式(1)，可以有效的抑制电池在充放电的循环过程中，正极活性物质中的Mn元素在负极活性物质层的沉积，使得负极活性物质层在电池后续循环过程中保持良好的脱/嵌锂通道。因此能提高电池的循环性能，并保证负极活性物质层具有较高的脱锂和嵌锂的动力学性能，使得锂离子二次电池兼具较高的倍率性能。
实施例
下述实施例更具体地描述了本申请公开的内容，这些实施例仅仅用于阐述性说明，因为在本申请公开内容的范围内进行各种修改和变化对本领域技术人员来说是明显的。除非另有声明，以下实施例中所报道的所有份、百分比、和比值都是基于重量计，而且实施例中使用的所有试剂都可商购获得或是按照常规方法进行合成获得，并且可直接使用而无需进一步处理，以及实施例中使用的仪器均可商购获得。
实施例1
正极极片的制备
将第一正极活性物质LiNi 0.8Co 0.1Mn 0.1O 2、第二正极活性物质LiMn 2O 4、导电炭黑及粘结剂PVDF分散至溶剂NMP中进行混合均匀，得到正极浆料；将正极浆料均匀涂布于正极集流体铝箔上，经烘干、冷压、分条、裁片后，得到正极极片。其中第一正极活性物质LiNi 0.8Co 0.1Mn 0.1O 2与第二正极活性物质LiMn 2O 4的质量比为55:45，正极活性物质、导电炭黑及粘结剂PVDF的重量比为96:2:2。
负极极片的制备
将负极活性物质石墨、导电炭黑、增稠剂CMC及粘结剂SBR按照重量比96:1:1:2分散于溶剂去离子水中进行混合均匀，得到负极浆料；将负极浆料均匀涂布于负极集流体铜箔上；经烘干、冷压、分条、裁片后，得 到负极极片。
电解液的制备
将碳酸乙烯酯(EC)、碳酸甲乙酯(EMC)及碳酸二乙酯(DEC)以质量比30:40:30混合均匀，得到非水有机溶剂。将1mol/L的LiPF 6溶解于上述非水有机溶剂中，混合均匀，得到电解液。
锂离子二次电池的制备
将正极极片、隔离膜及负极极片依次层叠设置，隔离膜采用PP/PE/PP复合薄膜，然后卷绕成电芯并装入软包外壳中，经顶侧封、注入电解液等工序后，制成软包电池。
实施例2～12及对比例1～2
与实施例1不同的是，调整锂离子二次电池的相关参数，详见表1。
测试部分
(1)锂离子二次电池的高温循环性能测试
在45℃下，将锂离子二次电池搁置5分钟，以1C倍率恒流充电至4.2V，再恒压充电至电流小于等于0.05C，之后搁置5分钟，再以1C倍率恒流放电至3.0V，此为一个充放电循环，此次的放电容量记为锂离子二次电池第1次循环的放电容量。将锂离子二次电池按照上述方法进行400次循环充放电测试，记录每一次循环的放电容量。
锂离子二次电池45℃、1C/1C循环400次后的容量保持率(％)＝第400次循环的放电容量/第1次循环的放电容量×100％。
(2)锂离子二次电池的直流阻抗测试
在25℃下，将锂离子二次电池搁置5分钟，以1C倍率恒流充电至4.2V，再恒压充电至电流小于等于0.05C，此时电池的荷电状态(SOC)为100％，之后搁置5分钟，再以1C倍率恒流放电，将锂离子二次电池的荷电状态(SOC)调整至50％。
将50％SOC的锂离子二次电池继续搁置10分钟，以4C倍率恒流放电30秒钟。记录搁置最后1秒的电压U 1、4C倍率恒流放电最后1秒的电压U 2，以及4C倍率恒流放电的电流I。
锂离子二次电池25℃、50％SOC、4C倍率恒流放电30s的直流阻抗 ＝(U 2-U 1)/I。
(3)锂离子二次电池的热冲击测试
在25℃下，将锂离子二次电池搁置5分钟，以1C倍率恒流充电至4.2V，再恒压充电至电流小于等于0.05C，之后搁置5分钟。然后将锂离子二次电池放置于烘箱中，设置烘箱温度以2℃/min的升温速率从25℃升温至130℃，保温2小时。在升温过程及保温过程中监控电池表面的温度，记录电池最高表面温度。
(4)负极活性物质层的锰元素含量测试
在25℃下，将剩余容量为额定容量70％的锂离子二次电池搁置5分钟，以1C倍率恒流充电至4.2V，再恒压充电至电流小于等于0.05C，之后搁置5分钟，再以1C倍率恒流放电至3.0V。
通过微波消解仪消解负极活性物质层。具体地，拆解上述锂离子二次电池，取负极活性物质层刮粉，将所刮粉体置入消解灌中，启动消解仪消解粉体，得到负极活性物质层消解液。其中负极活性物质层的质量记为m 1(g)。
通过等离子发射光谱仪PE7000DV，测试微量锰元素质量。具体地，配制锰元素标准液，测试并绘制锰元素标准曲线，然后测试上述负极活性物质层消解液中锰元素的质量，记为m 2(mg)。
负极活性物质层的锰元素含量(ppm)＝m 2/m 1。
实施例1～12和对比例1～2的测试结果示于表2。
表1
Figure PCTCN2019116601-appb-000005
表1中，锰离子络合添加剂的含量、负极成膜添加剂的含量及含氟锂盐型添加剂的含量均是在电解液中的质量百分含量。
表2
Figure PCTCN2019116601-appb-000006
对比分析实施例1～12与对比例1～2可知，锂离子二次电池的正极活性物质中包括第一正极活性物质和第二正极活性物质，锂离子二次电池在热冲击测试中电池温升得到有效控制，使得锂离子二次电池具有较高的安全性能。
由于负极活性物质层的OI值r、负极极片的孔隙率s及负极极片的电阻率t之间满足上述的式(1)，将剩余容量为额定容量的70％的锂离子二次电池以1C倍率恒流充电至4.2V，再以1C倍率恒流放电至3.0V，沉积在负极活性物质层的锰元素含量降低至1500ppm以下。电池充放电过程中沉积在负极活性物质层的锰元素含量明显降低，使得负极活性物质层在电池后续循环过程中保持良好的脱/嵌锂通道，提高了电池的循环性能。
由于负极活性物质层的OI值r、负极极片的孔隙率s及负极极片的电阻率t之间满足上述的式(1)，使得锂离子二次电池在45℃、1C/1C下进行400次充放电循环之后的容量保持率得到明显升高，可见锂离子二次电池的循环性能得到明显提高。同时，锂离子二次电池25℃、50％SOC、4C 倍率恒流放电30s的直流阻抗也较低，使得锂离子二次电池能兼具较高的动力学性能和倍率性能。
结合实施例1～12可知，本申请的锂离子二次电池能同时兼顾较高的安全性能及循环性能，并具有较低的阻抗，因此还能兼具较高的动力学性能及倍率性能。
以上所述，仅为本申请的具体实施方式，但本申请的保护范围并不局限于此，任何熟悉本技术领域的技术人员在本申请揭露的技术范围内，可轻易想到各种等效的修改或替换，这些修改或替换都应涵盖在本申请的保护范围之内。因此，本申请的保护范围应以权利要求的保护范围为准。

Claims (14)

  1. 一种负极极片，包括负极集流体以及设置在所述负极集流体至少一个表面上的负极活性物质层，所述负极活性物质层包括石墨材料；
    其中，所述负极活性物质层的004晶面衍射峰与110晶面衍射峰的强度之比r、所述负极活性物质层的孔隙率s及所述负极极片的电阻率t之间满足式(1)，
    Figure PCTCN2019116601-appb-100001
    所述式(1)中，t的单位为Ω·m。
  2. 根据权利要求1所述的负极极片，其中，所述负极活性物质层的004晶面衍射峰与110晶面衍射峰的强度之比r为1～50。
  3. 根据权利要求1所述的负极极片，其中，所述负极活性物质层的孔隙率s为10％～60％；和/或，
    所述负极活性物质层的压实密度为1.5g/cm 3～1.75g/cm 3。
  4. 根据权利要求1所述的负极极片，其中，所述负极极片的电阻率t为5Ω·m～100Ω·m。
  5. 一种锂离子二次电池，包括正极极片、负极极片、隔离膜和电解液，其中，所述正极极片包括含锰正极活性物质，所述负极极片为如权利要求1-4任一项所述的负极极片。
  6. 根据权利要求5所述的锂离子二次电池，其中，所述正极极片包括化学式(1)所示的第一正极活性物质和化学式(2)所示的第二正极活性物质，
    Li 1+xNi aCo bM 1-a-bO 2-yA y    化学式(1)
    Li 1+zMn cM’ 2-cO 4-dA’ d    化学式(2)
    所述化学式(1)中，-0.1≤x≤0.2，0<a<1，0≤b<1，0<a+b<1，0≤y<0.2，M为Mn、Fe、Cr、Ti、Zn、V、Al、Zr及Ce中的一种或多种，A包括S、N、F、Cl、Br及I中的一种或多种，
    优选地，0.5≤a<1，0<b<0.5，0.7≤a+b<1，0≤y<0.1，M为Mn及Al中 的一种或两种，A为S或F中的一种或两种，
    所述化学式(2)中，-0.1≤z≤0.2，0<c≤2，0≤d<1，M’包括Ni、Fe、Cr、Ti、Zn、V、Al、Mg、Zr及Ce中的一种或多种，A’包括S、N、F、Cl、Br及I中的一种或多种。
  7. 根据权利要求6所述的锂离子二次电池，其中，所述第一正极活性物质与所述第二正极活性物质的质量比为3:7～99.5:0.5，优选为35:65～95:5。
  8. 根据权利要求5-7任一项所述的锂离子二次电池，其中，所述电解液中含有锰离子络合添加剂，所述锰离子络合添加剂优选包括链状腈类化合物，更优选包括己二腈、丁二腈、戊二腈及己烷三腈中的一种或多种。
  9. 根据权利要求8所述的锂离子二次电池，其中，所述电解液中所述锰离子络合添加剂的质量百分含量为0.1wt％～4wt％。
  10. 根据权利要求5-9任一项所述的锂离子二次电池，其中，所述电解液中含有负极成膜添加剂，所述负极成膜添加剂优选包括含不饱和键的环状碳酸酯、含氟环状碳酸酯、环状磺酸酯及环状硫酸酯中的一种或多种，更优选包括碳酸亚乙烯酯、碳酸乙烯亚乙酯、氟代碳酸亚乙酯、二氟碳酸亚乙酯、三氟甲基碳酸亚乙酯、甲烷二磺酸亚甲酯、1,3-丙烷磺酸内酯、1-丙烯-1,3-磺酸内酯及硫酸亚乙酯中的一种或多种。
  11. 根据权利要求10所述的锂离子二次电池，其中，所述电解液中所述负极成膜添加剂的质量百分含量为0.1wt％～2wt％。
  12. 根据权利要求10或11所述的锂离子二次电池，其中，所述电解液中还含有含氟锂盐型添加剂，所述含氟锂盐型添加剂优选包括二氟磷酸锂LiPO 2F 2、二氟草酸磷酸锂LiDFOP、四氟硼酸锂LiBF 4及二氟草酸硼酸锂LiDFOB中的一种或多种。
  13. 根据权利要求12所述的锂离子二次电池，其中，所述电解液中所述含氟锂盐型添加剂的质量百分含量为0.05wt％～1.5wt％。
  14. 根据权利要求5-13任一项所述的锂离子二次电池，其中，所述锂离子电池的剩余容量为额定容量的70％以上时，所述负极活性物质层中Mn元素的总含量不超过1500ppm。
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CN110265625B (zh) 2020-12-04
PL3651245T3 (pl) 2023-01-30
EP3651245B1 (en) 2022-11-23
US11355742B2 (en) 2022-06-07
HUE060501T2 (hu) 2023-03-28
EP3651245A1 (en) 2020-05-13
US20200152964A1 (en) 2020-05-14

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