WO2024040525A1 - 二次电池及用电装置 - Google Patents

二次电池及用电装置 Download PDF

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WO2024040525A1
WO2024040525A1 PCT/CN2022/114857 CN2022114857W WO2024040525A1 WO 2024040525 A1 WO2024040525 A1 WO 2024040525A1 CN 2022114857 W CN2022114857 W CN 2022114857W WO 2024040525 A1 WO2024040525 A1 WO 2024040525A1
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negative electrode
secondary battery
active layer
lithium
negative
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PCT/CN2022/114857
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English (en)
French (fr)
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李璇
孙信
吴李力
陈兴布
宋佩东
云亮
刘润蝶
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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 PCT/CN2022/114857 priority Critical patent/WO2024040525A1/zh
Publication of WO2024040525A1 publication Critical patent/WO2024040525A1/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
    • H01M4/36—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
    • 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
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • 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
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present application relates to the field of batteries, and specifically to a secondary battery and an electrical device.
  • Secondary batteries are increasingly widely used because of their clean and renewable characteristics. Secondary batteries such as lithium-ion batteries are mainly composed of five parts: positive electrode, negative electrode, separator, electrolyte and casing. They mainly rely on lithium ions to move between the positive electrode and the negative electrode. Move to generate electrical energy. During charging, lithium ions or sodium ions are deintercalated from the positive electrode and embedded in the negative electrode through the electrolyte. The opposite is true during discharge.
  • the present application provides a secondary battery and an electrical device, which have both high energy density and excellent cycle performance.
  • the first aspect of the present application provides a secondary battery.
  • the secondary battery includes a positive electrode sheet and a negative electrode sheet.
  • the total capacity of the positive electrode sheet is P
  • the total capacity of the negative electrode sheet is N, N and P satisfy: N/P ⁇ 1;
  • the negative electrode sheet includes a current collector and a first negative electrode active layer, an insulating material layer and a second negative electrode active layer sequentially disposed on the surface of the current collector.
  • the total capacity of the positive and negative electrodes of the secondary battery is designed and controlled to control N/P ⁇ 1, so that the amount of lithium ions in the positive electrode sheet is much greater than the amount of lithium ions that the positive electrode sheet can accommodate.
  • some excess lithium ions will be deposited on the negative electrode sheet in the form of lithium metal, thereby forming a lithium metal complex with the negative electrode active material on the negative electrode sheet.
  • the formation of the lithium metal complex can improve the energy density of the secondary battery; in addition, On the one hand, another part of excess lithium ions forms lithium dendrites when deposited on the surface of the negative electrode sheet, thereby causing the problem of short circuit of the battery.
  • the second negative electrode active layer enables lithium dendrites to be deposited between the insulating material layer and the current collector interface.
  • the second negative electrode active layer is provided to absorb and cover the lithium dendrites punctured from the insulating material layer to avoid the formation of lithium dendrites on the surface of the negative electrode sheet. Crystals, thereby piercing the diaphragm and causing a short circuit. As a result, the secondary battery has both high energy density and excellent cycle performance.
  • the thickness of the insulating material layer is L 1 ⁇ m
  • the thickness of the second negative active layer is L 2 ⁇ m
  • the thickness of the insulating material layer is set according to the N/P value.
  • the N/P value is small, the more excess lithium ions are, the thicker the lithium dendrites deposited on the negative electrode sheet, and the thicker the thickness of the insulating material layer is controlled, At the same time, the thickness ratio of the insulating material layer and the second negative electrode active layer is controlled to ensure good ion transmission and avoid the formation of lithium dendrites on the surface of the negative electrode sheet, thereby piercing the separator and causing a short circuit.
  • the secondary battery has both high energy density and excellent cycle performance.
  • the thickness of the insulating material layer is 0.2 ⁇ m to 15 ⁇ m;
  • the thickness of the insulating material layer is 3.1 ⁇ m ⁇ 7.9 ⁇ m.
  • the thickness of the first negative active layer is 10 ⁇ m to 300 ⁇ m;
  • the thickness of the first negative active layer is 60 ⁇ m to 200 ⁇ m.
  • the component of the second negative active layer includes a lithiophilic material.
  • lithium dendrites are deposited between the insulating material layer and the current collector interface and continue to accumulate.
  • the insulating material layer will be pierced and embedded in the second negative electrode active layer and the second negative electrode.
  • the active layer is overlapped.
  • the second negative active layer further covers the lithium dendrites to prevent them from puncturing the isolation film.
  • the lithiophilic material in the second negative active layer can further interact with the embedded third
  • the lithium dendrites in the active layer of the two negative electrodes combine to absorb the lithium dendrites, which can prevent further diffusion of lithium dendrites and achieve passivation.
  • lithium metal is used as the reference electrode, and the overpotential of the lithiophilic material is not greater than 0.03V.
  • the lithiophilic material is selected from the group consisting of Au, Ag, Zn, Fe, Co, Ni, Ga, Sn, In, Ge, Ti, Mu, Pt, Al, Mg and their oxides, sulfide One or more of substances, fluorides, nitrogen compounds, chlorides, and carbides.
  • the secondary battery satisfies at least one of the following conditions a to b:
  • the mass proportion of the lithiophilic material is 0.2% to 5%;
  • the mass proportion of the lithiophilic material is 0.3% to 3%;
  • the overpotential of the second negative active layer is 0-0.3V.
  • the overpotential of the first negative active layer is 0.1V ⁇ 0.6V.
  • the components of the first negative active layer and the second negative active layer include a negative active material and metal lithium, and the metal lithium is supported on the surface of the negative active material.
  • the positive electrode sheet includes a current collector and a positive active layer loaded on the surface of the current collector.
  • the components of the positive active layer include lithium ion positive active materials, and the metallic lithium is derived from Lithium ions in the lithium ion positive active material contained in the positive electrode sheet.
  • the secondary battery satisfies at least one of the following conditions c to d:
  • the negative active material accounts for 80% to 98%;
  • the negative active material accounts for 80% to 98%.
  • the negative active material includes mesocarbon microspheres, graphite, glassy carbon, carbon nanotubes, carbon-carbon composite materials, carbon fiber, hard carbon, soft carbon, silicon-based materials, and magnesium-based materials. , at least one of tin-based materials and iron-based materials.
  • the components of the insulating material layer include insulating materials and adhesives.
  • the insulating material includes at least one of an organic insulating material and an inorganic insulating material.
  • the inorganic insulating material is selected from the group consisting of aluminum oxide, silicon oxide, zinc oxide, iron oxide, copper oxide, and titanium oxide. , at least one of mica, asbestos, marble and ceramics, and the organic insulating material is selected from at least one of natural rubber, styrene-butadiene rubber, butadiene rubber and isoprene rubber.
  • a second aspect of the present application provides an electrical device, which includes the secondary battery of the first aspect of the present application.
  • FIG. 1 is a schematic diagram of an embodiment of a secondary battery.
  • FIG. 2 is an exploded view of FIG. 1 .
  • Figure 3 is a schematic diagram of an embodiment of a battery pack.
  • FIG. 4 is an exploded view of FIG. 3 .
  • FIG. 5 is a schematic diagram of an embodiment of a power consumption device in which a secondary battery is used as a power source.
  • an embodiment means that a particular feature, structure or characteristic described in connection with the embodiment can be included in at least one embodiment of the present application.
  • the appearances of this phrase in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments. Those skilled in the art understand, both explicitly and implicitly, that the embodiments described herein may be combined with other embodiments.
  • multiple refers to more than two (including two).
  • multiple groups refers to two or more groups (including two groups), and “multiple pieces” refers to It is more than two pieces (including two pieces).
  • the capacity balance between the negative electrode (NE) and the positive electrode (PE) is considered a key point.
  • the positive electrode is excessive, the excess lithium ions released from the positive electrode during the charging process will remain on the surface of the negative electrode.
  • Precipitation to form lithium dendrites can easily cause a short circuit within the battery, thereby affecting battery safety performance; and the formation of lithium dendrites can pierce the isolation film, causing a short circuit and causing a safety accident. Therefore, in traditional technology, in order to avoid lithium precipitation and obtain good safety, the negative electrode generally needs to be over-designed, that is, the total capacity ratio N/P value in the corresponding area of the negative electrode sheet and the positive electrode sheet is controlled to >1.
  • An embodiment of the present application provides a secondary battery.
  • the secondary battery includes a positive electrode sheet and a negative electrode sheet.
  • the total capacity of the positive electrode sheet is P
  • the total capacity of the negative electrode sheet is N.
  • N and P satisfy: N/P ⁇ 1 .
  • the negative electrode sheet includes a current collector and a first negative electrode active layer, an insulating material layer and a second negative electrode active layer sequentially located on the surface of the current collector.
  • the total capacity of the positive and negative electrodes of the secondary battery is designed and controlled to control N/P ⁇ 1, so that the amount of lithium ions in the positive electrode sheet is much greater than the amount of lithium ions that the positive electrode sheet can accommodate.
  • some excess lithium ions will be deposited on the negative electrode sheet in the form of lithium metal, thereby forming a lithium metal complex with the negative electrode active material on the negative electrode sheet.
  • the formation of the lithium metal complex can improve the energy density of the secondary battery; in addition, On the one hand, another part of excess lithium ions forms lithium dendrites when deposited on the surface of the negative electrode sheet, thereby causing the problem of short circuit of the battery.
  • the second negative electrode active layer enables lithium dendrites to be deposited between the insulating material layer and the current collector interface.
  • the second negative electrode active layer is provided to absorb and cover the lithium dendrites punctured from the insulating material layer to avoid the formation of lithium dendrites on the surface of the negative electrode sheet. Crystals, thereby piercing the diaphragm and causing a short circuit. As a result, the secondary battery has both high energy density and excellent cycle performance.
  • the thickness of the insulating material layer is L 1 ⁇ m
  • the thickness of the second negative active layer is L 2 ⁇ m
  • the technicians of this application obtained that the thickness of the insulating material layer is set according to the N/P value.
  • the N/P value is smaller, the more excess lithium ions are, the more the negative electrode sheet is deposited.
  • the thicker the lithium dendrites the thicker the thickness of the insulating material layer should be controlled.
  • the thickness ratio of the insulating material layer and the second negative electrode active layer should be controlled to ensure good ion transmission and avoid the formation of lithium dendrites on the surface of the negative electrode sheet, thus stimulating Penetrating the diaphragm causes a short circuit.
  • the secondary battery has both high energy density and excellent cycle performance.
  • L 1 and L 2 satisfy: 0.01 ⁇ L 2 /L 1 ⁇ 0.1.
  • L 1 and L 2 satisfy: 0.03 ⁇ L 2 /L 1 ⁇ 0.08.
  • L 2 /L 1 includes the minimum value and maximum value of the range, and every value between the minimum value and the maximum value, L 2 / Specific examples of L 1 include, but are not limited to, the point values in the embodiment: 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1.
  • the thickness of the insulating material layer is 0.2 ⁇ m to 15 ⁇ m.
  • the thickness of the above-mentioned insulating material layer is 3.1 ⁇ m ⁇ 7.9 ⁇ m.
  • the value includes the minimum value and the maximum value of the range, and every value between the minimum value and the maximum value.
  • Specific examples include but are not limited to the point values in the embodiment and: 0.2 ⁇ m, 0.3 ⁇ m, 0.5 ⁇ m, 1 ⁇ m, 1.5 ⁇ m, 2 ⁇ m, 2.5 ⁇ m, 3 ⁇ m, 3.5 ⁇ m, 4 ⁇ m, 4.5 ⁇ m, 5 ⁇ m, 5.5 ⁇ m, 6 ⁇ m, 6.5 ⁇ m, 7 ⁇ m, 7.1 ⁇ m, 7.2 ⁇ m, 7.3 ⁇ m, ⁇ m, 7.5 ⁇ m, 7.7 ⁇ m, 7.8 ⁇ m, 7.9 ⁇ m, 8 ⁇ m, 8.5 ⁇ m, 9 ⁇ m, 9.5 ⁇ m, 10 ⁇ m, 10.5 ⁇ m, 11 ⁇ m, 11.5 ⁇ m, 12 ⁇ m, 12.5 ⁇ m, 13 ⁇ m, 13.5 ⁇ m, 4 ⁇ m, 14.5 ⁇ m, 15 ⁇ m .
  • the thickness of the first negative active layer is 10 ⁇ m to 300 ⁇ m.
  • the thickness of the first negative active layer is 60 ⁇ m to 200 ⁇ m.
  • the component of the second negative electrode active layer includes a lithiophilic material.
  • lithium dendrites are deposited between the insulating material layer and the current collector interface and continue to accumulate.
  • the insulating material layer will be pierced and embedded in the second negative electrode active layer and the second negative electrode.
  • the active layer is overlapped.
  • the second negative active layer further covers the lithium dendrites to prevent them from puncturing the isolation film.
  • the lithiophilic material in the second negative active layer can further interact with the embedded third
  • the lithium dendrites in the active layer of the two negative electrodes combine to absorb the lithium dendrites, which can prevent further diffusion of lithium dendrites and achieve passivation.
  • lithium metal is used as the reference electrode, and the overpotential of the lithiophilic material is not greater than 0.03V.
  • the overpotential of the above-mentioned lithiophilic materials was tested using a three-electrode electrochemical cell test, with the lithiophilic material as the working electrode, Li 0.5 FePO 4 as the reference electrode, and lithium metal as the counter electrode.
  • the specific test methods are as follows:
  • Lithium metal was deposited on the working electrode at a current density of 10 ⁇ A cm -2 .
  • the voltage of the working electrode relative to Li metal (Li/Li+) as the ordinate, and the capacity as the abscissa. When the capacity increases, the voltage first decreases and then remains flat. During this process, if the curve has no inflection point or the absolute value of the voltage on the ordinate corresponding to the inflection point is ⁇ 0.03V, it indicates that the material to be tested is lithiophilic.
  • the lithiophilic material is selected from the group consisting of Au, Ag, Zn, Fe, Co, Ni, Ga, Sn, In, Ge, Ti, Mu, Pt, Al, Mg and their oxides, sulfides, One or more of fluoride, nitrogen compound, chloride and carbide.
  • the mass proportion of the lithiophilic material in the second negative electrode active layer is 0.2% to 5%.
  • the mass proportion of the lithiophilic material in the second negative electrode active layer is 0.3% to 3%.
  • lithium metal is used as the reference electrode, and the overpotential of the second negative electrode active layer is 0 to 0.3V.
  • lithium metal is used as the reference electrode, and the overpotential of the first negative active layer is 0.1V to 0.6V.
  • the overpotential of the above-mentioned second negative electrode active layer or first negative electrode active layer is tested using a three-electrode electrochemical cell, with the second negative electrode active layer or the first negative electrode active layer as the working electrode,
  • Li 0.5 FePO 4 was used as the reference electrode, and lithium metal was used as the counter electrode.
  • the specific test methods are as follows:
  • Lithium metal was deposited on the working electrode at a current density of 10 ⁇ A cm -2 .
  • the voltage of the working electrode relative to Li metal (Li/Li+) as the ordinate, and the capacity as the abscissa. When the capacity increases, the voltage first decreases and then remains flat. During this process, the absolute value of the voltage on the ordinate corresponding to the inflection point of the curve is the overpotential.
  • the components of the above-mentioned first negative electrode active layer and the above-mentioned second negative electrode active layer include a negative electrode active material and metal lithium, and the metal lithium is supported on the surface of the negative electrode active material.
  • Metal lithium is loaded on the surface of the negative active material to form a lithium metal composite lithium substance, which is beneficial to improving the energy density of the secondary battery.
  • the energy density of the above-mentioned secondary battery can reach 300Wh/kg to 600Wh/kg, or even higher.
  • the proportion of the negative electrode active material is 80% to 99%.
  • the proportion of the negative electrode active material is 88% to 98%.
  • the proportion of the negative electrode active material is 80% to 99%.
  • the proportion of the negative electrode active material is 88% to 98%.
  • the above-mentioned negative active material includes mesophase carbon microspheres, graphite, glassy carbon, carbon nanotubes, carbon-carbon composite materials, carbon fiber, hard carbon, soft carbon, silicon-based materials, tin-based materials, At least one of magnesium-based materials and iron-based materials.
  • negative active materials include, but are not limited to: interphase carbon microspheres, natural graphite, artificial graphite, graphene, glassy carbon, carbon nanotubes, carbon fiber, hard carbon, soft carbon, iron oxide, tin oxide, silicon oxide, At least one of magnesium oxide and silicon-carbon composite.
  • the components of the first negative active layer and the second negative active layer further include a binder.
  • the proportion of the binder in the first negative active layer is 0.5% to 10%.
  • the proportion of the binder in the first negative active layer is 1% to 4%.
  • the proportion of the binder in the second negative active layer is 0.5% to 10%.
  • the proportion of binder in the above-mentioned second negative electrode active layer is 1% to 4%.
  • the components of the first negative active layer further include a conductive agent.
  • the proportion of the conductive agent in the first negative electrode active layer is 0.1% to 10%.
  • the proportion of the conductive agent in the first negative electrode active layer is 0.3% to 3%.
  • the conductive agent may be one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.
  • the binder may be styrene-butadiene rubber (SBR), water-based acrylic resin, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), ethylene-vinyl acetate copolymer ( One or more of EVA), polyvinyl alcohol (PVA) and polyvinyl butyral (PVB).
  • SBR styrene-butadiene rubber
  • PVDF polyvinylidene fluoride
  • PTFE polytetrafluoroethylene
  • EVA polyvinyl alcohol
  • PVB polyvinyl butyral
  • the components of the above-mentioned first active layer and the second active layer may also include a thickener.
  • the thickener may be carboxymethyl cellulose sodium CMC-Na.
  • the positive electrode sheet includes a current collector and a positive electrode active layer supported on the surface of the current collector.
  • the positive electrode active layer includes a lithium ion positive electrode active material as a component, and the metal lithium is derived from the lithium metal contained in the positive electrode sheet. Lithium ions in the lithium ion cathode active material.
  • charging and discharging can be carried out during the formation stage of the battery, so that the negative electrode sheet of the secondary battery shipped from the factory already has the negative active material and lithium metal to form a lithium metal composite lithium substance.
  • the lithium metal composite lithium substance can also be used in the subsequent process. formed in.
  • the mass proportion of the lithium ion cathode active material in the cathode active layer is 80% to 98%.
  • the above-mentioned lithium ion positive electrode active material may be a lithium ion positive electrode active material for secondary batteries that is well known in the art.
  • the lithium ion cathode active material may include at least one of the following materials: an olivine-structured lithium-containing phosphate, a lithium transition metal oxide, and their respective modified compounds.
  • an olivine-structured lithium-containing phosphate a lithium transition metal oxide
  • their respective modified compounds the present application is not limited to these materials, and other traditional materials that can be used as positive electrode active materials of batteries can also be used. Only one type of these positive electrode active materials may be used alone, or two or more types may be used in combination.
  • lithium transition metal oxides may include, but are not limited to, NCM ternary materials, lithium cobalt oxides (such as LiCoO 2 ), lithium nickel oxides (such as LiNiO 2 ), lithium manganese oxides (such as LiMnO 2 , LiMn 2 O 4 ), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi 1/3 Co 1/3 Mn 1/3 O 2 (also referred to as NCM333 ), LiNi 0.5 Co 0.2 Mn 0.3 O 2 (can also be abbreviated to NCM523), LiNi 0.5 Co 0.
  • NCM333 LiNi 1/3 Co 1/3 Mn 1/3 O 2
  • NCM523 LiNi 0.5 Co 0.2 Mn 0.3 O 2
  • LiNi 0.6 Co 0.2 Mn 0.2 O 2 can also be abbreviated to NCM622
  • LiNi 0.8 Co 0.1 Mn 0.1 O 2 also referred to as NCM811
  • lithium nickel cobalt aluminum oxide such as LiNi 0.85 Co 0.15 Al 0.05 O 2
  • Olivine Examples of structural lithium-containing phosphates may include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO 4 , abbreviated as LFP), lithium manganese phosphate (such as LiMnPO 4 ), and lithium manganese iron phosphate.
  • the molecular formula of the active material in the above-mentioned first coated particles and/or the above-mentioned second coated particles is: LiFex Mn (1-x) PO 4 , x can be anywhere from 0 to 1 One count.
  • LiFe x Mn (1-x) PO 4 is LiMnPO 4 lithium manganese phosphate
  • LiFePO 4 is LiFePO 4 lithium iron phosphate
  • the components of the positive electrode active layer also include a positive electrode binder and a positive electrode conductive agent.
  • the mass proportion of the positive electrode binder in the positive electrode active layer is 0.5% to 10%; optionally, the positive electrode
  • the mass proportion of the binder in the positive electrode active layer is 1 to 4%.
  • the mass proportion of the positive electrode conductive agent in the positive electrode active layer is 0.1% to 8%.
  • the positive electrode binder can use various binders commonly used in this field.
  • the positive electrode binder includes polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene tripolymer.
  • Copolymer tetrafluoroethylene-hexafluoropropylene copolymer, fluorine-containing acrylate resin, sodium carboxymethylcellulose, hydroxypropylcellulose, sodium hydroxymethylcellulose, potassium hydroxymethylcellulose, diacetyl fiber
  • fluorine-containing acrylate resin sodium carboxymethylcellulose, hydroxypropylcellulose, sodium hydroxymethylcellulose, potassium hydroxymethylcellulose, diacetyl fiber
  • polyacrylic acid sodium alginate, styrene-butadiene rubber, acrylic butadiene rubber, polypyrrole, polyaniline, epoxy resin and guardo gum.
  • the positive conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.
  • the current collectors in the above-mentioned positive electrode sheets and negative electrode sheets may be current collectors of secondary batteries known in the art.
  • the current collector can be a metal foil or a composite current collector.
  • the composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base material.
  • the composite current collector can be formed by forming metal materials (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as polypropylene (PP), polyterephthalate It is formed on substrates such as ethylene glycol ester (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
  • PP polypropylene
  • PBT polybutylene terephthalate
  • PS polystyrene
  • PE polyethylene
  • the components of the insulating material layer include insulating materials and adhesives.
  • the mass proportion of the insulating material in the insulating material layer is 20% to 95%; optionally, it is preferable that the mass proportion of the insulating material in the insulating material layer is 50% to 75%.
  • the component of the insulating material layer is a mixture of insulating material and adhesive.
  • binders can be well-known binders for secondary batteries in the art, including polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, Ethylene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, fluorine-containing acrylate resin, sodium carboxymethylcellulose, hydroxypropylcellulose, sodium hydroxymethylcellulose , potassium hydroxymethylcellulose, diacetylcellulose, polyacrylic acid, sodium alginate, styrene-butadiene rubber, acrylic butadiene rubber, polypyrrole, polyaniline, and at least one of epoxy resin and guardo gum.
  • PVDF polyvinylidene fluoride
  • PTFE polytetrafluoroethylene
  • PTFE vinylidene flu
  • the above-mentioned insulating material includes at least one of an inorganic insulating material and an organic insulating material.
  • Inorganic insulating materials include at least one of aluminum oxide, silicon oxide, zinc oxide, iron oxide, copper oxide, titanium oxide, mica, asbestos, marble, and ceramics; organic insulating materials can be selected from various types of insulating resins, such as natural rubber, Styrene-butadiene rubber, butadiene rubber and isoprene rubber, etc.
  • the above-mentioned insulating material includes at least one of alumina and styrene-butadiene rubber.
  • the above-mentioned secondary battery further includes a separator, and the separator is disposed between the positive electrode sheet and the negative electrode sheet.
  • the above-mentioned secondary battery further contains an electrolyte.
  • the positive electrode sheet, negative electrode sheet and separator film can be made into an electrode assembly through a winding process or a lamination process.
  • the electrolyte acts as a conductor for ions between the positive and negative electrodes.
  • the above-mentioned electrolytic solution may include electrolyte salts and solvents.
  • the electrolyte salt may be selected from lithium hexafluorophosphate (LiPF 6 ), lithium tetrafluoroborate (LiBF 4 ), lithium perchlorate (LiClO 4 ), lithium hexafluoroarsenate (LiAsF 6 ), lithium bisfluorosulfonyl imide ( LiFSI), lithium bistrifluoromethanesulfonimide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluoromethanesulfonate borate (LiDFOB), lithium dioxalatoborate (LiBOB), lithium difluorophosphate (LiPO 2 F 2 ), one or more of lithium difluorodioxalate phosphate (LiDFOP) and lithium tetrafluorooxalate phosphate (LiTFOP).
  • the above solvent can be selected from the group consisting of ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dicarbonate Propyl ester (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), butylene carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate ( MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), butyl One or more of ethyl acid ester (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS) and
  • additives are also included in the electrolyte.
  • additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain properties of the battery, such as additives that improve the overcharge performance of the battery, additives that improve the high-temperature performance of the battery, and additives that improve the low-temperature performance of the battery. Additives etc.
  • isolation membrane there is no particular restriction on the type of isolation membrane in this application. Any well-known porous structure isolation membrane with good chemical stability and mechanical stability can be used.
  • the material of the isolation membrane can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride, and can also be an isolation membrane with a boehmite coating. , that is, including a porous substrate and a boehmite coating loaded on the surface of the porous substrate.
  • the isolation film can be a single-layer film or a multi-layer composite film, with no special restrictions. When the isolation film is a multi-layer composite film, the materials of each layer can be the same or different, and there is no particular limitation.
  • the secondary battery of the present application is a lithium-ion battery.
  • the preparation of the above-mentioned secondary battery includes the following steps S10 to S30.
  • Step S10 Provide a positive electrode sheet and a separator.
  • the total capacity of the positive electrode sheet is P.
  • Step S20 Form a first negative electrode active layer, an insulating material layer and a second negative electrode active layer sequentially on the surface of the current collector to obtain a negative electrode sheet.
  • the total capacity of the negative electrode sheet is N; where N/P is controlled to ⁇ 1.
  • N gram capacity of negative electrode material ⁇ area density ⁇ mass proportion of negative electrode active material ⁇ size of negative electrode sheet
  • the mass proportion of the negative active material refers to: the mass proportion of the negative active material in the negative active layer
  • the mass proportion of the positive active material refers to: the mass proportion of the positive active material in the positive active layer
  • the negative plate The size refers to the area of the negative electrode sheet loaded with the negative electrode active layer.
  • the size of the positive electrode sheet refers to the area of the positive electrode sheet loaded with the positive electrode active layer.
  • the negative electrode sheet of the present application includes a first negative electrode active layer and a second negative electrode active layer.
  • the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as the positive electrode active material, the positive electrode conductive agent, the positive electrode binder and any other components in a solvent (such as N -methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode current collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.
  • a solvent such as N -methylpyrrolidone
  • the negative electrode sheet can be prepared by dispersing the above-mentioned components for preparing the negative electrode sheet, such as negative active material, negative electrode conductive agent, negative electrode binder and any other components in a solvent (such as N -methylpyrrolidone), form a first negative electrode slurry, and refer to this step to form an insulating slurry and a second negative electrode slurry respectively; apply the first negative electrode slurry on the negative electrode current collector, dry it, and then coat Cold insulating slurry, drying, and finally coating with the second negative electrode slurry. After drying, cold pressing and other processes, the negative electrode sheet can be obtained.
  • a solvent such as N -methylpyrrolidone
  • the secondary battery can be prepared according to conventional methods in this field, for example, the positive electrode sheet, the separator film, and the negative electrode sheet are wound (or stacked) in order, so that the separator film is between the positive electrode sheet and the negative electrode sheet to play an isolation role, and an electrode is obtained. assembly, place the electrode assembly in the outer package, inject electrolyte and seal to obtain a secondary battery.
  • the embodiments of the present application have no particular limitation on the shape of the secondary battery, which may be cylindrical, square, or any other shape.
  • the above-mentioned secondary battery also includes a casing for packaging the positive electrode sheet, the negative electrode sheet, the isolation film and the electrolyte.
  • the above-mentioned outer shell may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. It can also be a soft bag, such as a bag-type soft bag.
  • the material of the soft bag may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, polybutylene succinate, and the like.
  • FIG. 1 shows a square-structured secondary battery 4 as an example.
  • the housing may include a housing 41 and a cover 43 .
  • the housing 41 may include a bottom plate and side plates connected to the bottom plate, and the bottom plate and the side plates enclose a receiving cavity.
  • the housing 41 has an opening communicating with the accommodation cavity, and the cover plate 43 can cover the opening to close the accommodation cavity.
  • the positive electrode sheet, the negative electrode sheet and the separator film can be formed into the electrode assembly 42 through a winding process or a lamination process.
  • the electrode assembly 42 is packaged in the containing cavity.
  • the electrolyte soaks into the electrode assembly 42 .
  • the number of electrode assemblies 42 contained in the battery 4 can be one or more, and can be adjusted according to requirements.
  • This application also provides an electrical device, which includes the above-mentioned secondary battery.
  • the secondary battery may exist in the form of a battery cell or may be further assembled into a battery pack.
  • the battery pack 1 includes a battery box and one or more secondary batteries 4 provided in the battery box.
  • the battery box includes an upper box 2 and a lower box 3 .
  • the upper box 2 can be covered with the lower box 3 and form a closed space for the secondary battery 4 .
  • the plurality of secondary batteries 4 can be arranged in the battery box in any manner.
  • the above-mentioned secondary battery or the battery pack assembled therefrom can be used as a power source for an electrical device, or as an energy storage unit for an electrical device.
  • the above-mentioned electric devices may be, but are not limited to, mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.
  • mobile devices such as mobile phones, laptops, etc.
  • electric vehicles such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf golf carts, electric trucks, etc.
  • electric trains ships and satellites, energy storage systems, etc.
  • FIG. 5 shows an electrical device 5 as an example.
  • the electric device 5 is a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, or the like.
  • a battery pack may be used.
  • the power-consuming device may be a mobile phone, a tablet computer, a laptop computer, etc.
  • the device is usually required to be thin and light, and a battery can be used as a power source.
  • NCM cobalt manganese
  • ternary material LiNi 0.8 Mn 0.1 Co 0.1 O 2
  • conductive agent carbon black conductive agent carbon black
  • PVDF binder polyvinylidene fluoride
  • first active material artificial graphite conductive agent carbon black, binder styrene-butadiene rubber (SBR), and thickener sodium hydroxymethylcellulose (CMC) in a weight ratio of 97:0.5:1.25:1.25, and add deionized water, mix and stir for 6 hours to obtain the first negative electrode slurry; apply it evenly on the 6 ⁇ m thick copper foil of the negative electrode current collector, and dry it to form the first negative electrode active layer.
  • the thickness is recorded as L 0 . Please see Table 1 for details. .
  • the total capacity N of the negative electrode sheet and the total capacity P of the positive electrode sheet can be calculated according to the following calculation formula. Please see Table 1 for the specific N/P value.
  • N Negative active material gram capacity ⁇ area density ⁇ negative electrode ratio ⁇ negative electrode sheet size
  • the mass proportion of the negative active material refers to: the mass proportion of the negative active material in the negative active layer
  • the mass proportion of the positive active material refers to: the mass proportion of the positive active material in the positive active layer
  • the negative plate The size refers to the area of the negative electrode sheet loaded with the negative electrode active layer.
  • the size of the positive electrode sheet refers to the area of the positive electrode sheet loaded with the positive electrode active layer.
  • the above-mentioned negative electrode sheet includes a first negative electrode active layer and a second negative electrode active layer.
  • each layer on the pole piece can be tested using methods known in the art, specifically through the step test method: the step test needle gently scratches the sample surface with very small force, and the sample surface is micron or even nanometer level.
  • the high and low fluctuations are amplified millions of times by the sensor connected to the stylus, then converted into electronic signals, input into the computer software, and finally displayed in the form of numerical and graphical data.
  • Dissolve LiPF 6 in the mixed solvent to prepare an electrolyte solution with a concentration of 1 mol/L.
  • the mixed solvent is formed by mixing ethylene carbonate, ethyl methyl carbonate, and diethyl carbonate in a volume ratio of 1:1:1.
  • a conventional polypropylene (PP) film is used as the isolation film.
  • Embodiment 2 is basically the same as Embodiment 1, except that in step (2) during the preparation of the negative electrode sheet, the active material graphite in the second negative electrode slurry is replaced with graphene, and the total capacity N of the negative electrode sheet is maintained. Same as Example 1.
  • Embodiment 2 is basically the same as Embodiment 1, except that in step (2) during the preparation of the negative electrode sheet, the active material graphite in the second negative electrode slurry is replaced with magnesium oxide, and the total capacity N of the negative electrode sheet is maintained. Same as Example 1.
  • Embodiment 3 is basically the same as Embodiment 1, except that in step (2) during the preparation of the negative electrode sheet, the active material graphite in the first negative electrode slurry is replaced with silicon oxide, L 0 is controlled, and the negative electrode is maintained
  • the total capacity N of the slices is the same as in Example 2.
  • Embodiment 5 is basically the same as Embodiment 1, except that in the preparation process of the negative electrode sheet in step (2), the active material graphite in the first negative electrode slurry is replaced with iron oxide, and the Al 2 in the insulating slurry is replaced. O3 was replaced with equal mass of styrene-butadiene rubber, polyvinylidene fluoride was replaced with sodium carboxymethyl cellulose, and the total capacity N of the negative electrode sheet was kept the same as in Example 2.
  • Embodiment 6 is basically the same as Embodiment 1, except that in step (2) during the preparation of the negative electrode sheet, the Al 2 O 3 in the insulating slurry is replaced with equal masses of Al 2 O 3 and styrene-butadiene rubber. Mixture, in which the mass ratio of Al 2 O 3 to styrene-butadiene rubber is 1:1, polyvinylidene fluoride is replaced with sodium carboxymethyl cellulose, and the total capacity N of the negative electrode sheet is kept the same as in Example 2.
  • Embodiments 7 to 9 are basically the same as Embodiment 1, except that in step (2) during the preparation of the negative electrode sheet, the total capacity of the negative electrode sheet is changed by adjusting the amount of negative active material added in the first active slurry. N, thereby changing the N/P value, and changing the values of L 1 and L 2 accordingly, see Table 1 for details.
  • Embodiments 10 to 13 are basically the same as Embodiment 2, except that in step (2) during the preparation of the negative electrode sheet, the thickness of the second negative electrode active layer is adjusted while ensuring that the capacity N of the negative electrode sheet is basically the same as that in Embodiment 2. , please see Table 1 for details.
  • Embodiment 14 is basically the same as Embodiment 2, except that in the preparation process of the negative electrode sheet in step (2), the second active material graphene, the lithiophilic material ZnO, the binder styrene-butadiene rubber (SBR), and The thickener sodium carboxymethylcellulose (CMC) is mixed according to the weight ratio of 96:3:0.5:0.5, added to deionized water, mixed and stirred for 6 hours to obtain the second negative electrode slurry, while ensuring the capacity N of the negative electrode sheet and the implementation Example 2 is basically the same, see Table 1 for details.
  • SBR binder styrene-butadiene rubber
  • CMC thickener sodium carboxymethylcellulose
  • Comparative Example 1 is basically the same as Example 2, except that in the preparation process of the negative electrode sheet in step (2), only the first negative electrode active layer is formed, and the N/P value in the lithium ion battery is controlled to be 0.6.
  • Comparative Example 2 is basically the same as Example 4, except that in the preparation process of the negative electrode sheet in step (2), only the first negative electrode active layer is formed, and the N/P value in the lithium ion battery is controlled to be 0.6.
  • Comparative Example 3 is basically the same as Example 5, except that in the preparation process of the negative electrode sheet in step (2), only the first negative electrode active layer is formed, and the N/P value in the lithium ion battery is controlled to be 0.6.
  • Comparative Example 4 is basically the same as Example 2, except that during the preparation process of the negative electrode sheet in step (2), the second negative electrode active layer is not formed, and the N/P value of the lithium ion battery is kept the same as that of Example 2.

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Abstract

本申请提出一种二次电池(4)及用电装置，该二次电池(4)包括正极片及负极片，正极片的总容量为P，负极片的总容量为N，N和P满足：N/P<1；负极片包括集流体及依次设于集流体表面的第一负极活性层、绝缘材料层及第二负极活性层。该二次电池(4)兼具高能量密度及优异的循环性能。

Description

二次电池及用电装置 技术领域
本申请涉及电池领域，具体涉及一种二次电池及用电装置。
背景技术
二次电池因其清洁和可再生的特点得到日益广泛的应用，锂离子电池等二次电池主要由正极、负极、隔膜、电解液及外壳五部分组成，主要依靠锂离子在正极和负极之间移动来产生电能，充电时，锂离子或钠离子从正极脱嵌，经过电解质嵌入负极，放电时则相反。
近年来，随着新能源行业的快速发展，人们对电动汽车、电动自行车等新能源交通工具的需求越来大，对其性能要求也越来越高，而二次电池是电动汽车的重要动力来源，因此，人们对二次电池的能量密度、循环性能的要求也越来越高。
随着需求的提升，传统的二次电池的能量密度及循环性能越来越难以满足人们的需求，有待进一步改进。
发明内容
鉴于上述问题，本申请提供一种二次电池及用电装置，该二次电池兼具高能量密度及优异的循环性能。
为了实现上述目的，本申请的第一方面提供了一种二次电池，二次电池包括正极片及负极片，所述正极片的总容量为P，所述负极片的总容量为N，N和P满足：N/P<1；
所述负极片包括集流体及依次设于所述集流体表面的第一负极活性层、绝缘材料层及第二负极活性层。
上述二次电池中，一方面，对二次电池的正极及负极的总容量进行设计控制，控制N/P<1，使正极片中的锂离子的量远大于正极片能够容纳的锂离子量，充电时，部分过量的锂离子会以锂金属的形式沉积在负极片上，从而与负极片上的负极活性材料形成锂金属复合物，锂金属复合物的形成可以提高二次电池的能量密度；另一方面，另一部分过量的锂离子在负极 片析出表面沉积时形成锂枝晶，从而造成电池的短路的问题，通过在负极片的集流体表面依次设置第一负极活性层、绝缘材料层及第二负极活性层，使锂枝晶能够沉积在绝缘材料层与集流体界面之间，设置第二负极活性层吸收包覆从绝缘材料层刺穿出来的锂枝晶，避免负极片表面形成锂枝晶，从而刺穿隔膜造成短路。由此，使二次电池兼具高能量密度及优异的循环性能。
在本申请任意实施方式中，所述绝缘材料层的厚度为L 1μm，所述第二负极活性层的厚度为L 2μm，L 1和L 2满足：L 1＝-16×N/P+17.5，0.01≤L 2/L 1。
根据N/P值的大小设定绝缘材料层的厚度，当N/P值较小时，过量的锂离子越多，负极片沉积的锂枝晶越厚，则控制绝缘材料层的厚度越厚，同时控制绝缘材料层和第二负极活性层的厚度比例，在保证良好的离子传输下，避免负极片表面形成锂枝晶，从而刺穿隔膜造成短路。由此，使二次电池兼具高能量密度及优异的循环性能。
在本申请任意实施方式中，0.01≤L 2/L 1≤0.1；
可选地，0.03≤L 2/L 1≤0.08。
在本申请任意实施方式中，所述绝缘材料层的厚度为0.2μm～15μm；
可选地，所述绝缘材料层的厚度为3.1μm～7.9μm。
在本申请任意实施方式中，所述第一负极活性层的厚度为10μm～300μm；
可选地，所述第一负极活性层的厚度为60μm～200μm。
在本申请任意实施方式中，所述第二负极活性层的组分包括亲锂材料。
二次电池在循环使用过程中，锂枝晶沉积在绝缘材料层与集流体界面之间并不断累积，累积到一定程度就会刺穿绝缘材料层，从而嵌入第二负极活性层与第二负极活性层搭接，一方面，第二负极活性层起到进一步包覆锂枝晶的作用，避免其刺穿隔离膜，另一方面，第二负极活性层中的亲锂材料能进一步与嵌入第二负极活性层的锂枝晶结合，从而吸收锂枝晶，可阻止锂枝晶进一步扩散，达到钝化的目的。
在本申请任意实施方式中，以锂金属为参比电极，亲锂材料的过电位不大于0.03V。
在本申请任意实施方式中，所述亲锂材料选自Au、Ag、Zn、Fe、Co、Ni、Ga、Sn、In、Ge、Ti、Mu、Pt、Al、Mg及其氧化物、硫化物、氟化物、氮化物、氯化物、碳化物中的一种或多种。
在本申请任意实施方式中，所述二次电池满足如下条件a～b中的至少一个：
a、在所述第二负极活性层中，所述亲锂材料的质量占比为0.2％～5％；
可选地，在所述第二负极活性层中，所述亲锂材料的质量占比为0.3％～3％；
b、所述第二负极活性层的过电位为0～0.3V。
在本申请任意实施方式中，所述第一负极活性层的过电位为0.1V～0.6V。
在本申请任意实施方式中，所述第一负极活性层和所述第二负极活性层的组分均包括负极活性材料与金属锂，所述金属锂负载于所述负极活性材料表面。
在本申请任意实施方式中，所述正极片包括集流体及负载于所述集流体表面的正极活性层，所述正极活性层的组分包括锂离子正极活性材料，所述金属锂源自于所述正极片所含的所述锂离子正极活性材料中的锂离子。
在本申请任意实施方式中，所述二次电池满足如下条件c～d中的至少一个：
c、在所述第一负极活性层中，所述负极活性物质的占比为80％～98％；
d、在所述第二负极活性层中，所述负极活性物质的占比为80％～98％。
在本申请任意实施方式中，所述负极活性材料包括中间相碳微球、石墨、玻璃碳、碳纳米管、碳-碳复合材料、碳纤维、硬碳、软炭、硅基材料、镁基材料、锡基材料和铁基材料中的至少一种。
在本申请任意实施方式中，所述绝缘材料层的组分包括绝缘材料及粘结剂。
在本申请任意实施方式中，所述绝缘材料包括有机绝缘材料和无机绝缘材料中的至少一种，所述无机绝缘材料选自氧化铝、氧化硅、氧化锌、氧化铁、氧化铜、氧化钛、云母、石棉、大理石和陶瓷中的至少一种，所 述有机绝缘材料选自天然橡胶、丁苯橡胶、顺丁橡胶和异戊橡胶中的至少一种。
本申请的第二方面提供一种用电装置，所述用电装置包括本申请第一方面的二次电池。
上述说明仅是本申请技术方案的概述，为了能够更清楚了解本申请的技术手段，而可依照说明书的内容予以实施，并且为了让本申请的上述和其它目的、特征和优点能够更明显易懂，以下特举本申请的具体实施方式。
附图说明
通过阅读对下文优选实施方式的详细描述，各种其他的优点和益处对于本领域普通技术人员将变得清楚明了。附图仅用于示出优选实施方式的目的，而并不认为是对本申请的限制。而且在全部附图中，用相同的附图标号表示相同的部件。在附图中：
图1是二次电池的一实施方式的示意图。
图2是图1的分解图。
图3是电池包的一实施方式的示意图。
图4是图3的分解图。
图5是二次电池用作电源的用电装置的一实施方式的示意图。
附图标记说明：
1、电池包；2、上箱体；3、下箱体；4、二次电池；41、壳体；42、电极组件；43、盖板；5、用电装置。
具体实施方式
下面将结合附图对本申请技术方案的实施例进行详细的描述。以下实施例仅用于更加清楚地说明本申请的技术方案，因此只作为示例，而不能以此来限制本申请的保护范围。
除非另有定义，本文所使用的所有的技术和科学术语与属于本申请的技术领域的技术人员通常理解的含义相同；本文中所使用的术语只是为了描述具体的实施例的目的，不是旨在于限制本申请；本申请的说明书和权利要求书及上述附图说明中的术语“包括”和“具有”以及它们的任何变形， 意图在于覆盖不排他的包含。
在本申请实施例的描述中，技术术语“第一”“第二”等仅用于区别不同对象，而不能理解为指示或暗示相对重要性或者隐含指明所指示的技术特征的数量、特定顺序或主次关系。在本申请实施例的描述中，“多个”的含义是两个以上，除非另有明确具体的限定。
在本文中提及“实施例”意味着，结合实施例描述的特定特征、结构或特性可以包含在本申请的至少一个实施例中。在说明书中的各个位置出现该短语并不一定均是指相同的实施例，也不是与其它实施例互斥的独立的或备选的实施例。本领域技术人员显式地和隐式地理解的是，本文所描述的实施例可以与其它实施例相结合。
在本申请实施例的描述中，术语“和/或”仅仅是一种描述关联对象的关联关系，表示可以存在三种关系，例如A和/或B，可以表示：单独存在A，同时存在A和B，单独存在B这三种情况。另外，本文中字符“/”，一般表示前后关联对象是一种“或”的关系。
在本申请实施例的描述中，术语“多个”指的是两个以上(包括两个)，同理，“多组”指的是两组以上(包括两组)，“多片”指的是两片以上(包括两片)。
在本申请实施例的描述中，技术术语“中心”“纵向”“横向”“长度”“宽度”“厚度”“上”“下”“前”“后”“左”“右”“竖直”“水平”“顶”“底”“内”“外”“顺时针”“逆时针”“轴向”“径向”“周向”等指示的方位或位置关系为基于附图所示的方位或位置关系，仅是为了便于描述本申请实施例和简化描述，而不是指示或暗示所指的装置或元件必须具有特定的方位、以特定的方位构造和操作，因此不能理解为对本申请实施例的限制。
在本文的描述中，除非另有说明，术语“或(or)”是包括性的。也就是说，短语“A或(or)B”表示“A，B，或A和B两者”。更具体地，以下任一条件均满足条件“A或B”：A为真(或存在)并且B为假(或不存在)；A为假(或不存在)而B为真(或存在)；或A和B都为真(或存在)。除非另有说明，本申请中使用的术语具有本领域技术人员通常所理解的公知含义。除非另有说明，本申请中提到的各参数的数值可以用本领域常用的各种测量方法进行测量(例如，可以按照在本申请的实施例中给出的方法 进行测试)。
如背景技术所述，随着需求的提升，传统的二次电池的能量密度及循环性能越来越难以满足人们的需求。在锂离子电池等二次电池中，负极(NE)和正极(PE)的容量平衡被认为是一个关键点，一般地，若正极过量，充电过程中由正极脱出的多余的锂离子在负极表面析出形成锂枝晶，容易引发电池内短路，从而影响电池安全性能；而锂枝晶的形成会刺穿隔离膜，从而造成短路引发安全事故。故，传统技术中为了避免析锂以获取良好的安全性，负极一般需要过量设计，即控制负极片和正极片对应面积内的总容量比N/P值＞1。
然而，本申请的技术人员在电池的实际生产研发过程中发现：控制正负极对应面积内的总容量比N/P值＞1时，对锂离子电池等二次电池的能量密度及循环性能的提高有限，难以满足人们对二次电池的能量密度及循环性能越来越高的需求。
基于此，在通过大量探究实验之后，本申请的技术人员另辟蹊径、打破传统技术的禁锢，控制N/P<1，同时对负极片的结构进行设计，在实现高能量密度的同时，避免锂枝晶的产生，使二次电池兼具高能量密度及优异的循环性能。
本申请一实施方式提供了一种二次电池，该二次电池包括正极片及负极片，正极片的总容量为P，负极片的总容量为N，N和P满足：N/P<1。
负极片包括集流体及依次设于集流体表面的第一负极活性层、绝缘材料层及第二负极活性层。
上述二次电池中，一方面，对二次电池的正极及负极的总容量进行设计控制，控制N/P<1，使正极片中的锂离子的量远大于正极片能够容纳的锂离子量，充电时，部分过量的锂离子会以锂金属的形式沉积在负极片上，从而与负极片上的负极活性材料形成锂金属复合物，锂金属复合物的形成可以提高二次电池的能量密度；另一方面，另一部分过量的锂离子在负极片析出表面沉积时形成锂枝晶，从而造成电池的短路的问题，通过在负极片的集流体表面依次设置第一负极活性层、绝缘材料层及第二负极活性层，使锂枝晶能够沉积在绝缘材料层与集流体界面之间，设置第二负极活性层 吸收包覆从绝缘材料层刺穿出来的锂枝晶，避免负极片表面形成锂枝晶，从而刺穿隔膜造成短路。由此，使二次电池兼具高能量密度及优异的循环性能。
在本申请任意实施方式中，绝缘材料层的厚度为L 1μm，第二负极活性层的厚度为L 2μm，L 1和L 2满足：L 1＝-16×N/P+17.5，0.01≤L 2/L 1。
本申请技术人员在经过大量创造性试验，并总结分析后获得：根据N/P值的大小设定绝缘材料层的厚度，当N/P值较小时，过量的锂离子越多，负极片沉积的锂枝晶越厚，则控制绝缘材料层的厚度越厚，同时控制绝缘材料层和第二负极活性层的厚度比例，在保证良好的离子传输下，避免负极片表面形成锂枝晶，从而刺穿隔膜造成短路。由此，使二次电池兼具高能量密度及优异的循环性能。
在本申请任意实施方式中，L 1和L 2满足：0.01≤L 2/L 1≤0.1。
优选地，L 1和L 2满足：0.03≤L 2/L 1≤0.08。
上述“0.01≤L 2/L 1≤0.1”中，L 2/L 1的取值包括该范围的最小值及最大值，以及这种最小值与最大值之间的每一个值，L 2/L 1的具体示例包括但不限于实施例中的点值以及：0.01、0.02、0.03、0.04、0.05、0.06、0.07、0.08、0.09、0.1。
在本申请任意实施方式中，上述绝缘材料层的厚度为0.2μm～15μm。
可选地，上述绝缘材料层的厚度为3.1μm～7.9μm。
上述“0.2μm～15μm”中，取值包括该范围的最小值及最大值，以及这种最小值与最大值之间的每一个值，具体示例包括但不限于实施例中的点值以及：0.2μm、0.3μm、0.5μm、1μm、1.5μm、2μm、2.5μm、3μm、3.5μm、4μm、4.5μm、5μm、5.5μm、6μm、6.5μm、7μm、7.1μm、7.2μm、7.3μm、μm、7.5μm、7.7μm、7.8μm、7.9μm、8μm、8.5μm、9μm、9.5μm、10μm、10.5μm、11μm、11.5μm、12μm、12.5μm、13μm、13.5μm、4μm、14.5μm、15μm。
在本申请任意实施方式中，第一负极活性层的厚度为10μm～300μm。
在本申请任意实施方式中，第一负极活性层的厚度为60μm～200μm。
在本申请任意实施方式中，上述第二负极活性层的组分包括亲锂材料。
二次电池在循环使用过程中，锂枝晶沉积在绝缘材料层与集流体界面之间并不断累积，累积到一定程度就会刺穿绝缘材料层，从而嵌入第二负极活性层与第二负极活性层搭接，一方面，第二负极活性层起到进一步包覆锂枝晶的作用，避免其刺穿隔离膜，另一方面，第二负极活性层中的亲锂材料能进一步与嵌入第二负极活性层的锂枝晶结合，从而吸收锂枝晶，可阻止锂枝晶进一步扩散，达到钝化的目的。
在本申请任意实施方式中，以锂金属为参比电极，亲锂材料的过电位不大于0.03V。
具体的，上述亲锂材料的过电位的测试采用三电极电化学电池测试，以亲锂材料作为工作电极，Li 0.5FePO 4作为参考电极，锂金属作为对电极。具体测试方法如下：
以10μA cm -2的电流密度在工作电极上沉积金属锂。以工作电极相对于Li金属(Li/Li+)的电压为纵坐标，容量为横坐标。当容量提升时，电压呈先下降后持平的趋势，在此过程中，曲线无拐点或拐点对应的纵坐标的电压的绝对值≤0.03V时，说明待测材料具有亲锂性。
在本申请任意实施方式中，亲锂材料选自Au、Ag、Zn、Fe、Co、Ni、Ga、Sn、In、Ge、Ti、Mu、Pt、Al、Mg及其氧化物、硫化物、氟化物、氮化物、氯化物、碳化物中的一种或多种。
在本申请任意实施方式中，在上述第二负极活性层中，亲锂材料的质量占比为0.2％～5％。
在本申请任意实施方式中，在上述第二负极活性层中，亲锂材料的质量占比为0.3％～3％。
在本申请任意实施方式中，以锂金属为参比电极，第二负极活性层的过电位为0～0.3V。
在本申请任意实施方式中，以锂金属为参比电极，第一负极活性层的过电位为0.1V～0.6V。
上述第二负极活性层或第一负极活性层的过电位的测试采用三电极电化学电池测试，以第二负极活性层或第一负极活性层作为工作电极，
Li 0.5FePO 4作为参考电极，锂金属作为对电极。具体测试方法如下：
以10μA cm -2的电流密度在工作电极上沉积金属锂。以工作电极相对 于Li金属(Li/Li+)的电压为纵坐标，容量为横坐标。当容量提升时，电压呈先下降后持平的趋势，在此过程中，曲线拐点对应的纵坐标的电压的绝对值即为过电位。
在本申请任意实施方式中，上述第一负极活性层和上述第二负极活性层的组分均包括负极活性材料与金属锂，金属锂负载于负极活性材料表面。
金属锂负载于负极活性材料表面形成锂金属复合锂物，有利于提高二次电池的能量密度，上述二次电池的能量密度可达到300Wh/kg～600Wh/kg，甚至更高。
在本申请任意实施方式中，在上述第一负极活性层中，负极活性物质的占比为80％～99％。
在本申请任意实施方式中，在上述第一负极活性层中，负极活性物质的占比为88％～98％。
在本申请任意实施方式中，在上述第二负极活性层中，负极活性物质的占比为80％～99％。
在本申请任意实施方式中，在上述第二负极活性层中，负极活性物质的占比为88％～98％。
在本申请任意实施方式中，上述负极活性材料包括中间相碳微球、石墨、玻璃碳、碳纳米管、碳-碳复合材料、碳纤维、硬碳、软炭、硅基材料、锡基材料、镁基材料、和铁基材料中的至少一种。
上述负极活性材料具体示例包括但不限于：间相碳微球、天然石墨、人造石墨、石墨烯、玻璃碳、碳纳米管、碳纤维、硬碳、软炭、氧化铁、氧化锡、氧化硅、氧化镁、硅碳复合物中的至少一种。
在本申请任意实施方式中，第一负极活性层和第二负极活性层的组分均还包括粘结剂。
在本申请任意实施方式中，上述第一负极活性层中粘结剂的占比为0.5％～10％。
在本申请任意实施方式中，上述第一负极活性层中粘结剂的占比为1％～4％。
在本申请任意实施方式中，上述第二负极活性层中粘结剂的占比为0.5％～10％。
在本申请任意实施方式中，上述第二负极活性层中粘结剂的占比为 1％～4％。
在本申请任意实施方式中，第一负极活性层的组分还包括导电剂。
在本申请任意实施方式中，第一负极活性层中导电剂的占比为0.1％～10％。
在本申请任意实施方式中，第一负极活性层中导电剂的占比为0.3％～3％。
作为示例，导电剂可以为超导碳、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几种。
作为示例，粘结剂可以为丁苯橡胶(SBR)、水性丙烯酸树脂(water-based acrylic resin)、聚偏氟乙烯(PVDF)、聚四氟乙烯(PTFE)、乙烯-醋酸乙烯酯共聚物(EVA)、聚乙烯醇(PVA)及聚乙烯醇缩丁醛(PVB)中的一种或几种。
进一步地，上述第一活性层和第二活性层的组分还可以包括增稠剂，作为示例，增稠剂可为羧甲基纤维素钠CMC-Na。
在本申请任意实施方式中，正极片包括集流体及负载于集流体表面的正极活性层，正极活性层在组分包括锂离子正极活性材料，上述金属锂源自于所述正极片所含的所述锂离子正极活性材料中的锂离子。
可理解，上述二次电池中，控制N/P<1，充电过程中，正极片上的正极活性层中锂离子正极活性材料所含的锂离子脱出，而正极片中的锂离子的量远大于正极片能够容纳的锂离子量，部分过量的锂离子会以锂金属的形式沉积在负极片上，从而与负极片上的负极活性材料形成锂金属复合锂物，从而提高二次电池的能量密度。
需要说明的是，可在电池的化成阶段进行充放电使出厂的二次电池的负极片上即具备负极活性材料与锂金属形成锂金属复合锂物，该锂金属复合锂物也可以在后续使用过程中形成。
在本申请任意实施方式中，锂离子正极活性材料在正极活性层中的质量占比为80％～98％。
上述锂离子正极活性材料可采用本领域公知的用于二次电池的锂离子正极活性材料。
作为示例，锂离子正极活性材料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。但本申请并不限定于这些材料，还可以使用其他可被用作电池正极活性材料的传统材料。这些正极活性材料可以仅单独使用一种，也可以将两种以上组合使用。其中，锂过渡金属氧化物的示例可包括但不限于NCM三元材料、锂钴氧化物(如LiCoO 2)、锂镍氧化物(如LiNiO 2)、锂锰氧化物(如LiMnO 2、LiMn 2O 4)、锂镍钴氧化物、锂锰钴氧化物、锂镍锰氧化物、锂镍钴锰氧化物(如LiNi 1/3Co 1/3Mn 1/3O 2(也可以简称为NCM333)、LiNi 0.5Co 0.2Mn 0.3O 2(也可以简称为NCM523)、LiNi 0.5Co 0.2 5Mn 0.25O 2(也可以简称为NCM211)、LiNi 0.6Co 0.2Mn 0.2O 2(也可以简称为NCM622)、LiNi 0.8Co 0.1Mn 0.1O 2(也可以简称为NCM811)、锂镍钴铝氧化物(如LiNi 0.85Co 0.15Al 0.05O 2)及其改性化合物等中的至少一种。橄榄石结构的含锂磷酸盐的示例可包括但不限于磷酸铁锂(如LiFePO 4、简称为LFP)磷酸锰锂(如LiMnPO 4)、磷酸锰铁锂中的至少一种。
在本申请任意实施方式中，上述第一包覆型颗粒和/或上述第二包覆型颗粒中的活性材料的分子式为：LiFe xMn (1-x)PO 4，x取0～1任一数。
可理解，当x取0时，LiFe xMn (1-x)PO 4即为LiMnPO 4磷酸锰锂，当x取1时，LiFePO 4即为LiFePO 4磷酸铁锂。
NCM三元材料结构通式为LiNi x1Co y1Mn z1O 2，x1、y1、z1取0～1任一数，且x1+y1+z1＝1。
在本申请任意实施方式中，正极活性层的组分还包括正极粘结剂和正极导电剂，正极粘结剂在正极活性层中的质量占比为0.5％～10％；可选地，正极粘结剂在正极活性层中的质量占比为1～4％。
可选地，正极导电剂在正极活性层中的质量占比为0.1％～8％。
正极粘结剂可采用本领域常用的各类粘结剂。作为示例，正极粘结剂包括聚偏氟乙烯(PVDF)、聚四氟乙烯(PTFE)、偏氟乙烯-四氟乙烯-丙烯三元共聚物、偏氟乙烯-六氟丙烯-四氟乙烯三元共聚物、四氟乙烯-六氟丙烯共聚物、含氟丙烯酸酯树脂、羧甲基纤维素钠、羟丙基纤维素、羟甲基纤维素钠、羟甲基纤维素钾、双乙酰纤维素、聚丙烯酸、海藻酸钠、丁苯 橡胶、丙烯酸丁二烯橡胶、聚吡咯、聚苯胺和环氧树脂和瓜尔多胶中的至少一种。
作为示例，正极导电剂可以包括超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯及碳纳米纤维中的至少一种。
上述正极片及负极片中的集流体可采用本领域公知的二次电池的集流体。
集流体可采用金属箔片或复合集流体。例如，作为金属箔片，可以采用铜箔。复合集流体可包括高分子材料基层和形成于高分子材料基材至少一个表面上的金属层。复合集流体可通过将金属材料(铜、铜合金、镍、镍合金、钛、钛合金、银及银合金等)形成在高分子材料基材(如聚丙烯(PP)、聚对苯二甲酸乙二醇酯(PET)、聚对苯二甲酸丁二醇酯(PBT)、聚苯乙烯(PS)、聚乙烯(PE)等的基材)上而形成。
在本申请任意实施方式中，绝缘材料层的组分包括绝缘材料及粘结剂。
在本申请任意实施方式中，绝缘材料在绝缘材料层中的质量占比为20％～95％；可选地，优选为绝缘材料在绝缘材料层中的质量占比为50％～75％。
进一步的，绝缘材料层的组分为绝缘材料和粘结剂的混合物。
上述粘结剂可采用本领域公知的二次电池用粘结剂，包括聚偏氟乙烯(PVDF)、聚四氟乙烯(PTFE)、偏氟乙烯-四氟乙烯-丙烯三元共聚物、偏氟乙烯-六氟丙烯-四氟乙烯三元共聚物、四氟乙烯-六氟丙烯共聚物、含氟丙烯酸酯树脂、羧甲基纤维素钠、羟丙基纤维素、羟甲基纤维素钠、羟甲基纤维素钾、双乙酰纤维素、聚丙烯酸、海藻酸钠、丁苯橡胶、丙烯酸丁二烯橡胶、聚吡咯、聚苯胺和环氧树脂和瓜尔多胶中的至少一种。
在本申请任意实施方式中，上述绝缘材料包括无机绝缘材料和有机绝缘材料中的至少一种。无机绝缘材料包括氧化铝、氧化硅、氧化锌、氧化铁、氧化铜、氧化钛、云母、石棉、大理石、陶瓷中的至少一种；有机绝缘材料可选自各类绝缘树脂，例如天然橡胶、丁苯橡胶、顺丁橡胶和异戊 橡胶等。
在本申请任意实施方式中，上述绝缘材料包括氧化铝和丁苯橡胶中的至少一种。
在本申请任意实施方式中，上述二次电池还包括隔离膜，隔离膜设于正极片和负极片之间。
在本申请任意实施方式中，上述二次电池还包电解液。
正极片、负极片和隔离膜可通过卷绕工艺或叠片工艺制成电极组件。电解液在正极和负极之间起到传导离子的作用。
上述电解液可以包括电解质盐和溶剂。作为示例，电解质盐可选自六氟磷酸锂(LiPF 6)、四氟硼酸锂(LiBF 4)、高氯酸锂(LiClO 4)、六氟砷酸锂(LiAsF 6)、双氟磺酰亚胺锂(LiFSI)、双三氟甲磺酰亚胺锂(LiTFSI)、三氟甲磺酸锂(LiTFS)、二氟草酸硼酸锂(LiDFOB)、二草酸硼酸锂(LiBOB)、二氟磷酸锂(LiPO 2F 2)、二氟二草酸磷酸锂(LiDFOP)及四氟草酸磷酸锂(LiTFOP)中的一种或几种。
作为示例，上述溶剂可选自碳酸亚乙酯(EC)、碳酸亚丙酯(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)、碳酸亚丁酯(BC)、氟代碳酸亚乙酯(FEC)、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)、丁酸乙酯(EB)、1,4-丁内酯(GBL)、环丁砜(SF)、二甲砜(MSM)、甲乙砜(EMS)及二乙砜(ESE)中的一种或几种。
在一些实施方式中，电解液中还包括添加剂。例如添加剂可以包括负极成膜添加剂，也可以包括正极成膜添加剂，还可以包括能够改善电池某些性能的添加剂，例如改善电池过充性能的添加剂、改善电池高温性能的添加剂、改善电池低温性能的添加剂等。
本申请对隔离膜的种类没有特别的限制，可以选用任意公知的具有良好的化学稳定性和机械稳定性的多孔结构隔离膜。
在一些实施方式中，隔离膜的材质可选自玻璃纤维、无纺布、聚乙烯、 聚丙烯及聚偏二氟乙烯中的至少一种，还可以是具有勃姆石类涂层的隔离膜，即包括多孔基材及负载在多孔基材表面的勃姆石涂层。隔离膜可以是单层薄膜，也可以是多层复合薄膜，没有特别限制。在隔离膜为多层复合薄膜时，各层的材料可以相同或不同，没有特别限制。
在一些实施方式中，本申请的二次电池为锂离子电池。
上述二次电池的制备包括如下步骤S10～S30。
步骤S10、提供正极片及隔离膜，正极片的总容量为P。
步骤S20、在集流体表面依次形成第一负极活性层、绝缘材料层及第二负极活性层，得到负极片，负极片的总容量为N；其中，控制N/P<1。
可理解，通过对正极片及负极片的总容量极性设计，以控制两者的比值，可依照下述计算公式设计：
N＝负极材料克容量×面密度×负极活性材料的质量占比×负极片尺寸
P＝正极材料克容量×面密度×正极活性材料的质量占比×正极片尺寸
其中，负极活性材料的质量占比是指：负极活性材料在负极活性层中的质量占比，正极活性材料的质量占比是指：正极活性材料在正极活性层中的质量占比；负极片尺寸是指负极片中负载有负极活性层的面积，同理，正极片尺寸是指正极片中负载有正极活性层的面积。
进一步地，本申请的负极片中包括第一负极活性层和第二负极活性层，按照上述负极片的容量计算公式分别计算第一负极活性层和第二负极活性层对应的容量N1和N2，则负极片的总容量N＝N1+N2。
在一些实施方式中，可以通过以下方式制备正极片：将上述用于制备正极片的组分，例如正极活性材料、正极导电剂、正极粘结剂和任意其他的组分分散于溶剂(例如N-甲基吡咯烷酮)中，形成正极浆料；将正极浆料涂覆在正极集流体上，经烘干、冷压等工序后，即可得到正极片。
步骤S20中，绝缘材料层的厚度为L 1μm；第二负极活性层的厚度为L 2μm；控制L 1＝-16×N/P+17.5，0.01≤L 2/L 1。
在一些实施方式中，可以通过以下方式制备负极片：将上述用于制备负极片的组分，例如负极活性材料、负极导电剂、负极粘结剂和任意其他 的组分分散于溶剂(例如N-甲基吡咯烷酮)中，形成第一负极浆料，并参照该步骤分别形成绝缘浆料及第二负极浆料；将第一负极浆料涂覆在负极集流体上、烘干，然后涂覆冷绝缘浆料、烘干，最后涂覆第二负极浆料，经烘干、冷压等工序后，即可得到负极片。
可以按照本领域常规方法制备二次电池，例如将正极片、隔离膜、负极片按顺序卷绕(或叠片)，使隔离膜处于正极片与负极片之间起到隔离的作用，得到电极组件，将电极组件置于外包装中，注入电解液并封口，得到二次电池。本申请实施例对二次电池的形状没有特别的限制，其可以是圆柱形、方形或其他任意的形状。
上述二次电池还包括外壳，用于包装正极片、负极片、隔离膜及电解液。
在本申请任意实施例中，上述外壳的可以是硬壳，例如硬塑料壳、铝壳、钢壳等。也可以是软包，例如袋式软包。软包的材质可以是塑料，作为塑料，可列举出聚丙烯、聚对苯二甲酸丁二醇酯以及聚丁二酸丁二醇酯等。
本申请对二次电池的形状没有特别的限制，其可以是圆柱形、方形或其他任意的形状。例如，图1是作为一个示例的方形结构的二次电池4。
在一些实施例中，参照图2，外壳可包括壳体41和盖板43。其中，壳体41可包括底板和连接于底板上的侧板，底板和侧板围合形成容纳腔。壳体41具有与容纳腔连通的开口，盖板43能够盖设于所述开口，以封闭所述容纳腔。
正极片、负极片和隔离膜可经卷绕工艺或叠片工艺形成电极组件42。电极组件42封装于容纳腔。电解液浸润于电极组件42中。电池4所含电极组件42的数量可以为一个或多个，可根据需求来调节。
本申请还提供一种用电装置，该用电装置包括上述的二次电池。
进一步地，在上述用电装置中，二次电池可以电池单体的形式存在，也可以进一步组装成电池包的形式存在。
图3和图4是作为一个示例的电池包1。在电池包1中包括电池箱和 设置于电池箱中的一个或多个二次电池4。电池箱包括上箱体2和下箱体3，上箱体2能够盖设于下箱体3，并形成用于二次电池4的封闭空间。
多个二次电池4可以按照任意的方式排布于电池箱中。
上述二次电池或其组装成的电池包可以用作用电装置的电源，也可以作为用电装置的能量存储单元。
上述用电装置可以但不限于是移动设备(例如手机、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。
图5是作为一个示例的用电装置5。该用电装置5为纯电动车、混合动力电动车、或插电式混合动力电动车等。为了满足该用电装置5对二次电池的高功率和高能量密度的需求，可以采用电池包形式。
作为另一个示例的用电装置可以是手机、平板电脑、笔记本电脑等。该装置通常要求轻薄化，可以采用电池作为电源。
下面将结合具体的实施例对本发明进行了说明，但本发明并不局限于下述实施例，应当理解，所附权利要求概括了本发明的范围，在本发明构思的引导下本领域的技术人员应意识到，对本发明的各实施例所进行的一定的改变，都将被本发明的权利要求书的精神和范围所覆盖。
以下为具体实施例。
具体实施例
实施例1
(1)正极片的制备
将钴锰(NCM)三元材料(LiNi 0.8Mn 0.1Co 0.1O 2)、导电剂碳黑、粘结剂聚偏二氟乙烯(PVDF)按质量比为97：1：2混合，加入N-甲基吡咯烷酮，混合搅拌6h，得到正极浆料，之后将其均匀涂覆于13μm厚的铝箔表面，经烘干、冷压、形成正极活性层，分切后得到正极片。
(2)负极片的制备
将第一活性物质人造石墨、导电剂碳黑、粘结剂丁苯橡胶(SBR)、增 稠剂羟甲基纤维素钠(CMC)按照重量比为97：0.5：1.25：1.25，加入去离子水，混合搅拌6h，得到第一负极浆料；将其均匀涂覆在负极集流体6μm厚的铜箔上，烘干，形成第一负极活性层，厚度记为L 0，具体请见表1。
将聚偏氟乙烯、Al 2O 3按照重量比1：1混合，加入N-甲基吡咯烷酮，混合搅拌06h，得到绝缘浆料，然后在第一负极活性层表面均匀涂覆绝缘浆料，烘干，形成绝缘材料层，厚度记为L 1。具体请见表1。
将第二活性物质石墨、粘结剂丁苯橡胶(SBR)、增稠剂羟甲基纤维素钠(CMC)，按照重量比为1：0.5：0.5混合，加入去离子水中，混合搅拌6h，得到第二负极浆料，将其均匀涂覆在绝缘材料层片表面，烘干，形成第二负极活性层，厚度记为L 2。
其中，可依照下述计算公式计算负极片的总容量N及正极片的总容量P，具体的N/P值请见表1。
N＝负极活性材料克容量×面密度×负极占比×负极片尺寸
P＝正极活性材料克容量×面密度×正极占比×正极片尺寸
其中，负极活性材料的质量占比是指：负极活性材料在负极活性层中的质量占比，正极活性材料的质量占比是指：正极活性材料在正极活性层中的质量占比；负极片尺寸是指负极片中负载有负极活性层的面积，同理，正极片尺寸是指正极片中负载有正极活性层的面积。
上述负极片中包括第一负极活性层和第二负极活性层，按照上述负极片的容量计算公式分别计算第一负极活性层和第二负极活性层对应的容量N1和N2，则负极片的总容量N＝N1+N2。
极片上各个层的厚度可以选用本领域已知的方法进行测试，具体通过台阶仪测试方法进行测试：台阶仪的测针以十分微小的力轻轻划过样品表面，样品表面微米甚至纳米级别的高低起伏通过与测针连接的传感器得到千百万倍的放大，然后被转换成电子信号，输入到电脑软件中，最终以数字和图形的数据形式展现出来。
(3)电解液的制备
将LiPF 6溶于混合溶剂中，配置成浓度为1mol/L的电解液。混合溶剂 采用碳酸乙烯酯、碳酸甲乙酯、碳酸二乙酯按照体积比1：1：1混合形成。
(4)隔离膜的制备
以常规的聚丙烯(PP)膜作为隔离膜。
(5)锂离子电池的制备
将上述正极片、隔离膜、负极片按顺序叠好，得到裸电芯；将裸电芯置于包装壳中，干燥后注入电解液，经过真空封装、静置、化成、整形等工序，得到锂离子电池。
(6)对制得的锂离子电池的性能进行测试，包括如下：
1、锂离子电池的能量密度测试
在25℃下，以0.33C倍率恒流充电至电压为4.25V，之后以4.25V恒压充电至电流为0.05C，此时锂离子电池达到满充状态，之后静置5min，以0.33C倍率恒流放电至电压为2.8V，再静置5min，记录锂离子电池0.33C倍率恒流放电时的容量和电压平台，最后测量锂离子电池的质量。
二次电池的能量密度(Wh/kg)＝(锂离子电池0.33倍率恒流放电时的容量×锂离子电池0.33C倍率恒流放电时的电压平台)/锂离子电池的质量。
2、锂离子电池于25℃下的循环寿命测试
在25℃下，以1C倍率电流恒流充电至4.25V时，转恒压充电，至充电电流降至0.05C倍率电流时停止充电，然后以1C倍率电流恒流放电至2.8V时停止放电，此时循环圈数为1；重复进行充放电循环至电池容量降至初始容量的80％时停止测试，以此时的锂离子电池的循环圈数作为二次电池的25℃循环寿命。
具体结果请见表1。
实施例2
实施例2与实施例1基本相同，不同之处在于：步骤(2)负极片的制备过程中，将第二负极浆料中的活性物质石墨替换成石墨烯，并保持负极片的总容量N与实施例1相同。
其余步骤与实施例1相同，具体参数及测试结果请见表1。
实施例3
实施例2与实施例1基本相同，不同之处在于：步骤(2)负极片的制备过程中，将第二负极浆料中的活性物质石墨替换成氧化镁，并保持负极片的总容量N与实施例1相同。
其余步骤与实施例1相同，具体参数及测试结果请见表1。
实施例4
实施例3与实施例1基本相同，不同之处在于：步骤(2)负极片的制备过程中，将第一负极浆料中的活性物质石墨替换成硅氧化物，调控L 0，并保持负极片的总容量N与实施例2相同。
其余步骤与实施例2相同，具体参数及测试结果请见表1。
实施例5
实施例5与实施例1基本相同，不同之处在于：步骤(2)负极片的制备过程中，将第一负极浆料中的活性物质石墨替换成氧化铁，将绝缘浆料中的Al 2O 3替换成等质量丁苯橡胶，聚偏氟乙烯替换成羧甲基纤维素钠，并保持负极片的总容量N与实施例2相同。
其余步骤与实施例2相同，具体参数及测试结果请见表1。
实施例6
实施例6与实施例1基本相同，不同之处在于：步骤(2)负极片的制备过程中，将绝缘浆料中的Al 2O 3替换成等质量的Al 2O 3与丁苯橡胶的混合物，其中Al 2O 3与丁苯橡胶的质量比为1:1，聚偏氟乙烯替换成羧甲基纤维素钠，并保持负极片的总容量N与实施例2相同。
其余步骤与实施例2相同，具体参数及测试结果请见表1。
实施例7～9
实施例7～9与实施例1基本相同，不同之处在于：步骤(2)负极片的制备过程中，通过调节第一活性浆料中负极活性物质的添加量，以改变负极片的总容量N，从而改变N/P值，并相应地改变L 1和L 2的值，具体请见表1。
其余步骤与实施例2相同，具体参数及测试结果请见表1。
实施例10～13
实施例10～13与实施例2基本相同，不同之处在于：步骤(2)负极片的制备过程中，调节第二负极活性层的厚度，同时保证负极片的容量N与实施例2基本相同，具体请见表1。
其余步骤与实施例1相同，具体参数及测试结果请见表1。
实施例14
实施例14与实施例2基本相同，不同之处在于：步骤(2)负极片的制备过程中，将第二活性物质石墨烯、亲锂材料ZnO、粘结剂丁苯橡胶(SBR)、增稠剂羟甲基纤维素钠(CMC)，按照重量比为96：3：0.5：0.5混合，加入去离子水中，混合搅拌6h，得到第二负极浆料，同时保证负极片的容量N与实施例2基本相同，具体请见表1。
其余步骤与实施例1相同，具体参数及测试结果请见表1。
对比例1
对比例1与实施例2基本相同，不同之处在于：步骤(2)负极片的制备过程中，只形成第一负极活性层，控制锂离子电池中的N/P值为0.6。
其余步骤与实施例2相同，具体参数及测试结果请见表1。
对比例2
对比例2与实施例4基本相同，不同之处在于：步骤(2)负极片的制备过程中，只形成第一负极活性层，控制锂离子电池中的N/P值为0.6。
其余步骤与实施例4相同，具体参数及测试结果请见表1。
对比例3
对比例3与实施例5基本相同，不同之处在于：步骤(2)负极片的制备过程中，只形成第一负极活性层，控制锂离子电池中的N/P值为0.6。
其余步骤与实施例5相同，具体参数及测试结果请见表1。
对比例4
对比例4与实施例2基本相同，不同之处在于：步骤(2)负极片的制备过程中，不形成第二负极活性层，并保持锂离子电池的N/P值与实施例2相同。
其余步骤与实施例2相同，具体参数及测试结果请见表1。
各实施例及对比例中相关的参数及测试结果请见表1。
表1
Figure PCTCN2022114857-appb-000001
Figure PCTCN2022114857-appb-000002
其中，“/”代表不存在该结构或该物质。
由表1中数据可知：按照本申请的技术制得的二次电池兼具较高的能量密度及优异的循环性能。
最后应说明的是：以上各实施例仅用以说明本申请的技术方案，而非对其限制；尽管参照前述各实施例对本申请进行了详细的说明，本领域的普通技术人员应当理解：其依然可以对前述各实施例所记载的技术方案进行修改，或者对其中部分或者全部技术特征进行等同替换；而这些修改或者替换，并不使相应技术方案的本质脱离本申请各实施例技术方案的范围，其均应涵盖在本申请的权利要求和说明书的范围当中。尤其是，只要不存在结构冲突，各个实施例中所提到的各项技术特征均可以任意方式组合起来。本申请并不局限于文中公开的特定实施例，而是包括落入权利要求的范围内的所有技术方案。

Claims (17)

  1. 一种二次电池，其特征在于，所述二次电池包括正极片及负极片，所述正极片的总容量为P，所述负极片的总容量为N，N和P满足：N/P<1；
    所述负极片包括集流体及依次设于所述集流体表面的第一负极活性层、绝缘材料层及第二负极活性层。
  2. 如权利要求1所述的二次电池，其特征在于，所述绝缘材料层的厚度为L 1，单位为μm，所述第二负极活性层的厚度为L 2，单位为μm，L 1和L 2满足：L 1＝-16×N/P+17.5，0.01≤L 2/L 1。
  3. 如权利要求2所述的二次电池，其特征在于，L 1和L 2满足：0.01≤L 2/L 1≤0.1；
    可选地，L 1和L 2满足：0.03≤L 2/L 1≤0.08。
  4. 如权利要求1～3任一项所述二次电池，其特征在于，所述绝缘材料层的厚度为0.2μm～15μm；
    可选地，所述绝缘材料层的厚度为3.1μm～7.9μm。
  5. 如权利要求1～4任一项所述二次电池，其特征在于，所述第一负极活性层的厚度为10μm～300μm；
    可选地，所述第一负极活性层的厚度为60μm～200μm。
  6. 如权利要求1～5任一项所述的二次电池，其特征在于，所述第二负极活性层的组分包括亲锂材料。
  7. 如权利要求6所述的二次电池，其特征在于，以锂金属为参比电极，所述亲锂材料的过电位不大于0.03V。
  8. 如权利要求6～7任一项所述的二次电池，其特征在于，所述亲锂材料选自Au、Ag、Zn、Fe、Co、Ni、Ga、Sn、In、Ge、Ti、Mu、Pt、Al、Mg及其氧化物、硫化物、氟化物、氮化物、氯化物、碳化物中的一种或多种。
  9. 如权利要求6～8任一项所述的二次电池，其特征在于，所述二次电池满足如下条件a～b中的至少一个：
    a、在所述第二负极活性层中，所述亲锂材料的质量占比为0.2％～5％；
    可选地，在所述第二负极活性层中，所述亲锂材料的质量占比为0.3％～3％；
    b、以锂金属为参比电极，所述第二负极活性层的过电位为0～0.3V。
  10. 如权利要求1～9任一项所述的二次电池，其特征在于，以锂金属为参比电极，所述第一负极活性层的过电位为0.1V～0.6V。
  11. 如权利要求1～10任一项所述的二次电池，其特征在于，所述第一负极活性层和所述第二负极活性层的组分均包括负极活性材料与金属锂，所述金属锂负载于所述负极活性材料表面。
  12. 如权利要求11所述的二次电池，其特征在于，所述正极片包括集流体及负载于所述集流体表面的正极活性层，所述正极活性层的组分包括锂离子正极活性材料，所述金属锂源自于所述正极片所含的所述锂离子正极活性材料中的锂离子。
  13. 如权利要求11～12任一项所述的二次电池，其特征在于，所述二次电池满足如下条件c～d中的至少一个：
    c、在所述第一负极活性层中，所述负极活性物质的占比为80％～98％；
    d、在所述第二负极活性层中，所述负极活性物质的占比为80％～98％。
  14. 如权利要求11～13任一项所述的二次电池，其特征在于，所述负极活性材料包括中间相碳微球、石墨、玻璃碳、碳纳米管、碳-碳复合材料、碳纤维、硬碳、软炭、硅基材料、锡基材料和铁基材料中的至少一种。
  15. 如权利要求1～14任一项所述的二次电池，其特征在于，所述绝缘材料层的组分包括绝缘材料及粘结剂。
  16. 如权利要求15所述的二次电池，其特征在于，所述绝缘材料包括有机绝缘材料和无机绝缘材料中的至少一种，所述无机绝缘材料选自氧化铝、氧化硅、氧化锌、氧化铁、氧化铜、氧化钛、云母、石棉、大理石和陶瓷中的至少一种，所述有机绝缘材料选自天然橡胶、丁苯橡胶、顺丁橡胶和异戊橡胶中的至少一种。
  17. 一种用电装置，其特征在于，所述用电装置包括如权利要求1至16任一项所述的二次电池。
PCT/CN2022/114857 2022-08-25 2022-08-25 二次电池及用电装置 WO2024040525A1 (zh)

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CN102201565A (zh) * 2011-04-14 2011-09-28 杭州万好万家动力电池有限公司 一种高容量金属锂粉复合负极及制备方法和多层复合电极
CN110993890A (zh) * 2019-12-16 2020-04-10 东莞维科电池有限公司 一种负极极片、其制备方法和用途
US20200251728A1 (en) * 2017-10-20 2020-08-06 Lg Chem, Ltd. Long-life and ultra-high energy density lithium secondary battery
CN112234165A (zh) * 2020-11-23 2021-01-15 珠海冠宇电池股份有限公司 负极片和锂离子电池
CN114050231A (zh) * 2021-11-12 2022-02-15 珠海冠宇电池股份有限公司 一种负极片和锂离子电池

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Publication number Priority date Publication date Assignee Title
CN102201565A (zh) * 2011-04-14 2011-09-28 杭州万好万家动力电池有限公司 一种高容量金属锂粉复合负极及制备方法和多层复合电极
US20200251728A1 (en) * 2017-10-20 2020-08-06 Lg Chem, Ltd. Long-life and ultra-high energy density lithium secondary battery
CN110993890A (zh) * 2019-12-16 2020-04-10 东莞维科电池有限公司 一种负极极片、其制备方法和用途
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