WO2021023135A1 - 正极极片及其相关的电化学储能装置和设备 - Google Patents

正极极片及其相关的电化学储能装置和设备 Download PDF

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WO2021023135A1
WO2021023135A1 PCT/CN2020/106471 CN2020106471W WO2021023135A1 WO 2021023135 A1 WO2021023135 A1 WO 2021023135A1 CN 2020106471 W CN2020106471 W CN 2020106471W WO 2021023135 A1 WO2021023135 A1 WO 2021023135A1
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positive electrode
overcharge
pole piece
conductive material
conductive
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PCT/CN2020/106471
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English (en)
French (fr)
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於洋
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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 EP20850999.2A priority Critical patent/EP3905395A4/en
Publication of WO2021023135A1 publication Critical patent/WO2021023135A1/zh
Priority to US17/511,059 priority patent/US20220109159A1/en

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/621—Binders
    • H01M4/622—Binders being polymers
    • 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
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/4235—Safety or regulating additives or arrangements in electrodes, separators or electrolyte
    • 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
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • 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
    • H01M4/621—Binders
    • H01M4/622—Binders being polymers
    • H01M4/623—Binders being polymers fluorinated polymers
    • 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
    • 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
    • H01M4/626—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
    • H01M4/64—Carriers or collectors
    • H01M4/66—Selection of materials
    • H01M4/665—Composites
    • H01M4/667—Composites in the form of layers, e.g. coatings
    • 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
    • H01M4/64—Carriers or collectors
    • H01M4/66—Selection of materials
    • H01M4/668—Composites of electroconductive material and synthetic resins
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • 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
    • H01M2004/028—Positive electrodes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • This application relates to the field of electrochemistry, in particular to a positive pole piece and related electrochemical energy storage devices and equipment.
  • Lithium ion secondary batteries mainly rely on the reciprocating movement of lithium ions between the positive electrode active material and the negative electrode active material for charging and discharging.
  • Lithium-ion secondary batteries can provide stable voltage and current during use, and the use process is green and environmentally friendly, so they are widely used in various electrical equipment, such as mobile phones, tablet computers, notebook computers, electric bicycles, electric cars, etc. .
  • the purpose of this application is to provide a positive pole piece and its related electrochemical energy storage device and equipment to solve the problems in the prior art.
  • a positive electrode sheet which includes a positive electrode current collector, a positive electrode active material layer on at least one side of the positive electrode current collector, and a positive electrode active material layer located between the positive electrode active material layer and the positive electrode current collector.
  • the overcharge sensitive substance is a polymer that includes a monosaccharide structural unit and includes at least one of a carbonate group and a phosphate group;
  • the unit of x is nm, and the unit of y is 1.
  • Another aspect of the present application provides an electrochemical energy storage device, including the above-mentioned positive pole piece.
  • the positive pole piece provided in this application can be used to form an electrochemical energy storage device.
  • the electrochemical energy storage device When the electrochemical energy storage device is charged, if overcharge and abuse occur, lower temperature will cause the overcharge sensitive material to undergo chemical reaction and degradation , which in turn causes the physical structure of the material to change, causes the conductive material particles in the safety layer to separate, destroys the conductive network in the safety layer, increases the internal resistance of the electrochemical energy storage device, and blocks the positive electrode current collector and the positive electrode activity
  • the electronic conduction between the material layers cuts off the charging current in time, effectively preventing thermal runaway of the electrochemical energy storage device, avoiding safety problems such as fire and explosion, and improving the overcharge safety performance of the electrochemical energy storage device.
  • the reliability is difficult to guarantee, and there is a potential safety hazard.
  • the safety layer using the overcharge-sensitive material provided in the present application has better reliability, and thus can make the electrochemical energy storage device have better safety.
  • the present application provides a battery module including the above electrochemical energy storage device.
  • the present application provides a battery pack including the above-mentioned battery module.
  • the present application provides a device including the above-mentioned electrochemical energy storage device.
  • the electrochemical energy storage device can be used as a power source for the device or as an energy storage unit of the device.
  • the battery module, battery pack, and equipment of the present application include the electrochemical energy storage device provided in the present application, and thus have at least the same advantages as the electrochemical energy storage device of the present application.
  • FIG. 1 is a schematic diagram of voltage and temperature changes in the overcharge safety performance test of one of the batteries in Embodiment 13 of this application;
  • Figure 2 is a schematic diagram of voltage and temperature changes in the overcharge safety performance test of one of the batteries in Comparative Example 2 of the application;
  • Fig. 3 is a schematic diagram of an embodiment of a secondary battery
  • FIG. 4 is a schematic diagram of an embodiment of a battery module
  • FIG. 5 is a schematic diagram of an embodiment of the battery pack
  • Figure 6 is an exploded view of Figure 5;
  • Fig. 7 is a schematic diagram of an embodiment of a device in which a secondary battery is used as a power source.
  • any lower limit may be combined with any upper limit to form an unspecified range; and any lower limit may be combined with other lower limits to form an unspecified range, and any upper limit may 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. Therefore, each point or single numerical value can be used as its own lower limit or upper limit, combined with any other point or single numerical value, or combined with other lower or upper limits to form an unspecified range.
  • the first aspect of the application provides a positive electrode sheet, which includes a positive electrode current collector, a positive electrode active material layer on at least one side of the positive electrode current collector, and a safety layer between the positive electrode active material layer and the positive electrode current collector;
  • the positive electrode active material layer includes Positive active material
  • the safety layer includes binding material, conductive material and overcharge sensitive material;
  • the overcharge sensitive substance includes a monosaccharide structural unit, and includes at least one of a carbonate group and a phosphate group;
  • the average particle size x of the conductive material and the weight average molecular weight y of the overcharge sensitive material satisfy formula 1;
  • the unit of x is nm, and the unit of y is 1.
  • the positive pole piece provided in this application can be used to form an electrochemical energy storage device.
  • the overcharge-sensitive material in the safety layer can be under certain conditions (for example, excessive temperature, Voltage and other conditions) chemical reaction occurs, and the carbohydrate unit fragments containing carbonate groups and/or phosphate groups produced by degradation can be quickly miscible in electrolytes containing a large amount of carbonate solvents, changing from large molecular chains that are difficult to move freely into The freely movable small molecule solution or sol state pushes the conductive materials in the security layer to move together, destroying the conductive network in the security layer.
  • the ability of overcharge sensitive materials to promote the disintegration of the conductive network when it breaks and degrades is a protection
  • the inventor of the present application unexpectedly discovered that when the molecular weight of the overcharge sensitive material and the particle size of the conductive material used in the security layer meet a certain matching relationship, the above effect can be well exerted.
  • the average particle size x of the conductive material and the weight average molecular weight y of the overcharge sensitive material may satisfy the relationship of x/y ⁇ 0.25 (the unit of x is nm and the unit of y is 1).
  • the average particle size of the conductive material usually refers to the particle size of the conductive material coated in the security layer, and the average particle size is obtained through the observation of the electron microscope.
  • the average particle size is obtained through the observation of the electron microscope.
  • For non-spherical particles take the major axis diameter and The average value of the minor axis diameter is the average particle diameter.
  • the average particle diameter x of the conductive material and the weight average molecular weight y of the overcharge sensitive material can satisfy 0.001 ⁇ x/y ⁇ 0.25, 0.001 ⁇ x/y ⁇ 0.005, 0.005 ⁇ x/y ⁇ 0.01, 0.01 ⁇ x/y ⁇ 0.05, 0.05 ⁇ x/y ⁇ 0.1, 0.1 ⁇ x/y ⁇ 0.15, 0.15 ⁇ x/y ⁇ 0.2, or 0.2 ⁇ x/y ⁇ 0.25.
  • the conductive material with a smaller average particle size x is more likely to shift and disconnect the conductive network when the overcharge-sensitive material breaks; therefore, for the conductive material itself, it is possible to choose a higher Small particle size.
  • the average particle size x of the conductive material may satisfy: x ⁇ 600nm, x ⁇ 500nm, x ⁇ 400nm, x ⁇ 300nm, x ⁇ 200nm, or x ⁇ 100nm.
  • the overcharge sensitive material with a large weight average molecular weight y can have a stronger driving effect on the disconnection of the conductive network when it is broken; the overcharge sensitive material with too low weight average molecular weight y Substances may result in the inability to stabilize the conductive network during normal use; overcharge-sensitive materials with too high weight average molecular weight y may cause difficulties in chemical reactions of the overcharge-sensitive materials, longer degradation time, and affect response speed.
  • the weight-average molecular weight y of the overcharge sensitive substance may satisfy: 2000 ⁇ y ⁇ 20000, 2000 ⁇ y ⁇ 3000, 3000 ⁇ y ⁇ 4000, 4000 ⁇ y ⁇ 5000, 5000 ⁇ y ⁇ 6000, 6000 ⁇ y ⁇ 8000, 8000 ⁇ y ⁇ 10000, 10000 ⁇ y ⁇ 12000, 12000 ⁇ y ⁇ 14000, 14000 ⁇ y16000, 16000 ⁇ y ⁇ 18000, or 18000 ⁇ y ⁇ 20000.
  • the overcharge-sensitive material may include a monosaccharide structural unit, and may include at least one of a carbonate group and a phosphate group, so that it can be under certain conditions (for example, temperature, Voltage and other conditions), a chemical reaction can take place to degrade substances that produce sugar unit fragments containing carbonate groups and/or phosphate groups.
  • the overcharge sensitive substance may be at least one of sugar carbonate, sugar phosphate, and mixed carbonic acid and phosphoric acid ester of sugar.
  • Sugar carbonates usually refer to esters formed by replacing at least part of the hydroxyl groups in sugar molecules with carbonic acid groups.
  • the molecular structure of sugar carbonates usually includes carbonate groups; sugar phosphates usually refer to sugar molecules.
  • the molecular structure of the sugar phosphate ester usually includes a phosphate group; the carbonic acid and phosphate mixed ester compounds of sugar usually mean that at least part of the hydroxyl groups in the sugar molecule are The ester compound formed by the substitution of carbonic acid group and phosphoric acid group.
  • the molecular structure of the mixed ester of carbonic acid and phosphoric acid of sugar usually includes a carbonate group and a phosphate group.
  • carbonic acid groups and/or phosphate groups can be used as crosslinking groups to connect multiple monosaccharide molecules and/or polysaccharide molecules (for example, they can be linked to multiple hydroxyl groups belonging to different sugar molecules).
  • the reaction generates carbonate groups or phosphate groups) to form part of the bulk phase space structure. It can also expose part of the outer ends of unsubstituted carbonic acid and/or phosphoric acid, and optionally alkyl groups (for example, chain C1-C5 alkyl group) for end-capping, which can better stabilize the conductive network in the security layer during normal use, and produce more obvious structural changes when degradation occurs, and improve the response to overcharge speed.
  • alkyl groups for example, chain C1-C5 alkyl group
  • the degree of crosslinking of the overcharge-sensitive substance is usually based on the ability to normally prepare the overcharge prevention layer, which should be known to those skilled in the art.
  • monosaccharide structural units can also provide sites for the carbonate and phosphate esterification of sugar molecules; carbonate and phosphate groups have a good affinity with common electrolytes, and have great affinity for Li + Good coordination.
  • the small molecular sugar units and carbonate or phosphate fragments produced by the cleavage can be quickly miscible in electrolytes containing a large amount of carbonate solvents, improving the response speed of the anti-overcharge effect.
  • the overcharge sensitive substance may be an esterified product formed by monosaccharides, polysaccharides (including oligosaccharides), or a mixture of monosaccharides and polysaccharides.
  • Monosaccharides usually refer to a type of sugar that cannot be further hydrolyzed.
  • the molecular structure of monosaccharides can usually include 3-6 carbon atoms; polysaccharides usually refer to two or more monosaccharide units (for example, 2-10, 2, 3). 1, 4, 5, 6, 7, 8, 9, 10, or more than 10 monosaccharide units) sugar chains formed by the combination of glycosidic bonds.
  • the polysaccharide can be selected as an oligosaccharide containing 2-10 monosaccharide structural units to ensure that the overcharge sensitive substance has a suitable weight average molecular weight.
  • the overcharge sensitive material may be a carbonate of sugar. Compared with other materials (for example, phosphate), the carbonate has better compatibility with the electrolyte. .
  • the overcharge sensitive substance may be one or a combination of one or more of monosaccharide carbonate, polysaccharide carbonate, monosaccharide and polysaccharide mixture carbonate, and the like.
  • the conductive material in the safety layer can generally ensure that the safety layer has a certain conductive effect, and when the overcharge sensitive material degrades, it can be produced containing carbonate groups and/or phosphate groups.
  • the sugar unit fragments of the cluster are pushed and displaced, resulting in the destruction of the conductive network in the security layer;
  • the conductive material in the security layer may include one or more of metal conductive materials, carbon-based conductive materials, and polymer conductive materials. .
  • the metal material can be selected from aluminum, aluminum alloy, copper, copper alloy, nickel, nickel alloy, and titanium.
  • the carbon-based conductive material may be selected from Ketjen black, mesophase carbon microspheres, activated carbon, graphite, conductive carbon black, acetylene black, carbon fiber, carbon nanotube, One or more combinations of graphene, etc., for example, the polymer conductive material can be selected from polysulfur nitrides, aliphatic conjugated polymers, aromatic ring conjugated polymers, aromatic heterocyclic conjugated polymers A combination of one or more of them.
  • the conductive material may be a carbon-based conductive material. Because of its lower density and higher conductivity, it can be added in a small amount to satisfy the safety layer in the normal use of electrochemical energy storage. When the device is electrically conductive, it is easy to move when the overcharge sensitive material is degraded, destroying the conductive network, and improving the reliability of overcharge prevention.
  • the conductive material is a zero-dimensional carbon-based conductive material to reduce the random bridging effect of the conductive material in response to overcharge prevention.
  • the conductive material may be zero-dimensional conductive carbon black, which has good conductivity and is easy to achieve a small particle size.
  • the overcharge-sensitive substance can undergo a chemical reaction under certain conditions (for example, temperature, voltage, etc.) to degrade to produce sugar unit fragments containing carbonate groups and/or phosphate groups Of the substance.
  • the conditions for degradation of the overcharge-sensitive material usually correspond to the overcharge condition of the positive pole piece or electrochemical energy storage device.
  • the specific The conditions for overcharging can be changed.
  • the degradation conditions of overcharge-sensitive materials have a certain relationship with temperature and overcharge voltage. For example, when the positive pole piece is used at a high temperature, the overcharge-sensitive materials will reach a lower overcharge voltage.
  • Degradation occurs to ensure the safe use of the electrochemical energy storage device; for another example, if the positive pole piece is overcharged when its own use temperature is low, the overcharge-sensitive material can reach a relatively high overcharge voltage, and part of it It begins to degrade after heating up, but the overall temperature of the positive pole piece is much lower than that of the positive pole piece using traditional PTC materials.
  • the specific degradation voltage and temperature of overcharge sensitive substances can be adjusted according to actual needs.
  • the positive pole piece degrades the overcharge-sensitive material under the condition that the charging voltage is ⁇ V and the temperature is ⁇ °C, where 4.2 ⁇ 5.5, 4.2 ⁇ 4.5, 4.5 ⁇ ⁇ 4.8, 4.8 ⁇ 5.2, or 5.2 ⁇ 5.5, 35 ⁇ 80, 35 ⁇ 40, 40 ⁇ 45, 45 ⁇ 50, 50 ⁇ 55, 55 ⁇ 60, 60 ⁇ 65, 65 ⁇ 70, 70 ⁇ 75, or 75 ⁇ 80.
  • the positive pole pieces within the above ⁇ and ⁇ range can not only ensure normal use under normal voltage and temperature, but also ensure the reliability of overcharge safety performance.
  • the binding material in the safety layer is usually used to ensure that the safety layer is tightly connected with the current collector and the positive electrode active material layer.
  • the binding material can generally be various binders suitable for preparing positive electrode plates in the field.
  • the binding material can be selected from polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, polyurethane, polyacrylonitrile, One of polyimide, epoxy resin, silicone resin, ethylene-vinyl acetate copolymer, styrene butadiene rubber, styrene-acrylic rubber, polyacrylic acid, polyacrylic acid-acrylate copolymer and polyethylene-acrylate copolymer, etc.
  • the binding material is selected from one or a combination of polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, and the like.
  • the bonding substance in the security layer usually needs to have a certain proportion to ensure the normal use of the security layer. However, an excessively high proportion of the binding material may hinder the disintegration of the conductive network when the overcharge sensitive material is degraded.
  • the mass of the bonding substance accounts for 30% to 60%, 30% to 35%, 35% to 40%, 40% to 45%, 45% to 50% of the total mass of the safety layer. %, 50% to 55%, or 55% to 60%.
  • the content of the overcharge sensitive substance and the conductive substance in the safety layer usually needs to have a certain matching to ensure the conductivity of the safety layer during normal use and the blocking ability when overcharge occurs. Too little overcharge sensitive material or too large ratio to conductive material may cause its degradation and still cannot effectively promote the disconnection of the conductive network.
  • the positive pole piece provided in the present application when the mass ratio of the overcharge sensitive substance to the conductive substance in the safety layer is not less than 2:1, the positive pole piece can better exert the anti-overcharge effect. When the overcharge-sensitive material that meets this ratio degrades and breaks, it can quickly promote the displacement of the conductive material and destroy the conductive network.
  • the mass ratio of the overcharge sensitive material to the conductive material in the security layer may be ⁇ 2, ⁇ 3, ⁇ 4, or ⁇ 5.
  • the content of overcharge-sensitive substances and conductive substances in the security layer is within a specific range, which can better ensure the conductive effect of the security layer during normal use.
  • the mass of the overcharge sensitive material accounts for 30%-50%, 30%-35%, 35%-40%, 40%-45%, or 45%-50% of the total mass of the safety layer. %.
  • the mass of the conductive material accounts for 6% to 18%, 6% to 8%, 8% to 10%, 10% to 12%, 12% to 14% of the total mass of the safety layer. 14%-16%, or 16%-18%.
  • the positive electrode current collector is coated with a positive electrode active material layer.
  • one surface or both surfaces of the positive electrode current collector may be coated with the positive electrode active material layer.
  • the safety layer is provided between the positive electrode current collector and the positive electrode active material layer, the number of safety layers and the number of positive electrode active material layers are generally the same. That is, if the positive electrode active material layer is coated on one surface of the positive electrode current collector, it has one safety layer; if the positive electrode active material layer is coated on both surfaces of the positive electrode current collector, it has two safety layers.
  • the positive electrode current collector can usually be a layered body.
  • the positive electrode current collector is provided with a positive electrode active material layer on one surface, or can be provided with a positive electrode active material layer on both surfaces, and at least one of the positive electrode active material layer and the positive electrode A safety layer is provided between the current collectors.
  • the positive current collector is usually a structure or part that can collect current.
  • the positive electrode current collector can be various materials in the field that are suitable for use as the positive electrode current collector of the positive pole piece in the electrochemical energy storage device.
  • the positive electrode current collector can include but not limited to metal foil, etc., more specifically, it can include but not Limited to copper foil, aluminum foil, etc.
  • the positive electrode active material can generally be various materials in the field suitable for the positive electrode active material of the positive electrode sheet in the electrochemical energy storage device.
  • the positive electrode active material can include lithium manganese oxide.
  • Compounds such as lithium manganese oxide compounds may include, but are not limited to, one or a combination of lithium manganese oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, and the like.
  • the positive electrode active material can also include various other materials suitable for the positive electrode active material of the positive electrode sheet in the electrochemical energy storage device, for example, it can also include but not limited to lithium cobaltate, lithium iron phosphate, lithium iron phosphate, etc. One or more of them.
  • the positive active material layer may also generally include a binder, a conductive agent, etc.
  • the binder and conductive agent suitable for preparing the positive active material layer of an electrochemical energy storage device should be known to those skilled in the art.
  • the binder in the positive active material layer may be styrene butadiene rubber (SBR), water-based acrylic resin, sodium carboxymethyl cellulose (CMC), polyvinylidene fluoride (PVDF), poly One or more combinations of tetrafluoroethylene (PTFE), ethylene-vinyl acetate copolymer (EVA), polyvinyl alcohol (PVA), and polyvinyl butyral (PVB).
  • SBR styrene butadiene rubber
  • CMC sodium carboxymethyl cellulose
  • PVDF polyvinylidene fluoride
  • PTFE ethylene-vinyl acetate copolymer
  • EVA polyvinyl alcohol
  • PVB polyvinyl butyral
  • the conductive agent in the positive electrode active material can be one or more of graphite, superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. combination.
  • the positive electrode active material layer may generally include a positive electrode active material, a binder, a conductive agent, etc.
  • the preparation method of the positive pole piece may specifically include the following steps: After the conductive material and the overcharge-sensitive material form a slurry, they are coated on the positive electrode current collector to provide a positive electrode current collector with a safety layer; the positive electrode active material, binder, and conductive agent are mixed to form a slurry, and then coated On the security layer.
  • the second aspect of the present application provides an electrochemical energy storage device, including the positive pole piece provided in the first aspect of the present application.
  • the electrochemical energy storage device provided in this application may be a super capacitor, a lithium ion battery, a lithium metal battery, or a sodium ion battery.
  • the electrochemical energy storage device is a lithium ion battery is shown, but the present application is not limited thereto.
  • the electrochemical energy storage device may be a lithium-ion battery.
  • the lithium-ion battery it may include a positive pole piece, a negative pole piece, and a separator between the positive pole piece and the negative pole piece. , Electrolyte.
  • the positive pole piece may be the positive pole piece provided in the first aspect of the present application.
  • the method for preparing lithium ion batteries should be known to those skilled in the art.
  • each of the positive pole piece, the separator and the negative pole piece can be a layered body, which can be cut to a target size and stacked one after another. It can be wound to a target size to form a battery cell, and can be further combined with an electrolyte to form a lithium ion battery.
  • the negative electrode sheet usually includes a negative electrode current collector and a negative electrode active material layer on the surface of the negative electrode current collector, and the negative electrode active material layer usually includes a negative electrode active material.
  • the negative electrode current collector can generally be a layered body.
  • the negative electrode current collector is provided with a negative electrode active material layer on one surface, or can be provided with a negative electrode active material layer on both surfaces.
  • the negative electrode current collector is usually a structure or part that collects current.
  • the negative electrode current collector can be various materials suitable for use as the negative electrode current collector of a lithium ion battery in the field.
  • the negative electrode current collector can include but is not limited to metal foil, etc., more specifically It can include but not limited to copper foil.
  • the negative active material in the negative active material layer can be various materials suitable for the negative active material of lithium ion batteries in the field, for example, it can include but not limited to graphite, soft carbon, hard carbon, carbon fiber , Mesophase carbon microspheres, silicon-based materials, tin-based materials, lithium titanate or other metals that can form alloys with lithium, or a combination of one or more of them.
  • graphite can be selected from one or a combination of artificial graphite, natural graphite and modified graphite
  • silicon-based material can be selected from one of elemental silicon, silicon-oxygen compounds, silicon-carbon composites, and silicon alloys.
  • tin-based materials can be selected from one or more combinations of elemental tin, tin oxide compounds, tin alloys, and the like.
  • the negative active material layer may also generally include a binder, a conductive agent, etc.
  • the binder and conductive agent suitable for preparing the negative active material layer of an electrochemical energy storage device should be known to those skilled in the art.
  • the binder in the negative active material layer may be styrene butadiene rubber (SBR), water-based acrylic resin, sodium carboxymethyl cellulose (CMC), polyvinylidene fluoride (PVDF), poly One or more combinations of tetrafluoroethylene (PTFE), ethylene-vinyl acetate copolymer (EVA), polyvinyl alcohol (PVA), and polyvinyl butyral (PVB).
  • the conductive agent in the negative electrode active material can be one or more of graphite, superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. combination.
  • the separator can be various materials suitable for lithium ion battery separators in the field, for example, it can include but not limited to polyethylene, polypropylene, polyvinylidene fluoride, aramid, and polyterephthalene.
  • polyethylene polypropylene
  • polyvinylidene fluoride polyvinylidene fluoride
  • aramid polyvinylidene fluoride
  • polyterephthalene One or a combination of ethylene glycol formate, polytetrafluoroethylene, polyacrylonitrile, polyimide, polyamide, polyester, and natural fibers.
  • the electrolyte can be various electrolytes suitable for lithium-ion batteries in the art.
  • the electrolyte usually includes an electrolyte and a solvent, and the electrolyte usually includes a lithium salt.
  • the lithium salt can be an inorganic Lithium salt and/or organic lithium salt, etc., specifically including but not limited to, lithium salt may be selected from LiPF 6 , LiBF 4 , LiN(SO 2 F) 2 (abbreviated as LiFSI), LiN(CF 3 SO 2 ) 2 (Abbreviated as LiTFSI), LiClO 4 , LiAsF 6 , LiB(C 2 O 4 ) 2 (abbreviated as LiBOB), LiBF 2 C 2 O 4 (abbreviated as LiDFOB), one or more combinations.
  • the concentration of the electrolyte may be between 0.8 mol/L and 1.5 mol/L.
  • the solvent can be various solvents suitable for the electrolyte of lithium-ion batteries in the art.
  • the solvent of the electrolyte is usually a non-aqueous solvent, which can be an organic solvent. Specifically, it can include but not limited to ethylene carbonate, propylene carbonate, and carbonic acid. One or more combinations of butene ester, pentene carbonate, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, ethyl methyl carbonate, etc. or their halogenated derivatives.
  • the electrochemical energy storage device is a secondary battery.
  • the present application has no particular limitation on the shape of the secondary battery, which may be cylindrical, square or other arbitrary shapes.
  • Fig. 3 shows a secondary battery 5 with a square structure as an example.
  • the secondary battery can be assembled into a battery module, and the number of secondary batteries contained in the battery module can be multiple, and the specific number can be adjusted according to the application and capacity of the battery module.
  • Fig. 4 is a battery module 4 as an example.
  • a plurality of secondary batteries 5 may be arranged in sequence along the length direction of the battery module 4. Of course, it can also be arranged in any other manner. Furthermore, the plurality of secondary batteries 5 can be fixed by fasteners.
  • the battery module 4 may further include a housing having an accommodation space, and a plurality of secondary batteries 5 are accommodated in the accommodation space.
  • the above-mentioned battery modules can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be adjusted according to the application and capacity of the battery pack.
  • FIGS 5 and 6 show the battery pack 1 as an example.
  • the battery pack 1 may include a battery box and a plurality of battery modules 4 disposed in the battery box.
  • the battery box includes an upper box body 2 and a lower box body 3.
  • the upper box body 2 can be covered on the lower box body 3 and forms a closed space for accommodating the battery module 4.
  • Multiple battery modules 4 can be arranged in the battery box in any manner.
  • the device includes the above-mentioned secondary battery.
  • the secondary battery can be used as a power source for the device or as an energy storage unit of the device.
  • the device can be, but is not limited to, mobile devices (such as mobile phones, laptop computers, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf Vehicles, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.
  • the device can select a secondary battery (Cell), a battery module (Module) or a battery pack (pack) according to its usage requirements.
  • Cell secondary battery
  • Mode battery module
  • pack battery pack
  • Figure 7 is a device as an example.
  • the equipment is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle.
  • battery packs or battery modules can be used.
  • the device may be a mobile phone, a tablet computer, a notebook computer, etc.
  • the device is usually thin and light, and can use secondary batteries as a power source.
  • the "sucrose carbonate" of Example 10 has a hydroxyl esterification degree of 0.88;
  • the "carbonic acid and phosphoric acid mixed esterification of sucrose" of Example 12 is firstly carbonated to a weight average molecular weight of 3000-4000, and an esterification degree of 0.6, and then phosphoric acid is esterified to an esterification degree of 0.9;
  • the raw material degraded cellulose has a weight average molecular weight of 1300, is carbonated to a hydroxyl esterification degree of 0.85, and is fully capped with methyl;
  • the "degradable chitosan carbonate" raw material of Example 16 degrades chitosan with a weight average molecular weight of 4000-5000, is carbonated to a hydroxyl esterification degree of 0.85, and is fully capped with methyl;
  • a uniform , Dense security layer in which the thickness of the metal conductive layer aluminum foil is 12 ⁇ m, the thickness of the security layer when coated on one side is 3 ⁇ m, and the thickness of the security layer when coated on both sides is 1.5 ⁇ m.
  • Ethylene carbonate (EC), propylene carbonate (PC) and dimethyl carbonate (DMC) are mixed uniformly in a weight ratio of 1:1:1 to obtain an organic solvent; then lithium salt LiPF 6 is dissolved in the above organic solvent , Mix well to obtain an electrolyte, in which the concentration of LiPF 6 is 1 mol/L.
  • the positive pole piece, the polyethylene porous separation film, and the negative pole piece are laminated in order, and then wound to obtain a battery; the battery is placed in an outer package, electrolyte is injected and packaged to obtain a lithium ion secondary battery.
  • the preparation method of Comparative Example 1 refers to Example 7.
  • Comparative Example 2 refers to Example 1. The difference is that the safety layer is not prepared at all in Comparative Example 2, and the active material layers are directly prepared on the two surfaces of the current collector.
  • the preparation method of Comparative Example 3 refers to Example 1. The difference is that no overcharge sensitive substance is added to the prepared security layer slurry, and the use ratio of the adhesive substance is 90%, and the use ratio of the conductive substance is 10%.
  • Comparative Example 4 refers to Example 28. The difference is that in the prepared safety layer slurry, degraded cellulose with a weight average molecular weight of 10,000 is used instead of the overcharge sensitive substance.
  • FIG. 1 shows a schematic diagram of voltage and temperature changes in the overcharge safety performance test of one of the batteries in Example 13
  • FIG. 2 shows a schematic diagram of voltage and temperature changes in the overcharge safety performance test of one of the batteries in Comparative Example 2.
  • Cycle capacity retention rate (%) discharge capacity at the 100th cycle/discharge capacity at the first cycle ⁇ 100%
  • Example 1 6/6 94.3%
  • Example 2 4/6 94.1%
  • Example 3 6/6 94.2%
  • Example 4 3/6 94.0%
  • Example 5 2/6 94.1%
  • Example 6 4/6 94.0%
  • Example 7 3/6 93.7%
  • Example 8 6/6 94.4%
  • Example 9 4/6 94.2%
  • Example 10 6/6 93.9%
  • Example 11 2/6 93.9%
  • Example 12 4/6 94.1%
  • Example 13 6/6 94.2%
  • Example 14 6/6 94.0%
  • Example 15 6/6 94.1%
  • Example 16 6/6 94.3%
  • Example 17 3/6 94.3%
  • Example 18 6/6 94.1%
  • Example 19 6/6 94.2%
  • Example 20 6/6 94.0%
  • Example 21 6/6 92.6%
  • Example 22 6/6 94.1%
  • Example 23 6/6 94.4%
  • Example 24 2/6 93.9%
  • Example 25 3/6 94.3%
  • Example 26 3/6 94.1%
  • Example 27 5/6 94.0%
  • Example 28 6/6 94.0% Comparative example 1 0/6 93.9% Comparative example 2 0/6 92.9% Comparative example 3 0/6 93.8% Comparative example 4 0/6 93.5%
  • Comparative Example 4 show that the use of polysaccharides without carbonic acid groups or phosphoric acid groups to replace the overcharge-sensitive substances in this application can not achieve the effect of preventing overcharge.
  • this application effectively overcomes various shortcomings in the prior art and has a high industrial value.

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Abstract

涉及电化学领域，特别是涉及一种正极极片及其相关的电化学储能装置和设备。提供一种正极极片，包括正极集流体、位于正极集流体至少一面上的正极活性物质层以及位于正极活性物质层与正极集流体之间的安全层，所述正极活性物质层包括正极活性物质，所述安全层包括粘结物质、导电物质和过充敏感物质；所述过充敏感物质为包括单糖结构单元，且包括碳酸酯基团和磷酸酯基团中的至少一种的聚合物；所述导电物质的平均粒径x和所述过充敏感物质的重均分子量y满足式1。所提供的使用过充敏感物质的安全层具有更好的可靠性，进而可以使电化学储能装置具有更好的安全性。

Description

正极极片及其相关的电化学储能装置和设备
本申请要求于2019年8月8日提交中国专利局、申请号为201910730972.9、申请名称为“一种正极极片及电化学储能装置”的中国专利申请的优先权，其全部内容通过引用结合在本申请中。
技术领域
本申请涉及电化学领域，特别是涉及一种正极极片及其相关的电化学储能装置和设备。
背景技术
锂离子二次电池主要依靠锂离子在正极活性物质和负极活性物质之间的往返迁移来进行充电、放电。锂离子二次电池在使用过程中能够提供稳定的电压和电流，且使用过程绿色环保，从而被广泛地应用于各类用电设备，如手机、平板电脑、笔记本电脑、电动自行车、电动汽车等。
锂离子二次电池造福人类的同时，在充电过程中出现的起火和***等安全问题也时有发生，给人们的生命和财产安全带来很大威胁。
发明内容
鉴于以上所述现有技术的缺点，本申请的目的在于提供一种正极极片及其相关的电化学储能装置和设备，用于解决现有技术中的问题。
为实现上述目的及其他相关目的，本申请一方面提供一种正极极片，包括正极集流体、位于正极集流体至少一面上的正极活性物质层以及位于正极活性物质层与正极集流体之间的安全层，所述正极活性物质层包括正极活性物质，所述安全层包括粘结物质、导电物质和过充敏感物质；
所述过充敏感物质为包括单糖结构单元，且包括碳酸酯基团和磷酸酯基团中的至少一种的聚合物；
所述导电物质的平均粒径x和所述过充敏感物质的重均分子量y满足 式1；
0.001≤x/y≤0.25        式1；
其中，x的单位为nm，y的单位为1。
本申请另一方面提供一种电化学储能装置，包括上述的正极极片。
本申请所提供的正极极片可以用于形成电化学储能装置，在电化学储能装置充电时，如果发生过充滥用，较低的温度下便会导致过充敏感物质发生化学反应而降解，进而引起材料的物理结构发生变化，导致安全层中的导电材料颗粒相分离，破坏安全层中的导电网络，使电化学储能装置的内阻急剧增大，阻断正极集流体与正极活性物质层间的电子导通，及时切断充电电流，有效防止电化学储能装置发生热失控，避免引发起火、***等安全问题，提高电化学储能装置的过充安全性能。
对于依赖结晶度变化引起体积膨胀的PTC材料，其在高温条件下发生物理变化，这种变化受材料涂层制备工艺及电化学储能装置制备工艺的影响较大，比如，材料涂层制备工艺中的温度及涂布速度、电化学储能装置中的电解液等，都会对材料的结晶度产生影响、且影响不可控；此外，PTC材料更依赖于发生短路或者过充时，电池温度剧烈上升到一定程度而导致的电阻变化；对于热失控发生速度很快的电化学储能装置发生过充电，PTC材料很可能未被激发，不能及时切断充电电流，可靠性难以保证,存在安全隐患。与传统PTC材料作为安全层的设计相比，本申请所提供的使用过充敏感物质的安全层具有更好的可靠性，进而可以使电化学储能装置具有更好的安全性。
另一方面，本申请提供一种包含上述电化学储能装置的电池模块。
还要另一方面，本申请提供一种包含上述电池模块的电池包。
还要更进一步的方面，本申请提供一种包含上述电化学储能装置的设备，所述电化学储能装置可以作为所述设备的电源，也可以作为所述设备的能量存储单元。
本申请的电池模块、电池包和设备包括本申请提供的电化学储能装置，因而至少具有与本申请电化学储能装置相同的优势。
附图说明
为了更清楚地说明本申请实施例的技术方案，下面将对本申请实施例中所需要使用的附图作简单地介绍，显而易见地，下面所描述的附图仅仅是本申请的一些实施例，对于本领域普通技术人员来讲，在不付出创造性劳动的前提下，还可以根据附图获得其他的附图。
图1为本申请实施例13其中一个电池的过充安全性能测试的电压和温度变化示意图；
图2为本申请对比例2其中一个电池的过充安全性能测试的电压和温度变化示意图；
图3是二次电池的一实施方式的示意图；
图4是电池模块的一实施方式的示意图；
图5是电池包的一实施方式的示意图；
图6是图5的分解图；
图7是二次电池用作电源的设备的一实施方式的示意图。
其中，附图标记说明如下：
1电池包
2上箱体
3下箱体
4电池模块
5二次电池
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“多种”的含义是两种以上。
本申请的上述发明内容并不意欲描述本申请中的每个公开的实施方式或每种实现方式。如下描述更具体地举例说明示例性实施方式。在整篇申请中的多处，通过一系列实施例提供了指导，这些实施例可以以各种组合形式使用。在各个实例中，列举仅作为代表性组，不应解释为穷举。
正极极片
本申请第一方面提供一种正极极片，包括正极集流体、位于正极集流体至少一面上的正极活性物质层以及位于正极活性物质层与正极集流体之间的安全层；正极活性物质层包括正极活性物质，安全层包括粘结物质、导电物质和过充敏感物质；
过充敏感物质包括单糖结构单元，且包括碳酸酯基团和磷酸酯基团中的至少一种；
导电物质的平均粒径x和过充敏感物质的重均分子量y满足式1；
0.001≤x/y≤0.25         式1；
其中，x的单位为nm，y的单位为1。
本申请所提供的正极极片可以用于形成电化学储能装置，在电化学储能装置发生过充电时，安全层中的过充敏感物质可以在一定条件下(例如，过高的温度、电压等条件)发生化学反应，降解产生的含有碳酸酯基和/或磷酸酯基团的糖单元片段能够迅速混溶于含有大量碳酸酯溶剂的电解液，从难以***的大分子链转变为可***的小分子溶液或溶胶状态，推动安全层中导电物质一起发生位移，破坏安全层中的导电网络，因此过充敏感物质在断裂降解时对导电网络崩解的推动能力，是防过充响应速度等效果的关键。而本申请发明人意外发现，过充敏感物质的分子量与安全层中所使用的导电物质的粒径满足一定匹配关系时，能够很好发挥上述效果。例如，导电物质的平均粒径x和所述过充敏感物质的重均分子量y可以满足x/y≤0.25的关系(x的单位为nm，y的单位为1)。本申请所提供的正 极极片中，导电物质的平均粒径通常指涂覆至安全层中的导电物质，通过电镜观测平均计数统计获得的粒径，对于非球状颗粒，取其长轴径与短轴径的均值为平均粒径。
在本申请一些具体实施例中，导电物质的平均粒径x和过充敏感物质的重均分子量y可以满足0.001≤x/y≤0.25、0.001≤x/y≤0.005、0.005≤x/y≤0.01、0.01≤x/y≤0.05、0.05≤x/y≤0.1、0.1≤x/y≤0.15、0.15≤x/y≤0.2、或0.2≤x/y≤0.25。本申请所提供的正极极片中，平均粒径x越小的导电物质，在过充敏感物质断裂时更则容易发生位移而断开导电网络；所以对于导电物质本身来说，可选具有较小的粒径。本申请一些具体实施例中，导电物质的平均粒径x可以满足：x≤600nm、x≤500nm、x≤400nm、x≤300nm、x≤200nm、或x≤100nm。
本申请所提供的正极极片中，重均分子量y量较大的过充敏感物质，在断裂时能够对导电网络的断开产生更强烈的推动作用；重均分子量y过低的过充敏感物质可能会导致无法在正常使用时稳定导电网络；重均分子量y过高的过充敏感物质则可能会导致过充敏感物质化学反应困难，降解时间较长，影响响应速度。本申请一些具体实施例中，过充敏感物质的重均分子量y可以满足：2000≤y≤20000、2000≤y≤3000、3000≤y≤4000、4000≤y≤5000、5000≤y≤6000、6000≤y≤8000、8000≤y≤10000、10000≤y≤12000、12000≤y≤14000、14000≤y16000、16000≤y≤18000、或18000≤y≤20000。
本申请所提供的正极极片中，过充敏感物质可以包括单糖结构单元，且可以包括碳酸酯基团和磷酸酯基团中的至少一种，从而可以在一定条件下(例如，温度、电压等条件)，能够发生化学反应，降解产生含有碳酸酯基和/或磷酸酯基团的糖单元片段的物质。在本申请一些具体实施例中，过充敏感物质可以为糖的碳酸酯化物、糖的磷酸酯化物、以及糖的碳酸和磷酸混合酯化物中的至少一种。糖的碳酸酯化物通常指糖分子中至少部分的羟基被碳酸基团取代所形成的酯化物，糖的碳酸酯化物的分子结构中通常包括碳酸酯基团；糖的磷酸酯化物通常指糖分子中至少部分的羟基被磷酸基团取代所形成的酯化物，糖的磷酸酯化物的分子结构中通常包括磷酸酯基团；糖的碳酸和磷酸混合酯化物通常指糖分子中至少部分的羟基被碳 酸基团和磷酸基团取代所形成的酯化物，糖的碳酸和磷酸混合酯化物的分子结构中通常包括碳酸酯基团和磷酸酯基团。过充敏感物质的分子结构中，碳酸基团和/或磷酸基团可以作为交联基团连接多个单糖分子和/或多糖分子(例如，可以与多个属于不同糖分子的羟基基团反应生成碳酸酯基团或磷酸酯基团)，以形成部分体相空间结构，也可以暴露部分未取代的碳酸和/或磷酸外端，还可以依情况可以选择烷基基团(例如，链长为C1～C5的烷基基团)进行封端，从而可以在正常使用时更好地稳定安全层中的导电网络，并在发生降解时产生更明显的结构变化，提高抗过充的响应速度。过充敏感物质的交联程度通常以能够正常制备防过充层为准，这对于本领域技术人员来说应该是已知的。过充敏感物质中，单糖结构单元也可以为糖分子的碳酸酯和磷酸酯化提供位点；碳酸酯和磷酸酯基团与常见电解液有很好的亲和作用，对Li +有很好的配位作用，此外，断裂产生的小分子糖单元和碳酸酯或磷酸酯片段，能够迅速混溶于含有大量碳酸酯溶剂的电解液，提高防过充效果的响应速度。
本申请所提供的正极极片中，过充敏感物质可以是由单糖、多糖(包括寡聚糖)、或单糖和多糖混合物所形成的酯化物。单糖通常指无法进一步水解的一类糖，单糖的分子结构中通常可以包括3～6个碳原子；多糖通常指包括两个以上单糖单元(例如，2～10个、2个、3个、4个、5个、6个、7个、8个、9个、10个、或10个以上单糖单元)由糖苷键结合所形成的糖链。作为过充敏感物质来说，多糖可选为含有2～10个单糖结构单元的寡聚糖，以保证过充敏感物质具有合适的重均分子量。
进一步的，本申请所提供的正极极片中，过充敏感物质可以为糖的碳酸酯化物，碳酸酯化物与其他物质(例如，磷酸酯化物)相比，与电解液有更好的兼容性。在本申请一些具体实施例中，过充敏感物质可以为单糖的碳酸酯化物、多糖的碳酸酯化物、单糖与多糖混合物的碳酸酯化物等中的一种或多种的组合。
本申请所提供的正极极片中，安全层中的导电物质通常可以保证安全层具有一定的导电效果，且在过充敏感物质降解时，可以被产生的含有碳酸酯基和/或磷酸酯基团的糖单元片段推动，并发生位移，导致安全层中的导电网络被破坏；安全层中的导电物质可以包括金属导电材料、碳基导电 材料、高分子导电材料等中的一种或多种。本领域技术人员可选用合适的适用于安全层的金属导电材料、碳基导电材料和高分子导电材料，例如，金属材料可以选自铝、铝合金、铜、铜合金、镍、镍合金、钛、银等中的一种或多种的组合，再例如，碳基导电材料可以选自科琴黑、中间相碳微球、活性炭、石墨、导电炭黑、乙炔黑、碳纤维、碳纳米管、石墨烯等中的一种或多种的组合，再例如，高分子导电材料可以选自聚氮化硫类、脂肪族共轭聚合物、芳环共轭聚合物、芳杂环共轭聚合物等中的一种或多种的组合。
在本申请一些可选实施例中，导电物质可以为碳基导电材料，因为其较低的密度和较高的导电性，能够在少量添加的情况下，满足安全层在正常使用电化学储能装置时的导电性，并容易在过充敏感物质发生降解时，随之发生运动，破坏导电网络，提升防过充可靠性。在本申请一些更加可选的实施例中，导电物质为零维碳基导电材料，以减小导电物质在防过充响应时的随机搭桥效应。在本申请一些进一步可选的实施例中，所述导电物质可选为零维导电炭黑，其具有良好的导电性，并容易实现小粒径。
本申请所提供的正极极片中，过充敏感物质在一定条件下(例如，温度、电压等条件)，能够发生化学反应，降解产生含有碳酸酯基和/或磷酸酯基团的糖单元片段的物质。正极极片中，过充敏感物质发生降解的条件通常与正极极片或电化学储能装置的过充条件是相对应的，而对于不同的正极极片或电化学储能装置来说，具体的过充的条件是可以变化的。过充敏感物质发生降解的条件与温度和过充电压均有一定关系，例如，正极极片在自身使用温度较高的情况下，过充敏感物质在达到较低的过充电压时，便会发生降解，以保证电化学储能装置的安全使用；再例如，正极极片在自身使用温度较低的情况下发生过充，过充敏感物质可在达到相对较高的过充电压，发生一部分升温后开始降解，但正极极片的整体温度要比使用传统PTC材料的正极极片低许多。过充敏感物质具体的降解电压与温度，可根据实际需要进行调控。在本申请一些具体实施例中，正极极片在充电电压为αV且温度为β℃的条件下，过充敏感物质发生降解，其中，4.2≤α≤5.5、4.2≤α≤4.5、4.5≤α≤4.8、4.8≤α≤5.2、或5.2≤α≤5.5，35≤β≤80、35≤β≤40、40≤β≤45、45≤β≤50、50≤β≤55、55≤β≤60、60≤β≤65、65≤β≤70、70≤β≤75、或75≤β≤80。 在上述α和β范围内的正极极片，既能保证正常电压和温度下的正常使用，又能保证过充安全性能的可靠性。
本申请所提供的正极极片中，安全层中的粘结物质通常用于保证安全层与集流体和正极活性物质层紧密连接。粘结物质通常可以是本领域各种适用于制备正极极片的粘结剂，例如，粘结物质可以选自聚偏氟乙烯、偏氟乙烯-六氟丙烯共聚物、聚胺酯、聚丙烯腈、聚酰亚胺、环氧树脂、有机硅树脂、乙烯-醋酸乙烯共聚物、丁苯橡胶、苯丙橡胶、聚丙烯酸、聚丙烯酸-丙烯酸酯共聚物及聚乙烯-丙烯酸酯共聚物等中的一种或多种的组合。在本申请一些可选的实施例中，粘结物质选自聚偏氟乙烯、偏氟乙烯-六氟丙烯共聚物等中的一种或多种的组合。安全层中的粘结物质通常需要具有一定的比例，以保证安全层正常使用。但过高的粘结物质的比例可能会在过充敏感物质发生降解时，对导电网络崩解产生阻碍作用。在本申请一些具体实施例中，粘结物质的质量占所述安全层总质量的30％～60％、30％～35％、35％～40％、40％～45％、45％～50％、50％～55％、或55％～60％。
本申请所提供的正极极片中，安全层中过充敏感物质和导电物质的含量通常需要具有一定匹配，以保证安全层在正常使用时的导电性能和在发生过充时的阻断能力。过充敏感物质太少或与导电物质的比例过大，可能会导致其降解以后依然无法有效推动导电网路的断开。本申请所提供的正极极片中，安全层中过充敏感物质与导电物质的质量比不小于2：1时，能更好发挥正极极片的防过充效果。满足该比例的过充敏感物质在降解断裂时，能迅速推动导电物质发生位移，破坏导电网络。在本申请一些具体实施例中，在安全层中过充敏感物质与导电物质的质量比可以≥2、≥3、≥4、或≥5。
此外，安全层中过充敏感物质和导电物质的含量在特定范围内，能够更好的确保安全层正常使用时的导电效果。在本申请一些具体实施例中，过充敏感物质的质量占安全层总质量的30％～50％、30％～35％、35％～40％、40％～45％、或45％～50％。在本申请另一些具体实施例中，导电物质的质量占安全层总质量的6％～18％、6％～8％、8％～10％、10％～12％、12％～14％、14％～16％、或16％～18％。
本申请所提供的正极极片中，正极集流体的至少一个表面上涂布有正 极活性材料层。在本申请一具体实施例中，所述正极集流体的一个表面、或两个表面上可以涂布有所述正极活性材料层。需要说明的是，由于安全层设于所述正极集流体与所述正极活性材料层之间，因此，安全层的数量与正极活性材料层的数量通常来说是一致的。即如果正极集流体的一个表面上涂布有所述正极活性材料层，则具有一个安全层；若正极集流体的两个表面上均涂布有所述正极活性材料层，则具有两个安全层。正极集流体通常可以为层体，正极集流体在其一个表面上设有正极活性物质层，也可以在其两个表面均设有正极活性物质层，且其中至少一个的正极活性物质层与正极集流体之间设有安全层。正极集流体通常是可以汇集电流的结构或零件。正极集流体可以是本领域各种适用于作为电化学储能装置中正极极片的正极集流体的材料，例如，正极集流体可以是包括但不限于金属箔等，更具体可以是包括但不限于铜箔、铝箔等。
本申请所提供的正极极片中，正极活性物质通常可以是本领域各种适用于作为电化学储能装置中正极极片的正极活性物质的材料，例如，正极活性物质可以包括锂锰氧化物类化合物等，锂锰氧化物类化合物可以是包括但不限于锂锰氧化物、锂镍锰氧化物、锂镍钴锰氧化物等中的一种或多种的组合。正极活性物质还可以包括其他各种适用于作为电化学储能装置中正极极片的正极活性物质的材料，例如，还可以是包括但不限于钴酸锂、磷酸亚铁锂、磷酸铁锂等中的一种或多种的组合。正极活性物质层通常还可以包括粘结剂、导电剂等，适用于制备电化学储能装置的正极活性物质层的粘结剂和导电剂对于本领域技术人员来说应该是已知的。例如，正极活性物质层中的粘结剂可以为丁苯橡胶(SBR)、水性丙烯酸树脂(water-based acrylic resin)、羧甲基纤维素钠(CMC)、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)等中的一种或多种的组合。再例如，正极活性物质中的导电剂可以为石墨、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等中的一种或多种的组合。
本领域技术人员可选择合适的方法制备正极极片，正极活性物质层通常可以包括正极活性物质、粘结剂、导电剂等，正极极片的制备方法具体可以包括如下步骤：将粘结物质、导电物质和过充敏感物质形成浆料后， 涂布于正极集流体上，以提供负载有安全层的正极集流体；将正极活性物质、粘结剂、导电剂混合形成浆料后，涂布于安全层上。
电化学储能装置
本申请的第二方面提供一种电化学储能装置，包括本申请第一方面所提供的正极极片。
需要说明的是，本申请所提供的电化学储能装置可以为超级电容器、锂离子电池、锂金属电池或钠离子电池等。在本申请的实施例中，仅示出电化学储能装置为锂离子电池的实施例，但本申请不限于此。
在本申请一具体实施例中，电化学储能装置可以是锂离子电池，在锂离子电池中，可以包括正极极片、负极极片、间隔于正极极片和负极极片之间的隔离膜、电解液。其中，正极极片可以是如本申请第一方面所提供的正极极片。制备锂离子电池的方法对于本领域技术人员来说应该是已知的，例如，正极极片、隔离膜和负极极片各自都可以是层体，从而可以裁剪成目标尺寸后依次叠放，还可以卷绕至目标尺寸，以用于形成电芯，并可以进一步与电解液结合以形成锂离子电池。
在锂离子电池中，负极极片通常包括负极集流体和位于负极集流体表面的负极活性物质层，负极活性物质层通常包括负极活性物质。负极集流体通常可以为层体，负极集流体在其一个表面上设有负极活性物质层，也可以在其两个表面均设有负极活性物质层。负极集流体通常是汇集电流的结构或零件，负极集流体可以是本领域各种适用于作为锂离子电池负极集流体的材料，例如，负极集流体可以是包括但不限于金属箔等，更具体可以是包括但不限于铜箔等。
在锂离子电池中，负极活性物质层中的负极活性物质可以是本领域各种适用于锂离子电池的负极活性物质的材料，例如，可以是包括但不限于石墨、软碳、硬碳、碳纤维、中间相碳微球、硅基材料、锡基材料、钛酸锂或其他能与锂形成合金的金属等中的一种或多种的组合。其中，石墨可选自人造石墨、天然石墨以及改性石墨中的一种或多种的组合；硅基材料可选自单质硅、硅氧化合物、硅碳复合物、硅合金中的一种或多种的组合；锡基材料可选自单质锡、锡氧化合物、锡合金等中的一种或多种的组合。 负极活性物质层通常还可以包括粘结剂、导电剂等，适用于制备电化学储能装置的负极活性物质层的粘结剂和导电剂对于本领域技术人员来说应该是已知的。例如，负极活性物质层中的粘结剂可以为丁苯橡胶(SBR)、水性丙烯酸树脂(water-based acrylic resin)、羧甲基纤维素钠(CMC)、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)等中的一种或多种的组合。再例如，负极活性物质中的导电剂可以为石墨、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等中的一种或多种的组合。
在锂离子电池中，隔离膜可以是本领域各种适用于锂离子电池隔离膜的材料，例如，可以是包括但不限于聚乙烯、聚丙烯、聚偏氟乙烯、芳纶、聚对苯二甲酸乙二醇酯、聚四氟乙烯、聚丙烯腈、聚酰亚胺，聚酰胺、聚酯和天然纤维等中的一种或多种的组合。
在锂离子电池中，电解液可以是本领域各种适用于锂离子电池的电解液，例如，电解液通常包括电解质和溶剂，电解质通常可以包括锂盐等，更具体的，锂盐可以是无机锂盐和/或有机锂盐等，具体可以是包括但不限于，锂盐可选自LiPF 6、LiBF 4、LiN(SO 2F) 2(简写为LiFSI)、LiN(CF 3SO 2) 2(简写为LiTFSI)、LiClO 4、LiAsF 6、LiB(C 2O 4) 2(简写为LiBOB)、LiBF 2C 2O 4(简写为LiDFOB)中的的一种或多种的组合。再例如，电解质的浓度可以为0.8mol/L～1.5mol/L之间。溶剂可以是本领域各种适用于锂离子电池的电解液的溶剂，电解液的溶剂通常为非水溶剂，可选为有机溶剂，具体可以是包括但不限于碳酸乙烯酯、碳酸丙烯酯、碳酸丁烯酯、碳酸戊烯酯、碳酸二甲酯、碳酸二乙酯、碳酸二丙酯、碳酸甲乙酯等或它们的卤代衍生物中的一种或多种的组合。
以下通过特定的具体实例说明本申请的实施方式，本领域技术人员可由本说明书所揭露的内容轻易地了解本申请的其他优点与功效。本申请还可以通过另外不同的具体实施方式加以实施或应用，本说明书中的各项细节也可以基于不同观点与应用，在没有背离本申请的精神下进行各种修饰或改变。
须知，下列实施例中未具体注明的工艺设备或装置均采用本领域内的常规设备或装置。
此外应理解，本申请中提到的一个或多个方法步骤并不排斥在所述组合步骤前后还可以存在其他方法步骤或在这些明确提到的步骤之间还可以***其他方法步骤，除非另有说明；还应理解，本申请中提到的一个或多个设备/装置之间的组合连接关系并不排斥在所述组合设备/装置前后还可以存在其他设备/装置或在这些明确提到的两个设备/装置之间还可以***其他设备/装置，除非另有说明。而且，除非另有说明，各方法步骤的编号仅为鉴别各方法步骤的便利工具，而非为限制各方法步骤的排列次序或限定本申请可实施的范围，其相对关系的改变或调整，在无实质变更技术内容的情况下，当亦视为本申请可实施的范畴。
在本申请的具体实施方式中，所述电化学储能装置为二次电池。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。如图3是作为一个示例的方形结构的二次电池5。
在一些实施例中，二次电池可以组装成电池模块，电池模块所含二次电池的数量可以为多个，具体数量可根据电池模块的应用和容量来调节。
图4是作为一个示例的电池模块4。参照图4，在电池模块4中，多个二次电池5可以是沿电池模块4的长度方向依次排列设置。当然，也可以按照其他任意的方式进行排布。进一步可以通过紧固件将该多个二次电池5进行固定。
可选地，电池模块4还可以包括具有容纳空间的壳体，多个二次电池5容纳于该容纳空间。
在一些实施例中，上述电池模块还可以组装成电池包，电池包所含电池模块的数量可以根据电池包的应用和容量进行调节。
图5和图6是作为一个示例的电池包1。参照图5和图6，在电池包1中可以包括电池箱和设置于电池箱中的多个电池模块4。电池箱包括上箱体2和下箱体3，上箱体2能够盖设于下箱体3，并形成用于容纳电池模块4的封闭空间。多个电池模块4可以按照任意的方式排布于电池箱中。
本申请另一方面提供一种设备，所述设备包括上述的二次电池，所述二次电池可以作为所述设备提供电源，也可以作为所述设备的能量存储单元。所述设备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***等。
所述设备可以根据其使用需求来选择二次电池(Cell)、电池模块(Module)或电池包(pack)。
图7是作为一个示例的设备。该设备为纯电动车、混合动力电动车、或插电式混合动力电动车等。为了满足该设备对二次电池的高功率和高能量密度的需求，可以采用电池包或电池模块。
作为另一个示例的设备可以是手机、平板电脑、笔记本电脑等。该设备通常要求轻薄化，可以采用二次电池作为电源。
实施例1～28
正极极片的制备：
制作安全层浆料：取粘结物质、导电物质、过充敏感物质置于行星式搅拌釜内，再加入上述物料总重量9倍的N-甲基吡咯烷酮(NMP)作为分散溶剂，快速搅拌5小时形成均匀稳定的浆料，所选用的粘结物质、导电物质、过充敏感物的选择和配比详见表1，表1的配比中，各物质的百分比含量均以粘结物质、导电物质、过充敏感物质的总质量进行计算。各实施例中所使用的过充敏感物质参数如下：
实施例1～9的“葡萄糖碳酸酯化物”，羟基的酯化度为0.9；
实施例10的“蔗糖碳酸酯化物”，羟基酯化度为0.88；
实施例11的“蔗糖磷酸酯化物”，酯化度0.92；
实施例12的“蔗糖的碳酸与磷酸混合酯化物”，先经碳酸脂化至重均分子量3000～4000，酯化度0.6，后经磷酸酯化至酯化度0.9；
实施例13、17～28的“葡萄糖与蔗糖混合物的碳酸脂化物”，蔗糖与葡萄糖比例为1:1，羟基的酯化度为0.9；
实施例14的“γ-环糊精碳酸酯化物”，羟基的酯化度为0.9；
实施例15的“降解纤维素碳酸酯化物”，原料降解纤维素重均分子量1300，经碳酸酯化至羟基酯化度0.85，并用甲基充分封端；
实施例16的“降解壳聚糖碳酸酯化物”原料降解壳聚糖重均分子量4000～5000，经碳酸酯化至羟基酯化度0.85，并用甲基充分封端；
将上述均匀稳定的浆料抽真空除气泡，将安全层浆料涂覆于正极集流体的单面或双面(具体为单面或双面涂覆详见表1)，烘干后得到均匀、致密的安全层，其中金属导电层铝箔的厚度为12μm，单面涂覆时的安全层的厚度均为3μm，双面涂覆时的安全层的厚度为1.5μm。
将正极活性物质LiNi 0.8Co 0.1Mn 0.1O 2、导电剂Super-P、粘结剂PVDF按照重量比95:2:3分散于溶剂NMP中，充分搅拌混合均匀得到正极浆料；将正极浆料均匀涂覆于安全层表面，经烘干、冷压后，得到正极极片。
表1
Figure PCTCN2020106471-appb-000001
Figure PCTCN2020106471-appb-000002
Figure PCTCN2020106471-appb-000003
Figure PCTCN2020106471-appb-000004
负极极片的制备：
将负极活性物质人造石墨、导电剂Super-P、粘结剂丁苯橡胶(SBR)及羧甲基纤维素钠(CMC)按照重量比93:3:2:2分散于溶剂去离子水中，搅拌混合均匀后得到负极浆料。之后将负极浆料涂覆在负极集流体铜箔的相对两个表面，经烘干、冷压后，得到负极极片。
电解液的制备：
将碳酸乙烯酯(EC)、碳酸丙烯酯(PC)及碳酸二甲酯(DMC)按照重量比为1:1:1混合均匀，得到有机溶剂；再将锂盐LiPF 6溶解于上述有机溶剂中，混合均匀，得到电解液，其中LiPF 6的浓度为1mol/L。
锂离子二次电池的制备：
将正极极片、聚乙烯多孔隔离膜、负极极片按顺序层叠好，然后卷绕得到电芯；将电芯装入外包装中，注入电解液并封装，得到锂离子二次电池。
对比例1
对比例1的制备方法参照实施例7，区别在于，过充敏感物质的重均分子量为3000，导电物质的平均粒径为1000nm，即对应的导电物质的粒径：过充敏感物质分子量＝0.33。
对比例2
对比例2的制备方法参照实施例1，区别在于，对比例2中完全未制备安全层，直接在集流体的两个表面制备了活性物质层。
对比例3
对比例3的制备方法参照实施例1，区别在于，所制作安全层浆料中，未加入过充敏感物质，而粘结物质的使用比例为90％，导电物质的使用比例为10％。
对比例4
对比例4的制备方法参照实施例28，区别在于，所制作安全层浆料中，以重均分子量同样为10000的降解纤维素替代了过充敏感物质。
测试部分：
(1)锂离子二次电池的过充安全性能测试：
在25±2℃下，将锂离子二次电池以1C倍率恒流充电至4.25V，之后以4.25V恒压充电至电流为0.05C，静置30min，然后用夹具将电池固定好，并放置在过充电安全测试设备上，环境温度控制在25±2℃，静置5min后，以1C倍率对满充状态的电池进行过充电，记录每个电池的实时电压和温度变化，直至电池发生起火或***或充电停止。每个实施例和对比例取6个电池进行测试，电池未发生起火或***则通过测试，否则不通过。各实施例和对比例的过充安全性能测试结果如表2所示。另外，图1所示为实施例13其中一个电池的过充安全性能测试的电压和温度变化示意图，图2所示为对比例2其中一个电池的过充安全性能测试的电压和温度变化示意图。
(2)锂离子二次电池的循环性能测试：
在45±2℃下，将锂离子二次电池以1C恒流充电至4.25V，之后以4.25V恒压充电至电流为0.05C，静置5min，然后以1C恒流放电至2.8V，此为一个充放电循环过程，此次的放电容量为首次循环的放电容量。将锂离子二次电池按照上述方法进行200次循环充放电测试，记录每一次循环的放电容量。
循环容量保持率(％)＝第100次循环的放电容量/首次循环的放电容量×100％
各实施例和对比例的循环性能测试结果如表2所示。
实施例1～28和对比例1～4的测试结果示于下表所示：
表2
  通过率 45℃循环200圈容量保持率
实施例1 6/6 94.3％
实施例2 4/6 94.1％
实施例3 6/6 94.2％
实施例4 3/6 94.0％
实施例5 2/6 94.1％
实施例6 4/6 94.0％
实施例7 3/6 93.7％
实施例8 6/6 94.4％
实施例9 4/6 94.2％
实施例10 6/6 93.9％
实施例11 2/6 93.9％
实施例12 4/6 94.1％
实施例13 6/6 94.2％
实施例14 6/6 94.0％
实施例15 6/6 94.1％
实施例16 6/6 94.3％
实施例17 3/6 94.3％
实施例18 6/6 94.1％
实施例19 6/6 94.2％
实施例20 6/6 94.0％
实施例21 6/6 92.6％
实施例22 6/6 94.1％
实施例23 6/6 94.4％
实施例24 2/6 93.9％
实施例25 3/6 94.3％
实施例26 3/6 94.1％
实施例27 5/6 94.0％
实施例28 6/6 94.0％
对比例1 0/6 93.9％
对比例2 0/6 92.9％
对比例3 0/6 93.8％
对比例4 0/6 93.5％
从实施例1～28的测试结果可知，使用本申请所述的正极极片的二次电池，具有很好的过充安全测试通过率，并具有良好的45℃循环200圈容量保持率，另外，由图1可知，正极极片在发生过充时，温度会逐渐升高，在到达一定温度后安全层中的过充敏感物质会发生降解，造成导电网络发生断裂破坏，使电化学储能装置的内阻急剧增大，从而及时切断充电电流；
对比例1的测试结果对比表明，x/y过大，过充安全测试无法通过；
对比例2的测试结果对比表明，使用常规正极极片的二次电池，过充安全测试无法通过且45℃循环200圈容量保持率较低，另外，如图2所示，电池在过充后温度会逐渐升高，并在1200秒左右发生起火；
对比例3的测试结果表明，使用PVDF代替本申请中的过充敏感物质，二次电池不能通过过充安全测试；
对比例4的测试结果表明，使用不具备碳酸基或磷酸基团的多糖代替本申请中的过充敏感物质，也无法获得防过充的效果。
综上所述，本申请有效克服了现有技术中的种种缺点而具高度产业利用价值。
根据上述说明书的揭示和教导，本领域技术人员还可以对上述实施方式进行变更和修改。因此，本申请并不局限于上面揭示和描述的具体实施方式，对本申请的一些修改和变更也应当落入本申请的权利要求的保护范围内。此外，尽管本说明书中使用了一些特定的术语，但这些术语只是为了方便说明，并不对本申请构成任何限制。

Claims (19)

  1. 一种正极极片，包括正极集流体、位于正极集流体至少一面上的正极活性物质层以及位于正极活性物质层与正极集流体之间的安全层，所述正极活性物质层包括正极活性物质，所述安全层包括粘结物质、导电物质和过充敏感物质；
    所述过充敏感物质为包括单糖结构单元，且包括碳酸酯基团和磷酸酯基团中的至少一种的聚合物；
    所述导电物质的平均粒径x和所述过充敏感物质的重均分子量y满足式1；
    0.001≤x/y≤0.25  式1；
    其中，x的单位为nm，y的单位为1。
  2. 如权利要求1所述的正极极片，其中，所述导电物质的平均粒径x≤600nm。
  3. 如权利要求1或2所述的正极极片，其中，所述过充敏感物质的重均分子量2000≤y≤20000。
  4. 如权利要求1-3任一项所述的正极极片，其中，所述过充敏感物质选自糖的碳酸酯化物、糖的磷酸酯化物、以及糖的碳酸和磷酸混合酯化物中的一种或多种的组合。
  5. 如权利要求1-4任一项所述的正极极片，其中，所述过充敏感物质选自单糖的碳酸酯化物、多糖的碳酸酯化物、以及单糖与多糖混合物的碳酸酯化物中的一种或多种的组合。
  6. 如权利要求1-5任一项所述的正极极片，其中，所述导电物质选自金属导电材料、碳基导电材料、高分子导电材料中的一种或多种的组合。
  7. 如权利要求1-6任一项所述的正极极片，其中，所述金属导电材料选自铝、铝合金、铜、铜合金、镍、镍合金、钛、银中的一种或多种的组合，所述碳基导电材料选自科琴黑、中间相碳微球、活性炭、石墨、导电炭黑、乙炔黑、碳纤维、碳纳米管、石墨烯中的一种或多种的组合，所述高分子导电材料选自聚氮化硫类、脂肪族共轭聚合物、芳环共轭聚合物、芳杂环共轭聚合物中的一种或多种的组合。
  8. 如权利要求1-7任一项所述的正极极片，其中，所述导电物质为零维导电颗粒。
  9. 如权利要求1-8任一项所述的正极极片，其中，所述导电物质为零维碳基导电材料颗粒。
  10. 如权利要求1-9任一项所述的正极极片，其中，所述导电物质为零维导电炭黑。
  11. 如权利要求1-10任一项所述的正极极片，其中，所述正极极片在充电电压为αV且温度为β℃的条件下，所述过充敏感物质发生降解，其中4.2≤α≤5.5，35≤β≤80。
  12. 如权利要求1-11任一项所述的正极极片，其中，所述粘结物质选自聚偏氟乙烯、偏氟乙烯-六氟丙烯共聚物、聚胺酯、聚丙烯腈、聚酰亚胺、环氧树脂、有机硅树脂、乙烯-醋酸乙烯共聚物、丁苯橡胶、苯丙橡胶、聚 丙烯酸、聚丙烯酸-丙烯酸酯共聚物及聚乙烯-丙烯酸酯共聚物中的一种或多种的组合。
  13. 如权利要求1-12任一项所述的正极极片，其中，所述粘结物质选自聚偏氟乙烯、偏氟乙烯-六氟丙烯共聚物中的一种或多种的组合。
  14. 如权利要求1-13任一项所述的正极极片，其中，所述粘结物质的质量占所述安全层总质量的30％～60％。
  15. 如权利要求1-14任一项所述的正极极片，其中，所述安全层中，所述过充敏感物质与所述导电物质的质量比不小于2：1；
    和/或，所述过充敏感物质的质量占所述安全层总质量的30％～50％；
    和/或，所述导电物质的质量占所述安全层总质量的6％～18％。
  16. 一种电化学储能装置，包括权利要求1-15任一权利要求所述的正极极片。
  17. 一种电池模块，其中，包括根据权利要求16所述的电化学储能装置。
  18. 一种电池包，其中，包括根据权利要求17所述的电池模块。
  19. 一种设备，其中，包括根据权利要求16所述的电化学储能装置，其中，所述设备选自电动车辆、电动船舶、电动工具、电子设备及储能***中的一种或多种。
PCT/CN2020/106471 2019-08-08 2020-07-31 正极极片及其相关的电化学储能装置和设备 WO2021023135A1 (zh)

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