WO2022104698A1 - 一种改善电极组件安全性的极片及包含其的电化学装置、电子装置 - Google Patents

一种改善电极组件安全性的极片及包含其的电化学装置、电子装置 Download PDF

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WO2022104698A1
WO2022104698A1 PCT/CN2020/130421 CN2020130421W WO2022104698A1 WO 2022104698 A1 WO2022104698 A1 WO 2022104698A1 CN 2020130421 W CN2020130421 W CN 2020130421W WO 2022104698 A1 WO2022104698 A1 WO 2022104698A1
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Prior art keywords
positive electrode
coating
current collector
electrode current
insulating material
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PCT/CN2020/130421
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English (en)
French (fr)
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韩冬冬
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宁德新能源科技有限公司
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Priority to CN202080068060.0A priority Critical patent/CN114503300B/zh
Priority to EP20961989.9A priority patent/EP4250388A1/en
Priority to PCT/CN2020/130421 priority patent/WO2022104698A1/zh
Publication of WO2022104698A1 publication Critical patent/WO2022104698A1/zh
Priority to US18/320,486 priority patent/US20230343962A1/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
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—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
    • H01M4/04—Processes of manufacture in general
    • H01M4/0402—Methods of deposition of the material
    • H01M4/0404—Methods of deposition of the material by coating on electrode collectors
    • 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
    • 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
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2220/00—Batteries for particular applications
    • H01M2220/30—Batteries in portable systems, e.g. mobile phone, laptop
    • 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 energy storage, and in particular, to a pole piece for improving the safety of an electrode assembly, an electrochemical device and an electronic device including the same, especially a lithium ion battery.
  • lithium-ion batteries With the development of technology and the increase in demand for mobile devices, the demand for electrochemical devices (eg, lithium-ion batteries) has increased significantly. At the same time, lithium-ion batteries with high safety are one of the research directions.
  • the electrochemical device In actual use, the electrochemical device will be hit by a foreign object, and in extreme cases, it will be pierced by a sharp object.
  • the electrochemical device When the electrochemical device is pierced, on the one hand, if the piercing object is a metal body, the The piercing part of the fluid is connected to another electrode through the metal body; on the other hand, the piercing part of the current collector usually produces burrs, which deform and extend downward with the piercing object, so that the positive and negative electrodes are pierced through the diaphragm.
  • the above two conditions may lead to the occurrence of a short circuit, which will generate a lot of heat and cause the lithium-ion battery to catch fire or even explode, which seriously threatens the safety of consumers.
  • the embodiments of the present application solve at least one problem in the related art to at least some extent by providing a pole piece for improving the safety of an electrode assembly and an electrochemical device including the same.
  • the present application provides a positive electrode, the positive electrode includes a positive electrode current collector, a positive electrode active material layer and a coating layer, wherein the positive electrode active material layer and the coating layer are arranged on the surface of the positive electrode current collector, and the coating layer
  • the bonding force with the positive electrode current collector is greater than or equal to 5 N/m.
  • the present application provides an electrochemical device comprising the positive electrode in the above embodiment.
  • the positive electrode of the present application can effectively improve the safety performance of its electrode assembly by providing a coating and designing the coating and the positive electrode current collector, and improving the adhesion of the coating to the positive electrode current collector.
  • the coating with high adhesive force can improve the structural stability of the electrode assembly and reduce the occurrence rate of short-circuit between the electrode pieces, thereby improving the electrochemical device. safety performance.
  • the present application provides an electronic device including the above electrochemical device.
  • FIG. 1 is a schematic structural diagram of a positive electrode according to some embodiments of the present application.
  • FIG. 2 is a schematic structural diagram of a positive electrode according to some embodiments of the present application.
  • FIG. 3 is a schematic cross-sectional structural diagram of a positive electrode according to some embodiments of the present application.
  • FIG. 4 is a schematic top-view structural diagram of a positive electrode according to some embodiments of the present application.
  • FIG. 5 is a schematic top-view structural diagram of a positive electrode according to some embodiments of the present application.
  • FIG. 6 is a schematic top-view structural diagram of a positive electrode according to some embodiments of the present application.
  • a list of items joined by the terms "at least one of,” “at least one of,” “at least one of,” or other similar terms may mean the listed items any combination of .
  • the phrase “at least one of A and B” means A only; B only; or A and B.
  • the phrase "at least one of A, B, and C” means A only; or B only; C only; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B, and C.
  • Item A may contain a single element or multiple elements.
  • Item B may contain a single element or multiple elements.
  • Item C may contain a single element or multiple elements.
  • Electrodes (positive or negative electrodes) of electrochemical devices are typically prepared by mixing an active material, a conductive agent, a thickener, a binder, and a solvent, and then coating the mixed slurry on the current collector to form an active material layer.
  • the electrochemical device is pierced, on the one hand, if the pierced object is a metal body, the pierced part of the current collector is connected to another electrode through the metal body; on the other hand, the pierced part of the current collector usually The burr is generated, and the piercing object deforms and extends downward, so as to pierce the separator to directly connect the positive and negative electrodes, resulting in the occurrence of a short circuit.
  • the electrochemical device avoids the contact between the current collector and the metal puncture object, and the current collector burr and another electrode during the process of being punctured or impacted by foreign objects, thereby improving the electrochemical device. safety.
  • the positive electrode of the present application is realized by coating the surface of the current collector with a coating with high cohesive force. As a control method of the cohesive force, the type of binder, the binder and the insulation can be adjusted in the coating slurry. The composition ratio of the material is controlled.
  • the present application provides a positive electrode, which includes the coating layer and a positive electrode active material layer as described below.
  • the positive electrode 10 includes a positive electrode current collector 101 and a positive electrode active material layer 102 and a coating layer 103 provided on the surface of the positive electrode current collector 101 , wherein the positive electrode active material layer 102 is provided on the surface of the positive electrode current collector.
  • the first part 1011 of the coating is provided on the second part 1012 on the surface of the positive current collector.
  • the second portion 1012 on the surface of the positive current collector is different from the first portion 1011 .
  • the second portion is a partial region of the uncoated positive electrode active material layer, which includes, but is not limited to, a side portion of the positive electrode current collector, an end portion of the positive electrode current collector, and a portion of the positive electrode active material layer. Apply intermittently or on the tabs.
  • the positive electrode active material layer and the coating layer may be disposed on the surface of the positive electrode current collector on one side or both sides.
  • FIGS. 1 and 2 are only exemplary examples for illustrating the arrangement relationship between the coating layer and the positive electrode active material layer. As shown in FIG. 3, in some embodiments, there can be a separation distance between the coating and the positive electrode active material layer. In some embodiments, the separation distance between the coating and the positive active material layer is less than or equal to 3 mm.
  • the coating is provided at the end portion of the positive electrode current collector in the lengthwise direction.
  • the width of the coating along the length of the positive current collector is less than or equal to 200 mm. In some embodiments, the width of the coating along the length of the positive current collector is about 150 mm. It should be understood that although the coating of FIG. 4 is only provided on a single end portion of the positive electrode current collector, it is merely an exemplary example for illustrating the coating placement relationship. In some embodiments, the coating may be provided on a single end portion or both end portions of the positive current collector. In some embodiments, the surface of the positive electrode current collector opposite the coating is at least partially provided with a positive electrode active material layer.
  • the coating layer is disposed on the side portion of the positive electrode current collector in the width direction.
  • the width of the coating in the width direction of the positive current collector is less than or equal to 5 mm. In some embodiments, the width of the coating in the width direction of the positive current collector is about 2 mm. In some embodiments, the positive electrode can be provided with a coating along the edge in the width direction of the positive electrode current collector.
  • the coating layer is provided at the coating interval of the positive electrode active material layer along the length direction of the positive electrode current collector.
  • the coating width is less than or equal to 10 mm.
  • the coating has a coating width of about 5 mm.
  • the coating layer is disposed on at least one of the end of the positive electrode current collector in the length direction, the edge of the positive electrode current collector in the width direction, and the interval of the positive electrode active material layer along the length direction of the positive electrode current collector.
  • the positive electrode includes a positive electrode tab, and a coating exists on the surface of the positive electrode tab.
  • the coating is provided on the surface of the positive electrode current collector in all regions of the surface of the positive electrode current collector that are not coated with the positive electrode active material layer. It should be understood that the coating arrangement positions shown in FIGS. 3 to 5 are intended to provide illustrative exemplary embodiments, and those skilled in the art may adjust or combine the various embodiments according to actual needs without departing from the spirit of the present application. Coating set position, not limited by it.
  • the adhesion of the coating to the positive electrode current collector is at least greater than or equal to 5 N/m.
  • the coated positive electrode can effectively improve the protection of the coating to the positive electrode current collector by limiting the adhesion of the coating to the positive electrode current collector, thereby reducing the short circuit phenomenon that may occur when punctured or impacted by external force.
  • the adhesion of the coating to the cathode current collector is greater than or equal to 10 N/m. In other embodiments, the adhesion of the coating to the positive electrode current collector is greater than or equal to 30 N/m.
  • the coating includes a binder.
  • the binder is a colloidal polymer.
  • the binder includes polyvinylidene fluoride PVDF, polytetrafluoroethylene PTFE, sodium carboxymethyl cellulose CMC, styrene butadiene rubber SBR, nitrile rubber, polyurethane, fluorine rubber, polyvinyl alcohol At least one of PVA and sodium polyacrylate.
  • the molecular weight of the binder is greater than or equal to 10 kDa. In other embodiments, the molecular weight of the binder is greater than or equal to 100 kDa.
  • the coating further includes an insulating material.
  • the insulating material can be solid powder, flake or bulk material.
  • the mass percentage of the binder is 2% to 100% based on the weight of the coating.
  • the coating consists of a binder and an insulating material.
  • the insulating material includes at least one of an inorganic insulating material or an organic insulating material.
  • the inorganic insulating material includes an inorganic insulating material containing at least one element of Ba, Ca, Al, Si, Ti, Mg, Fe, and B.
  • the inorganic insulating material includes BaSO 4 , CaSiO 3 , CaSiO 4 , ⁇ -AlOOH, Al 2 O 3 , TiO 2 , SiO 2 , SiC, SiN, MgO, Fe 2 O 3 , BN at least one.
  • the organic insulating material includes at least one of a homopolymer or a copolymer of the following components: ethylene, vinyl chloride, propylene, styrene, butadiene, vinylidene fluoride, tetrafluoroethylene, and Hexafluoropropylene.
  • the molecular weight of the organic insulating material is greater than or equal to 50 kDa.
  • the average particle size T of the insulating material is 0.1 ⁇ m to 20 ⁇ m. In some embodiments, the average particle size T of the insulating material is 0.5 ⁇ m to 5 ⁇ m.
  • the term "average particle size” is the average value of the particle size R of the sample particles.
  • the method for measuring the average particle size of the insulating material particles of the present application is as follows: first, a cross-section is prepared along the direction perpendicular to the positive electrode current collector, and a scanning electron microscope (hereinafter referred to as "SEM") is used to take a SEM image of the cross-section . Then, using image analysis software, randomly select 10 insulating material particles from the SEM image of the cross-section of the coating, and calculate the respective cross-sectional areas of the insulating material particles in the SEM image, and obtain the respective Particle size R (diameter):
  • R 2 ⁇ (S/ ⁇ ) 1/2 ; wherein, S is the area of the insulating material particle;
  • the particle diameter R of the insulating material particles was calculated on 30 SEM images, and the particle diameter R of the 300 obtained insulating material particles was arithmetically averaged to obtain the average particle diameter T of the insulating material particles.
  • the thickness of the coating is greater than or equal to 0.5 ⁇ m.
  • the relationship of the coating to its insulating material satisfies the following conditions:
  • h is the thickness of the coating
  • T is the average particle size of the insulating material.
  • the insulating materials and binders in the coating that meet the above conditions can be further dispersed well and uniformly, so that the coating can evenly cover the surface of the positive electrode current collector, and at the same time, it can also improve the overall coverage of the coating on the surface of the positive electrode current collector.
  • the adhesive force can effectively improve the protection of the coating area.
  • the positive electrode active material layer contains a positive electrode active material.
  • the positive electrode active material layer may be one or more layers, and each layer of the multilayered positive electrode active material may contain the same or different positive electrode active materials.
  • the positive active material is any material that can reversibly intercalate and deintercalate metal ions such as lithium ions.
  • the discharge capacity of the positive active material is less than the rechargeable capacity of the negative active material to prevent unintentional precipitation of lithium metal on the negative electrode during charging.
  • the type of the positive electrode active material is not particularly limited as long as it can electrochemically occlude and release metal ions (eg, lithium ions).
  • the positive active material is a material containing lithium and at least one transition metal.
  • the positive electrode active material may include, but are not limited to, lithium transition metal composite oxides and lithium-containing transition metal phosphate compounds.
  • the transition metal in the lithium transition metal composite oxide includes V, Ti, Cr, Mn, Fe, Co, Ni, Cu, and the like.
  • the lithium transition metal composite oxides include lithium cobalt composite oxides such as LiCoO 2 ; lithium nickel composite oxides such as LiNiO 2 ; lithium manganese composite oxides such as LiMnO 2 , LiMn 2 O 4 , and Li 2 MnO 4 ; LiNi 1/3 Mn 1/3 Co 1/3 O 2 , LiNi 0.5 Mn 0.3 Co 0.2 O 2 and other lithium-nickel-manganese-cobalt composite oxides, in which a part of the transition metal atoms serving as the host of these lithium transition metal composite oxides are Substituted by other elements such as Na, K, B, F, Al, Ti, V, Cr, Mn, Fe, Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, Si, Nb, Mo, Sn, W, etc.
  • lithium transition metal composite oxide may include, but are not limited to, LiNi 0.5 Mn 0.5 O 2 , LiNi 0.85 Co 0.10 Al 0.05 O 2 , LiNi 0.33 Co 0.33 Mn 0.33 O 2 , LiNi 0.45 Co 0.10 Al 0.45 O 2 , LiMn 1.8 Al 0.2 O 4 and LiMn 1.5 Ni 0.5 O 4 and so on.
  • combinations of lithium transition metal composite oxides include, but are not limited to, combinations of LiCoO 2 and LiMn 2 O 4 , wherein a portion of Mn in LiMn 2 O 4 may be replaced by transition metals (eg, LiNi 0.33 Co 0.33 Mn 0.33 O 2 ), a part of Co in LiCoO 2 can be replaced by transition metals.
  • the transition metal in the lithium-containing transition metal phosphate compound includes V, Ti, Cr, Mn, Fe, Co, Ni, Cu, and the like.
  • the lithium-containing transition metal phosphate compounds include LiFePO 4 , Li 3 Fe 2 (PO 4 ) 3 , LiFeP 2 O 7 and other iron phosphates, and LiCoPO 4 and other cobalt phosphates, wherein as these lithium transition metal phosphate compounds A part of the transition metal atoms of the host is replaced by Al, Ti, V, Cr, Mn, Fe, Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, Nb, Si and other elements.
  • a powdered material of lithium transition metal oxide Li a M b O 2 is used, wherein 0.9 ⁇ a ⁇ 1.1, 0.9 ⁇ b ⁇ 1.1, and M is primarily a transition metal selected from Mn, Co, and Ni , where the composition M varies with particle size.
  • A is selected from at least one of the elements Al, Mg, Ti, Cr, and A' At least one selected from elements F, Cl, S, Zr, Ba, Y, Ca, B, Be, Sn, Sb, Na, and Zn.
  • powders with a composition that is related to size ie one component with large particles (eg distributed centered at ⁇ 20 ⁇ m); the component is capable of rapid bulk diffusion.
  • Another component has small particles (eg distributed around 5 ⁇ m) and its composition ensures safety.
  • an electrode active material that combines high cycle stability and high safety with high volumetric energy density and high gravimetric energy density is provided.
  • the positive active material has a broad particle size distribution, defined as a particle size ratio of large particles to small particles greater than 3, and Dv90/Dv10 > 3, where Dv90 represents a volume-based particle size distribution ranging from small particle size From the side up, the particle size reaches 90% of the cumulative volume.
  • Dv10 represents a particle size that reaches 10% of the cumulative volume from the small particle size side in the particle size distribution based on volume.
  • the particle size distribution of the powder can be determined by suitable methods known in the art. Suitable methods are eg laser diffraction or sieving by using sets of sieves with different mesh numbers.
  • the individual particles are substantially lithium transition metal oxides, and the individual particles have Co, whose content in the transition metal increases continuously with particle size.
  • the individual particles also contain Mn in the transition metal, and the Mn content decreases continuously with particle size.
  • the large particles have large particles close to the composition of LiCoO2 to achieve high Li diffusion constants, and thus to achieve adequate rate performance.
  • Large particles occupy only a small fraction of the total surface area of the positive electrode. Therefore, the heat released by the reaction with the electrolyte at the surface or at the outer part is limited; as a result, there are fewer large particles leading to poor safety.
  • Small particles have compositions containing less Co for increased safety. The lower lithium diffusion constant is acceptable in small particles without significant loss of rate performance due to the short length of the solid-state diffusion paths.
  • the preferred composition of the small particles contains smaller amounts of Co and larger amounts of stabilizing elements, such as Mn.
  • the slower Li bulk diffusion is acceptable, but the stability of the surface is high.
  • the preferred composition of large particles contains a larger amount of Co and a smaller amount of Mn, due to the need for rapid lithium diffusion, while a slightly lower surface stability is acceptable.
  • preferably at least 80 w% of the M is cobalt or nickel in the interior of a single particle composed of LixMO2 .
  • the inner portion of the particle has a composition close to LiCoO2.
  • the outer part is lithium manganese nickel cobalt oxide.
  • the preparation of a powdered electrode active material having a composition and size-dependent composition can be achieved by the following methods: depositing at least one transition metal-containing precipitate on seed particles, the seed particles having a transition metal composition different from that of the precipitate; adding controlled and performing at least one thermal treatment wherein substantially all of the particles obtained contain a seed-derived inner core that is completely covered by a precipitate-derived layer.
  • the type of the positive electrode current collector is not particularly limited and may be any suitable material in the art.
  • the positive electrode current collector is an aluminum foil.
  • the elongation of the cathode current collector ranges x: 1.5% to 3.5%.
  • the strength range of the positive current collector is p: 100Mpa to 300Mpa.
  • the thickness range H of the positive electrode current collector is 5 ⁇ m to 20 ⁇ m.
  • the relationship between the coating and the positive electrode current collector satisfies the following conditions:
  • h is the thickness of the coating
  • x is the elongation of the positive electrode current collector
  • p is the strength of the positive electrode current collector
  • H is the thickness of the positive electrode current collector
  • k 100MPa.
  • the coatings of the embodiments of the present application can further prevent the metal spikes formed by the deformation of the positive electrode current collector when it is punctured by defining the relationship between the thickness of the coating and the elongation, strength and thickness of the positive electrode current collector, thereby reducing the Short-circuiting of positive current collectors to other adjacent current collectors.
  • the surface roughness of the positive electrode current collector ranges from 0.01 ⁇ m to 5 ⁇ m. In the positive electrode of the embodiments of the present application, by limiting the surface roughness of the positive electrode current collector, the structural stability of the coating and the positive electrode active material layer disposed on the surface of the positive electrode current collector can be further improved, as well as the electrical performance of the positive electrode.
  • the electrolytic solution used in the electrochemical device of the present application includes an electrolyte and a solvent that dissolves the electrolyte.
  • the electrolyte used in the electrochemical devices of the present application further includes additives.
  • the electrolyte further comprises any non-aqueous solvent known in the art as a solvent for the electrolyte.
  • the non-aqueous solvent includes, but is not limited to, one or more of the following: cyclic carbonate, chain carbonate, cyclic carboxylate, chain carboxylate, cyclic ether, Chain ethers, phosphorus-containing organic solvents, sulfur-containing organic solvents and aromatic fluorine-containing solvents.
  • examples of cyclic carbonates may include, but are not limited to, one or more of the following: ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate.
  • the cyclic carbonate has 3-6 carbon atoms.
  • examples of chain carbonates may include, but are not limited to, one or more of the following: dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate (DEC), methyl n-carbonate Chain carbonates such as propyl ester, ethyl-n-propyl carbonate, di-n-propyl carbonate, etc.
  • fluorine-substituted chain carbonates may include, but are not limited to, one or more of the following: bis(fluoromethyl)carbonate, bis(difluoromethyl)carbonate, bis(trifluoromethyl)carbonate base) carbonate, bis(2-fluoroethyl)carbonate, bis(2,2-difluoroethyl)carbonate, bis(2,2,2-trifluoroethyl)carbonate, 2-fluoroethyl methyl carbonate, 2,2-difluoroethyl methyl carbonate and 2,2,2-trifluoroethyl methyl carbonate, etc.
  • examples of cyclic carboxylic acid esters may include, but are not limited to, one or more of the following: one or more of gamma-butyrolactone and gamma-valerolactone.
  • some of the hydrogen atoms of the cyclic carboxylate may be replaced by fluorine.
  • examples of chain carboxylates may include, but are not limited to, one or more of the following: methyl acetate, ethyl acetate, propyl acetate, isopropyl acetate, butyl acetate, sec-butyl acetate, isobutyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, isopropyl propionate, methyl butyrate, ethyl butyrate, propyl butyrate , methyl isobutyrate, ethyl isobutyrate, methyl valerate, ethyl valerate, methyl pivalate and ethyl pivalate, etc.
  • some of the hydrogen atoms of the chain carboxylate may be replaced by fluorine.
  • examples of fluorine-substituted chain carboxylates may include, but are not limited to, methyl trifluoroacetate, ethyl trifluoroacetate, propyl trifluoroacetate, butyl trifluoroacetate, and trifluoroacetic acid 2,2,2-trifluoroethyl ester, etc.
  • examples of cyclic ethers may include, but are not limited to, one or more of the following: tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, 2-methyl 1 , 3-dioxolane, 4-methyl 1,3-dioxolane, 1,3-dioxane, 1,4-dioxane and dimethoxypropane.
  • examples of chain ethers may include, but are not limited to, one or more of the following: dimethoxymethane, 1,1-dimethoxyethane, 1,2-dimethyl Oxyethane, diethoxymethane, 1,1-diethoxyethane, 1,2-diethoxyethane, ethoxymethoxymethane, 1,1-ethoxymethoxy Ethoxyethane and 1,2-ethoxymethoxyethane, etc.
  • examples of phosphorus-containing organic solvents may include, but are not limited to, one or more of the following: trimethyl phosphate, triethyl phosphate, dimethyl ethyl phosphate, methyl diethyl phosphate Ester, Ethylene Methyl Phosphate, Ethylene Ethyl Phosphate, Triphenyl Phosphate, Trimethyl Phosphite, Triethyl Phosphite, Triphenyl Phosphite, Tris(2,2,2-trifluorophosphate) ethyl) ester and tris(2,2,3,3,3-pentafluoropropyl) phosphate, etc.
  • examples of sulfur-containing organic solvents may include, but are not limited to, one or more of the following: sulfolane, 2-methyl sulfolane, 3-methyl sulfolane, dimethyl sulfone, diethyl sulfolane Sulfone, ethyl methyl sulfone, methyl propyl sulfone, dimethyl sulfoxide, methyl methanesulfonate, ethyl methanesulfonate, methyl ethanesulfonate, ethyl ethanesulfonate, dimethyl sulfate, sulfuric acid Diethyl ester and dibutyl sulfate.
  • some of the hydrogen atoms of the sulfur-containing organic solvent may be replaced by fluorine.
  • aromatic fluorinated solvents include, but are not limited to, one or more of the following: fluorobenzene, difluorobenzene, trifluorobenzene, tetrafluorobenzene, pentafluorobenzene, hexafluorobenzene, and trifluorobenzene Fluoromethylbenzene.
  • the solvent used in the electrolyte of the present application includes cyclic carbonate, chain carbonate, cyclic carboxylate, chain carboxylate, and combinations thereof.
  • the solvent used in the electrolyte of the present application includes ethylene carbonate, propylene carbonate, diethyl carbonate, ethyl propionate, propyl propionate, n-propyl acetate, or ethyl acetate at least one of them.
  • the solvent used in the electrolyte of the present application comprises: ethylene carbonate, propylene carbonate, diethyl carbonate, ethyl propionate, propyl propionate, ⁇ -butyrolactone and combinations thereof .
  • the chain carboxylate and/or cyclic carboxylate can form a passivation film on the surface of the electrode, thereby improving the intermittent charging of the electrochemical device Capacity retention after cycling.
  • the electrolyte contains 1% to 60% of chain carboxylates, cyclic carboxylates, and combinations thereof.
  • the electrolyte contains ethyl propionate, propyl propionate, ⁇ -butyrolactone and combinations thereof, and the content of the combination is 1% to 60%, 10% to 10%, based on the total weight of the electrolyte solution. 60%, 10% to 50%, 20% to 50%.
  • the electrolyte contains 1% to 60%, 10% to 60%, 20% to 50%, 20% to 40%, or 30% propyl propionate based on the total weight of the electrolyte.
  • examples of additives may include, but are not limited to, one or more of the following: fluorocarbonates, ethylene carbonate containing carbon-carbon double bonds, compounds containing sulfur-oxygen double bonds, and acid anhydrides.
  • the additive is present in an amount of 0.01% to 15%, 0.1% to 10%, or 1% to 5% based on the total weight of the electrolyte.
  • the content of the propionate is 1.5 to 30 times, 1.5 to 20 times, 2 to 20 times, or 5 to 20 times that of the additive based on the total weight of the electrolyte.
  • the additive comprises one or more fluorocarbonates.
  • fluorocarbonate can act together with propionate to form a stable protective film on the surface of the negative electrode, thereby inhibiting the decomposition reaction of the electrolyte.
  • examples of fluorocarbonates may include, but are not limited to, one or more of the following: fluoroethylene carbonate, cis-4,4-difluoroethylene carbonate, trans-4,4 -Difluoroethylene carbonate, 4,5-difluoroethylene carbonate, 4-fluoro-4-methyl ethylene carbonate, 4-fluoro-5-methyl ethylene carbonate, trifluoromethyl methyl carbonate, carbonic acid Trifluoroethyl methyl ester and ethyl trifluoroethyl carbonate, etc.
  • the additive comprises one or more ethylene carbonates containing carbon-carbon double bonds.
  • carbon-carbon double bond-containing vinyl carbonates may include, but are not limited to, one or more of the following: vinylene carbonate, methyl vinylene carbonate, ethyl vinylene carbonate, 1,2 carbonate - Dimethyl vinylene carbonate, 1,2-diethyl vinylene carbonate, fluorovinylene carbonate, trifluoromethyl vinylene carbonate; vinyl ethylene carbonate, 1-methyl carbonate- 2-Vinylethylene carbonate, 1-ethyl-2-vinylethylene carbonate, 1-n-propyl-2-vinylethylene carbonate, 1-methyl-2-vinylethylene carbonate Ethyl carbonate, 1,1-divinylethylene carbonate, 1,2-divinylethylene carbonate, 1,1-dimethyl-2-methyleneethylene carbonate and carbonic acid- 1,1-Diethyl-2-methylene ethylene ester, etc.
  • the carbon-carbon double bond-containing vinyl carbonates may
  • the additive comprises one or more sulfur-oxygen double bond-containing compounds.
  • compounds containing sulfur-oxygen double bonds may include, but are not limited to, one or more of the following: cyclic sulfates, chain sulfates, chain sulfonates, cyclic sulfonates, chain sulfites esters and cyclic sulfites, etc.
  • cyclic sulfates may include, but are not limited to, one or more of the following: 1,2-ethylene glycol sulfate, 1,2-propylene glycol sulfate, 1,3-propylene glycol sulfate, 1,2 -Butanediol sulfate, 1,3-butanediol sulfate, 1,4-butanediol sulfate, 1,2-pentanediol sulfate, 1,3-pentanediol sulfate, 1,4 -Pentanediol sulfate and 1,5-pentanediol sulfate, etc.
  • chain sulfates may include, but are not limited to, one or more of the following: dimethyl sulfate, methyl ethyl sulfate, diethyl sulfate, and the like.
  • chain sulfonates may include, but are not limited to, one or more of the following: fluorosulfonates such as methyl fluorosulfonate and ethyl fluorosulfonate, methyl methanesulfonate, ethyl methanesulfonate , butyl dimethanesulfonate, methyl 2-(methanesulfonyloxy) propionate and ethyl 2-(methanesulfonyloxy) propionate, etc.
  • fluorosulfonates such as methyl fluorosulfonate and ethyl fluorosulfonate, methyl methanesulfonate, ethyl methanesulfonate , butyl dimethanesulfonate, methyl 2-(methanesulfonyloxy) propionate and ethyl 2-(methanesulfonyloxy) propionate, etc.
  • cyclic sulfonates may include, but are not limited to, one or more of the following: 1,3-propanesultone, 1-fluoro-1,3-propanesultone, 2-fluoro- 1,3-Propane sultone, 3-fluoro-1,3-propane sultone, 1-methyl-1,3-propane sultone, 2-methyl-1,3-propane sulfonate Acid lactone, 3-methyl-1,3-propane sultone, 1-propene-1,3-sultone, 2-propene-1,3-sultone, 1-fluoro-1 -Propene-1,3-sultone, 2-fluoro-1-propene-1,3-sultone, 3-fluoro-1-propene-1,3-sultone, 1-fluoro- 2-Propene-1,3-sultone, 2-fluoro-2-propene-1,3-sultone, 3-fluoro-2-propene-1,3-sultone,
  • chain sulfites may include, but are not limited to, one or more of the following: dimethyl sulfite, methyl ethyl sulfite, diethyl sulfite, and the like.
  • cyclic sulfites may include, but are not limited to, one or more of the following: 1,2-ethylene glycol sulfite, 1,2-propylene glycol sulfite, 1,3-propylene glycol sulfite , 1,2-butanediol sulfite, 1,3-butanediol sulfite, 1,4-butanediol sulfite, 1,2-pentanediol sulfite, 1,3-pentanediol sulfite Glycol sulfite, 1,4-pentanediol sulfite and 1,5-pentanediol sulfite, etc.
  • the additive comprises one or more acid anhydrides.
  • acid anhydrides may include, but are not limited to, one or more of cyclic phosphoric anhydrides, carboxylic acid anhydrides, disulfonic acid anhydrides, and carboxylic acid sulfonic acid anhydrides.
  • cyclic phosphoric anhydrides may include, but are not limited to, one or more of trimethylphosphoric acid cyclic anhydride, triethylphosphoric acid cyclic anhydride, and tripropylphosphoric acid cyclic anhydride.
  • carboxylic anhydrides may include, but are not limited to, one or more of succinic anhydride, glutaric anhydride, and maleic anhydride.
  • disulfonic anhydrides may include, but are not limited to, one or more of ethane disulfonic anhydride and propane disulfonic anhydride.
  • carboxylic acid sulfonic anhydride may include, but are not limited to, one or more of sulfobenzoic anhydride, sulfopropionic anhydride, and sulfobutyric anhydride.
  • the additive is a combination of a fluorocarbonate and a carbon-carbon double bond-containing ethylene carbonate. In some embodiments, the additive is a combination of a fluorocarbonate and a compound containing a sulfur-oxygen double bond. In some embodiments, the additive is a combination of a fluorocarbonate and a compound having 2-4 cyano groups. In some embodiments, the additive is a combination of a fluorocarbonate and a cyclic carboxylate. In some embodiments, the additive is a combination of fluorocarbonate and cyclic phosphoric anhydride. In some embodiments, the additive is a combination of a fluorocarbonate and a carboxylic acid anhydride. In some embodiments, the additive is a combination of fluorocarbonate and fluorine anhydride. In some embodiments, the additive is a combination of a fluorocarbonate and a carboxylic acid anhydride.
  • the electrolyte is not particularly limited, and any known electrolyte can be used.
  • lithium salts are generally used.
  • electrolytes may include, but are not limited to, inorganic lithium salts such as LiPF 6 , LiBF 4 , LiClO 4 , LiAlF 4 , LiSbF 6 , LiTaF 6 , LiWF 7 ; lithium tungstates such as LiWOF 5 ; HCO 2 Li, CH 3 CO 2 Li, CH 2 FCO 2 Li, CHF 2 CO 2 Li, CF 3 CO 2 Li, CF 3 CH 2 CO 2 Li, CF 3 CF 2 CO 2 Li, CF 3 CF 2 CO 2 Li, CF 3 CF 2 CF 2 CO 2 Li, CF 3 CF 2 CF 2 CO 2 Li and other carboxylate lithium salts; FSO 3 Li, CH 3 SO 3 Li, CH 2 FSO 3 Li, CHF 2 SO 3 Li, CF 3 SO 3 Li, CF 3 CF 2 SO 3 Li , CF 3 CF 2 SO
  • (malonate) Lithium borate salts tris(malonate) lithium phosphate, difluorobis(malonate) lithium phosphate, tetrafluoro(malonate) lithium phosphate, etc.
  • the electrolyte is selected from LiPF6, LiSbF6 , LiTaF6 , FSO3Li , CF3SO3Li , LiN( FSO2 )2 , LiN( FSO2 ) ( CF3SO2 ) , LiN(CF 3 SO 2 ) 2 , LiN(C 2 F 5 SO 2 ) 2 , cyclic 1,2-perfluoroethanebissulfonimide lithium, cyclic 1,3-perfluoropropanebissulfonimide lithium, LiC(FSO 2 ) 3 , LiC(CF 3 SO 2 ) 3 , LiC(C 2 F 5 SO 2 ) 3 , LiBF 3 CF 3 , LiBF 3 C 2 F 5 , LiPF 3 (CF 3 ) 3 , LiPF 3 ( C 2 F 5 ) 3 , lithium difluorooxalate borate, lithium bis(oxalate)borate or lithium difluorobis(oxal
  • the content of the electrolyte is not particularly limited as long as the effects of the present application are not impaired.
  • the total molar concentration of lithium in the electrolyte is greater than 0.3 mol/L, greater than 0.4 mol/L, or greater than 0.5 mol/L.
  • the total molar concentration of lithium in the electrolyte is less than 3 mol/L, less than 2.5 mol/L, or less than 2.0 mol/L.
  • the total molar concentration of lithium in the electrolyte is within a range consisting of any two of the above-mentioned values. When the electrolyte concentration is within the above-mentioned range, the amount of lithium as the charged particles is not too small, and the viscosity can be kept in an appropriate range, so that it is easy to ensure good electrical conductivity.
  • the electrolyte includes at least one salt selected from the group consisting of monofluorophosphate, borate, oxalate, and fluorosulfonate.
  • the electrolyte includes a salt selected from the group consisting of monofluorophosphate, oxalate, and fluorosulfonate.
  • the electrolyte includes a lithium salt.
  • the salt selected from the group consisting of monofluorophosphate, borate, oxalate, and fluorosulfonate is present in an amount greater than 0.01% or greater than 0.1% based on the total weight of the electrolyte.
  • the salt selected from the group consisting of monofluorophosphate, borate, oxalate, and fluorosulfonate is present in an amount of less than 20% or less than 10% based on the total weight of the electrolyte. In some embodiments, the amount of salt selected from the group consisting of monofluorophosphates, borates, oxalates, and fluorosulfonates is within a range consisting of any two of the foregoing values.
  • the electrolyte comprises one or more species selected from the group consisting of monofluorophosphates, borates, oxalates, and fluorosulfonates, and one or more salts in addition thereto.
  • Other salts include the lithium salts exemplified above, and in some examples, LiPF 6 , LiN(FSO 2 )(CF 3 SO 2 ), LiN(CF 3 SO 2 ) 2 , LiN ( C 2 F 5 SO 2 ) 2 , cyclic lithium 1,2-perfluoroethanebissulfonimide, cyclic lithium 1,3-perfluoropropanebissulfonimide, LiC(FSO 2 ) 3 , LiC (CF 3 SO 2 ) 3 , LiC(C 2 F 5 SO 2 ) 3 , LiBF 3 CF 3 , LiBF 3 C 2 F 5 , LiPF 3 (CF 3 ) 3 , LiPF 3 (C 2 F 5 ) 3 .
  • the other salts include the lithium salt
  • the salts other than these are present in an amount greater than 0.01% or greater than 0.1% based on the total weight of the electrolyte. In some embodiments, the additional salt is present in an amount of less than 20%, less than 15%, or less than 10% based on the total weight of the electrolyte. In some embodiments, the content of other salts is within the range composed of any two of the above-mentioned values. The other salts having the above-mentioned contents help to balance the conductivity and viscosity of the electrolyte.
  • the electrolytic solution may contain additional additives such as a negative electrode coating film forming agent, a positive electrode protective agent, and an overcharge inhibitor as necessary.
  • additives generally used in non-aqueous electrolyte secondary batteries can be used, and examples thereof can include, but are not limited to, vinylene carbonate, succinic anhydride, biphenyl, cyclohexylbenzene, 2,4-difluorobenzyl Ether, propane sultone, propene sultone, etc. These additives may be used alone or in any combination.
  • the content of these additives in the electrolytic solution is not particularly limited, and may be appropriately set according to the type and the like of the additives.
  • the additive is present in an amount of less than 5%, in the range of 0.01% to 5%, or in the range of 0.2% to 5%, based on the total weight of the electrolyte.
  • the negative electrode sheet includes a negative electrode current collector and a negative electrode mixture layer disposed on one or both surfaces of the negative electrode current collector.
  • the negative electrode mixture layer includes a negative electrode active material layer, and the negative electrode active material layer includes a negative electrode active material.
  • the negative electrode active material layer may be one or more layers, and each layer of the multilayered negative electrode active material may contain the same or different negative electrode active materials.
  • the negative electrode active material is any material that can reversibly intercalate and deintercalate metal ions such as lithium ions.
  • the chargeable capacity of the negative electrode active material is greater than the discharge capacity of the positive electrode active material to prevent unintentional precipitation of lithium metal on the negative electrode during charging.
  • a general coating such as a positive electrode can be provided on the surface of the negative electrode current collector in the region where the negative electrode mixture layer is not coated as required.
  • any known current collector can be used.
  • negative electrode current collectors include, but are not limited to, metal materials such as aluminum, copper, nickel, stainless steel, nickel-plated steel, and the like.
  • the anode current collector is copper.
  • the negative electrode current collector form may include, but is not limited to, metal foil, metal cylinder, metal coil, metal plate, metal film, metal mesh, stamped metal, foamed metal, etc.
  • the negative electrode current collector is a thin metal film.
  • the negative electrode current collector is copper foil.
  • the negative electrode current collector is a rolled copper foil based on a rolling method or an electrolytic copper foil based on an electrolytic method.
  • the thickness of the negative current collector is greater than 1 ⁇ m or greater than 5 ⁇ m. In some embodiments, the thickness of the negative current collector is less than 100 ⁇ m or less than 50 ⁇ m. In some embodiments, the thickness of the negative electrode current collector is within a range composed of any two of the above-mentioned values.
  • the negative electrode active material is not particularly limited as long as it can reversibly occlude and release lithium ions.
  • Examples of the negative electrode active material may include, but are not limited to, carbon materials such as natural graphite and artificial graphite; metals such as silicon (Si) and tin (Sn); or oxides of metal elements such as Si and Sn, and the like.
  • the negative electrode active materials may be used alone or in combination.
  • the negative electrode mixture layer may further include a negative electrode binder.
  • the negative electrode binder can improve the bonding of the negative electrode active material particles to each other and the bonding of the negative electrode active material to the current collector.
  • the type of the negative electrode binder is not particularly limited, as long as it is a material that is stable to the electrolyte solution or the solvent used in the production of the electrode.
  • the negative electrode binder includes a resin binder. Examples of resin binders include, but are not limited to, fluororesins, polyacrylonitrile (PAN), polyimide resins, acrylic resins, polyolefin resins, and the like.
  • the negative electrode binder includes, but is not limited to, carboxymethyl cellulose (CMC) or its salt, styrene-butadiene rubber (SBR), polyacrylic acid (PAA) or Its salts, polyvinyl alcohol, etc.
  • CMC carboxymethyl cellulose
  • SBR styrene-butadiene rubber
  • PAA polyacrylic acid
  • Its salts polyvinyl alcohol, etc.
  • the negative pole piece can be prepared by the following method: coating the negative electrode mixture slurry containing negative electrode active material, resin binder, etc. on the negative electrode current collector, after drying, calendering and forming the negative electrode mixture layer on both sides of the negative electrode current collector, by This results in a negative electrode.
  • a separator is usually provided between the positive electrode and the negative electrode.
  • the electrolytic solution of the present application is usually used by permeating the separator.
  • the material and shape of the separator are not particularly limited as long as the effects of the present application are not significantly impaired.
  • the separator may be a resin, glass fiber, inorganic substance, or the like formed of a material that is stable to the electrolyte of the present application.
  • the separator includes a porous sheet or a non-woven fabric-like substance with excellent liquid retention properties.
  • materials for resin or fiberglass separators may include, but are not limited to, polyolefins, aramids, polytetrafluoroethylene, polyethersulfone, glass filters, and the like.
  • the material of the isolation membrane is a glass filter.
  • the polyolefin is polyethylene or polypropylene.
  • the polyolefin is polypropylene.
  • the separator can also be a material formed by laminating the above materials, examples of which include, but are not limited to, a three-layer separator formed by laminating polypropylene, polyethylene, and polypropylene in the order.
  • inorganic materials may include, but are not limited to, oxides such as alumina and silica, nitrides such as aluminum nitride and silicon nitride, sulfates (eg, barium sulfate, calcium sulfate, etc.).
  • inorganic forms may include, but are not limited to, particulate or fibrous.
  • the form of the separator may be in the form of a thin film, examples of which include, but are not limited to, non-woven fabrics, woven fabrics, microporous membranes, and the like.
  • the separator has a pore size of 0.01 ⁇ m to 1 ⁇ m and a thickness of 5 ⁇ m to 50 ⁇ m.
  • a separator formed by forming a composite porous layer containing the above-mentioned inorganic particles on the surface of the positive electrode and/or the negative electrode sheet using a resin-based binder can also be used.
  • the membrane is, for example, a separator formed by using a fluororesin as a binder to form a porous layer of alumina particles having a particle size of less than 90% of 1 ⁇ m on both surfaces of the positive electrode.
  • the thickness of the separator is arbitrary. In some embodiments, the thickness of the isolation membrane is greater than 1 ⁇ m, greater than 5 ⁇ m, or greater than 8 ⁇ m. In some embodiments, the thickness of the isolation membrane is less than 50 ⁇ m, less than 40 ⁇ m, or less than 30 ⁇ m. In some embodiments, the thickness of the isolation film is within a range consisting of any two of the above-mentioned values. When the thickness of the separator is within the above range, insulating properties and mechanical strength can be secured, and the rate characteristics and energy density of the electrochemical device can be secured.
  • the porosity of the separator is arbitrary. In some embodiments, the porosity of the isolation membrane is greater than 20%, greater than 35%, or greater than 45%. In some embodiments, the isolation membrane has a porosity of less than 90%, less than 85%, or less than 75%. In some embodiments, the porosity of the isolation membrane is within a range consisting of any two of the foregoing values. When the porosity of the separator is within the above range, insulating properties and mechanical strength can be ensured, and membrane resistance can be suppressed, so that the electrochemical device has good rate characteristics.
  • the average pore diameter of the separator is also arbitrary. In some embodiments, the average pore size of the isolation membrane is less than 0.5 ⁇ m or less than 0.2 ⁇ m. In some embodiments, the isolating membrane has an average pore size greater than 0.05 ⁇ m. In some embodiments, the average pore size of the isolation membrane is within a range consisting of any two of the above-mentioned values. When the average pore diameter of the separator exceeds the above-mentioned range, a short circuit is likely to occur. When the average pore diameter of the separator is within the above range, the membrane resistance can be suppressed while preventing short circuit, so that the electrochemical device has good rate characteristics.
  • Electrochemical devices include electrode assemblies, current collection structures, housings, and protective elements.
  • the electrode assembly may have any of a laminated structure in which the positive electrode and the negative electrode are laminated with the separator interposed therebetween, and a structure in which the positive electrode and the negative electrode are wound in a spiral shape with the separator interposed therebetween.
  • the proportion of the mass of the electrode assembly to the internal volume of the battery is greater than 40% or greater than 50%.
  • the electrode assembly occupancy is less than 90% or less than 80%.
  • the occupancy rate of the electrode assembly is within a range composed of any two of the above-mentioned values.
  • the occupancy rate of the electrode assembly is within the above range, the capacity of the electrochemical device can be ensured, and the deterioration of characteristics such as repeated charge and discharge performance and high temperature storage associated with an increase in internal pressure can be suppressed, and the operation of the gas release valve can be prevented.
  • the outer surface of the electrode assembly can be further provided with the coating in the positive electrode of the present application.
  • the coatings of the present application can be disposed on some or all areas of the outer surface of the electrode assembly.
  • the current collecting structure is not particularly limited. In some embodiments, the current collecting structure is a structure that reduces the resistance of the wiring portion and the bonding portion.
  • the electrode assembly is of the above-described laminated structure, a structure in which the metal core portions of the respective electrode layers are bundled and welded to the terminals is suitably used.
  • the electrode area is increased, the internal resistance increases, so it is also suitable to provide two or more terminals in the electrode to reduce the resistance.
  • the internal resistance can be reduced by providing two or more lead structures on the positive electrode and negative electrode tabs and bundling them on the terminals.
  • the material of the case is not particularly limited as long as it is stable to the electrolyte solution used.
  • the case may be, but not limited to, nickel-plated steel sheet, stainless steel, aluminum or aluminum alloy, metal such as magnesium alloy, or a laminated film of resin and aluminum foil.
  • the housing is a metal or laminated film of aluminum or an aluminum alloy.
  • Metal-based housings include, but are not limited to, a hermetically sealed structure formed by welding metals to each other by laser welding, resistance welding, or ultrasonic welding, or a caulked structure using the above-mentioned metals via a resin gasket.
  • the case using the above-mentioned laminated film includes, but is not limited to, a hermetically sealed structure formed by thermally adhering resin layers to each other, and the like.
  • a resin different from the resin used for the laminated film may be interposed between the above-mentioned resin layers.
  • the shape of the housing is also arbitrary, and may be any of a cylindrical shape, a square shape, a laminated type, a button type, a large size, and the like, for example.
  • an adhesive layer is further provided on the surface of the coating layer provided on the outer surface of the electrode assembly. regional bonding and improve the structural stability of electrochemical devices.
  • the adhesion between the coating and the positive current collector is greater than or equal to the adhesion between the coating and the adhesion layer.
  • the protective element can use a positive temperature coefficient (PTC), a thermal fuse, a thermistor, whose resistance increases when abnormal heat is generated or an excessive current flows, and can be cut off by rapidly increasing the internal pressure or internal temperature of the battery when abnormal heat is generated A valve (current cutoff valve), etc. for the current flowing in the circuit.
  • PTC positive temperature coefficient
  • the above-mentioned protective element can be selected to be in a condition that does not work in the normal use of high current, and can also be designed in a form that does not cause abnormal heat release or thermal runaway even if there is no protective element.
  • the electrochemical device of the present application includes any device in which an electrochemical reaction occurs, and specific examples thereof include all kinds of primary batteries, secondary batteries, fuel cells, solar cells, or capacitors.
  • the electrochemical device is a lithium secondary battery, including a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery, or a lithium ion polymer secondary battery.
  • the present application further provides an electronic device comprising the electrochemical device according to the present application.
  • the use of the electrochemical device of the present application is not particularly limited, and it can be used in any electronic device known in the art.
  • the electrochemical devices of the present application may be used in, but are not limited to, notebook computers, pen input computers, mobile computers, e-book players, portable telephones, portable fax machines, portable copiers, portable printers, headsets stereo headphones, VCRs, LCD TVs, portable cleaners, portable CD players, mini discs, transceivers, electronic notepads, calculators, memory cards, portable recorders, radios, backup power, motors, cars, motorcycles, power Bicycles, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, large household batteries and lithium-ion capacitors, etc.
  • the selected thickness of aluminum foil is used as the positive electrode current collector, the insulating material and the binder are mixed according to the selected weight ratio, deionized water is added, and the system is stirred under the action of a vacuum mixer until the system becomes a uniform slurry to obtain a coating slurry , wherein the solid content is 40wt%; according to the size requirements of the pole piece, a layer of coating slurry is coated on the surface of the positive electrode current collector, and dried at 85°C to obtain a coated positive electrode current collector.
  • the positive active material lithium cobalt oxide (LiCoO2), the conductive agent SP, and the binder polyvinylidene fluoride are mixed according to the weight ratio of 97:1.4:1.6, and N-methylpyrrolidone (NMP) is added.
  • NMP N-methylpyrrolidone
  • the coatings were set up with corresponding parameters according to the conditions of the following examples and comparative examples.
  • the artificial graphite, styrene-butadiene rubber and sodium carboxymethyl cellulose are mixed with deionized water according to the mass ratio of 96%: 2%: 2%, and stirred evenly to obtain a negative electrode slurry.
  • This negative electrode slurry was coated on a 12 ⁇ m copper foil. After drying, cold pressing, cutting and welding the tabs, the negative electrode is obtained.
  • a polyethylene (PE) porous polymer film was used as the separator.
  • the obtained positive electrode, separator and negative electrode were wound in order and placed in an outer casing (outer packaging foil), leaving a liquid injection port.
  • the electrolyte is poured from the liquid injection port, and the lithium ion battery is prepared through the processes of chemical formation and capacity.
  • the paper tape is folded up, fixed with the upper fixture, and its cohesive force is tested with the high-speed rail AI-3000 tensile machine, and the tensile speed: the 50mm/min tensile displacement is determined according to the sample length;
  • the lithium-ion battery was punctured with nails under normal temperature conditions, using nails with a diameter of 2.5mm (steel nails, made of carbon steel, taper of 16.5mm, and total length of the steel nails of 100mm), punctured at a speed of 30mm/s, and the puncture depth
  • nails with a diameter of 2.5mm steel nails, made of carbon steel, taper of 16.5mm, and total length of the steel nails of 100mm
  • puncture depth Take the taper of the nail through the lithium-ion battery as the criterion, keep it for 300s after the nail is pierced, and observe whether the lithium-ion battery produces smoke, catches fire or explodes. If not, the lithium-ion battery is considered to pass the nail penetration test. Calculate the puncture pass rate of 10 electrochemical devices to be tested.
  • Table 1 shows the specific compositions of Examples 1-18 and Comparative Examples 1-3 and the corresponding coating adhesion and penetration rate. Wherein, the coating position is the end portion of the pole piece, and the width of the coating from the end edge is 150 mm.
  • the comparison between the examples and the comparative example 1 shows that the puncture pass rate of the comparative example 1 without the coating is 0/10, and it does not have the safety of the piercing test, while the comparative example 2 and the comparative example 3 are coated. coating, but its adhesive strength does not meet the requirements of the examples of the application, and the puncture pass rates of the electrochemical device are only 0/10 and 3/10, respectively, less than 50%, and the safety also fails to meet the requirements.
  • the coating adhesion reaches 5N/m in Example 1, and its puncture pass rate reaches 5/10, which meets the safety requirement of 50% pass rate.
  • the adhesion of the coating is further improved, and the puncture pass rate is further greatly improved.
  • Table 2 shows the required relationship between insulating materials with different average particle sizes and the coating thickness h.
  • the coating thickness h and the average particle size T of the insulating material satisfy the following conditions: compared with Comparative Examples 4-6, Examples 19-26 with h ⁇ 1.5 ⁇ T have a significantly improved puncture pass rate.
  • the average particle size of the insulating material is smaller than the thickness of the coating, the dispersion of the insulating material in the coating can be improved, so that the insulating material can be uniformly dispersed, thereby improving the isolation effect of the coating; on the other hand, When the average particle size of the insulating material is closer to the thickness of the coating, the binder content around the particle area of the insulating material is also less, which will reduce the adhesive force around the particle area of the insulating material, so that the The pierced current collector is stretched, resulting in a greatly reduced shading burr effect.
  • the thickness of the coating is greater than or equal to 1.5 times the average particle size of the insulating material, the coverage of the coating slurry on the surface of the current collector can be improved, thereby
  • Table 3 shows the influence of the relationship between the thickness h ( ⁇ m) of the coating and the elongation x of the current collector, the strength p (Mpa), and the thickness H ( ⁇ m) on the puncture pass rate.
  • Table 4 shows the effect of setting the coating slurry of Example 5 at the side portion of the positive electrode and the tab on the puncture pass rate
  • Comparative Example 8 The side part of the pole piece is not covered Electrode assembly side part 0/10 Comparative Example 9 No coverage at the tabs pole ear 0/10 Example 34 The side part of the pole piece is completely covered Electrode assembly side part 10/10 Example 35 Full coverage at the tabs pole ear 10/10
  • the results show that the coating of the present application is provided on the side part of the positive electrode and the tab, which can greatly improve the puncture pass rate of the nail penetration test on the corresponding part of the electrochemical device, and ensure the safety performance of the electrode assembly.
  • Table 5 shows the effect of the molecular weight of the binder in the coating on the penetration rate
  • the molecular weight of the binder in the scope of the embodiments of the present application can maintain the adhesion of the coating to the current collector, so as to ensure the safety performance of the electrode assembly.
  • Table 6 shows the effect of the difference in the adhesion of the coating to the current collector and the bonding layer on the puncture pass rate
  • the positive electrode of the present application is coated with a coating with high adhesive force on the surface of the positive electrode current collector without the positive electrode active material layer covering the area, and the pass rate of the piercing test of the lithium ion battery is There will be a huge improvement, significantly improving the safety performance of lithium-ion batteries.

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Abstract

本申请涉及一种改善电极组件安全性的极片及包含其的电化学装置、电子装置。本申请提供一种正极，其包括正极集流体、正极活性物质层及涂层，其中正极活性物质层及涂层设置于正极集流体的表面上，涂层与正极集流体的粘结力大于或等于5N/m。本申请的正极通过设置涂层及对涂层与正极集流体的设计，并提高涂层对正极集流体的粘结力，能够有效提高其电极组件的安全性能。当本申请的电化学装置受到外力冲击或穿刺时，具有高粘结力的涂层能够提高其电极组件的结构稳定性，并降低极片与极片间的短路发生率，进而提高电化学装置的安全性能。

Description

一种改善电极组件安全性的极片及包含其的电化学装置、电子装置 技术领域
本申请涉及储能领域，具体涉及一种改善电极组件安全性的极片及包含其的电化学装置及电子装置，特别是锂离子电池。
背景技术
随着技术的发展和对移动装置的需求的增加，人们对电化学装置(例如，锂离子电池)的需求显著增加。同时具有高安全性的锂离子电池是研究方向之一。
在实际使用中，电化学装置会受到外物的撞击，在极端情况下，会被尖锐的物体所刺穿，当电化学装置被刺穿时，一方面，如果刺穿物为金属体，集流体的刺穿处通过该金属体而与另一电极导通；另一方面，集流体的刺穿处通常会产生毛刺、并随着刺穿物向下变形延伸，从而刺穿隔膜将正负极直接连通，上述两种状况都有可能导致短路的发生，进而产生大量热量使得锂离子电池起火甚至爆炸，严重威胁了消费者的使用安全。
有鉴于此，确有必要对电极极片进行研究与改进，以提升其电化学装置和电子装置使用上的安全性。
发明内容
本申请实施例通过提供一种改善电极组件安全性的极片及包含其的电化学装置以在至少某种程度上解决至少一种存在于相关领域中的问题。
在本申请的一方面，本申请提供了一种正极，该正极包括正极集流体、正极活性物质层及涂层，其中正极活性物质层及涂层设置于正极集流体的表面上，且涂层与正极集流体之间的粘结力大于或等于5N/m。
在本申请的另一方面，本申请提供一种电化学装置，其包括上述实施例中的正极。
本申请的正极通过设置涂层及对涂层与正极集流体的设计，并提高涂层对正极集流体的粘结力，能够有效提高其电极组件的安全性能。当本申请的电化学装置受到外力冲击或穿刺时，具有高粘结力的涂层能够提高其电极组件的结构稳定 性，并降低极片与极片间的短路发生率，进而提高电化学装置的安全性能。
在本申请的另一方面，本申请提供一种电子装置，其包括上述电化学装置。
本申请实施例的额外层面及优点将部分地在后续说明中描述、显示、或是经由本申请实施例的实施而阐释。
附图说明
在下文中将简要地说明为了描述本申请实施例或现有技术所必要的附图以便于描述本申请的实施例。
图1为根据本申请一些实施例的正极的结构示意图。
图2为根据本申请一些实施例的正极的结构示意图。
图3为根据本申请一些实施例的正极的剖面结构示意图。
图4为根据本申请一些实施例的正极的俯视结构示意图。
图5为根据本申请一些实施例的正极的俯视结构示意图。
图6为根据本申请一些实施例的正极的俯视结构示意图。
具体实施方式
本申请的实施例将会被详细的描示在下文中。本申请的实施例不应该被解释为对本申请的限制。
除非另外明确指明，本文使用的下述术语具有下文指出的含义。
在具体实施方式及权利要求书中，由术语“中的至少一者”、“中的至少一个”、“中的至少一种”或其他相似术语所连接的项目的列表可意味着所列项目的任何组合。例如，如果列出项目A及B，那么短语“A及B中的至少一者”意味着仅A；仅B；或A及B。在另一实例中，如果列出项目A、B及C，那么短语“A、B及C中的至少一者”意味着仅A；或仅B；仅C；A及B(排除C)；A及C(排除B)；B及C(排除A)；或A、B及C的全部。项目A可包含单个元件或多个元件。项目B可包含单个元件或多个元件。项目C可包含单个元件或多个元件。
再者，为便于描述，“第一”、“第二”、“第三”等等可在本文中用于区分一个图或一系列图的不同组件。除非经特别指定或限定之外，“第一”、“第二”、“第 三”等等不意欲描述对应组件。
电化学装置(例如，锂离子电池)的电极(正极或负极)通常通过以下方法制备：将活性物质、导电剂、增稠剂、粘结剂和溶剂混合，然后将混合后的浆料涂布于集流体上以形成活性物质层。当电化学装置被刺穿时，一方面，如果刺穿物为金属体，集流体的刺穿处通过该金属体而与另一电极导通；另一方面，集流体的刺穿处通常会产生毛刺、并随着刺穿物向下变形延伸，从而刺穿隔膜将正负极直接连通，导致短路的发生。
本申请通过对正极的设计与改进使其电化学装置在受到异物穿刺或撞击的过程中的避免了集流体与金属穿刺物、集流体毛刺与另一电极的接触，从而改善了电化学装置的安全性。本申请的正极是通过在集流体表面涂覆具有高粘结力的涂层来实现，作为粘结力的控制方法，可以通过在涂层浆料中调控粘结剂种类、粘结剂与绝缘材料的组成配比来控制。
在本申请的一方面，本申请提供了一种正极，其包括如下所述的涂层及正极活性物质层。
I、正极
现参考图1至图3，正极10包括正极集流体101和设置在正极集流体101的表面上的正极活性物质层102和涂层103，其中正极活性物质层102设置于正极集流体的表面上的第一部分1011，涂层设置于正极集流体的表面上的第二部分1012。
在一些实施例中，正极集流体的表面上的第二部分1012不同于第一部分1011。在一些实施例中，第二部分为未涂覆的正极活性物质层的部分区域，其包括，但不限于，正极集流体的侧边部分、正极集流体的端部部分、正极活性物质层的涂覆间歇处或极耳处。
如图1及图2所示，在一些实施例中，正极活性物质层及涂层可以单面或双面设置于正极集流体的表面上。
应理解，虽然图1及图2的涂层与正极活性物质层之间不存间隔，然而其仅为用于说明涂层与正极活性物质层设置关系的示范例。如图3所示，在一些实施例中，涂层与正极活性物质层之间能够存在间隔距离。在一些实施例中，涂层与 正极活性物质层之间的间隔距离小于或等于3mm。
在一些实施例中，如图4所示，涂层设置于正极集流体长度方向的端部部分。在一些实施例中，涂层沿正极集流体长度方向的宽度小于或等于200mm。在一些实施例中，涂层沿正极集流体长度方向的宽度为约150mm。应理解，虽然图4的涂层仅设置在正极集流体的单一端部部分，然而其仅为用于说明涂层设置关系的示范例。在一些实施例中，涂层可以设置于正极集流体的单一端部部分或双端部部分。在一些实施例中，正极集流体与涂层相对的表面至少部分地设置有正极活性物质层。
在一些实施例中，如图5所示，涂层设置于正极集流体宽度方向的侧边部分。在一些实施例中，涂层在正极集流体宽度方向上的宽度小于或等于5mm。在一些实施例中，涂层在正极集流体宽度方向上的宽度为约2mm。在一些实施例中，正极能够沿正极集流体宽度方向的边缘设置涂层。
在一些实施例中，如图6所示，涂层设置于正极集流体沿长度方向上的正极活性物质层的涂覆间歇处。在一些实施例中，涂层的涂覆宽度小于或等于10mm。在一些实施例中，涂层的涂覆宽度为约5mm。本申请通过控制涂层设置于正极活性物质层的涂覆间歇处的涂覆宽度，能够进一步降低电极组件受到来自侧边的外力冲击或穿刺所可能导致的损害，同时提高电极组件在卷绕结构或叠片结构中的结构稳定度。
根据本申请的一些实施例，涂层设置于正极集流体长度方向的端部、正极集流体宽度方向的边缘以及正极活性物质层沿正极集流体长度方向的间隔处中的至少一处。
根据本申请的一些实施例，正极包括正极极耳，正极极耳表面存在涂层。
在一些实施例中，涂层设置于正极集流体的表面上全部未涂覆的正极活性物质层的区域。应理解，图3至图5所演示的涂层设置位置旨为用于提供说明的示范性实施例，在不违背本申请精神下，本领域技术人员可根据实际需要调整或结合各个实施例的涂层设置位置，而不受其限制。
1、涂层
根据本申请的一些实施例，涂层对正极集流体的粘结力至少大于或等于 5N/m。
本申请设置涂层的正极，通过限定涂层对正极集流体的粘结力，能够有效的提高涂层对正极集流体的保护性，进而降低收到外力穿刺或撞击时所可能产生的短路现象。在另一些实施例中，涂层对正极集流体的粘结力大于或等于10N/m。在另一些实施例中，涂层对正极集流体的粘结力大于或等于30N/m。
根据本申请的一些实施例，涂层包括粘结剂。在一些实施例中，粘结剂为胶状的高分子聚合物。
根据本申请的一些实施例，粘结剂包括聚偏氟乙烯PVDF、聚四氟乙烯PTFE、羧甲基纤维素钠CMC、丁苯橡胶SBR、丁腈橡胶、聚胺酯、氟化橡胶、聚乙烯醇PVA、聚丙烯酸钠中的至少一种。在一些实施例中，粘结剂的分子量大于或等于10kDa。在另一些实施例中，粘结剂的分子量大于或等于100kDa。
根据本申请的一些实施例，涂层还包括绝缘材料。绝缘材料可以是固态的粉状、片状或块状材料。
根据本申请的一些实施例，基于涂层的重量，粘结剂的质量百分比为2％至100％。在一些实施例中，涂层由粘结剂及绝缘材料所组成。
根据本申请的一些实施例，绝缘材料包括无机绝缘材料或有机绝缘材料中的至少一种。
根据本申请的一些实施例，无机绝缘材料包括含Ba、Ca、Al、Si、Ti、Mg、Fe、B中至少一种元素的无机绝缘材料。
根据本申请的一些实施例，无机绝缘材料包括BaSO 4、CaSiO 3、CaSiO 4、γ-AlOOH、Al 2O 3、TiO 2、SiO 2、SiC、SiN、MgO、Fe 2O 3、BN中的至少一种。
根据本申请的一些实施例，有机绝缘材料包括以下组分的均聚物或共聚物中的至少一种：乙烯、氯乙烯、丙烯、苯乙烯、丁二烯、偏氟乙烯、四氟乙烯及六氟丙烯。在一些实施例中，有机绝缘材料的分子量大于或等于50kDa。
根据本申请的一些实施例，绝缘材料的平均粒径T为0.1μm至20μm。在一些实施例中，绝缘材料的平均粒径T为0.5μm至5μm。
在本文中，术语“平均粒径”为样本颗粒的粒径R的平均值。举例而言，对本申请绝缘材料颗粒的平均粒径的测量方法如下：首先，沿垂直于正极集流体方向制备横截面，使用扫描电子显微镜(以下简称为“SEM”)，拍摄该横截面SEM图像。然后，使用图像解析软件，从涂层横截面SEM图像中随机地选出10 个绝缘材料颗粒，并计算得到绝缘材料颗粒各自的在SEM图像中的截面积，通过以下公式获得绝缘材料颗各自的粒径R(直径)：
R＝2×(S/π) 1/2；其中，S为绝缘材料颗粒的面积；
对30张SEM图像进行上述绝缘材料颗粒的粒径R的计算，并将所得300个绝缘材料颗粒的粒径R进行算数平均，从而求得绝缘材料颗粒的平均粒径T。
根据本申请的一些实施例，涂层的厚度大于或等于0.5μm。
根据本申请的一些实施例，涂层与其绝缘材料的关系满足以下条件：
h≥1.5×T，
其中，h为涂层的厚度，T为绝缘材料的平均粒径。满足上述条件的涂层中的绝缘材料及粘结剂能够进一步获得良好的均匀分散，并使得涂层在正极集流体表面上能够均匀的覆盖，同时还能提高涂层对正极集流体表面的总体粘结力，进而能够有效的提高涂层覆盖区域的保护性。
2、正极活性物质层
正极活性物质层包含正极活性物质。正极活性物质层可以是一层或多层，多层正极活性物质中的每层可以包含相同或不同的正极活性物质。正极活性物质为任何能够可逆地嵌入和脱嵌锂离子等金属离子的物质。在一些实施例中，正极活性物质的放电容量小于负极活性物质的可充电容量，以防止在充电期间锂金属无意地析出在负极上。
正极活性物质的种类没有特别限制，只要是能够以电化学方式吸藏和释放金属离子(例如，锂离子)即可。在一些实施例中，正极活性物质为含有锂和至少一种过渡金属的物质。正极活性物质的实例可包括，但不限于，锂过渡金属复合氧化物和含锂过渡金属磷酸化合物。
在一些实施例中，锂过渡金属复合氧化物中的过渡金属包括V、Ti、Cr、Mn、Fe、Co、Ni、Cu等。在一些实施例中，锂过渡金属复合氧化物包括LiCoO 2等锂钴复合氧化物；LiNiO 2等锂镍复合氧化物；LiMnO 2、LiMn 2O 4、Li 2MnO 4等锂锰复合氧化物；LiNi 1/3Mn 1/3Co 1/3O 2、LiNi 0.5Mn 0.3Co 0.2O 2等锂镍锰钴复合氧化物，其中作为这些锂过渡金属复合氧化物的主体的过渡金属原子的一部分被Na、K、B、F、Al、Ti、V、Cr、Mn、Fe、Co、Li、Ni、Cu、Zn、Mg、Ga、Zr、 Si、Nb、Mo、Sn、W等其它元素所取代。锂过渡金属复合氧化物的实例可包括，但不限于，LiNi 0.5Mn 0.5O 2、LiNi 0.85Co 0.10Al 0.05O 2、LiNi 0.33Co 0.33Mn 0.33O 2、LiNi 0.45Co 0.10Al 0.45O 2、LiMn 1.8Al 0.2O 4和LiMn 1.5Ni 0.5O 4等。锂过渡金属复合氧化物的组合的实例包括，但不限于，LiCoO 2与LiMn 2O 4的组合，其中LiMn 2O 4中的一部分Mn可被过渡金属所取代(例如，LiNi 0.33Co 0.33Mn 0.33O 2)，LiCoO 2中的一部分Co可被过渡金属所取代。
在一些实施例中，含锂过渡金属磷酸化合物中的过渡金属包括V、Ti、Cr、Mn、Fe、Co、Ni、Cu等。在一些实施例中，含锂过渡金属磷酸化合物包括LiFePO 4、Li 3Fe 2(PO 4) 3、LiFeP 2O 7等磷酸铁类、LiCoPO 4等磷酸钴类，其中作为这些锂过渡金属磷酸化合物的主体的过渡金属原子的一部分被Al、Ti、V、Cr、Mn、Fe、Co、Li、Ni、Cu、Zn、Mg、Ga、Zr、Nb、Si等其它元素所取代。
在一些实施例中，使用锂过渡金属氧化物Li aM bO 2的粉末状材料，其中0.9＜a＜1.1，0.9＜b＜1.1，且M主要是选自Mn、Co和Ni的过渡金属，其中，组成M随粒度改变。
在一些实施例中，在锂过渡金属氧化物Li aM bO 2的粉末状的电极活性物质中，其中M＝A ZA’ Z’M’ 1-Z-Z’，M’＝Mn xNi yCo 1-x-y，0≤y≤1，0≤x≤1，0≤Z+Z’＜0.1，Z’＜0.02，A选自元素Al、Mg、Ti、Cr中至少一种，且A’选自元素F、Cl、S、Zr、Ba、Y、Ca、B、Be、Sn、Sb、Na、Zn中的至少一种。
在一些实施例中，过渡金属平均组成是M＝Mn xNi yCo 1-x-y，其中0.03＜x＜0.35。
在一些实施例中，过渡金属平均组成是M＝Mn xNi yCo 1-x-y，其中0.03＜x，且x+y＜0.7。
在一些实施例中，在具有组成与尺寸相关的Li aM bO 2的粉末状的电极活性物质中，基本上所有颗粒的所有部分具有层状晶体结构，较大颗粒具有组成Li aM bO 2，其中M＝Mn xNi yCo 1-x-y，x+y＜0.35，小颗粒具有组成Li aM bO 2，其中M＝Mn x’Ni y’Co 1-x’-y’，其具有至少低10％的Co，(1-x’-y’)＜0.9×(1-x-y)，以及至少高5％的Mn，x’-x＞0.05。由此，可以获得具有组成与尺寸相关的粉末，也即一种成分具有大的颗粒(例如分布集中在≥20μm)；其成分能够快速体相扩散。另一种成分具有小的颗粒(例如分布于5μm周围)且其成分能确保安全性。从而提供将高循环稳定性和高安全性与高体积能量密度和高重量能量密度结合起来的电 极活性物质。
在一些实施例中，正极活性物质具有宽的粒度分布，其规定为大颗粒与小颗粒的粒度比大于3，Dv90/Dv10>3，其中，Dv90表示在体积基准的粒度分布中，从小粒径侧起、达到体积累积90％的粒径。Dv10表示在体积基准的粒度分布中，从小粒径侧起、达到体积累积10％的粒径。粉末的粒度分布可以通过现有技术中已知的适当方法测定。适当的方法例如激光衍射或通过使用具有不同目数的套筛进行筛分。
在一些实施例中，单个颗粒基本上是锂过渡金属氧化物，且单个颗粒具有Co，其在过渡金属中的含量随粒度连续提高。
在一些实施例中，单个颗粒在过渡金属中还含有Mn，且Mn含量随粒度连续降低。
在一些实施例中，大颗粒具有能获得高Li扩散常数的接近于LiCoO 2组成的大颗粒，因此能获得足够的速率性能。大颗粒仅占正极的总表面积的小部分。因此，由在表面或在外侧部分与电解质反应放出的热量得到限制；结果，大的颗粒较少导致差的安全性。小颗粒具有含有较少Co的组成以获得提高的安全性。较低的锂扩散常数在小颗粒中可以被接受而没有明显的速率性能的损失，这是由于固态扩散路径的长度短。
在一些实施例中，小颗粒的优选组成含有较少量的Co和较大量的稳定元素，如Mn。较缓慢的Li体扩散可以被接受，但表面的稳定性高。在本申请的正极活性物质粉末中，大颗粒的优选组成含有较大量的Co和较少量的Mn，这是由于需要快速的锂体扩散，而表面稍低的稳定性可以被接受。
在一些实施例中，在组成为Li xMO 2的单个颗粒的内部中，优选至少80w％的M是钴或镍。在一些实施例中，颗粒的内侧部分具有接近于LiCoO2的组成。外侧部分是锂锰镍钴氧化物。
制备具有组成与尺寸相关的粉末状的电极活性物质可以通过如下方法：将至少一种含有过渡金属的沉淀物沉积在晶种颗粒上，晶种颗粒具有与沉淀物不同的过渡金属组成；添加控制量的锂源；并进行至少一种热处理，其中基本上所有获得的颗粒含有得自晶种的内核，该内核完全被得自沉淀物的层覆盖。
3、正极集流体
正极集流体的种类没有特别限制可以是本领域中的任何合适的材料。举例而言，在一些实施例中，正极集流体为铝箔。
在一些实施例中，正极集流体的延展率范围x：1.5％至3.5％。
在一些实施例中，正极集流体的强度范围p：100Mpa至300Mpa。
在一些实施例中，正极集流体的厚度范围H：5μm至20μm。
根据本申请的一些实施例，涂层与正极集流体的关系满足以下条件：
h≥(H×p×x)/k，
其中h为涂层的厚度，x为正极集流体的延展率，p为正极集流体的强度，H为正极集流体的厚度，且k＝100MPa。本申请实施例的涂层，通过限定涂层的厚度与正极集流体的延展率、强度及厚度的关系，能够进一步防止正极集流体在收到穿刺时的变形所形成的金属尖刺，进而降低正极集流体与其他邻近的集流体的短路情形。
在一些实施例中，正极集流体的表面粗糙度范围：0.01μm至5μm。本申请实施例的正极，通过限定正极集流体的表面粗糙度，能够进一步提高设置在正极集流体表面上的涂层及正极活性物质层的结构稳定性，以及正极的电性能。
II、电解液
本申请的电化学装置中的使用的电解液包括电解质和溶解该电解质的溶剂。在一些实施例中，本申请的电化学装置中的使用的电解液进一步包括添加剂。
在一些实施例中，电解液进一步包含现有技术中已知的任何可作为电解液的溶剂的非水溶剂。
在一些实施例中，非水溶剂包括，但不限于，以下中的一种或多种：环状碳酸酯、链状碳酸酯、环状羧酸酯、链状羧酸酯、环状醚、链状醚、含磷有机溶剂、含硫有机溶剂和芳香族含氟溶剂。
在一些实施例中，环状碳酸酯的实例可包括，但不限于，以下中的一种或多种：碳酸亚乙酯(EC)、碳酸亚丙酯(PC)和碳酸亚丁酯。在一些实施例中，环状碳酸酯具有3-6个碳原子。
在一些实施例中，链状碳酸酯的实例可包括，但不限于，以下中的一种或多种：碳酸二甲酯、碳酸甲乙酯、碳酸二乙酯(DEC)、碳酸甲基正丙基酯、碳酸乙基正丙基酯、碳酸二正丙酯等链状碳酸酯等。被氟取代的链状碳酸酯的实例可包括，但不限于，以下中的一种或多种：双(氟甲基)碳酸酯、双(二氟甲基)碳酸酯、双(三氟甲基)碳酸酯、双(2-氟乙基)碳酸酯、双(2,2-二氟乙基)碳酸酯、双(2,2,2-三氟乙基)碳酸酯、2-氟乙基甲基碳酸酯、2,2-二氟乙基甲基碳酸酯和2,2,2-三氟乙基甲基碳酸酯等。
在一些实施例中，环状羧酸酯的实例可包括，但不限于，以下中的一种或多种：γ-丁内酯和γ-戊内酯中的一种或多种。在一些实施例中，环状羧酸酯的部分氢原子可被氟取代。
在一些实施例中，链状羧酸酯的实例可包括，但不限于，以下中的一种或多种：乙酸甲酯、乙酸乙酯、乙酸丙酯、乙酸异丙酯、乙酸丁酯、乙酸仲丁酯、乙酸异丁酯、乙酸叔丁酯、丙酸甲酯、丙酸乙酯、丙酸丙酯、丙酸异丙酯、丁酸甲酯、丁酸乙酯、丁酸丙酯、异丁酸甲酯、异丁酸乙酯、戊酸甲酯、戊酸乙酯、特戊酸甲酯和特戊酸乙酯等。在一些实施例中，链状羧酸酯的部分氢原子可被氟取代。在一些实施例中，氟取代的链状羧酸酯的实例可包括，但不限于，三氟乙酸甲酯、三氟乙酸乙酯、三氟乙酸丙酯、三氟乙酸丁酯和三氟乙酸2,2,2-三氟乙酯等。
在一些实施例中，环状醚的实例可包括，但不限于，以下中的一种或多种：四氢呋喃、2-甲基四氢呋喃、1,3-二氧戊环、2-甲基1,3-二氧戊环、4-甲基1,3-二氧戊环、1,3-二氧六环、1,4-二氧六环和二甲氧基丙烷。
在一些实施例中，链状醚的实例可包括，但不限于，以下中的一种或多种：二甲氧基甲烷、1,1-二甲氧基乙烷、1,2-二甲氧基乙烷、二乙氧基甲烷、1,1-二乙氧基乙烷、1,2-二乙氧基乙烷、乙氧基甲氧基甲烷、1,1-乙氧基甲氧基乙烷和1,2-乙氧基甲氧基乙烷等。
在一些实施例中，含磷有机溶剂的实例可包括，但不限于，以下中的一种或多种：磷酸三甲酯、磷酸三乙酯、磷酸二甲基乙酯、磷酸甲基二乙酯、磷酸亚乙基甲酯、磷酸亚乙基乙酯、磷酸三苯酯、亚磷酸三甲酯、亚磷酸三乙酯、亚磷酸三苯酯、磷酸三(2,2,2-三氟乙基)酯和磷酸三(2,2,3,3,3-五氟丙基)酯等。
在一些实施例中，含硫有机溶剂的实例可包括，但不限于，以下中的一种或 多种：环丁砜、2-甲基环丁砜、3-甲基环丁砜、二甲基砜、二乙基砜、乙基甲基砜、甲基丙基砜、二甲基亚砜、甲磺酸甲酯、甲磺酸乙酯、乙磺酸甲酯、乙磺酸乙酯、硫酸二甲酯、硫酸二乙酯和硫酸二丁酯。在一些实施例中，含硫有机溶剂的部分氢原子可被氟取代。
在一些实施例中，芳香族含氟溶剂包括，但不限于，以下中的一种或多种：氟苯、二氟苯、三氟苯、四氟苯、五氟苯、六氟苯和三氟甲基苯。
在一些实施例中，本申请的电解液中使用的溶剂包括环状碳酸酯、链状碳酸酯、环状羧酸酯、链状羧酸酯及其组合。在一些实施例中，本申请的电解液中使用的溶剂包括碳酸亚乙酯、碳酸亚丙酯、碳酸二乙酯、丙酸乙酯、丙酸丙酯、乙酸正丙酯、或乙酸乙酯中的至少一种。在一些实施例中，本申请的电解液中使用的溶剂包含：碳酸亚乙酯、碳酸亚丙酯、碳酸二乙酯、丙酸乙酯、丙酸丙酯、γ-丁内酯及其组合。
在电解液中加入链状羧酸酯及/或环状羧酸酯后，链状羧酸酯及/或环状羧酸酯可在电极表面形成钝化膜，从而提高电化学装置的间歇充电循环后的容量保持率。在一些实施例中，电解液中含有1％至60％的链状羧酸酯、环状羧酸酯及其组合。在一些实施例中，电解液中含有丙酸乙酯、丙酸丙酯、γ-丁内酯及其组合，基于电解液的总重量，该组合的含量为1％至60％、10％至60％、10％至50％、20％至50％。在一些实施例中，基于电解液的总重量，电解液中含有1％至60％、10％至60％、20％至50％、20％至40％或30％的丙酸丙酯。
在一些实施例中，添加剂的实例可包括，但不限于，以下的一种或多种：氟代碳酸酯、含碳碳双键的碳酸乙烯酯、含硫氧双键的化合物和酸酐。
在一些实施例中，基于电解液的总重量，添加剂的含量为0.01％至15％、0.1％至10％或1％至5％。
根据本申请的实施例，基于电解液的总重量，丙酸酯的含量为添加剂的1.5至30倍、1.5至20倍、2至20倍或5-20倍。
在一些实施例中，添加剂包含一种或多种氟代碳酸酯。在锂离子电池充电/放电时，氟代碳酸酯可与丙酸酯共同作用以在负极的表面上形成稳定的保护膜，从而抑制电解液的分解反应。
在一些实施例中，氟代碳酸酯具有式C＝O(OR 1)(OR 2)，其中R 1和R 2各自选自具有1-6个碳原子的烷基或卤代烷基，其中R 1和R 2中的至少一者选自具有1-6 个碳原子的氟代烷基，且R 1和R 2任选地连同其所连接的原子形成5元至7元环。
在一些实施例中，氟代碳酸酯的实例可包括，但不限于，以下的一种或多种：氟代碳酸乙烯酯、顺式4,4-二氟碳酸乙烯酯、反式4,4-二氟碳酸乙烯酯、4,5-二氟碳酸乙烯酯、4-氟-4-甲基碳酸乙烯酯、4-氟-5-甲基碳酸乙烯酯、碳酸三氟甲基甲酯、碳酸三氟乙基甲酯和碳酸乙基三氟乙酯等。
在一些实施例中，添加剂包含一种或多种含碳碳双键的碳酸乙烯酯。含碳碳双键的碳酸乙烯酯的实例可包括，但不限于，以下的一种或多种：碳酸亚乙烯酯、碳酸甲基亚乙烯酯、碳酸乙基亚乙烯酯、碳酸-1,2-二甲基亚乙烯酯、碳酸-1,2-二乙基亚乙烯酯、碳酸氟亚乙烯酯、碳酸三氟甲基亚乙烯酯；碳酸乙烯基亚乙酯、碳酸-1-甲基-2-乙烯基亚乙酯、碳酸-1-乙基-2-乙烯基亚乙酯、碳酸-1-正丙基-2-乙烯基亚乙酯、碳酸1-甲基-2-乙烯基亚乙酯、碳酸-1,1-二乙烯基亚乙酯、碳酸-1,2-二乙烯基亚乙酯、碳酸-1,1-二甲基-2-亚甲基亚乙酯和碳酸-1,1-二乙基-2-亚甲基亚乙酯等。在一些实施例中，含碳碳双键的碳酸乙烯酯包括碳酸亚乙烯酯，其易于获得并可实现更为优异的效果。
在一些实施例中，添加剂包含一种或多种含硫氧双键的化合物。含硫氧双键的化合物的实例可包括，但不限于，以下的一种或多种：环状硫酸酯、链状硫酸酯、链状磺酸酯、环状磺酸酯、链状亚硫酸酯和环状亚硫酸酯等。
环状硫酸酯的实例可包括，但不限于，以下的一种或多种：1,2-乙二醇硫酸酯、1,2-丙二醇硫酸酯、1,3-丙二醇硫酸酯、1,2-丁二醇硫酸酯、1,3-丁二醇硫酸酯、1,4-丁二醇硫酸酯、1,2-戊二醇硫酸酯、1,3-戊二醇硫酸酯、1,4-戊二醇硫酸酯和1,5-戊二醇硫酸酯等。
链状硫酸酯的实例可包括，但不限于，以下的一种或多种：硫酸二甲酯、硫酸甲乙酯和硫酸二乙酯等。
链状磺酸酯的实例可包括，但不限于，以下的一种或多种：氟磺酸甲酯和氟磺酸乙酯等氟磺酸酯、甲磺酸甲酯、甲磺酸乙酯、二甲磺酸丁酯、2-(甲磺酰氧基)丙酸甲酯和2-(甲磺酰氧基)丙酸乙酯等。
环状磺酸酯的实例可包括，但不限于，以下的一种或多种：1,3-丙磺酸内酯、1-氟-1,3-丙磺酸内酯、2-氟-1,3-丙磺酸内酯、3-氟-1,3-丙磺酸内酯、1-甲基-1,3-丙磺酸内酯、2-甲基-1,3-丙磺酸内酯、3-甲基-1,3-丙磺酸内酯、1-丙烯-1,3-磺酸内酯、2-丙烯-1,3-磺酸内酯、1-氟-1-丙烯-1,3-磺酸内酯、2-氟-1-丙烯-1,3-磺酸内 酯、3-氟-1-丙烯-1,3-磺酸内酯、1-氟-2-丙烯-1,3-磺酸内酯、2-氟-2-丙烯-1,3-磺酸内酯、3-氟-2-丙烯-1,3-磺酸内酯、1-甲基-1-丙烯-1,3-磺酸内酯、2-甲基-1-丙烯-1,3-磺酸内酯、3-甲基-1-丙烯-1,3-磺酸内酯、1-甲基-2-丙烯-1,3-磺酸内酯、2-甲基-2-丙烯-1,3-磺酸内酯、3-甲基-2-丙烯-1,3-磺酸内酯、1,4-丁磺酸内酯、1,5-戊磺酸内酯、甲烷二磺酸亚甲酯和甲烷二磺酸亚乙酯等。
链状亚硫酸酯的实例可包括，但不限于，以下的一种或多种：亚硫酸二甲酯、亚硫酸甲乙酯和亚硫酸二乙酯等。
环状亚硫酸酯的实例可包括，但不限于，以下的一种或多种：1,2-乙二醇亚硫酸酯、1,2-丙二醇亚硫酸酯、1,3-丙二醇亚硫酸酯、1,2-丁二醇亚硫酸酯、1,3-丁二醇亚硫酸酯、1,4-丁二醇亚硫酸酯、1,2-戊二醇亚硫酸酯、1,3-戊二醇亚硫酸酯、1,4-戊二醇亚硫酸酯和1,5-戊二醇亚硫酸酯等。
在一些实施例中，添加剂包含一种或多种酸酐。酸酐的实例可包括，但不限于，环状磷酸酐、羧酸酐、二磺酸酐和羧酸磺酸酐中的一种或多种。环状磷酸酐的实例可包括，但不限于，三甲基磷酸环酐、三乙基磷酸环酐和三丙基磷酸环酐中的一种或多种。羧酸酐的实例可包括，但不限于，琥珀酸酐、戊二酸酐和马来酸酐中的一种或多种。二磺酸酐的实例可包括，但不限于，乙烷二磺酸酐和丙烷二磺酸酐中的一种或多种。羧酸磺酸酐的实例可包括，但不限于，磺基苯甲酸酐、磺基丙酸酐和磺基丁酸酐中的一种或多种。
在一些实施例中，添加剂为氟代碳酸酯与含碳碳双键的碳酸乙烯酯的组合。在一些实施例中，添加剂为氟代碳酸酯与含硫氧双键的化合物的组合。在一些实施例中，添加剂为氟代碳酸酯与具有2-4个氰基的化合物的组合。在一些实施例中，添加剂为氟代碳酸酯与环状羧酸酯的组合。在一些实施例中，添加剂为氟代碳酸酯与环状磷酸酐的组合。在一些实施例中，添加剂为氟代碳酸酯与羧酸酐的组合。在一些实施例中，添加剂为氟代碳酸酯与璜酸酐的组合。在一些实施例中，添加剂为氟代碳酸酯与羧酸璜酸酐的组合。
电解质没有特别限制，可以任意地使用作为电解质公知的物质。在锂二次电池的情况下，通常使用锂盐。电解质的实例可包括，但不限于，LiPF 6、LiBF 4、LiClO 4、LiAlF 4、LiSbF 6、LiTaF 6、LiWF 7等无机锂盐；LiWOF 5等钨酸锂类；HCO 2Li、CH 3CO 2Li、CH 2FCO 2Li、CHF 2CO 2Li、CF 3CO 2Li、CF 3CH 2CO 2Li、CF 3CF 2CO 2Li、CF 3CF 2CF 2CO 2Li、CF 3CF 2CF 2CF 2CO 2Li等羧酸锂盐类；FSO 3Li、CH 3SO 3Li、 CH 2FSO 3Li、CHF 2SO 3Li、CF 3SO 3Li、CF 3CF 2SO 3Li、CF 3CF 2CF 2SO 3Li、CF 3CF 2CF 2CF 2SO 3Li等磺酸锂盐类；LiN(FCO) 2、LiN(FCO)(FSO 2)、LiN(FSO 2) 2、LiN(FSO 2)(CF 3SO 2)、LiN(CF 3SO 2) 2、LiN(C 2F 5SO 2) 2、环状1,2-全氟乙烷双磺酰亚胺锂、环状1,3-全氟丙烷双磺酰亚胺锂、LiN(CF 3SO 2)(C 4F 9SO 2)等酰亚胺锂盐类；LiC(FSO 2) 3、LiC(CF 3SO 2) 3、LiC(C 2F 5SO 2) 3等甲基化锂盐类；双(丙二酸根合)硼酸锂盐、二氟(丙二酸根合)硼酸锂盐等(丙二酸根合)硼酸锂盐类；三(丙二酸根合)磷酸锂、二氟双(丙二酸根合)磷酸锂、四氟(丙二酸根合)磷酸锂等(丙二酸根合)磷酸锂盐类；以及LiPF 4(CF 3) 2、LiPF 4(C 2F 5) 2、LiPF 4(CF 3SO 2) 2、LiPF 4(C 2F 5SO 2) 2、LiBF 3CF 3、LiBF 3C 2F 5、LiBF 3C 3F 7、LiBF 2(CF 3)2、LiBF 2(C 2F 5) 2、LiBF 2(CF 3SO 2) 2、LiBF 2(C 2F 5SO 2) 2等含氟有机锂盐类；二氟草酸硼酸锂、双(草酸)硼酸锂等草酸硼酸锂盐类；四氟草酸根合磷酸锂、二氟双(草酸根合)磷酸锂、三(草酸根合)磷酸锂等草酸根合磷酸锂盐类等。
在一些实施例中，电解质选自LiPF 6、LiSbF 6、LiTaF 6、FSO 3Li、CF 3SO 3Li、LiN(FSO 2) 2、LiN(FSO 2)(CF 3SO 2)、LiN(CF 3SO 2) 2、LiN(C 2F 5SO 2) 2、环状1,2-全氟乙烷双磺酰亚胺锂、环状1,3-全氟丙烷双磺酰亚胺锂、LiC(FSO 2) 3、LiC(CF 3SO 2) 3、LiC(C 2F 5SO 2) 3、LiBF 3CF 3、LiBF 3C 2F 5、LiPF 3(CF 3) 3、LiPF 3(C 2F 5) 3、二氟草酸硼酸锂、双(草酸)硼酸锂或二氟双(草酸根合)磷酸锂，其有助于改善电化学装置的输出功率特性、高倍率充放电特性、高温保存特性和循环特性等。
电解质的含量没有特别限制，只要不损害本申请的效果即可。在一些实施例中，电解液中的锂的总摩尔浓度为大于0.3mol/L以上、大于0.4mol/L或大于0.5mol/L。在一些实施例中，电解液中的锂的总摩尔浓度为小于3mol/L、小于2.5mol/L或小于2.0mol/L以下。在一些实施例中，电解液中的锂的总摩尔浓度在上述任意两个数值所组成的范围内。当电解质浓度在上述范围内时，作为带电粒子的锂不会过少，并且可以使粘度处于适当的范围，因而容易确保良好的电导率。
当使用两种以上的电解质的情况下，电解质包括至少一种为选自由单氟磷酸盐、硼酸盐、草酸盐和氟磺酸盐组成的组中的盐。在一些实施例中，电解质包括选自由单氟磷酸盐、草酸盐和氟磺酸盐组成的组中的盐。在一些实施例中，电解质包括锂盐。在一些实施例中，基于电解质的总重量，选自由单氟磷酸盐、硼酸盐、草酸盐和氟磺酸盐组成的组中的盐的含量为大于0.01％或大于0.1％。在一 些实施例中，基于电解质的总重量，选自由单氟磷酸盐、硼酸盐、草酸盐和氟磺酸盐组成的组中的盐的含量为小于20％或小于10％。在一些实施例中，选自由单氟磷酸盐、硼酸盐、草酸盐和氟磺酸盐组成的组中的盐的含量在上述任意两个数值所组成的范围内。
在一些实施例中，电解质包含选自由单氟磷酸盐、硼酸盐、草酸盐和氟磺酸盐组成的组中的一种以上物质和除此以外的一种以上的盐。作为除此以外的盐，可以举出在上文中例示的锂盐，在一些实施例中为LiPF 6、LiN(FSO 2)(CF 3SO 2)、LiN(CF 3SO 2) 2、LiN(C 2F 5SO 2) 2、环状1,2-全氟乙烷双磺酰亚胺锂、环状1,3-全氟丙烷双磺酰亚胺锂、LiC(FSO 2) 3、LiC(CF 3SO 2) 3、LiC(C 2F 5SO 2) 3、LiBF 3CF 3、LiBF 3C 2F 5、LiPF 3(CF 3) 3、LiPF 3(C 2F 5) 3。在一些实施例中，除此以外的盐为LiPF 6。
在一些实施例中，基于电解质的总重量，除此以外的盐的含量为大于0.01％或大于0.1％。在一些实施例中，基于电解质的总重量，除此以外的盐的含量为小于20％、小于15％或小于10％。在一些实施例中，除此以外的盐的含量在上述任意两个数值所组成的范围内。具有上述含量的除此以外的盐有助于平衡电解液的电导率和粘度。
在电解液中，除了含有上述溶剂、添加剂和电解质盐以外，可以根据需要含有负极被膜形成剂、正极保护剂、防过充电剂等额外添加剂。作为添加剂，可使用一般在非水电解质二次电池中使用的添加剂，其实例可包括，但不限于，碳酸亚乙烯酯、琥珀酸酐、联苯、环己基苯、2，4-二氟苯甲醚、丙烷磺内酯、丙烯磺内酯等。这些添加剂可以单独使用或任意组合使用。另外，电解液中的这些添加剂的含量没有特别限制，可以根据该添加剂的种类等适当地设定即可。在一些实施例中，基于电解液的总重量，添加剂的含量为小于5％、在0.01％至5％的范围内或在0.2％至5％的范围内。
III、负极
负极极片包括负极集流体和设置在负极集流体的一个或两个表面上的负极合剂层。负极合剂层包括负极活性物质层，负极活性物质层包含负极活性物质。负极活性物质层可以是一层或多层，多层负极活性物质中的每层可以包含相同或不同的负极活性物质。负极活性物质为任何能够可逆地嵌入和脱嵌锂离子等金属 离子的物质。在一些实施例中，负极活性物质的可充电容量大于正极活性物质的放电容量，以防止在充电期间锂金属无意地析出在负极上。在一些实施例中，可根据需要在负极集流体表面上未涂覆负极合剂层的区域设置如正极一般的涂层。
作为保持负极活性物质的集流体，可以任意使用公知的集流体。负极集流体的实例包括，但不限于，铝、铜、镍、不锈钢、镀镍钢等金属材料。在一些实施例中，负极集流体为铜。
在负极集流体为金属材料的情况下，负极集流体形式可包括，但不限于，金属箔、金属圆柱、金属带卷、金属板、金属薄膜、金属板网、冲压金属、发泡金属等。在一些实施例中，负极集流体为金属薄膜。在一些实施例中，负极集流体为铜箔。在一些实施例中，负极集流体为基于压延法的压延铜箔或基于电解法的电解铜箔。
在一些实施例中，负极集流体的厚度为大于1μm或大于5μm。在一些实施例中，负极集流体的厚度为小于100μm或小于50μm。在一些实施例中，负极集流体的厚度在上述任意两个数值所组成的范围内。
负极活性物质没有特别限制，只要能够可逆地吸藏、放出锂离子即可。负极活性物质的实例可包括，但不限于，天然石墨、人造石墨等碳材料；硅(Si)、锡(Sn)等金属；或Si、Sn等金属元素的氧化物等。负极活性物质可以单独使用或组合使用。
负极合剂层还可包括负极粘合剂。负极粘合剂可提高负极活性物质颗粒彼此间的结合和负极活性物质与集流体的结合。负极粘合剂的种类没有特别限制，只要是对于电解液或电极制造时使用的溶剂稳定的材料即可。在一些实施例中，负极粘合剂包括树脂粘合剂。树脂粘合剂的实例包括，但不限于，氟树脂、聚丙烯腈(PAN)、聚酰亚胺树脂、丙烯酸系树脂、聚烯烃树脂等。当使用水系溶剂制备负极合剂浆料时，负极粘合剂包括，但不限于，羧甲基纤维素(CMC)或其盐、苯乙烯-丁二烯橡胶(SBR)、聚丙烯酸(PAA)或其盐、聚乙烯醇等。
负极极片可以通过以下方法制备：在负极集流体上涂布包含负极活性物质、树脂粘结剂等的负极合剂浆料，干燥后，进行压延而在负极集流体的两面形成负极合剂层，由此可以得到负极。
IV、隔离膜
为了防止短路，在正极与负极极片之间通常设置有隔离膜。这种情况下，本申请的电解液通常渗入该隔离膜而使用。
对隔离膜的材料及形状没有特别限制，只要不显著损害本申请的效果即可。隔离膜可为由对本申请的电解液稳定的材料所形成的树脂、玻璃纤维、无机物等。在一些实施例中，隔离膜包括保液性优异的多孔性片或无纺布状形态的物质等。树脂或玻璃纤维隔离膜的材料的实例可包括，但不限于，聚烯烃、芳香族聚酰胺、聚四氟乙烯、聚醚砜、玻璃过滤器等。在一些实施例中，隔离膜的材料为玻璃过滤器。在一些实施例中，聚烯烃为聚乙烯或聚丙烯。在一些实施例中，聚烯烃为聚丙烯。上述隔离膜的材料可以单独使用或任意组合使用。
隔离膜还可为上述材料层积而成的材料，其实例包括，但不限于，按照聚丙烯、聚乙烯、聚丙烯的顺序层积而成的三层隔离膜等。
无机物的材料的实例可包括，但不限于，氧化铝、二氧化硅等氧化物、氮化铝、氮化硅等氮化物、硫酸盐(例如，硫酸钡、硫酸钙等)。无机物的形式可包括，但不限于，颗粒状或纤维状。
隔离膜的形态可为薄膜形态，其实例包括，但不限于，无纺布、织布、微多孔性膜等。在薄膜形态中，隔离膜的孔径为0.01μm至1μm，厚度为5μm至50μm。除了上述独立的薄膜状隔离膜以外，还可以使用下述隔离膜：通过使用树脂类的粘合剂在正极和/或负极极片的表面形成含有上述无机物颗粒的复合多孔层而形成的隔离膜，例如，将氟树脂作为粘合剂使90％粒径小于1μm的氧化铝颗粒在正极的两面形成多孔层而形成的隔离膜。
隔离膜的厚度是任意的。在一些实施例中，隔离膜的厚度为大于1μm、大于5μm或大于8μm。在一些实施例中，隔离膜的厚度为小于50μm、小于40μm或小于30μm。在一些实施例中，隔离膜的厚度在上述任意两个数值所组成的范围内。当隔离膜的厚度在上述范围内时，则可以确保绝缘性和机械强度，并可以确保电化学装置的倍率特性和能量密度。
在使用多孔性片或无纺布等多孔质材料作为隔离膜时，隔离膜的孔隙率是任意的。在一些实施例中，隔离膜的孔隙率为大于20％、大于35％或大于45％。在一些实施例中，隔离膜的孔隙率为小于90％、小于85％或小于75％。在一些 实施例中，隔离膜的孔隙率在上述任意两个数值所组成的范围内。当隔离膜的孔隙率在上述范围内时，可以确保绝缘性和机械强度，并可以抑制膜电阻，使电化学装置具有良好的倍率特性。
隔离膜的平均孔径也是任意的。在一些实施例中，隔离膜的平均孔径为小于0.5μm或小于0.2μm。在一些实施例中，隔离膜的平均孔径为大于0.05μm。在一些实施例中，隔离膜的平均孔径在上述任意两个数值所组成的范围内。若隔离膜的平均孔径超过上述范围，则容易发生短路。当隔离膜的平均孔径在上述范围内时，在防止短路的同时可抑制了膜电阻，使电化学装置具有良好的倍率特性。
V、电化学装置
电化学装置包括电极组件、集电结构、壳体和保护元件。
电极组件
电极组件可以是由上述正极和负极隔着上述隔离膜层积而成的叠片结构、以及上述正极和负极隔着上述隔离膜以漩涡状卷绕而成的结构中的任一种。在一些实施例中，电极组件的质量在电池内容积中所占的比例(电极组件占有率)为大于40％或大于50％。在一些实施例中，电极组件占有率为小于90％或小于80％。在一些实施例中，电极组件占有率在上述任意两个数值所组成的范围内。当电极组件占有率在上述范围内时，可以确保电化学装置的容量，同时可以抑制与内部压力上升相伴的反复充放电性能及高温保存等特性的降低，进而可以防止气体释放阀的工作。
根据本申请的一些实施例，电极组件的外表面能够进一步设置本申请正极中的涂层。在一些实施例中，本申请的涂层能够设置于电极组件的外表面上的部分或全部区域。通过在电极组件的外表面设置涂层能够进一步提高电极组件受到外部冲击或异物穿刺时的安全性。
集电结构
集电结构没有特别限制。在一些实施例中，集电结构为降低配线部分及接合部分的电阻的结构。当电极组件为上述层积结构时，适合使用将各电极层的金属芯部分捆成束而焊接至端子上所形成的结构。电极面积增大时，内部电阻增大，因而在电极内设置2个以上的端子而降低电阻也是适合使用的。当电极组件为上 述卷绕结构时，通过在正极和负极极片分别设置2个以上的引线结构，并在端子上捆成束，从而可以降低内部电阻。
壳体
壳体的材质没有特别限制，只要是对于所使用的电解液稳定的物质即可。壳体可使用，但不限于，镀镍钢板、不锈钢、铝或铝合金、镁合金等金属类、或者树脂与铝箔的层积膜。在一些实施例中，壳体为铝或铝合金的金属或层积膜。
金属类的壳体包括，但不限于，通过激光焊接、电阻焊接、超声波焊接将金属彼此熔敷而形成的封装密闭结构；或者隔着树脂制垫片使用上述金属类形成的铆接结构。使用上述层积膜的壳体包括，但不限于，通过将树脂层彼此热粘而形成的封装密闭结构等。为了提高密封性，还可以在上述树脂层之间夹入与层积膜中所用的树脂不同的树脂。在通过集电端子将树脂层热粘而形成密闭结构时，由于金属与树脂的接合，可使用具有极性基团的树脂或导入了极性基团的改性树脂作为夹入的树脂。另外，壳体的形状也是任意的，例如可以为圆筒形、方形、层积型、纽扣型、大型等中的任一种。
根据本申请的一些实施例，于电极组件的外表面上设置的上述涂层的表面进一步设置粘结层，当电极组件设置于壳体内形成电化学装置后，粘结层能够对壳体的部分区域粘结，并提高电化学装置的结构稳定性。在一些实施例中，涂层和正极集流体之间的粘结力大于或等于涂层和粘结层之间的粘结力。通过设计涂层对正极集流体与粘结层的粘结力的差异，能够保证电化学装置在受到金属刺穿物穿刺时，涂层能够随着正极集流体一同延伸，进而将正极集流体与金属刺穿物隔开，并提升电化学装置受到外物穿刺或冲击时的安全性能。
保护元件
保护元件可以使用在异常放热或过大电流流过时电阻增大的正温度系数(PTC)、温度熔断器、热敏电阻、在异常放热时通过使电池内部压力或内部温度急剧上升而切断在电路中流过的电流的阀(电流切断阀)等。上述保护元件可选择在高电流的常规使用中不工作的条件的元件，亦可设计成即使不存在保护元件也不至于发生异常放热或热失控的形式。
VI、应用
本申请的电化学装置包括发生电化学反应的任何装置，它的具体实例包括所有种类的一次电池、二次电池、燃料电池、太阳能电池或电容。特别地，该电化学装置是锂二次电池，包括锂金属二次电池、锂离子二次电池、锂聚合物二次电池或锂离子聚合物二次电池。
本申请另提供了一种电子装置，其包括根据本申请的电化学装置。
本申请的电化学装置的用途没有特别限定，其可用于现有技术中已知的任何电子装置。在一些实施例中，本申请的电化学装置可用于，但不限于，笔记本电脑、笔输入型计算机、移动电脑、电子书播放器、便携式电话、便携式传真机、便携式复印机、便携式打印机、头戴式立体声耳机、录像机、液晶电视、手提式清洁器、便携CD机、迷你光盘、收发机、电子记事本、计算器、存储卡、便携式录音机、收音机、备用电源、电机、汽车、摩托车、助力自行车、自行车、照明器具、玩具、游戏机、钟表、电动工具、闪光灯、照相机、家庭用大型蓄电池和锂离子电容器等。
下面以锂离子电池为例并且结合具体的实施例说明锂离子电池的制备及其安全性能，本领域的技术人员将理解，本申请中描述的制备方法仅是实例，其他任何合适的制备方法均在本申请的范围内。
实施例
以下说明列举了本申请的锂离子电池的实施例和对比例及其所进行的性能评估。
一、锂离子电池的制备
1、正极的制备
采用选定厚度的铝箔作为正极集流体，将绝缘材料、粘结剂按照选定的重量比进行混合，加入去离子水，在真空搅拌机作用下搅拌至体系成均一浆料，获得涂层浆料，其中固含量为40wt％；根据极片尺寸要求，在正极集流体表面部分区域涂覆一层涂层浆料，在85℃下干燥，得到涂有涂层的正极集流体。
将正极活性物质钴酸锂(LiCoO2)、导电剂SP、粘结剂聚偏二氟乙烯按照重量比97：1.4：1.6进行混合，加入N-甲基吡咯烷酮(NMP)，在真空搅拌机作 用下搅拌至均一浆料，获得常规正极浆料，其中正极浆料的固含量为72wt％；根据极片尺寸要求，在正极集流体表面未涂覆涂层的区域涂覆一层正极浆料，将膜片在85℃下烘干，经过冷压、裁片、分切后，在85℃的真空条件下干燥4h，得到正极。
根据以下实施例和对比例的条件设置涂层，使其具有相应参数。
2、负极的制备
将人造石墨、丁苯橡胶和羧甲基纤维素钠按照96％:2％:2％的质量比例与去离子水混合，搅拌均匀，得到负极浆料。将该负极浆料涂布在12μm的铜箔上。干燥，冷压，再经过裁片、焊接极耳，得到负极。
3、电解液的制备
在干燥氩气环境下，将EC、PC、PP和DEC(重量比1：1：1：1)混合，加入LiPF 6混合均匀，形成基础电解液，其中LiPF 6的浓度为1.15mol/L。
4、隔离膜的制备
以聚乙烯(PE)多孔聚合物薄膜作为隔离膜。
5、锂离子电池的制备
将得到的正极、隔离膜和负极按次序卷绕，置于外装壳体(外包装箔)中，留下注液口。从注液口灌注电解液，封装，再经过化成、容量等工序制得锂离子电池。
二、测试方法
1、涂层粘结力的测试方法
(1)、取样：将化成后电极组件拆解，拆出正极，用无尘纸将极片表层电解液擦释干净；
(2)、制样：取待测试极片，用刀片截取宽(约20mm)及长y(约190mm)的试样，尺寸可依据实际拆出极片尺寸选择；
(3)、将双面胶(NITTO 5000NS)贴于宽度30mm*长度200-300mm钢板上，双面胶宽度20mm*长度y；
(4)、将第2步截取的极片试样贴在双面胶上，测试面朝下；
(5)、将宽度与极片等宽，长度大于试样长度80-200mm的纸带用皱纹胶固定；
(6)、将纸带向上翻折，用上夹具固定，用高铁AI-3000拉力机测试其粘结 力，拉伸速度：50mm/min拉伸位移根据样品长度确定；
(7)、取曲线走平时拉力值f计算粘结力，F＝f*g(9.8N/kg)/x(极片宽度)单位：N/m。
2、穿钉测试的测试方法
取10枚待测的电化学装置(锂离子电池)在常温下以0.5C倍率恒定电流充电至电压4.4V，进一步在4.4V恒定电压下充电至电流0.05C，使其处于4.4V满充状态。之后在常温条件下对锂离子电池进行钉子穿刺，采用直径为2.5mm钉子(钢钉，材质为碳钢，锥度为16.5mm，钢钉总长为100mm)，以30mm/s的速度穿刺，穿刺深度以钉子锥度穿过锂离子电池为准，钉子穿刺后保留300s，观察锂离子电池是否产烟、起火或爆炸。若没有则认为锂离子电池通过穿钉测试。计算10枚待测的电化学装置的穿刺通过率。
三、测试结果
表1展示了实施例1-18和对比例1-3的具体组成以及相应的涂层粘结力和穿刺通过率。其中，涂层位置为极片端部部分，涂层距离端部边缘的寛度为150mm。
表1
Figure PCTCN2020130421-appb-000001
Figure PCTCN2020130421-appb-000002
结果表明，通过实施例与对比例1比较可知，不含涂层的对比例1穿刺通过率为0/10，不具备穿钉测试的安全性，而对比例2及对比例3虽然涂覆了涂层，但其粘结力不满足本申请实施例的要求，其电化学装置的穿刺通过率仅分别为0/10及3/10，不足50％，安全性同样无法满足要求。当使用本申请中的涂层，涂层粘结力达到5N/m的实施例1，其穿刺通过率达到5/10，满足了50％通过率的安全性要求。进一步提高涂层粘结力，其穿刺通过率进一步大幅提升，当达到10N/m后，即可实现穿钉100％通过率。这是因为，当刺穿处的集流体随着金属穿刺物(钢钉)向穿刺方向延伸时，高粘结力的涂层能够紧密跟随破裂集流体的延伸，并能够阻隔在集流体与金属穿刺物之间，避免了集流体的裸露所导致的与金属穿刺物导通的短路，同时也能够遮蔽穿刺产生的毛刺，大幅降低了短路风险。
表2展示了不同平均粒径的绝缘材料与涂层厚度h的要求关系。
表2
Figure PCTCN2020130421-appb-000003
结果表明，涂层厚度h与绝缘材料平均粒径T满足以下条件：h≥1.5×T的实施例19-26相比于对比例4-6具有显著提高的穿刺通过率。这是由于，当绝缘材料的平均粒径相较涂层厚度越小时，能够提高绝缘材料在涂层中的分散性，导致绝缘材料能够均匀分散，从而提高涂层的隔离作用；另一方面，当绝缘材料的平 均粒径越接近涂层厚度时，该绝缘材料的颗粒区域周围的粘结剂含量也偏少，会降低绝缘材料的颗粒区域周围的粘结力，从而无法很好的随被刺穿的集流体延展，导致遮蔽毛刺作用大幅降低。另外，当涂层厚度大于或等于绝缘材料的平均粒径的1.5倍时，能够提高涂层浆料在集流体表面上的覆盖度，进而提高涂层覆盖度。
表3展示了涂层的厚度h(μm)与集流体的延展率x、强度p(Mpa)、及厚度H(μm)的关系对穿刺通过率的影响。
表3
Figure PCTCN2020130421-appb-000004
结果表明，涂层与正极集流体的关系满足以下条件：h≥(H×p×x)/k的实施例27-33相比于对比例7具有更加优异的穿刺通过率，其原因在于，集流体厚度、延展率越大，相应在刺穿时的变形也就越大，因而需要更厚的绝缘涂层以满足延展阻隔的需要。因此，根据上述关系选择合适的绝缘层厚度，可满足安全改善效果。
表4展示了将实施例5的涂层浆料设置于正极的侧边部分与极耳处对穿刺通过率的影响
表4
  绝缘层覆盖位置 穿钉位置 穿刺通过率
对比例8 极片侧边部分无覆盖 电极组件侧边部分 0/10
对比例9 极耳处无覆盖 极耳处 0/10
实施例34 极片侧边部分完全覆盖 电极组件侧边部分 10/10
实施例35 极耳处完全覆盖 极耳处 10/10
结果表明，在正极的侧边部分和极耳处设置本申请的涂层，可大幅提高对其电化学装置相对应的部位的穿钉测试的穿刺通过率，保证电极组件的安全性能。
表5展示了涂层中的粘结剂的分子量对穿刺通过率的影响
表5
Figure PCTCN2020130421-appb-000005
结果表明，粘结剂的分子量会影响涂层对集流体的粘结力。在本申请实施例范围中的粘结剂的分子量，能够保持涂层对集流体的粘结力，以确保电极组件的安全性能。
表6展示了涂层对集流体与粘结层的粘结力差异对穿刺通过率的影响
表6
Figure PCTCN2020130421-appb-000006
结果表明，通过限定涂层对集流体的粘结力大于或等于涂层对粘结层的粘结力，可进一步提高其电化学装置穿钉测试的穿刺通过率。
通过上述实施例及对比例可知，本申请的正极通过采用在正极集流体表面上的无正极活性物质层覆盖区域涂覆具有高粘结力的涂层，其锂离子电池的穿钉测试通过率会有巨大程度的改善，显著提高锂离子电池的安全性能。
整个说明书中对“实施例”、“部分实施例”、“一个实施例”、“另一举例”、“举例”、“具体举例”或“部分举例”的引用，其所代表的意思是在本申请中的至少一个实施例或举例包含了该实施例或举例中所描述的特定特征、结构、材料或特性。因此，在整个说明书中的各处所出现的描述，例如：“在一些实施例中”、“在实施例中”、“在一个实施例中”、“在另一个举例中”，“在一个举例中”、“在特定举例中”或“举例”，其不必然是引用本申请中的相同的实施例或示例。此外，本文中的特定特征、结构、材料或特性可以以任何合适的方式在一个或多个实施例或举例中结合。
尽管已经演示和描述了说明性实施例，本领域技术人员应该理解上述实施例不能被解释为对本申请的限制，并且可以在不脱离本申请的精神、原理及范围的情况下对实施例进行改变，替代和修改。

Claims (15)

  1. 一种正极，其特征在于，包括正极集流体、正极活性物质层及涂层，其中所述正极活性物质层及所述涂层设置于所述正极集流体的表面上，所述涂层和所述正极集流体之间的粘结力大于或等于5N/m。
  2. 根据权利要求1所述的正极，其特征在于，所述涂层位于如下位置中的至少一处：1)所述正极集流体长度方向的端部；2)所述正极集流体宽度方向的边缘；3)所述正极活性物质层沿所述正极集流体长度方向的间隔处。
  3. 根据权利要求1所述的正极，其特征在于，所述涂层包括粘结剂；可选地，所述涂层进一步包括绝缘材料。
  4. 根据权利要求3所述的正极，其特征在于，所述涂层与所述绝缘材料的关系满足以下条件：h≥1.5×T，
    其中，h为所述涂层的厚度，T为所述绝缘材料的平均粒径。
  5. 根据权利要求4所述的正极，其特征在于，所述绝缘材料的平均粒径T为0.1μm至20μm；且所述涂层的厚度h大于或等于0.5μm。
  6. 根据权利要求1所述的正极，其特征在于，所述涂层与所述正极集流体的关系满足以下条件：h≥(H×p×x)/k，
    其中，h为所述涂层的厚度，x为所述正极集流体的延展率，p为所述正极集流体的强度，H为所述正极集流体的厚度，且k＝100MPa。
  7. 根据权利要求6所述的正极，其特征在于，所述正极集流体的延展率x的范围为1.5％至3.5％；所述正极集流体的强度p的范围为100Mpa至300Mpa；所述正极集流体的厚度H的范围为5μm至20μm。
  8. 根据权利要求3所述的正极，其特征在于，满足以下条件的至少一者：
    a.所述粘结剂包括聚偏氟乙烯、聚四氟乙烯、羧甲基纤维素钠、丁苯橡胶、丁腈橡胶、聚胺酯、氟化橡胶、聚乙烯醇、聚丙烯酸钠中的至少一种；
    b.所述绝缘材料包括无机绝缘材料或有机绝缘材料中的至少一种，其中所述无机绝缘材料包含Ba、Ca、Al、Si、Ti、Mg、Fe、B中至少一种元素，所述有机绝缘材料包括以下组分的均聚物或共聚物中的至少一种：乙烯、氯乙烯、丙烯、苯乙烯、丁二烯、偏氟乙烯、四氟乙烯及六氟丙烯；
    c.基于所述涂层的重量，所述粘结剂的质量百分比为2％至100％，所述绝缘 材料的质量百分比为0％至98％。
  9. 根据权利要求8所述的正极，其特征在于，所述无机绝缘材料包括BaSO 4、CaSiO 3、CaSiO 4、γ-AlOOH、Al 2O 3、TiO 2、SiO 2、SiC、SiN、MgO、Fe 2O 3、BN中的至少一种。
  10. 根据权利要求2所述的正极，其特征在于，所述正极集流体与所述涂层相对的表面至少部分地设置有正极活性物质层。
  11. 一种电极组件，其包括根据权利要求1-10中任一权利要求所述的正极。
  12. 根据权利要求11所述的电极组件，其特征在于，满足以下条件的至少一者：
    d.所述电极组件的外表面存在所述涂层。
    e.所述正极沿所述正极集流体宽度方向的边缘存在所述涂层；
    f.所述正极包括正极极耳，所述正极极耳表面存在所述涂层。
  13. 一种电化学装置，其包括根据权利要求11-12中任一权利要求所述的电极组件。
  14. 根据权利要求13所述的电化学装置，其特征在于，所述电极组件位于壳体内，所述涂层与所述壳体之间存在粘结层，所述涂层和所述正极集流体之间的粘结力大于或等于所述涂层和所述粘结层之间的粘结力。
  15. 一种电子装置，其包括根据权利要求13或14所述的电化学装置。
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