CN112542569A - Electrode assembly, electrochemical device comprising same and electronic device - Google Patents

Electrode assembly, electrochemical device comprising same and electronic device Download PDF

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Publication number
CN112542569A
CN112542569A CN202011411667.2A CN202011411667A CN112542569A CN 112542569 A CN112542569 A CN 112542569A CN 202011411667 A CN202011411667 A CN 202011411667A CN 112542569 A CN112542569 A CN 112542569A
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layer
electrode assembly
active layer
positive electrode
lithium
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CN112542569B (en
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韩冬冬
李巍巍
王可飞
刘胜奇
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Ningde Amperex Technology Ltd
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Ningde Amperex Technology Ltd
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Priority to PCT/CN2021/134394 priority patent/WO2022116964A1/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
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/058—Construction or manufacture
    • 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
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

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  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
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  • Manufacturing & Machinery (AREA)
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  • Secondary Cells (AREA)
  • Battery Electrode And Active Subsutance (AREA)

Abstract

The application provides an electrode subassembly, including the negative pole mass flow body, set up in the negative pole active layer, diaphragm layer, the positive pole active layer on at least one surface of the negative pole mass flow body, just the diaphragm layer set up in the negative pole active layer with between the positive pole active layer, just at least partial surface edge perpendicular to of positive pole active layer there is not anodal metal mass flow body in the projection area of partial surface direction. In the electrode assembly of the present application, a metal current collector (e.g., aluminum) is not required, and the thickness of the entire electrode assembly can be reduced, thereby achieving higher energy density. In addition, because the positive electrode does not have a metal current collector, short circuit caused by that metal burrs pierce the diaphragm when the positive electrode is pierced can be avoided. Therefore, the secondary battery (for example, lithium ion battery) using the present application has higher safety.

Description

Electrode assembly, electrochemical device comprising same and electronic device
Technical Field
The application relates to the field of energy storage, in particular to an electrode assembly for improving the safety of a battery cell and improving the energy density, and an electrochemical device and an electronic device comprising the electrode assembly.
Background
As technology develops and the demand for mobile devices increases, the demand for electrochemical devices (e.g., lithium ion batteries) has increased significantly. Meanwhile, a lithium ion battery with high safety and high energy density is one of research directions.
In practical use, the electrochemical device may be impacted by a foreign object, and in an extreme case, the electrochemical device may be pierced by a sharp object, when the electrochemical device is pierced, on one hand, if the pierced object is a metal body, the pierced part of the current collector is conducted to another electrode through the metal body; on the other hand, the piercing part of the current collector usually generates burrs and extends along with the downward deformation of the pierced object, so that the pierced diaphragm directly communicates the positive electrode and the negative electrode, a short circuit is caused, a large amount of heat is generated to cause the battery to be on fire or even explode, and the use safety of consumers is seriously threatened. At the same time, consumers have made higher demands on the capacity and the endurance of the electrochemical device.
In view of the foregoing, there is a need for an electrode assembly, an electrochemical device and an electronic device including the same, which can improve cell safety and increase energy density.
Disclosure of Invention
Embodiments of the present application address at least one of the problems occurring in the related art to at least some extent by providing an electrode assembly and an electrochemical device including the same, which improve cell safety and increase energy density.
In one aspect of the present application, the present application provides an electrode assembly, which includes a negative electrode current collector, a negative electrode active layer disposed on at least one surface of the negative electrode current collector, a separator layer, a positive electrode active layer, the separator layer disposed between the negative electrode active layer and the positive electrode active layer, and at least a part of the surface of the positive electrode active layer is perpendicular to the projection area of the part of the surface direction, and there is no positive electrode metal current collector.
According to some embodiments of the present application, the partial surface accounts for 50% or more, preferably 80% or more, more preferably 95% or more of the surface of the positive electrode active layer.
In the electrode assembly, the positive electrode only comprises the positive active layer, and a metal current collector is not needed, so that the whole thickness of the electrode assembly can be reduced, and the energy density of the electrode can be improved. The application the metal mass flow body, including the mass flow body that aluminium foil, copper foil, stainless steel foil etc. made by metal material.
According to some embodiments of the present application, the adhesion of the positive electrode active layer to the separator layer is greater than or equal to 2N/m.
According to some embodiments of the present application, the positive electrode active layer includes a positive electrode active material, wherein the positive electrode active material is selected from at least one of a lithium transition metal composite oxide and a lithium transition metal phosphate compound.
According to some embodiments of the present application, the negative active layer includes a negative active material and a binder, wherein the negative active material is selected from at least one of graphite and a silicon-based material.
According to some embodiments of the present application, the silicon-based material is selected from at least one of pure silicon, SiOx (0< x <2), silicon carbon composite.
In the electrode assembly of the present application, the negative electrode active layer may be coated on one surface of the negative electrode current collector, and may also be coated on both opposite surfaces of the negative electrode current collector. Accordingly, a separator layer, a positive active material layer, and a conductive layer may be coated on both sides of the negative electrode current collector to form an electrode assembly that is symmetrical with respect to the negative electrode current collector. Of course, the separator layer, the positive electrode active material layer, and the conductive layer may be coated on only one side.
According to some embodiments of the present application, a surface of the positive electrode active layer is provided with a conductive layer.
According to some embodiments of the present application, the conductive layer has a thickness of 0.1 μm to 30 μm. The thickness of the electrode assembly has a close relationship with the energy density, and the conductive layer should not be too thin, nor too thick. The conductive layer with too small thickness can not only increase the process difficulty, but also cause uneven thickness of the conductive layer, resulting in poor conductive performance. An excessive thickness of the conductive layer causes an excessive thickness of the entire electrode assembly, resulting in a decrease in energy density of the electrode assembly. In the present application, the thickness of the conductive layer is 0.1 μm to 30 μm.
The conductive layer in the electrode assembly includes a conductive agent, wherein the conductive agent includes at least one of carbon black, acetylene black, fullerene, carbon nanotube, graphene, graphite. According to some embodiments of the present application, a surface of the conductive layer is provided with an insulating layer.
According to some embodiments of the present application, the insulating layer comprises a binder, wherein the binder is present in an amount a by mass, wherein a is 2% to 100%, based on the weight of the insulating layer. The addition of the binder to the insulating layer can enhance the adhesion between the insulating materials, so that the insulating layer is firmly adhered to the surface of the conductive layer. In the present application, the binder may be selected from at least one of polyvinylidene fluoride (PVDF), Polytetrafluoroethylene (PTFE), sodium carboxymethylcellulose (CMC), Styrene Butadiene Rubber (SBR), nitrile butadiene rubber, polyurethane, fluorinated rubber, polyvinyl alcohol (PVA), or sodium polyacrylate.
According to some embodiments of the present application, the composition of the insulating layer further comprises an insulating material, and the thickness h of the insulating layer is greater than or equal to 0.5 μm.
The insulating material in the insulating layer may be an inorganic insulating material, or may be at least one of organic insulating materials, or a mixed material of an inorganic insulating material and an organic insulating material. As an example, the inorganic insulating material may be selected from BaSO4、CaSiO3、γ-AlOOH、CaSiO4、Al2O3、TiO2The organic insulating material may be at least one selected from homopolymers or copolymers of ethylene, vinyl chloride, propylene, styrene, butadiene, vinylidene fluoride, tetrafluoroethylene, and hexafluoropropylene.
According to some embodiments of the application, the insulating material has an average particle size of 0.01 μm to 20 μm.
According to some embodiments of the present application, the separator layer comprises at least one of an inorganic layer, a polyolefin porous layer.
According to some embodiments of the present application, the set of inorganic layersComprises inorganic particles and a binder, wherein the inorganic particles comprise BaSO4、CaSiO3、γ-AlOOH、CaSiO4、Al2O3、TiO2、SiO2At least one of (1). In order to ensure the cohesiveness of the inorganic particles, the binder is present in an amount of b, wherein b is 5% or more and 40% or less, based on the weight of the inorganic layer.
According to some embodiments of the present application, the negative current collector is selected from copper foil. The copper foil has excellent stability and can avoid corrosion during discharge.
According to some embodiments of the present application, the electrode assembly further comprises a tab. The tab is a positive electrode tab, and the positive electrode tab is in contact with the positive electrode active layer, so that the positive electrode tab is electrically connected with the positive electrode active layer. In another embodiment, the positive tab is in contact with the conductive layer, thereby achieving electrical connection of the tab to the conductive layer.
The application also provides a preparation method of the electrode assembly, which comprises the following steps: 1) sequentially arranging the negative electrode active layer and the diaphragm layer on the surface of the negative electrode current collector; 2) and coating the positive electrode active layer on the surface of the separator layer.
According to some embodiments of the present application, further comprising the step of: 3) and arranging the conductive layer or the insulating layer on the surface of the positive electrode active layer.
According to some embodiments of the present application, further comprising the step of: 4) and arranging the insulating layer on the surface of the conductive layer.
The present application also provides an electrochemical device comprising the electrode assembly according to the present invention.
The present application also provides an electronic device comprising the electrochemical device described herein.
The beneficial effect of this application:
in the electrode assembly of the present application, the positive electrode includes the positive electrode active layer and the conductive layer, and a metal current collector (e.g., aluminum) is not required, so that the thickness of the entire electrode assembly can be reduced, thereby achieving higher energy density. In addition, because the positive electrode does not have a metal current collector, short circuit caused by that metal burrs pierce the diaphragm when the positive electrode is pierced can be avoided. Therefore, the secondary battery (for example, lithium ion battery) using the present application has higher safety.
Drawings
FIG. 1 is a schematic view of one embodiment of an electrode assembly of the present application;
FIG. 2 is a schematic view of another embodiment of an electrode assembly of the present application;
fig. 3 is a schematic view of yet another embodiment of an electrode assembly of the present application.
Reference numerals:
1-positive electrode
11-positive electrode active layer
12-Positive electrode conductive layer
2-negative electrode
21-negative active layer
3-diaphragm layer
4-negative current collector
5-positive pole tab
6-insulating layer
Detailed Description
Embodiments of the present application will be described in detail below. The embodiments of the present application should not be construed as limiting the present application.
The following terms used herein have the meanings indicated below, unless explicitly indicated otherwise.
In the detailed description and claims, a list of items linked by the term "at least one of," "at least one of," or other similar terms may mean any combination of the listed items. For example, if items a and B are listed, the phrase "at least one of a and B" means a only; only B; or A and B. In another example, if items A, B and C are listed, the phrase "at least one of A, B and C" means a only; or only B; only C; a and B (excluding C); a and C (excluding B); b and C (excluding A); or A, B and C. Item a may comprise a single element or multiple elements. Item B may comprise a single element or multiple elements. Item C may comprise a single element or multiple elements.
An electrode (positive electrode or negative electrode) of an electrochemical device (e.g., a lithium ion battery) is generally prepared by the following method: mixing an active material, a conductive agent, a thickening agent, a binder and a solvent, and then coating the mixed slurry on a current collector. However, when 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 conducted to the other electrode through the metal body; on the other hand, the pierced part of the current collector usually generates burrs and extends along with downward deformation of the pierced object, so that the pierced diaphragm directly communicates the positive electrode and the negative electrode, and short circuit is caused.
This application has cancelled traditional anodal mass flow body Al foil through the electrode subassembly structure that uses specific structure, has avoided electrochemical device at the drift nail in-process, and the metal mass flow body Al foil of high ductility extends and with the contact of another electrode along with the puncture thing, simultaneously, has also avoided the production of metal burr to pierce through the barrier film and cause the short circuit, improved electrochemical device's security. Meanwhile, the energy density is greatly improved by eliminating inactive metal current collectors in the electrochemical device.
In one embodiment, the present application provides an electrochemical device including an electrode assembly of a negative electrode, a positive electrode, and a separator layer as described below, and an electrolyte.
I. Negative electrode
The negative electrode includes a negative electrode current collector and a negative electrode active layer disposed on one or both surfaces of the negative electrode current collector.
The negative electrode active layer may be one or more layers, and each of the plurality of negative electrode active layers may contain the same or different negative electrode active materials. The negative electrode active material is any material capable of reversibly intercalating and deintercalating metal ions such as lithium ions. In some embodiments, the chargeable capacity of the negative active layer is greater than the discharge capacity of the positive active layer to prevent unintentional precipitation of lithium metal on the negative electrode during charging.
As the current collector for holding the negative electrode active material, a known current collector may be used arbitrarily. Examples of the negative electrode current collector include, but are not limited to, metal materials such as aluminum, copper, nickel, stainless steel, nickel-plated steel, and the like. In some embodiments, the negative current collector is copper.
In the case where the negative electrode current collector is a metal material, the form of the negative electrode current collector may include, but is not limited to, a metal foil, a metal cylinder, a metal coil, a metal plate, a metal film, a metal lath, a stamped metal, a foamed metal, and the like. In some embodiments, the negative electrode current collector is a metal thin film. In some embodiments, the negative current collector is a copper foil. In some embodiments, the negative electrode current collector is a rolled copper foil based on a rolling process or an electrolytic copper foil based on an electrolytic process.
In some embodiments, the thickness of the negative electrode current collector is greater than 1 μm or greater than 5 μm. In some embodiments, the thickness of the negative electrode current collector is less than 100 μm or less than 50 μm. In some embodiments, the thickness of the negative electrode current collector is within a range consisting of any two of the above values.
The negative electrode active material is not particularly limited as long as it can reversibly store and release lithium ions. Examples of the negative electrode active material may include, but are not limited to, carbon materials such as natural graphite, artificial graphite, and the like; silicon-based materials such as pure silicon (Si), silicon monoxide, silicon carbon composite, and alloys of silicon and metal elements. The negative electrode active materials may be used alone or in combination.
The negative active layer may further include a negative binder. The negative electrode binder may improve the binding of the negative electrode active material particles to each other and the binding of the negative electrode active material to the current collector. The kind 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. In some embodiments, the negative electrode binder comprises a resin binder. Examples of the resin binder include, but are not limited to, fluororesins, Polyacrylonitrile (PAN), polyimide resins, acrylic resins, polyolefin resins, and the like. When the negative electrode mix slurry is prepared using an aqueous solvent, the negative electrode binder includes, but is not limited to, carboxymethyl cellulose (CMC) or a salt thereof, styrene-butadiene rubber (SBR), polyacrylic acid (PAA) or a salt thereof, polyvinyl alcohol, and the like.
The negative electrode can be prepared by the following method: a negative electrode mixture slurry containing a negative electrode active material, a resin binder, and the like is applied onto a negative electrode current collector, dried, and then rolled to form negative electrode active layers on both surfaces of the negative electrode current collector, thereby obtaining a negative electrode.
II. Positive electrode
The positive electrode may include a positive electrode active layer, and a conductive layer may be further provided on a surface of the positive electrode active layer. According to some embodiments of the present application, an insulating layer may be further provided on a surface of the conductive layer.
1. Positive electrode active layer
The positive electrode active layer contains a positive electrode active material. The positive electrode active layer may be one or more layers, and each of the plurality of positive electrode active layers may contain the same or different positive electrode active materials. The positive electrode active material is any material capable of reversibly intercalating and deintercalating metal ions such as lithium ions. In some embodiments, the discharge capacity of the positive electrode active layer is less than the chargeable capacity of the negative electrode active layer to prevent unintentional precipitation of lithium metal on the negative electrode during charging.
(1) Positive electrode active material
The kind of the positive electrode active material is not particularly limited as long as it can electrochemically occlude and release metal ions (for example, lithium ions). In some embodiments, the positive active material is a material containing lithium and at least one transition metal. Examples of the positive active material may include, but are not limited to, lithium transition metal composite oxides and lithium transition metal phosphate compounds.
In some embodiments, the transition metal in the lithium transition metal composite oxide includes V, Ti, Cr, Mn, Fe, Co, Ni, Cu, and the like. In some embodiments, the lithium transition metal composite oxide comprises LiCoO2Lithium cobalt composite oxide; LiNiO2Lithium nickel composite oxide; LiMnO2、LiMn2O4、Li2MnO4Lithium manganese composite oxides, etc.; LiNi1/3Mn1/3Co1/3O2、LiNi0.5Mn0.3Co0.2O2Isolithium nickel manganese cobalt composite oxides in which a part of transition metal atoms is a main component of these lithium transition metal composite oxidesIs 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. Examples of the lithium transition metal composite oxide may include, but are not limited to, LiNi0.5Mn0.5O2、LiNi0.85Co0.10Al0.05O2、LiNi0.33Co0.33Mn0.33O2、LiNi0.45Co0.10Al0.45O2、LiMn1.8Al0.2O4And LiMn1.5Ni0.5O4And the like. Examples of the combination of lithium transition metal composite oxides include, but are not limited to, LiCoO2With LiMn2O4In which LiMn is2O4A part of Mn in (A) may be substituted with a transition metal (e.g., LiNi)0.33Co0.33Mn0.33O2)，LiCoO2A part of Co in (a) may be substituted with a transition metal.
In some embodiments, the transition metal in the lithium-containing transition metal phosphate compound includes V, Ti, Cr, Mn, Fe, Co, Ni, Cu, and the like. In some embodiments, the lithium-containing transition metal phosphate compound comprises LiFePO4、Li3Fe2(PO4)3、LiFeP2O7Iso-phosphates, LiCoPO4And cobalt phosphates in which a part of the transition metal atoms as the main component of the lithium transition metal phosphate compound is replaced with another element such as Al, Ti, V, Cr, Mn, Fe, Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, Nb, or Si.
In some embodiments, lithium transition metal oxide Li is usedaMbO2Wherein 0.9. ltoreq. a.ltoreq.1.1, 0.9. ltoreq. b.ltoreq.1.1 and M is mainly a transition metal selected from Mn, Co and Ni, wherein the composition M varies with the particle size.
In some embodiments, Li is the lithium transition metal oxideaMbO2Wherein M ═ a in the powdery electrode active material of (a)ZA’Z’M’1-Z-Z’，M’＝MnxNiyCo1-x-yY is more than or equal to 0 and less than or equal to 1, x is more than or equal to 0 and less than or equal to 1, Z + Z ' is more than or equal to 0.1, Z ' is more than or equal to 0.02, A is selected from at least one of elements Al, Mg, Ti and Cr, and A ' is selected from at least one of elements F, Cl, S, Zr, Ba, Y, Ca, B, Be, Sn, Sb, Na and Zn.
In some embodiments, the transition metal average composition is M ═ MnxNiyCo1-x-yWherein x is more than or equal to 0.03 and less than or equal to 0.35.
In some embodiments, the transition metal average composition is M ═ MnxNiyCo1-x-yWherein x is more than or equal to 0.03 and x + y is less than or equal to 0.7.
In some embodiments, Li having composition and size dependenceaMbO2In the powdery electrode active material of (a), substantially all parts of all particles have a layered crystal structure, and the larger particles have a composition of LiaMbO2Wherein M ═ MnxNiyCo1-x-yX + y is less than or equal to 0.35, the small particles have a composition LiaMbO2Wherein M ═ Mnx’Niy’Co1-x’-y’Having at least 10% less Co, (1-x ' -y ') ≦ 0.9 x (1-x-y), and at least 5% more Mn, x ' -x>0.05. Thus, it is possible to obtain powders having a composition dependent on the size, i.e. one component having large particles (e.g. with a distribution concentrated at ≧ 20 μm); its components can diffuse in the bulk rapidly. The other component has small particles (e.g., distributed around 5 μm) and its composition ensures safety. Thereby providing an electrode active material combining high cycle stability and high safety with high volumetric energy density and high gravimetric energy density.
In some embodiments, the cathode active material has a broad particle size distribution defined as a particle size ratio of large particles to small particles of more than 3, Dv90/Dv10>3, wherein Dv90 represents a particle size reaching 90% of volume accumulation from a small particle size side in a particle size distribution on a volume basis. Dv10 represents a particle size which reaches 10% of the volume accumulation from the small particle size side in the volume-based particle size distribution. The particle size distribution of the powder can be determined by suitable methods known in the art. Suitable methods are for example laser diffraction or sieving by using screens with different mesh numbers.
In some embodiments, the individual particles are substantially lithium transition metal oxide, and the individual particles have Co, the content of which in the transition metal increases continuously with particle size.
In some embodiments, the individual particles also contain Mn in the transition metal, and the Mn content decreases continuously with particle size.
In some embodiments, the large particles have close to LiCoO to achieve high Li diffusion constants2Large particles of composition and thus sufficient rate performance can be obtained. The large particles account for only a small fraction of the total surface area of the positive electrode. Therefore, the heat evolved by the reaction with the electrolyte at the surface or at the outer part is limited; as a result, the larger particles are less likely to result in poor safety. The small particles have a composition with less Co to obtain improved safety. Lower lithium diffusion constants may be acceptable in small particles without significant loss of rate performance due to the short length of the solid state diffusion path.
In some embodiments, the preferred composition of the small particles contains a lesser amount of Co and a greater amount of a stabilizing element, such as Mn. Slower Li body diffusion is acceptable, but the surface stability is high. In the cathode active material powder of the present invention, the preferred composition of the large particles contains a larger amount of Co and a smaller amount of Mn, since rapid lithium bulk diffusion is required and a somewhat lower stability of the surface is acceptable.
In some embodiments, in the composition of LixMO2Preferably at least 80 w% of M in the interior of the individual particles of (a) is cobalt or nickel. In some embodiments, the inner portion of the particle has a proximity to LiCoO2The composition of (1). The outer part is lithium manganese nickel cobalt oxide.
The preparation of the electrode active material having a powdery shape with composition-dependent size may be performed by the following method: depositing at least one transition metal containing precipitate on a seed particle having a different transition metal composition than the precipitate; adding a controlled amount of a lithium source; and at least one heat treatment is carried out, wherein substantially all of the obtained particles contain seed-derived cores that are completely covered with a layer derived from the precipitate.
2. Conductive layer
The conductive layer conducts current from the positive electrode and at least partially covers at least one surface of the positive electrode.
According to some embodiments of the application, the conductive layer is 0.1 μm to 30 μm thick.
According to some embodiments of the present application, the conductive layer comprises a conductive agent comprising at least one of carbon black, acetylene black, fullerene, carbon nanotube, graphene, graphite.
3. Insulating layer
In order to avoid the contact between the conducting layer and the puncture object and the short circuit during the nail penetration, an insulating layer is arranged on the surface of the conducting layer.
According to some embodiments of the application, the insulating layer comprises a binder.
According to some embodiments of the present application, the insulating layer further comprises an insulating material.
According to some embodiments of the present application, the binder is present in an amount a of 2% or more and 100% or less by mass based on the weight of the insulating layer, and the insulating material is present in an amount 1-a by mass.
According to some embodiments of the present application, the insulating material comprises at least one of an inorganic insulating material and/or an organic insulating material.
According to some embodiments of the application, the inorganic insulating material comprises BaSO4、CaSiO3、γ-AlOOH、CaSiO4、Al2O3、TiO2At least one of; the organic insulating material comprises at least one of homopolymer or copolymer of ethylene, vinyl chloride, propylene, styrene, butadiene, vinylidene fluoride, tetrafluoroethylene and hexafluoropropylene.
According to some embodiments of the present application, the particle size D50 of the insulation material is 0.01 μm to 20 μm, preferably 0.5 μm to 5 μm. When the particle size of the insulating material is within this range, it is possible to ensure the uniformity of dispersion of the insulating material in the layer and the thickness of the insulating layer coating.
According to some embodiments of the present application, the insulating layer has a thickness h ≧ 0.5 μm.
According to some embodiments of the present application, the binder comprises at least one of polyvinylidene fluoride PVDF, polytetrafluoroethylene PTFE, sodium carboxymethylcellulose CMC, styrene butadiene rubber SBR, nitrile butadiene rubber, polyurethane, fluorinated rubber, polyvinyl alcohol PVA, sodium polyacrylate.
III, a barrier layer
In order to prevent short-circuiting, a separator layer is provided between the positive electrode and the negative electrode.
The separator layer may be disposed between the positive and negative electrodes in a known manner. For example, the surface of the electrode is coated with slurry for molding, or electrostatic spinning is performed on the surface of the electrode, or a pre-prepared separator is stacked with the positive electrode and the negative electrode in a conventional stacking manner.
For example, when the surface of the electrode is coated with slurry for molding, the separator layer includes inorganic particles and a binder selected from at least one of polyvinylidene fluoride (PVDF), Polytetrafluoroethylene (PTFE), sodium carboxymethylcellulose (CMC), Styrene Butadiene Rubber (SBR), nitrile butadiene rubber, polyurethane, fluorinated rubber, polyvinyl alcohol (PVA), and sodium polyacrylate.
According to some embodiments of the present application, the inorganic particles comprise BaSO4、CaSiO3、γ-AlOOH、CaSiO4、Al2O3、TiO2、SiO2At least one of (1).
According to some embodiments of the present application, the inorganic particles have a particle size D50 of 0.01 μm to 20 μm, preferably 0.5 μm to 5 μm.
The thickness of the membrane layer is arbitrary. In some embodiments, the membrane layer has a thickness greater than 1 μm, greater than 5 μm, or greater than 8 μm. In some embodiments, the membrane layer has a thickness of less than 50 μm, less than 40 μm, or less than 30 μm. In some embodiments, the membrane layer has a thickness within a range consisting of any two of the above values. When the thickness of the separator layer is within the above range, the insulating property and the mechanical strength can be secured, and the rate characteristic and the energy density of the electrochemical device can be secured.
When a porous material such as a porous membrane or nonwoven fabric is used as the separator layer, the porosity of the separator layer is arbitrary. In some embodiments, the porosity of the separator layer is greater than 20%, greater than 35%, or greater than 45%. In some embodiments, the porosity of the separator layer is less than 90%, less than 85%, or less than 75%. In some embodiments, the porosity of the separator layer is within a range consisting of any two of the above values. When the porosity of the separator layer is within the above range, insulation and mechanical strength can be secured, and membrane resistance can be suppressed, resulting in an electrochemical device having good rate characteristics.
The average pore size of the separator layer is also arbitrary. In some embodiments, the membrane layer has an average pore size of less than 0.5 μm or less than 0.2 μm. In some embodiments, the separator layer has an average pore size greater than 0.05 μm. In some embodiments, the separator layer has an average pore size within a range consisting of any two of the above values. If the average pore diameter of the separator layer exceeds the above range, short circuits are likely to occur. When the average pore diameter of the separator layer is within the above range, the membrane resistance can be suppressed while preventing short-circuiting, resulting in an electrochemical device having good rate characteristics.
IV, electrolyte
For a liquid secondary battery, the electrolyte used in the electrochemical device of the present application includes an electrolyte and a solvent dissolving the electrolyte. In some embodiments, the electrolyte used in the electrochemical device of the present application further comprises an additive.
In some embodiments, the electrolyte further comprises any non-aqueous solvent known in the art that can act as a solvent for the electrolyte.
In some embodiments, 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 ether, phosphorus-containing organic solvent, sulfur-containing organic solvent, and aromatic fluorine-containing solvent.
In some embodiments, examples of the cyclic carbonate may include, but are not limited to, one or more of the following: ethylene Carbonate (EC), Propylene Carbonate (PC) and butylene carbonate. In some embodiments, the cyclic carbonate has 3 to 6 carbon atoms.
In some embodiments, examples of the chain carbonates can include, but are not limited to, one or more of the following: and chain carbonates such as dimethyl carbonate, methylethyl carbonate, diethyl carbonate (DEC), methyl-n-propyl carbonate, ethyl-n-propyl carbonate, and di-n-propyl carbonate. Examples of chain carbonates substituted with fluorine may include, but are not limited to, one or more of the following: bis (fluoromethyl) carbonate, bis (difluoromethyl) carbonate, bis (trifluoromethyl) 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, and the like.
In some embodiments, examples of the cyclic carboxylic acid ester may include, but are not limited to, one or more of the following: one or more of gamma-butyrolactone and gamma-valerolactone. In some embodiments, a portion of the hydrogen atoms of the cyclic carboxylic acid ester may be substituted with fluorine.
In some embodiments, examples of the chain carboxylic acid ester 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, and the like. In some embodiments, a part of hydrogen atoms of the chain carboxylic acid ester may be substituted with fluorine. In some embodiments, examples of the fluorine-substituted chain carboxylic acid ester may include, but are not limited to, methyl trifluoroacetate, ethyl trifluoroacetate, propyl trifluoroacetate, butyl trifluoroacetate, 2,2, 2-trifluoroethyl trifluoroacetate, and the like.
In some embodiments, examples of the cyclic ether 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.
In some embodiments, examples of the chain ethers may include, but are not limited to, one or more of the following: dimethoxymethane, 1-dimethoxyethane, 1, 2-dimethoxyethane, diethoxymethane, 1-diethoxyethane, 1, 2-diethoxyethane, ethoxymethoxymethane, 1-ethoxymethoxyethane, 1, 2-ethoxymethoxyethane, and the like.
In some embodiments, examples of the phosphorus-containing organic solvent may include, but are not limited to, one or more of the following: trimethyl phosphate, triethyl phosphate, dimethyl ethyl phosphate, methyl diethyl phosphate, ethylene methyl phosphate, ethylene ethyl phosphate, triphenyl phosphate, trimethyl phosphite, triethyl phosphite, triphenyl phosphate, tris (2,2, 2-trifluoroethyl) phosphate, tris (2,2,3, 3-pentafluoropropyl) phosphate, and the like.
In some embodiments, examples of the sulfur-containing organic solvent may include, but are not limited to, one or more of the following: sulfolane, 2-methylsulfolane, 3-methylsulfolane, dimethylsulfone, diethylsulfone, ethylmethylsulfone, methylpropylsulfone, dimethylsulfoxide, methyl methanesulfonate, ethyl methanesulfonate, methyl ethanesulfonate, ethyl ethanesulfonate, dimethyl sulfate, diethyl sulfate and dibutyl sulfate. In some embodiments, a portion of the hydrogen atoms of the sulfur-containing organic solvent may be substituted with fluorine.
In some embodiments, the aromatic fluorine-containing solvent includes, but is not limited to, one or more of the following: fluorobenzene, difluorobenzene, trifluorobenzene, tetrafluorobenzene, pentafluorobenzene, hexafluorobenzene and trifluoromethylbenzene.
In some embodiments, the solvent used in the electrolyte of the present application includes cyclic carbonates, chain carbonates, cyclic carboxylates, chain carboxylates, and combinations thereof. In some embodiments, the solvent used in the electrolyte of the present application includes at least one of ethylene carbonate, propylene carbonate, diethyl carbonate, ethyl propionate, propyl propionate, n-propyl acetate, or ethyl acetate. In some embodiments, the solvent used in the electrolyte of the present application comprises: ethylene carbonate, propylene carbonate, diethyl carbonate, ethyl propionate, propyl propionate, gamma-butyrolactone, and combinations thereof.
After the chain carboxylate and/or the cyclic carboxylate are added into the electrolyte, the chain carboxylate and/or the cyclic carboxylate can form a passivation film on the surface of an electrode, so that the capacity retention rate of the electrochemical device after intermittent charging cycle is improved. In some embodiments, the electrolyte contains 1% to 60% of chain carboxylic acid ester, cyclic carboxylic acid ester, and combinations thereof. In some embodiments, the electrolyte comprises ethyl propionate, propyl propionate, γ -butyrolactone, and combinations thereof in an amount of 1% to 60%, 10% to 50%, 20% to 50%, based on the total weight of the electrolyte. In some embodiments, 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.
In some embodiments, examples of the additive may include, but are not limited to, one or more of the following: fluoro carbonate, ethylene carbonate containing carbon-carbon double bond, compound containing sulfur-oxygen double bond and acid anhydride.
In some embodiments, 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.
According to an embodiment of the present application, the propionate is contained in an amount of 1.5 to 30 times, 1.5 to 20 times, 2 to 20 times, or 5-20 times the additive, based on the total weight of the electrolyte.
In some embodiments, the additive comprises one or more fluoro carbonates. The fluoro carbonate may cooperate with the propionate to form a stable protective film on the surface of the negative electrode at the time of charge/discharge of the lithium ion battery, thereby inhibiting the decomposition reaction of the electrolyte.
In some embodiments, the fluoro carbonate has the formula C ═ O (OR)1)(OR2) Wherein R is1And R2Each selected from alkyl or haloalkyl groups having 1 to 6 carbon atoms, wherein R is1And R2At least one of which is selected from fluoroalkyl groups having 1-6 carbon atoms, and R1And R2Optionally together with the atoms to which they are attached form a 5-to 7-membered ring.
In some embodiments, examples of the fluoro-carbonates 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-methylethylene carbonate, 4-fluoro-5-methylethylene carbonate, trifluoromethyl methyl carbonate, trifluoroethylmethyl carbonate, and ethyl trifluoroethyl carbonate, and the like.
In some embodiments, the additive comprises one or more ethylene carbonates containing carbon-carbon double bonds. Examples of the ethylene carbonate containing a carbon-carbon double bond may include, but are not limited to, one or more of the following: vinylene carbonate, methyl vinylene carbonate, ethyl vinylene carbonate, 1, 2-dimethyl vinylene carbonate, 1, 2-diethyl vinylene carbonate, fluoroethylene carbonate and trifluoromethyl vinylene carbonate; vinyl ethylene carbonate, 1-methyl-2-vinyl ethylene carbonate, 1-ethyl-2-vinyl ethylene carbonate, 1-n-propyl-2-vinyl ethylene carbonate, 1-methyl-2-vinyl ethylene carbonate, 1-divinyl ethylene carbonate, 1, 2-divinyl ethylene carbonate, 1-dimethyl-2-methylene ethylene carbonate, 1-diethyl-2-methylene ethylene carbonate, and the like. In some embodiments, the ethylene carbonate containing a carbon-carbon double bond includes vinylene carbonate, which is easily available and can achieve more excellent effects.
In some embodiments, the additive comprises one or more compounds containing a sulfur-oxygen double bond. Examples of the compound containing a thiooxy double bond may include, but are not limited to, one or more of the following: cyclic sulfuric acid esters, chain sulfonic acid esters, cyclic sulfonic acid esters, chain sulfurous acid esters, cyclic sulfurous acid esters, and the like.
Examples of the cyclic sulfate may include, but are not limited to, one or more of the following: 1, 2-ethanediol sulfate, 1, 2-propanediol sulfate, 1, 3-propanediol 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.
Examples of the chain sulfate may include, but are not limited to, one or more of the following: dimethyl sulfate, ethyl methyl sulfate, diethyl sulfate, and the like.
Examples of the chain sulfonate may include, but are not limited to, one or more of the following: fluorosulfonate esters such as methyl fluorosulfonate and ethyl fluorosulfonate, methyl methanesulfonate, ethyl methanesulfonate, butyl methanesulfonate, methyl 2- (methylsulfonyloxy) propionate, and ethyl 2- (methylsulfonyloxy) propionate.
Examples of the cyclic sulfonate ester may include, but are not limited to, one or more of the following: 1, 3-propane sultone, 1-fluoro-1, 3-propane sultone, 2-fluoro-1, 3-propane sultone, 3-fluoro-1, 3-propane sultone, 1-methyl-1, 3-propane sultone, 2-methyl-1, 3-propane sultone, 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, 3-propane sultone, 2-fluoro-1, 3-sultone, 2-propane-1, 3-sultone, 2-fluoro-propane-1, 3-sultone, 1-fluoro-2-propene-1, 3-sultone, 2-fluoro-2-propene-1, 3-sultone, 3-fluoro-2-propene-1, 3-sultone, 1-methyl-1-propene-1, 3-sultone, 2-methyl-1-propene-1, 3-sultone, 3-methyl-1-propene-1, 3-sultone, 1-methyl-2-propene-1, 3-sultone, 2-methyl-2-propene-1, 3-sultone, 3-methyl-2-propene-1, 3-sultone, 1, 4-butanesultone, 1, 5-pentanesulfonactone, methylene methanedisulfonate, ethylene methanedisulfonate, and the like.
Examples of chain-like sulfites can include, but are not limited to, one or more of the following: dimethyl sulfite, ethyl methyl sulfite, diethyl sulfite, and the like.
Examples of cyclic sulfites can include, but are not limited to, one or more of the following: 1, 2-ethanediol sulfite, 1, 2-propanediol sulfite, 1, 3-propanediol sulfite, 1, 2-butanediol sulfite, 1, 3-butanediol sulfite, 1, 4-butanediol sulfite, 1, 2-pentanediol sulfite, 1, 3-pentanediol sulfite, 1, 4-pentanediol sulfite, and 1, 5-pentanediol sulfite, etc.
In some embodiments, the additive comprises one or more anhydrides. Examples of the acid anhydride may include, but are not limited to, one or more of cyclic phosphoric anhydride, carboxylic anhydride, disulfonic anhydride, and carboxylic sulfonic anhydride. Examples of the cyclic phosphoric anhydride may include, but are not limited to, one or more of trimethylphosphoric cyclic anhydride, triethylphosphoric cyclic anhydride and tripropylphosphoric cyclic anhydride. Examples of the carboxylic acid anhydride may include, but are not limited to, one or more of succinic anhydride, glutaric anhydride, and maleic anhydride. Examples of the disulfonic anhydride can include, but are not limited to, one or more of ethane disulfonic anhydride and propane disulfonic anhydride. Examples of the carboxylic sulfonic anhydride may include, but are not limited to, one or more of sulfobenzoic anhydride, sulfopropionic anhydride, and sulfobutyric anhydride.
In some embodiments, the additive is a combination of a fluoro carbonate and ethylene carbonate containing a carbon-carbon double bond. In some embodiments, the additive is a combination of a fluoro carbonate and a compound containing a thiooxy double bond. In some embodiments, the additive is a combination of a fluoro carbonate and a compound having 2-4 cyano groups. In some embodiments, the additive is a combination of a fluoro carbonate and a cyclic carboxylic acid ester. In some embodiments, the additive is a combination of a fluoro carbonate and a 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 a fluoro carbonate and a sulfonic anhydride. In some embodiments, the additive is a combination of a fluorocarbonate and a carboxylic acid sulfonic anhydride.
In the present application, the electrolyte is not particularly limited, and any known electrolyte can be used. In the case of a lithium secondary battery, a lithium salt is generally used. Examples of the electrolyte may include, but are not limited to, LiPF6、LiBF4、LiClO4、LiAlF4、LiSbF6、LiTaF6、LiWF7Inorganic lithium salts; LiWOF5Lithium tungstate species; HCO2Li、CH3CO2Li、CH2FCO2Li、CHF2CO2Li、CF3CO2Li、CF3CH2CO2Li、CF3CF2CO2Li、CF3CF2CF2CO2Li、CF3CF2CF2CF2CO2Lithium carboxylates such as Li; FSO3Li、CH3SO3Li、CH2FSO3Li、CHF2SO3Li、CF3SO3Li、CF3CF2SO3Li、CF3CF2CF2SO3Li、CF3CF2CF2CF2SO3Lithium sulfonates such as Li; LiN (FCO)2、LiN(FCO)(FSO2)、LiN(FSO2)2、LiN(FSO2)(CF3SO2)、LiN(CF3SO2)2、LiN(C2F5SO2)2Cyclic 1, 2-perfluoroethane bis-sulfonyl imide lithium, cyclic 1, 3-perfluoropropane bis-sulfonyl imide lithium, LiN (CF)3SO2)(C4F9SO2) Lithium imide salts; LiC (FSO)2)3、LiC(CF3SO2)3、LiC(C2F5SO2)3Lithium methide salts; lithium (malonate) borate salts such as lithium bis (malonate) borate salt and lithium difluoro (malonate) borate salt; lithium (malonate) phosphates such as lithium tris (malonate) phosphate, lithium difluorobis (malonate) phosphate, and lithium tetrafluoro (malonate) phosphate; and LiPF4(CF3)2、LiPF4(C2F5)2、LiPF4(CF3SO2)2、LiPF4(C2F5SO2)2、LiBF3CF3、LiBF3C2F5、LiBF3C3F7、LiBF2(CF3)2、LiBF2(C2F5)2、LiBF2(CF3SO2)2、LiBF2(C2F5SO2)2Fluorine-containing organic lithium salts; lithium oxalato borate salts such as lithium difluorooxalato borate and lithium bis (oxalato) borate; lithium oxalato phosphate salts such as lithium tetrafluorooxalato phosphate, lithium difluorobis (oxalato) phosphate, and lithium tris (oxalato) phosphate.
In some embodiments, the electrolyte is selected from LiPF6、LiSbF6、LiTaF6、FSO3Li、CF3SO3Li、LiN(FSO2)2、LiN(FSO2)(CF3SO2)、LiN(CF3SO2)2、LiN(C2F5SO2)2Cyclic 1, 2-perfluoroethane bissulfonylimide lithium, cyclic 1, 3-perfluoropropane bissulfonylimide lithium, and LiC (FSO)2)3、LiC(CF3SO2)3、LiC(C2F5SO2)3、LiBF3CF3、LiBF3C2F5、LiPF3(CF3)3、LiPF3(C2F5)3Lithium difluorooxalato borate, lithium bis (oxalato) borate, or lithium difluorobis (oxalato) phosphate, which contribute to improvement in output characteristics, high-rate charge-discharge characteristics, high-temperature storage characteristics, cycle characteristics, and the like of an electrochemical device.
The content of the electrolyte is not particularly limited as long as the effects of the present application are not impaired. In some embodiments, the total molar concentration of lithium in the electrolyte is greater than 0.3mol/L or greater, greater than 0.4mol/L, or greater than 0.5 mol/L. In some embodiments, the total molar concentration of lithium in the electrolyte is less than 3mol/L, less than 2.5mol/L, or less than 2.0 mol/L. In some embodiments, the total molar concentration of lithium in the electrolyte is within a range consisting of any two of the above values. When the electrolyte concentration is within the above range, lithium as charged particles is not excessively small, and the viscosity can be made to be in an appropriate range, so that good conductivity is easily ensured.
In the case where two or more electrolytes are used, the electrolyte includes at least one salt selected from the group consisting of monofluorophosphate, borate, oxalate and fluorosulfonate. In some embodiments, the electrolyte comprises a salt selected from the group consisting of a monofluorophosphate, an oxalate, and a fluorosulfonate. In some embodiments, the electrolyte comprises a lithium salt. In some embodiments, the content of the salt selected from the group consisting of monofluorophosphate, borate, oxalate and fluorosulfonate is more than 0.01% or more than 0.1% based on the total weight of the electrolyte. In some embodiments, the content of the salt selected from the group consisting of monofluorophosphate, borate, oxalate and fluorosulfonate is less than 20% or less than 10% based on the total weight of the electrolyte. In some embodiments, the amount of a salt selected from the group consisting of monofluorophosphates, borates, oxalates, and fluorosulfonates is within a range consisting of any two of the foregoing values.
In some embodiments, the electrolyte comprises one or more substances selected from the group consisting of monofluorophosphates, borates, oxalates, and fluorosulfonates, and one or more salts in addition thereto. As other salts, there may be mentioned the lithium salts exemplified hereinabove, and LiPF in some examples6、LiN(FSO2)(CF3SO2)、LiN(CF3SO2)2、LiN(C2F5SO2)2Cyclic 1, 2-perfluoroethane bissulfonylimide lithium, cyclic 1, 3-perfluoropropane bissulfonylimide lithium, and LiC (FSO)2)3、LiC(CF3SO2)3、LiC(C2F5SO2)3、LiBF3CF3、LiBF3C2F5、LiPF3(CF3)3、LiPF3(C2F5)3. In some embodiments, the additional salt is LiPF6。
In some embodiments, the amount of the additional salt is greater than 0.01% or greater than 0.1% based on the total weight of the electrolyte. In some embodiments, the amount of the other salt is less than 20%, less than 15%, or less than 10% based on the total weight of the electrolyte. In some embodiments, the amount of other salts is within a range consisting of any two of the above values. The other salts having the above contents help to balance the conductivity and viscosity of the electrolyte.
The electrolyte solution may contain, in addition to the above-mentioned solvent, additive and electrolyte salt, additional additives such as a negative electrode coating film forming agent, a positive electrode protecting agent, and an overcharge preventing agent, as required. As the additive, additives generally used in nonaqueous electrolyte secondary batteries may be used, and examples thereof may include, but are not limited to, vinylene carbonate, succinic anhydride, biphenyl, cyclohexylbenzene, 2, 4-difluoroanisole, propane sultone, propene sultone, and the like. These additives may be used alone or in any combination thereof. The content of these additives in the electrolyte solution is not particularly limited, and may be appropriately set according to the kind of the additives. In some embodiments, the additive is present in an amount 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.
V, electrochemical device
The electrochemical device includes an electrode assembly, a current collecting structure, an outer case, and a protective member.
Electrode assembly
The electrode assembly may have any of a laminated structure in which the positive electrode and the negative electrode are laminated with the separator layer interposed therebetween, and a wound structure in which the positive electrode and the negative electrode are wound in a spiral shape with the separator layer interposed therebetween.
Current collecting structure
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. When the electrode group has 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. Since the internal resistance increases when the electrode area increases, it is also preferable to provide 2 or more terminals in the electrode to reduce the resistance. When the electrode group has the above-described wound structure, 2 or more lead structures are provided for the positive electrode and the negative electrode, respectively, and the terminals are bundled together, whereby the internal resistance can be reduced.
External casing
The material of the outer case is not particularly limited as long as it is stable to the electrolyte used. The outer case may be made of, but not limited to, a metal such as nickel-plated steel plate, stainless steel, aluminum, an aluminum alloy, or a magnesium alloy, or a laminated film of a resin and an aluminum foil. In some embodiments, the outer case is a metal or laminated film of aluminum or aluminum alloy.
The metal-based outer case includes, but is not limited to, a hermetically sealed structure formed by welding metals to each other by laser welding, resistance welding, or ultrasonic welding; or a caulking structure formed by using the metal through a resin spacer. The outer case using the laminated film includes, but is not limited to, a sealed structure formed by thermally bonding resin layers to each other. In order to improve the sealing property, a resin different from the resin used for the laminate film may be interposed between the resin layers. When the resin layer is thermally adhered to the current collecting terminal to form a sealed structure, a resin having a polar group or a modified resin into which a polar group has been introduced may be used as the resin to be interposed, because of the bonding between the metal and the resin. The shape of the outer package is also arbitrary, and may be any of a cylindrical shape, a square shape, a laminated shape, a button shape, a large size, and the like.
Protective element
The protection element may be a Positive Temperature Coefficient (PTC) element whose resistance increases when abnormal heat radiation or an excessive current flows, a temperature fuse, a thermistor, a valve (current cutoff valve) that cuts off a current flowing through a circuit by rapidly increasing the internal pressure or internal temperature of the battery when abnormal heat radiation occurs, or the like. The protective element may be selected from elements that do not operate under normal use of high current, and may be designed so that abnormal heat release or thermal runaway does not occur even if the protective element is not present.
VI, application
The electrochemical device of the present application includes any device in which electrochemical reactions occur, and specific examples thereof include all kinds of primary batteries, secondary batteries, fuel cells, solar cells, or capacitors. In particular, 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 an 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 for any electronic device known in the art. In some embodiments, the electrochemical device of the present application can be used in, but is not limited to, notebook computers, pen-input computers, mobile computers, electronic book players, cellular phones, portable facsimile machines, portable copiers, portable printers, headphones, video recorders, liquid crystal televisions, portable cleaners, portable CDs, mini-discs, transceivers, electronic organizers, calculators, memory cards, portable recorders, radios, backup power supplies, motors, automobiles, motorcycles, mopeds, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, household large batteries, lithium ion capacitors, and the like.
While the preparation of lithium ion batteries including the electrode assemblies described herein is illustrated below with reference to specific examples, those skilled in the art will appreciate that the preparation methods described herein are merely examples and that any other suitable preparation methods are within the scope of the present application.
Fig. 1 shows a schematic view of an embodiment of an electrode assembly of the present application, wherein the electrode assembly includes a positive electrode 1, a negative electrode 2 disposed symmetrically with respect to a negative electrode current collector 4, a separator layer 3 between the positive electrode 1 and the negative electrode 2, and a tab 5.
The positive electrode 1 includes a positive electrode active layer 11 and a positive electrode conductive layer 12, wherein the positive electrode conductive layer 12 completely covers the positive electrode active layer 11. The negative electrode includes a negative electrode current collector 4 and a negative electrode active layer 21 disposed on a surface of the negative electrode current collector 4. The separator layer 3 is composed of an inorganic layer, is provided on the surface of the negative electrode active layer 21, and electrically insulates the positive electrode 1 and the negative electrode 2 from each other. A positive electrode tab 5 is led out of the conductive layer 12.
Fig. 2 shows a schematic view of another embodiment of an electrode assembly of the present application. The structure of the electrode assembly in fig. 2 is different from that of the electrode assembly in fig. 1 in that: the positive electrode conductive layer 12 is disposed only on the surface of the positive electrode active layer 11, not covering the periphery of the positive electrode active layer 11, and the electrode assembly of fig. 2 further includes an insulating layer 6 disposed on the surface of the positive electrode conductive layer 12.
Fig. 3 shows a schematic view of yet another embodiment of an electrode assembly of the present application. The structure of the electrode assembly in fig. 3 is different from that of the electrode assembly in fig. 1 in that: the separator layer 3 completely covers the negative active layer 21 to prevent short circuit or self-discharge of the battery.
Examples
Performance evaluations were conducted below with respect to examples and comparative examples of lithium ion batteries including the electrode assembly of the present application.
Preparation of lithium ion battery
Example 1
1. Preparation of the negative electrode
Mixing the artificial graphite, the styrene-butadiene rubber and the sodium carboxymethylcellulose with deionized water according to the mass ratio of 96% to 2%, and uniformly stirring to obtain the cathode slurry. The negative electrode slurry was coated on a copper foil of 12 μm. Drying, cold pressing, cutting into pieces, and welding tabs to obtain the cathode.
2. Preparation of diaphragm layer slurry
Mixing an inorganic material gamma-AlOOH and a binder PVDF according to the weight ratio of 80: 20, adding deionized water, and stirring under the action of a vacuum stirrer until a system becomes uniform slurry to obtain coating slurry, wherein the solid content is 40 wt%.
3. Preparation of negative electrode/diaphragm layer pole piece
And coating a layer of diaphragm layer slurry on the two side surfaces of the negative electrode to be used as a diaphragm layer. The thickness of the diaphragm layer is 15 μm, and the negative electrode/diaphragm layer pole piece is obtained after drying.
4. Preparation of electrode assemblies
The positive electrode active material lithium cobaltate (LiCoO)2) Mixing a conductive agent SP and a binding agent polyvinylidene fluoride according to the weight ratio of 97: 1.4: 1.6, adding N-methyl pyrrolidone (NMP), and stirring under the action of a vacuum stirrer until a system becomes uniform slurry to obtain conventional anode slurry, wherein the solid content of the anode slurry is 72 wt%; and coating the positive electrode slurry on the surface of the diaphragm layer, and drying to obtain the cathode, diaphragm layer and positive electrode integrated structure.
5. And leading out a positive pole lug at the edge of the positive pole by using conductive adhesive.
6. Preparation of lithium ion battery
The resulting electrode assembly was wound and placed in an outer packaging foil, leaving a liquid injection port. And (4) pouring electrolyte from the electrolyte injection port, packaging, and performing formation, capacity and other processes to obtain the lithium ion battery.
Examples 2 to 15
Step 1 to step 4 are the same as in example 1, except that: and further coating the conductive slurry on the surface of the anode, drying to form a conductive layer, and leading out an anode tab at the edge of the conductive layer by using a conductive adhesive.
The conductive paste consists of a conductive agent and a binder, and the preparation method of the conductive paste comprises the following steps:
mixing the conductive agent and the binder according to a ratio, adding N-methyl pyrrolidone (NMP), and uniformly dispersing to obtain the conductive slurry.
Preparation of lithium ion battery
The resulting electrode assembly was wound and placed in an outer packaging foil, leaving a liquid injection port. And (4) pouring electrolyte from the electrolyte injection port, packaging, and performing formation, capacity and other processes to obtain the lithium ion battery.
Relevant parameters of the lithium ion batteries of examples 1 to 15 are shown in table 2.
Example 16 to example 25
On the basis of the embodiment 5, the insulating layer slurry is further coated on the surface of the conductive layer and dried to form the insulating layer.
The insulating layer slurry is prepared by mixing a binder and an insulating material according to a ratio, adding N-methyl pyrrolidone (NMP) and uniformly dispersing.
Relevant parameters for the lithium ion batteries of examples 16 to 25 are shown in table 3.
Comparative example 1
1. Preparation of the Positive electrode
The positive electrode active material lithium cobaltate (LiCoO)2) Mixing the conductive agent SP and the binding agent polyvinylidene fluoride with N-methyl pyrrolidone (NMP) according to the mass ratio of 95 percent to 2 percent to 3 percent, adding the auxiliary agent, and uniformly stirring to obtain the anode slurry. And coating the anode slurry on an aluminum foil with the thickness of 12 mu m, drying, cold pressing, cutting into pieces, and welding a tab to obtain the anode.
2. Preparation of the negative electrode
Mixing the artificial graphite, the styrene-butadiene rubber and the sodium carboxymethylcellulose with deionized water according to the mass ratio of 96% to 2%, and uniformly stirring to obtain the cathode slurry. The negative electrode slurry was coated on a copper foil of 12 μm. Drying, cold pressing, cutting into pieces, and welding tabs to obtain the cathode.
3. Preparation of the electrolyte
Mixing EC, PC, PP and DEC (weight ratio 1: 1) under dry argon atmosphere, adding LiPF6Mixing uniformly to form a basic electrolyte, wherein LiPF6The concentration of (2) is 1.15 mol/L.
4. Preparation of the separator
Polyethylene (PE) porous polymer films were used as separators.
5. Preparation of lithium ion battery
The obtained positive electrode, separator and negative electrode were wound in order and placed in an outer packaging foil, leaving a liquid inlet. And (4) pouring electrolyte from the electrolyte injection port, packaging, and performing formation, capacity and other processes to obtain the lithium ion battery.
Comparative example 2
1. Preparation of the Positive electrode
The positive electrode active material lithium cobaltate (LiCoO)2) Conductive agent SP and polyvinylidene fluoride as a binder are mixed according to the weight ratio of 97: 1.4: 1.6, N-methyl pyrrolidone (NMP) is added, the mixture is stirred under the action of a vacuum stirrer until the system becomes uniform slurry, and conventional anode slurry is obtained, wherein the solid content of the anode slurry is 72 wt%, and the anode slurry is coated on an aluminum foil with the thickness of 12 mu m. Drying, cold pressing, cutting into pieces, and welding tabs to obtain the anode.
2. Preparation of diaphragm layer slurry
Mixing an inorganic material gamma-AlOOH and a binder PVDF according to the weight ratio of 80: 20, adding deionized water, and stirring under the action of a vacuum stirrer until a system becomes uniform slurry to obtain coating slurry, wherein the solid content is 40 wt%.
3. Positive electrode/diaphragm layer pole piece
And coating a layer of diaphragm layer slurry on the two side surfaces of the positive electrode to be used as a diaphragm layer. The thickness of the diaphragm layer is 15 μm, and the positive electrode/diaphragm layer pole piece is obtained after drying.
4. Preparation of electrode assemblies
Mixing the artificial graphite, the styrene-butadiene rubber and the sodium carboxymethylcellulose with deionized water according to the mass ratio of 96% to 2%, and uniformly stirring to obtain the cathode slurry. And coating the cathode slurry on the surface of the diaphragm layer, and drying to obtain the cathode, diaphragm layer and anode integrated structure.
5. And a negative pole tab is led out from the edge of the negative pole by using conductive adhesive.
6. Preparation of lithium ion battery
The resulting electrode assembly was wound and placed in an outer packaging foil, leaving a liquid injection port. And (4) pouring electrolyte from the electrolyte injection port, packaging, and performing formation, capacity and other processes to obtain the lithium ion battery.
Second, testing method
1. Method for testing passing rate of puncture test
10 groups of battery cores prepared from the same electrode assembly are taken, and the battery cores are charged to full charge voltage at 0.5C and CV is 0.05C; the temperature is 20 +/-5 ℃, the nail diameter is 4mm, the puncture speed is 30mm/s, and the retention time is 300 s; and regarding the cells as passing tests without fire or explosion, and defining the number n of the passed cells/the total number 10 of the tested cells as the passing rate of the puncture test.
2. Energy density testing method
0.5 CC to full charge voltage, CV to 0.05C, 0.5C DC to 3.0V, recording discharge capacity energy density ═ discharge capacity/(length × width ×) thickness
Third, test results
Table 1 shows the specific structural compositions of example 1 and comparative examples 1-2 and the corresponding puncture throughput rates and energy densities.
TABLE 1
Figure BDA0002816897960000231
As can be seen from the results in table 1, example 1, in which the Al foil of the positive electrode current collector was omitted, has a significantly improved penetration rate and energy density, as compared with comparative example 1. Compared with comparative example 2 without the copper foil of the negative current collector, the lithium ion battery adopting the electrode assembly has higher puncture test passing rate. That is, the lithium ion battery using the electrode assembly described herein has higher safety. In addition, since the positive electrode current collector is not required to be used, the lithium ion battery using the electrode assembly of the present application has a higher energy density under the same other conditions.
The effect of the conductive layer on the performance of the lithium ion battery is studied, and the relevant parameters and test results of the conductive agent, the binder, the thickness of the conductive layer, and the like in the conductive layer are shown in table 2.
TABLE 2
Figure BDA0002816897960000241
Figure BDA0002816897960000251
The results in table 2 show that, as can be seen from comparison between examples 2 to 10 and example 1, increasing the conductive layer can improve the cell dynamic performance and improve the cell rate. Examples 10, 14, 15 with a 75% conductive agent content have comparable kinetic performance to comparative example 1.
On the basis of example 5 in table 2, an insulating layer was provided on the surface of the conductive layer. The effect of the binder and insulating material in the insulating layer on the performance of lithium ion batteries is now being investigated. The relevant parameters and test results are shown in table 3.
TABLE 3
Figure BDA0002816897960000252
Figure BDA0002816897960000261
The results in table 3 indicate that the embodiment in which the insulating layer is further provided on the surface of the conductive layer has an improved penetration rate, because the presence of the insulating layer can avoid the contact between the metal piercing object and the conductive layer, thereby avoiding the conductive layer from being communicated with the negative electrode through the metal piercing object, causing short circuit and thermal runaway, and further greatly improving the safety performance of the electrochemical device.
Although illustrative embodiments have been illustrated and described, it will be appreciated by those skilled in the art that the above embodiments are not to be construed as limiting the application and that changes, substitutions and alterations can be made to the embodiments without departing from the spirit, principles and scope of the application.

Claims (10)

1. An electrode assembly, it includes the negative pole current collector, sets up in negative pole active layer, the diaphragm layer, the positive pole active layer of at least one surface of the negative pole current collector, the diaphragm layer sets up in negative pole active layer with the positive pole active layer, and the projection area of at least part surface along perpendicular to part surface direction of positive pole active layer does not have positive pole metal current collector.
2. The electrode assembly according to claim 1, wherein a surface of the positive electrode active layer is provided with a conductive layer.
3. The electrode assembly of claim 2, the conductive layer comprising a conductive agent that satisfies at least one of the following conditions:
a. the thickness of the conductive layer is 0.1-30 μm;
b. the conductive agent comprises at least one of carbon black, acetylene black, fullerene, carbon nano tube, graphene and graphite.
4. The electrode assembly of claim 2, a surface of the conductive layer being provided with an insulating layer.
5. The electrode assembly of claim 4, the insulating layer comprising a binder that satisfies at least one of the following conditions:
c. the insulating layer comprises an insulating material;
d. the mass percentage of the binder is a based on the weight of the insulating layer, wherein a is more than or equal to 2% and less than or equal to 100%;
e. the thickness h of the insulating layer is more than or equal to 0.5 mu m.
6. The electrode assembly of claim 5, the insulating material comprising at least one of an inorganic insulating material and/or an organic insulating material that satisfies at least one of the following conditions:
f. the inorganic insulating material comprises BaSO4、CaSiO3、γ-AlOOH、CaSiO4、Al2O3、TiO2At least one of; the organic insulating material comprises at least one of homopolymer or copolymer of ethylene, vinyl chloride, propylene, styrene, butadiene, vinylidene fluoride, tetrafluoroethylene and hexafluoropropylene;
g. the average particle diameter of the insulating material is 0.01 to 20 μm.
7. The electrode assembly of claim 1, the electrode assembly satisfying at least one of the following conditions:
h. the electrode assembly further includes a tab connected with the conductive layer;
i. the separator layer comprises at least one of an inorganic layer and a polyolefin porous layer;
j. the negative active layer comprises a negative active material, and the negative active material comprises at least one of graphite and a silicon-based material;
k. the partial surface accounts for more than 50%, preferably more than 80%, more preferably more than 95% of the surface of the positive electrode active layer;
the adhesion of the positive electrode active layer to the separator layer is greater than or equal to 2N/m.
8. The electrode assembly of claim 7, the composition of the inorganic layer comprising inorganic particles and a binder satisfying at least one of the following conditions:
based on the weight of the inorganic layer, the mass percentage of the binder is b, wherein b is more than or equal to 5% and less than or equal to 40%;
n. the inorganic particles comprise BaSO4、CaSiO3、γ-AlOOH、CaSiO4、Al2O3、TiO2、SiO2At least one of;
the inorganic particles have a D50 of 0.01 to 20 μ ι η;
p. the binder comprises at least one of polyvinylidene fluoride, polytetrafluoroethylene, sodium carboxymethylcellulose, styrene butadiene rubber, nitrile butadiene rubber, polyurethane, fluorinated rubber, polyvinyl alcohol or sodium polyacrylate.
9. An electrochemical device comprising the electrode assembly according to any one of claims 1 to 8.
10. An electronic device comprising the electrochemical device of claim 9.
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