CN113113611A - Composite current collector, battery pole piece, battery core and lithium ion secondary battery - Google Patents

Composite current collector, battery pole piece, battery core and lithium ion secondary battery Download PDF

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Publication number
CN113113611A
CN113113611A CN202110341822.6A CN202110341822A CN113113611A CN 113113611 A CN113113611 A CN 113113611A CN 202110341822 A CN202110341822 A CN 202110341822A CN 113113611 A CN113113611 A CN 113113611A
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China
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current collector
layer
composite current
ion secondary
lithium ion
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Chinese (zh)
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栗西亮
李涛
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Shanghai Feihong Chuanglian New Energy Development Co ltd
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Shanghai Copious Industrial Co ltd
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Priority to CN202110341822.6A priority Critical patent/CN113113611A/en
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    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00Electrodes
    • H01M4/02Electrodes composed of, or comprising, active material
    • H01M4/64Carriers or collectors
    • H01M4/66Selection of materials
    • H01M4/665Composites
    • H01M4/667Composites in the form of layers, e.g. coatings
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00Secondary cells; Manufacture thereof
    • H01M10/05Accumulators with non-aqueous electrolyte
    • H01M10/052Li-accumulators
    • H01M10/0525Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00Secondary cells; Manufacture thereof
    • H01M10/05Accumulators with non-aqueous electrolyte
    • H01M10/058Construction or manufacture
    • H01M10/0585Construction or manufacture of accumulators having only flat construction elements, i.e. flat positive electrodes, flat negative electrodes and flat separators
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00Secondary cells; Manufacture thereof
    • H01M10/05Accumulators with non-aqueous electrolyte
    • H01M10/058Construction or manufacture
    • H01M10/0587Construction or manufacture of accumulators having only wound construction elements, i.e. wound positive electrodes, wound negative electrodes and wound separators
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00Electrodes
    • H01M4/02Electrodes composed of, or comprising, active material
    • H01M4/13Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/131Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00Electrodes
    • H01M4/02Electrodes composed of, or comprising, active material
    • H01M4/13Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/133Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00Electrodes
    • H01M4/02Electrodes composed of, or comprising, active material
    • H01M4/13Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/134Electrodes based on metals, Si or alloys
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00Electrodes
    • H01M4/02Electrodes composed of, or comprising, active material
    • H01M4/13Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/136Electrodes based on inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01MPROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2220/00Batteries for particular applications
    • H01M2220/20Batteries in motive systems, e.g. vehicle, ship, plane
    • YGENERAL 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
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02EREDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10Energy storage using batteries
    • YGENERAL 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
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02PCLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50Manufacturing or production processes characterised by the final manufactured product

Abstract

The invention relates to a composite current collector, a battery pole piece, a battery core and a lithium ion secondary battery, which improve the structure of the current collector used in the lithium ion secondary battery, adopt the composite current collector with a porous structure, enable a positive electrode active substance layer and/or a negative electrode active substance layer to enter pores of the composite current collector, improve the load capacity of a unit area, enable the thickness of the pole piece with the same load capacity to be smaller or enable more active substances to be arranged on the unit area, and enable the energy density of the lithium ion secondary battery to be obviously improved. In addition, due to the porous structure of the composite current collector, in the lithium desorption and intercalation process of the lithium ion secondary battery, lithium ions can penetrate through the composite current collector to the other side of the current collector or be desorbed and intercalated into the active material layer, and the safety of the battery core can be improved.

Description

Composite current collector, battery pole piece, battery core and lithium ion secondary battery
Technical Field
The invention relates to the technical field of lithium ion secondary batteries, in particular to a composite current collector, a battery pole piece, a battery core and a lithium ion secondary battery.
Background
Lithium ion secondary batteries are widely used in the fields of power, 3C, energy storage, and the like. In recent years, the application and popularization of electric vehicles are accelerated by policies of limiting carbon emission and limiting and prohibiting selling of fuel vehicles in europe, china and the like. However, the energy density of batteries has been plagued. The lithium battery is one of main sources of dead weight of the electric automobile, the power consumption of hundreds of kilometers is closely related to the dead weight of the automobile, and the problem to be solved by the lithium battery at present is to improve the energy density of the battery core.
Disclosure of Invention
The invention aims to provide a composite current collector, a battery pole piece, a battery core and a lithium ion secondary battery, and the energy density of the lithium ion secondary battery is improved by improving the structure of the current collector.
In order to achieve the purpose, the invention provides the following scheme:
a composite current collector comprising a polymer-based porous support layer and a conductive layer;
the polymer-based porous support layer is formed by combining a plurality of polymer skeletons in a physical or chemical mode; the conducting layer is arranged on at least one of the polymer frameworks.
A battery pole piece comprises the composite current collector and an active substance layer;
the active material layer is disposed on a surface and/or within pores of the composite current collector.
A battery cell comprises a positive pole piece, a separation film and a negative pole piece;
the positive pole piece, the isolating film and the negative pole piece are arranged in a stacked or winding manner;
the positive pole piece comprises a positive current collector and a positive active substance layer arranged on the positive current collector;
the negative pole piece comprises a negative pole current collector and a negative pole active substance layer arranged on the negative pole current collector;
the positive current collector and/or the negative current collector are/is the composite current collector; when the positive current collector is the composite current collector, the composite current collector is a first composite current collector, and the positive active material layer is arranged on the surface and/or in the pores of the first composite current collector; when the negative current collector is the composite current collector, the composite current collector is a second composite current collector, and the negative active material layer is arranged on the surface and/or in the pores of the second composite current collector.
A lithium ion secondary battery, comprising one or more of the above-described cells and an electrolyte;
the battery cell is located in the electrolyte.
According to the specific embodiment provided by the invention, the invention discloses the following technical effects:
according to the composite current collector, the battery pole piece, the battery core and the lithium ion secondary battery, the structure of the current collector used in the lithium ion secondary battery is improved, the composite current collector with the porous structure is adopted, so that the positive electrode active substance layer and/or the negative electrode active substance layer can enter the pores of the composite current collector, the load capacity of a unit area is improved, the thickness of the pole piece with the same load capacity is smaller or more active substances can be arranged on the unit area, and the energy density of the lithium ion secondary battery can be obviously improved. In addition, the porous structure of the composite current collector enables lithium ions to penetrate through the composite current collector to the other side of the current collector or be embedded in the active material layer in the lithium embedding and removing process of the lithium ion secondary battery, and therefore the safety of the battery cell can be improved. Compared with the traditional metal current collector, the contact area among the composite current collector, the active substance layer and the electrolyte is larger, the contact is more sufficient, the internal resistance of the battery is smaller, the safety is higher, the electrochemical performance is better, the low-temperature performance is good, and the safety, the energy density, the low-temperature performance and the stability of the lithium ion secondary battery can be obviously improved.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without creative efforts.
Fig. 1 is a schematic structural diagram of a polymer-based porous support layer provided in embodiment 1 of the present invention.
Fig. 2 is a schematic connection diagram of the polymer skeleton and the conductive layer provided in embodiment 1 of the present invention.
Fig. 3 is a schematic structural diagram of only disposing the first protection layer according to embodiment 1 of the present invention.
Fig. 4 is a schematic structural diagram of only disposing the second passivation layer according to embodiment 1 of the present invention.
Fig. 5 is a schematic structural diagram of simultaneously providing a first protective layer and a second protective layer in embodiment 1 of the present invention.
Description of the symbols:
1-a polymeric backbone; 2-a conductive layer; 3-a first protective layer; 4-a second protective layer.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The invention aims to provide a composite current collector, a battery pole piece, a battery core and a lithium ion secondary battery, and the energy density of the lithium ion secondary battery is improved by improving the structure of the current collector.
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in further detail below.
Example 1:
the safety, energy density, low-temperature performance and stability of the battery are always suffered from defects. The safety mainly relates to mechanical damage, lithium precipitation and electrolyte failure. The lithium battery is one of main sources of dead weight of the electric automobile, the power consumption of hundreds of kilometers is closely related to the dead weight of the automobile, and the problem to be solved by the lithium battery at present is to improve the energy density of the battery core. The high-low temperature performance refers to the capacity exertion of the lithium ion secondary battery at high and low temperatures, the capacity exertion of the battery is greatly limited at low temperature, and the phenomenon is more obvious at lower temperature. When the temperature is higher, the viscosity of the electrolyte is low, the polarization is small, and the internal resistance of the battery is small, which is relatively beneficial to the exertion of the capacity of the lithium ion secondary battery, so the low-temperature performance is also the problem to be solved urgently at present
In view of the above problems, the present embodiment is directed to providing a composite current collector including a polymer-based porous support layer and a conductive layer 2. The polymer-based porous support layer is formed by physically or chemically bonding a plurality of polymer skeletons 1, and a conductive layer 2 is provided on at least one polymer skeleton 1.
Fig. 1 shows a schematic structural diagram of a polymer-based porous support layer. The polymer skeleton 1 is made of polymer materials, the polymer skeleton 1 is combined in a physical and/or chemical mode to form a polymer-based porous supporting layer, and the shape of the polymer-based porous supporting layer can be cylindrical, strip-shaped, sheet-shaped or other irregular shapes. The high molecular material comprises one or more of polyolefins, polyacetylenes, polyesters, polyamides, polyimides, polyethers, polyols, polysulfones, polysulfides, siloxane polymers, polysaccharide polymers, amino acid polymers, aromatic ring polymers, aromatic heterocyclic polymers, epoxy resins, phenolic resins, derivatives of the above materials, crosslinked products of the above materials and copolymers of the above materials.
Specifically, the polymer material may include Polyethylene (PE), polyvinyl chloride (PVC), polyvinyl alcohol (PVA), Polystyrene (PS), polyvinylidene fluoride (PVDF), Polytetrafluoroethylene (PTFE), polyacetylene, polypropylene (PP), polycaprolactam (PA6), polyhexamethylene adipamide (PA66), polyparaphenylene terephthalamide (PPTA), polyethylene terephthalamide (PET), polybutylene terephthalate (PBT), poly 4-hydroxybenzoic acid, poly 2-hydroxy-6-naphthoic acid, polyethylene naphthalate (PEN), Polycarbonate (PC), Polyoxymethylene (POM), polyphenylene oxide (PPO), Polyphenylene Sulfide (PPs), polyethylene glycol (PEG), Polyaniline (PAN), polypyrrole (PPy), Polythiophene (PT), polystyrene, sodium Polystyrene Sulfonate (PSs), cellulose, starch, acrylonitrile-butadiene-styrene copolymer (ABS), One or more of derivatives of the above materials, crosslinked products of the above materials, and copolymers of the above materials.
Preferably, the polymer material comprises one or more of poly (p-phenylene terephthalamide) (PPTA), poly (4-hydroxybenzoic acid), poly (2-hydroxy-6-naphthoic acid), Polyimide (PI), and polyethylene terephthalate (PET).
Referring to fig. 2, a schematic diagram of the connection between the polymer skeleton 1 and the conductive layer 2 is shown, wherein the conductive layer 2 is disposed on the polymer skeleton 1. The polymer skeleton 1 has any shape, and the cross section can be round, oval, rectangle, trapezoid or other irregular shapes. The form of the polymer skeleton 1 is also arbitrary, and may be a cylinder, a strip, a sheet or other irregular shape, and the preparation method used for the polymer skeleton 1 may be a melt-blowing method, an electrostatic spinning method or the like.
The conductive layer 2 may include one or more of a metal material, a carbon-based conductive material, and a polymer conductive material. Wherein, the metal material comprises one or more of aluminum, aluminum alloy, copper alloy, nickel alloy, titanium alloy, silver and silver alloy, for example, comprises one or more of aluminum, copper, nickel, titanium, silver, copper-nickel alloy and aluminum. The carbon-based conductive material comprises one or more of graphite, superconducting carbon, acetylene black, carbon black, Ketjen black, carbon nanotubes, carbon dots and carbon nanofibers. The high molecular conductive material comprises one or more of sulfur nitride, aromatic ring conjugated polymer, aliphatic conjugated polymer and aromatic heterocyclic conjugated polymer. For example, the polymeric conductive material may include one or more of polyacetylene, polyphenylene, polyaniline, polypyrrole, polypyridine, polythiophene. In addition, the delocalization of the electrons of the high-molecular conductive material can be increased through doping modification, so that the conductivity of the high-molecular conductive material is improved.
When the conductive layer 2 is made of a metal material, it may be formed on the polymer skeleton 1 by at least one of vapor deposition, electroless plating, and electroplating. The vapor deposition method and the electroplating method are preferred, and the conductive layer 2 is formed on the polymer skeleton 1 by the vapor deposition method or the electroplating method, so that the conductive layer 2 and the polymer skeleton 1 are combined more firmly. The vapor deposition method is preferably a physical vapor deposition method, and the physical vapor deposition method is preferably at least one of an evaporation method and a sputtering method, wherein the evaporation method is preferably at least one of a vacuum evaporation method, a thermal evaporation method, and an electron beam evaporation method, and the sputtering method is preferably a magnetron sputtering method. The electroplating method is preferably a supercritical electroplating method or an electroless plating method.
As an alternative embodiment, the polymer-based porous support layer further comprises an additive, the additive comprising one or more of a metallic material and an inorganic non-metallic material. The metal material may be one or more of aluminum, aluminum alloy, copper alloy, nickel alloy, titanium alloy, silver, and silver alloy. The inorganic non-metallic material may be one or more of carbon-based material, alumina, silicon carbide, silicon nitride, silicon dioxide, boron nitride, silicate and titanium oxide, and may also be one or more of glass material, ceramic material and composite ceramic material. The carbon-based material can be one or more of graphite, superconducting carbon, acetylene black, carbon dots, ketjen black, carbon nanotubes, carbon nanofibers and graphene. In addition, the additive can also be a carbon-based material coated by a metal material, such as one or more of nickel-coated graphite powder and nickel-coated carbon fiber.
After the composite current collector provided by the embodiment is applied to the lithium ion secondary battery, the positive current collector and/or the negative current collector of the battery core can be the composite current collector, and compared with the traditional metal current collector, the composite current collector has a porous structure, so that the positive active material layer and/or the negative active material layer can enter the pores of the composite current collector, and the load capacity of unit area is improved. If the same load capacity is set on the battery pole piece, compared with the traditional metal current collector, the battery pole piece obtained by adopting the composite current collector provided by the embodiment is thinner, the volume of the battery cell is smaller, and the weight is lighter, so that the quality and the volume energy density of the lithium ion secondary battery can be improved simultaneously, and the energy density of the lithium ion secondary battery is obviously improved. In addition, due to the porous structure of the composite current collector, lithium ions can penetrate through the composite current collector to the other side of the current collector or be embedded in the active material layer in the lithium extraction and insertion process of the lithium ion secondary battery, and the safety of the battery core is improved. Compared with the traditional metal current collector, the composite current collector allows lithium ions and electrolyte to pass through, the contact area among the composite current collector, the active substance layer and the electrolyte is larger, the contact is more sufficient, and the internal resistance of the lithium ion secondary battery is smaller, so that the dynamic performance of the lithium ion secondary battery is improved, and the safety, the electrochemical performance and the low-temperature performance of the lithium ion secondary battery are improved. Therefore, the composite current collector provided by the embodiment can remarkably improve the safety, energy density, low-temperature performance and stability of the lithium ion secondary battery.
In this example, the porosity of the polymer-based porous support layer is represented by the volume of gas passing through the composite current collector per unit area vertically per unit time under a pressure difference of 125Pa, and the porosity ranges from 1cc/cm2/sec-1000cc/cm2Sec, preferably, the porosity is 10cc/cm2/sec-500cc/cm2In the/sec range, more preferably, the porosity is 30cc/cm2/sec-300cc/cm2In the/sec range. The porosity of the polymer-based porous support layer is 0.1-99.9%, preferably 20-80%, more preferably 30-60%, and the pore diameter is in the range of 0.01-50 μm.
The porosity of a high molecular weight, porous support layer is affected by: the thickness H1 of the polymer-based porous support layer, the thickness D1 of the conductive layer 2, the form of the polymer skeleton 1, the bonding force between the conductive layer 2 and the polymer skeleton 1, and the like. By adjusting one or more of the foregoing factors, the porosity and pore size distribution of the high molecular weight-based porous support layer can be adjusted. The thickness H1 of the macromolecule-based porous supporting layer is in the range of 1 μm-100 μm, preferably the thickness H1 is in the range of 10 μm-50 μm, more preferably the thickness H1 is in the range of 15 μm-30 μm. The thickness D1 of the conductive layer 2 is in the range of 1nm to 10000nm, preferably the thickness D1 is in the range of 200nm to 2000nm, more preferably the thickness D1 is in the range of 300nm to 1000 nm.
As an optional implementation mode, the conducting layer 2 is disposed on the polymer skeleton 1 in a surrounding manner, and is in 360-degree contact with the polymer skeleton 1, the contact area is large, and the two are tightly combined, so that the polymer skeleton 1 can effectively support the conducting layer 2, and meanwhile, the conducting layer 2 can further improve the overall strength of the composite current collector. Therefore, compared with the traditional metal current collectors such as aluminum foil and copper foil, the composite current collector has large porosity, the thickness of the conductive layer 2 can be obviously reduced and is not easy to break, the thickness of the conductive layer 2 is obviously reduced, the density of the high-molecular porous supporting layer formed by the high-molecular framework 1 is obviously reduced, and the weight of the current collector can be obviously reduced. Meanwhile, the porous structure of the composite current collector enables active substances to enter pores of the composite current collector, the thickness of a pole piece adopting the composite current collector is smaller under the same load condition, or more active substances can be arranged on the unit area of the composite current collector, the composite current collector structure is beneficial to reducing the weight of the battery core and the lithium ion secondary battery, and meanwhile, the size of the battery core and the lithium ion secondary battery is reduced, so that the quality and the volume energy density of the lithium ion secondary battery are improved.
In addition, the porous structure of the composite current collector enables an active substance layer to enter the pores of the composite current collector and to be in full contact with the composite current collector, the pores of the composite current collector simultaneously ensure that lithium ions can pass through the current collector, and the conductive layer 2 ensures that the composite current collector has good conductive performance. The polymer framework 1 and the conducting layer 2 arranged on the polymer framework are tightly combined, so that the composite current collector is not easy to peel off and break the conducting layer 2 in the processing and using processes, and the service life of the battery core and the lithium ion secondary battery is prolonged.
The composite current collector is of a porous structure, when the lithium ion secondary battery is subjected to mechanical damage and is subjected to abnormal conditions such as piercing, burrs are not generated on the conducting layer 2 basically, and therefore the risk of short circuit caused by contact of metal burrs and a counter electrode can be reduced.
As an alternative embodiment, the strength of the polymer-based porous support layer is 1MPa to 1500MPa, and preferably, the strength of the polymer-based porous support layer is 30MPa to 500MPa, so that the polymer-based porous support layer has good tensile strength and dimensional stability, and further, the composite current collector does not undergo excessive deformation and elongation during the processing. In addition, because the deformation amount of the polymer framework 1 is small, the conducting layer 2 and the polymer framework 1 can still be tightly combined, and the mechanical stability and the working stability of the composite current collector are improved.
In order to effectively protect the conductive layer 2 disposed on the polymer skeleton, the composite current collector of this embodiment further includes a first protection layer 3, and the first protection layer 3 is disposed between the polymer skeleton 1 and the conductive layer 2. And/or, the composite current collector further comprises a second protective layer 4, and the second protective layer 4 is arranged above the conductive layer 2. The first protective layer 3 and the second protective layer 4 are used for protecting the conductive layer 2, so that the conductive layer 2 is prevented from being damaged by chemical corrosion or mechanical damage, the composite current collector is ensured to have higher working stability and service life, and the lithium ion secondary battery has higher safety and electrochemical performance. In addition, the first protective layer 3 and the second protective layer 4 can also increase the strength of the composite current collector.
As some examples, referring to fig. 3, the composite current collector includes a polymer skeleton 1, a conductive layer 2, and a first protective layer 3 disposed between the polymer skeleton 1 and the conductive layer 2. Referring to fig. 4, the composite current collector includes a polymer skeleton 1, a conductive layer 2, and a second protective layer 4 disposed on the conductive layer 2. Referring to fig. 5, the composite current collector includes a polymer skeleton 1, a conductive layer 2, a first protection layer 3 disposed between the polymer skeleton 1 and the conductive layer 2, and a second protection layer 4 disposed on the conductive layer 2, and the conductive layer 2 is protected more sufficiently by the first protection layer 3 and the second protection layer 4, so that the composite current collector has higher comprehensive performance.
The first protective layer 3 and the second protective layer 4 may each include one or more of a metal, a metal oxide, and conductive carbon. Specifically, the metal may be one or more of nickel, chromium, a nickel-based alloy, and a copper-based alloy. The nickel-based alloy is an alloy formed by adding one or more other elements into a nickel-based matrix, preferably a nickel-chromium alloy, wherein the nickel-chromium alloy is an alloy formed by metal nickel and metal chromium, and the weight ratio of nickel to cadmium in the nickel-chromium alloy can be 1: 99-99: 1, for example the weight ratio may be 9: 1. the copper-based alloy is an alloy formed by adding one or more other elements into copper serving as a matrix, and is preferably a copper-nickel alloy, wherein the weight ratio of nickel to copper in the copper-nickel alloy is 1: 99-99: 1, for example the weight ratio may be 9: 1. the metal oxide may be one or more of alumina, chromia, cobalt oxide and nickel oxide. The conductive carbon may be one or more of graphite, superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, carbon nanofibers, and graphene.
The first protective layer 3 has a thickness of 1nm to 1000nm, preferably, 10nm to 300nm, and the second protective layer 4 has a thickness of 1nm to 1000nm, preferably, 10nm to 300 nm. The thicknesses of the first protective layer 3 and the second protective layer 4 are within an appropriate range, and the energy density of the lithium ion secondary battery can be improved.
It is understood that the materials of the first protective layer 3 and the second protective layer 4 may be the same or different, and the thicknesses of the first protective layer 3 and the second protective layer 4 may also be the same or different.
The second protective layer 4 is preferably at least one of a metal protective layer or a metal oxide protective layer. The protective layer made of a metal material is a metal protective layer, and the protective layer made of a metal oxide material is a metal oxide protective layer. The metal oxide protective layer has the advantages of high mechanical strength, strong corrosion resistance and large specific surface area, can better protect the conductive layer 2, avoid the damage such as chemical corrosion or mechanical damage, and the like, and can improve the interface between the composite current collector and the active material layer, improve the binding force between the composite current collector and the active material layer, and further improve the performance of the lithium ion secondary battery.
In the present embodiment, the thickness D1 of the conductive layer 2 can be measured by an apparatus and a method known in the art, such as a micrometer, a thickness meter, a scanning electron microscope, a transmission electron microscope, and the like. The method for measuring the thickness and the porosity of the macromolecular porous supporting layer can select a nitrogen adsorption desorption method, a mercury pressing method, an immersion method, a mass density method, a gas expansion replacement method and the like according to the structural difference of the macromolecular porous supporting layer. If the macromolecule based porous supporting layer adopts non-woven fabric, the thickness and porosity of the non-woven fabric can be measured according to the relevant standard of GB/T24218.
Example 2:
this example is used to provide a battery electrode sheet, which includes the composite current collector described in example 1 and an active material layer disposed on the surface and/or in the pores of the composite current collector.
The battery pole piece of the embodiment can be a positive pole piece or a negative pole piece, and is used in a lithium ion secondary battery.
When the battery pole piece is a positive pole piece, the positive pole piece comprises a positive current collector and a positive active substance layer arranged on the surface of the positive current collector and/or in the pores of the positive current collector, and the positive current collector is a composite current collector. Specifically, the positive electrode current collector has two surfaces opposite to each other in the thickness direction thereof, and the positive electrode active material layer may be provided on at least one surface of the positive electrode current collector and/or in the pores of the positive electrode current collector.
The positive electrode active material layer includes a positive electrode active material. The positive active material comprises one or more of positive active materials capable of reversible deintercalation and intercalation of lithium ions. The kind of the positive active material is not limited in this embodiment, and the positive active material may be one or more of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt aluminum oxide, vanadium lithium phosphate, cobalt lithium phosphate, manganese lithium phosphate, lithium iron manganese phosphate, lithium iron lithium silicate, lithium vanadium silicate, lithium cobalt silicate, lithium manganese silicate, and lithium titanate. Such as LiMn2O4、LiNiO2、LiCoO2、LiNi1-yCoyO2(0<y<1)、LiNixCoyAl1-x-yO2(0<x<1,0<y<1,0<x+y<1)、LiMn1-a-bNiaCobO2(0<a<1,0<b<1,0<a+b<1)、LiCoPO4、LiMnPO4、LiFePO4、LiMn1-mFemO4(0<z<1) And Li3V2(PO4)3One or more of (a).
The positive electrode active material layer may further include a binder, and the present embodiment does not limit the kind of the binder. The binder may include one or more of Styrene Butadiene Rubber (SBR), polyvinylidene fluoride (PVDF), Polytetrafluoroethylene (PTFE), ethylene-vinyl acetate copolymer (EVA), sodium carboxymethyl cellulose (CMC-Na), aqueous acrylic resin, polyvinyl alcohol (PVA), and polyvinyl butyral (PVB).
The positive electrode active material layer may further include a conductive agent, and the present embodiment is not limited to the kind of the conductive agent. The conductive agent may include one or more of graphite, superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, carbon nanofibers, and graphene.
The preparation method of the positive pole piece can adopt a coating method. Dispersing a positive electrode active substance, a conductive agent and a binder in a solvent, wherein the solvent can be N-methylpyrrolidone (NMP), forming uniform positive electrode slurry, coating the positive electrode slurry on a positive electrode current collector, and drying to obtain the positive electrode piece.
When the battery pole piece is a negative pole piece, the negative pole piece comprises a negative pole current collector and a negative pole active substance layer arranged on the surface of the negative pole current collector and in the pores of the negative pole current collector, and at the moment, the negative pole current collector is a composite current collector. The negative electrode current collector has two surfaces corresponding in a thickness direction thereof, and the negative electrode active material layer may be disposed on at least one surface of the negative electrode current collector and/or in pores of the negative electrode current collector.
The anode active material layer includes an anode active material. The negative electrode active material is a negative electrode active material capable of lithium ion intercalation and deintercalation, and the present embodiment is not limited to the kind of the negative electrode active material. The negative electrode active material may be artificial graphite, natural graphite, hard carbon, soft carbon, mesocarbon microbeads (MCMB), silicon-carbon composite, metallic lithium, SiO, lithium titanate of spinel structure, Li-Sn alloy, Li-Sn-O alloy, Sn, SnO2And Li-Al alloy. Preferably, the negative active material includes artificial graphite, natural graphite, hard carbon, soft carbon, mesocarbon microbeads (MCMB), silicon, a silicon-carbon composite, and SiO.
The negative electrode active material layer may further include a conductive agent, and the present embodiment is not limited to the kind of the conductive agent. The conductive agent may include one or more of graphite, superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, carbon nanofibers, and graphene.
The anode active material layer may further include a binder, and the present embodiment does not limit the kind of the binder. The binder may include one or more of Styrene Butadiene Rubber (SBR), polyvinylidene fluoride (PVDF), Polytetrafluoroethylene (PTFE), ethylene-vinyl acetate copolymer (EVA), sodium carboxymethyl cellulose (CMC-Na), aqueous acrylic resin, polyvinyl alcohol (PVA), and polyvinyl butyral (PVB).
The preparation method of the negative pole piece can select a coating method. Dispersing a negative electrode active material, a conductive agent and a binder in a solvent, wherein the solvent can be deionized water to form uniform negative electrode slurry, coating the negative electrode slurry on a negative electrode current collector, and drying to obtain a negative electrode plate.
Example 3:
the embodiment is used for providing a battery cell, the battery cell includes a positive electrode plate, an isolation film and a negative electrode plate, and the positive electrode plate, the isolation film and the negative electrode plate are stacked or wound. Specifically, the battery cell may be formed by stacking or winding a positive electrode plate, an isolation film, and a negative electrode plate, wherein the isolation film is located between the positive electrode plate and the negative electrode plate to perform an isolation function.
The positive pole piece comprises a positive current collector and a positive active substance layer arranged on the positive current collector. The negative pole piece comprises a negative pole current collector and a negative pole active substance layer arranged on the negative pole current collector. Lithium ions are deintercalated between the positive electrode active material and the negative electrode active material, and thereby charge and discharge of the lithium ion secondary battery are realized. The positive electrode active material layer and the negative electrode active material layer described in example 2 can be used as the positive electrode active material layer and the negative electrode active material layer.
The positive current collector and/or the negative current collector are/is the composite current collector described in example 1, that is, if the negative current collector is a metal current collector, the positive current collector is the composite current collector described in example 1. If the negative electrode current collector is the composite current collector described in embodiment 1, the positive electrode current collector may be the composite current collector described in embodiment 1, or may be a metal current collector, such as an aluminum foil. When the positive current collector is a composite current collector, the composite current collector is a first composite current collector, and the positive active material layer is arranged on the surface and/or in the pores of the first composite current collector. When the negative current collector is a composite current collector, the composite current collector is referred to as a second composite current collector, and the negative active material layer is arranged on the surface and/or in the pores of the second composite current collector.
When the composite current collector is used as a positive electrode current collector, the conductive layer 2 preferably includes aluminum or an aluminum alloy. When the composite current collector is used as a negative electrode current collector, the conductive layer 2 is preferably copper or a copper alloy.
When the composite current collector is used as a positive electrode current collector, the second protective layer 4 is preferably a metal oxide protective layer, such as aluminum oxide, nickel oxide, chromium oxide, or the like. The metal oxide protective layer has the advantages of high hardness, high mechanical strength, large specific surface area, better corrosion resistance and the like, and can better protect the conductive layer 2. When the composite current collector is used as the negative electrode current collector, the second protective layer 4 is preferably a metal protective layer. The metal protective layer can improve the conductivity of the composite current collector, thereby reducing the polarization of the lithium ion secondary battery, reducing the risk of lithium precipitation of the negative electrode, and improving the cycle performance and the safety performance of the lithium ion secondary battery.
As an alternative embodiment, the double-sided loading of the positive electrode active material layer is 180g/m2-600g/m2Preferably 200g/m2-400g/m2More preferably 220g/m2-300g/m2. The double-sided loading of the positive active material layer is in the range, so that the positive electrode can be ensured to have good dynamic performance, and the electrochemical performance of the lithium ion secondary battery is improved. The double-sided loading amount of the negative electrode active material layer was 50g/m2-300g/m2Preferably 60g/m2-240g/m2More preferably 70g/m2-180g/m2. The double-sided loading capacity of the negative electrode active material layer is within the range, so that the negative electrode has good dynamic performance, the safety of the battery cell is improved, and the electrochemical performance of the lithium ion secondary battery is improved.
In this embodiment, the kind of the isolation film is not limited, and any isolation film with a porous structure having good chemical stability and mechanical stability, such as one or more of polyethylene, polypropylene, polyvinylidene fluoride, cellulose, non-woven fabric, and glass fiber, may be used. The separator may be a single-layer film or a multilayer composite film. When the barrier film is a multilayer composite film, the materials of the layers may be the same or different. The separator may also be a composite separator, for example, a composite separator in which the surface of an organic separator is provided with an inorganic coating.
The porosity of the separator is 25% to 55%, preferably 30% to 50%. Thus, the dynamic performance and low-temperature performance of the lithium ion secondary battery can be further improved, and the energy density of the lithium ion secondary battery can be improved.
Example 4:
this example is intended to provide a lithium ion secondary battery comprising one or more cells as described in example 3 and an electrolyte, the cells being located within the electrolyte.
The electrolyte solution includes an organic solvent and an electrolyte salt dispersed in the organic solvent.
The organic solvent may include Ethylene Carbonate (EC), Propylene Carbonate (PC), pentylene carbonate, 1, 2-butylene glycol carbonate (1, 2-BC), 2, 3-butylene glycol carbonate (2, 3-BC), Ethyl Methyl Carbonate (EMC), dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), Methyl Propyl Carbonate (MPC), Ethyl Propyl Carbonate (EPC), Butylene Carbonate (BC), fluoroethylene carbonate (FEC), Methyl Formate (MF), ethyl formate (EM), Methyl Acetate (MA), Ethyl Acetate (EA), Propyl Acetate (PA), Methyl Propionate (MP), Ethyl Propionate (EP), Propyl Propionate (PP), propyl butyrate (MB), Ethyl Butyrate (EB), 1, 4-butyrolactone (GBL), Sulfolane (SF), dimethylsulfone (MSM), One or more of methylethylsulfone (EMS) and diethylsulfone (ESE). Preferably, the organic solvent comprises a mixed solvent of cyclic carbonate and chain carbonate, and the organic solvent is favorable for preparing the electrolyte with good comprehensive properties of viscosity and conductivity. The conductivity of the electrolyte at 25 ℃ is preferably 6mS/cm-13mS/cm, so that the electrolyte has good ion conductivity and thermal stability, and the battery has good low-temperature performance, normal-temperature cycle performance and high-temperature cycle performance.
The electrolyte salt may include one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bis (fluorosulfonylimide) (LiFSI), lithium bis (trifluoromethanesulfonimide) (LiTFSI) trifluoromethanesulfonate (LiTFS), lithium difluoroborate (lidfo), lithium dioxalate borate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorobis (liddrop) and lithium tetrafluoro-oxalate phosphate (litfo).
The electrolyte can also comprise additives, wherein the additives can comprise a negative electrode film forming additive, a positive electrode film forming additive, an additive for improving the overcharge performance of the battery, an additive for improving the high-temperature performance of the battery, an additive for improving the low-temperature performance of the battery and the like.
As an alternative embodiment, the lithium ion secondary battery may further include an outer package for enclosing the positive electrode tab, the separator, the negative electrode tab, and the electrolyte. The positive pole piece, the isolating membrane and the negative pole piece can form a laminated structure battery cell or a winding structure battery cell in a laminating or winding mode, the battery cell is soaked in the electrolyte, and the battery cell and the electrolyte are packaged in the outer package together. The number of the battery cores in the battery can be one or more, and the number of the battery cores can be adjusted according to requirements. The outer package may be a soft bag, for example a pouch-type soft bag. The soft package material can be plastic, and for example, the soft package material can include one or more of polypropylene PP, polybutylene terephthalate PBT, polybutylene succinate and the like. The outer package of the battery may also be a hard case, such as an aluminum case, a steel case, or the like.
It should be noted that the shape of the lithium ion secondary battery is not limited in this embodiment, and may be, for example, a cylindrical shape, a square shape, or any other shape.
In order to make it clear to those skilled in the art that the lithium ion secondary battery used in the present embodiment has good performance, a detailed description is given of a specific test procedure and test data.
Firstly, the preparation method of each device of the lithium ion secondary battery is discussed:
preparation of conventional positive pole piece
The anode material (lithium iron phosphate, LFP for short; or LiNi)1/3Co1/3Mn1/3O2NCM111 for short), PVDF as a binder and acetylene black as a conductive agent according to a mass ratio of 95: 2.5: 2.5, adding the mixture into solvent NMP (N-methyl pyrrolidone), stirring the mixture under the action of a vacuum stirrer until the mixture is uniform and stable to obtain positive electrode slurry, uniformly coating the positive electrode slurry on a positive electrode current collector (aluminum foil), and drying, cold-pressing and cutting the positive electrode slurry to obtain a conventional positive electrode plate, wherein the compaction density of the conventional positive electrode plate is 2.4g/cm3The positive electrode active material supporting amount (double-sided) was L1.
Preparation of positive pole piece
Different from the conventional positive pole piece, the positive current collector is a composite current collector, the composite current collector is prepared by adopting a vacuum evaporation method, and the preparation method of the composite current collector comprises the following steps: selecting a high-molecular porous supporting layer with a preset porosity, carrying out surface cleaning treatment, placing the high-molecular porous supporting layer subjected to the surface cleaning treatment in a vacuum plating chamber, melting and evaporating high-purity aluminum wires in a metal evaporation chamber at a high temperature of 1200-2000 ℃, and depositing the evaporated metal on a high-molecular framework 1 of the high-molecular porous supporting layer through a cooling system in the vacuum plating chamber to form a conducting layer 2.
Preparation of conventional negative pole piece
Mixing a negative electrode active material (hard carbon, graphite), a conductive agent acetylene black, a thickening agent CMC-Na and a binder SBR according to a mass ratio of 95.5: 2: 1: 1.5, adding solvent deionized water, stirring to be uniform and stable under the action of a vacuum stirrer to obtain negative electrode slurry, uniformly coating the negative electrode slurry on a negative electrode current collector (copper foil), drying, cold pressing and cutting to obtain a conventional negative electrode plate, wherein the compacted density of hard carbon of the conventional negative electrode plate is 0.98g/cm3Graphite 1.5g/cm3The negative electrode active material supporting amount (double-sided) was L2.
Preparation of negative pole piece
Different from the conventional negative pole piece, the negative current collector is a composite current collector, the composite current collector is prepared by combining a supercritical electroplating method and a chemical plating method, and the preparation method of the composite current collector comprises the following steps: selecting a polymer-based porous supporting layer with a predetermined porosity, wherein the polymer-based porous supporting layer is at 8-50MPa, 100 ℃ and CO2Performing supercritical cleaning in the environment, adsorbing a catalytic active center (such as Pd) on a macromolecular framework 1, cooling, performing chemical plating on the treated macromolecular porous supporting layer for 1-60min at the pH value of 10-12 and the temperature of 30-60 ℃, and depositing copper on the macromolecular framework 1 to form a conducting layer 2 after the chemical plating.
Preparation of the electrolyte
The organic solvent is a mixed solvent of Ethylene Carbonate (EC), Ethyl Methyl Carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC) and Methyl Propionate (MP). The electrolyte salt is lithium hexafluorophosphate LiPF6. The mass percentage of the electrolyte in the electrolyte is 12.5 wt%.
Preparation of lithium ion secondary battery
And stacking the positive pole piece, the isolating film and the negative pole piece to obtain a battery core, putting the battery core into a packaging shell, injecting electrolyte into the packaging shell, sealing the packaging shell, and performing the procedures of standing, compacting, formation, exhausting, sealing and the like to obtain the lithium ion secondary battery.
Test section
1. Low temperature performance of lithium ion secondary battery
At 25 ℃, the lithium ion secondary battery is discharged to the lower limit of the charge-discharge cut-off voltage by 1C, then is charged to the upper limit of the charge-discharge cut-off voltage by the constant current of 1C, and then is charged to 0.05C by the constant voltage, and the charging capacity is recorded as CC. Then, the ambient temperature of the battery is adjusted to-10 ℃, the battery is discharged by a constant current of 1C until the lower limit of the charge-discharge cut-off voltage is reached, and the discharge capacity is recorded as CD. The ratio of the discharge capacity CD to the charge capacity CC is the discharge capacity retention rate of the lithium ion secondary battery at-10 ℃. Namely, the discharge capacity retention (%) of the lithium ion secondary battery at-10 ℃ is 100% CD/CC.
2. High temperature cycle performance test of lithium ion secondary battery
At 25 ℃, the lithium ion secondary battery is firstly discharged to the lower limit of the charge-discharge cut-off voltage by 1C, then the ambient temperature around the lithium ion secondary battery is raised to 55 ℃, the lithium ion secondary battery is charged to the upper limit of the charge-discharge cut-off voltage by a constant current of 1C, and then the lithium ion secondary battery is charged to 0.05C at a constant voltage. And then discharging at a constant current of 1C to the lower limit of charge-discharge cut-off voltage, which is a charge-discharge cycle, wherein the discharge capacity of the lithium ion secondary battery at the time is the discharge capacity of the lithium ion secondary battery in the first cycle at 55 ℃. The 500-cycle test was carried out in the above manner, and the discharge capacity of the lithium ion secondary battery at 55 ℃ for the 500 th cycle was recorded. The capacity retention (%) of the lithium ion secondary battery after being cycled 500 times at 55 ℃ was 500 cycles of discharge capacity/100% of discharge capacity at the first cycle.
3. Rate discharge performance of lithium ion secondary battery
At 25 ℃, the lithium ion secondary battery is discharged to the lower limit of the charge-discharge cut-off voltage by 1C, then is charged to the upper limit of the charge-discharge cut-off voltage by the constant current of 1C, and then is charged to 0.05C at constant voltage. And then discharging at 1C to the lower limit of charge-discharge cut-off voltage, recording the discharge capacity C1 and the cell temperature T1 at the moment, and then charging at constant current to the upper limit of charge-discharge cut-off voltage and charging at constant voltage to 0.05C. And then discharging at a constant current of 120C multiplying power to lower limit cut-off voltage of 2.2V, and recording the discharge capacity C2 and the cell temperature T2 at the moment, wherein the multiplying power discharge percentage (%) of the cell is C2/C1 x 100%, and the temperature rise percentage (%) of the cell is (T2-T1)/T1 x 100%.
In the above tests 1, 2, and 3, the charge-discharge cutoff voltage of the lithium ion secondary battery using the LFP positive electrode active material was 2.0 to 3.6V, and the charge-discharge cutoff voltage of the lithium ion secondary battery using the NCM111 positive electrode active material was 2.8 to 4.2V. In the above test 3, the lower limit cut-off voltage of the rate capability test discharge was 2.2V.
Test results
1. Function of composite current collector in improving mass energy density of lithium ion battery
1) When the positive current collector is a composite current collector, the function of improving the quality energy density of the lithium ion secondary battery is realized
TABLE 1-1
Figure BDA0002999353880000151
In Table 1-1, LCP is an abbreviation for Liquid Crystal Polymer, i.e., Liquid Crystal Polymer. The positive current collector weight percent refers to the percent of the positive current collector weight per unit area divided by the conventional positive current collector weight per unit area. Compared with the traditional aluminum foil positive current collector, the weight of the positive current collector adopting the composite current collector is reduced to different degrees, so that the mass energy density of the lithium ion secondary battery can be improved.
2) When the negative current collector is a composite current collector, the weight energy density of the lithium ion secondary battery is improved.
Tables 1 to 2
Figure BDA0002999353880000161
In tables 1-2, the weight percent of the negative current collector is the weight of the composite negative current collector per unit area divided by the weight of the conventional negative current collector per unit area. Compared with the traditional copper foil negative current collector, the negative current collector adopting the composite current collector has the advantages that the weight is reduced to different degrees, and therefore the mass energy density of the lithium ion secondary battery can be improved.
2. Influence of porosity of composite current collector on electrochemical performance of lithium ion secondary battery
The porosity of the composite current collector affects the thickness of the electrode plate, and is characterized by the volume of gas per unit area in unit time under a certain pressure difference. The same load capacity and the thickness of the pole piece after cold pressing are influenced by the porosity of the composite current collector, and meanwhile, the thickness of the conducting layer 2 and the state of the pole piece influence the ohmic internal resistance of the pole piece, further influence the direct current internal resistance of the lithium ion secondary battery, and further influence the electrochemical performance of the lithium ion secondary battery.
TABLE 2-1
Figure BDA0002999353880000162
Figure BDA0002999353880000171
Tables 2 to 2
Figure BDA0002999353880000172
In the lithium ion secondary battery of Table 2-2, the amount of L2 supporting the negative electrode active material layer (both sides) was 110g/m2The amount of L1 (both faces) supported by the positive electrode active material layer was 240g/m2Then (c) is performed. As can be seen from table 2-2, the composite current collector can improve the low-temperature performance of the lithium ion secondary battery.
Tables 2 to 3
Figure BDA0002999353880000173
Figure BDA0002999353880000181
In the lithium ion secondary batteries of tables 2 to 3, the amount of L2 supporting the negative electrode active material layer (both sides) was 110g/m2The amount of the positive electrode active material supported (double-sided) L1 was 240g/m2Then (c) is performed. As can be seen from tables 2 to 3, the composite current collector can improve the low-temperature performance of the lithium ion secondary battery, and the hard carbon material has better low-temperature performance than the graphite material.
3. Influence of loading of active material layer of electrode pole piece on low-temperature performance of lithium ion secondary battery
TABLE 3
Figure BDA0002999353880000182
Figure BDA0002999353880000191
In table 3, the positive electrode active material was LFP, and the negative electrode active material was hard carbon. As can be seen from the data in Table 3, the loading amount of the positive electrode active material layer in the present application was 180g/m2-340g/m2In time, the present application has a better effect of improving the low-temperature performance of the lithium ion secondary battery. The loading capacity of the positive active material layer is 200g/m2-300g/m2When the lithium ion secondary battery is used, the low-temperature performance of the lithium ion secondary battery is further improved. The loading amount of the negative electrode active material layer was 60g/m2-200g/m2The application has better effect of improving the low-temperature performance of the lithium ion secondary battery; the loading amount of the negative electrode active material layer was 60g/m2-150g/m2When used, the low-temperature performance of the lithium ion secondary battery can be further improved.
4. Effect of protective layer on electrochemical Performance of lithium ion Secondary Battery
TABLE 4-1
Figure BDA0002999353880000192
In table 4-1, the protective layer is provided on the basis of the positive electrode current collector 2-3.
TABLE 4-2
Figure BDA0002999353880000193
Figure BDA0002999353880000201
In the batteries of Table 4-2, the negative electrode active material layer supporting amounts were all 110g/m2The loading capacity of the positive active material layer is 240g/m2. The data in table 4-2 show that when the positive current collector is a composite current collector, the capacity retention rate of the battery after 1C/1C cycle for 500 weeks at 55 ℃ can be further improved by arranging the protective layer, and the reliability of the battery is better.
Tables 4 to 3
Figure BDA0002999353880000202
In tables 4 to 3, a protective layer is provided on the basis of the negative electrode current collector 2 to 3. In tables 4-3, the nickel-base alloy contained 90% nickel and 10% chromium. In tables 4-3, the double protective layer includes a nickel protective layer 15nm disposed outside the conductive layer 2, and a nickel oxide protective layer 15nm thick disposed outside the second protective layer 4.
Tables 4 to 4
Figure BDA0002999353880000203
Figure BDA0002999353880000211
Tables 4 to 4 lithium ion secondary batteries, the negative electrode active material layer supporting amounts (both sides) were 110g/m2The positive electrode active material layer loading (double faces) was 240g/m2. As can be seen from tables 4 to 4, when the negative electrode current collector is a composite current collector, the provision of the protective layer enables secondary charging of lithium ionsThe capacity retention rate of the cell after 1C/1C circulation for 500 weeks at 55 ℃ is further improved, and the reliability of the cell is better.
5. High temperature performance of lithium ion secondary battery
TABLE 5-1
Figure BDA0002999353880000212
TABLE 5-1 lithium ion Secondary Battery in which the negative electrode active material layer supporting amounts were all 110g/m2The loading capacity of the positive active material layer is 240g/m2. As can be seen from table 5-1, when the positive electrode current collector and/or the negative electrode current collector is replaced with the composite current collector, the rate discharge performance of the lithium ion secondary battery is improved, and the temperature rise is less, so that the rate performance and reliability of the lithium ion secondary battery are improved.
TABLE 5-2
Figure BDA0002999353880000221
TABLE 5-2 lithium ion Secondary Battery in which the negative electrode active material layer supporting amounts were all 110g/m2The loading capacity of the positive active material layer is 240g/m2. As can be seen from table 5-2, when the positive electrode current collector and/or the negative electrode current collector is replaced with the composite current collector, the rate discharge performance of the lithium ion secondary battery is improved, and the temperature rise is less, so that the rate performance and reliability of the lithium ion secondary battery are improved.
The embodiments in the present description are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other.
The principles and embodiments of the present invention have been described herein using specific examples, which are provided only to help understand the method and the core concept of the present invention; meanwhile, for a person skilled in the art, according to the idea of the present invention, the specific embodiments and the application range may be changed. In view of the above, the present disclosure should not be construed as limiting the invention.

Claims (10)

1. A composite current collector is characterized by comprising a high-molecular porous supporting layer and a conductive layer;
the polymer-based porous support layer is formed by combining a plurality of polymer skeletons in a physical or chemical mode; the conducting layer is arranged on at least one of the polymer frameworks.
2. The composite current collector of claim 1, wherein the porosity of the polymer-based porous support layer is 0.1% to 99.9%, 20% to 80%, or 30% to 60%; the strength of the polymer-based porous supporting layer is 1MPa-1500MPa or 30MPa-500 MPa.
3. The composite current collector of claim 1, wherein the conductive layer is circumferentially disposed on the polymer skeleton and is in 360 degree contact with the polymer skeleton.
4. The composite current collector of claim 1, further comprising a first protective layer; the first protective layer is arranged between the polymer framework and the conductive layer; the first protective layer is used for protecting the conductive layer;
and/or, the composite current collector further comprises a second protective layer; the second protective layer is arranged above the conductive layer; the second protective layer is used for protecting the conductive layer.
5. The composite current collector of claim 4, wherein the thickness of the first protective layer is from 1nm to 1000nm or from 10nm to 300 nm;
the thickness of the second protective layer is 1nm-1000nm or 10nm-300 nm.
6. A battery pole piece, characterized in that it comprises a composite current collector according to any one of claims 1 to 5 and an active substance layer;
the active material layer is disposed on a surface and/or within pores of the composite current collector.
7. An electric core is characterized in that the electric core comprises a positive pole piece, a separation film and a negative pole piece; the positive pole piece, the isolating film and the negative pole piece are arranged in a stacked or winding manner;
the positive pole piece comprises a positive current collector and a positive active substance layer arranged on the positive current collector;
the negative pole piece comprises a negative pole current collector and a negative pole active substance layer arranged on the negative pole current collector;
the positive and/or negative current collector is the composite current collector of any one of claims 1-5; when the positive current collector is the composite current collector, the composite current collector is a first composite current collector, and the positive active material layer is arranged on the surface and/or in the pores of the first composite current collector; when the negative current collector is the composite current collector, the composite current collector is a second composite current collector, and the negative active material layer is arranged on the surface and/or in the pores of the second composite current collector.
8. The battery cell of claim 7, wherein the positive electrode active material layer has a double-sided loading of 180g/m2-600g/m2、200g/m2-400g/m2Or 220g/m2-300g/m2(ii) a The double-sided loading capacity of the negative electrode active material layer is 50g/m2-300g/m2、60g/m2-240g/m2Or 70g/m2-180g/m2
9. The cell of claim 7, wherein the separator has a porosity of 25% to 55% or 30% to 50%.
10. A lithium-ion secondary battery, characterized in that it comprises one or more cells according to any of claims 7 to 9 and an electrolyte;
the battery cell is located in the electrolyte.
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CN113594414A (en) * 2021-07-29 2021-11-02 溧阳紫宸新材料科技有限公司 Organic porous skeleton cathode, preparation method thereof and battery
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