CN118156514A - Composite current collector with three-dimensional network structure, pole piece and electrochemical device - Google Patents

Composite current collector with three-dimensional network structure, pole piece and electrochemical device Download PDF

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CN118156514A
CN118156514A CN202410253500.XA CN202410253500A CN118156514A CN 118156514 A CN118156514 A CN 118156514A CN 202410253500 A CN202410253500 A CN 202410253500A CN 118156514 A CN118156514 A CN 118156514A
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current collector
layer
network structure
insulating layer
dimensional network
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梁成都
李博
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Zhejiang Shengyu Technology Co ltd
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Zhejiang Shengyu Technology Co ltd
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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
    • H01M4/64—Carriers or collectors
    • H01M4/66—Selection of materials
    • H01M4/665—Composites
    • H01M4/667—Composites in the form of layers, e.g. coatings
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/64—Carriers or collectors
    • H01M4/70—Carriers or collectors characterised by shape or form
    • H01M4/72—Grids
    • H01M4/74—Meshes or woven material; Expanded metal
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/50—Current conducting connections for cells or batteries
    • H01M50/572—Means for preventing undesired use or discharge
    • H01M50/584—Means for preventing undesired use or discharge for preventing incorrect connections inside or outside the batteries
    • H01M50/59—Means for preventing undesired use or discharge for preventing incorrect connections inside or outside the batteries characterised by the protection means
    • H01M50/593—Spacers; Insulating plates
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Manufacturing & Machinery (AREA)
  • Composite Materials (AREA)
  • Cell Electrode Carriers And Collectors (AREA)

Abstract

The composite current collector comprises a compact conductive layer, wherein the two largest opposite surfaces of the compact conductive layer are respectively provided with an insulating layer, the insulating layer is of a three-dimensional network structure, the three-dimensional network structure comprises through three-dimensional channels, and the composite current collector has higher mechanical property and mechanical property, and simultaneously has good conductivity and lithium dendrite growth inhibition property, so that the preparation rate of the composite current collector, an electrode plate and an electrochemical device and the reliability in the use process can be improved, the electrochemical device has higher electrochemical property and higher weight energy density, and the preparation method is simple and efficient.

Description

Composite current collector with three-dimensional network structure, pole piece and electrochemical device
Technical Field
The invention relates to the field of electrochemical current collectors, in particular to a three-dimensional network structured composite current collector, a pole piece and an electrochemical device.
Background
Copper foil and aluminum foil are common current collectors of lithium ion batteries, wherein the copper foil is used as a negative current collector, and the aluminum foil is used as a positive current collector, so that the lithium ion battery has the advantages of soft texture, difficult brittle fracture during battery core preparation by winding or lamination, high electronic conduction speed, stable chemical property and the like, is low in price, and is beneficial to popularization and application of the lithium ion battery.
In general, the lighter the current collector, the more advantageous it is to increase the energy density of the battery. The current copper foil and aluminum foil current collectors have thicknesses of 4-6 μm and 8-10 μm, which are the very level of manufacturing lithium ion batteries. Further thinning the thickness of the copper foil and the aluminum foil to reduce the quality of the current collector can lead to increased brittleness of the copper foil and the aluminum foil, and the current collector is easy to break and cannot meet the mechanical performance requirement of the current collector. And the traditional copper foil and aluminum foil current collector have the defects of uneven lithium ion deposition, lithium dendrite formation, volume expansion effect, battery cycle performance reduction and serious safety problems due to small specific surface area, large current density and the like.
Compared with traditional current collectors such as aluminum foil and copper foil, the three-dimensional net-shaped current collector can reduce the volume expansion effect caused by lithium deposition through a larger specific surface area and a three-dimensional net structure, and the electric field distribution is uniform, so that the generation of lithium dendrites is inhibited, and the three-dimensional net-shaped current collector has better toughness and strength compared with a plane current collector. Common three-dimensional net-shaped current collectors such as foam nickel, foam copper, three-dimensional carbon frameworks and the like, wherein the frameworks of the three-dimensional net-shaped structures are electronic conduction channels. However, the preparation process of these three-dimensional network current collectors is complicated, and the lithium deposition area is mainly on top of the three-dimensional network structure, so that it is difficult to fully utilize the skeleton of the three-dimensional network structure.
Chinese patent application CN111987320a discloses a current collector with a three-dimensional network structure, comprising: the high-molecular polymer current collector comprises a high-molecular polymer current collector matrix and a metal conductive layer, wherein the high-molecular polymer current collector matrix is provided with a three-dimensional network pore structure, and the metal conductive layer is formed by a metal material deposited on a skeleton of the high-molecular polymer three-dimensional network structure in a physical deposition mode. The current collector replaces the existing metal network structures such as foam copper and the like with the insulating high polymer three-dimensional network structure, and the contact area and binding force of the whole current collector and the loaded active material are improved by depositing the metal conductive layer on the high polymer three-dimensional network structure, and meanwhile, the current density is uniform, and polarization is reduced. However, the thickness of the polymer substrate in the three-dimensional network current collector reaches 30-200 mu m, the overall thickness of the current collector is thicker, the volume energy density is affected, and the metal material is difficult to ensure to be fully and uniformly deposited on the three-dimensional network skeleton.
Chinese patent CN115440987a discloses a current collector comprising a first polymer layer, a metal foil layer and a second polymer layer laminated in this order, the current collector having a plurality of through holes penetrating the current collector at opposite surfaces in the lamination direction. The current collector can be effectively infiltrated by the electrolyte, so that the electrochemical consistency of the inside of the current collector is improved, meanwhile, the generation of lithium dendrites can be inhibited to a certain extent, dead lithium is avoided, and the electrochemical performance and safety are improved. According to the technical scheme, through holes are formed in the polymer layer metal foil layer, lithium ions can be effectively deposited in the inner space, lithium dendrites are prevented from being generated, but the mechanical property of the metal layer is reduced due to the through holes, the resistance is greatly increased due to the discontinuity of the conductive structure, the scattering and loss of current in the conductive layer are increased, in addition, the through holes are formed by integrally penetrating three layers, the conductive contact surface of the metal layer is only the cross section of the through holes, the contact resistance is large, and the conductive property of the current collector is greatly reduced. On the other hand, although each through-hole can increase the internal space, these through-holes are not three-dimensionally penetrating, have uniform directivity and are independent of each other, resulting in that lithium dendrites inevitably grow toward the separator after a long period of time.
Therefore, it is necessary to further develop a novel current collector which has high energy density, equivalent mechanical strength and lithium dendrite suppression effect, and good battery cycle performance.
Disclosure of Invention
The invention overcomes the defects in the prior art, provides the composite current collector with a three-dimensional network structure, has higher mechanical property and mechanical property, and simultaneously has good conductivity and lithium dendrite growth inhibition property, so that the preparation rate of the composite current collector, the electrode plate and the electrochemical device and the reliability in the use process can be improved, the electrochemical device has higher electrochemical property and higher weight energy density, and the preparation method has simple and efficient process.
The composite current collector with the three-dimensional network structure comprises a compact conductive layer, wherein insulating layers are arranged on two largest opposite surfaces of the compact conductive layer, the insulating layers are provided with the three-dimensional network structure, and the three-dimensional network structure comprises through three-dimensional channels. In the scheme of the invention, the insulating layer has a three-dimensional network structure, such as a honeycomb or bird nest shape and the like, and the three-dimensional network structure comprises a plurality of pores separated by framework materials of the insulating layer, namely three-dimensional channels distributed in the insulating layer, and the pores can be mutually communicated to form a network space formed inside the insulating layer, so that the wettability of the insulating layer is very good, and the compact conducting layer is complete, thereby ensuring good current collecting and conducting properties. On the other hand, since the space network structure of the insulating layer comprises a three-dimensional distributed and mutually communicated structure, the distribution of crystal nuclei is greatly dispersed, and the lithium crystallization phenomenon is inhibited, namely, even if the pole piece locally appears crystallization, the pole piece grows in the internal structure body of the space network, and due to the three-dimensional property of the space, dendrites of the pole piece are also three-dimensional pointing, so that the proportion of lithium dendrites growing towards the direction of the diaphragm is greatly reduced.
Further, the three-dimensional network structure further comprises non-through pore channels, the total porosity of the insulating layer is K 0, the porosity corresponding to the through three-dimensional channel is K 1,K0 and is 0.6-0.9, and K 1/K0 is more than or equal to 0.7 and less than or equal to 0.85.
The prior three-dimensional network current collector basically characterizes the influence of pores by total porosity, but the inventor finds that a single total porosity index has no obvious correlation with the current collector performance, and the ratio of the through three-dimensional pore canal to the total porosity plays a key role in the current collector performance in the scheme of the application, and the inventor considers that the possible reasons are as follows: the through three-dimensional pore canal is an open pore canal which is mutually communicated and is an effective pore canal of a three-dimensional network structure, but the larger the porosity ratio of the through three-dimensional channel is, the strength of the insulating layer is affected and is further related to the circulation performance of the current collector, and the like, so that the non-through pore canal with proper ratio is required to exist on the premise of meeting certain total porosity, and the non-through pore canal such as a blind hole, a closed dead hole and the like plays a role in assisting the three-dimensional channel and enhancing the strength of the insulating layer.
Further, the pore diameter r of the three-dimensional network structure is 200-2000nm, preferably 200-1500nm.
Further, the insulating layer is formed by stacking two layers of insulators, and comprises an inner insulating sub-layer which is attached to the compact conducting layer and an outer insulating sub-layer which is far away from the compact conducting layer, wherein the aperture of the inner insulating sub-layer is smaller than that of the outer insulating sub-layer, and the ratio of the total aperture K 0 of the inner insulating sub-layer to the total aperture K 0 of the outer insulating sub-layer is 1.2-1.5.
Further, the aperture of the three-dimensional network structure of the inner insulator layer is more than or equal to 200 and less than or equal to 800nm, and the aperture of the three-dimensional network structure of the outer insulator layer is more than or equal to 1000 and less than or equal to 1500nm.
The two insulator layers are arranged, the porosity of the inner insulator layer is kept high, the pore diameter of the outer insulator layer is large, the outer insulator layer is easy to be soaked by electrolyte and is more easily and uniformly dispersed after entering the inner insulator layer, the inner insulator layer is more flexible than the outer insulator layer due to the large porosity, the compact conductive layer can be better matched to bend, the bending buffer effect of the outer insulator layer is achieved, meanwhile, the active material is easier to fill in the pores of the outer insulator layer when the active material layer is coated, and then the active material layer can be filled in the pores of the inner insulator layer. If these active materials are directly taken up by the pores of the inner insulator layer, it is apparent that the active materials cannot further sufficiently fill the pores inside thereof due to the relatively smaller and denser pore sizes; and the smaller pore diameter of the inner insulator layer is also beneficial to dispersing and attaching to the lithium deposition on the surface of the compact conducting layer, so that the growth of lithium dendrites is avoided.
Further, the dense conductive layer thickness D1 is 1 μm to 8 μm, preferably 2 μm to 6 μm, preferably 2 μm to 4 μm;
The thickness D2 of the insulating layer is 1 μm to 8. Mu.m, preferably 1 μm to 6. Mu.m, preferably 1 μm to 4. Mu.m.
Further, a framework of the three-dimensional network structure is loaded with a conductive reinforcing material; preferably, the material of the conductive reinforcing material is the same as that of the compact conductive layer.
Further, the dense conductive layer is selected from a metal conductive material or a carbon-based conductive material, wherein the metal conductive material is selected from at least one of aluminum, copper, nickel, titanium, silver, nickel-copper alloy and aluminum-zirconium alloy, and the carbon-based conductive material is selected from at least one of graphite, acetylene black, graphene and carbon nanotubes; the compact conductive layer has the following characteristics: (1) The densified conductive layers such as copper foil, aluminum foil, etc. have little or no voids or interstices, which can effectively reduce electrical resistance and provide a better current conduction path. (2) The densified conductive layer generally has a planar surface, has no pronounced asperities or roughness, helps ensure good contact and connectivity, reduces contact resistance, and provides a uniform current distribution. (3) Densified conductive layers such as copper foil, aluminum foil, etc. are more susceptible to maintaining integrity when the insulating layer is broken than copper plating, aluminum plating, etc. formed by deposition, and thus combine the advantages of conventional metal foil current collectors.
And/or the material of the compact insulating layer is at least one selected from organic polymer insulating materials, inorganic insulating materials and composite materials; preferably, the composite material is composed of an organic polymer insulating material and an inorganic insulating material. In an embodiment of the present application, the material of the insulating layer is selected from an organic polymer insulating material, and may be one of Polyamide (PA), polyethylene terephthalate (PET), polyimide (PI), polyethylene (PE), polypropylene (PP), polystyrene (PS), polyvinyl chloride (PVC), acrylonitrile-butadiene-styrene copolymer (ABS), polybutylene terephthalate (PBT), poly-paraphenylene terephthalamide (PPA), epoxy resin, polyoxymethylene (POM), phenolic resin, polypropylene (PPE), polytetrafluoroethylene (PTFE), silicone rubber, polyvinylidene fluoride (PVDF), polycarbonate (PC), aramid, polydiformylphenylenediamine, cellulose and its derivatives, starch and its derivatives, protein and its derivatives, polyvinyl alcohol and its cross-links, polyethylene glycol and its cross-links, and the like. Because the density of the insulating layer is generally smaller than that of metal and the insulating layer is provided with a certain pore, the mass is lighter, and the current collector can improve the weight energy density of the battery while improving the safety performance of the battery. And the insulating layer can play a good bearing and protecting role on the conductive layer positioned on the surface of the insulating layer, so that the common pole piece fracture phenomenon in the existing current collector is not easy to occur.
The preparation method of the composite current collector comprises the following steps:
Placing a compact conductive layer material such as aluminum or copper material in a roller press, continuously rolling the material into a compact conductive layer with a required thickness in a rolling mode, and then thermally compounding the compact conductive layer material with insulating layers (such as a PP porous film and a PET porous film of a finished product) with the requirements of porosity, aperture and the like on two sides of the compact conductive layer respectively in a dry compounding mode, a wet compounding mode or a solvent-free compounding mode to form a structure with insulating layers on two sides of the compact conductive layer;
or mixing high molecular polymer such as PP, PET, etc. with pore-forming agent such as ammonium bicarbonate, benzoic acid, etc. to obtain high molecular polymer slurry, coating on two sides of the compact conductive layer to form film, and heating to form pores to form insulating layer.
The total porosity K 0 was measured by the conventional mercury porosimetry method. The porosity of the through three-dimensional channel K 1 was tested by the bubble point method: cutting a porous film for forming an insulating layer into a circular sheet shape, soaking and saturating the circular sheet shape in a fluoroether solvent, measuring the mass M1 of the film, then placing the circular sheet into a film fixer for pressurization, blowing out liquid in the porous film, measuring the mass M2 of the film, and obtaining the film pore volume of the porous film according to the mass change (M1-M2) of a porous film sample and the density of the fluoroether solvent, wherein the ratio of the film pore volume to the apparent volume (film thickness: wafer area) of the porous film is the porosity K 1.
In a second aspect, the present application provides a pole piece comprising a current collector as described above and an electrode active material layer formed on the surface of the current collector.
In the embodiment of the application, the electrode active material layer is also filled in the pores of the three-dimensional network structure; the electrode active material layer formed on at least one surface of the current collector is partially or entirely connected to the electrode active material layer filled in the pores. The electrode active material layer may be formed on at least one surface of the current collector. The electrode active material layer is disposed on a surface of the current collector. After the electrode active material layer is dried and compacted, the layer may infiltrate into the inside of the pores.
In an embodiment of the present application, the electrode active material layer is formed on at least one surface of the current collector, and may at least partially fill the pores of the three-dimensional network structure of the current collector. Meanwhile, the electrode active material layer formed on the surface of the current collector and the electrode active material layer filled in the pores are partially or entirely connected to each other. In this way, the bonding between the electrode active material layer and the current collector is stronger, thereby improving the long-term reliability and life of the electrode tab and the battery. In addition, the electrode active material layer has a certain porosity, so that the electrolyte wettability of the pole piece can be enhanced, and the polarization phenomenon of the pole piece can be reduced.
In a third aspect, the present application provides an electrochemical device comprising the pole piece of the second aspect. The electrochemical device provided by the application comprises a negative electrode plate, a diaphragm and a negative electrode plate. Specifically, the electrochemical device may be a wound or laminated battery such as one of a lithium ion secondary battery, a lithium primary battery, a sodium ion battery, and a magnesium ion battery, but is not limited thereto.
The technical scheme of the invention has at least the following beneficial effects:
1. The conductive layer adopted by the technical scheme of the invention has less materials and lighter weight, maintains the equivalent mechanical strength under the condition of further reducing the thickness of the compact conductive layer, and simultaneously reduces the weight of the current collector and the pole piece so as to be beneficial to improving the mass capacity density.
2. The arrangement of the insulating layer structures on the two sides and the integral compact conducting layers such as copper foil and aluminum foil can keep the equivalent mechanical strength-of the current collector.
3. The insulating layer of the technical scheme of the invention has a three-dimensional-network structure, the three-dimensional-network structure comprises a plurality of pores separated by framework materials of the insulating layer, and the pores can be mutually communicated to form a three-dimensional network space formed inside the insulating layer, so that the insulating layer has very good wettability, and the conducting layer is complete, thereby ensuring good current collecting and conducting properties.
4. According to the technical scheme, the space network structure of the insulating layer comprises three-dimensional distributed and mutually communicated channel structures, namely communicated open pores, so that the distribution of crystal nuclei is greatly dispersed, the lithium crystallization phenomenon is restrained, even if the pole piece is crystallized locally, the pole piece can grow in an internal structure body of the space network, and due to the three-dimensional property of the space, dendrites of the pole piece are three-dimensional directional, and the proportion of lithium dendrites growing towards the direction of a diaphragm is greatly reduced.
5. According to the technical scheme, the insulating layer is provided with the honeycomb-shaped or bird nest-shaped or foam-shaped three-dimensional space net-shaped structure, so that the stress of the insulating layer is released conveniently, and the binding force between the insulating layer and the conducting layer is improved.
6. According to the technical scheme, the internal framework of the three-dimensional network structure can be partially or completely provided with the conductive reinforcing material to form a three-dimensional conductive structure, so that electrons have higher conductivity.
Drawings
Fig. 1 is a cross-sectional view of a current collector with a three-dimensional network structure according to the present invention.
Wherein: 1. a dense conductive layer; 2. an insulating layer; 3 three-dimensional network space structure in the insulating layer.
Detailed Description
The invention can be realized by the following specific embodiments:
Example 1 preparation of composite current collector
1.1 Placing an aluminum or copper material in a roll press, continuously rolling the material by means of rolling into a dense conductive layer of the desired thickness: aluminum foil and copper foil;
1.2 taking an organic polymer film (the positive electrode current collector is a porous PET film and the negative electrode current collector is a porous PP film) with a three-dimensional network structure meeting the requirements, and transferring the organic polymer film to two surfaces of an aluminum foil or a copper foil in a conventional dry-type compounding mode of a metal foil and a plastic organic film to obtain the composite current collector.
1.3 Taking the prepared composite current collector in a vacuum thermal evaporation cabin, vacuum thermally plating a conductive reinforcing material on the surface of an insulating layer, and attaching the composite current collector to a framework of the insulating layer, wherein the corresponding material of the positive current collector is aluminum, the corresponding material of the negative current collector is copper, and the evaporation thickness is 100nm.
The prepared current collector is shown in fig. 1, wherein 1 is a compact conductive layer, 2 is an insulating layer, 3 is a three-dimensional network structure in the insulating layer, and specific samples are shown in tables 1 and 2.
The prepared positive electrode current collector and comparative current collector are shown in table 1 below.
TABLE 1 Positive electrode current collector
Comparative example D-1e after thermally compounding a nonporous PET film to an aluminum foil sheet, perforations were formed through both surfaces of a current collector using a laser drilling method.
The prepared negative electrode current collector and comparative current collector are shown in table 2 below.
Table 2 negative electrode current collector
In comparative example D-2e, a pore-forming film was formed by laser drilling to form perforations through the current collector after thermally compounding the nonporous PP film to a copper foil.
Example 2 preparation of pole piece:
Through a conventional battery coating process, coating positive electrode slurry or negative electrode slurry on the surface of a current collector, and drying at 100 ℃ to obtain a positive electrode plate or a negative electrode plate, wherein:
The active material of the positive electrode plate is ternary nickel cobalt manganese lithium slurry NCM523 (NCM 523: PVDF: ketjen black)
Nmp as solvent, solid content 60%) positive active material layer thickness 14 μm, =90:5:5;
the active material of the negative electrode sheet was graphite (graphite: SBR: ultrafine graphite=92:6:4, nmp as solvent, solid content 46%), and the negative electrode active material layer was laminated to a thickness of 14 μm.
Example 3 preparation of a battery:
Through a conventional battery manufacturing process, a positive electrode plate (compaction density: 3.2g/cm 3), a PP/PE/PP diaphragm and a negative electrode plate (compaction density: 1.5g/cm 3) are wound together into a bare cell, then the bare cell is placed into a battery shell, electrolyte (EC: EMC volume ratio: 3:7, liPF6: 1.2 mol/L) is injected, and then the procedures of sealing, formation and the like are carried out, so that a secondary battery is finally obtained, wherein the specific see Table 5.
Performance tests were performed on the current collector and the wound core battery prepared above.
1. Current collector tensile test
And (3) referring to the tensile method test in the standard GB/T228.1-2010, wherein the length of a current collector sample is 200+/-2 mm, the width of the current collector sample is 15+/-0.25 mm, the tensile speed of 50mm/min is set, the distance between clamping heads of a testing machine is 125+/-0.1 mm, the test is stopped when the sample is stretched to fracture, the tensile strength is obtained, the tensile strength multiple strength relative to an aluminum foil or a copper foil is calculated, 5 parallel samples are tested, and the average value is taken as a test result. The test results are shown in tables 3-4.
TABLE 3 Table 3
Numbering device Tensile strength multiple relative to current collector D-1a
Current collector S-1a 1.08
Current collector S-1e 1.13
TABLE 4 Table 4
As can be seen in the table above, the current collector provided by this embodiment is lighter in weight than conventional copper foil and aluminum foil while maintaining tensile properties at least similar to those of the aluminum foil or copper foil.
2. Cycling ability test:
At 45 ℃, the lithium ion secondary battery is charged to 4.2V at a constant current of 1C, then is charged to a current of less than or equal to 0.05C at a constant voltage, and is discharged to 2.5V at a constant current of 1C, wherein the discharge capacity is the discharge capacity of the 1 st cycle, the charge and discharge cycles are repeated, and the capacity retention rate after 1000 cycles is recorded. The test results are shown in Table 5.
3. Pole piece lithium deposition observation
And disassembling the lithium battery after the cyclic test, splitting out a positive plate and a negative plate, observing the surface morphology of the positive plate, wherein the white area is the precipitated lithium, and judging the precipitated lithium degree according to the larger precipitated lithium amount of the white area: the results of the large amount of lithium precipitation, the small amount of lithium precipitation, the slight lithium precipitation, the very slight lithium precipitation, and no lithium precipitation are shown in Table 5.
TABLE 5
From the analysis of the table, the current collector can improve the cycle performance and the high-temperature performance of the battery. Meanwhile, compared with a double-side single-layer insulating layer, the double-side double-layer insulating layer has more excellent performance. However, this is also affected by the connection between the two layers, the synchronization of bending, etc., and it is required that each sub-layer of the insulating layer satisfies a certain condition.
The above-described embodiments are merely preferred embodiments of the present invention, and are not intended to limit the scope of the present invention. All insubstantial changes and modifications made by those skilled in the art based on the teachings herein are intended to be within the scope of the teachings herein as claimed.

Claims (10)

1. The composite current collector with the three-dimensional network structure is characterized by comprising a compact conductive layer, wherein insulating layers are arranged on two largest opposite surfaces of the compact conductive layer, the insulating layers are provided with the three-dimensional network structure, and the three-dimensional network structure comprises through three-dimensional channels.
2. The composite current collector of claim 1 wherein the insulating layer has a total porosity of K 0, and the three-dimensional channel therethrough has a porosity of K 1,K0 of 0.6 to 0.9 and 0.7 to 0. 1/K0 to 0.85.
3. A current collector according to claim 1 or 2, wherein the pore size r of the three-dimensional network structure is 200-2000nm, preferably 200-1500nm.
4. The composite current collector of claim 2, wherein the insulating layer is formed by laminating two layers of insulators, and comprises an inner insulating layer attached to the dense conducting layer and an outer insulating layer far away from the dense conducting layer, the pore diameter of the inner insulating layer is smaller than that of the outer insulating layer, and the ratio of the total porosity K 0 of the inner insulating layer to the outer insulating layer is 1.2-1.5.
5. The composite current collector of claim 4, wherein the pore size of the three-dimensional network structure of the inner insulator layer is 200.ltoreq.r.ltoreq.800 nm, and the pore size of the three-dimensional network structure of the outer insulator layer is 1000.ltoreq.r.ltoreq.1500 nm.
6. Current collector according to claim 1, characterized in that the dense conductive layer thickness D1 is 1 μm-8 μm, preferably 2-6 μm, preferably 2-4 μm;
The thickness D2 of the insulating layer is 1 μm to 8. Mu.m, preferably 1 μm to 6. Mu.m, preferably 1 μm to 4. Mu.m.
7. The composite current collector of claim 1 wherein the skeleton of the three-dimensional network structure is loaded with a conductive reinforcing material;
preferably, the material of the conductive reinforcing material is the same as that of the compact conductive layer.
8. The composite current collector of claim 1 or 7, wherein said dense conductive layer is selected from a metallic conductive material or a carbon-based conductive material; the metal conductive material is at least one of aluminum, copper, nickel, titanium, silver, nickel-copper alloy and aluminum-zirconium alloy, and the carbon-based conductive material is at least one of graphite, acetylene black, graphene and carbon nano tube;
And/or the material of the insulating layer is at least one selected from organic polymer insulating materials, inorganic insulating materials and composite materials; preferably, the composite material is composed of an organic polymer insulating material and an inorganic insulating material.
9. A pole piece comprising a current collector according to any one of claims 1 to 8 and an active material layer formed on the surface of the current collector.
10. An electrochemical device comprising the electrode sheet of claim 9.
CN202410253500.XA 2024-03-06 2024-03-06 Composite current collector with three-dimensional network structure, pole piece and electrochemical device Pending CN118156514A (en)

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