CN117936804A - High-specific-surface current collector, preparation method thereof, electrode plate and battery - Google Patents
High-specific-surface current collector, preparation method thereof, electrode plate and battery Download PDFInfo
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- CN117936804A CN117936804A CN202410015608.5A CN202410015608A CN117936804A CN 117936804 A CN117936804 A CN 117936804A CN 202410015608 A CN202410015608 A CN 202410015608A CN 117936804 A CN117936804 A CN 117936804A
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- 238000002360 preparation method Methods 0.000 title abstract description 14
- 239000011888 foil Substances 0.000 claims abstract description 213
- 229910052751 metal Inorganic materials 0.000 claims abstract description 156
- 239000002184 metal Substances 0.000 claims abstract description 156
- 239000007772 electrode material Substances 0.000 claims abstract description 31
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 20
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims description 66
- 229910052782 aluminium Inorganic materials 0.000 claims description 64
- 238000005554 pickling Methods 0.000 claims description 38
- 238000000034 method Methods 0.000 claims description 34
- 238000010306 acid treatment Methods 0.000 claims description 13
- 230000008569 process Effects 0.000 claims description 13
- 238000004140 cleaning Methods 0.000 claims description 9
- 239000008367 deionised water Substances 0.000 claims description 7
- 229910021641 deionized water Inorganic materials 0.000 claims description 7
- 238000004519 manufacturing process Methods 0.000 claims description 7
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 claims description 6
- 239000011889 copper foil Substances 0.000 claims description 6
- 238000001035 drying Methods 0.000 claims description 6
- 230000001678 irradiating effect Effects 0.000 claims description 6
- 238000002791 soaking Methods 0.000 claims description 5
- 238000009792 diffusion process Methods 0.000 claims description 3
- 238000000608 laser ablation Methods 0.000 claims description 2
- 230000005484 gravity Effects 0.000 claims 1
- 230000000052 comparative effect Effects 0.000 description 13
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 10
- 229910001416 lithium ion Inorganic materials 0.000 description 10
- 239000003575 carbonaceous material Substances 0.000 description 9
- 239000011149 active material Substances 0.000 description 7
- 230000006872 improvement Effects 0.000 description 7
- 239000011248 coating agent Substances 0.000 description 6
- 238000000576 coating method Methods 0.000 description 6
- 230000000694 effects Effects 0.000 description 5
- 230000002035 prolonged effect Effects 0.000 description 5
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 4
- 239000000853 adhesive Substances 0.000 description 4
- 230000001070 adhesive effect Effects 0.000 description 4
- 230000009286 beneficial effect Effects 0.000 description 4
- 238000003486 chemical etching Methods 0.000 description 4
- 229910052744 lithium Inorganic materials 0.000 description 4
- 238000001000 micrograph Methods 0.000 description 4
- 238000000926 separation method Methods 0.000 description 4
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 3
- 239000013543 active substance Substances 0.000 description 3
- 230000005540 biological transmission Effects 0.000 description 3
- 229920001971 elastomer Polymers 0.000 description 3
- 239000000806 elastomer Substances 0.000 description 3
- 239000003792 electrolyte Substances 0.000 description 3
- 239000007773 negative electrode material Substances 0.000 description 3
- 230000010287 polarization Effects 0.000 description 3
- 239000007774 positive electrode material Substances 0.000 description 3
- 238000005096 rolling process Methods 0.000 description 3
- 230000032683 aging Effects 0.000 description 2
- 238000005452 bending Methods 0.000 description 2
- 210000001787 dendrite Anatomy 0.000 description 2
- 238000009826 distribution Methods 0.000 description 2
- 239000003344 environmental pollutant Substances 0.000 description 2
- 239000012535 impurity Substances 0.000 description 2
- 229910052742 iron Inorganic materials 0.000 description 2
- 230000003287 optical effect Effects 0.000 description 2
- 231100000719 pollutant Toxicity 0.000 description 2
- 238000003825 pressing Methods 0.000 description 2
- -1 separators Substances 0.000 description 2
- 238000007493 shaping process Methods 0.000 description 2
- 239000007787 solid Substances 0.000 description 2
- 230000003746 surface roughness Effects 0.000 description 2
- 238000004804 winding Methods 0.000 description 2
- 229910000572 Lithium Nickel Cobalt Manganese Oxide (NCM) Inorganic materials 0.000 description 1
- JLVVSXFLKOJNIY-UHFFFAOYSA-N Magnesium ion Chemical compound [Mg+2] JLVVSXFLKOJNIY-UHFFFAOYSA-N 0.000 description 1
- 239000002033 PVDF binder Substances 0.000 description 1
- QSNQXZYQEIKDPU-UHFFFAOYSA-N [Li].[Fe] Chemical compound [Li].[Fe] QSNQXZYQEIKDPU-UHFFFAOYSA-N 0.000 description 1
- FBDMTTNVIIVBKI-UHFFFAOYSA-N [O-2].[Mn+2].[Co+2].[Ni+2].[Li+] Chemical compound [O-2].[Mn+2].[Co+2].[Ni+2].[Li+] FBDMTTNVIIVBKI-UHFFFAOYSA-N 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 230000006978 adaptation Effects 0.000 description 1
- 229910045601 alloy Inorganic materials 0.000 description 1
- 239000000956 alloy Substances 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 230000015556 catabolic process Effects 0.000 description 1
- 239000010406 cathode material Substances 0.000 description 1
- 210000004027 cell Anatomy 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 230000003749 cleanliness Effects 0.000 description 1
- 230000008602 contraction Effects 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 238000000354 decomposition reaction Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000006731 degradation reaction Methods 0.000 description 1
- 230000003111 delayed effect Effects 0.000 description 1
- 239000006185 dispersion Substances 0.000 description 1
- 239000011267 electrode slurry Substances 0.000 description 1
- 230000008595 infiltration Effects 0.000 description 1
- 238000001764 infiltration Methods 0.000 description 1
- 229910001425 magnesium ion Inorganic materials 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 238000002161 passivation Methods 0.000 description 1
- 239000000843 powder Substances 0.000 description 1
- 238000003860 storage Methods 0.000 description 1
- 230000035882 stress Effects 0.000 description 1
- 238000009736 wetting Methods 0.000 description 1
Classifications
-
- 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
-
- 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
- H01M4/66—Selection of materials
- H01M4/661—Metal or alloys, e.g. alloy coatings
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Materials Engineering (AREA)
- Manufacturing & Machinery (AREA)
- Cell Electrode Carriers And Collectors (AREA)
Abstract
The invention provides a high-ratio-meter current collector, a preparation method thereof, an electrode plate and a battery, wherein the high-ratio-meter current collector comprises a metal foil, the metal foil is provided with a plurality of concave holes, the diameter of each concave hole is less than or equal to 20 mu m, the total area of each concave hole accounts for 25% or less of the total area of the metal foil, and the water drop angle of the metal foil is less than or equal to 5 degrees. The high-specific-surface current collector has high adhesion with the electrode material and low internal resistance.
Description
Technical Field
The invention relates to the technical field of lithium batteries, in particular to a high-specific-surface current collector, a preparation method thereof, an electrode plate and a battery.
Background
Lithium ion batteries generally include: active materials, separators, electrolytes, current collectors, and the like. The negative current collector of the lithium ion battery is generally copper foil, and the positive current collector is generally aluminum foil. Because the rolled surface of a general metal foil is smoother, problems such as poor wettability, non-tight bonding, small bonding strength, small bonding area, difficult adhesion and the like can occur when the active material is coated, so that the interface resistance between the active material and a current collector is high, the active material is easy to fall off, and the coating difficulty is high. The above problems can lead to the performance degradation of the battery, such as serious polarization caused by large interface resistance, and influence on the lithium storage capacity, rate capability, cycle stability and the like of the active material, so that the current requirements for high rate, high energy density and long cycle life are difficult to meet. Therefore, improving the surface state and property of the metal foil strip has important significance for improving the compatibility of the active material and the current collector, improving the bonding strength and increasing the bonding area, and further improving the battery performance.
The prior art patent such as CN111180741A, CN111180741A, CN116742007A discloses a scheme that a layer of carbon material is coated on a metal foil to increase the specific surface area of a current collector. However, the carbon materials widely used at present have the defects of poor conductivity, difficult dispersion, weak bonding strength between the coating and the metal foil, thicker coating and the like.
Disclosure of Invention
The invention aims to solve the technical problems of providing a high-specific-surface current collector which has large adhesion with electrode materials and low internal resistance.
The invention also solves the technical problem of providing a preparation method of the high-specific-surface current collector, which has little influence on the tensile strength and the elongation of the metal foil and can meet the manufacturing process requirements of the electrode plate.
The invention also solves the technical problem of providing an electrode plate with good electrohydraulic wettability and an electronic channel.
The invention also solves the technical problems of providing a battery with excellent coulombic efficiency, cycle stability and rate capability.
In order to solve the above problems, in a first aspect, the present invention provides a high-specific-surface current collector, including a metal foil, the metal foil being provided with a plurality of concave holes, the diameter of the concave holes being equal to or less than 20 μm, the total area of the concave holes accounting for 25% or less of the total area of the metal foil, and the water drop angle of the metal foil being equal to or less than 5 °.
As an improvement of the above scheme, the surface energy of the metal foil is as follows: 2mol of deionized water is dripped on the metal foil, and the diffusion speed of the water drops is more than or equal to 20mm/5S.
As an improvement of the scheme, the diameter of the concave holes is less than or equal to 10 mu m.
As an improvement of the scheme, the metal foil is copper foil or aluminum foil.
As an improvement of the scheme, the thickness of the metal foil is 10-30 mu m. Preferably, the thickness of the metal foil is 12-20 μm.
As an improvement of the scheme, the preparation method of the metal foil comprises the following steps: and adopting two high-energy physical discharge processes to carry out metal treatment on the smooth metal foil so as to form a plurality of concave holes on the smooth metal foil.
As an improvement of the above-mentioned scheme, the smooth metal foil is irradiated with laser light.
In a second aspect, the invention provides an electrode sheet, which comprises a current collector and an electrode material, wherein the current collector is any one of the high-ratio surface current collectors, and the electrode material is a positive electrode material or a negative electrode material.
As an improvement of the scheme, the resistivity of the electrode slice is less than or equal to 30Ω·m;
And/or the peel strength of the electrode slice is more than or equal to 13N/25mm.
In a third aspect, the present invention provides a battery, including an electrode sheet as described in any one of the above.
The implementation of the invention has the following beneficial effects:
the high-specific-surface current collector has higher specific surface area and increases the adhesive force with electrode materials by more than 15 percent.
The high-specific surface current collector has a higher surface tension value, excellent electrohydraulic wettability and a good electronic channel, and is beneficial to reducing the internal resistance (the internal resistance is lower by more than 50 percent) of the lithium ion battery, so that the coulomb efficiency, the circulation stability and the multiplying power performance of the battery are improved; in addition, the heat in the battery can be effectively dispersed, so that the temperature rise of the battery is reduced, and the service life of the battery is prolonged.
The high-specific surface collector has flexibility, and can not only enable the elastomer in the electrode material to repeatedly expand and shrink without falling off, but also reduce the contact internal resistance with the electrode material and the transmission internal resistance.
Compared with a smooth metal foil, the metal foil has the advantages that the volume ratio is unchanged, the specific surface area is increased, the contact surface with an electrode material is increased, the electrode material can be embedded, the cost is low, and on one hand, the metal foil can replace a current collector coated with a carbon material; on the other hand, can also be used in combination with carbon materials.
Drawings
FIG. 1 is a graph showing the surface energy test effect of a high-specific-surface-area current collector according to the present invention;
FIG. 2 is a graph showing the surface energy test effect of a conventional polished aluminum foil;
FIG. 3 is an electron microscope image of a high specific surface area current collector of the present invention;
FIG. 4 is an electron microscope image of a conventional plain aluminum foil;
FIG. 5 is a schematic view of one embodiment of a laser irradiated metal foil of the present invention;
FIG. 6 is a schematic view of another embodiment of a laser irradiated metal foil of the present invention;
FIG. 7 is an enlarged view of the recess formed by the method of the present invention;
fig. 8 is an enlarged view of a recess formed by a chemical etching method.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings, for the purpose of making the objects, technical solutions and advantages of the present invention more apparent. It is only stated that the terms of orientation such as up, down, left, right, front, back, inner, outer, etc. used in this document or the imminent present invention, are used only with reference to the drawings of the present invention, and are not meant to be limiting in any way.
The high-specific surface current collector provided by the invention comprises a metal foil, wherein the metal foil is provided with a plurality of concave holes, the diameter of each concave hole is less than or equal to 20 mu m, the total area of each concave hole accounts for 25% or less of the total area of the metal foil, and the water drop angle of the metal foil is less than or equal to 1 degree.
The existing smooth metal foil is thicker in passivation layer, large in oil content and incapable of being removed cleanly due to multiple single rolling passes, so that contact internal resistance between an electrode material (such as LFP) and the metal foil is larger, and the existing method only has the effect of improving adhesion and cannot reduce contact internal resistance when the carbon material is coated on the smooth metal foil. In addition, the use of high power corona opportunities to generate large amounts of metallic aluminum powder or iron-containing aluminum powder (1100 alloy) can result in excessive self-discharge of the cell, especially at high rates.
The high-specific-surface current collector has higher specific surface area and increases the adhesive force with electrode materials by more than 15 percent.
The high-specific surface current collector has a higher surface tension value, excellent electrohydraulic wettability and a good electronic channel, and is beneficial to reducing the internal resistance (the internal resistance is lower by more than 50 percent) of the lithium ion battery, so that the coulomb efficiency, the circulation stability and the multiplying power performance of the battery are improved; in addition, the heat in the battery can be effectively dispersed, so that the temperature rise of the battery is reduced, and the service life of the battery is prolonged.
The high-specific surface collector has flexibility, and can not only enable the elastomer in the electrode material to repeatedly expand and shrink without falling off, but also reduce the contact internal resistance with the electrode material and the transmission internal resistance.
Compared with a smooth metal foil, the metal foil has the advantages that the volume ratio is unchanged, the specific surface area is increased, the contact surface with an electrode material is increased, the electrode material can be embedded, the cost is low, and on one hand, the metal foil can replace a current collector coated with a carbon material; on the other hand, can also be used in combination with carbon materials.
Specifically, the surface energy of the metal foil is as follows: 2mol of deionized water is dripped on the metal foil, and the diffusion speed of the water drops is more than or equal to 20mm/5S. That is, 1 drop of 2mol of deionized water was dropped on the metal foil, and the diameter of the water drop was 20mm after 5 seconds, as shown in FIG. 1. Fig. 2 is a graph showing the surface energy test effect of a commercially available smooth aluminum foil, and as can be seen from fig. 1 and 2, the high-ratio current collector of the present invention has good wettability, so that good electron current can be provided, and the internal resistance of the battery can be reduced.
The metal foil material is copper foil or aluminum foil. Among them, copper foil is generally used as a current collector of a negative electrode material, and aluminum foil is generally used as a current collector of a positive electrode material.
The thickness of the metal foil is important for the energy density of the battery. The thinner the thickness of the metal foil, the higher the energy density of the electrode, because the energy of the lithium battery is mainly concentrated in the cathode material, and the excessive thickness of the metal foil may cause an increase in the internal resistance of the battery, thereby reducing the energy density of the battery. In addition, the metal foil is required to carry the active material and fix it on the electrode, which has a certain requirement for its thickness. If the thickness of the metal foil is too thin, the carrying capacity of the metal foil is affected, and the stability of the electrode is further affected. Preferably, the thickness of the metal foil is 8-30 μm. More preferably, the thickness of the metal foil is 12 to 20. Mu.m.
The specific thickness of the metal foil needs to be selected and optimized according to the specific use situation to achieve the best electrode performance.
In the production process of the lithium ion battery, the processes of coating, rolling, winding, core pressing, shaping and the like require that the metal foil current collector and the pole piece remain intact, and certain requirements on the tensile strength, the elongation and the bending performance of the metal foil current collector are met. In order to improve the energy density of the lithium ion battery, the thickness of the metal foil current collector is preferably 10-15 mu m, and if the total area of concave holes accounts for more than 25% of the total area of the metal foil, the mechanical property of the metal foil can be reduced, and the requirements of the pole piece manufacturing process cannot be met. Preferably, the total area of the concave holes is 15% -25% of the total area of the metal foil. In addition, the diameter of the concave holes also affects the mechanical properties of the metal foil and the adhesion between the metal foil and the active substance. Thus the diameter of the concave holes is less than or equal to 20 mu m. Preferably, the diameter of the recess is 10 μm or less.
Compared with a smooth aluminum foil, the high-ratio-meter current collector has the following advantages:
(1) More electrode materials can be loaded, so that the cohesiveness of the current collector foil and the electrode materials is improved, and thick electrodes, ultrathin electrodes and dry electrodes are facilitated;
(2) The repeated deformation and stress of the elastic body during expansion and contraction can be relaxed, and the cycle life of the battery can be prolonged;
(3) The generation of dendrites of the positive and negative electrodes can be reduced and delayed, the growth direction of dendrites can be changed, and the safety of the battery can be improved;
(4) The problems of anode and cathode and anode surfaces can be reduced, the permeation and infiltration of electrolyte among high-rate battery core active substances under high voltage can be improved, lithium ions can migrate more freely, ohmic polarization and concentration polarization among the active substances can be reduced, and the battery rate and the cycle service life can be prolonged;
(5) The duty ratio of the foil in the battery quality is reduced, and the battery energy density is improved;
(6) Improve electrolyte wettability, and improve production efficiency and consistency and yield of the battery.
In addition, in the production process of the lithium ion battery, the processes of coating, rolling, winding, core pressing, shaping and the like require that the metal foil current collector and the pole piece remain intact, and certain requirements on the tensile strength, the elongation and the bending performance of the metal foil current collector are met.
In order to solve the problems, correspondingly, the preparation method of the high-ratio meter current collector provided by the invention comprises the following steps of:
s1, providing a smooth metal foil;
s2, treating the light surface metal foil by adopting two high-energy physical discharge processes to obtain a semi-finished metal foil;
And S3, sequentially performing thermal acid treatment, cleaning and drying on the semi-finished metal foil to obtain the metal foil with the high specific surface area.
The specific surface area of the high-specific surface metal foil prepared by the method is 10% or more than that of the smooth metal foil, and the tensile strength of the high-specific surface metal foil is 3% or less than that of the smooth metal foil.
Compared with the smooth metal foil, the specific surface area of the high-specific-surface metal foil is increased by 10% or more, so that the adhesive force between the high-specific-surface metal foil and the electrode material is increased by 15% or more.
In addition, the high-ratio surface metal foil has a higher surface tension value, excellent electrohydraulic wettability and a good electronic channel, and is beneficial to reducing the internal resistance (the internal resistance is lower by more than 50 percent) of the lithium ion battery, so that the coulomb efficiency, the circulation stability and the multiplying power performance of the battery are improved; in addition, the heat in the battery can be effectively dispersed, so that the temperature rise of the battery is reduced, and the service life of the battery is prolonged.
And secondly, the high-specific surface metal foil has better flexibility, so that the elastomer in the electrode material can be repeatedly expanded and contracted without falling off, and the contact internal resistance with the electrode material and the transmission internal resistance can be reduced.
Compared with a smooth metal foil, the high-specific surface metal foil has the advantages that the volume ratio is unchanged, the specific surface area is increased, the contact surface with an electrode material is increased, the electrode material can be embedded, the cost is low, and on one hand, the high-specific surface metal foil can replace a current collector coated with a carbon material; on the other hand, can also be used in combination with carbon materials.
Specifically, the invention adopts two high-energy physical discharge processes to carry out metal treatment on the smooth metal foil so as to form a plurality of concave holes on the smooth metal foil. Referring to fig. 3 and 4, fig. 3 is an electron microscope image of the high specific surface metal aluminum foil of the present invention, and fig. 4 is an electron microscope image of a commercial smooth aluminum foil (smooth aluminum foil in step S1), it can be seen from fig. 3 and 4 that the surface area of the high specific surface metal aluminum foil manufactured by the manufacturing method of the present invention is significantly increased, wherein one high energy physical discharge process forms concave holes with good dimensional uniformity and distribution on the metal aluminum foil, and the other high energy physical discharge process further etches the metal aluminum foil around the concave holes, so that the specific surface area of the metal aluminum foil is further increased without affecting the tensile strength of the metal aluminum foil. The smooth aluminum foil surface cannot increase the surface area, and thus cannot enlarge the contact area with the electrode material.
The method for metal treatment of the light surface metal foil by adopting two high-energy physical discharge processes comprises the following steps: the laser irradiates the smooth metal foil to change the grain structure and orientation of the surface of the metal foil, and the surface roughness of the metal foil is controlled to obtain the target number and aperture concave holes.
Because the laser beam has the characteristics of large energy density, controllable direction, strong convergence capability and the like, the laser interacts with pollutants such as oil stains, oxide layers and the like attached to the smooth metal foil and is separated from the smooth metal foil in the forms of instant thermal expansion, melting, gas volatilization and the like.
Specifically, spot laser is adopted to carry out laser perforation on the optical surface metal foil so as to form concave holes; and laser ablation is carried out on the smooth metal foil by adopting linear laser so as to remove oxide layers, greasy dirt and scraps generated by laser perforation on the smooth metal foil. The laser has large spot energy, can impact concave holes on the surface of the metal foil, is relatively lower than the spot laser energy, but has large action area, and can quickly gasify pollutants such as greasy dirt, oxide layers and the like on the surface of the metal foil and remove scraps generated by laser perforation.
According to the invention, through the mutual matching of the two lasers, not only can the concave holes with the target size be obtained, but also the concave holes are uniformly distributed, and the influence on the tensile strength of the metal foil is small.
The laser wavelength, laser power, pulse width and pulse frequency have important effects on the formation of the pits, but are specifically defined according to the number and size of the pits and the thickness of the smooth metal foil. If the thickness of the smooth metal foil is 10-30 mu m, the diameter of the concave holes is less than or equal to 20 mu m, and the total area of the concave holes is 15-25% of the total area of the smooth metal foil, the laser parameters are set as follows:
Spot laser with wavelength of 520-540 nm, laser power of 8-10W, pulse width of 5-8 ns and pulse frequency of 60-100 MHz;
The linear laser has the laser wavelength of 1000-1100 nm, the laser power of 3-5W, the pulse width of 1-3 ns and the pulse frequency of 20-50 MHz.
Referring to fig. 5, the laser light source 2 may be disposed on one side of the smooth metal foil 1, so that a concave hole is formed on one side of the smooth metal foil 1. In addition, referring to fig. 6, the laser light sources 2 may be disposed on both sides of the smooth metal foil 1, respectively, so that both sides of the smooth metal foil 1 form concave holes.
Specifically, the method for performing thermal acid treatment on the semi-finished metal foil in the step S3 includes: the semi-finished metal foil is soaked in a pickling tank, pickling solution in the pickling tank comprises HF and H 2 SO4, and the temperature of the pickling solution is 40-50 ℃. The heat acid treatment can further remove debris, greasy dirt and other impurities on the metal foil, iron ions, magnesium ions and the like, further improve the wettability of the metal foil and enable lithium ions to migrate more freely. More importantly, as the edges of the concave holes generated by laser perforation are uneven, oxidation reaction can be carried out on the periphery of the concave holes to generate a layer of oxide film.
Compared with the common pickling solution, the concentration of the pickling solution cannot be too high, otherwise, the aperture of the concave holes, the tensile strength of the metal foil and the like are affected. Preferably, the total mass of HF and H 2SO4 is 2-3% of the total mass of the pickling solution, and the mass ratio of HF to H 2SO4 is 1: (2.5-5). More preferably, the total mass of HF and H 2SO4 is 2.2-2.8% of the total mass of the pickling solution, and the mass ratio of HF to H 2SO4 is 1: (3-4).
After the metal foil passes through the pickling tank, the metal foil is also required to be cleaned through a cleaning tank, and deionized water is contained in the cleaning tank, so that the main functions are to remove residual pickling solution on the metal foil and decomposition products generated in the pickling process, and the cleanliness and the surface wetting tension of the metal foil are effectively improved. If the cleaning tank is absent, the pickling solution and the decomposed products of the pickling remain on the metal foil can influence the conductivity or electrochemical performance of the conductive coating or the electrode active material subsequently coated on the metal foil, thereby influencing the service life, the cycle number, the electric quantity and the like of the lithium battery.
Preferably, the deionized water is at a temperature of 50 to 70 ℃. More preferably, the deionized water temperature is 55-60 ℃.
Referring to fig. 7 and 8, fig. 7 is an enlarged view of a pit formed by the preparation method of the present invention, and fig. 8 is an enlarged view of a pit formed by a chemical etching method, it is apparent from fig. 7 and 8 that the method of opening holes by using two high-energy physical discharge processes of the present invention has high productivity, and compared with the existing method of opening holes by using a metal foil by chemical etching, the present invention has high uniformity of pit aperture formed by laser irradiation of an optical aluminum foil by using a spot laser, and has high uniformity of pit aperture, while the pit formed by using a chemical etching method has uneven distribution of pit aperture, and has different sizes of pit aperture.
The preparation method is simple, and the two high-energy physical discharge processes are adopted to treat the light surface metal foil, so that not only can greasy dirt, oxide layers, impurities and the like on the surface of the metal foil be removed, but also the crystal grain structure and the orientation on the surface of the metal foil can be changed, and the surface roughness of the metal foil can be controlled to obtain concave holes with target quantity and aperture, and finally, the high-specific surface area, high adhesive force, good wettability and low internal resistance of the high-specific surface metal foil can be obtained under the condition that the tensile strength of the metal foil is not influenced.
In addition, the preparation method disclosed by the invention is more environment-friendly by only treating through a low-concentration pickling tank.
The invention also provides an electrode plate which comprises the current collector and electrode materials, wherein the current collector is the high-ratio meter current collector.
The electrode sheet of the invention can be an anode electrode sheet or a cathode electrode sheet. If the metal foil of the current collector is aluminum foil and the electrode material is positive electrode material, the electrode plate is positive electrode plate. If the metal foil of the current collector is copper foil and the electrode material is negative electrode material, the electrode plate is a negative electrode plate.
The current collector has high specific surface area, so that the contact area between the current collector and the electrode material is large, and the electrode sheet has low resistivity and high peeling strength.
The electrode sheet of the invention can be a semi-solid electrode sheet, a solid electrode sheet or a dry electrode sheet.
Correspondingly, the invention also provides a battery, which comprises the electrode plate. Specifically, the battery of the invention is a lithium iron battery.
The invention will be further illustrated by the following specific examples
Example 1
The preparation method of the high-specific-surface current collector comprises the following steps:
s1, providing a polished aluminum foil with the thickness of 15 mu m;
s2, sequentially irradiating two sides of the light-surface aluminum foil by using point laser and linear laser to obtain a semi-finished aluminum foil;
wherein, parameters of the punctiform laser are as follows: the laser wavelength is 525nm, the laser power is 8W, the pulse width is 6ns, and the pulse frequency is 70MHz;
the parameters of the line laser are as follows: the laser wavelength is 1040nm, the laser power is 3W, the pulse width is 2ns, and the pulse frequency is 30MHz;
S3, sequentially carrying out heat acid treatment, cleaning and drying on the semi-finished aluminum foil to obtain a high-ratio aluminum foil, wherein the aluminum foil is provided with concave holes;
Wherein the method of thermal acid treatment comprises: soaking the semi-finished aluminum foil in a pickling tank, wherein pickling solution in the pickling tank comprises the following components in percentage by mass: 3 and H 2 SO4, the temperature of the pickling solution being 45 ℃, the total mass of HF and H 2SO4 being 2% of the total mass of the pickling solution;
The high-ratio surface current collector prepared by the embodiment has the total area of concave holes accounting for 25% of the total area of the aluminum foil on the light surface, the diameter of the concave holes is less than or equal to 10 mu m, and the water drop angle of the high-ratio surface aluminum foil is less than or equal to 5 degrees.
Example 2
The preparation method of the high-specific-surface current collector comprises the following steps:
s1, providing a polished aluminum foil with the thickness of 15 mu m;
s2, sequentially irradiating two sides of the light-surface aluminum foil by using point laser and linear laser to obtain a semi-finished aluminum foil;
wherein, parameters of the punctiform laser are as follows: the laser wavelength is 525nm, the laser power is 9W, the pulse width is 7ns, and the pulse frequency is 80MHz;
The parameters of the line laser are as follows: the laser wavelength is 1040nm, the laser power is 4W, the pulse width is 2ns, and the pulse frequency is 40MHz;
S3, sequentially carrying out heat acid treatment, cleaning and drying on the semi-finished aluminum foil to obtain the aluminum foil with the high specific surface area;
Wherein the method of thermal acid treatment comprises: soaking the semi-finished aluminum foil in a pickling tank, wherein pickling solution in the pickling tank comprises the following components in percentage by mass: 4 and H 2 SO4, the temperature of the pickling solution is 50 ℃, and the total mass of the HF and the H 2SO4 is 2.5% of the total mass of the pickling solution.
The high-ratio surface current collector prepared by the embodiment has the total area of concave holes accounting for 23% of the total area of the aluminum foil on the light surface, the diameter of the concave holes is less than or equal to 10 mu m, and the water drop angle of the high-ratio surface aluminum foil is less than or equal to 5 degrees.
Comparative example 1
Commercial polished aluminum foil was 15 μm thick and had a water drop angle of 110 °.
Comparative example 2
The preparation method of the high-specific-surface current collector comprises the following steps:
s1, providing a polished aluminum foil with the thickness of 15 mu m;
S2, irradiating two sides of the polished aluminum foil by using point laser to obtain a semi-finished aluminum foil;
wherein, parameters of the punctiform laser are as follows: the laser wavelength is 525nm, the laser power is 8W, the pulse width is 6ns, and the pulse frequency is 70MHz;
S3, sequentially carrying out heat acid treatment, cleaning and drying on the semi-finished aluminum foil to obtain the aluminum foil with the high specific surface area;
Wherein the method of thermal acid treatment comprises: soaking the semi-finished aluminum foil in a pickling tank, wherein pickling solution in the pickling tank comprises the following components in percentage by mass: 3 and H 2 SO4, the temperature of the pickling solution is 45 ℃, and the total mass of the HF and the H 2SO4 is 2% of the total mass of the pickling solution.
The high-ratio surface current collector prepared by the embodiment has the total area of concave holes accounting for 11% of the total area of the aluminum foil on the light surface, the diameter of the concave holes is less than or equal to 30 mu m, and the water drop angle of the high-ratio surface aluminum foil is less than or equal to 10 degrees.
Comparative example 3
The preparation method of the high-specific-surface current collector comprises the following steps:
s1, providing a polished aluminum foil with the thickness of 15 mu m;
S2, irradiating two sides of the polished aluminum foil by using linear laser to obtain a semi-finished aluminum foil;
The parameters of the line laser are as follows: the laser wavelength is 1040nm, the laser power is 3W, the pulse width is 2ns, and the pulse frequency is 30MHz;
S3, sequentially carrying out heat acid treatment, cleaning and drying on the semi-finished aluminum foil to obtain the aluminum foil with the high specific surface area;
Wherein the method of thermal acid treatment comprises: soaking the semi-finished aluminum foil in a pickling tank, wherein pickling solution in the pickling tank comprises the following components in percentage by mass: 3 and H 2 SO4, the temperature of the pickling solution is 45 ℃, and the total mass of the HF and the H 2SO4 is 2% of the total mass of the pickling solution.
The high-ratio surface current collector prepared by the embodiment has the total area of concave holes accounting for 8% of the total area of the aluminum foil on the light surface, the diameter of the concave holes is more than or equal to 30 mu m, and the water drop angle of the high-ratio surface aluminum foil is less than or equal to 10 degrees.
The current collectors of example 1, example 2, comparative examples 1to 3 were made into electrode sheets and batteries, and the resistance and peel strength of each electrode sheet, and the gram capacity results of the test electrodes were shown in table 1.
The polished aluminum foils of examples 1 to 2 and comparative examples 1 to 3 were from the same supplier and were of the same lot. The high-ratio aluminum foils prepared in comparative example 1 (polished aluminum foil), examples 1-2 and comparative examples 2-3 were tested to form 5 test groups, 3 samples were taken from each test group, and the results were averaged, wherein the test items included tensile strength, specific surface area, and resistance, and the tensile strength decrease rate and specific surface area increase rate of the aluminum foil were calculated, and the tensile strength decrease rate (%) = (tensile strength of the blank group-tensile strength of the aluminum foil of the test group)/tensile strength of the blank group × 100%, and the specific surface area increase rate (%) = (specific surface area of the test group-specific surface area of the blank group)/specific surface area of the blank group × 100%;
The high-ratio aluminum foils prepared in examples 1 to 2 and comparative examples 2 to 3 and the glossy aluminum foil of comparative example 1 were prepared into electrode sheets and batteries, and specifically, electrode slurry consisting of 95% by mass of lithium nickel cobalt manganese oxide and 5% by mass of PVDF binder was coated on the high-ratio aluminum foils and the glossy aluminum foils to form an electrode layer having a thickness of 170 μm. The resistance and peel strength of each electrode sheet, and the gram capacity of the electrodes were tested. And the electrode sheets of examples 1 to 2 and comparative examples 1 to 3 were subjected to an aging test, and were divided into 5 groups each having 5 samples, and the results were averaged. Specifically, the electrode was placed in an aging oven at 200 ℃ for 96 hours, the separation area of the electrode layer and the aluminum foil of the electrode sheet was observed and counted, and the separation area ratio of the electrode sheet was calculated, the separation area ratio = separation area per electrode sheet/area per electrode sheet 100%, and the results are shown in table 1.
Table 1 test results for each of examples and comparative examples
From the results in table 1, it is understood that the high-ratio current collectors of examples 1 and 2 can increase the specific surface area of the metal foil by providing the metal foil with the target number and target size of concave holes, and can embed more electrode materials and increase the electrode gram capacity without changing the volume ratio of the metal foil, as compared with comparative examples 1 to 3. In addition, the high ratio surface collectors of examples 1 and 2 have high adhesion to the electrode material, and thus the peel strength of the electrode sheet is significantly higher than that of comparative examples 1 to 3. Further, the high specific surface current collectors of examples 1 and 2 have good wettability and electron channels, and thus the sheet resistance thereof is also significantly lower than that of examples 1 to 3.
The foregoing is a preferred embodiment of the present invention and it should be noted that modifications and adaptations to those skilled in the art may be made without departing from the principles of the present invention and are intended to be comprehended within the scope of the present invention.
Claims (10)
1. The high-specific-surface-area current collector is characterized by comprising a metal foil, wherein the metal foil is provided with a plurality of concave holes, the diameter of each concave hole is less than or equal to 20 mu m, the total area of each concave hole accounts for 25% or less of the total area of the metal foil, and the water drop angle of the metal foil is less than or equal to 5 degrees.
2. The high-ratio surface collector of claim 1, wherein the surface energy of the metal foil is as follows: 2mol of deionized water is dripped on the metal foil, and the diffusion speed of the water drops is more than or equal to 20mm/5S.
3. The high-specific gravity current collector according to claim 1, wherein the diameter of the concave hole is 10 μm or less.
4. The high-ratio surface current collector according to claim 1, wherein the metal foil is copper foil or aluminum foil;
And/or the thickness of the metal foil is 10-30 μm.
5. A method for preparing the high-specific-surface collector as set forth in any one of claims 1 to 4, comprising the steps of:
s1, providing a smooth metal foil;
S2, treating the smooth metal foil by adopting two high-energy physical discharge processes to obtain a semi-finished metal foil;
And S3, sequentially carrying out heat acid treatment, cleaning and drying on the semi-finished metal foil to obtain a high-specific-surface metal foil, wherein the specific surface area of the high-specific-surface metal foil is 10% or more than that of the smooth metal foil, and the tensile strength of the high-specific-surface metal foil is 3% or less than that of the smooth metal foil.
6. The method for preparing a high-specific-surface-area current collector according to claim 5, wherein in step S2, the method for treating the smooth metal foil by using two high-energy physical discharge processes comprises: and irradiating the smooth metal foil by adopting two lasers to form a plurality of concave holes on the smooth metal foil.
7. The method for manufacturing a high-specific-surface-area current collector according to claim 6, wherein the method for irradiating the smooth metal foil with two kinds of laser light comprises:
Carrying out laser perforation on the smooth metal foil by using point laser so as to form the concave hole;
and (3) carrying out laser ablation on the smooth metal foil by using linear laser so as to remove oxide layers, greasy dirt and scraps generated by laser perforation on the smooth metal foil.
8. The method for preparing a high specific surface area current collector according to claim 5, wherein in step S3, the method for performing thermal acid treatment on the semi-finished metal foil comprises: and soaking the semi-finished metal foil in a pickling tank, wherein pickling solution in the pickling tank comprises HF and H 2 SO4, and the temperature of the pickling solution is 40-50 ℃.
9. An electrode sheet comprising a current collector and an electrode material, wherein the current collector is the high-specific-surface current collector according to any one of claims 1 to 4.
10. A battery comprising the electrode sheet according to claim 9.
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