CN109802142B - Porous copper foil for lithium ion battery - Google Patents
Porous copper foil for lithium ion battery Download PDFInfo
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- CN109802142B CN109802142B CN201910072950.8A CN201910072950A CN109802142B CN 109802142 B CN109802142 B CN 109802142B CN 201910072950 A CN201910072950 A CN 201910072950A CN 109802142 B CN109802142 B CN 109802142B
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Abstract
The invention discloses a porous copper foil for a lithium ion battery. Micropores penetrating through the upper surface and the lower surface of the copper foil are regularly distributed on the porous copper foil; the micropores include two micropores with different pore diameters; the arrangement of the large micropores and the small micropores is in a shape of arrangement of boron-oxygen three-membered rings in the borate glass, wherein the large micropores are positioned at oxygen positions of the arrangement shape of the boron-oxygen three-membered rings, and the small micropores are positioned at boron positions of the arrangement shape of the boron-oxygen three-membered rings. The aperture of the small micropore is one fourth of that of the large micropore, and the distance between two nearest adjacent large micropores is 3 times of the diameter of the large micropore. The design of the invention effectively increases the pore area of unit area, effectively improves the battery capacity on the premise of ensuring enough strength, and achieves the purposes of effectively improving the load capacity and the adsorption capacity of the negative electrode material on the copper foil of unit area and considering the requirements of electrode quality and performance so as to meet the development requirement of circuit integration.
Description
Technical Field
The invention relates to a copper foil for a lithium ion battery, in particular to a porous copper foil.
Background
With the coming of environmental crisis, coal resources are in shortage day by day, and a large amount of harmful gas is discharged to pollute the atmospheric environment through coal combustion power generation, and the environmental protection is not slow due to the fact that the disastrous weather such as haze is serious. With the development of new energy automobiles, the demand of lithium ion batteries has increased dramatically. In addition, the lithium ion battery is widely applied to electric appliances such as mobile phones and notebook computers, and becomes a novel sustainable environment-friendly power generation method.
Lithium ion batteries operate by mainly relying on the intercalation or deintercalation of lithium ions in the positive or negative electrode material. The negative electrode is typically made of activated graphite attached to a copper foil about 8 microns thick. The copper foil functions as a carrier and also functions as a current collector, collecting and conducting electrons. Because copper is a good conductor and has lower resistance, the dynamic amplification of the internal resistance of the battery can be reduced, and the service life of the battery is prolonged.
Along with the integration development of electronic devices, lithium ion batteries with smaller size, lighter weight and better performance are developed, and the demand for effectively improving the comprehensive performance of the lithium ion batteries is more and more urgent. At the present stage, the traditional nonporous copper foil has limited surface area and general adsorption capacity, is difficult to bear more negative electrode materials, and directly influences the service performance and the service life of the lithium ion battery; in the traditional nonporous copper foil, the wettability of the electrolyte on a high-density negative electrode material is difficult to improve; the traditional nonporous copper foil cannot meet the requirements of quality, volume and performance, and is difficult to meet the requirement of circuit integration development.
Disclosure of Invention
Based on the technical problems that the traditional copper foil for the lithium ion battery in the prior art is difficult to bear more negative electrode materials and cannot meet the requirements of quality, volume and performance, the invention provides the porous copper foil with high specific surface area and high load capacity.
Based on the above purpose, the inventor of the present invention designs a copper foil with multiple pores to realize the increase of the bearing capacity of the negative electrode material, and simultaneously reduce the mass and the volume to meet the integration requirement. The inventor designs a porous copper foil with a specific hole distribution scheme by methods of calculation, simulation and the like so as to achieve the aim. The inventor tests the mechanical properties of different hole designs, the bearing capacity of the cathode material and the like through repeated research, calculation and simulation, thereby obtaining the technical scheme of the invention as follows: a porous copper foil for a lithium ion battery is disclosed, wherein micropores penetrating through the upper surface and the lower surface of the copper foil are regularly distributed on the copper foil; the micropores comprise two micropores with different pore diameters, namely big micropores and small micropores; the regular distribution means that the arrangement of the large micropores and the small micropores is in the shape of arrangement of boron-oxygen three-membered rings in the borate glass, wherein the large micropores are positioned at oxygen positions of the arrangement shape of the boron-oxygen three-membered rings, and the small micropores are positioned at boron positions of the arrangement shape of the boron-oxygen three-membered rings.
The using requirement of the lithium ion battery is met, and the preferred thickness of the copper foil is 6-100 mu m.
Through repeated theoretical calculation and simulation analysis, the inventor preferably selects the pore diameter of the small micropores to be one fourth of that of the large micropores, and the pore diameter of the large micropores to be 10-1000 mu m; the distance between two nearest neighbor macro-micropores is 3 times of the diameter of the macro-micropores. More preferably, the pore diameter of the large micropores is 40 μm, the pore diameter of the small micropores is 10 μm, and the distance between two nearest large micropores is 120 μm.
The hole distribution design of the porous copper foil is based on finite element simulation analysis and theoretical optimization results. Usually, the form of the holes arranged in an equilateral triangle is a commonly adopted design scheme, but when the hole configuration is subjected to external load, a compressive stress area is generated in the right center of the triangle, and the compressive stress is easy to destabilize due to the fact that the thickness of the copper foil for the lithium ion battery is only tens of microns, so that the overall hole configuration is unstable. The invention adopts the arrangement mode of boron-oxygen three-membered rings in borate glass to distribute micropores with two pore diameters, the large micropores at the oxygen positions in the arrangement shape of the boron-oxygen three-membered rings just form an equilateral triangle, the small micropores at the boron positions in the arrangement shape of the oxygen three-membered rings are equivalent to the centers of the equilateral triangles formed by the large micropores, and the compressive stress formed by the large micropores at the centers of the equilateral triangles when external load is applied is just met by reasonably designing the pore diameters and the pore diameter proportion of the large micropores and the small micropores, and the original compressive stress is eliminated due to the tensile stress area generated by the introduction of the small micropores. Therefore, the instability problem can be avoided, and the pore area per unit area is effectively increased, namely the porosity is increased; the capacity of the battery is effectively improved on the premise of ensuring enough strength, and the invention aims of effectively improving the loading capacity and adsorption capacity of the negative electrode material on the copper foil in unit area and meeting the requirements of electrode quality and performance so as to meet the development requirement of circuit integration are fulfilled.
The invention also provides a preparation method of the porous copper foil for the lithium ion battery, which comprises the following steps:
1) preparing copper foil by an electrolytic method; the thickness of the prepared copper foil is preferably 6-100 mu m;
2) two micropores with different apertures are regularly manufactured on the copper foil by a mechanical punching or electrochemical hole making method, the arrangement of the micropores is in a boron-oxygen three-membered ring arrangement shape in the borate glass, wherein the micropore with a large aperture is positioned at an oxygen position of the boron-oxygen three-membered ring arrangement shape, and the micropore with a small aperture is positioned at a boron position of the boron-oxygen three-membered ring arrangement shape.
Drawings
FIG. 1 is a graph showing the variation of the relative tensile strength and porosity of the porous copper foil design of the present invention as verified by Matlab analysis.
FIG. 2 is a schematic view showing the micropore design of a porous copper foil according to example 1 of the present invention.
FIG. 3 is a schematic view showing the micropore design of a porous copper foil according to example 2 of the present invention.
FIG. 4 is a schematic view of a microporous design of a porous copper foil according to example 3 of the present invention.
Fig. 5 is a graph of simulation results for simulating the porous copper foil design of example 1 using ANSYS analysis.
Fig. 6 is a graph of simulation results for simulating the porous copper foil design of example 2 using ANSYS analysis.
Fig. 7 is a graph of simulation results for simulating the porous copper foil design of example 3 using ANSYS analysis.
Wherein the units of the numbers in FIGS. 2 to 4 are μm.
Detailed Description
The invention is further described with reference to the following figures and specific examples. It should be understood, however, that these examples are for illustrative use only in greater detail and are not to be construed as limiting the invention in any way.
The inventor constructs a porous arrangement scheme taking a boron-oxygen ternary ring structure in borate glass as an arrangement shape and a pore diameter proportion and pore diameter optimization scheme for determining the size of micropores by methods of theoretical calculation, simulation, repeated structure optimization and the like. Through further performance simulation tests, the constructed porous copper foil is proved to effectively improve the battery capacity on the premise of ensuring sufficient strength, and the invention aims of effectively improving the load capacity and the adsorption capacity of the negative electrode material on the copper foil in unit area and meeting the requirements of electrode quality and performance so as to meet the development requirements of circuit integration are fulfilled.
Firstly, the inventor determines a porous arrangement scheme that a boron-oxygen three-membered ring structure in the borate glass is in an arrangement shape and a distribution mode that micropores with large pore diameters are located at oxygen positions of the boron-oxygen three-membered ring arrangement shape and micropores with small pore diameters are located at boron positions of the boron-oxygen three-membered ring arrangement shape through theoretical calculation; and the pore diameter of the large micropores is preferably 4 times of that of the small micropores by methods such as finite element simulation analysis, and the distance between two nearest-neighbor large micropores is preferably 3 times of that of the large micropores. The inventors performed analysis using Matlab to verify the relative tensile strength versus porosity variation for this design choice. Specifically, the following are described:
performing verification analysis by using Matlab, and setting the hole distance of two nearest neighbor macro-micro holes as
The pore diameter of the macro-micro pores is
The pore diameter of the small micropores is
And calculating the porosity q according to the distribution of the pores:
；
calculating the relative tensile strength according to the distribution of the holes, regardless of the deformation of the copper foil, through linear simplificationk： 
。
In the case where the ratio of the pore diameters of the large micropores to the small micropores obtained by the inventors was 4:1, an image of the porosity and the relative tensile strength was plotted using matlab as shown in fig. 1. The distance between two nearest big micropores is 3 times of the diameter of the big micropores, and the diameter of the big micropores is larger than that of the nearest two nearest big microporesThe diameter is 4 times of the pore diameter of the small micropores, i.e.
:
=3:1，
:
Relative tensile strength according to figure 1 and above when =4:1kAnd the calculation formula of the porosity q, the closest is the relative tensile strengthk70 is taken, at which time the corresponding porosityq=12.24%；
:
:
=1:0.34:0.085, which is similar to the design of the present invention
:
=3:1，
:
And =4: 1. As can be seen from the attached figure 1, the design not only ensures that the mechanical property is not greatly lost, but also improves the porosity as much as possible, and achieves the purposes of effectively improving the loading capacity and the adsorption capacity of the negative electrode material on the copper foil in unit area, and meeting the requirements of the electrode quality and the performance so as to meet the development requirement of circuit integration.
In order to obtain the optimal copper foil porous design parameters, the inventor conducts repeated calculation and simulation analysis. Specifically, examples of constructing each preferred porous design are as follows.
Example 1
The porous copper foil micropores are designed as shown in figure 2, the pore diameter of the large micropores is 30 microns, the pore diameter of the small micropores is 7.5 microns, the distance between two nearest-neighbor large micropores is 90 microns, the large micropores form a boron-oxygen three-membered ring arrangement shape, the large micropores are positioned at the oxygen position of the boron-oxygen three-membered ring arrangement, namely, every three large micropores form an equilateral triangle shape, the small micropores are positioned at the boron position of the boron-oxygen three-membered ring arrangement, namely, a small micropore is distributed at the center of an equilateral triangle constructed by every three large micropores, therefore, the distance between the nearest-neighbor two small micropores is 51.96 microns; the arrangement is repeated in this way, and a hole arrangement scheme of the porous copper foil of the embodiment is constructed. For convenience, the porous arrangement scheme of this example is hereinafter referred to as configuration II.
Example 2
The difference from example 1 is that: the aperture of the big micropore is 40 μm, the aperture of the small micropore is 10 μm, the distance between two nearest big micropores is 120 μm, and the distance between two nearest small micropores is 69.28 μm. Hereinafter, the porous arrangement scheme of this embodiment is referred to as configuration III, and the design drawing is shown in FIG. 3.
Example 3
The difference from example 1 is that: the aperture of the big micropore is 50 μm, the aperture of the small micropore is 12.5 μm, the distance between two nearest big micropores is 150 μm, and the distance between two nearest small micropores is 86.60 μm. The porous arrangement scheme of the present embodiment is hereinafter referred to as configuration IV, and the design drawing is shown in FIG. 4.
The inventor adopts ANSYS analysis to simulate the strength conditions of the above examples and comparative examples, and the specific method is as follows:
the design model has a thickness of 8 μm and an area of 1 × 1 mm2Elastic modulus of 119 GPa, Poisson's ratio of 0.326 and density of 8900g/cm3. The left edge is restricted in the directions of x and z, and the right edge is uniformly tensioned.
And f is defined as the tensile force applied to the right edge per unit length when the internal maximum stress reaches 100 MPa, and b is the thickness of the copper foil. Designing pore size distribution with different gradients, and analyzing the stress condition by using ANSYS:
for configuration ii, i.e., the porous copper foil design of example 1: when the corresponding maximum stress is 100 MPa, the unit length applied tension f of the right edge is 230N/m; as shown in fig. 5.
For configuration iii, i.e., the porous copper foil design of example 2: when the corresponding maximum stress is 100 MPa, the unit length applied tension f of the right edge is 250N/m; as shown in fig. 6.
For configuration iv, i.e., the porous copper foil design of example 3: when the corresponding maximum stress is 100 MPa, the unit length applied tensile force f of the right edge is 220N/m, as shown in figure 7.
From the above comparison, the design scheme of the porous copper foil according to each example of the present invention is as follows: when the distance between two nearest large micropores is 3 times of the diameter of the large micropores and the pore diameter of the large micropores is 4 times of the pore diameter of the small micropores, the scheme ensures that the mechanical property is not greatly lost, improves the porosity as much as possible, and achieves the aims of effectively improving the loading capacity and the adsorption capacity of the negative electrode material on the copper foil in unit area and meeting the requirements of the electrode quality and the performance so as to meet the development requirements of the high-performance lithium ion battery. On the basis, the comparative analysis shows that the configuration III is optimal in different pore diameter selections of the embodiments, and the optimal selection of the large micropore with the pore diameter of 40 μm and the small micropore with the pore diameter of 10 μm can be determined.
While the foregoing is a detailed description of the preferred embodiment of the invention, it will be apparent to those skilled in the art that insubstantial changes in form and detail may be made in the steps recited above without departing from the scope of the invention, and the invention is not limited to the specific form and details set forth above.
Claims (5)
1. A porous copper foil for a lithium ion battery, characterized in that: micropores penetrating through the upper surface and the lower surface of the copper foil are regularly distributed on the copper foil; the micropores comprise two micropores with different pore diameters, namely big micropores and small micropores; the regular distribution refers to the arrangement of the large micropores and the small micropores in the shape of arrangement of boron-oxygen three-membered rings in the borate glass, wherein the large micropores are positioned at the oxygen positions of the arrangement of the boron-oxygen three-membered rings, and the small micropores are positioned at the boron positions of the arrangement of the boron-oxygen three-membered rings;
the aperture of the small micropores is one fourth of that of the large micropores; the distance between two nearest neighbor macro-micro pores is 3 times of the diameter of the macro-micro pores; the aperture of the large micropores is 10-1000 μm.
2. The porous copper foil for lithium ion batteries according to claim 1, characterized in that: the aperture of the big micropore is 40 μm, the aperture of the small micropore is 10 μm, and the distance between two nearest big micropores is 120 μm.
3. The porous copper foil for lithium ion batteries according to claim 1, characterized in that: the thickness of the copper foil is 6 to 100 μm.
4. A method for preparing a porous copper foil for a lithium ion battery according to any one of claims 1 to 3, comprising the steps of:
1) preparing copper foil by an electrolytic method;
2) two micropores with different apertures are regularly manufactured on the copper foil by a mechanical punching or electrochemical hole making method, the arrangement of the micropores is in a boron-oxygen three-membered ring arrangement shape in the borate glass, wherein the micropores with large apertures are positioned at the oxygen positions of the boron-oxygen three-membered ring arrangement shape, and the micropores with small apertures are positioned at the boron positions of the boron-oxygen three-membered ring arrangement shape;
wherein, the aperture ratio of the micropores with large aperture and the micropores with small aperture in the step 2 is 4:1, and the distance between the micropores with large aperture and the nearest neighbors is 3 times of the aperture of the micropores with large aperture.
5. The method according to claim 4, wherein: the thickness of the copper foil is 6-100 mu m.
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| JPS59114766A (en) * | 1982-12-20 | 1984-07-02 | Yuasa Battery Co Ltd | Manufacture of pocket type alkaline storage battery plate |
| GB9703920D0 (en) * | 1997-02-25 | 1997-04-16 | Univ Southampton | Method of preparing a porous metal |
| CN100561779C (en) * | 2006-02-22 | 2009-11-18 | 深圳市中金高能电池材料有限公司 | The processing method of perforated non-ferrous metal band for battery plate |
| CN101364644A (en) * | 2007-08-10 | 2009-02-11 | 深圳市比克电池有限公司 | Lithium battery current collecting body, high capacity cylindrical lithium ionic cell and preparation |
| US9517939B2 (en) * | 2012-05-09 | 2016-12-13 | The Board Of Trustees Of The University Of Illinois | Method of enhancing the connectivity of a colloidal template, and a highly interconnected porous structure |
| CN103247779A (en) * | 2013-04-16 | 2013-08-14 | 谭彬 | Production method of electrochemical active pole piece |
| US11196038B2 (en) * | 2017-05-22 | 2021-12-07 | Lg Chem, Ltd. | Flexible electrode, method for manufacturing the same and secondary battery including the same |
| CN107565168A (en) * | 2017-07-21 | 2018-01-09 | 安普瑞斯（无锡）有限公司 | A kind of lithium ion battery of high-energy-density high power density |
| CN207818780U (en) * | 2018-02-13 | 2018-09-04 | 宁德时代新能源科技股份有限公司 | Collector, pole piece and battery |
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