Microporous current collector and preparation method thereof

Abstract

The present invention relates to a microporous current collector and a preparation method thereof, and relates to the technical field of current collectors for secondary ion batteries, the microporous current collector comprises a current collector base material, the surface of the current collector base material is provided with uniformly distributed protrusions and pits, and the top end of each protrusion is provided with a small hole with a diameter of 10-50 nm; the current collector base material comprises an aluminum foil base material or a copper foil base material. According to the microporous current collector provided by the invention, the micro-pores with the diameter of 10-50nm are molded at the convex tips of the micro-molded aluminum foil by utilizing the principle of a tip effect, positive electrode slurry or negative electrode slurry cannot permeate through the micro-pores, and lithium ions can freely migrate in the micro-pores, so that the problems of non-uniform coating, lithium precipitation during charging and discharging of a battery and the like in the prior art are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of current collectors for secondary ion batteries, and in particular to a microporous current collector and a preparation method thereof. Background Art

[0002] The negative electrode current collector of lithium-ion batteries is copper foil, and the positive electrode current collector is aluminum foil, such as Figure 1 As shown in the figure, the negative electrode material is coated on both sides of the copper foil, and the positive electrode material is coated on both sides of the aluminum foil, and the positive and negative electrodes are separated by a separator in the middle. In the actual production process, the coating is uneven. Figure 1 Visually, it can be seen that the coating on the positive electrode A side has a bulge (i.e. Figure 1 During charging, lithium ions are deintercalated from the positive electrode material and embedded into the negative electrode material through the diaphragm. At the raised material pile on the positive electrode A side 108, the coating amount on the corresponding negative electrode B side is insufficient, and sufficient negative electrode material cannot be provided to the positive electrode A side material pile to absorb lithium ions. These lithium ions that cannot be absorbed by the negative electrode material are deposited on the negative electrode surface to form dendrites, which causes the life of the battery cell to decay rapidly. The dendrites piercing the diaphragm may also cause safety problems.

[0003] At present, in order to solve the above problems, microporous copper foil is often used in the prior art, such as Figure 2 As shown, when the negative electrode B surface cannot provide enough negative electrode material to absorb the lithium ions released from the positive electrode A surface, the lithium ions will pass through the 209 micropores on the copper foil and embed into the negative electrode material on the negative electrode A surface. For example, patent number CN 109056011 A discloses a technical solution for microporous copper foil: including an electrolytic cell on a raw foil frame, an anode plate in the electrolytic cell, a large number of pin points on the anode plate, the anode cell connected to the positive electrode of the power supply through a copper bus, a cathode roller connected to the negative electrode of the power supply is provided above the anode cell, and the cathode roller is a carrier for depositing copper foil to prepare microporous copper foil. However, the porosity of the copper foil obtained by the technical solution disclosed by patent number CN 109056011 A is 20%, and the pore size is 10 microns; the problem of micropore pore size ≥ 1um: the current coating method in the lithium battery industry is wet coating, and the solvent or glue in the slurry will flow through the micropores to the reverse side and stick to the coating roller, causing the coating machine to be unable to produce. In addition, there are no reports of microporous aluminum foil on the market. Summary of the invention

[0004] In order to solve the above problems, the present invention provides a microporous current collector and a preparation method thereof.

[0005] In a first aspect, the present invention provides a microporous current collector, which includes a current collector substrate, the surface of which is provided with evenly distributed protrusions and pits, and the top of the protrusion is provided with a small hole with a diameter of 10 to 50 nm; the current collector substrate includes an aluminum foil substrate or a copper foil substrate.

[0006] Furthermore, the horizontal spacing D between the bottoms of adjacent pits is 40 to 240 μm, the maximum depth B of the pits is 4 to 20 μm, the maximum horizontal width C of the pits is 10 to 40 μm, and the arc radius R of the pits is 1 to 5 μm.

[0007] Furthermore, the size parameters of the protrusions include: a ratio of the maximum height to the maximum diameter of the protrusions of 1:4 to 1:10; the maximum height of the protrusions is 4 to 20 um, the maximum diameter of the protrusions is 10 to 40 um, and the horizontal spacing between the bottoms of adjacent protrusions is 40 to 240 um.

[0008] Furthermore, the horizontal distance between the adjacent bottoms of the pits and the tops of the protrusions is 20 to 120 μm.

[0009] In a second aspect, the present invention provides a method for preparing the microporous current collector according to any one of the first aspects, the preparation method comprising the following steps:

[0010] obtaining a current collector substrate;

[0011] The current collector substrate is subjected to a first processing to obtain a micro-shaped current collector substrate having protrusions and pits evenly distributed on the surface;

[0012] The microporous current collector substrate is heated and stretched to obtain the microporous current collector.

[0013] Furthermore, the step of subjecting the current collector substrate to a first processing to obtain a micro-shaped current collector substrate with evenly distributed protrusions and pits on the surface includes the following process:

[0014] First, use a laser to micro-shape the required shape of the current collector substrate on a steel roller with a diameter of φ50mm~2000mm and a length of 100mm~2000mm. There are two micro-shaped steel rollers. The steel roller after micro-shaping is called a forming device. Then the forming device is installed on a rolling mill; the current collector substrate passes between the forming devices, the gap between the upper and lower forming devices is adjusted, pressure is applied to the forming device, and the surface shape of the forming device is copied to the current collector substrate. The current collector substrate after shaping is called a micro-shaped current collector substrate.

[0015] Furthermore, when the current collector substrate is an aluminum foil substrate, the working condition parameters of the heating stretching include: five-stage heating; the temperature of the first stage heating is 100±50°C; the temperature of the second stage heating is 300±50°C; the temperature of the third stage heating is 500±50°C; the temperature of the fourth stage heating is 300±50°C; the temperature of the fifth stage heating is 100±50°C;

[0016] When the current collector substrate is a copper foil substrate, the working condition parameters of the heating and stretching include: five-stage heating; the first stage is heated at 100±50°C; the second stage is heated at 500±50°C; the third stage is heated at 900±50°C; the fourth stage is heated at 500±50°C; and the fifth stage is heated at 100±50°C.

[0017] Furthermore, when the current collector substrate is an aluminum foil substrate, the heating and stretching tension is 100±50 MPa; when the current collector substrate is a copper foil substrate, the heating and stretching tension is 150±50 MPa.

[0018] Furthermore, the step of heating and stretching the micro-shaped current collector substrate to obtain the microporous current collector includes the following process:

[0019] The micro-shaped current collector substrate is unwound from the unwinding shaft, and then sequentially passed through the tension control roller to adjust to the preset heating and stretching tension value and five-stage heating, and finally rolled up on the winding shaft to obtain the microporous current collector.

[0020] The above technical solution provided by the embodiment of the present invention has at least the following advantages compared with the prior art:

[0021] The embodiment of the present invention provides a microporous current collector and a preparation method thereof. The microporous current collector provided by the present invention utilizes the principle of the tip effect to shape micropores with a diameter of 10 to 50 nm at the tip of the micro-shaped current collector protrusion. The positive electrode slurry or the negative electrode slurry cannot penetrate through the micropores, and lithium ions can migrate freely in the micropores, thereby solving the problems of uneven coating and lithium deposition during battery charging and discharging in the prior art. Specifically:

[0022] 1) The microporous current collector provided by the present invention has a micropore diameter of 10 to 50 nm. When coated, the positive electrode slurry or the negative electrode slurry has a high viscosity and a large surface tension, and cannot penetrate from the A side of the microporous current collector to the B side of the microporous current collector through the micropores. However, after being assembled into a battery cell and injected with electrolyte, the electrolyte has a low viscosity and a small surface tension, and can penetrate from the A side of the microporous current collector to the B side of the microporous current collector through the micropores; the ion diameter is less than 1 nm, and the pore diameter of 10 to 50 nm is sufficient for a large number of ions to pass through at the same time.

[0023] 2) The principle of the tip effect is used in the preparation process of the microporous current collector provided by the present invention, such as Figure 8 As shown, when the micro-shaped current collector passes through the heating furnace, heat will gather at the tip of the protrusion. When stretched, the tension and heat will gather at the tip at the same time, stretching a small hole at the tip. The aperture of the micropore can be controlled by controlling the ratio of the protrusion height and the diameter on the surface of the micro-shaped current collector. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0025] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0026] Figure 1 It is a schematic diagram of positive and negative electrode sheets in the prior art;

[0027] Figure 2 It is a schematic diagram of the application of microporous copper foil in the prior art;

[0028] Figure 3 The surface morphology of the micro-shaped aluminum foil in the present invention is Figure 1 ;

[0029] Figure 4 The surface morphology of the micro-shaped aluminum foil in the present invention is Figure 2 ;

[0030] Figure 5 This is a surface morphology diagram of the micro-shaped copper foil in the present invention;

[0031] Figure 6 It is a schematic diagram of protrusions and pits of the micro-shaped current collector in the present invention and a partial enlargement;

[0032] Figure 7 Schematic diagram of the processing and stretching of the micro-shaped current collector in the present invention;

[0033] Figure 8 It is a schematic diagram of the processing and stretching technology principle of the micro-shaped current collector in the present invention;

[0034] Fig. 9 Schematic diagram of the technical principle of the microporous current collector used in the present invention Figure 1 ;

[0035] Fig.10 Schematic diagram of the technical principle of the microporous current collector used in the present invention Figure 2 ;

[0036] Figure 1 Middle: 101-coating on the negative electrode A side, 102-copper foil, 103-coating on the negative electrode B side, 104-diaphragm, 105-coating on the positive electrode A side, 106-aluminum foil, 107-coating on the positive electrode B side, 108-pile-up caused by uneven coating;

[0037] Figure 2Middle: 201-coatings on the negative electrode A surface 2, 202-copper foil 2, 203-coatings on the negative electrode B surface 2, 204-diaphragm 2, 205-coatings on the positive electrode A surface 2, 206-aluminum foil 2, 207-coatings on the positive electrode B surface 2, 208-pile-up caused by uneven coating 2; 209-micropores;

[0038] Figure 6 Middle: 401-protrusion, 402-pit, B-maximum depth B of the pit, C-maximum horizontal width of the pit, D-horizontal spacing between the bottoms of adjacent pits, R-arc radius of the pit;

[0039] Figure 7 Middle: 501- unwinding shaft, 502- tension control roller, 503- rewinding shaft;

[0040] Figure 8 Middle: 601- micro-shaped current collector, 602- micro-shaped protrusions, 603- heat and force. DETAILED DESCRIPTION

[0041] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0042] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or prepared by existing methods.

[0043] In a first aspect, the present invention provides a microporous current collector, which includes a current collector substrate, the surface of which is provided with evenly distributed protrusions and pits, and the top of the protrusion is provided with a small hole with a diameter of 10 to 50 nm; the current collector substrate includes an aluminum foil substrate or a copper foil substrate.

[0044] An embodiment of the present invention provides a microporous current collector. The microporous current collector provided by the present invention utilizes the principle of the tip effect to shape micropores with a diameter of 10 to 50 nm at the tip of the micro-shaped current collector protrusion. Positive electrode slurry or negative electrode slurry cannot penetrate through the micropores, and lithium ions can migrate freely in the micropores, thereby solving the problems of uneven coating and lithium deposition during battery charging and discharging in the prior art.

[0045] In some specific embodiments, when the current collector substrate is an aluminum foil substrate, the microporous current collector is a microporous aluminum foil, the microporous aluminum foil comprises an aluminum foil substrate, the surface of the aluminum foil substrate is provided with evenly distributed protrusions and pits, and the top of the protrusion is provided with a small hole with a diameter of 10 to 50 nm;

[0046] When the current collector substrate is a copper foil substrate, the microporous current collector is a microporous copper foil, which includes a copper foil substrate, the surface of which is provided with evenly distributed protrusions and pits, and the top of the protrusion is provided with a small hole with a diameter of 10 to 50 nm.

[0047] In some specific embodiments, the horizontal spacing D between the bottoms of adjacent pits is 40-240 μm, the maximum depth B of the pits is 4-20 μm, the maximum horizontal width C of the pits is 10-40 μm, and the arc radius R of the pits is 1-5 μm.

[0048] In some specific embodiments, the size parameters of the protrusions include: a ratio of the maximum height to the maximum diameter of the protrusions is 1:10 to 1:4; the maximum height of the protrusions is 4 to 20 um, the maximum diameter of the protrusions is 10 to 40 um, and the horizontal spacing between the bottoms of adjacent protrusions is 40 to 240 um.

[0049] In some specific embodiments, the horizontal distance between the adjacent bottoms of the pits and the tops of the protrusions is 20-120 μm.

[0050] In a second aspect, based on the same inventive concept, the present invention provides a method for preparing the microporous current collector according to any one of the first aspects, the preparation method comprising the following steps:

[0051] obtaining a current collector substrate;

[0052] The current collector substrate is subjected to a first processing to obtain a micro-shaped current collector substrate having protrusions and pits evenly distributed on the surface;

[0053] The microporous current collector substrate is heated and stretched to obtain the microporous current collector.

[0054] In some specific embodiments, the step of subjecting the current collector substrate to a first processing to obtain a micro-shaped current collector substrate having protrusions and pits evenly distributed on the surface includes the following process:

[0055] First, a laser is used to micro-shape the required shape of the current collector substrate on a steel roller with a diameter of φ50mm to 2000mm and a length of 100mm to 2000mm. There are two micro-shaped steel rollers. The steel roller after micro-shaping is called a forming device. Then the forming device is installed on a rolling mill; the current collector substrate passes through the forming devices, the gap between the upper and lower forming devices is adjusted, and pressure is applied to the forming device to copy the surface shape of the forming device to the current collector substrate. The current collector substrate after shaping is called a micro-shaped current collector substrate. In some specific embodiments, the step of heating and stretching the micro-shaped aluminum foil substrate includes the following process:

[0056] A. Heating and stretching environment atmosphere control: the heating furnace is filled with argon gas for protection;

[0057] B. Heating temperature control: the first section is heated at 100±50℃; the second section is heated at 300±50℃; the third section is heated at 500±50℃; the fourth section is heated at 300±50℃; the fifth section is heated at 100±50℃.

[0058] C. The micro-shaped current collector is unwound from the unwinding reel 501, heated through the first to fifth sections, and wound on the winding reel 503. The tension of the heating and stretching is controlled by the tension control roller 502 to shape micropores with a pore size of 10 to 50 nm at the tip of the micro-shaped aluminum foil. The tension is set to: 100±50MPa.

[0059] In some specific embodiments, the surface morphology of the micro-shaped aluminum foil is as follows Figure 3 and Figure 4 As shown, the surface of the micro-shaped aluminum foil has evenly distributed protrusions and pits.

[0060] In some specific embodiments, the width of the micro-shaped aluminum foil is 300 mm.

[0061] In some specific embodiments, the protrusions and pits of the micro-shaped aluminum foil and the partial enlarged schematic diagram are as shown in Figure 6 As shown, Figure 6 Parameters such as B, C, D, and R can be customized according to actual product requirements.

[0062] In some specific embodiments, the working condition parameters of the heating stretching include: five-stage heating; the heating temperature of the first stage is 100±50℃; the heating temperature of the second stage is 300±50℃; the heating temperature of the third stage is 500±50℃; the heating temperature of the fourth stage is 300±50℃; the heating temperature of the fifth stage is 100±50℃.

[0063] In some specific embodiments, the tension of the heated stretching is 100±50 MPa.

[0064] In some specific embodiments, the surface morphology of the micro-shaped copper foil is as follows Figure 5As shown. Heating stretching includes the following processes:

[0065] A. Heating and stretching environment atmosphere control: the heating furnace is filled with argon gas for protection;

[0066] B. Heating temperature control: the first section is heated at 100±50℃; the second section is heated at 500±50℃; the third section is heated at 900±50℃; the fourth section is heated at 500±50℃; the fifth section is heated at 100±50℃.

[0067] C. The micro-shaped current collector is unwound from the unwinding reel 501, heated through the first to fifth sections, and wound on the winding reel 503. The tension of the heating and stretching is controlled by the tension control roller 502 to shape micropores with a pore size of 10 to 50 nm at the tip of the micro-shaped aluminum foil. The tension is set to: 150±50MPa.

[0068] In some specific embodiments, Figure 7 As shown, the step of heating and stretching the micro-shaped aluminum foil substrate to obtain the microporous current collector includes the following process:

[0069] The micro-shaped aluminum foil substrate is unwound from the unwinding shaft, and then sequentially passed through the tension control roller to adjust to the preset heating and stretching tension value and five-stage heating, and finally rolled up on the winding shaft to obtain the microporous current collector.

[0070] In some specific embodiments, the schematic diagram of the processing and stretching technology principle of the micro-shaped aluminum foil in the present invention is as follows Figure 8 As shown, when the micro-shaped aluminum foil passes through the heating furnace, the heat will be concentrated at the protruding tip. When it is stretched, the tension and heat will be concentrated at the tip at the same time, stretching a small hole at the tip.

[0071] In some specific embodiments, the microporous current collector of the present invention is used as follows Fig. 9 and Fig.10 1) Through holes allow lithium ions to pass through, solving the lithium deposition problem: Fig. 9 It can be seen that the top of the micro-shaped aluminum foil protrusion is in a closed-cell state. After coating the positive electrode material on both sides, the coating amount at A and B is relatively balanced; the coating amount at C1 and D1 is unbalanced, and the coating amount at D1 is more than that at C1. When the battery is charged, there is more positive electrode material at D1, and the corresponding negative electrode material is relatively insufficient. The deintercalated lithium ions are not absorbed by enough negative electrode materials. At C1, there is too little positive electrode material, and the corresponding negative electrode material is not fully utilized. 2) From Fig.10 It can be seen that the top of the microporous current collector protrusion is in a through-hole state. After coating the negative electrode material on both sides, the coating amount at A and B is relatively balanced;

[0072] The coating amount at C2 and D2 is unbalanced, and the coating amount at D2 is more than that at C2. When the battery is charged, the negative electrode material corresponding to C2 cannot fully absorb the lithium ions migrated from the positive electrode sheet, but the excess lithium ions will pass through the through-holes and recombine with the negative electrode material corresponding to C2; when the positive electrode sheet is unevenly coated, the excess lithium ions will also pass through the through-holes to prevent lithium precipitation. Similarly, when the current collector substrate is a copper foil substrate, the microporous current collector is a microporous copper foil, which is similar.

[0073] It should be noted that the component raw materials involved in the microporous current collector and the preparation method thereof provided in the embodiments of the present invention, unless otherwise specified or specified, can be directly commercially available products or homemade using existing public preparation methods; at the same time, the steps and parameters involved, unless otherwise specified or specified, can be carried out according to existing processing techniques or directly using existing equipment, and the present invention document will not describe them one by one.

[0074] The present invention will be further described below in conjunction with specific examples. It should be understood that these examples are intended only to illustrate the present invention and are not intended to limit the scope of the present invention. The experimental methods in the following examples that do not specify specific conditions are usually measured according to national standards. If there is no corresponding national standard, then the conditions recommended by the manufacturer are followed.

[0075] Example 1

[0076] This example provides a microporous current collector, the microporous current collector comprises a current collector substrate, the surface of the current collector substrate is provided with evenly distributed protrusions and pits, the top of the protrusion is provided with a small hole with a diameter of 10 to 50 nm; the current collector substrate is an aluminum foil substrate;

[0077] The horizontal spacing D between the bottoms of adjacent pits is 100 μm, the maximum depth B of the pits is 12 μm, the maximum horizontal width C of the pits is 48 μm, and the arc radius R of the pits is 1.5 μm;

[0078] The size parameters of the protrusions include: a ratio of the height to the diameter of the protrusions is 1:4; the height of the protrusions is 12um, the diameter of the protrusions is 48um, and the horizontal spacing between the bottoms of adjacent protrusions is 100um.

[0079] The preparation method of the microporous current collector comprises the following steps:

[0080] Step (1): the aluminum foil substrate is subjected to a first processing to obtain a micro-shaped aluminum foil with a width of 300 mm and evenly distributed protrusions and pits on the surface; specifically, the process includes the following steps: first, a laser is used to micro-shape the aluminum foil into a desired shape on a steel roller with a diameter of φ50 mm to 2000 mm and a length of 100 mm to 2000 mm, two micro-shaped steel rollers are provided, and the micro-shaped steel rollers are called forming devices, and then the forming devices are installed on a rolling mill; the aluminum foil passes between the forming devices, the gap between the upper and lower forming devices is adjusted, and pressure is applied to the forming device to copy the surface shape of the forming device onto the aluminum foil, and the aluminum foil after shaping is called micro-shaped aluminum foil;

[0081] Step (2): heating and stretching the micro-shaped aluminum foil to obtain the microporous current collector; specifically comprising the following process:

[0082] A. Heating and stretching environment atmosphere control: the heating furnace is filled with argon gas for protection;

[0083] B. Heating temperature control: the first section is heated at 100±3℃; the second section is heated at 300±3℃; the third section is heated at 500±3℃; the fourth section is heated at 300±3℃; the fifth section is heated at 100±3℃;

[0084] C. The micro-shaped current collector is unwound from the unwinding reel, heated through the first to fifth sections, and wound on the winding reel. The tension of heating and stretching is controlled by the tension control roller to shape micropores at the tip of the micro-shaped aluminum foil. The tension is set to: 100±3MPa.

[0085] Example 2

[0086] This example provides a microporous current collector, the microporous current collector comprises a current collector substrate, the surface of the current collector substrate is provided with evenly distributed protrusions and pits, the top of the protrusion is provided with a small hole with a diameter of 10 to 50 nm; the current collector substrate is an aluminum foil substrate;

[0087] The horizontal spacing D between the bottoms of adjacent pits is 36 μm, the maximum depth B of the pits is 12 μm, the maximum horizontal width C of the pits is 100 μm, and the arc radius R of the pits is 1.5 μm;

[0088] The size parameters of the protrusions include: a ratio of the height to the diameter of the protrusions is 1:3; the height of the protrusions is 12um, the diameter of the protrusions is 36um, and the horizontal spacing between the bottoms of adjacent protrusions is 100um.

[0089] The preparation method of the microporous current collector comprises the following steps:

[0090] Step (1): the aluminum foil substrate is subjected to a first processing to obtain a micro-shaped aluminum foil with a width of 300 mm and evenly distributed protrusions and pits on the surface; specifically, the process includes the following steps: first, a laser is used to micro-shape the aluminum foil into a desired shape on a steel roller with a diameter of φ50 mm to 2000 mm and a length of 100 mm to 2000 mm, two micro-shaped steel rollers are provided, and the micro-shaped steel rollers are called forming devices, and then the forming devices are installed on a rolling mill; the aluminum foil passes between the forming devices, the gap between the upper and lower forming devices is adjusted, and pressure is applied to the forming device to copy the surface shape of the forming device onto the aluminum foil, and the aluminum foil after shaping is called micro-shaped aluminum foil;

[0091] Step (2): heating and stretching the micro-shaped aluminum foil to obtain the microporous current collector; specifically comprising the following process:

[0092] A. Heating and stretching environment atmosphere control: the heating furnace is filled with argon gas for protection;

[0093] B. Heating temperature control: the first section is heated at 100±3℃; the second section is heated at 300±3℃; the third section is heated at 500±3℃; the fourth section is heated at 300±3℃; the fifth section is heated at 100±3℃;

[0094] C. The micro-shaped current collector is unwound from the unwinding reel, heated through the first to fifth sections, and wound on the winding reel. The tension of heating and stretching is controlled by the tension control roller to shape micropores at the tip of the micro-shaped aluminum foil. The tension is set to: 100±3MPa.

[0095] Example 3

[0096] This example provides a microporous current collector, the microporous current collector comprises a current collector substrate, the surface of the current collector substrate is provided with evenly distributed protrusions and pits, the top of the protrusion is provided with a small hole with a diameter of 10 to 50 nm; the current collector substrate is an aluminum foil substrate;

[0097] The horizontal spacing D between the bottoms of adjacent pits is 100 μm, the maximum depth B of the pits is 12 μm, the maximum horizontal width C of the pits is 24 μm, and the arc radius R of the pits is 1.5 μm;

[0098] The size parameters of the protrusions include: a ratio of the height to the diameter of the protrusions is 1:2; the height of the protrusions is 12um, the diameter of the protrusions is 24um, and the horizontal spacing between the bottoms of adjacent protrusions is 100um.

[0099] The preparation method of the microporous current collector comprises the following steps:

[0100] Step (1): the aluminum foil substrate is subjected to a first processing to obtain a micro-shaped aluminum foil with a width of 300 mm and evenly distributed protrusions and pits on the surface; specifically, the process includes the following steps: first, a laser is used to micro-shape the aluminum foil into a desired shape on a steel roller with a diameter of φ50 mm to 2000 mm and a length of 100 mm to 2000 mm, two micro-shaped steel rollers are provided, and the micro-shaped steel rollers are called forming devices, and then the forming devices are installed on a rolling mill; the aluminum foil passes between the forming devices, the gap between the upper and lower forming devices is adjusted, and pressure is applied to the forming device to copy the surface shape of the forming device onto the aluminum foil, and the aluminum foil after shaping is called micro-shaped aluminum foil;

[0101] Step (2): heating and stretching the micro-shaped aluminum foil to obtain the microporous current collector; specifically comprising the following process:

[0102] A. Heating and stretching environment atmosphere control: the heating furnace is filled with argon gas for protection;

[0103] B. Heating temperature control: the first section is heated at 100±3℃; the second section is heated at 300±3℃; the third section is heated at 500±3℃; the fourth section is heated at 300±3℃; the fifth section is heated at 100±3℃;

[0104] C. The micro-shaped current collector is unwound from the unwinding reel, heated through the first to fifth sections, and wound on the winding reel. The tension of heating and stretching is controlled by the tension control roller to shape micropores at the tip of the micro-shaped aluminum foil. The tension is set to: 100±3MPa.

[0105] Example 4

[0106] This example provides a microporous current collector, the microporous current collector comprises a current collector substrate, the surface of the current collector substrate is provided with evenly distributed protrusions and pits, the top of the protrusion is provided with a small hole with a diameter of 10 to 50 nm; the current collector substrate is an aluminum foil substrate;

[0107] The horizontal spacing D between the bottoms of adjacent pits is 100 μm, the maximum depth B of the pits is 12 μm, the maximum horizontal width C of the pits is 12 μm, and the arc radius R of the pits is 1.5 μm;

[0108] The size parameters of the protrusions include: a ratio of the height to the diameter of the protrusions is 1:1; the height of the protrusions is 12um, the diameter of the protrusions is 12um, and the horizontal spacing between the bottoms of adjacent protrusions is 100um.

[0109] The preparation method of the microporous current collector comprises the following steps:

[0110] Step (1): the aluminum foil substrate is subjected to a first processing to obtain a micro-shaped aluminum foil with a width of 300 mm and evenly distributed protrusions and pits on the surface; specifically, the process includes the following steps: first, a laser is used to micro-shape the aluminum foil into a desired shape on a steel roller with a diameter of φ50 mm to 2000 mm and a length of 100 mm to 2000 mm, two micro-shaped steel rollers are provided, and the micro-shaped steel rollers are called forming devices, and then the forming devices are installed on a rolling mill; the aluminum foil passes between the forming devices, the gap between the upper and lower forming devices is adjusted, and pressure is applied to the forming device to copy the surface shape of the forming device onto the aluminum foil, and the aluminum foil after shaping is called micro-shaped aluminum foil;

[0111] Step (2): heating and stretching the micro-shaped aluminum foil to obtain the microporous current collector; specifically comprising the following process:

[0112] A. Heating and stretching environment atmosphere control: the heating furnace is filled with argon gas for protection;

[0113] B. Heating temperature control: the first section is heated at 100±3℃; the second section is heated at 300±3℃; the third section is heated at 500±3℃; the fourth section is heated at 300±3℃; the fifth section is heated at 100±3℃;

[0114] C. The micro-shaped current collector is unwound from the unwinding reel, heated through the first to fifth sections, and wound on the winding reel. The tension of heating and stretching is controlled by the tension control roller to shape micropores at the tip of the micro-shaped aluminum foil. The tension is set to: 100±3MPa.

[0115] Example 5

[0116] This example provides a microporous current collector, the microporous current collector comprises a current collector substrate, the surface of the current collector substrate is provided with evenly distributed protrusions and pits, the top of the protrusion is provided with a small hole with a diameter of 10 to 50 nm; the current collector substrate is an aluminum foil substrate;

[0117] The horizontal spacing D between the bottoms of adjacent pits is 6 μm, the maximum depth B of the pits is 12 μm, the maximum horizontal width C of the pits is 100 μm, and the arc radius R of the pits is 1.5 μm;

[0118] The size parameters of the protrusions include: a ratio of the height to the diameter of the protrusions is 2:1; the height of the protrusions is 12um, the diameter of the protrusions is 6um, and the horizontal spacing between the bottoms of adjacent protrusions is 100um.

[0119] The preparation method of the microporous current collector comprises the following steps:

[0120] Step (1): the aluminum foil substrate is subjected to a first processing to obtain a micro-shaped aluminum foil with a width of 300 mm and evenly distributed protrusions and pits on the surface; specifically, the process includes the following steps: first, a laser is used to micro-shape the aluminum foil into a desired shape on a steel roller with a diameter of φ50 mm to 2000 mm and a length of 100 mm to 2000 mm, two micro-shaped steel rollers are provided, and the micro-shaped steel rollers are called forming devices, and then the forming devices are installed on a rolling mill; the aluminum foil passes between the forming devices, the gap between the upper and lower forming devices is adjusted, and pressure is applied to the forming device to copy the surface shape of the forming device onto the aluminum foil, and the aluminum foil after shaping is called micro-shaped aluminum foil;

[0121] Step (2): heating and stretching the micro-shaped aluminum foil to obtain the microporous current collector; specifically comprising the following process:

[0122] A. Heating and stretching environment atmosphere control: the heating furnace is filled with argon gas for protection;

[0123] B. Heating temperature control: the first section is heated at 100±3℃; the second section is heated at 300±3℃; the third section is heated at 500±3℃; the fourth section is heated at 300±3℃; the fifth section is heated at 100±3℃;

[0124] C. The micro-shaped current collector is unwound from the unwinding reel, heated through the first to fifth sections, and wound on the winding reel. The tension of heating and stretching is controlled by the tension control roller to shape micropores at the tip of the micro-shaped aluminum foil. The tension is set to: 100±3MPa.

[0125] Embodiment 6:

[0126] The width of the micro-shaped copper foil substrate is 300mm, the protrusion height is 12um, the protrusion diameter is 6um, the protrusion spacing is 140um, and the heating and stretching are carried out according to 4.2.3.1. The tension is set to: 150±3MPa, the first section is heated at 100±3℃; the second section is heated at 200±3℃; the third section is heated at 500±3℃; the fourth section is heated at 200±3℃; the fifth section is heated at 100±3℃.

[0127] Embodiment 7:

[0128] The width of the micro-shaped copper foil substrate is 300mm, the protrusion height is 12um, the protrusion diameter is 6um, and the protrusion spacing is 140um. Heat and stretch according to 4.2.3.1. The tension is set to: 150±3MPa, the first section is heated at 100±3℃; the second section is heated at 250±3℃; the third section is heated at 600±3℃; the fourth section is heated at 250±3℃; the fifth section is heated at 100±3℃.

[0129] Embodiment 8:

[0130] The width of the micro-shaped copper foil substrate is 300mm, the protrusion height is 12um, the protrusion diameter is 6um, the protrusion spacing is 140um, and the heating and stretching are performed according to 4.2.3.1. The tension is set to: 150±3MPa, the first section is heated at 100±3℃; the second section is heated at 300±3℃; the third section is heated at 700±3℃; the fourth section is heated at 300±3℃; the fifth section is heated at 100±3℃.

[0131] Embodiment 9:

[0132] The width of the micro-shaped copper foil substrate is 300mm, the protrusion height is 12um, the protrusion diameter is 6um, and the protrusion spacing is 140um. Heat and stretch according to 4.2.3.1. The tension is set to: 150±3MPa, the first section is heated at 100±3℃; the second section is heated at 400±3℃; the third section is heated at 800±3℃; the fourth section is heated at 400±3℃; the fifth section is heated at 100±3℃.

[0133] Embodiment 10:

[0134] The width of the micro-shaped copper foil substrate is 300mm, the protrusion height is 12um, the protrusion diameter is 6um, the protrusion spacing is 140um, and the heating and stretching are carried out according to 4.2.3.1. The tension is set to: 150±3MPa, the first section is heated at 100±3℃; the second section is heated at 500±3℃; the third section is heated at 900±3℃; the fourth section is heated at 500±3℃; the fifth section is heated at 100±3℃.

[0135] Comparative Example 1

[0136] This example provides a microporous current collector, the microporous current collector comprises an aluminum foil substrate, the surface of the aluminum foil substrate is provided with evenly distributed protrusions and pits, and the top of the protrusion is provided with a small hole with a diameter of 0 nm;

[0137] The horizontal spacing D between the bottoms of adjacent pits is 240 μm, the maximum depth B of the pits is 12 μm, the maximum horizontal width C of the pits is 120 μm, and the arc radius R of the pits is 5 μm;

[0138] The size parameters of the protrusions include: the ratio of the height and the diameter of the protrusions is 1:10; the height of the protrusions is 12um, the diameter of the protrusions is 120um, and the horizontal spacing between the bottoms of adjacent protrusions is 240um.

[0139] The preparation method of the microporous current collector comprises the following steps:

[0140] Step (1): the aluminum foil substrate is subjected to a first processing to obtain a micro-shaped aluminum foil with a width of 300 mm and evenly distributed protrusions and pits on the surface; specifically, the process includes the following steps: first, a laser is used to micro-shape the aluminum foil into a desired shape on a steel roller with a diameter of φ50 mm to 2000 mm and a length of 100 mm to 2000 mm, two micro-shaped steel rollers are provided, and the micro-shaped steel rollers are called forming devices, and then the forming devices are installed on a rolling mill; the aluminum foil passes between the forming devices, the gap between the upper and lower forming devices is adjusted, and pressure is applied to the forming device to copy the surface shape of the forming device onto the aluminum foil, and the aluminum foil after shaping is called micro-shaped aluminum foil;

[0141] Step (2): heating and stretching the micro-shaped aluminum foil to obtain the microporous current collector; specifically comprising the following process:

[0142] A. Heating and stretching environment atmosphere control: the heating furnace is filled with argon gas for protection;

[0143] B. Heating temperature control: the first section is heated at 100±3℃; the second section is heated at 300±3℃; the third section is heated at 500±3℃; the fourth section is heated at 300±3℃; the fifth section is heated at 100±3℃;

[0144] C. The micro-shaped current collector is unwound from the unwinding reel, heated through the first to fifth sections, and wound on the winding reel. The tension of heating and stretching is controlled by the tension control roller to shape micropores at the tip of the micro-shaped aluminum foil. The tension is set to: 100±3MPa.

[0145] Comparative Example 2:

[0146] The width of the micro-shaped copper foil substrate is 300mm, the protrusion height is 12um, the protrusion diameter is 6um, and the protrusion spacing is 140um. Heat stretching is performed according to 4.2.3.1, and the tension is set to: 150±3MPa, the first section is room temperature; the second section is room temperature; the third section is room temperature; the fourth section is room temperature; the fifth section is room temperature.

[0147] Comparative Example 3:

[0148] The width of the conventional copper foil substrate is 300mm. During electrolysis, the substrate winding speed is 2m / min. The heating and stretching are performed according to 4.2.3.1. The tension is set to: 150±3MPa. The first section is heated to 100±3℃; the second section is heated to 500±3℃; the third section is heated to 900±3℃; the fourth section is heated to 500±3℃; and the fifth section is heated to 100±3℃.

[0149] Comparative Example 4:

[0150] The width of the micro-shaped copper foil substrate is 300mm, the protrusion height is 12um, the protrusion diameter is 6um, the protrusion spacing is 140um, and the heating and stretching are carried out according to 4.2.3.1. The tension is set to: 150±3MPa, the first section is heated at 100±3℃; the second section is heated at 600±3℃; the third section is heated at 1000±3℃; the fourth section is heated at 600±3℃; the fifth section is heated at 100±3℃.

[0151] The key parameters of the microporous current collectors provided in Examples 1 to 5 and Comparative Example 1 are shown in Table 1.

[0152] Table 1

[0153]

[0154] Examples 6 to 10 and Comparative Examples 2 to 3 provide a microporous current collector, the substrate of which is a copper foil substrate, and its key parameters are shown in Table 2.

[0155] Table 2

[0156]

[0157]

[0158] Test Example 1

[0159] In this example, the microporous current collectors provided in Examples 1 to 5 and Comparative Example 1 were subjected to performance testing, specifically including the following process:

[0160] A. Lithium-ion electrolyte permeability test

[0161] Use a pipette to draw electrolyte drops onto the upper surface of the microporous current collector, stick a piece of pH test paper on the lower surface of the microporous current collector, and observe the color change time of the pH test paper.

[0162] B. Slurry permeability test

[0163] Weigh 5.1 g PVDF and dissolve it in 67.8 g NMP, stir for 2 h, add 81.6 g CNT, stir for 2 h, add 500.8 g ternary material, add 24.7 g NMP, stir for 3 h, and prepare the positive electrode slurry.

[0164] Use a small spoon to transfer 1 spoon of slurry to the upper surface of the microporous current collector, stick a piece of pH test paper on the lower surface of the microporous current collector, and observe the color change time of the pH test paper.

[0165] C. Tensile strength test

[0166] Use a sampler to cut a microporous current collector with a length*width of 100*25mm. For the room temperature tensile mechanical properties test, the gauge length is 50mm, the test rate is 5mm / min, and the tensile strength is recorded.

[0167] The test results are shown in Table 3.

[0168] Table 3

[0169]

[0170] It can be seen from Table 3 that from the results of Example 1 to Example 5, as the ratio of the protrusion height to the diameter becomes larger and larger, the time for the electrolyte to penetrate the microporous current collector becomes shorter and shorter, indicating that the micropore diameter is getting larger and larger, verifying that the sharper the protrusion, the more obvious the tip effect; the slurry cannot penetrate the microporous current collector; there is no obvious change in the tensile strength; in Comparative Example 1, the ratio of the protrusion height to the diameter is too small, the tip effect is not obvious, the micropores are too small, and it does not have the characteristics of a microporous current collector.

[0171] Test Example 2

[0172] In this example, the performance of the microporous current collectors provided in Examples 6 to 10 and Comparative Examples 2 to 4 was tested.

[0173] A. Lithium-ion electrolyte permeability test

[0174] Use a pipette to draw electrolyte drops onto the upper surface of the microporous copper foil, stick a piece of pH test paper on the lower surface of the microporous copper foil, and observe the color change time of the pH test paper.

[0175] B. Slurry permeability test

[0176] Weigh 95.1 g of graphite, 1 g of carbon black, 1.6 g of CMC, 2.3 g of SBR (4.6 g of emulsion), and 120 g of water, stir for 3 h, and prepare a negative electrode slurry.

[0177] Use a small spoon to transfer 1 spoon of slurry to the upper surface of the microporous copper foil, stick a piece of pH test paper on the lower surface of the microporous copper foil, and observe the color change time of the pH test paper.

[0178] C. Tensile strength test

[0179] Use a sampler to cut a microporous copper foil with a length*width of 100*25mm. For the room temperature tensile mechanical properties test, the gauge length is 50mm, the test rate is 5mm / min, and the tensile strength is recorded.

[0180] The test results are shown in Table 4.

[0181] Table 4

[0182]

[0183]

[0184] It can be seen from Table 4 that from the results of Example 6 to Example 10, as the heating temperature increases, the time for the electrolyte to penetrate the microporous copper foil becomes shorter and shorter, indicating that the micropore diameter is getting larger and larger; the slurry cannot penetrate the microporous copper foil; there is no obvious change in tensile strength; Comparative Example 2 is not heated, no micropores are generated, and it does not have the characteristics of a microporous copper foil; Comparative Example 3 is a conventional copper foil, has no tip effect, cannot generate micropores, and does not have the characteristics of a microporous copper foil; Comparative Example 4 is heated at too high a temperature, the micropores are too large, the slurry will penetrate the micropores during coating, and normal production cannot be achieved.

[0185] Various embodiments of the present invention may be presented in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity, and should not be understood as a rigid limitation on the scope of the present invention; therefore, the range description should be considered to have specifically disclosed all possible sub-ranges and single numerical values ​​within the range. For example, the range description from 1 to 6 should be considered to have specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers within the range, such as 1, 2, 3, 4, 5 and 6, which apply regardless of the range. In addition, whenever a numerical range is indicated herein, it is meant to include any cited number (fractional or integer) within the indicated range.

[0186] The foregoing is merely a specific embodiment of the present invention, which enables those skilled in the art to understand or implement the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A microporous current collector, characterized in that: The microporous current collector comprises a current collector substrate, the surface of the current collector substrate is provided with evenly distributed protrusions and pits, the top of the protrusion is provided with a small hole with a diameter of 10 to 50 nm; the current collector substrate comprises an aluminum foil substrate or a copper foil substrate.

2. The microporous current collector according to claim 1, characterized in that: The horizontal spacing D between the bottoms of adjacent pits is 40 to 240 μm, the maximum depth B of the pits is 4 to 20 μm, the maximum horizontal width C of the pits is 10 to 40 μm, and the arc radius R of the pits is 1 to 5 μm.

3. The microporous current collector according to claim 1, characterized in that: The size parameters of the protrusions include: a ratio of the maximum height to the maximum diameter of the protrusions of 1:4 to 1:10; the maximum height of the protrusions is 4 to 20 um, the maximum diameter of the protrusions is 10 to 40 um, and the horizontal spacing between the bottoms of adjacent protrusions is 40 to 240 um.

4. The microporous current collector according to claim 1, characterized in that: The horizontal distance between the adjacent bottoms of the pits and the tops of the protrusions is 20 to 120 μm.

5. A method for preparing a microporous current collector according to any one of claims 1 to 4, characterized in that: The preparation method comprises the following steps: obtaining a current collector substrate; The current collector substrate is subjected to a first processing to obtain a micro-shaped current collector substrate having protrusions and pits evenly distributed on the surface; The microporous current collector substrate is heated and stretched to obtain the microporous current collector.

6. The method for preparing a microporous current collector according to claim 5, characterized in that: The step of performing a first processing on the current collector substrate to obtain a micro-shaped current collector substrate having protrusions and pits evenly distributed on the surface The process includes: First, use a laser to micro-shape the required shape of the current collector substrate on a steel roller with a diameter of φ50mm~2000mm and a length of 100mm~2000mm. There are two micro-shaped steel rollers. The steel roller after micro-shaping is called a forming device. Then the forming device is installed on a rolling mill; the current collector substrate passes between the forming devices, the gap between the upper and lower forming devices is adjusted, pressure is applied to the forming device, and the surface shape of the forming device is copied to the current collector substrate. The current collector substrate after shaping is called a micro-shaped current collector substrate.

7. The method for preparing a microporous current collector according to claim 5, characterized in that: When the current collector substrate is an aluminum foil substrate, the working condition parameters of the heating stretching include: five-stage heating; the temperature of the first stage heating is 100±50°C; the temperature of the second stage heating is 300±50°C; the temperature of the third stage heating is 500±50°C; the temperature of the fourth stage heating is 300±50°C; the temperature of the fifth stage heating is 100±50°C; When the current collector substrate is a copper foil substrate, the working condition parameters of the heating and stretching include: five-stage heating; the first stage is heated at 100±50°C; the second stage is heated at 500±50°C; the third stage is heated at 900±50°C; the fourth stage is heated at 500±50°C; and the fifth stage is heated at 100±50°C.

8. The method for preparing a microporous current collector according to claim 7, characterized in that: When the current collector substrate is an aluminum foil substrate, the heating and stretching tension is 100±50 MPa; when the current collector substrate is a copper foil substrate, the heating and stretching tension is 150±50 MPa.

9. The method for preparing a microporous current collector according to claim 8, characterized in that: The step of heating and stretching the micro-shaped current collector substrate to obtain the microporous current collector The process includes: The micro-shaped current collector substrate is unwound from the unwinding shaft, and then sequentially passed through the tension control roller to adjust to the preset heating and stretching tension value and five-stage heating, and finally rolled up on the winding shaft to obtain the microporous current collector.

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