Current collector with through hole structure, preparation method thereof, current collector hole forming device and application

Abstract

The invention provides a current collector with a through hole structure, a preparation method of the current collector, a current collector hole forming device and application. A plurality of through holes penetrating through the current collector along the thickness direction are formed in the current collector; the diameter of each through hole is 0.2 mm-3 mm, and the area ratio of the through holes in the current collector is 10%-30%. The plurality of through holes penetrating through the whole current collector are formed in the current collector, and the hole diameter and the area ratio of the through holes are limited, so that the mechanical property of the current collector can meet the use requirement, and the stripping force of the pole piece prepared on the basis of the current collector is remarkably improved; and moreover, the electrolyte infiltration time of the prepared battery is shortened from 3 days to 1 day, and the battery can be fully infiltrated, so that the cycle performance is further improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of battery materials, and in particular relates to a current collector with a through-hole structure, a preparation method thereof, a current collector pore-forming device and applications. Background Art

[0002] Current collectors play a key role in power systems and electronic devices. In batteries, battery packs or other related equipment, current collectors are mainly used to collect and conduct current to ensure that the current can be smoothly transmitted from the power source to the power-consuming equipment, or from one end of the equipment to the other. Currently, the more common current collectors are aluminum foil, copper foil and functional current collectors. Among them, aluminum foil is a relatively thick aluminum ingot that is rolled multiple times to a thickness of 10μm-20μm. Copper foil is thickened to a thickness of 6μm-10μm by electrolytic copper. Functional current collectors are formed by depositing a metal layer of about 1μm on both sides of polymer materials such as PET or PP.

[0003] The above three conventional current collectors (aluminum foil, copper foil and functional current collector) have the following disadvantages:

[0004] 1) The surface roughness of the current collector is not enough, and the peeling force of the produced electrode is low;

[0005] 2) The electrode is not wettable enough in the electrolyte. It takes 3 days for the large cylindrical battery to achieve electrolyte wetting.

[0006] 3) The battery cycle is not long.

[0007] Therefore, how to overcome the shortcomings of the above-mentioned current collectors and improve battery performance is a technical problem that needs to be solved urgently. Summary of the invention

[0008] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a current collector with a through-hole structure, a preparation method thereof, a current collector pore-forming device and application. The present invention provides a plurality of through-holes that penetrate the entire current collector in the current collector, and limits the hole diameter and area ratio of the through-holes. The peeling force of the pole piece prepared based on this is significantly improved, and the electrolyte infiltration time of the prepared battery is shortened from 3 days to 1 day for full infiltration, and the cycle performance is further improved.

[0009] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0010] In a first aspect, the present invention provides a current collector having a through-hole structure, wherein the current collector is provided with a plurality of through-holes penetrating the current collector along a thickness direction.

[0011] The diameter of the through hole is 0.2 mm-3 mm, and the area of ​​the through hole in the current collector accounts for 10%-30%.

[0012] The present invention provides a plurality of through holes penetrating the entire current collector in the current collector, and limits the hole diameter and area ratio of the through holes, so that the mechanical properties of the current collector can meet the use requirements. The peeling force of the pole piece prepared based on this is significantly improved, and the electrolyte infiltration time of the prepared battery is shortened from 3 days to 1 day for full infiltration, and the cycle performance is further improved.

[0013] In the present invention, the hole diameter of the through hole is 0.2mm-3mm, for example, it can be 0.2mm, 0.5mm, 1mm, 1.5mm, 2mm, 2.5mm or 3mm. Through holes with suitable hole diameters help to ensure the mechanical properties of the current collector while improving the energy density. If the hole diameter of the through hole is too small, the energy density and the pole piece peeling force will be limited; if the hole diameter of the through hole is too large, the tensile strength and elongation at break of the current collector will be reduced, resulting in the current collector being prone to problems such as broken tape, wrinkle deformation, etc. in subsequent production processes such as tape walking and rolling.

[0014] In the present invention, the area ratio of the through hole is 10%-30%, for example, it can be 10%, 15%, 20%, 25% or 30%. Through holes with an area ratio help to ensure the mechanical properties of the current collector while improving the energy density. If the area ratio of the through hole is too small, the energy density and the pole piece peeling force will be limited; if the area ratio of the through hole is too large, the tensile strength and elongation at break of the current collector will be reduced, resulting in the current collector being prone to problems such as broken tape, wrinkle deformation, etc. in subsequent production processes such as tape walking and rolling.

[0015] It should be noted that the above-mentioned "hole diameter" refers to the maximum diameter of the through hole. The area ratio of the through hole can be calculated by the following method: Take 1m 2 The current collector sample is taken, and the area of ​​all through holes in the current collector sample is calculated, and then the area ratio of the through holes is calculated.

[0016] Preferably, the current collector with a through-hole structure is any one of a metal foil current collector, a functional current collector or a bipolar current collector, preferably a functional current collector. It should be noted that the functional current collector refers to a polymer base film as a substrate, and metal layers are stacked on both sides of the polymer base film.

[0017] It should be noted that a plurality of through holes refers to “at least 2 through holes”, and the same applies to the following.

[0018] Preferably, the spacing between adjacent through holes is 0.1 mm-20 mm, for example, 0.1 mm, 0.5 mm, 1 mm, 5 mm, 10 mm, 15 mm or 20 mm, etc., preferably 0.5 mm-6 mm.

[0019] In the present invention, multiple through holes with appropriate spacing help to ensure the strength and stability of the current collector, and avoid too small a hole spacing which will cause the connecting parts between the holes to weaken, thereby affecting the strength and stability of the structure; it is beneficial to reduce the difficulty of production, avoid cracking or breakage during the punching process, and even cause the material between the holes to completely break, avoiding stress concentration; if the hole spacing is too small, the stress concentration areas of multiple through holes will affect each other, causing the material to be more susceptible to fatigue and fracture.

[0020] Preferably, the shape of the through hole includes any one of a circle, an ellipse, a polygon, an irregular shape, or a combination of at least two of them, preferably a polygon, for example, a pentagon or a hexagon.

[0021] In the present invention, the polygonal through hole can increase the contact area between the active material and the current collector because it has more edges and corners and uneven areas; compared with the circular through hole, the polygonal through hole can form a mechanical interlocking structure with the active material; the polygonal edges and uneven structure can disperse stress and reduce local stress concentration, thereby making the overall peeling strength higher; the complex interface shape of the polygon can provide more bonding points and paths.

[0022] Preferably, no metal layer is deposited on the hole wall of the through hole.

[0023] In the present invention, for the functional current collector, if no metal layer is deposited on the hole wall of the through hole, it is beneficial to reduce the occurrence of short circuit phenomenon and improve safety performance.

[0024] Preferably, the inner wall roughness Ra of the through hole is 1 μm-150 μm, for example, 1 μm, 10 μm, 50 μm, 100 μm or 150 μm, etc., preferably 60 μm-80 μm.

[0025] It should be noted that the roughness of the inner wall of the through hole can be measured by an optical microscope, that is, the inner wall of the through hole is observed and imaged by an optical microscope, and then the surface morphology in the image is analyzed using image analysis software to calculate the roughness parameters; an ordinary optical microscope or an electron microscope can be used, and selection can be made according to different magnification and resolution requirements.

[0026] In the present invention, the inner wall roughness of the through hole is within a suitable range, which is beneficial to increase the bonding force of the active material inside the through hole.

[0027] In the present invention, the adjustment of the inner wall roughness of the through hole is achieved by adjusting the shape of the punching needle and providing edges and corners on its surface.

[0028] Preferably, the through hole has a concavity and convexity of 1 nm-50 μm, for example, it may be 1 nm, 10 nm, 50 nm, 100 nm, 1 μm, 5 μm, 10 μm or 50 μm.

[0029] It should be noted that, for the through hole on the current collector, the convexity refers to the height of the through hole edge protruding or concave relative to the plane where the through hole is located, which can be measured using a high-precision profilometer.

[0030] In the present invention, the appropriate concavity and convexity helps to increase the peeling force between the current collector and the active material, improve the infiltration efficiency of the electrolyte, and avoid the wrinkle problem during the tape running process.

[0031] In the present invention, the adjustment of the concave-convex degree is achieved by adjusting the inclination angle of the cone surface provided at the inner wall opening of the groove and the difference between the diameter of the inner wall of the groove and the diameter of the punching needle.

[0032] Preferably, the thickness of the current collector is 2 μm-30 μm, for example, 2 μm, 5 μm, 10 μm, 15 μm, 20 μm, 25 μm or 30 μm.

[0033] In a second aspect, the present invention provides a method for preparing a current collector having a through-hole structure as described in the first aspect, the preparation method comprising the following steps:

[0034] The current collector to be punched is subjected to roller punching to obtain the current collector with a through-hole structure.

[0035] The present invention adopts a roller punching method to prepare a current collector with a through-hole structure, which has the following advantages: 1) low cost and simple process; 2) good punching quality, the formed hole shape is regular and the edge is relatively smooth, no large burrs will appear, and the appearance of burrs is reduced as much as possible, which is beneficial to subsequent processing and use; 3) fast and continuous processing can be achieved with high efficiency.

[0036] In a third aspect, the present invention provides a current collector pore-forming device used in the preparation method as described in the second aspect, wherein the current collector pore-forming device comprises a winding system and a punching system.

[0037] The winding system comprises a reel-off shaft and a reel-off shaft, which are respectively used for supporting the current collector to be perforated and outputting the current collector with a through-hole structure.

[0038] The punching system is arranged downstream of the unwinding shaft, and includes a needle roller and a support roller. The needle roller and the support roller are respectively arranged on both sides of the current collector. The surface of the needle roller is provided with a plurality of evenly distributed punching needles, and the surface of the support roller is provided with a plurality of grooves for piercing the punching needles to realize punching of the current collector.

[0039] The current collector hole-forming device provided by the present invention has the following advantages: 1) low cost and simple process; 2) good punching quality, the formed hole shape is regular and the edge is smooth, no large burrs will appear, and the appearance of burrs is reduced as much as possible, which is beneficial to subsequent processing and use; 3) fast and continuous processing can be achieved with high efficiency.

[0040] It should be noted that the function of the unwinding shaft is to support the current collector coil to be punched and to play the role of conveying the current collector.

[0041] Preferably, a front traction roller and a tension detection roller are provided between the unwinding shaft and the punching system, the front traction roller is used to support and pull the current collector, and the tension detection roller is used to detect the tension of the current collector during operation.

[0042] Preferably, a rear traction roller is provided between the punching system and the reel.

[0043] Preferably, a defect detector is also distributed between the punching system and the reel.

[0044] It should be noted that the defect detector is used to detect defects in through holes. The specific detection contents include: hole position offset: the position of the hole does not meet the design requirements and an offset occurs; aperture error: the diameter of the hole does not meet the predetermined size, it is too large or too small; burrs: large burrs appear on the edge of the hole after punching; breakage: cracks or breakage occur in the material during the punching process; irregular hole shape: different from or irregular with the preset shape; non-penetration: failure to completely penetrate the material, resulting in residual material at the bottom of the hole.

[0045] Preferably, the diameter of the punching needle is the same as the diameter of the through hole.

[0046] It should be noted that the thickness of the punching needle determines the diameter of the through hole, which can be controlled to an error within 0.1mm.

[0047] Preferably, the punching needle is made of metal, for example, stainless steel, copper or aluminum.

[0048] Preferably, the inner wall diameter of the groove is larger than the diameter of the punching needle, and the difference is ≤0.05 mm, for example, it can be 0.01 mm, 0.02 mm, 0.03 mm, 0.04 mm or 0.05 mm.

[0049] In the present invention, in order to avoid burrs as much as possible, the gap between the punching needle and the groove is ≤0.05 mm, so that a shear force can be ensured between the punching needle and the groove, and the shear force can punch the current collector into a specific shape and reduce the generation of burrs.

[0050] Preferably, the number of the grooves is the same as the number of the punching needles, and the center positions of the grooves correspond to the center positions of the punching needles.

[0051] In the present invention, "the center position of the groove corresponds to the center position of the punching needle" describes a precise geometric position relationship, which is of great significance for ensuring processing accuracy, realizing product functions and maintaining the continuity of the production process.

[0052] Preferably, a conical surface is provided at the inner wall opening of the groove.

[0053] In the present invention, the function of the conical surface is to punch holes along the conical surface, provide a buffer for the needle punching, ensure that the punching needle falls smoothly into the groove without mechanical collision, avoid direct impact on the bottom plate, damage the needle head, and extend the service life.

[0054] Preferably, the supporting roller is a hollow structure.

[0055] Preferably, the groove is a through hole structure.

[0056] Preferably, one end of the support roller is connected to a dust collecting box via a negative pressure air pipe, so as to collect the fluid collector fragments and fluid collector chips generated during the punching process.

[0057] In the present invention, the current collector fragments and current collector chips generated during the punching process are collected by negative pressure, thereby ensuring the safety of the battery and reducing the introduction of the current collector fragments and current collector chips into the battery.

[0058] It should be noted that a vacuum pump is provided on the negative pressure air pipe to provide negative pressure to the supporting roller of the hollow structure.

[0059] In a fourth aspect, the present invention provides a use of the current collector with a through-hole structure as described in the first aspect in a lithium-ion battery.

[0060] Preferably, the lithium-ion battery comprises a positive electrode sheet and a negative electrode sheet, the positive electrode sheet comprises a current collector having a through-hole structure as described in the first aspect and / or the negative electrode sheet comprises a current collector having a through-hole structure as described in the first aspect.

[0061] The numerical range described in the present invention not only includes the point values ​​listed above, but also includes any point values ​​between the above numerical ranges that are not listed. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0062] Compared with the prior art, the present invention has the following beneficial effects:

[0063] (1) The present invention provides a plurality of through holes that penetrate the entire current collector and limits the hole diameter and area ratio of the through holes, so that the mechanical properties of the current collector can meet the use requirements. The peeling force of the pole piece prepared based on this is significantly improved, and the electrolyte infiltration time of the prepared battery is shortened from 3 days to 1 day for full infiltration, and the cycle performance is further improved.

[0064] (2) The current collector hole-forming device provided by the present invention has the following advantages: 1) low cost and simple process; 2) good punching quality, the formed hole shape is regular and the edge is smooth, no large burrs will appear, and the appearance of burrs is reduced as much as possible, which is beneficial to subsequent processing and use; 3) fast and continuous processing can be achieved with high efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0065] Figure 1 This is a physical picture of the current collector with a through-hole structure provided in Example 1 of the present invention.

[0066] Figure 2 A two-dimensional plan view of the through holes of the current collector with a through hole structure provided in Example 1 of the present invention.

[0067] Figure 3 This is a schematic diagram of the structure of the current collector pore-forming device used in Example 1 of the present invention.

[0068] Figure 4 This is a schematic diagram of the grooves and punching needles in the current collector pore-forming device used in Example 1 of the present invention.

[0069] Figure 5 Schematic diagram of the device for collecting current collector fragments and current collector scraps provided in Example 1 of the present invention.

[0070] Among them, 1-unwinding shaft; 2-current collector; 3-front traction roller; 4-tension detection roller; 5-needle roller; 6-punching needle; 7-support roller; 8-groove; 9-rear traction roller; 10-defect detector; 11-rewinding shaft; 12-negative pressure air pipe; 13-vacuum pump; 14-dust collection box; 15-conical surface. DETAILED DESCRIPTION

[0071] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only used to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0072] Example 1

[0073] The present invention provides a current collector having a through-hole structure, such as Figure 1 As shown, the current collector is provided with a plurality of through holes penetrating the current collector along the thickness direction.

[0074] The diameter of the through hole is 0.5 mm, and the area of ​​the through hole in the current collector accounts for 10%; the spacing between adjacent through holes is 10 mm; the shape of the through hole is circular; the inner wall roughness Ra of the through hole is 70 μm; the through hole has a convexity and the convexity is 10 μm; the current collector is aluminum foil with a thickness of 13 μm.

[0075] Figure 2 A two-dimensional plan view of the through hole of the current collector with a through hole structure provided in this embodiment is shown. As can be seen from the figure, the through hole has no large burrs.

[0076] This embodiment also provides a method for preparing the current collector having a through-hole structure, the method comprising the following steps:

[0077] The current collector to be punched is subjected to roller punching to obtain the current collector with a through-hole structure.

[0078] This embodiment also provides a current collector pore-forming device used in the above preparation method, and its structural schematic diagram is shown in FIG. Figure 3 As shown, the current collector pore-forming device includes a winding system and a punching system.

[0079] The winding system comprises a reel 1 and a reel 11, which are respectively used to support the current collector 2 to be punched and output the current collector 2 with a through-hole structure.

[0080] The punching system is arranged downstream of the unwinding shaft 1, and includes a needle roller 5 and a hollow support roller 7. The needle roller 5 and the support roller 7 are respectively arranged on both sides of the current collector 2. The surface of the needle roller 5 is provided with a plurality of evenly distributed punching needles 6, and the surface of the support roller 7 is provided with a plurality of grooves 8 for piercing the punching needles 6 to realize punching of the current collector 2; the diameter of the punching needle 6 is the same as the diameter of the through hole, the material of the punching needle 6 is stainless steel, and the cross-sectional shape of the punching needle 6 is circular.

[0081] Figure 4 A schematic diagram of the groove 8 and the punching needle 6 provided in this embodiment is shown, wherein the inner wall diameter of the groove 8 is larger than the diameter of the punching needle 6, and the difference between the two is 0.02 mm; the number of the grooves 8 is the same as the number of the punching needles 6, and the center position of the groove corresponds to the center position of the punching needle; a conical surface 15 is provided at the inner wall opening of the groove 8, and the groove 8 is a through hole structure.

[0082] A front traction roller 3 and a tension detection roller 4 are provided between the unwinding shaft 1 and the punching system. The front traction roller 3 is used to support and pull the current collector 2, and the tension detection roller 4 is used to detect the tension of the current collector 2 during operation.

[0083] A rear traction roller 9 is arranged between the punching system and the winding shaft 11 , and a defect detector 10 is also distributed between the punching system and the winding shaft 11 .

[0084] like Figure 5 As shown, one end of the support roller 7 is connected to a dust collecting box 14 via a negative pressure air pipe 12 for collecting fluid collector fragments and fluid collector chips generated during the punching process; a vacuum pump 13 is provided on the negative pressure air pipe 12 for providing negative pressure to the support roller 7 with a hollow structure.

[0085] Example 2

[0086] The present invention provides a current collector with a through-hole structure, wherein the current collector is provided with a plurality of through-holes penetrating the current collector along a thickness direction.

[0087] The diameter of the through hole is 0.2 mm, and the area of ​​the through hole in the current collector accounts for 30%; the spacing between adjacent through holes is 1 mm; the shape of the through hole is circular; the inner wall roughness Ra of the through hole is 1 μm; the through hole has a convexity and the convexity is 1 nm; the current collector is copper foil with a thickness of 6 μm.

[0088] This embodiment also provides a method for preparing the current collector having a through-hole structure, the method comprising the following steps:

[0089] The current collector to be punched is subjected to roller punching to obtain the current collector with a through-hole structure.

[0090] This embodiment also provides a current collector pore-forming device used in the above-mentioned preparation method, and the current collector pore-forming device includes a winding system and a punching system.

[0091] The winding system comprises a reel-off shaft and a reel-off shaft, which are respectively used for supporting the current collector to be perforated and outputting the current collector with a through-hole structure.

[0092] Example 3

[0093] The present invention provides a current collector with a through-hole structure, wherein the current collector is provided with a plurality of through-holes penetrating the current collector along a thickness direction.

[0094] The diameter of the through hole is 3mm, and the area of ​​the through hole in the current collector accounts for 20%; the spacing between adjacent through holes is 20mm; the shape of the through hole is circular; the inner wall roughness Ra of the through hole is 150μm; the through hole has a convexity and concavity of 50μm; the current collector includes a polymer (polypropylene) base film, and a metal layer (made of copper) arranged on the surfaces of both sides of the polymer base film, and the single-sided thickness of the metal layer is 1000nm; no metal layer is deposited on the hole wall of the through hole; the thickness of the current collector is 6μm.

[0095] This embodiment also provides a method for preparing the current collector having a through-hole structure, the method comprising the following steps:

[0096] The current collector to be punched is subjected to roller punching to obtain the current collector with a through-hole structure.

[0097] Example 4

[0098] The difference between this embodiment and embodiment 1 is that the area of ​​the through holes in the current collector accounts for 15%.

[0099] The rest of the preparation methods and parameters were the same as those in Example 1.

[0100] Example 5

[0101] The difference between this embodiment and embodiment 1 is that the diameter of the through hole in the current collector is 1 mm.

[0102] The rest of the preparation methods and parameters were the same as those in Example 1.

[0103] Example 6

[0104] The difference between this embodiment and embodiment 1 is that the spacing between adjacent through holes is 0.5 mm.

[0105] The rest of the preparation methods and parameters were the same as those in Example 1.

[0106] Example 7

[0107] The difference between this embodiment and embodiment 1 is that the spacing between adjacent through holes is 6 mm.

[0108] The rest of the preparation methods and parameters were the same as those in Example 1.

[0109] Example 8

[0110] The difference between this embodiment and embodiment 1 is that the inner wall roughness Ra of the through hole is 60 μm.

[0111] The rest of the preparation methods and parameters were the same as those in Example 1.

[0112] Example 9

[0113] The difference between this embodiment and embodiment 1 is that the inner wall roughness Ra of the through hole is 80 μm.

[0114] The rest of the preparation methods and parameters were the same as those in Example 1.

[0115] Example 10

[0116] The difference between this embodiment and embodiment 1 is that the spacing between adjacent through holes is 0.05 mm.

[0117] The rest of the preparation methods and parameters were the same as those in Example 1.

[0118] Embodiment 11

[0119] The difference between this embodiment and embodiment 1 is that the spacing between adjacent through holes is 25 mm.

[0120] The rest of the preparation methods and parameters were the same as those in Example 1.

[0121] Example 12

[0122] The difference between this embodiment and the first embodiment is that the inner wall roughness Ra of the through hole is 0.5 μm.

[0123] The rest of the preparation methods and parameters were the same as those in Example 1.

[0124] Example 13

[0125] The difference between this embodiment and the first embodiment is that the inner wall roughness Ra of the through hole is 250 μm.

[0126] The rest of the preparation methods and parameters were the same as those in Example 1.

[0127] Embodiment 14

[0128] The difference between this embodiment and the first embodiment is that the cross-sectional shape of the punching needle is changed to a pentagon, so that the shape of the through hole is a pentagon.

[0129] The rest of the preparation methods and parameters were the same as those in Example 1.

[0130] Embodiment 15

[0131] The difference between this embodiment and embodiment 3 is that a metal layer is deposited on the hole wall of the through hole, that is, the base film is firstly punched by roller pressing, and then a metal layer is deposited on both sides.

[0132] The rest of the preparation methods and parameters were the same as those in Example 3.

[0133] Example 16

[0134] The difference between this embodiment and embodiment 1 is that the area of ​​the through holes in the current collector accounts for 30%.

[0135] The rest of the preparation methods and parameters were the same as those in Example 1.

[0136] Comparative Example 1

[0137] The difference between this comparative example and Example 1 is that the aluminum foil does not have through holes, that is, the aluminum foil is not rolled and punched.

[0138] The rest of the preparation methods and parameters were the same as those in Example 1.

[0139] Comparative Example 2

[0140] The difference between this comparative example and Example 2 is that the copper foil does not have through holes, that is, the aluminum foil is not rolled and punched.

[0141] The rest of the preparation methods and parameters were the same as those in Example 2.

[0142] Comparative Example 3

[0143] The difference between this comparative example and Example 1 is that the diameter of the through hole on the current collector is 0.1 mm by adjusting the thickness of the punching needle.

[0144] The rest of the preparation methods and parameters were the same as those in Example 1.

[0145] Comparative Example 4

[0146] The difference between this comparative example and Example 1 is that the diameter of the through hole on the current collector is 4 mm by adjusting the thickness of the punching needle.

[0147] The rest of the preparation methods and parameters were the same as those in Example 1.

[0148] Comparative Example 5

[0149] The difference between this comparative example and Example 1 is that the distribution density of the punching needles is adjusted so that the area of ​​the through holes in the current collector accounts for 5%.

[0150] The rest of the preparation methods and parameters were the same as those in Example 1.

[0151] Comparative Example 6

[0152] The difference between this comparative example and Example 1 is that the distribution density of the punching needles is adjusted so that the area of ​​the through holes in the current collector accounts for 35%.

[0153] The rest of the preparation methods and parameters were the same as those in Example 1.

[0154] Comparative Example 7

[0155] The difference between this comparative example and Example 1 is that the inner wall opening of the groove is not processed, that is, the inner wall opening of the groove is made into an edge surface.

[0156] The rest of the preparation methods and parameters were the same as those in Example 1.

[0157] Comparative Example 8

[0158] The difference between this comparative example and Example 3 is that the concavity and convexity of the current collector through hole is 60 μm.

[0159] The rest of the preparation methods and parameters were the same as those in Example 3.

[0160] Performance Testing

[0161] 1. The current collectors provided in the above embodiments and comparative examples are assembled into soft-pack batteries; wherein, the current collectors prepared in Embodiment 1, Embodiments 3-16, Comparative Examples 1, and Comparative Examples 3-8 are used as positive electrode current collectors, and commercial copper foil is used as the negative electrode current collector; the current collectors prepared in Embodiment 2 and Comparative Example 2 are used as positive electrode current collectors, and commercial aluminum foil is used as the negative electrode current collector.

[0162] The positive electrode material of the soft-pack battery includes positive electrode active material (NCM811), conductive carbon black, polyvinylidene fluoride (PVDF5130) and carbon nanotubes, and the mass ratio of the four is 96:1.8:1.7:0.5; the negative electrode material of the soft-pack battery includes negative electrode active material (graphite), aqueous binder (LA136D), conductive carbon black, carbon nanotubes and carboxymethyl cellulose, and the mass ratio of the five is 96:2.3:0.9:0.4:0.4; the electrolyte of the soft-pack battery is: 1 mol / L LiPF6 solution (the solvent is EC and EMC in a volume ratio of 3:7); the separator of the soft-pack battery is a polyethylene film; the designed nominal capacity of the soft-pack battery is 4Ah.

[0163] The mechanical and electrochemical properties of the soft-pack battery prepared above were tested.

[0164] Test method for tensile strength and elongation: The tensile strength and elongation of the current collectors provided in the above embodiments and comparative examples were tested with reference to the national standard GB / T 1040.3-2006.

[0165] The test method of electrode peeling force is as follows: the rolled electrode is cut into a size of 10×2cm and tested with an electronic peeling tester; the cut electrode sample is pasted to the tested stainless steel plate with a 2cm wide 3M tape, and one side of the electrode is opened for a 180° electrode peeling test. After the test is completed, the experimental parameters are recorded.

[0166] The test conditions for capacity retention rate are as follows: the soft-pack battery is charged and discharged 150 times at a charge and discharge rate of 1C, and the battery capacity retention rate of the lithium-ion battery after 150 cycles of charge and discharge is calculated. The battery capacity retention rate after 150 cycles of charge and discharge = battery capacity after 150 cycles of charge and discharge / initial capacity of the battery × 100%.

[0167] 2. The current collectors provided in the above embodiments and comparative examples are assembled into cylindrical batteries, and then infiltrated with electrolyte. The specific steps include:

[0168] The current collectors provided in the above embodiments and comparative examples are assembled into cylindrical batteries, which are then infiltrated with electrolyte (dye is added to the electrolyte during testing). After infiltration for a certain period of time, the battery cells are disassembled and the degree of electrolyte infiltration is observed with the naked eye. When the surface of the electrode material and the diaphragm are evenly dyed and there is no local non-wetting, the infiltration time is recorded.

[0169] The above test results are shown in Table 1.

[0170] Table 1

[0171]

[0172]

[0173] analyze:

[0174] As can be seen from the above table, the present invention provides a plurality of through holes that penetrate the entire current collector in the current collector and limits the hole diameter and area ratio of the through holes, so that the mechanical properties of the current collector meet the use requirements. The peeling force of the pole piece prepared based on this is significantly improved, and the electrolyte infiltration time of the prepared battery is shortened from 3 days to 1 day for sufficient infiltration, and the cycle performance is further improved.

[0175] It can be seen from Example 1, Example 4, Example 16 and Comparative Examples 5-6 that a reasonable proportion of through-hole area is conducive to improving the peeling force and capacity retention rate of the pole piece. In addition, as the hole proportion increases, its tensile strength decreases, the elongation also decreases, and the pole piece peeling force increases, and the battery cycle performance first increases and then decreases. However, if the area proportion of the through-holes in the current collector is too small, the peeling force of the pole piece decreases, and the battery cycle performance is poor. If the area proportion of the through-holes in the current collector is too large, the tensile strength and elongation of the current collector will be reduced, resulting in the current collector being prone to problems such as broken belts, wrinkles and deformations in subsequent production processes such as belt walking and rolling, and causing the battery cycle performance to be significantly reduced.

[0176] It can be seen from Example 1, Example 5 and Comparative Examples 3-4 that through holes with appropriate hole diameters help ensure that the mechanical properties of the current collector meet the use requirements, and can also improve the energy density. If the hole diameter of the through hole on the current collector is too small, the pole piece peeling force will decrease; if the hole diameter of the through hole on the current collector is too large, the tensile strength and elongation of the current collector will be seriously reduced, resulting in the current collector being prone to problems such as broken belts, wrinkles and deformation in subsequent production processes such as belt walking and rolling, and the battery cycle performance will be significantly reduced.

[0177] It can be seen from Examples 1, 6-7 and 10-11 that if the spacing between adjacent through holes is too small, the stress concentration areas of multiple holes will affect each other, causing the material to be more susceptible to fatigue and fracture, decreased tensile strength and elongation, decreased electrode peeling force, and decreased cycle performance; if the spacing between adjacent through holes is too large, it will affect the peeling force and cycle performance of the battery.

[0178] It can be seen from Examples 1, 8-9 and 12-13 that if the inner wall roughness of the through hole is too small, the electrode peeling force will decrease and the battery cycle performance will decrease; if the inner wall roughness of the through hole is too large, the mechanical properties of the current collector will decrease and the battery cycle performance will decay.

[0179] It can be seen from Example 1 and Example 14 that if the through hole is pentagonal in shape, the contact area between the active material and the current collector can be increased; compared with circular through holes, polygonal through holes can form a mechanical interlocking structure with the active material; polygonal edges and concave-convex structures can disperse stress and reduce local stress concentration, thereby making the overall peel strength higher and the mechanical properties meet the use requirements; the complex polygonal interface shape can provide more bonding points and paths. Based on this, the battery cycle performance is also further improved.

[0180] It can be seen from Example 3 and Example 15 that if a metal layer is deposited on the hole wall of the through hole, it is not conducive to improving the peeling force of the electrode sheet, resulting in a decrease in the cycle performance of the battery.

[0181] It can be seen from Example 1 (or Example 2) and Comparative Example 1 (or Comparative Example 2) that if the current collector is not roll-punched, the safety performance will be reduced and the electrode peeling force will be significantly reduced.

[0182] It can be seen from Example 1 and Comparative Example 7 that if the inner wall opening of the groove is an edge surface instead of a cone surface, the punching needle cannot fall smoothly into the groove, and mechanical collision is likely to occur, damaging the needle head and shortening the service life.

[0183] It can be seen from Example 3 and Comparative Example 8 that if the concavo-convexity of the current collector through hole is too large, although the mechanical properties are good, the cycle performance of the battery drops sharply.

[0184] The applicant declares that the present invention illustrates the process method of the present invention through the above-mentioned embodiments, but the present invention is not limited to the above-mentioned process steps, that is, it does not mean that the present invention must rely on the above-mentioned process steps to be implemented. Those skilled in the art should understand that any improvement of the present invention, equivalent replacement of the raw materials selected by the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A current collector having a through-hole structure, characterized in that: The current collector is provided with a plurality of through holes penetrating the current collector along the thickness direction; The diameter of the through hole is 0.2 mm-3 mm, and the area of ​​the through hole in the current collector accounts for 10%-30%.

2. The current collector according to claim 1, characterized in that: The spacing between adjacent through holes is 0.1 mm to 20 mm, preferably 0.5 mm to 6 mm; Preferably, the shape of the through hole includes any one of a circular shape, an elliptical shape, a polygonal shape, and an irregular shape, or a combination of at least two of them, preferably a polygonal shape.

3. The current collector according to claim 1 or 2, characterized in that: No metal layer is deposited on the hole wall of the through hole; Preferably, the inner wall roughness Ra of the through hole is 1 μm-150 μm, preferably 60 μm-80 μm; Preferably, the through hole has a concavity and convexity of 1 nm-50 μm; Preferably, the thickness of the current collector is 2 μm-30 μm.

4. A method for preparing a current collector having a through-hole structure according to any one of claims 1 to 3, characterized in that: The preparation method comprises the following steps: The current collector to be punched is subjected to roller punching to obtain the current collector with a through-hole structure.

5. A current collector pore-forming device used in the preparation method according to claim 4, characterized in that: The current collector pore-forming device comprises a winding system and a punching system; The winding system includes a reel and a reel, which are respectively used to support the current collector to be punched and output the current collector with a through-hole structure; The punching system is arranged downstream of the unwinding shaft, and includes a needle roller and a support roller. The needle roller and the support roller are respectively arranged on both sides of the current collector. The surface of the needle roller is provided with a plurality of evenly distributed punching needles, and the surface of the support roller is provided with a plurality of grooves for piercing the punching needles to realize punching of the current collector.

6. The current collector pore forming device according to claim 5, characterized in that: A front traction roller and a tension detection roller are arranged between the unwinding shaft and the punching system, the front traction roller is used to support and pull the current collector, and the tension detection roller is used to detect the tension of the current collector during operation; Preferably, a rear traction roller is provided between the punching system and the reel; Preferably, a defect detector is also distributed between the punching system and the reel.

7. The current collector pore-forming device according to claim 5 or 6, characterized in that: The diameter of the punching needle is the same as the diameter of the through hole; Preferably, the punching needle is made of metal; Preferably, the inner wall diameter of the groove is larger than the diameter of the punching needle, and the difference is ≤0.05 mm.

8. The current collector pore-forming device according to any one of claims 5 to 7, characterized in that: The number of the grooves is the same as the number of the punching needles, and the center position of the groove corresponds to the center position of the punching needle; Preferably, a conical surface is provided at the inner wall opening of the groove.

9. The current collector pore-forming device according to any one of claims 5 to 8, characterized in that: The support roller is a hollow structure; Preferably, the groove is a through-hole structure; Preferably, one end of the support roller is connected to a dust collecting box via a negative pressure air pipe, so as to collect the fluid collector fragments and fluid collector chips generated during the punching process.

10. Use of the current collector with a through-hole structure as claimed in any one of claims 1 to 3 in a lithium-ion battery.

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