A current collector, a preparation method thereof, and a battery

Abstract

The present invention provides a current collector, a preparation method thereof, and a battery. The current collector includes: a polymer layer; a metal layer located on both surface sides of the polymer layer; a through-hole structure that penetrates the polymer layer and the metal layer along the thickness direction of the current collector; and the holes of the through-hole structure are filled with a first lithium-philic polymer material. The current collector provided by the present invention achieves the purpose of weight reduction through the synergistic cooperation of the structure and materials, improves the energy density of the current collector, realizes the uniform deposition of lithium, and avoids the generation of lithium dendrites; at the same time, it also plays a role in reducing the occurrence probability of thermal runaway and improves the electrochemical performance of the battery.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium-ion batteries, and relates to a current collector, a preparation method thereof, and a battery. Background Art

[0002] Lithium-ion batteries (LIBs) have become the dominant technology for portable electronic devices, portable device power supplies, and energy storage due to advantages such as long service life and high energy efficiency. Over the past decade, the rapid development in various fields has imposed higher requirements on LIBs, especially higher energy density and better safety. In the traditional LIB structure, pure metal current collectors such as copper foil (ρ = 8.96 g / cm 3 ) or aluminum foil are usually used to support the active materials of the negative electrode and the positive electrode, respectively. However, their total mass accounts for more than 15% of the total weight of the LIB, but they do not contribute to the capacity at all, which greatly hinders the improvement of the overall energy density of the LIB. Due to the uneven surface of the bare copper, the formed SEI film is unstable, and the lithium-ion flux usually concentrates at the tip of the bare copper, resulting in an excessive local current density, uneven nucleation and growth of lithium metal, and promoting dendrite growth. Therefore, it is very necessary to induce uniform deposition of lithium from the lithium metal nucleation stage. To solve the problems of the overweight current collector and lithium dendrites, scientific researchers have carried out a large number of studies on this.

[0003] (1) Constructing a three-dimensional conductive framework as the host material for metallic lithium can significantly improve the volume expansion problem during the cycling of metallic lithium. At the same time, the conductive framework can reduce the generation of "dead lithium" and thus improve the utilization rate of metallic lithium. For example, Si-yuan Li et al. [Advanced Functional Materials 2019:1808847.] modified a layer of Co3O4 nanowires on carbon fiber as the current collector for the lithium metal negative electrode. The large spatial volume of the three-dimensional framework structure of the carbon fiber can buffer the volume expansion problem during cycling, and the conversion reaction between Co3O4 and lithium endows the composite current collector with excellent lithiophilicity. However, the three-dimensional conductive framework in the above literature sacrifices the material structure strength, resulting in poor structural strength of the current collector.

[0004] (2) Using a thinner metal current collector. For example, CN114164464A discloses a cathode roller and a cathode roller PVA process for producing a 4-8um ultra-thin lithium battery copper foil, including an O-ring and an end plate. The O-ring and the end plate are arranged at the end of the cathode roller. The O-ring is made of rubber material, and the end plate is made of PVC board. Through the special structure of the cathode roller and the PVA method, the surface roughness of the cathode roller is 0.15-0.18um, making the copper foil crystals finer and the physical properties more excellent. At the same time, the phenomenon of edge tearing and wrinkling of the ultra-thin lithium battery copper foil during production is reduced, and the production efficiency of the copper foil is improved. At the same time, the thinning of the copper foil also needs to fully consider the influence of mechanical properties, especially mechanical toughness, because the copper foil as the current collector of the negative electrode needs good mechanical toughness to relieve the stress generated by the volume change during the charge and discharge process of the active material. However, the production yield and the mechanical strength problem of the thin foil brought about by the thinning of the foil are also limiting factors for the ultra-thin metal current collector.

[0005] (3) Promoting the uniform deposition of lithium ions by constructing a lithium-philic coating or a nanoarray. For example, CN115911400A discloses a negative electrode current collector, an electric core, a battery pack, a vehicle, and a processing method of the negative electrode current collector, belonging to the technical field of battery manufacturing. The negative electrode current collector includes: a copper foil having a three-dimensional cross-linked porous structure; a lithium-philic layer covering at least a partial area of at least one surface of the copper foil; and a graphite layer covering the lithium-philic layer and covering the surface of the copper foil. However, during the cycling process, the lithium-philic coating or the lithium-philic nanoarray is prone to fall off, resulting in a decline in the cycling performance.

[0006] Therefore, how to effectively reduce the weight of the current collector, avoid the phenomenon of uneven lithium deposition, and improve the electrochemical performance of the battery is a technical problem that urgently needs to be solved at present. Summary of the Invention

[0007] Aiming at the deficiencies of the existing technology, the purpose of the present invention is to provide a current collector, a preparation method thereof, and a battery. The current collector provided by the present invention achieves the purpose of weight reduction through the synergistic cooperation of structure and materials, improves the energy density of the current collector, realizes the uniform deposition of lithium, and avoids the generation of lithium dendrites; at the same time, it also plays a role in reducing the probability of thermal runaway and improving the electrochemical performance of the battery.

[0008] To achieve the purpose of the present invention, the following technical solutions are adopted:

[0009] In the first aspect, the present invention provides a current collector, which includes:

[0010] A polymer layer;

[0011] A metal layer located on both side surfaces of the polymer layer;

[0012] A through-hole structure that penetrates the polymer layer and the metal layer along the thickness direction of the current collector;

[0013] The hole of the through-hole structure is filled with a first lithiumophilic polymer material.

[0014] Through the cooperation of the metal layer and the polymer layer structure, the current collector of the present invention has excellent mechanical flexibility and is not easily broken. Even if it breaks, it cannot reach the standard of piercing the separator, avoiding the occurrence of battery short circuit and reducing the probability of thermal runaway. At the same time, the specific structure combination of the polymer and the metal layer has a density far lower than that of the pure metal layer, significantly improving the energy density of the battery. The through-hole structure and the first lithiumophilic polymer material cooperate synergistically, which not only promotes the uniform deposition of lithium ions, but also further reduces the weight of the current collector, and at the same time compensates for the conductivity caused by the opening. Through the synergistic effect of the specific structure and materials, the good conductivity of the current collector is ensured, the energy density and thermal stability of the battery are improved, the uniform deposition of lithium ions is promoted, and thus the first efficiency and cycle performance of the battery are improved.

[0015] The following are the preferred technical solutions of the present invention, but do not limit the technical solutions provided by the present invention. Through the following preferred technical solutions, the technical objectives and beneficial effects of the present invention can be better achieved and realized.

[0016] Preferably, the polymer material in the polymer layer includes any one or a combination of at least two of polyimide, polyvinylidene fluoride, polypropylene, polyethylene, polyethylene terephthalate, polymethyl methacrylate, polyethylene oxide or polyvinyl alcohol.

[0017] Preferably, the weight average molecular weight of the polymer in the polymer layer is 5000 - 50000, but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0018] Preferably, the thickness T1 of the polymer layer and the thickness T2 of the metal layer satisfy: 2μm ≤ T1 + T2 ≤ 6μm.

[0019] Preferably, the thickness T1 of the polymer layer and the thickness T2 of the metal layer satisfy: 1 / 6 ≤ T1 / (T1 + T2) ≤ 1 / 2.

[0020] Preferably, the thickness T1 of the polymer layer is 1 - 3μm.

[0021] Preferably, the thickness T2 of the metal layer satisfies: T2 is 1 - 3μm.

[0022] Preferably, the aperture size of the through-hole structure is 5 - 20μm.

[0023] Preferably, taking the thickness direction perpendicular to the current collector as the horizontal direction, the center distance of the holes of adjacent through holes in the same horizontal direction is 500-5000 μm.

[0024] Preferably, the first lithium-philic polymer material includes any one or a combination of at least two of polydopamine, polyethylene oxide, polyvinyl alcohol, or polyacrylamide.

[0025] Preferably, a second lithium-philic polymer material is grafted on the surface of the holes of the first lithium-philic polymer material; the second lithium-philic polymer material includes any one or a combination of at least two of polydopamine, polyethylene oxide, polyvinyl alcohol, or polyacrylamide.

[0026] In a second aspect, the present invention provides a method for preparing a current collector as described in the first aspect, and the preparation method includes the following steps:

[0027] Composite metal layers on both side surfaces of the polymer layer to obtain a composite structure;

[0028] Perform pore-forming treatment along the thickness direction of the composite structure to obtain a through-hole structure penetrating the polymer layer and the metal layer;

[0029] Fill the holes of the through-hole structure with the first lithium-philic polymer material to obtain the current collector.

[0030] Preferably, the method for the composite metal layer includes vacuum evaporation plating.

[0031] Preferably, the first lithium-philic polymer material is filled into the holes of the through-hole structure by an in-situ polymerization method.

[0032] Preferably, a second lithium-philic polymer material is grafted on the surface of the holes of the first lithium-philic polymer material, and the grafting method includes in-situ grafting.

[0033] Preferably, the in-situ grafting method includes:

[0034] Using the first lithium-philic polymer material as a photoinitiator, graft the monomer of the second lithium-philic polymer material and the first lithium-philic polymer material through light irradiation to make the second lithium-philic polymer material grafted on the surface of the holes of the first lithium-philic polymer material.

[0035] In a third aspect, the present invention further provides a battery, and the battery includes the current collector as described in the first aspect or the current collector prepared by the preparation method as described in the second aspect.

[0036] Compared with the prior art, the present invention has the following beneficial effects:

[0037] In the current collector provided by the present invention, the structure with a polymer composite between two metal layers endows the current collector with excellent mechanical flexibility and makes it not easily break. Even if it breaks, it cannot reach the standard of piercing the separator, thus avoiding the occurrence of battery short circuit and reducing the probability of thermal runaway. At the same time, the specific structural cooperation between the polymer and the metal layer can effectively reduce the thickness of the metal layer, making the density of the specific composite layer structure much lower than that of the pure metal layer, and significantly improving the energy density of the battery. The first lithiophilic polymer material interacts with the polymer in the current collector through hydrogen bonds and van der Waals forces, thus firmly fixing in the through-hole structure of the current collector. On the one hand, it promotes the uniform deposition of lithium ions, and on the other hand, it fills the through-hole structure and compensates for the conductivity caused by the opening. The through-hole structure ensures the conductivity connection between the front and back sides of the current collector and further reduces the weight of the current collector. That is, through the synergistic effect of specific structures and materials, the present invention ensures the good performance of the conductivity of the current collector, improves the energy density and thermal stability of the battery, promotes the uniform deposition of lithium ions, and thus improves the initial efficiency and cycle performance of the battery. Description of the Drawings

[0038] Figure 1 SEM image of the Cu-PI-Cu current collector with a through-hole structure provided in Example 1.

[0039] Figure 2 SEM image of the current collector provided in Example 1. Detailed Embodiments

[0040] The technical solutions of the present invention will be further described below through specific embodiments. Those skilled in the art should understand that the embodiments are only for helping to understand the present invention and should not be regarded as specific limitations on the present invention.

[0041] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in the description of the specification and claims of this application and the above description of the drawings are intended to cover non-exclusive inclusion.

[0042] In the description of the embodiments of this application, technical terms such as "first" and "second" are only used to distinguish different objects and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity, specific order or primary-secondary relationship of the indicated technical features. In the description of the embodiments of this application, "a plurality" means more than two unless otherwise specifically defined.

[0043] In a first specific embodiment, the present invention provides a current collector, which includes:

[0044] A polymer layer;

[0045] A metal layer located on both side surfaces of the polymer layer;

[0046] A through-hole structure that penetrates the polymer layer and the metal layer along the thickness direction of the current collector;

[0047] The holes of the through-hole structure are filled with a first lithiumophilic polymer material.

[0048] In the current collector provided by the present invention, the structure of the composite polymer between the two metal layers enables the current collector to have excellent mechanical flexibility and is not easily broken. Even if it breaks, it cannot reach the standard of piercing the separator, avoiding the occurrence of battery short circuit and reducing the probability of thermal runaway. At the same time, the structural cooperation of the specific polymer and the metal layer can effectively reduce the thickness of the metal layer, making the density of the specific composite layer structure much lower than that of the pure metal layer, significantly improving the energy density of the battery. The first lithiumophilic polymer material interacts with the polymer in the current collector through hydrogen bonds and van der Waals forces, thus firmly fixing in the through-hole structure of the current collector. On the one hand, it plays a role in promoting the uniform deposition of lithium ions, and on the other hand, it fills the holes in the through-hole structure, also making up for the conductivity caused by the opening. The through-hole structure ensures the conductivity connection between the front and back sides of the current collector and further reduces the weight of the current collector. That is, through the synergistic effect of the specific structure and materials, the present invention ensures the good performance of the conductivity of the current collector, improves the energy density and thermal stability of the battery, promotes the uniform deposition of lithium ions, and thus improves the initial efficiency and cycle performance of the battery.

[0049] In the current collector provided by the present invention, if the first lithiumophilic polymer is not located in the through-hole structure but on the surface of the metal layer, good electronic conductivity cannot be achieved.

[0050] As a preferred technical solution in the first specific embodiment, the polymer material in the polymer layer includes any one or a combination of at least two of polyimide, polyvinylidene fluoride, polypropylene, polyethylene, polyethylene terephthalate, polymethyl methacrylate, polyethylene oxide, or polyvinyl alcohol.

[0051] Furthermore, the weight-average molecular weight of the polymer in the polymer layer is 5,000 to 50,000, such as 5,000, 7,500, 10,000, 12,500, 15,000, 17,500, 20,000, 22,500, 25,000, 27,500, 30,000, 32,500, 35,000, 37,500, 40,000, 42,500, 45,000, 47,500 or 50,000, etc., but not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0052] It should be noted that for the polymer material in the polymer layer provided by the present invention, in addition to the above-mentioned characteristic limitations, other conventional types of substances of polymer materials that can be used in the battery current collector structure are equally applicable to the present invention; and further, the weight-average molecular weight of the polymer provided by the present invention is 5,000 to 50,000, which ensures the flexibility of the polymer.

[0053] As a preferred technical solution in the first specific embodiment, the thickness T1 of the polymer layer and the thickness T2 of the metal layer satisfy: 2 μm ≤ T1 + T2 ≤ 6 μm, such as 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, 5.5 μm or 6 μm, etc., but not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0054] As a preferred technical solution in the first specific embodiment, the thickness T1 of the polymer layer and the thickness T2 of the metal layer satisfy: 1 / 6 ≤ T1 / (T1 + T2) ≤ 1 / 2, such as 1 / 6, 2 / 6 or 3 / 6, etc., but not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0055] As a preferred technical solution in the first specific embodiment, the thickness T1 of the polymer layer is 1 to 3 μm, such as 1 μm, 1.5 μm, 2 μm, 2.5 μm or 3 μm, etc., but not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0056] As a preferred technical solution in the first specific embodiment, the thickness T2 of the metal layer is 1 to 3 μm, such as 1 μm, 1.5 μm, 2 μm, 2.5 μm or 3 μm, etc., but not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0057] In the present invention, by regulating the thickness T1 of the polymer layer and / or the thickness T2 of the metal layer and / or the numerical range of the parameters satisfying the relationship between T1 and T2, it is more beneficial to improve the flexibility of the current collector, ensure the conductivity and improve the system energy density.

[0058] As a preferred technical solution in the first specific embodiment, the pore size of the through-hole structure is 5-20 μm, such as 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm or 20 μm, etc., but not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0059] As a preferred technical solution in the first specific embodiment, taking the thickness direction perpendicular to the current collector as the horizontal direction, the center distance between the holes of adjacent through-holes in the same horizontal direction is 500-5000 μm, such as 500 μm, 750 μm, 1000 μm, 1250 μm, 1500 μm, 1750 μm, 2000 μm, 2250 μm, 2500 μm, 2750 μm, 3000 μm, 3250 μm, 3500 μm, 3750 μm, 4000 μm, 4250 μm, 4500 μm, 4750 μm or 5000 μm, etc., but not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0060] In the present invention, the pore size of the through-hole structure being 5-20 μm and / or the center distance between the holes being 500-5000 μm can enable the current collector to have excellent welding effect, while also ensuring the uniform deposition of lithium ions, and the mechanical strength of the current collector is also relatively high.

[0061] As a preferred technical solution in the first specific embodiment, the first lithium-philic polymer material includes any one or a combination of at least two of polydopamine, polyethylene oxide, polyvinyl alcohol or polyacrylamide.

[0062] In the present invention, the first lithium-philic polymer material has good affinity with lithium ions, can induce uniform lithium metal nucleation and inhibit the growth of lithium dendrites; and the first lithium-philic polymer material has photosensitive properties and can generate surface-bound free radicals to trigger surface-initiated radical polymerization of monomers on almost any substrate.

[0063] A further preferred solution is that the second lithium-philic polymer material is grafted on the surface of the holes of the first lithium-philic polymer material.

[0064] In the present invention, in addition to good lithium ion affinity, the first lithiumophilic polymer material can also be used as a photoinitiator to achieve graft connection of the second lithiumophilic polymer material with dual functions of nano-brush and functional groups. The second lithiumophilic polymer material has a large number of lithiumophilic functional groups, which play a role in inducing the uniform distribution of lithium ion nucleation positions on the surface of the current collector foil, increasing the possibility of nucleation and homogenizing the ion distribution. Moreover, the second lithiumophilic polymer material also has a nano-brush structure, which can greatly improve the interfacial wettability and affinity between the electrolyte and the current collector, and further improve the migration and diffusion of lithium ions.

[0065] Specifically: The second lithiumophilic polymer material includes any one or a combination of at least two of polydopamine, polyethylene oxide, polyvinyl alcohol, or polyacrylamide, preferably polyacrylamide.

[0066] In addition, it should be noted that in the present invention, the types of the first lithiumophilic polymer material and the second lithiumophilic polymer material can be the same or different; preferably, the first lithiumophilic polymer material is polydopamine and the second lithiumophilic polymer material is polyacrylamide.

[0067] It can be understood that in order to improve the electronic conductivity of the current collector, a conductive material can also be carried in the first lithiumophilic polymer material. The present invention does not limit the specific type of the conductive material, and any conventional conductive material that can be used to improve conductivity is applicable to the present invention. For example, the conductive material can be conductive carbon black, carbon nanotubes, graphite, graphene, or carbon fiber, etc.

[0068] In the second specific embodiment, the present invention provides a method for preparing a current collector as described in the above first specific embodiment. The preparation method includes the following steps:

[0069] Composite metal layers on both side surfaces of the polymer layer to obtain a composite structure;

[0070] Perform pore-forming treatment along the thickness direction of the composite structure to obtain a through-hole structure penetrating the polymer layer and the metal layer;

[0071] Fill the holes of the through-hole structure with the first lithiumophilic polymer material to obtain the current collector.

[0072] The preparation method provided by the present invention first composites the metal layers on both side surfaces of the polymer layer and then performs pore-forming treatment, avoiding the non-penetration of the obtained hole structure, thereby obtaining a through-hole structure, which is conducive to the subsequent filling of the first lithiumophilic polymer material; thus obtaining a current collector structure with stable structure, good mechanical properties, and excellent electrochemical properties; at the same time, the preparation method is simple to operate, without complex treatment processes, and is applicable to actual production and life.

[0073] As a preferred technical solution in the second specific embodiment, the method for the composite metal layer includes a vacuum evaporation method.

[0074] The present invention does not make special limitations on the method for compounding the metal layer, and any method that can achieve the compounding of the polymer layer and the metal layer is applicable to the present invention; and further adopting the vacuum evaporation method can precisely control the target thickness of the metal layer and has uniform deposition.

[0075] Specifically, the present invention provides a specific preparation process of the vacuum evaporation method:

[0076] Put the polymer layer into the vacuum chamber of the vacuum evaporation equipment, add the metal target, and perform vacuum evaporation of the metal layers on both surfaces of the polymer.

[0077] Optionally, during the vacuum evaporation process, the vacuum degree can be 10 kPa to 100 kPa (such as 10 kPa, 20 kPa, 30 kPa, 40 kPa, 50 kPa, 60 kPa, 70 kPa, 80 kPa, 90 kPa or 100 kPa, etc.); the temperature of the vacuum evaporation can be 300 °C to 3000 °C (such as 300 °C, 500 °C, 1000 °C, 1500 °C, 2000 °C, 2500 °C or 3000 °C, etc.); the voltage value of the vacuum evaporation can be 100 V to 20000 V (such as 100 V, 500 V, 1000 V, 2500 V, 5000 V, 7500 V, 10000 V, 12500 V, 15000 V, 17500 V or 20000 V, etc.).

[0078] As a preferred technical solution in the second specific embodiment, the first lithiumophilic polymer material is filled into the holes of the through-hole structure by an in-situ polymerization method.

[0079] It should be further noted that the present invention does not limit the metal elements in the metal layer, and any conventional metal elements that can be used for the battery current collector are applicable to the present invention; and the metal layer can be a pure metal layer or an alloy metal layer, etc.; for example, the metal elements include but are not limited to at least one of copper, aluminum, nickel, iron (the element of stainless steel), gold or silver; those skilled in the art can make adaptive selection and adjustment according to the type of metal element through the above specific vacuum evaporation process.

[0080] In a further preferred technical solution, the second lithiumophilic polymer material is grafted on the surface of the holes of the first lithiumophilic polymer material, and the grafting method includes in-situ grafting.

[0081] Specifically, the in-situ grafting method includes:

[0082] Using the first lithiumophilic polymer material as a photoinitiator, the monomers of the second lithiumophilic polymer material are grafted onto the first lithiumophilic polymer material through light irradiation, so that the second lithiumophilic polymer material is grafted onto the surface of the holes of the first lithiumophilic polymer material.

[0083] In the grafting method provided by the present invention, the first lithiumophilic polymer material can be directly used as an initiator material without the need to additionally add an initiator; and in-situ polymerization grafting reaction of the second lithiumophilic polymer is realized.

[0084] Optionally, the light source for the light irradiation includes a 300W xenon lamp for simulating sunlight.

[0085] Optionally, the temperature of the light irradiation is 100°C to 1000°C, such as 100°C, 200°C, 300°C, 400°C, 500°C, 600°C, 700°C, 800°C, 900°C or 1000°C, etc., and the time of the light irradiation is 10 min to 150 min, such as 10 min, 20 min, 30 min, 40 min, 50 min, 60 min, 70 min, 80 min, 90 min, 100 min, 110 min, 120 min, 130 min, 140 min or 150 min, etc.

[0086] It should be noted that the filling method of the first lithiumophilic polymer material in the holes in the present invention can be in-situ polymerization filling or non-in-situ polymerization filling. In-situ polymerization filling is preferred, which can realize the tight combination of the first lithiumophilic polymer material and the hole structure, so that the first lithiumophilic polymer material is firmly fixed in the through-hole structure of the current collector.

[0087] Specifically, the present invention provides a method for filling the holes of the through-hole structure with the first lithiumophilic polymer material, and the method includes the following steps:

[0088] Mix a composite structure with a through-hole structure and a monomer solution of the first lithiumophilic polymer material, carry out a polymerization reaction, and then remove the excess first lithiumophilic polymer material on the surface of the composite structure to realize the filling of the holes in the through-hole structure with the first lithiumophilic polymer material.

[0089] Optionally, during the mixing process, a buffer solution can also be added. The buffer solution includes a tris(hydroxymethyl)aminomethane hydrochloride (Tris-HCl) solution; the pH value of the buffer solution is 8.0 to 8.3, such as 8, 8.1, 8.2 or 8.3, etc.

[0090] Optionally, during the mixing process, a conductive material solution can also be added. The conductive material includes conductive carbon black (SP).

[0091] In the present invention, during the filling process of the first lithiophilic polymer material into the via hole structure, a conductive material is additionally added, further improving the electronic conductivity of the current collector.

[0092] Optionally, the mass ratio of the composite structure with the via hole structure to the monomer of the first lithiophilic polymer material is (50~300):1, such as 50:1, 100:1, 150:1, 200:1, 250:1 or 300:1, etc.

[0093] In the present invention, by regulating the mass ratio of the composite structure with the via hole structure to the monomer of the first lithiophilic polymer material, the uniform deposition of lithium ions can be better achieved.

[0094] Optionally, the polymerization reaction is carried out under light, and the light source of the light includes an ultraviolet light source, etc.; the power of the light is 100W~5000W, such as 100W, 500W, 1500W, 2000W, 2500W, 3000W, 3500W, 4000W, 4500W or 5000W, etc.

[0095] Optionally, the method for removing the excess first lithiophilic polymer material on the surface of the composite structure includes scraping, that is, a scraper can be used to scrape off the excess first lithiophilic polymer material.

[0096] In an application embodiment, the present invention further provides a battery, and the battery includes a current collector as described in the above first specific embodiment or a current collector prepared by the preparation method described in the above second specific embodiment.

[0097] The current collector provided by the present invention can be used in electrode plates, for example, it can be compounded with coatings such as an electrode active material layer to obtain an electrode plate (a positive electrode plate or a negative electrode plate); it can also be directly used as an electrode plate, that is, an electrode plate without an electrode active material layer, such as directly used as a negative electrode plate at the negative extreme.

[0098] The battery provided by the present invention includes a lithium ion battery, for example, it can be a primary lithium ion battery, a secondary lithium ion battery or a lithium ion battery without a negative electrode, etc. (a lithium ion battery without a negative electrode and only the current collector in the present application, without a negative electrode active material, etc.); and in the above-provided lithium ion battery, except for the current collector defined by the present invention, the remaining preparation raw materials, preparation methods and specific structures, etc. are all conventional technical solutions, and those skilled in the art can make adaptive selections and adjustments according to actual needs.

[0099] Example 1

[0100] This example provides a current collector, and the current collector includes:

[0101] A polymer layer, a polyimide (PI) film layer;

[0102] A metal layer, a copper layer, the metal layer being located on both side surfaces of the polymer layer;

[0103] A via hole structure, the via hole structure penetrating through the polymer layer and the metal layer along the thickness direction of the current collector; the holes of the via hole structure are filled with a first lithium-philic polymer material, polydopamine (PDA), and a second lithium-philic polymer material, polyacrylamide (PAM), is grafted onto the surface of the holes of the first lithium-philic polymer material.

[0104] The thickness T1 of the polymer layer is 1 μm, and the thickness T2 of the metal layer is 1 μm;

[0105] In the via hole structure, the aperture of the holes is 10 μm. Taking the direction perpendicular to the thickness direction of the current collector as the horizontal direction, the center distance between the holes of adjacent vias in the same horizontal direction is 2000 μm.

[0106] The preparation method of the current collector is as follows:

[0107] (1) Dissolve 10 mmol of 4,4-diaminodiphenyl ether (ODA) and 10 mmol of pyromellitic dianhydride (PMDA) successively in 40 mL of N,N-dimethylacetamide (DMAc) solvent. Under the protection of nitrogen (N2), stir at room temperature for 3 - 4 hours to obtain a polyamic acid (PAA) solution;

[0108] Then, quickly pour a catalyst mixture prepared by mixing pyridine and propionic anhydride (pyridine is 3 wt% of PAA, and the molar ratio of propionic anhydride to PAA is 3:1) into the PAA solution, stir at room temperature for 5 minutes and then perform spin coating; subsequently, place it in an oven, keep it at 90 °C for 30 min until the solvent evaporates to obtain a PAA film, and then heat-treat it at 200 °C for 10 min, cool it to room temperature to obtain a 1-μm-thick polyimide film (PI film). Cut the PI into corresponding sizes, ultrasonically clean it in absolute ethanol, 1 mol / L HCl solution, and deionized water for 5 min to remove surface oil stains and oxide films. Put the treated PI film into the cavity of a vacuum evaporation coater (EB-400S, Ecopia), and add a sufficient amount of target material (pure copper particles). Deposit 0.5-μm-thick metal copper layers on both sides of the PI film successively to obtain a Cu-PI-Cu composite current collector; use an ultraviolet picosecond laser drilling machine (LASER06007) to prepare via hole structures with an aperture of 10 μm and a spacing of 2×2 mm along the thickness direction on the Cu-PI-Cu composite current collector. The laser wavelength used is 355 nm, and the spot focus diameter is 10 μm;

[0109] (2) Prepare a buffer solution with a pH of 8.5 using 0.001 mol / L tris(hydroxymethyl)aminomethane hydrochloride (Tris-HCl). Repeatedly wash the Cu-PI-Cu with a through-hole structure using deionized water to remove impurities on its surface. Fix the clean Cu-PI-Cu with a through-hole structure at the bottom of an open container, pour an appropriate amount of the buffer solution into the container, and then add a mixed solution of 3 g / L SP and 2 g / L dopamine (the mass ratio of Cu-PI-Cu with a through-hole structure to dopamine is 100:1) into the solution. Irradiate the dopamine solution with a 36-watt ultraviolet lamp. Due to the self-polymerization reaction of dopamine under ultraviolet assistance, the color of the solution turns dark brown; then scrape off the excess polydopamine on the surface with a spatula to ensure that the polydopamine is evenly in the holes, rinse the surface with ultrapure water, and dry it with N2, so that the first lithiumophilic polymer material, polydopamine, fills the holes of the through-hole structure;

[0110] Immerse the PDA-modified copper foil into a quartz bottle containing an aqueous solution of acrylamide monomer with a mass fraction of 35% of acrylamide monomer. Degas it for 30 minutes with continuously dried nitrogen at room temperature, and seal the quartz bottle; irradiate it with a light source below 10 cm (simulating sunlight, a 300 W xenon lamp) for 1 h, and keep the temperature at about 25 °C to graft a second lithiumophilic polymer material onto the surface of the holes of the first lithiumophilic polymer material to obtain the current collector.

[0111] Figure 1 The SEM image of the Cu-PI-Cu current collector with a through-hole structure provided for Example 1 is shown. From Figure 1 it can be seen that after the pore-forming treatment, the obtained through-hole structure is uniform, fine, and well-distributed.

[0112] Figure 2 The SEM image of the current collector provided in Example 1 is shown.

[0113] Example 2

[0114] This example provides a current collector, and the current collector includes:

[0115] A polymer layer, a polyimide (PI) film layer;

[0116] A metal layer, a copper layer, and the metal layer is located on both side surfaces of the polymer layer;

[0117] A through-hole structure that penetrates the polymer layer and the metal layer along the thickness direction of the current collector; the holes of the through-hole structure are filled with a first lithiumophilic polymer material, polydopamine (PDA), and a second lithiumophilic polymer material, polyacrylamide (PAM), is grafted onto the surface of the holes of the first lithiumophilic polymer material.

[0118] The thickness T1 of the polymer layer is 2 μm, and the thickness T2 of the metal layer is 1 μm;

[0119] In the through-hole structure, the aperture of the hole is 20 μm. Taking the thickness direction perpendicular to the current collector as the horizontal direction, the center distance between the holes of adjacent through-holes in the same horizontal direction is 2000 μm.

[0120] The preparation method of the current collector is as follows:

[0121] (1) Dissolve 10 mmol of 4,4-diaminodiphenyl ether (ODA) and 10 mmol of pyromellitic dianhydride (PMDA) successively in 40 mL of N,N-dimethylacetamide (DMAc) solvent. Under the protection of nitrogen (N2), stir at room temperature for 3 - 4 hours to obtain a polyamic acid (PAA) solution;

[0122] Then, quickly pour a catalyst mixture solution prepared by mixing pyridine and propionic anhydride (pyridine is 3 wt% of PAA, and the molar ratio of propionic anhydride to PAA is 3:1) into the PAA solution, stir at room temperature for 5 minutes and then spin-coat; subsequently, place it in an oven, keep it at 90 °C for 30 min until the solvent evaporates to obtain a PAA film, and then heat-treat it at 200 °C for 10 min, cool it to room temperature to obtain a 2-μm-thick polyimide film (PI film). Cut the PI into appropriate sizes, ultrasonically clean it in anhydrous ethanol, 1 mol / L HCl solution, and deionized water for 5 min to remove surface oil stains and oxide films. Put the treated PI film into the cavity of a vacuum evaporation coater (EB-400S, Ecopia), and add a sufficient amount of target material (pure copper particles). Deposit a 1-μm-thick metallic copper layer on both sides of the PI film successively to obtain a Cu-PI-Cu composite current collector; use an ultraviolet picosecond laser drilling machine (LASER06007) to prepare a through-hole structure with a hole diameter of 20 μm and a pitch of 2 × 2 mm along the thickness direction for the Cu-PI-Cu composite current collector. The laser wavelength used is 355 nm, and the spot focus diameter is 10 μm;

[0123] (2) Prepare a buffer solution with a pH of 8.5 using 0.002 mol / L tris(hydroxymethyl)aminomethane hydrochloride (Tris-HCl). Wash the Cu-PI-Cu with a through-hole structure repeatedly with deionized water to remove impurities on its surface. Fix the clean Cu-PI-Cu with a through-hole structure at the bottom of an open container, pour an appropriate amount of the buffer solution into the container, and then add a mixed solution of 6 g / L SP and 4 g / L dopamine (the mass ratio of Cu-PI-Cu with a through-hole structure to dopamine is 50:1) into the solution. Irradiate the dopamine solution with a 36-watt ultraviolet lamp. Due to the self-polymerization reaction of dopamine under ultraviolet light assistance, the color of the solution turns dark brown; then scrape off the excess polydopamine on the surface with a spatula to ensure that the polydopamine is all in the holes, rinse the surface with ultrapure water, and dry it with N2, so that the first lithium-philic polymer material, polydopamine, fills the holes of the through-hole structure;

[0124] Immerse the PDA-modified copper foil into a quartz bottle containing an aqueous solution of acrylamide monomer with a mass fraction of 45% of acrylamide monomer. Degas it for 30 minutes with continuously dried nitrogen at room temperature, and seal the quartz bottle; irradiate it with a light source below 10 cm (simulating sunlight, a 300W xenon lamp) for 1 h, and keep the temperature at about 25 °C to graft the second lithium-philic polymer material on the surface of the holes of the first lithium-philic polymer material to obtain the current collector.

[0125] Example 3

[0126] This example provides a current collector, which includes:

[0127] A polymer layer, a polyimide (PI) film layer;

[0128] A metal layer, a copper layer, and the metal layer is located on both side surfaces of the polymer layer;

[0129] A through-hole structure, and the through-hole structure penetrates the polymer layer and the metal layer along the thickness direction of the current collector; the holes of the through-hole structure are filled with the first lithium-philic polymer material, polydopamine (PDA), and the first lithium-philic polymer material is grafted with the second lithium-philic polymer material, polyacrylamide (PAM), on the surface of the holes.

[0130] The thickness T1 of the polymer layer is 1 μm, and the thickness T2 of the metal layer is 3 μm;

[0131] In the through-hole structure, the aperture of the holes is 5 μm. Taking the direction perpendicular to the thickness direction of the current collector as the horizontal direction, the center distance of the holes of adjacent through-holes in the same horizontal direction is 1000 μm.

[0132] The preparation method of the current collector is as follows:

[0133] (1) 10 mmol of 4,4-diaminodiphenyl ether (ODA) and 10 mmol of pyromellitic dianhydride (PMDA) were successively dissolved in 40 mL of N,N-dimethylacetamide (DMAc) solvent. Under the protection of nitrogen (N2), the mixture was stirred at room temperature for 3 - 4 hours to obtain a polyamic acid (PAA) solution;

[0134] Then, a catalyst mixture solution prepared by mixing pyridine and propionic anhydride (pyridine was 3 wt% of PAA, and the molar ratio of propionic anhydride to PAA was 3:1) was quickly poured into the PAA solution. After stirring at room temperature for 5 minutes, spin coating was carried out; then it was placed in an oven and kept at 90 °C for 30 min until the solvent evaporated to obtain a PAA film. After heat treatment at 200 °C for 10 min and cooling to room temperature, a 1-μm-thick polyimide film (PI film) was obtained. The PI was cut into appropriate sizes and ultrasonically treated in absolute ethanol, 1 mol / L HCl solution, and deionized water for 5 min to remove surface oil stains and oxide films. The treated PI film was placed in the cavity of a vacuum evaporation coater (EB-400S, Ecopia), and a sufficient amount of target material (pure copper particles) was added. Metal copper layers with a thickness of 3 μm were plated on both sides of the PI film successively to obtain a Cu-PI-Cu composite current collector; A UV picosecond laser drilling machine (LASER06007) was used to prepare a through-hole structure with a pore diameter of 5 μm and a pitch of 1×1 mm along the thickness direction on the Cu-PI-Cu composite current collector. The laser wavelength used was 355 nm, and the spot focus diameter was 10 μm;

[0135] (2) A buffer solution with a pH of 8.5 was prepared from 0.0005 mol / L of tris(hydroxymethyl)aminomethane hydrochloride (Tris-HCl). The Cu-PI-Cu with a through-hole structure was repeatedly washed with deionized water to remove surface impurities. The clean Cu-PI-Cu with a through-hole structure was fixed at the bottom of an open container, and an appropriate amount of buffer solution was poured into the container. Then, a mixed solution of 1.5 g / L of SP and 1 g / L of dopamine (the mass ratio of Cu-PI-Cu with a through-hole structure to dopamine was 300:1) was added to the solution. The dopamine solution was irradiated with a 36-watt UV lamp. Due to the self-polymerization reaction of dopamine under UV assistance, the color of the solution turned dark brown; then the excess polydopamine on the surface was scraped off with a spatula to ensure that the polydopamine was all in the pores. The surface was rinsed with ultrapure water and dried with N2, so that the first lithium-philic polymer material, polydopamine, was filled in the pores of the through-hole structure;

[0136] The copper foil modified with PDA was immersed in a quartz bottle containing an aqueous solution of acrylamide monomer with a mass fraction of 25% of acrylamide monomer. Degassing treatment was carried out for 30 minutes with continuously dried nitrogen at room temperature, and then the quartz bottle was sealed. Irradiation was carried out for 1 h under a light source below 10 cm (simulating sunlight, 300 W xenon lamp), and the temperature was maintained at about 25 °C, so that a second lithiumophilic polymer material was grafted onto the surface of the pores of the first lithiumophilic polymer material to obtain the current collector.

[0137] Example 4

[0138] This example provides a current collector, which includes:

[0139] A polymer layer, a polyimide (PI) film layer;

[0140] A metal layer, a copper layer, and the metal layer is located on both side surfaces of the polymer layer;

[0141] A through-hole structure, and the through-hole structure penetrates through the polymer layer and the metal layer along the thickness direction of the current collector; the pores of the through-hole structure are filled with a first lithiumophilic polymer material, polydopamine (PDA), and a second lithiumophilic polymer material, polyacrylamide (PAM), is grafted onto the surface of the pores of the first lithiumophilic polymer material.

[0142] The thickness T1 of the polymer layer is 2 μm, and the thickness T2 of the metal layer is 2 μm;

[0143] In the through-hole structure, the aperture of the pores is 20 μm. Taking the direction perpendicular to the thickness direction of the current collector as the horizontal direction, the center distance of the pores of adjacent through-holes in the same horizontal direction is 1000 μm.

[0144] The preparation method of the current collector is as follows:

[0145] (1) 10 mmol of 4,4-diaminodiphenyl ether (ODA) and 10 mmol of pyromellitic dianhydride (PMDA) were successively dissolved in 40 mL of N,N-dimethylacetamide (DMAc) solvent, and stirred at room temperature for 3 - 4 hours under the protection of nitrogen (N2) to obtain a polyamic acid (PAA) solution;

[0146] Then, the catalyst mixture solution prepared by mixing pyridine and propionic anhydride (pyridine is 3 wt% of PAA, and the molar ratio of propionic anhydride to PAA is 3:1) was quickly poured into the PAA solution, stirred at room temperature for 5 minutes, and then spin-coated; subsequently, it was placed in an oven, kept at 90 °C for 30 min until the solvent evaporated to obtain a PAA film, and then heat-treated at 200 °C for 10 min, cooled to room temperature to obtain a 2-μm-thick polyimide film (PI film). The PI was cut into appropriate sizes, ultrasonically treated in absolute ethanol, 1 mol / L HCl solution, and deionized water for 5 min to remove surface oil stains and oxide films. The treated PI film was placed in the cavity of a vacuum evaporation coater (EB-400S, Ecopia), and a sufficient amount of target material (pure copper particles) was added. Metal copper layers with a thickness of 2 μm were plated on both sides of the PI film in sequence to obtain a Cu-PI-Cu composite current collector; a UV picosecond laser drilling machine (LASER06007) was used to prepare a through-hole structure with a pore diameter of 20 μm and a pitch of 1×1 mm along the thickness direction on the Cu-PI-Cu composite current collector. The laser wavelength used was 355 nm, and the spot focus diameter was 10 μm;

[0147] (2) Prepare a buffer solution with a pH of 8.5 from 0.002 mol / L tris(hydroxymethyl)aminomethane hydrochloride (Tris-HCl), and repeatedly wash the Cu-PI-Cu with a through-hole structure with deionized water to remove impurities on its surface. Fix the clean Cu-PI-Cu with a through-hole structure at the bottom of an open container, pour an appropriate amount of buffer solution into the container, and then add a mixed solution of 3 g / L SP and 2 g / L dopamine to the solution. Irradiate the dopamine solution with a 36-watt UV lamp. Due to the self-polymerization reaction of dopamine under UV assistance, the color of the solution turned dark brown; then, scrape off the excess polydopamine on the surface with a spatula to ensure that the polydopamine is all in the pores, rinse the surface with ultrapure water, and dry it with N2, so that the first lithium-philic polymer material, polydopamine, fills the pores of the through-hole structure;

[0148] Immerse the PDA-modified copper foil in a quartz bottle containing an aqueous solution of acrylamide monomer with a mass fraction of 45% of acrylamide monomer, degas it for 30 minutes with continuously dried nitrogen at room temperature, and seal the quartz bottle; irradiate it with a light source below 10 cm (simulating sunlight, 300 W xenon lamp) for 1 h, and keep the temperature at about 25 °C to graft a second lithium-philic polymer material on the surface of the pores of the first lithium-philic polymer material to obtain the current collector.

[0149] Example 5

[0150] This example provides a current collector, which includes:

[0151] A polymer layer, a polyimide (PI) film layer;

[0152] A metal layer, a copper layer, the metal layer being located on both side surfaces of the polymer layer;

[0153] A via hole structure, the via hole structure penetrating through the polymer layer and the metal layer along the thickness direction of the current collector; the holes of the via hole structure are filled with a first lithium-philic polymer material, polydopamine (PDA), and a second lithium-philic polymer material, polyacrylamide (PAM), is grafted onto the surface of the holes of the first lithium-philic polymer material.

[0154] The thickness T1 of the polymer layer is 3 μm, and the thickness T2 of the metal layer is 1 μm;

[0155] In the via hole structure, the aperture of the holes is 5 μm. Taking the direction perpendicular to the thickness direction of the current collector as the horizontal direction, the center distance between the holes of adjacent vias in the same horizontal direction is 500 μm.

[0156] The preparation method of the current collector is as follows:

[0157] (1) Dissolve 10 mmol of 4,4-diaminodiphenyl ether (ODA) and 10 mmol of pyromellitic dianhydride (PMDA) successively in 40 mL of N,N-dimethylacetamide (DMAc) solvent. Under the protection of nitrogen (N2), stir at room temperature for 3 - 4 hours to obtain a polyamic acid (PAA) solution;

[0158] Then, quickly pour a catalyst mixture prepared by mixing pyridine and propionic anhydride (pyridine is 3 wt% of PAA, and the molar ratio of propionic anhydride to PAA is 3:1) into the PAA solution, stir at room temperature for 5 minutes and then perform spin coating; then place it in an oven, keep it at 90 °C for 30 min until the solvent evaporates to obtain a PAA film, and then heat-treat it at 200 °C for 10 min, cool it to room temperature to obtain a 3-μm-thick polyimide film (PI film). Cut the PI into corresponding sizes, ultrasonically clean it in absolute ethanol, 1 mol / L HCl solution, and deionized water for 5 min to remove surface oil stains and oxide films. Put the treated PI film into the cavity of a vacuum evaporation coater (EB-400S, Ecopia), add a sufficient amount of target material (pure copper particles), and deposit 1-μm-thick metal copper layers on both sides of the PI film successively to obtain a Cu-PI-Cu composite current collector; use an ultraviolet picosecond laser drilling machine (LASER06007) to prepare via hole structures with an aperture of 5 μm and a spacing of 0.5×0.5 mm along the thickness direction for the Cu-PI-Cu composite current collector (as Figure 1 shown), the laser wavelength used is 355 nm, and the spot focus diameter is 10 μm;

[0159] (2) Prepare a buffer solution with a pH of 8.5 using 0.002 mol / L tris(hydroxymethyl)aminomethane hydrochloride (Tris-HCl). Repeatedly wash the Cu-PI-Cu with a through-hole structure with deionized water to remove impurities on its surface. Fix the clean Cu-PI-Cu with a through-hole structure at the bottom of an open container, pour an appropriate amount of the buffer solution into the container, and then add a mixed solution of 3 g / L SP and 2 g / L dopamine to the solution. Irradiate the dopamine solution with a 36-watt ultraviolet lamp. Due to the self-polymerization reaction of dopamine under ultraviolet light assistance, the color of the solution turns dark brown; then use a spatula to scrape off the excess polydopamine on the surface to ensure that the polydopamine is all in the holes, rinse the surface with ultrapure water, and dry it with N2, so that the first lithiumophilic polymer material, polydopamine, fills the holes of the through-hole structure;

[0160] Immerse the PDA-modified copper foil in a quartz bottle containing an aqueous solution of acrylamide monomer with a mass fraction of 25% of acrylamide monomer. Degas it for 30 minutes with continuously dried nitrogen at room temperature, and seal the quartz bottle; irradiate it with a light source below 10 cm (simulating sunlight, a 300W xenon lamp) for 1 h, and keep the temperature at about 25 °C to graft a second lithiumophilic polymer material onto the surface of the holes of the first lithiumophilic polymer material to obtain the current collector.

[0161] Example 6

[0162] The difference between this example and Example 1 is that the polymer in the polymer layer of this example is polyethylene terephthalate (PET), and the first lithiumophilic polymer material is polyvinyl alcohol.

[0163] In the preparation method, directly select a PEI film for evaporation plating of a metal copper layer;

[0164] The monomer of the first lithiumophilic polymer is vinyl alcohol.

[0165] The rest of the preparation methods and parameters are the same as those in Example 1.

[0166] Example 7

[0167] The difference between this example and Example 1 is that in the through-hole structure of this example, the pore size is 3 μm.

[0168] In the preparation method, just adaptively adjust the parameters for pore formation.

[0169] The rest of the preparation methods and parameters are the same as those in Example 1.

[0170] Example 8

[0171] The difference between this example and Example 1 is that in the through-hole structure of this example, the pore size is 25 μm.

[0172] In the preparation method, the parameters for pore formation can be adjusted adaptively.

[0173] The remaining preparation methods and parameters are the same as those in Example 1.

[0174] Example 9

[0175] The difference between this example and Example 1 is that the thickness T1 of the polymer layer in this example is 0.5 μm.

[0176] The remaining preparation methods and parameters are the same as those in Example 1.

[0177] Example 10

[0178] The difference between this example and Example 1 is that the thickness T1 of the polymer layer in this example is 5 μm.

[0179] The remaining preparation methods and parameters are the same as those in Example 1.

[0180] Example 11

[0181] The difference between this example and Example 1 is that the thickness T2 of the metal layer in this example is 0.5 μm.

[0182] The remaining preparation methods and parameters are the same as those in Example 1.

[0183] Example 12

[0184] The difference between this example and Example 1 is that the thickness T2 of the metal layer in this example is 5 μm.

[0185] The remaining preparation methods and parameters are the same as those in Example 1.

[0186] Example 13

[0187] The difference between this example and Example 1 is that this example does not contain the second lithiumophilic polymer material PMA.

[0188] In the preparation method, after the first lithiumophilic polymer material polydopamine is filled into the holes of the through-hole structure, the reaction is terminated.

[0189] The remaining preparation methods and parameters are the same as those in Example 1.

[0190] Example 14

[0191] The difference between this example and Example 1 is that in this example, the mass ratio of Cu-PI-Cu with a through-hole structure to dopamine is 350:1.

[0192] The remaining preparation methods and parameters are the same as those in Example 1.

[0193] Comparative Example 1

[0194] The difference between this comparative example and Example 1 is that the current collector provided in this comparative example has no through-hole structure and is not modified with the first lithium-philic polymer material and the second lithium-philic polymer material.

[0195] In the preparation method, after obtaining a Cu-PI-Cu composite current collector without pores, the reaction was terminated to obtain the current collector.

[0196] The remaining preparation methods and parameters are the same as those in Example 1.

[0197] Comparative Example 2

[0198] The difference between this comparative example and Example 1 is that in the current collector provided in this comparative example, the through-hole structure is filled with the second lithium-philic polymer material and does not contain the first lithium-philic material.

[0199] In step (2) of the preparation method, the Cu-PI-Cu with a through-hole structure was immersed in a quartz bottle containing an aqueous solution of acrylamide monomer. The mass fraction of acrylamide monomer was 35%. Degassing treatment was carried out for 30 minutes with continuously dried nitrogen at room temperature, and then the quartz bottle was sealed. Irradiation was carried out for 1 h under a light source below 10 cm (simulating sunlight, 300 W xenon lamp), and the temperature was maintained at about 25 °C to fill the holes in the through-hole structure with the second lithium-philic polymer material to obtain the current collector.

[0200] Comparative Example 3

[0201] The difference between this comparative example and Example 1 is that in the current collector provided in this comparative example, there is no through-hole structure, and the first lithium-philic polymer material is located on the surface of the metal layer away from the polymer layer.

[0202] In the preparation method, the pore-forming process in step (1) is not carried out, and the scraping process in step (2) is not carried out.

[0203] The remaining preparation methods and parameters are the same as those in Example 1.

[0204] The current collectors provided by the examples with a copper layer as the metal layer and the comparative examples were used to prepare a non-negative electrode battery structure and the battery performance was tested.

[0205] i) Preparation of non-negative electrode battery structure:

[0206] The prepared composite current collector was used as the non-negative electrode current collector, that is, the negative electrode plate, and the size of the current collector was (100 mm × 55 mm).

[0207] Preparation of the positive electrode sheet: Using NCM811 as the positive electrode active material, carbon black as the conductive agent, and PVDF as the binder, the positive electrode active material, conductive agent, and binder are mixed in a mass ratio of 97:1:2. Add N-methylpyrrolidone (NMP) to prepare the positive electrode slurry, control the solid content to be 65% - 70%. Use 12μm aluminum foil as the positive electrode current collector, and adopt the coating and drying methods to prepare the positive electrode sheet. The size of the positive electrode sheet is 96mm × 51mm.

[0208] Celgard2320 microporous polypropylene film is used as the separator; the electrolyte is 1mol / L LiPF6, dissolved in a mixture of ethylene carbonate (EC) and diethyl carbonate (DEC) in a volume ratio of 1:1;

[0209] The capacity ratio of the positive electrode to the negative electrode is 1. The assembly process is carried out by the soft-pack stacking method. Stacking: Stack the positive electrode sheet, separator, and negative electrode current collector in sequence to obtain the battery cell; then assemble: After hot-pressing the stacked battery cell, put it into the aluminum-plastic film, perform top and side sealing, inject the electrolyte into the battery, seal the battery after injection, the injection coefficient is 3g / Ah, and carry out formation treatment on the packaged battery to obtain the battery to be tested.

[0210] ii) Performance testing:

[0211] Perform performance testing on the batteries of the prepared examples and comparative examples:

[0212] (a) Energy density: First, weigh the battery of each group of tests to obtain the mass of the battery, denoted as m. Then, at 25°C, charge the battery at a constant current of 0.1C to 4.25V, and then charge at a constant voltage of 4.25V until the current ≤ 0.05C. After standing for 5 minutes, discharge at a constant current of 0.1C to 2.8V to obtain the discharge energy Q. The calculation method of the battery energy density is Q / m.

[0213] (b) Initial efficiency and cycle performance: The charge and discharge cut-off voltages are 2.8 - 4.2V, the charge and discharge current is 1A / g, and the test ends after 2000 cycles.

[0214] (c) Test method for the peak temperature of thermal runaway: According to T / CSAE 344—2024 "Test Method for Adiabatic Calorimetry of Thermal Runaway of Lithium-Ion Power Batteries".

[0215] The test results of the above tests are shown in Table 1.

[0216] Table 1

[0217]

[0218] In summary, in the current collector provided by the present invention, the structure of the composite polymer between the two metal layers endows the current collector with excellent mechanical flexibility, making it not easily break. Even if it breaks, it cannot reach the standard of piercing the separator, thus better avoiding the risks inside the battery and reducing the probability of thermal runaway. At the same time, the specific structural cooperation between the polymer and the metal layer can effectively reduce the thickness of the metal layer, making the density of the specific composite layer structure much lower than that of the pure metal layer, significantly improving the energy density of the battery. The first lithiophilic polymer material interacts with the polymer in the current collector through hydrogen bonds and van der Waals forces, thus firmly fixing in the through-hole structure of the current collector. On the one hand, it promotes the uniform deposition of lithium ions, and on the other hand, it fills the through-hole structure, compensating for the conductivity caused by the opening. The through-hole structure ensures the conductivity connection between the front and back sides of the current collector and further reduces the weight of the current collector. That is, through the synergistic effect of the specific structure and materials, the present invention ensures the good performance of the conductivity of the current collector, improves the energy density and thermal stability of the battery, promotes the uniform deposition of lithium ions, and thus improves the initial efficiency and cycle performance of the battery.

[0219] The applicant declares that the above description is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of within the technical scope disclosed by the present invention by any person skilled in the art of this technology fall within the protection scope and the public disclosure scope of the present invention.

Claims

1. A current collector, characterized in that: The current collector comprises: polymer layer; A metal layer, wherein the metal layer is located on both side surfaces of the polymer layer; a through-hole structure, wherein the through-hole structure penetrates the polymer layer and the metal layer along the thickness direction of the current collector; The holes of the through-hole structure are filled with a first lithium-philic polymer material, which is a photoinitiator; the first lithium-philic polymer material interacts with the polymer in the polymer layer through hydrogen bonds and van der Waals forces; the first lithium-philic polymer material is grafted with a second lithium-philic polymer material on the surface of the hole, and the second lithium-philic polymer material also has a nanobrush structure.

2. The current collector according to claim 1, characterized in that: The polymer layer satisfies at least one of the following conditions (a) to (b): (a) the polymer material in the polymer layer includes any one or a combination of at least two of polyimide, polyvinylidene fluoride, polypropylene, polyethylene, polyethylene terephthalate, polymethyl methacrylate, polyethylene oxide or polyvinyl alcohol; (b) The weight average molecular weight of the polymer in the polymer layer is 5,000 to 50,000.

3. The current collector according to claim 1, characterized in that: The thickness T1 of the polymer layer and the thickness T2 of the metal layer satisfy at least one of the following conditions (c) to (f): (c) 2μm≤T1+T2≤6μm; (d) 1 / 6≤T1 / T1+T2≤1 / 2; (e) T1 is 1~3μm; (f) T2 is 1~3μm.

4. The current collector according to claim 1, characterized in that: The pore size of the through-hole structure is 5-20 μm; and / or, Taking the thickness direction perpendicular to the current collector as the horizontal direction, the hole center distance between adjacent through holes in the same horizontal direction is 500-5000 μm.

5. The current collector according to claim 1, characterized in that: The first lithium-philic polymer material includes any one of polydopamine, polyethylene oxide, polyvinyl alcohol or polyacrylamide, or a combination of at least two thereof; and / or, The second lithium-philic polymer material includes any one of polydopamine, polyethylene oxide, polyvinyl alcohol or polyacrylamide, or a combination of at least two thereof.

6. A method for preparing a current collector according to any one of claims 1 to 5, characterized in that: The preparation method comprises the following steps: Compounding metal layers on both sides of the polymer layer to obtain a composite structure; Performing pore formation along the thickness direction of the composite structure to obtain a through-hole structure penetrating the polymer layer and the metal layer; The holes of the through-hole structure are filled with a first lithium-philic polymer material to obtain the current collector.

7. The preparation method according to claim 6, characterized in that: The method of composite metal layer comprises vacuum evaporation method.

8. The preparation method according to claim 6, characterized in that: The first lithium-philic polymer material is filled in the holes of the through-hole structure by an in-situ polymerization method; and / or, The first lithium-philic polymer material is grafted with a second lithium-philic polymer material on the surface of the pores, and the grafting method includes in-situ grafting.

9. The preparation method according to claim 8, characterized in that: The in-situ grafting method comprises: The first lithiophilic polymer material is used as a photoinitiator, and the monomer of the second lithiophilic polymer material is grafted with the first lithiophilic polymer material by light irradiation, so that the first lithiophilic polymer material is grafted with the second lithiophilic polymer material on the surface of the hole.

10. A battery, characterized in that: The battery comprises the current collector according to any one of claims 1 to 5 or the current collector prepared by the preparation method according to any one of claims 6 to 9.

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