Composite aluminum material and preparation method therefor, battery negative electrode material, and battery

Abstract

Disclosed are a composite aluminum material and a preparation method therefor, a battery negative electrode material, and a battery. The composite aluminum material comprises an aluminum sheet and a twin-crystal metal material coated on the upper surface and the lower surface of the aluminum sheet. The design of the sheet structure allows for surface-to-surface contact between aluminum materials, thereby reducing contact resistance between the materials. The twin-crystal metal coating serves as an oxygen barrier to prevent rapid oxidation of the aluminum materials in air, and has good dual conduction capability for ions and electrons, thereby facilitating coupling of the electrons and the ions in the aluminum negative electrode material. Finally, the structural design effectively mitigates the electrochemical polarization problem of the small-sized aluminum negative electrode material, thereby facilitating activation of the electrochemical performance thereof. In addition, the present invention further provides a composite aluminum sheet having a twin-crystal metal coating, which is prepared in a bottom-up manner; and an aluminum metal film is deposited on a carbon-coated polymer film substrate by means of a physical vapor deposition method, such that the problem of continuous oxidation of an aluminum sheet in a bottom-up preparation process is solved.

Description

Composite aluminum material and preparation method thereof, battery negative electrode material and battery Technical Field

[0001] The present invention relates to the technical field of energy storage materials, and in particular to a composite aluminum material and a preparation method thereof, a battery negative electrode material and a battery. Background Art

[0002] Lithium-ion batteries are widely used in consumer electronics and energy storage. With the development of technology, the capacity requirements for lithium-ion batteries are getting higher and higher. At present, the most widely used graphite anode material in lithium-ion batteries has gradually approached its theoretical specific capacity (372mAh g -1 ). Therefore, it is imperative to develop new low-cost and high-capacity negative electrode materials. Aluminum metal negative electrode has a high theoretical specific capacity (993mAh g -1 ) and energy density, becoming a potential next-generation lithium-ion battery negative electrode material.

[0003] In the related art, due to the high activity of aluminum metal, it is very easy to form an electronically insulating oxide layer in the air, and as the size of the aluminum metal decreases, the volume proportion of the oxide layer also increases. In the process of aluminum metal miniaturization, the reduction in aluminum size is accompanied by an increase in the volume proportion of aluminum oxide on its surface, resulting in a large ohmic polarization of small-sized aluminum materials when used as negative electrode materials for lithium-ion batteries. The aluminum negative electrode cannot form effective electron-ion coupling, resulting in its electrochemical performance being unable to be fully utilized, with disadvantages such as large polarization, unclear charge and discharge platform, and low actual specific capacity. On the other hand, the high activity of aluminum metal also determines that its miniaturization is mainly achieved through top-down preparation methods, such as mechanical milling, evaporation condensation and laser ablation; the aluminum powder of micron size and below prepared by the above methods is often granular, and the contact between aluminum particles is mainly point contact; and this point contact conductive form causes a large contact resistance between aluminum particles. When small-sized aluminum metal is used as a negative electrode material, it will cause severe polarization due to the large ohmic impedance.

[0004] Therefore, it is of great significance to solve the serious electrochemical polarization problem of aluminum negative electrode materials under small size, reduce the contact resistance between materials, and improve their electrochemical performance.

[0005] Summary of the Invention

[0006] The present invention aims to address at least one of the technical problems existing in the prior art. To this end, the present invention provides a composite aluminum material, a preparation method thereof, a battery anode material, and a battery, aiming to address the severe electrochemical polarization issues, high contact resistance between materials, and insufficient electrochemical performance currently encountered in small-sized aluminum anode materials.

[0007] In a first aspect of the present invention, a composite aluminum material is proposed, comprising an aluminum sheet and a twin metal material; the twin metal material is coated on the upper and lower surfaces of the aluminum sheet to form an upper twin metal coating layer and a lower twin metal coating layer.

[0008] The composite aluminum material according to the embodiment of the present invention has at least the following beneficial effects: The present invention proposes a sheet-like composite aluminum material with a twin metal coating, the structural design of which consists of three parts, namely an upper twin metal coating layer, an aluminum sheet and a lower twin metal coating layer, and the aluminum sheet is located between the upper twin metal coating layer and the lower twin metal coating layer, forming a "sandwich" structure, as shown in Figure 1. Among them, the aluminum metal material (i.e., "aluminum sheet" or "sheet aluminum") in the sheet structure in the middle has a size of microns and below, which can well adapt to the volume expansion problem generated when the aluminum material is used as a negative electrode material. The twin boundaries existing in the twin metal provide a path for the transmission of ions, realizing electron-ion dual conduction, and the twin metal coating on the upper and lower surfaces of the aluminum sheet plays the role of oxygen isolation and electron-ion dual conduction. On the one hand, when sheet-like aluminum materials are used as negative electrode materials, the contact between the sheets is mainly in the form of surface contact, which greatly reduces the contact resistance between the materials, significantly improves the conductivity of small-sized aluminum materials, and greatly reduces the polarization problem caused by the material when used as a negative electrode material. On the other hand, twin metals have good dual conductivity of ions and electrons. The design of twin metal coating can not only play a good oxygen barrier role, preventing the rapid oxidation of aluminum materials in the air; it can also make the electron-ion transmission unaffected, which is conducive to the coupling of electrons and ions in the aluminum material. Therefore, the sheet-like composite aluminum material with a twin metal coating design can greatly reduce the polarization problem caused by the ohmic impedance between aluminum materials when the aluminum material is used as a negative electrode material, and activate its electrochemical performance.

[0009] In some embodiments of the present invention, the aluminum flakes comprise aluminum micron flakes or aluminum nanoflakes, each having an adjustable thickness and a diameter significantly greater than its thickness. The aluminum flakes are sized at or below the micron level, effectively accommodating the volume expansion issues associated with aluminum materials used as negative electrode materials. When used as negative electrode materials, the sheet-like aluminum nanoflakes or aluminum microflakes primarily maintain surface contact, significantly reducing contact resistance between the materials and significantly improving the electrical conductivity of small-sized aluminum materials, significantly reducing polarization issues associated with their use as negative electrode materials.

[0010] In some embodiments of the present invention, the thickness of the aluminum sheet is 1 nm to 100 μm.

[0011] In some preferred embodiments of the present invention, the thickness of the aluminum sheet is 100 nm to 500 nm, for example, 100 nm, 200 nm, 300 nm, 400 nm, or 500 nm.

[0012] In some more preferred embodiments of the present invention, the thickness of the aluminum flake is about 500 nm.

[0013] In some embodiments of the present invention, the diameter of the aluminum sheet is 1 μm to 200 μm.

[0014] In some preferred embodiments of the present invention, the diameter of the aluminum sheet is 10 μm to 100 μm, for example, it can be 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, or 100 μm.

[0015] In some more preferred embodiments of the present invention, the diameter of the aluminum flakes is about 10 μm.

[0016] In some embodiments of the present invention, the twinned metal coating refers to coating the upper and lower surfaces of an aluminum sheet with a twinned metal material to form a "sandwich" structure, with the coating thickness being less than 1 / 10 of the thickness of the aluminum sheet. The twinned metal material refers to a metal material having a twinned structure. The twin boundaries in the twinned metal provide a path for ion transport, achieving electron-ion dual conduction. The twinned metal coating is applied to the upper and lower surfaces of the aluminum sheet, with a thickness less than 1 / 10 of the thickness of the aluminum sheet, providing oxygen isolation and electron-ion dual conduction.

[0017] In some embodiments of the present invention, the twinned metal material is selected from a single element material composed of a single element in the I to VII subgroups, the VIII group, the III main group, and the IV main group, or an alloy or composite material composed of multiple elements; but not limited to this, any metal material with a twinned structure can be used.

[0018] In some preferred embodiments of the present invention, the twinned metal material is selected from a single material composed of one of copper, titanium, zinc, nickel, and chromium, or an alloy or composite material composed of multiple elements.

[0019] In some more preferred embodiments of the present invention, the twinned metal material is selected from metal titanium, metal zinc, metal nickel, metal chromium, zinc-titanium alloy, and zinc-copper alloy.

[0020] In some embodiments of the present invention, the thickness of the upper twinned metal cladding layer is 1 nm to 300 nm.

[0021] In some preferred embodiments of the present invention, the thickness of the upper twin metal coating layer is 1 nm to 50 nm, for example, 1 nm, 5 nm, 10 nm, 20 nm, 30 nm, 40 nm, or 50 nm.

[0022] In some more preferred embodiments of the present invention, the thickness of the upper twinned metal cladding layer is about 50 nm.

[0023] In some embodiments of the present invention, the thickness of the lower twin metal cladding layer is 1 nm to 300 nm.

[0024] In some preferred embodiments of the present invention, the thickness of the lower twin metal coating layer is 1 nm to 50 nm, for example, 1 nm, 5 nm, 10 nm, 20 nm, 30 nm, 40 nm, or 50 nm.

[0025] In some more preferred embodiments of the present invention, the thickness of the lower twinned metal cladding layer is about 50 nm.

[0026] In some embodiments of the present invention, the thickness of the composite aluminum material is between 100 nm and 100 μm. The composite aluminum material has a thickness of nanosheets, microsheets, or submicrometer sheets. The thickness of the composite aluminum material is related to the thickness of the aluminum sheet and the thickness of the twinned metal cladding layer. For example, if the thickness of the aluminum sheet is 500 nm, and the thickness of the upper twinned metal cladding layer and the thickness of the lower twinned metal cladding layer are both 50 nm, then the thickness of the composite aluminum material is 600 nm. This will not be further elaborated here.

[0027] The second aspect of the present invention provides a method for preparing a composite aluminum material, comprising the steps of:

[0028] S1. Providing a polymer film substrate and cleaning the polymer film substrate;

[0029] S2, performing carbon plating pre-treatment on the cleaned polymer film substrate to obtain a carbon-plated polymer film substrate;

[0030] S3, using physical vapor deposition technology to sequentially deposit a lower twinned metal film layer, an aluminum metal film layer, and an upper twinned metal film layer on the surface of the carbon-coated polymer film substrate to form a composite aluminum metal film with a sandwich structure;

[0031] S4. After the carbon-coated polymer film substrate on which the composite aluminum metal film is deposited is allowed to stand for a period of time, the substrate is placed in an organic solvent for ultrasonic treatment to peel off the carbon-coated polymer film, and then the organic solvent is removed to obtain the composite aluminum material.

[0032] The preparation method of the composite aluminum material according to the embodiment of the present invention has at least the following beneficial effects: the high activity of aluminum makes it difficult to prepare small-sized aluminum materials by a bottom-up method; the traditional top-down preparation method (such as mechanical milling, evaporation condensation and laser ablation) will result in a large waste of materials, and it is impossible to control the morphology of the material from the atomic or molecular perspective. The particle size and morphology of the prepared material are poorly consistent, and it is difficult to protect the material during the preparation process. The prepared aluminum nanomaterial usually has a thick oxide layer, resulting in low electronic conductivity of the material. Based on this, the present invention proposes a bottom-up preparation method to prepare a small-sized aluminum material with a sheet structure (i.e., the "aluminum sheet"): a physical vapor deposition method is used to deposit an aluminum metal film on a carbon-coated polymer film substrate. The carbon coating of the polymer substrate facilitates the peeling of the aluminum metal film. After a simple ultrasonic treatment, an aluminum sheet with adjustable thickness can be prepared from the bottom up. The physical vapor deposition preparation method provides a high vacuum environment for the growth of the aluminum sheet, solving the problem of continuous oxidation of the aluminum sheet during the bottom-up preparation process. The carbon-coated polymer film provides a good substrate for the growth and collection of aluminum flakes: it not only has a low thermal expansion coefficient and excellent thermal stability, and can withstand the high temperature of aluminum metal during the physical vapor deposition process; it is also conducive to the peeling of the prepared aluminum metal film, making it easy to ultrasonically form aluminum flakes after peeling.

[0033] In some embodiments of the present invention, the physical vapor deposition technology includes vacuum evaporation coating technology, vacuum magnetron sputtering technology, and ion plating technology, but is not limited thereto.

[0034] In some embodiments of the present invention, the polymer film substrate includes polyimide (PI) film, carbonate (PC) film, polyethylene terephthalate (PET) film, polypropylene (PP) film, polyethylene (PE) film, polyvinyl chloride (PVC) film, polytetrafluoroethylene (PTFE) film, polystyrene (PS) film, polyvinylidene fluoride (PVDF) film, but is not limited thereto.

[0035] In some preferred embodiments of the present invention, the polymer film substrate is selected from pyrophenyl polyimide films.

[0036] In some embodiments of the present invention, the thickness of the polymer film substrate is 3 μm to 100 μm.

[0037] In some preferred embodiments of the present invention, the thickness of the polymer film substrate is 10 μm to 25 μm.

[0038] In some more preferred embodiments of the present invention, the thickness of the polymer film substrate is about 25 μm.

[0039] In some embodiments of the present invention, in step S1, the polymer film substrate is ultrasonically cleaned using an organic solution, and the organic solution includes but is not limited to methanol, ethanol, and acetone.

[0040] In some embodiments of the present invention, in step S2, the cleaned polymer film substrate is subjected to carbon coating pretreatment using a physical vapor deposition technique to obtain a carbon-coated polymer film substrate. The physical vapor deposition technique includes, but is not limited to, vacuum evaporation coating technique, vacuum magnetron sputtering technique, and ion plating technique.

[0041] In some embodiments of the present invention, the carbon plating pre-treatment includes plating an amorphous carbon layer on the surface of the polymer film substrate, and the thickness of the amorphous carbon layer is 1 nm to 50 nm.

[0042] In some preferred embodiments of the present invention, the thickness of the amorphous carbon layer is 10 nm to 20 nm.

[0043] In some more preferred embodiments of the present invention, the thickness of the amorphous carbon layer is about 10 nm.

[0044] In some embodiments of the present invention, in step S3, a physical vapor deposition technique is used to control process parameters to first deposit a twinned metal film layer (a lower twinned metal film layer) on the surface of the carbon-coated polymer film substrate, followed by depositing an aluminum metal film layer, and finally depositing another twinned metal film layer (an upper twinned metal film layer), ultimately forming a twinned metal-coated composite aluminum metal film having a sandwich structure. The physical vapor deposition technique includes, but is not limited to, vacuum evaporation coating technology, vacuum magnetron sputtering technology, and ion plating technology.

[0045] In some embodiments of the present invention, the twin metal is achieved by controlling the process parameters and deposition time of the preparation. For example, in a specific embodiment of the present invention, a composite aluminum submicron sheet with a twin copper metal coating layer is prepared by magnetron sputtering technology, the thickness of the twin copper metal coating layer is 50nm, and the thickness of the corresponding aluminum metal layer is 500nm. The specific preparation process is as follows: (1) Use 95% ethanol to ultrasonically clean the polyimide film, and after sufficient drying, stick it on the circular roller of the magnetron sputtering instrument, then heat the vacuum coating chamber of the magnetron sputtering instrument to 200℃, and then evacuate it to a pressure of 10 -4Pa. (2) A carbon target with a purity of 99.99% was selected, the deposition power was 1KW, and argon gas with a flow rate of 300sccm was introduced into the vacuum coating chamber to perform carbon coating pretreatment on the polyimide film. The coating steps are as follows: open under a bias voltage of 50V, deposit for 5 minutes, obtain the polyimide film after carbon coating pretreatment, and then cool to room temperature. (3) A copper target and an aluminum target with a purity of 99.99% were selected, the deposition power of copper was 1KW, and the deposition power of aluminum was 2KW. Argon gas with a flow rate of 300sccm was introduced into the vacuum coating chamber, the vacuum coating chamber of the magnetron sputtering instrument was heated to 200℃, and then the pressure was evacuated to 10 -4 Pa. The coating steps are as follows: first turn on the copper target under a bias of 50V and deposit on the polyimide film after interface modification for 2 minutes, then turn on the aluminum target and keep the aluminum target turned on until the 27th minute, turn on the copper target again, and turn off the copper target after 2 minutes to obtain an aluminum metal film with a twinned copper metal coating layer deposited on the polyimide film. (4) Take out the polyimide film on which the composite aluminum metal film is deposited, place it in a dry environment at room temperature and let it stand for 48 hours, then gently fold the polyimide film and put it into anhydrous ethanol to ultrasonically peel off the composite aluminum metal film attached to the polyimide substrate. After taking out the polyimide film, aluminum submicron sheets with a twinned copper metal coating layer dispersed in anhydrous ethanol are obtained. (4) The anhydrous ethanol soaked with aluminum composite sub-nano sheets is filtered. Nylon filter paper with a filtration pore size of 40nm is selected. After the filtration is completed, it is placed in a vacuum drying oven and dried for 8 hours to obtain a composite aluminum submicron sheet with a twinned copper metal coating layer. It should be noted that the above examples are only for better illustrating the specific process parameters of the preparation and should not be regarded as any limitation of the present invention. Those skilled in the art can reasonably determine the specific process parameters according to factors such as the type of metal and coating thickness in actual operation.

[0046] In some embodiments of the present invention, in step S4, the static treatment refers to placing the composite aluminum sheet in a dry indoor environment at a temperature range of -40°C to 35°C for 1 to 48 hours, preferably at 25°C for 24 hours. The organic solvent includes, but is not limited to, ethanol, acetone, and benzene. Any solvent that does not react with the prepared composite aluminum sheet at room temperature can be used. Removal of the organic solvent is performed by filtration.

[0047] In a third aspect of the present invention, a battery negative electrode material is provided, comprising a negative electrode active material, a conductive agent and a binder, wherein the negative electrode active material is the above-mentioned composite aluminum material or the composite aluminum material prepared using the above-mentioned preparation method.

[0048] The battery negative electrode material according to the embodiment of the present invention has at least the following beneficial effects: the battery negative electrode material proposed in the present invention has a structural design of a sheet-like composite aluminum material with a twin metal coating as its negative electrode active material. The sheet-like structure design realizes that the contact between the aluminum materials is in the form of surface contact, which greatly reduces the contact resistance between the nano-scale or micron-scale aluminum materials when used as negative electrode materials from the material perspective. Twin metals have good dual conductivity of ions and electrons. The design of the twin metal coating can not only play a good oxygen isolation role, preventing the aluminum material from rapidly oxidizing in the air; it can also make the electron-ion transmission unaffected, which is conducive to the coupling of electrons and ions in the aluminum negative electrode material. Therefore, the structural design of the sheet-like composite aluminum negative electrode material with twin metal coating effectively reduces the polarization of the nano-scale or micron-scale aluminum-based negative electrode material, and effectively activates the electrochemical activity of the nano-scale or micron-scale aluminum-based negative electrode material. A corresponding preparation method was also proposed, using a bottom-up preparation method to prepare a composite aluminum negative electrode material with twin metal coating: physical vapor deposition is used to deposit an aluminum metal film on a carbon-coated polymer film substrate. The carbon coating of the polymer substrate facilitates the peeling of the aluminum metal film. After a simple ultrasonic treatment, aluminum flakes with adjustable thickness can be prepared from the bottom up. The physical vapor deposition preparation method provides a high vacuum environment for the growth of the aluminum flakes, solving the problem of continuous oxidation of the aluminum flakes during the bottom-up preparation process.

[0049] In some embodiments of the present invention, the conductive agent is selected from acetylene black, conductive carbon black, and graphite, but is not limited thereto. Any conductive agent commonly used in the art can be used to improve the conductivity of electrons generated in the electrode and thus improve battery performance.

[0050] In some embodiments of the present invention, the binder is selected from styrene-butadiene rubber (SBR) emulsion, carboxymethyl cellulose (CMC), polyethylene oxide (PEO), polypropylene oxide (PPO), polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP), polyacrylonitrile (PAN), polymethyl acrylate (PMA), polymethyl methacrylate (PMMA), but is not limited thereto. Commonly used negative electrode material binders in the art can be used, and PVDF is usually used.

[0051] In a fourth aspect of the present invention, a battery negative electrode is provided, comprising a current collector and the battery negative electrode material as described above.

[0052] In some embodiments of the present invention, the current collector is an inactive conductive current collector, which can be selected from copper foil (mesh), titanium foil (mesh), iron foil (mesh), nickel foil (mesh), carbon cloth, conductive nylon, etc., but is not limited thereto.

[0053] In a fifth aspect of the present invention, a battery is provided, comprising the battery negative electrode as described above.

[0054] In some embodiments of the present invention, the battery includes, but is not limited to, a half-cell such as a button cell or a full cell such as a lithium-ion battery. The negative electrode of the battery provided herein may also be an energy storage device such as a supercapacitor or a hybrid supercapacitor. The cathode active material, separator, and electrolyte of the assembled battery are not limited in any way; commonly used materials in the art can be used and are not further elaborated here. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] The present invention will be further described below with reference to the accompanying drawings and embodiments, in which:

[0056] FIG1 is a schematic diagram of the structure of a sheet-like composite aluminum material with twin metal cladding according to an embodiment of the present invention;

[0057] FIG2 is a schematic diagram of the SEM morphology of a twinned metal copper-clad composite aluminum submicron sheet material prepared in an embodiment of the present invention;

[0058] FIG3 is a schematic diagram showing the cross-sectional morphology and thickness characterization of a twinned metal copper-clad composite aluminum submicron sheet material prepared in an embodiment of the present invention;

[0059] FIG4 is a schematic diagram of TEM characterization of twins in the twinned metal copper cladding layer prepared in an embodiment of the present invention. DETAILED DESCRIPTION

[0060] The following will clearly and completely describe the concept and technical effects of the present invention in conjunction with the embodiments to fully understand the purpose, features and effects of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, other embodiments obtained by those skilled in the art without creative work are all within the scope of protection of the present invention.

[0061] In the description of the present invention, reference to terms such as "one embodiment," "some embodiments," "illustrative embodiments," "examples," "specific examples," or "some examples" means that the specific features, structures, materials, or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the exemplary expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0062] In the description of the present invention, unless otherwise indicated, the numerical range "a-b" is an abbreviation for any combination of real numbers between a and b, where a and b are real numbers. Unless otherwise indicated, the individual reactions or steps may or may not be performed sequentially. Preferably, the reaction methods of the present invention are performed sequentially.

[0063] If no specific techniques or conditions are specified in the following examples, the methods were carried out according to the techniques or conditions described in the literature in the field or according to the product instructions. All reagents or instruments without manufacturer specified are commercially available conventional products.

[0064] Example 1: Composite aluminum submicron sheet with twinned copper metal cladding layer prepared on a polyimide film substrate

[0065] This example uses a 25 μm thick polyimide film as a substrate and magnetron sputtering technology to prepare a composite aluminum submicron sheet with a twinned copper metal cladding layer. The twinned copper metal cladding layer has a thickness of 50 nm, and the corresponding aluminum metal layer has a thickness of 500 nm. The specific preparation process is as follows:

[0066] (1) Use 95% ethanol to ultrasonically clean the polyimide film, and after it is fully dried, stick it on the circular roller of the magnetron sputtering instrument. Then heat the vacuum coating chamber of the magnetron sputtering instrument to 200℃ and then pump it to a pressure of 10 -4 Pa.

[0067] (2) A carbon target with a purity of 99.99% was selected, and the deposition power was 1 kW. Argon gas at a flow rate of 300 sccm was introduced into the vacuum coating chamber to perform carbon pretreatment on the polyimide film. The coating process was as follows: a bias voltage of 50 V was applied, and deposition was performed for 5 minutes to obtain a carbon pretreated polyimide film, which was then cooled to room temperature.

[0068] (3) A copper target and an aluminum target with a purity of 99.99% were selected. The deposition power of copper was 1KW and that of aluminum was 2KW. Argon gas with a flow rate of 300sccm was introduced into the vacuum coating chamber. The vacuum coating chamber of the magnetron sputtering instrument was heated to 200°C and then evacuated to a pressure of 10 -4 The coating steps are as follows: first, a copper target is turned on under a bias voltage of 50 V to deposit on the interface-modified polyimide film for 2 minutes, then an aluminum target is turned on and kept on until the 27th minute, the copper target is turned on again and turned off after 2 minutes to obtain an aluminum metal film with a twinned copper metal coating layer deposited on the polyimide film.

[0069] (4) The polyimide film on which the composite aluminum metal film was deposited was taken out, and after being placed in a dry environment at room temperature for 48 hours, the polyimide film was gently folded and placed in anhydrous ethanol to ultrasonically peel off the composite aluminum metal film attached to the polyimide substrate. After the polyimide film was taken out, aluminum submicron sheets with a twinned copper metal coating layer were obtained and dispersed in anhydrous ethanol.

[0070] (5) The anhydrous ethanol impregnated with the aluminum composite sub-nanosheets was filtered using nylon filter paper with a pore size of 40 nm. After the filtration, the sheet was placed in a vacuum drying oven and dried for 8 hours to obtain a composite aluminum sub-micron sheet with a twinned copper metal coating.

[0071] In order to better illustrate the microscopic morphological characteristics of the composite aluminum submicron sheet with a twinned copper metal coating, a scanning electron microscope (SEM) was used to characterize it. As shown in Figure 2, the surface of the prepared composite aluminum submicron sheet is relatively smooth and presents an irregular sheet shape. The morphology of the cross section of the composite aluminum submicron sheet was further observed using a transmission electron microscope (TEM). As shown in Figure 3, the thickness of the prepared composite aluminum submicron sheet with a twinned copper metal coating was about 600nm, and the cross section showed a three-layer structure of a twinned copper metal coating layer-aluminum submicron sheet layer-twinned copper metal coating layer. In order to verify that the structure of the copper metal coating layer is twinned, the copper metal coating layer was further observed using a transmission electron microscope. As shown in Figure 4, it was proved that the crystal structure of the metallic copper in the copper metal coating layer is twinned.

[0072] To illustrate the beneficial effects of the present invention, the composite aluminum submicron sheet material with a twinned copper metal coating prepared in Example 1 was used to prepare an electrode for half-cell electrochemical performance testing. In the half-cell, a lithium metal sheet was used as the negative electrode, and an electrode prepared from the composite aluminum submicron sheet material with a twinned copper metal coating described in this example was used as the positive electrode. A polyolefin separator was used as the separator, and the electrolyte was 1M LiPF6 / EC:DMC = 1:1. The cells were assembled into button-type batteries. The specific preparation steps are as follows:

[0073] (1) Preparation of positive electrode: Aluminum submicron sheet material composited with twinned copper metal coating, carbon black and polyvinylidene fluoride (PVDF) were ground and mixed in an agate mortar in a mass ratio of 7:2:1. An appropriate amount of N-methylpyrrolidone (NMP) solvent was added and stirred until the slurry was slightly fluid. The slurry was evenly coated on the surface of the copper foil and then placed in a vacuum oven for drying at 80°C for 24 hours. The dried electrode was taken out and cut into a circular electrode with a diameter of 10 mm using a round hole punch.

[0074] (2) Negative electrode preparation: A metal lithium sheet with a diameter of 12 mm was used as the negative electrode of the half-cell.

[0075] (3) Preparation of electrolyte: In a glove box filled with argon, LiPF6 electrolyte salt was added to a mixed solvent of ethylene carbonate (EC) and dimethyl carbonate (DMC) in a volume ratio of 1:1 according to the proportion, and then stirred thoroughly to dissolve.

[0076] (4) Battery assembly and electrochemical testing: In an argon-filled glove box with H2O and O2 contents less than 0.1 ppm, button cells were assembled and electrochemical performance testing was performed in an electrochemical workstation.

[0077] In order to better illustrate the beneficial effects of the present invention, aluminum powder with a diameter of 500nm and aluminum submicron sheets with a thickness of 500nm without twin metal coating were used as negative electrode materials for comparative tests. Except for the different negative electrode materials, the other materials are exactly the same as those used in the aluminum submicron sheet negative electrode assembled half-cell with a twin copper metal coating composite in Example 1, and the preparation steps are also the same. The electrochemical performance test results are shown in Table 1. It can be found that the sheet-like aluminum submicron sheet negative electrode has smaller polarization and better discharge capacity than the granular submicron aluminum powder negative electrode, which proves that the sheet-like structural design is conducive to reducing the polarization of the submicron aluminum negative electrode and improving its electrochemical performance. However, due to the presence of the surface oxide layer, the improvement in electrochemical performance brought about by relying solely on the sheet-like structural design is relatively limited. The composite aluminum submicron sheet negative electrode coated with a twin copper metal layer further reduces polarization and greatly improves the discharge capacity, and has obvious advantages in electrochemical performance compared to the traditional aluminum powder negative electrode.

[0078] Table 1. Composite aluminum submicron sheet negative electrode half-cell test data of Example 1 of the present invention

[0079] Example 2-5: Preparation of composite aluminum submicron sheets with twinned copper metal cladding layers of different thicknesses using polyimide film as a substrate

[0080] The difference between Example 2-5 and Example 1 is the thickness of the composite aluminum submicron sheet. The preparation method of the composite aluminum submicron sheet and the assembly method of the half-cell are the same as those in Example 1. In Examples 2-5, the thickness of the aluminum metal layer is 100nm, 200nm, 300nm, and 400nm, respectively, and the thickness of the twin copper metal coating layer is 10nm, 20nm, 30nm, and 40nm, respectively. The corresponding composite aluminum submicron sheets prepared are 120nm, 240nm, 360nm, and 480nm, respectively. The composite aluminum submicron sheet with a twin copper metal coating layer prepared in Example 2-5 was prepared into an electrode for half-cell electrochemical performance testing and compared with Example 1. The test results are shown in Table 2. It can be seen that as the thickness of the aluminum metal layer decreases, the polarization voltage increases slightly with the aluminum metal layer. After 300 cycles, the discharge capacity remains above 600mAh / g.

[0081] Table 2. Composite aluminum submicron sheet negative electrode half-cell test data of Examples 1-5 of the present invention

[0082] Example 6-11: Preparation of composite aluminum submicron sheets with different types of twinned metal coatings using polyimide film as a substrate

[0083] The difference between Examples 6-11 and Example 1 lies in the type of twin metal. The preparation method of the composite aluminum submicron sheet and the half-cell assembly method are the same as those in Example 1. The types of twin metals used in Examples 6-11 are titanium, zinc, nickel, chromium, zinc-titanium alloy, and zinc-copper alloy, respectively. The thickness of the twin metal coating layer is 50 nm, and the thickness of the composite aluminum submicron sheet is 600 nm. The composite aluminum submicron sheets prepared in Examples 6-11 were prepared into electrode-assembled half-cells for electrochemical cycling testing. The test results are shown in Table 3. As shown in Table 3, the discharge capacity exceeded 500 mAh / g after 300 cycles.

[0084] Table 3. Composite aluminum submicron sheet negative electrode half-cell test data of Examples 6-11 of the present invention

[0085] Examples 12-18: Preparation of composite aluminum submicron sheets with twinned copper metal cladding using different polymer films as substrates

[0086] Examples 12-18 differ from Example 1 in that the composite aluminum submicron flakes are prepared using different polymer film substrates; the remaining preparation steps remain the same. The choice of substrate affects the diameter of the composite aluminum submicron flakes. The diameters of the composite aluminum submicron flakes with twinned copper metal cladding layers prepared in Examples 12-18 and Example 1 were measured using a laser particle size analyzer. The results, shown in Table 4, indicate that the resulting composite aluminum submicron flakes all had diameters in the micrometer range, all below 100 μm.

[0087] Table 4. Diameter test results of composite aluminum submicron sheets prepared in Examples 12-18 and Example 1 of the present invention

[0088] Examples 19-23: Lithium-ion full battery assembly based on twinned copper metal coating composite aluminum submicron sheet negative electrode material and lithium cobalt oxide positive electrode material

[0089] Examples 19-23 respectively utilize the twinned copper metal cladding composite aluminum submicron sheet materials prepared in Examples 1-5 of the present invention to assemble lithium-ion full batteries, wherein the positive electrode utilizes lithium cobalt oxide, the separator utilizes a polyolefin separator, and the electrolyte utilizes 1M LiPF6 / EC:DMC in a 1:1 ratio, to form button-type batteries. The specific preparation steps are as follows:

[0090] (1) Preparation of negative electrode material: The twinned copper metal cladding composite aluminum submicron sheet material prepared in Examples 1-5, conductive carbon black, and polyvinylidene fluoride (PVDF) were ground and mixed uniformly in an agate mortar at a mass ratio of 7:2:1. An appropriate amount of N-methylpyrrolidone (NMP) solvent was added and stirred thoroughly until the slurry became slightly fluid. The slurry was then coated on the surface of the copper foil and dried in a vacuum oven at 80°C for 24 hours. The dried negative electrode was removed and cut into circular pieces with a diameter of 12 mm using a round hole punch.

[0091] (2) Preparation of positive electrode materials: Lithium cobalt oxide positive electrode material, conductive carbon black, and polyvinylidene fluoride (PVDF) were ground and mixed uniformly in an agate mortar at a mass ratio of 8:1:1. An appropriate amount of N-methylpyrrolidone (NMP) solvent was added and stirred thoroughly until the slurry became slightly fluid. The slurry was then evenly coated on the surface of carbon-coated aluminum foil and then dried in a vacuum oven at 80°C for 24 hours. The dried positive electrode sheet was removed and cut into a circular sheet with a diameter of 10 mm using a round hole punch.

[0092] (3) Preparation of electrolyte: In a glove box filled with argon, LiPF6 electrolyte salt was added to a mixed solvent of ethylene carbonate (EC) and dimethyl carbonate (DMC) in a volume ratio of 1:1 according to the proportion, and then stirred thoroughly to dissolve.

[0093] (4) Battery assembly and electrochemical testing: In an argon-filled glove box with H2O and O2 contents less than 0.1 ppm, button cells were assembled and electrochemical performance testing was performed in an electrochemical workstation.

[0094] The composite aluminum submicron sheet negative electrode material with a twinned copper metal coating layer prepared in Examples 1-5 was used in combination with a lithium cobalt oxide positive electrode material to assemble a lithium-ion full battery. The electrochemical performance of the full battery corresponding to the composite aluminum submicron sheet negative electrode materials of different thicknesses was compared. The test results are shown in Table 5. As can be seen from the table, the reversible discharge specific capacity is around 130 mAh / g, and the capacity retention rate is maintained above 95% after 500 cycles of the full battery.

[0095] Table 5. Test data of lithium-ion full batteries based on lithium cobalt oxide positive electrode materials of Examples 19-23 of the present invention

[0096] Examples 24-28: Dual-ion battery assembly based on twinned copper metal coating composite aluminum submicron sheet material and expanded graphite positive electrode material

[0097] Examples 24-28 respectively utilize the twinned copper metal-clad aluminum submicron sheet materials prepared in Examples 1-5 of the present invention to assemble lithium-ion dual-ion batteries. Expanded graphite serves as the positive electrode material for these dual-ion batteries, a polyolefin separator is used, and the electrolyte is 4M LiPF6 / EMC + 2% VC. The batteries are assembled into button-type cells. The specific preparation steps are as follows:

[0098] (1) Preparation of negative electrode material: The twinned copper metal cladding composite aluminum submicron sheet material prepared in Examples 1-5, conductive carbon black, and polyvinylidene fluoride (PVDF) were ground and mixed uniformly in an agate mortar at a mass ratio of 7:2:1. An appropriate amount of N-methylpyrrolidone (NMP) solvent was added and stirred thoroughly until the slurry became slightly fluid. The slurry was then coated on the surface of the copper foil and dried in a vacuum oven at 80°C for 24 hours. The dried negative electrode was removed and cut into circular pieces with a diameter of 12 mm using a round hole punch.

[0099] (2) Preparation of positive electrode materials: Expanded graphite, conductive carbon black, and polyvinylidene fluoride (PVDF) were ground and mixed uniformly in an agate mortar at a mass ratio of 8:1:1. An appropriate amount of N-methylpyrrolidone (NMP) solvent was added and stirred thoroughly until the slurry became slightly fluid. The slurry was then evenly coated on the surface of carbon-coated aluminum foil and then dried in a vacuum oven at 80°C for 24 hours. The dried positive electrode was removed and cut into circular pieces with a diameter of 10 mm using a round hole punch.

[0100] (3) Preparation of electrolyte: In a glove box filled with argon, LiPF6 electrolyte salt was added to ethyl methyl carbonate (EMC) solvent in proportion, and then 2% by mass of vinylene carbonate (VC) additive was added, and then stirred thoroughly to dissolve.

[0101] (4) Assembly and electrochemical testing of dual-ion batteries: In an argon-filled glove box with H2O and O2 contents less than 0.1 ppm, the batteries were assembled into button cells and electrochemical performance tests were performed in an electrochemical workstation.

[0102] Examples 24-28 respectively use the composite aluminum submicron sheet negative electrode material with a twin copper metal coating layer prepared in Examples 1-5 and expanded graphite as the positive electrode material to assemble lithium-ion-based dual-ion full batteries. The electrochemical performance of the lithium-ion-based dual-ion full batteries corresponding to the composite aluminum submicron sheet negative electrode materials of different thicknesses is compared. The test results are shown in Table 6. It can be seen from the table that their reversible discharge specific capacities are all around 100 mAh / g. After the dual-ion batteries are cycled 1000 times, the capacity retention rate is maintained at above 80%.

[0103] Table 6. Test data of dual-ion batteries based on expanded graphite positive electrode materials of Examples 24-28 of the present invention

[0104] Compared with Examples 19-23, although the battery capacity of Examples 24-28 is limited by the capacity of the dual-ion battery positive electrode material, it decreases to a certain extent. However, compared with the expensive lithium cobalt oxide positive electrode material in Examples 19-23, Examples 24-28 use dual-ion batteries with economical and friendly expanded graphite as the positive electrode, which significantly reduces the cost. At the same time, the reversible discharge specific capacity of the battery is about 100 mAh / g. After the dual-ion battery is cycled for 1000 times, the capacity retention rate is maintained at more than 80%, which reduces the cost while meeting the basic requirements of the full battery.

[0105] The above-described embodiments merely illustrate several implementations of the present invention. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, and all such variations and improvements fall within the scope of protection of the present invention.

Claims

1. A composite aluminum material, characterized in that, it comprises aluminum sheets and twin crystal metal materials; the twin crystal metal materials are coated on the upper and lower surfaces of the aluminum sheets to form an upper layer twin crystal metal coating layer and a lower layer twin crystal metal coating layer.

2. The composite aluminum material according to claim 1, characterized in that, the thickness of the aluminum sheet is 1 nm to 100 μm, preferably 100 nm to 500 nm; and / or, the diameter of the aluminum sheet is 1 μm to 200 μm, preferably 10 μm to 100 μm; and / or, the thickness of the upper layer twin crystal metal coating layer is 1 nm to 300 nm, preferably 1 nm to 50 nm; and / or, the thickness of the lower layer twin crystal metal coating layer is 1 nm to 300 nm, preferably 1 nm to 50 nm.

3. The composite aluminum material according to claim 1, characterized in that, the twin crystal metal material is selected from single element materials composed of elements in the first to seventh subgroups, the eighth group, the third main group, and the fourth main group of the periodic table, or alloys or composite materials composed of multiple elements; preferably metal titanium, metal zinc, metal nickel, metal chromium, zinc-titanium alloy, zinc-copper alloy.

4. A preparation method of the composite aluminum material according to any one of claims 1-3, characterized in that, it comprises the steps of: providing a polymer film substrate and cleaning the polymer film substrate; performing a pre-treatment for carbon plating on the cleaned polymer film substrate to obtain a carbon-plated polymer film substrate; using physical vapor deposition technology to sequentially deposit a lower layer twin crystal metal film layer, an aluminum metal film layer, and an upper layer twin crystal metal film layer on the surface of the carbon-plated polymer film substrate to form a composite aluminum metal film with a sandwich structure; after the carbon-plated polymer film substrate deposited with the composite aluminum metal film is subjected to a standing treatment, it is placed in an organic solvent for ultrasonic treatment to peel off the carbon-plated polymer film, and then the organic solvent is removed to obtain the composite aluminum material.

5. The preparation method of the composite aluminum material according to claim 4, characterized in that, the polymer film substrate includes polyimide film, carbonate film, polyethylene terephthalate film, polypropylene film, polyethylene film, polyvinyl chloride film, polytetrafluoroethylene film, polystyrene film, polyvinylidene fluoride; and / or, the thickness of the polymer film substrate is 3 μm to 100 μm, preferably 10 μm to 25 μm.

6. The preparation method of the composite aluminum material according to claim 4, characterized in that, the pre-treatment for carbon plating includes plating an amorphous carbon layer on the surface layer of the polymer film substrate, and the thickness of the amorphous carbon layer is 1 nm to 50 nm, preferably 10 nm to 20 nm; and / or, the standing treatment includes placing it at a temperature of -40 °C to 35 °C for 1 h to 48 h.

7. The preparation method of the composite aluminum material according to claim 4, characterized in that, the physical vapor deposition technology includes vacuum evaporation coating technology, vacuum magnetron sputtering technology, and ion coating technology.

8. A battery anode material, characterized in that, It includes a negative electrode active material, a conductive agent, and a binder. The negative electrode active material is the composite aluminum material described in any one of claims 1-3 or the composite aluminum material prepared by using the preparation method described in any one of claims 4-7.

9. A battery negative electrode characterized in that it includes a current collector and the battery negative electrode material as described in claim 8.

10. A battery characterized in that it includes the battery negative electrode as described in claim 9.

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