Preparation method of composite current collector

Abstract

The invention relates to the technical field of sodium metal batteries, in particular to a preparation method of a composite current collector for a lightweight high-energy-density sodium metal battery. The composite current collector comprises a polymer middle layer and conducting layers on the two sides of the polymer middle layer. The conductive layer with the thickness of 200-500 nanometers is attached to the surface of the polymer middle layer through a magnetron sputtering method, it is guaranteed that the conductive layer on the surface is uniform and does not fall off, and meanwhile light weight and good flexibility of the current collector are achieved through the light and flexible polymer middle layer. The nano-particles on the surface of the conducting layer subjected to magnetron sputtering are also beneficial to uniform deposition of sodium metal on the surface of the current collector, and the electrochemical performance of the traditional commercial copper foil / aluminum foil is achieved or surpassed on the basis of light weight. The preparation method of the composite current collector provided by the invention is simple and convenient in process and relatively low in cost, and is favorable for realizing a light-weight and high-energy-density sodium metal battery.

Description

Technical Field

[0001] The present application relates to a method for preparing a composite current collector, and in particular, to a method for preparing a composite current collector for use in a sodium metal battery. Background Art

[0002] In recent years, with the huge demand for renewable energy and increasingly severe environmental pollution problems, there is an urgent need to develop efficient and convenient large-scale energy storage technology. Sodium metal batteries have attracted research interest due to their high theoretical specific capacity and high energy density, but the high reactivity of sodium itself causes it to react continuously with the electrolyte and generate dendrites, resulting in low coulombic efficiency and safety issues for sodium metal batteries. Therefore, the development of dendrite-free, high coulombic efficiency sodium metal batteries is still a challenge for their large-scale application.

[0003] The current collector is an important component of the sodium metal battery, which carries active materials and connects the internal and external electron pathways. Commonly used current collectors are generally commercial copper foil and aluminum foil, which occupy a large part of the volume and mass of the battery, greatly affecting the energy density of the metal battery. Using polymer as a substrate and metal plating on the surface by magnetron sputtering to form a composite current collector can greatly reduce the amount of copper and aluminum in the battery. It not only reduces the mass occupied by the current collector in the battery and improves the energy density of the battery, but also reduces the overall mass of the battery, saving manufacturing and transportation costs to a great extent.

[0004] Therefore, a composite current collector is proposed for lightweight and high energy density sodium metal batteries. Summary of the invention

[0005] In order to reduce the weight of the sodium metal battery collector and achieve lightweight and high energy density of the sodium metal battery, the present application proposes a method for preparing a composite current collector, which can not only reduce the weight of the battery collector and effectively improve the battery energy density, but also reduce the production cost of the composite current collector.

[0006] In order to solve the above problems, the present application provides a method for preparing a composite current collector, comprising the following steps:

[0007] Providing a polymeric interlayer cut to size, the polymeric interlayer having respective two sides:

[0008] Conductive layers are respectively arranged on both sides of the polymer intermediate layer, with the polymer intermediate layer as a substrate, and the conductive layers are formed by magnetron sputtering on both sides of the polymer intermediate layer:

[0009] The polymer intermediate layer is polyethylene terephthalate (PET), and the conductive layer is made of at least one of copper and aluminum;

[0010] The thickness of the polymer intermediate layer is 12.5 micrometers, and the thickness of the conductive layer is 200-500 nanometers;

[0011] 1. The present application provides a method for preparing a composite current collector, the composite current collector comprising a polymer intermediate layer and conductive layers on both sides. The conductive layers on both sides are deposited on the surface of the polymer intermediate layer by magnetron sputtering, and the sputtering thickness is 200-500 nanometers. The composite current collector prepared by this method can be used as a current collector for sodium metal batteries. Compared with traditional commercial copper foil / aluminum foil, the composite current collector is lightweight.

[0012] 2. The material of the polymer intermediate layer in the embodiment of the present application is polyethylene terephthalate (PET). By selecting a lightweight and bendable polymer intermediate layer as the substrate of the composite current collector, the composite current collector has good flexibility;

[0013] 3. The conductive layer of the embodiment of the present application is made of at least one of copper or aluminum, and a 200-500 nanometer conductive layer is deposited on both sides of the polymer intermediate layer by magnetron sputtering. The magnetron sputtering method can make copper / aluminum nanoparticles evenly adhere to the surface of the polymer intermediate layer, ensuring that the surface conductive layer is uniform and stable without falling off. The tiny particles on the surface of the conductive layer are also conducive to the uniform deposition of sodium metal, reaching or exceeding the coulomb efficiency of traditional commercial copper foil / aluminum foil;

[0014] 4. In the embodiment of the present application, conductive layers are provided on both sides of the polymer intermediate layer. The conductivity of the conductive layers is somewhat lower than that of traditional commercial copper foil / aluminum foil, but the performance of the composite current collector in the battery is better than that of traditional commercial copper foil / aluminum foil.

[0015] The preparation method of the composite current collector of the present application can form a nanometer-thick conductive layer on both sides of the polyethylene terephthalate (PET) film by magnetron sputtering. The conductive layer has excellent electrochemical stability, does not react with the electrolyte, and exhibits excellent electrochemical performance. The preparation process of the present application is simple, and the current collector is lightweight, which can effectively improve production efficiency, reduce production costs, and reduce comprehensive costs while increasing battery energy density. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 An SEM image of the copper side of the Xiahe fluid surface was prepared for this application.

[0017] Figure 2 The SEM image of the aluminum side of the composite current collector surface prepared for this application.

[0018] Figure 3 This is a SEM image of the surface of the polymer interlayer (PET) used in this application.

[0019] Figure 4The quality of the composite current collector prepared for this application is compared with that of traditional commercial copper foil / aluminum foil.

[0020] Figure 5 The conductivity of the composite current collector prepared for this application is compared with that of traditional commercial copper foil / aluminum foil.

[0021] Figure 6 This is the Na-Al half-cell cycle efficiency diagram for traditional aluminum foil.

[0022] Figure 7 This is the cycle efficiency diagram of the Na-Cu half-cell made of traditional foil.

[0023] Figure 8 A half-cell cycle efficiency diagram of a composite current collector Na-500nm Al was prepared for this application.

[0024] Fig. 9 A half-cell cycle efficiency diagram of a composite current collector Na-500nm Cu was prepared for this application. DETAILED DESCRIPTION

[0025] Unless otherwise defined, the technical terms used in the following examples have the same meanings as those generally understood by those skilled in the art to which the present invention belongs. The test reagents used in the following examples are conventional biochemical reagents unless otherwise specified; the experimental methods are conventional methods unless otherwise specified.

[0026] The invention will be described in detail below with reference to the embodiments and the accompanying drawings.

[0027] The models and manufacturers of the equipment used in the embodiments of the present invention are as follows:

[0028] Electronic balance, model BT224S, Sartorius, Germany; triple / dual target magnetron sputtering instrument, model VTC-600-3HD / 2HD, Shenyang Kejing Automation Equipment Co., Ltd.; punching machine, model MRXCP60, Shenzhen Kejing Co., Ltd.; glove box, model EXCEL, Ai Mingke Technology Co., Ltd.; button battery sealing machine, model MSK-110, Shenzhen Kejing Co., Ltd.; LAND battery tester, model LAND CT2001A, Wuhan Landian Electronics Co., Ltd.; scanning electron microscope, model Hitachi S4800, Hitachi Corporation, Japan.

[0029] The raw material information used in each embodiment of the present invention is as follows:

[0030] Polyethylene terephthalate (PET) film, specification of 12.5um, purchased from Shanghai Huadong Composite Insulation Filter Cloth Screen Factory; copper target, specification of 99.99%, purchased from Quanzhou Qijin New Material Technology Co., Ltd.; carbon target, specification of 99.99%, purchased from Quanzhou Qijin New Material Technology Co., Ltd.; sodium metal specification of battery grade purchased from Tianjin Zhongneng Lithium Industry Co., Ltd.; high purity argon (Ar 2 ), with a specification of 99.99%, purchased from Tianjin Huanyu Gas Co., Ltd.; glass fiber separator, with a specification of battery grade, purchased from Cytiva, USA; battery shell, with a specification of CR2032, purchased from McLean Co., Ltd.; NaClO 4 in EC / DEC (1:1, w / w), specification: 1 mol L -1 Battery grade, purchased from Suzhou Duoduo Chemical Technology Co., Ltd.;

[0031] Example 1

[0032] A method for preparing a composite current collector surface comprises the following steps:

[0033] (1) Cutting a polyethylene terephthalate (PET) film into a disc with a diameter of 16 mm, the thickness of the PET film is 12.5 μm;

[0034] (2) using a magnetron sputtering process to plate a copper or aluminum conductive layer on the surface of the polymer intermediate layer, wherein the thickness of the conductive layer is 200-500 nm;

[0035] The embodiments of the present application provide corresponding characterizations of the composite current collector. Figure 1 The SEM image of the copper side of the composite current collector surface prepared for this application is as follows: Figure 2 The SEM image of the aluminum side of the composite current collector surface prepared for this application is as follows: Figure 3 The SEM image of the surface of the polymer interlayer (PET) used in this application. Magnetron sputtering obtains a uniform and firm conductive layer, and the nanoparticles on the surface are conducive to guiding the uniform deposition of sodium metal.

[0036] In this embodiment, the composite current collector prepared in the present application includes a polymer interlayer and conductive layers on both sides, and the thickness of the conductive layer is 500nm. Figure 4 As shown, the mass of the composite current collector with an aluminum conductive layer is 0.00396 g, and the mass of the aluminum foil is 0.00845 g. The mass of the composite current collector is only 46.86% of that of the traditional commercial aluminum foil. The mass of the composite current collector with a copper conductive layer is 0.00473 g, and the mass of the copper foil is 0.01768 g. The mass of the composite current collector is only 26.75% of that of the traditional commercial copper foil. This shows that the composite current collector of this embodiment can achieve lightweight current collectors and greatly improve the energy density of sodium metal batteries.

[0037] In this embodiment, the composite current collector prepared in the present application includes a polymer middle layer and conductive layers on both sides, and the thickness of the conductive layer is 500nm. The conductive layers on both sides of the polymer middle layer can connect the electronic paths inside and outside the battery, such as Figure 5 As shown, compared with the conductivity of traditional copper foil / aluminum foil, there is a certain gap in the composite current collector with a conductive layer of 500nm. In other embodiments, its conductivity increases with the increase of the thickness of the conductive layer.

[0038] Example 2

[0039] The electrode materials prepared in the above steps were assembled into a half-cell for electrochemical performance testing; the electrode sheet and a 12 mm-sized sodium metal sheet were assembled into a CR2032 button cell in a glove box filled with argon atmosphere and with water and oxygen content less than 0.1 ppm, and sealed with a button cell sealer. The electrolyte system was 1 mol L- 1 NaClO containing additives of ethylene carbonate (EC) / diethyl carbonate (DEC) (1:1, volume ratio) 4 The solution is prepared by using a commercial glass fiber diaphragm.

[0040] Figure 6 This is a cycle efficiency diagram of the sodium metal half-cell in Example 2. The Na-Al half-cell shows that after 30 cycles, the coulombic efficiency is about 90%.

[0041] Figure 7 This is the cycle efficiency diagram of the aluminum metal half-cell in Example 2. The Na-Cu half-cell shows that after 30 cycles, the coulombic efficiency is maintained at about 70%, which is relatively low.

[0042] Figure 8 Graph showing the cycle efficiency of the sodium metal half-cell in Example 2. The Na-PET / 500nm Al half-cell shows that after 30 cycles, the coulombic efficiency continues to rise and reaches 90%, which is close to that of Al foil.

[0043] Fig. 9 The graph is the cycle efficiency of the sodium metal half-cell in Example 2. The Na-PET 500nm Cu half-cell shows that after 30 cycles, the coulombic efficiency is stabilized at 90%, which is significantly improved compared to the coulombic efficiency of Cu foil.

[0044] All technical and scientific terms used in this application have the same meanings as those commonly understood by technicians in the technical field to which this application belongs; the terms used in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0045] The present application is not limited to the above embodiments. Improvements and modifications made by those skilled in the art based on the disclosure of the present application and without departing from the scope of the present application should be within the protection scope of the present application.

Claims

1. A method for preparing a composite current collector for use in sodium metal batteries, characterized in that: The steps include: providing a polymeric intermediate layer cut to a suitable size, the polymeric intermediate layer having corresponding two sides; Conductive layers are respectively arranged on both sides of the polymer intermediate layer, and the conductive layers are formed by magnetron sputtering on both sides of the polymer intermediate layer.

2. The method for preparing a composite current collector according to claim 1, characterized in that: The polymer intermediate layer is polyethylene terephthalate (PFT), and the material of the conductive layer includes at least one of copper and aluminum.

3. The method for preparing a composite current collector according to claim 1, characterized in that: The thickness of the polymer intermediate layer is 12.5 micrometers, and the thickness of the conductive layer is 200-500 nanometers.

4. Use of the composite current collector prepared according to the preparation method according to any one of claims 1 to 3 in a sodium metal battery.

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