Preparation method of nanocarbon modified composite current collector surface

Abstract

The invention discloses a preparation method of a nanocarbon modified composite current collector surface, which comprises the following steps: (1) cutting a polyethylene terephthalate (PET) film with the size of 8 * 8cm; (2) the inspection device is accurate; (3) mounting a target material; (4) fixing the PET film on a sample table, setting 30sccm of argon, and starting a power supply of a water cooler; (5) the cavity is vacuumized, and the vacuum degree is reduced to 4E + 0hPa; (6) opening the molecular pump to enable the rotating speed to reach 90000, opening the percentage of the rotating speed of the molecular pump to enable the rotating speed to be reduced to 45000, and opening the flowmeter 1 and the rotary table; (7) a direct-current power switch is turned on, the power is adjusted to be 30 W, a baffle is opened, and the thickness of sputtered metal is 500 nm; and (8) the composite current collector obtained in the step (7) is placed on a sample table, the steps (4-7) are repeated, and the thickness of the sputtered nanocarbon is 10 nm. The preparation method of the surface of the nanocarbon modified composite current collector is simple, low in price and environment-friendly, the obtained nanocarbon modified composite current collector can be applied to a sodium metal battery negative electrode, the mass of a battery can be greatly reduced, the safety performance of the battery can be improved, and excellent cycling stability can be provided.

Description

Technical Field

[0001] The invention discloses a method for preparing a surface of a nano-carbon modified composite current collector, and more specifically, relates to a method for preparing a negative electrode material for a sodium metal battery. Background Art

[0002] In recent decades, sodium metal batteries (SMBs) have attracted increasing attention as a low-cost, high-energy-density secondary battery. However, chemically active metallic sodium (Na) can continuously react with organic electrolytes, resulting in low Coulombic efficiency, fast capacity decay, and large interfacial resistance of SMBs. Meanwhile, uneven Na deposition can trigger the malignant growth of Na dendrites, leading to serious safety hazards. Therefore, constructing a stable and dendrite-free Na metal anode is crucial to improve the electrochemical stability and safety of SMBs.

[0003] Metal foil is the carrier and current collector of the positive and negative electrode materials of sodium batteries. Based on the demand for improving the mass energy density / volume energy density of sodium batteries, the mass proportion / volume proportion of current collectors in sodium batteries should be as low as possible. Therefore, current collectors are developing in the direction of thinner, microporous, high tensile strength, high elongation and composite, and the application of polymer-plated metal composite current collectors to replace traditional pure metal current collectors is gradually maturing. Low-cost, high-quality composite current collectors have positive significance for the development of power batteries.

[0004] The surface of metal foil is relatively smooth and flat, and the contact area is not large enough. In addition, metal foil is a metal material, while batteries are generally non-metallic materials, which makes the two materials have poor contact compatibility and large interface contact resistance, resulting in reduced battery charge and discharge performance. Therefore, surface modification of metal foil composite current collectors has become one of the effective methods to improve the performance of sodium metal batteries.

[0005] Since nanocarbon materials have strong plasticity, wide sources, light texture, and can stably coexist with sodium metal, we use nanocarbon materials to modify the surface of the composite current collector to provide more active sites for the embedding of sodium and improve the performance of sodium metal batteries. Summary of the invention

[0006] The present invention aims to solve the safety problem of the negative electrode of the sodium metal battery, so that the sodium metal battery can be truly commercialized.

[0007] To achieve the above purpose, the present invention adopts the following technical solutions:

[0008] A method for preparing a composite current collector comprises the following steps:

[0009] (1) Cutting polyethylene terephthalate (PET) film. The inner layer of the composite current collector is a polymer high molecular PET film, and the cutting size is 8*8 cm;

[0010] (2) Check that the DC / RF power supply, vacuum pump unit, ventilation system, cooling system, and film thickness meter are connected correctly;

[0011] (3) Install the target: loosen the top screw, remove the target baffle, rotate counterclockwise to remove the target cover, unscrew the screws, remove the target pressure plate, and install or replace the target. Finally, install the components in reverse order;

[0012] (4) Fix the PET film on the sample stage, fix the four corners with tape, open the argon gas cylinder, set the gas flow rate to 30 sccm, and turn on the chiller power;

[0013] (5) Evacuate the chamber: Close the upper cover, lock the knob, open the manual baffle valve, turn on the power switch, and reduce the vacuum degree to 4E+0hPa;

[0014] (6) Turn on the molecular pump and make the molecular pump speed reach 90000, turn on the molecular pump speed percentage and reduce the speed to 45000, turn on the flow meter 1 and the turntable;

[0015] (7) Turn on the DC power switch, adjust the power to 30 W, open the baffle, start sputtering, and the sputtered metal thickness is 500 nm;

[0016] A method for preparing a nano-carbon modified composite current collector surface comprises the following steps:

[0017] Place the composite current collector obtained in step (7) above on the sample stage, and repeat steps (4), (5), (7) until the sputtered nanocarbon thickness is 10 nm;

[0018] 1) The preparation method of the nano-carbon modified composite current collector surface described in the present invention has a simple process, conforms to the concept of sustainable development, is low in cost, and is non-toxic and harmless;

[0019] 2) The present invention provides nucleation sites for the deposition of sodium metal by modifying the surface of the composite current collector with nanocarbon;

[0020] 3) The nano-carbon modified composite current collector material prepared by the present invention is simple and easy to obtain, has abundant raw materials, and has controllable production conditions. It can greatly inhibit the growth of sodium dendrites and a series of problems such as unlimited volume expansion, and is a developable negative electrode material for sodium metal batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a quality diagram of the inner layer PET film used in Example 1.

[0022] Figure 2 The quality diagram of the composite current collector prepared in Example 1

[0023] Figure 3 The quality diagram of the nanocarbon modified composite current collector prepared in Example 1

[0024] Figure 4 The quality diagram of the copper foil used as a comparison group in Example 1

[0025] Figure 5 The quality diagram of the aluminum foil used as a comparison group in Example 1

[0026] Figure 6 This is a SEM image of the copper side of the composite current collector in Example 1.

[0027] Figure 7 This is a SEM image of the carbon side of the surface of the nanocarbon-modified composite current collector in Example 1.

[0028] Figure 8 This is the SEM image of the PET film in Example 1.

[0029] Fig. 9 This is the cycle efficiency diagram of the Na / Cu half-cell in Example 2.

[0030] Fig.10 This is the cycle efficiency diagram of the Na / PET-500nm Cu half-cell in Example 2.

[0031] Fig.11 This is the cycle efficiency diagram of the Na / PET-500nm Cu-10nm C half-cell in Example 2. DETAILED DESCRIPTION

[0032] 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 all conventional biochemical reagents unless otherwise specified; the experimental methods are all conventional methods unless otherwise specified.

[0033] The invention will be described in detail below with reference to the embodiments and the accompanying drawings.

[0034] The models and manufacturers of the equipment used in the embodiments of the present invention are as follows:

[0035] 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.

[0036] The raw material information used in each embodiment of the present invention is as follows:

[0037] Polyethylene terephthalate (PET) film, specification is 12.5um, purchased from Shanghai Huadong Composite Insulation Filter Cloth Screen Factory; copper target, specification is 99.99%, purchased from Quanzhou Qijin New Material Technology Co., Ltd.; carbon target, specification is 99.99%, purchased from Quanzhou Qijin New Material Technology Co., Ltd.; metallic sodium, specification is battery grade, purchased from Tianjin Zhongneng Lithium Co., Ltd.; high purity argon (Ar2), specification is 99.99%, purchased from Tianjin Huanyu Gas Co., Ltd.; glass fiber diaphragm, specification is battery grade, purchased from Cytiva, USA; battery shell, specification is CR2032, purchased from McLean Co., Ltd.; NaClO4in EC / DEC (1:1, w / w), specification is 1 mol L -1 Battery grade, purchased from Suzhou Duoduo Chemical Technology Co., Ltd.;

[0038] Example 1

[0039] A method for preparing a nano-carbon modified composite current collector surface comprises the following steps:

[0040] (1) Cutting polyethylene terephthalate (PET) film. The inner layer of the composite current collector is a polymer high molecular PET film, and the cutting size is 8*8 cm;

[0041] (2) Check that the DC / RF power supply, vacuum pump unit, ventilation system, cooling system, and film thickness meter are connected correctly;

[0042] (3) Install the target: loosen the top screw, remove the target baffle, rotate counterclockwise to remove the target cover, unscrew the screws, remove the target pressure plate, and install or replace the target. Finally, install the components in reverse order;

[0043] (4) Fix the PET film on the sample stage, fix the four corners with tape, open the argon gas cylinder, set the gas flow rate to 30 sccm, and turn on the chiller power;

[0044] (5) Evacuate the chamber: Close the upper cover, lock the knob, open the manual baffle valve, turn on the power switch, and reduce the vacuum degree to 4E+0hPa;

[0045] (6) Turn on the molecular pump and make the molecular pump speed reach 90000, turn on the molecular pump speed percentage and reduce the speed to 45000, turn on the flow meter 1 and the turntable;

[0046] (7) Turn on the DC power switch, adjust the power to 30 W, open the baffle, start sputtering, and the sputtered metal thickness is 500 nm;

[0047] A method for preparing a nano-carbon modified composite current collector surface comprises the following steps:

[0048] Place the composite current collector obtained in step (7) above on the sample stage, and repeat steps (4), (5), (7) until the sputtered nanocarbon thickness is 10 nm;

[0049] The electrode materials prepared by the above method were subjected to various tests, and the test results are shown in Figure 1 , Figure 2 , Figure 3 , Figure 4 , Figure 5 , Figure 6 , Figure 7 , Figure 8 .

[0050] Figure 1 The mass of the inner PET film used in Example 1 is 3.37 mg. Figure 2 is the mass of the composite current collector prepared in Example 1, which is 4.73 mg. Figure 3 The mass of the nano-carbon modified composite current collector prepared in Example 1 is 4.85 mg. Figure 4 and Figure 5 As the control group, the weight of copper foil and aluminum foil of the same size are 17.68 mg and 8.45 mg respectively. As can be seen from the mass diagram, the weight of the prepared composite current collector is significantly reduced compared with the traditional current collectors of copper foil and aluminum foil, which is convenient for preparing lighter and safer batteries. Although the weight of the composite current collector modified by nanocarbon has increased by 0.12 mg, the increase is small. Combined with the subsequent battery performance test, it shows the feasibility and innovation of the preparation method of the surface of the nanocarbon-modified composite current collector.

[0051] Figure 6 This is a SEM image of the copper side of the composite current collector obtained in Example 1. In the image, the metallic copper is in the form of nanoclusters, but has poor size uniformity and poor smoothness. Figure 7This is a SEM image of the carbon side of the surface of the nanocarbon-modified composite current collector obtained in Example 1. After modification with nanocarbon, the uniformity is greatly improved, and the surface is smooth, which is conducive to the deposition and stripping of sodium, and improves the electrochemical performance of the sodium metal battery. Figure 8 This is the SEM image of the PET film in Example 1.

[0052] Example 2

[0053] The electrode materials prepared in the above steps were assembled into a half-cell for electrochemical performance testing; the material was punched into small discs with a diameter of 16 mm using a punching machine, and assembled with a 12 mm metal sodium sheet into a CR2032 button cell in a glove box filled with argon atmosphere and with a water and oxygen content of less than 0.1 ppm, and sealed with a button cell sealing machine. The electrolyte system was 1 mol L -1 The additive contained in the NaClO4 solution was ethylene carbonate (EC) / diethyl carbonate (DEC) (1:1, volume ratio), and the diaphragm was a commercial glass fiber diaphragm.

[0054] Fig. 9 2 is a cycle efficiency diagram of the sodium metal half-cell in Example 2. The Na / Cu half-cell shows that the coulombic efficiency is maintained at 75% only after 50 cycles, and the stability is poor.

[0055] Fig.10 This is a cycle efficiency diagram of the sodium metal half-cell in Example 2. The Na / PET-500nm Cu half-cell shows that the coulombic efficiency is maintained at 90% after 50 cycles. The stability is improved compared to copper foil, but the coulombic efficiency is still low.

[0056] Fig.11 This is the cycle efficiency diagram of the sodium metal half-cell in Example 2. The Na / PET-500nm Cu-10nm C half-cell shows that after 50 cycles, the coulombic efficiency reaches 95%, the stability is greatly improved, and the coulombic efficiency is relatively high.

[0057] The present invention simplifies the preparation process of negative electrode materials for sodium metal batteries. On this basis, a nano-carbon-modified composite current collector surface structure is designed for the negative electrode of sodium metal batteries. The material has high cycle efficiency and is simple and environmentally friendly. It is considered to be a very potential sodium metal battery electrode material.

[0058] The above description is only a preferred example of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a nanocarbon-modified composite current collector surface, characterized in that: The specific steps include: (1) Cutting polyethylene terephthalate (PET) film. The inner layer of the composite current collector is a polymer high molecular PET film, and the cutting size is 8*8 cm; (2) Check that the DC / RF power supply, vacuum pump unit, ventilation system, cooling system, and film thickness meter are connected correctly; (3) Install the target: loosen the top screw, remove the target baffle, rotate counterclockwise to remove the target cover, unscrew the screws, remove the target pressure plate, and install or replace the target. Finally, install the components in reverse order; (4) Fix the PET film on the sample stage, fix the four corners with tape, open the argon gas cylinder, set the gas flow rate to 30 sccm, and turn on the chiller power; (5) Evacuate the chamber: Close the upper cover, lock the knob, open the manual baffle valve, turn on the power switch, and reduce the vacuum degree to 4E+0hPa; (6) Turn on the molecular pump and make the molecular pump speed reach 90000, turn on the molecular pump speed percentage and reduce the speed to 45000, turn on the flow meter 1 and the turntable; (7) Turn on the DC power switch, adjust the power to 30 W, open the baffle, start sputtering, and the sputtered metal thickness is 500 nm; (8) Place the composite current collector obtained in step (7) above on the sample stage, and repeat steps (4), (5), and (7) to sputter nanocarbon to a thickness of 10 nm.

2. The method for preparing a nanocarbon-modified composite current collector surface according to claim 1, characterized in that: The intermediate in step (1) is a PET film with a thickness of 12.5 um.

3. The method for preparing a nanocarbon-modified composite current collector surface according to claim 1, characterized in that: The composite current collector prepared in step (7) has metal copper on both sides, and the thickness of each side is 500 nm.

4. The method for preparing a nanocarbon-modified composite current collector surface according to claim 1, characterized in that: In the step (8), the nanocarbon-modified composite current collector surface has a sputtered nanocarbon thickness of 10 nm.

5. A negative electrode material having a nano-carbon-modified composite current collector surface prepared according to the preparation method according to any one of claims 1 to 4.

6. Application of the nanocarbon-modified composite current collector surface obtained by the preparation method according to any one of claims 1 to 4 in sodium metal batteries.

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