Flexible self-supporting material as well as preparation method and application thereof

Abstract

The invention belongs to the field of flexible battery energy storage, and relates to a flexible self-supporting material and a preparation method and application thereof. The flexible self-supporting material comprises a carbon nanotube film, a Si / Ge film and a liquid metal film which are arranged in sequence. According to the invention, the carbon nanotube film is used as a flexible carrier, has good flexibility, mechanical property, conductivity and ultra-light weight, can greatly reduce the proportion of inactive substances in the electrode, and improves the energy density of the electrode material. Meanwhile, Si is easy to fall off from the traditional current collector Cu to cause damage to the electrode structure, and the carbon nanotube film well improves the defect and improves the stability of the electrode material.

Description

Technical Field

[0001] This invention belongs to the field of flexible battery energy storage, specifically, it relates to a flexible self-supporting material, its preparation method, and its application. Background Technology

[0002] With the continuous development of society, the demand for energy will continue to increase. Lithium-ion batteries, as an energy storage device, have received extensive research and attention. Due to their numerous advantages, they are widely used in various electronic devices. Currently, commercially available graphite can no longer meet the practical needs of high-energy-density lithium-ion batteries. Silicon (Si) has a theoretically extremely high capacity (~3579 mA hg). -1 Si 15 Li₄ (Si) is one of the most promising anode materials for lithium-ion batteries due to its advantages such as low price. However, the large volume variation, unstable solid electrolyte membrane, and poor conductivity of Si are the main problems limiting its use as anode material in lithium-ion batteries. Strategies to improve the electrochemical performance of Si mainly include: preparing Si with different nanostructures, combining it with other materials, and selecting novel binders and electrolytes.

[0003] Unlike traditional batteries, flexible batteries require each component to be flexible. The key to constructing flexible batteries lies in the combination of flexible current collectors and high-specific-capacity active materials. Due to significant volume changes, silicon (Si) can easily detach from traditional copper current collectors, damaging the electrode structure. Some studies have attempted to improve electrode stability by modifying copper current collectors, but this approach has yielded limited improvements. Carbon nanotube films, with their excellent flexibility, mechanical properties, and conductivity, are often used as flexible electrode carriers. Their ultra-light weight significantly reduces the proportion of inactive materials in the electrode. Over the past few decades, carbon nanotube research has made tremendous progress in yield, precise structural control, and performance optimization. Carbon nanotube films are gradually moving from the laboratory to industrialization, getting closer to practical applications.

[0004] Liquid metals (Ga, In, Sn, etc.) are liquid at room temperature and have excellent conductivity, flexibility, and fluidity, which can accommodate volume expansion and repair electrode surfaces. Summary of the Invention

[0005] The purpose of this invention is to provide a flexible self-supporting material and its preparation method. The flexible self-supporting material exhibits good flexibility and excellent electrochemical performance, and has great application potential in the field of battery energy storage. Its preparation method is simple and applicable to other high-capacity electrode materials.

[0006] A first aspect of the present invention provides a flexible self-supporting material comprising a carbon nanotube film, a Si / Ge film, and a liquid metal film arranged sequentially.

[0007] Optionally, the liquid metal in the liquid metal film is selected from at least one of gallium (Ga), indium (In), tin (Sn), In-Sn alloy, Ga-In alloy, Ga-In-Sn alloy, and metal- or non-metal-doped In-Sn alloy, Ga-In alloy, and Ga-In-Sn alloy.

[0008] Optionally, the mass ratio of In in the alloy to the total mass of other metals is 6 to 12:1, more preferably 8 to 10:1.

[0009] Optionally, the liquid metal is an In-Sn alloy.

[0010] Optionally, the carbon nanotube film serves as a flexible substrate with a thickness of 5–20 μm, the Si or Ge film has a thickness of 1–3 μm, and the liquid metal film has a thickness of 0.1–0.3 μm.

[0011] Optionally, the flexible self-supporting material does not contain conductive agents or binders.

[0012] A second aspect of the present invention provides a method for preparing the above-mentioned flexible self-supporting material, comprising the following steps:

[0013] (1) Carbon nanotube films were prepared by floating catalytic chemical vapor deposition;

[0014] (2) Si / Ge film and liquid metal film are sequentially prepared on the surface of carbon nanotube film by magnetron sputtering to obtain the flexible self-supporting material.

[0015] Optionally, step (1) includes: in the presence of hydrogen and an inert gas, contacting a carbon source and a catalyst at a high temperature to continuously grow carbon nanotubes, collecting carbon nanotube aggregates and pressing them into shape to prepare a carbon nanotube film.

[0016] Optionally, the carbon source is acetylene, the catalyst is ferrocene, and the inert gas is argon.

[0017] Optionally, the carbon source content is 4–8 wt%, based on the total weight of the carbon source, hydrogen, and inert gas.

[0018] Optionally, the weight ratio of carbon source to catalyst is 30 to 50:1.

[0019] Optionally, the volume ratio of hydrogen to inert gas is 1 to 3:1.

[0020] Optionally, the space velocity during the reaction process is 1500–2500 h⁻¹. -1 .

[0021] Optionally, the high temperature is 1300–1550°C.

[0022] Optionally, the sputtering conditions include: the magnetron sputtering system is evacuated to a vacuum level of 0.5 × 10⁻⁶. -4 ~1.5×10 -4 Pa, the sputtering gas is high-purity argon, and the working pressure is 0.5 to 1.5 Pa.

[0023] Optionally, the sputtering step includes: firstly pre-sputtering the target material, which includes a Si / Ge target and a liquid metal target; then sputtering the Si / Ge target to deposit a Si / Ge film on the carbon nanotube film; and then sputtering the liquid metal target to deposit a layer of liquid metal on the deposited Si / Ge.

[0024] Optionally, the sputtering conditions for Si / Ge targets include: a power of 100–200 W and a time of 50–100 min; the sputtering conditions for liquid metal targets include: a power of 10–30 W and a time of 10–30 min.

[0025] A third aspect of the present invention provides the application of the above-described flexible self-supporting material as an electrode material, preferably in flexible batteries.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] This invention utilizes carbon nanotube thin films as a flexible carrier, which possesses excellent flexibility, mechanical properties, conductivity, and ultralight weight. This significantly reduces the proportion of inactive materials in the electrode, thereby increasing the energy density of the electrode material. Simultaneously, Si easily detaches from the traditional current collector Cu, causing electrode structural damage; however, the carbon nanotube thin film effectively mitigates this drawback, improving the stability of the electrode material. One embodiment of this invention yields a flexible CNT / Si / LM electrode that eliminates the need for binders and conductive agents, while also increasing energy density. As a negative electrode material for lithium-ion batteries, it exhibits excellent cycle stability and rate performance. Notably, the flexible material preparation process of this invention eliminates the hazards and use of toxic solutions and solvents associated with traditional lithium-ion battery production. These characteristics not only reduce the consumption of natural resources but also promote the environmentally friendly and economical development of batteries.

[0028] Other features and advantages of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0029] Exemplary embodiments of the present invention will be described in more detail with reference to the accompanying drawings.

[0030] Figure 1 This is a digital photograph of a carbon nanotube film prepared by floating catalytic chemical vapor deposition in one embodiment of the present invention.

[0031] Figure 2 This is a scanning electron microscope image of a carbon nanotube film prepared by floating catalytic chemical vapor deposition in one embodiment of the present invention.

[0032] Figure 3 This is a digital photograph of a CNT / Si / LM flexible electrode material prepared by magnetron sputtering in one embodiment of the present invention.

[0033] Figure 4 This is a scanning electron microscope image of a CNT / Si / LM flexible electrode material prepared by magnetron sputtering in one embodiment of the present invention.

[0034] Figure 5 This is a cyclic voltammetry curve of the CNT / Si / LM flexible electrode material prepared in one embodiment of the present invention as a negative electrode material for a lithium-ion battery.

[0035] Figure 6 This is a charge-discharge test diagram of the CNT / Si / LM flexible electrode material prepared in one embodiment of the present invention as a negative electrode material for a lithium-ion battery.

[0036] Figure 7 The graphs show the cycle performance test results of the CNT / Si / LM flexible electrode material prepared in one embodiment of the present invention and the CNT / Si prepared in the control example. Detailed Implementation

[0037] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0038] The present invention provides a flexible self-supporting material comprising a carbon nanotube film, a Si / Ge film, and a liquid metal film arranged sequentially.

[0039] In this invention, "Si / Ge" refers to Si and / or Ge. For example, Si / Ge thin film refers to Si thin film and / or Ge thin film, the thickness of Si / Ge thin film refers to the total thickness of possible Si thin film and possible Ge thin film, and Si / Ge target material refers to Si target material and / or Ge target material.

[0040] The liquid metal in the liquid metal film includes, but is not limited to, at least one of gallium (Ga), indium (In), tin (Sn), In-Sn alloy, Ga-In alloy, Ga-In-Sn alloy, and metal- or non-metal-doped In-Sn alloy, Ga-In alloy, and Ga-In-Sn alloy.

[0041] According to a preferred embodiment of the present invention, the mass ratio of In in the alloy to the total mass of other metals is 6 to 12:1, more preferably 8 to 10:1.

[0042] More preferably, the liquid metal is an In-Sn alloy, and further, the mass ratio of In to Sn is 6 to 12:1, preferably 8 to 10:1.

[0043] In this invention, the carbon nanotube film serves as a flexible substrate, and its thickness is preferably 5–20 μm.

[0044] The present invention does not particularly limit the thickness of the other two layers. When used as an electrode material, the thickness of the Si / Ge thin film is preferably 0.2 to 3 μm, and the thickness of the liquid metal thin film is preferably 0.1 to 0.3 μm.

[0045] The flexible self-supporting material of the present invention does not contain conductive agents and binders. The meaning of conductive agents and binders is known to those skilled in the art, referring to conventional components that are mixed with active components to form electrode slurries.

[0046] The present invention also provides a method for preparing the above-mentioned flexible self-supporting material, comprising the following steps:

[0047] (1) Carbon nanotube films were prepared by floating catalytic chemical vapor deposition;

[0048] (2) Si / Ge film and liquid metal film are sequentially prepared on the surface of carbon nanotube film by magnetron sputtering to obtain the flexible self-supporting material.

[0049] The specific method for preparing carbon nanotube films by floating catalytic chemical vapor deposition is well known in the art. Specifically, in the presence of hydrogen and inert gas, a carbon source and a catalyst are brought into contact at high temperature to continuously grow carbon nanotubes. The carbon nanotube aggregates are collected and pressed into shape to prepare carbon nanotube films.

[0050] The carbon source is preferably acetylene, the catalyst is preferably ferrocene, and the inert gas is preferably argon.

[0051] The content of each component can be determined with reference to existing conditions. Based on the total weight of carbon source, hydrogen and inert gas, the content of carbon source in the system is preferably 4 to 8 wt%; the weight ratio of carbon source to catalyst is preferably 30 to 50:1.

[0052] The volume ratio of hydrogen to inert gas is preferably controlled to be 1 to 3:1.

[0053] The space velocity during the reaction process is preferably controlled at 1500–2500 h⁻¹. -1 .

[0054] The total carrier gas flow rate is preferably controlled at 2000 mL / min to 2500 mL / min.

[0055] The high temperature usually refers to 1300-1550℃.

[0056] According to a specific embodiment of the present invention, acetylene is used as the carbon source, ferrocene as the catalyst, and hydrogen and argon as the carrier gases to continuously grow carbon nanotubes at high temperature. The carbon nanotube aggregates are collected at the furnace inlet using a roller collector. After a certain period of collection, the carbon nanotube film aggregates are removed from the collection device and pressed into shape on a roller press under a certain pressure to prepare a carbon nanotube film.

[0057] The magnetron sputtering method of the present invention can be performed in a magnetron sputtering machine, and the sputtering conditions preferably include: the magnetron sputtering machine system is evacuated to a vacuum of 0.5 × 10⁻⁶. -4 ~1.5×10 -4 Pa, the sputtering gas is high-purity argon, and the working pressure is 0.5 to 1.5 Pa.

[0058] The term "high-purity argon" is a well-known term in the art, referring to argon gas with a purity of at least 99.99%, which is commercially available.

[0059] Specifically, the sputtering steps include: first, pre-sputtering the target material, which includes a Si / Ge target and a liquid metal target; then sputtering the Si / Ge target to deposit a Si / Ge film on the carbon nanotube film; and then sputtering the liquid metal target to deposit a layer of liquid metal on the deposited Si or Ge.

[0060] The sputtering conditions for each target material can be determined as needed. According to a preferred embodiment of the present invention, the sputtering conditions for Si / Ge target materials include: power of 100-200W and time of 50-100min.

[0061] According to a preferred embodiment of the present invention, the sputtering conditions for the liquid metal target include: a power of 10 to 30 W and a time of 10 to 30 min.

[0062] The thickness of Si / Ge thin films and liquid metal thin films can be controlled by adjusting the above conditions.

[0063] The flexible self-supporting material of the present invention can be used as an electrode material in flexible batteries, including but not limited to lithium batteries.

[0064] In one specific embodiment of this invention, a Si-based flexible self-supporting electrode material was prepared using floating catalytic chemical vapor deposition and magnetron sputtering. Carbon nanotube films, as a flexible substrate, meet the mechanical strength and flexibility requirements of flexible batteries. Liquid metal (LM) possesses excellent flexibility and other advantages, enabling good interfacial contact between Si and the liquid metal, which helps reduce electrode material breakage and improve cycle stability. As a lithium-ion battery anode material, it exhibits excellent electrochemical performance.

[0065] The flexible electrode prepared by this invention eliminates the need for binders and conductive agents, thereby increasing energy density. The flexible self-supporting electrode material prepared by this invention is suitable for energy storage devices in portable and wearable electronic devices and exhibits excellent electrochemical performance.

[0066] The present invention will be further described below with reference to the embodiments, but the scope of the present invention is not limited to these embodiments.

[0067] Unless otherwise specified in the examples, all procedures were performed under standard conditions or conditions recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0068] Example 1

[0069] (1) Ferrocene was used as a catalyst, acetylene as the carbon source, and hydrogen and argon (volume ratio 2:1) as carrier gases. A mixture of carbon source, hydrogen, argon, and water vapor was introduced at a reaction temperature of 1300–1550 °C. The volume ratio of hydrogen to carbon source to argon was 10:1:5, the volume fraction of water vapor was 0.5%, the weight ratio of carbon source to catalyst was 40:1, and the space velocity during the reaction was 2000 h⁻¹. -1 Carbon nanotubes can then be grown on the catalyst surface.

[0070] (2) Stable carbon nanotubes, grown and formed, float to the furnace opening under the influence of a carrier gas. They are then pulled out of the furnace using a roller collector, stretched in multiple stages, and collected on the roller collector. The carbon nanotube aggregates are then removed and pressed into carbon nanotube films of varying thicknesses using a roller press. A digital photograph of the carbon nanotube film is shown below. Figure 1 As shown, the scanning electron microscope image is as follows: Figure 2 As shown.

[0071] (3) CNT / Si / LM was prepared by magnetron sputtering using a 10 μm thick carbon nanotube film as a substrate. The magnetron sputtering system was evacuated to a vacuum of 1.0 × 10⁻⁶. -4The sputtering gas was high-purity Ar, and the working pressure was 1.0 Pa. First, the target was pre-sputtered for 5 min to remove impurities from the target surface. Then, the Si target was sputtered at 150 W for 60 min to deposit a Si layer with a thickness of 0.4 μm on the CNT film. Next, the LM target was sputtered at 20 W for 15 min to deposit an LM layer with a thickness of 0.1 μm on the deposited Si, thereby preparing the CNT / Si / LM flexible electrode material.

[0072] Digital photographs of the CNT / Si / LM flexible electrode material are shown below. Figure 3 As shown, the scanning electron microscope image is as follows: Figure 4 As shown.

[0073] Example 2

[0074] Using the carbon nanotube film with a thickness of 10 μm prepared in Example 1 as a substrate, CNT / Si / LM was prepared by magnetron sputtering. The magnetron sputtering system was evacuated to a vacuum of 1.0 × 10⁻⁶. -4 The sputtering gas was high-purity Ar, and the working pressure was 1.0 Pa. First, the target was pre-sputtered for 5 min to remove impurities from the target surface. Then, the Si target was sputtered at 100 W for 100 min to deposit a Si layer with a thickness of 0.6 μm on the CNT film. Next, the LM target was sputtered at 10 W for 30 min to deposit an LM layer with a thickness of 0.2 μm on the deposited Si, thereby preparing the CNT / Si / LM flexible electrode material.

[0075] Example 3

[0076] Using the carbon nanotube film with a thickness of 10 μm prepared in Example 1 as a substrate, CNT / Si / LM was prepared by magnetron sputtering. The magnetron sputtering system was evacuated to a vacuum of 1.0 × 10⁻⁶. -4 The sputtering gas was high-purity Ar, and the working pressure was 1.0 Pa. First, the target was pre-sputtered for 5 min to remove impurities on the target surface. Then, the Si target was sputtered at 200 W for 50 min to deposit a Si layer with a thickness of 0.45 μm on the CNT film. Next, the LM target was sputtered at 30 W for 10 min to deposit an LM layer with a thickness of 0.25 μm on the deposited Si, thereby preparing the CNT / Si / LM flexible electrode material.

[0077] Compare with Example 1

[0078] CNT / Si was prepared using a carbon nanotube film with a thickness of 10 μm obtained in Example 1 as a substrate by magnetron sputtering. The magnetron sputtering system was evacuated to a vacuum of 1.0 × 10⁻⁶. -4The sputtering gas was high-purity Ar, and the working pressure was 1.0 Pa. First, the target was pre-sputtered for 5 min to remove impurities from its surface. Then, the Si target was sputtered at 150 W for 120 min to deposit a Si layer on the CNT film. A CNT / Si film was thus prepared. The Si thickness was 0.8 μm.

[0079] Test case

[0080] The CNT / Si / LM flexible electrode material prepared in Example 1 was used as a negative electrode material for lithium-ion batteries for cyclic voltammetry testing, and the results are as follows: Figure 5 As shown, the electrode material exhibits obvious redox peaks, demonstrating the feasibility of CNT / Si / LM flexible electrode material as a negative electrode material for lithium-ion batteries.

[0081] The CNT / Si / LM flexible electrode material prepared in Example 1 was used as a negative electrode material for lithium-ion batteries for charge-discharge testing. The electrochemical performance results for the first three cycles are as follows: Figure 6 As shown in the figure, the CNT / Si / LM flexible electrode material exhibits high electrochemical performance.

[0082] The CNT / Si / LM flexible electrode material prepared in Example 1 and the CNT / Si prepared in the control example were subjected to cycle performance tests, and the results are as follows: Figure 7 As shown in the figure, the CNT / Si / LM flexible electrode material exhibits good cycle stability and a higher specific capacity than CNT / Si.

[0083] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

[0084] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

Claims

1. A flexible self-supporting material, characterized in that, The flexible self-supporting material comprises a carbon nanotube film, a Si / Ge film, and a liquid metal film arranged sequentially.

2. The flexible self-supporting material according to claim 1, wherein, The liquid metal in the liquid metal film is selected from at least one of gallium (Ga), indium (In), tin (Sn), In-Sn alloy, Ga-In alloy, Ga-In-Sn alloy, and metal- or non-metal-doped In-Sn alloy, Ga-In alloy, and Ga-In-Sn alloy.

3. The flexible self-supporting material according to claim 2, wherein, The mass ratio of In in the alloy to the total mass of other metals is 6 to 12:1, more preferably 8 to 10:1; Preferably, the liquid metal is an In-Sn alloy.

4. The flexible self-supporting material according to claim 1, wherein, The carbon nanotube film serves as a flexible substrate with a thickness of 5–20 μm, the Si / Ge film has a thickness of 0.2–3 μm, and the liquid metal film has a thickness of 0.1–0.3 μm.

5. The flexible self-supporting material according to any one of claims 1-4, wherein, The flexible self-supporting material does not contain conductive agents or binders.

6. A method for preparing the flexible self-supporting material according to any one of claims 1-5, comprising the following steps: (1) Carbon nanotube films were prepared by floating catalytic chemical vapor deposition; (2) Si / Ge film and liquid metal film are sequentially prepared on the surface of carbon nanotube film by magnetron sputtering to obtain the flexible self-supporting material.

7. The method for preparing the flexible self-supporting material according to claim 6, wherein, Step (1) includes: in the presence of hydrogen and inert gas, contacting the carbon source and the catalyst at high temperature to continuously grow carbon nanotubes, collecting the carbon nanotube aggregates and pressing them into shape to prepare a carbon nanotube film.

8. The method for preparing the flexible self-supporting material according to claim 7, wherein, The carbon source is acetylene, the catalyst is ferrocene, and the inert gas is argon. Based on the total weight of carbon source, hydrogen and inert gas, the carbon source content is 4-8 wt%. The weight ratio of carbon source to catalyst is 30–50:1; The volume ratio of hydrogen to inert gas is 1 to 3:1; The space velocity during the reaction process is 1500–2500 h⁻¹. -1 ; The high temperature is 1300–1550℃.

9. The method for preparing the flexible self-supporting material according to claim 6, wherein, The sputtering conditions include: the magnetron sputtering system is evacuated to a vacuum of 0.5 × 10⁻⁶. -4 ~1.5×10 -4 Pa, the sputtering gas is high-purity argon, and the working pressure is 0.5 to 1.5 Pa.

10. The method for preparing the flexible self-supporting material according to claim 6, wherein, The sputtering steps include: first, pre-sputtering the target material, which includes a Si / Ge target and a liquid metal target; then sputtering the Si / Ge target to deposit a Si / Ge film on the carbon nanotube film; and then sputtering the liquid metal target to deposit a layer of liquid metal on the deposited Si / Ge.

11. The method for preparing the flexible self-supporting material according to claim 10, wherein, The sputtering conditions for Si / Ge targets include: power of 100–200 W and time of 50–100 min. The sputtering conditions for liquid metal targets include: power of 10–30 W and time of 10–30 min.

12. The application of the flexible self-supporting material according to any one of claims 1-5 as an electrode material, preferably in flexible batteries.

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