Method for in-situ modification of positive electrode current collector by plasma technology

Abstract

The invention discloses a method for in-situ modification of a positive electrode current collector by a plasma technology, which comprises the following steps: placing the current collector in a plasma reaction cavity, vacuumizing and introducing reaction gas; starting plasma discharge, and reacting for a set time to enable reaction gas to react on the surface of the current collector to form bonding; wherein the plasma treatment power is 100 to 300W, and the time is 10 to 30 minutes. Compared with a traditional method for pyrolyzing nitrogen-containing or fluorine-containing organic matter to react with the material, the method has the advantages that firstly, the reaction time is greatly shortened, even magnitude difference exists, secondly, the reaction temperature is lower than 100 DEG C, and the morphology structure of a material body is not damaged.

Description

Technical Field

[0001] This invention belongs to the field of energy storage battery technology, specifically relating to a method for in-situ modification of positive electrode current collector using plasma technology. Background Technology

[0002] With global energy demand continuing to rise and the transition to sustainable energy accelerating, traditional energy sources such as coal, oil, and natural gas are no longer sufficient to meet current development needs. Against this backdrop, countries worldwide are expanding the development and utilization of renewable energy sources such as wind and solar power year by year. However, the inherent intermittency and volatility of wind and solar energy lead to power instability issues during grid connection. Energy storage technology, as a key means to address this pain point, can not only effectively smooth out the output fluctuations of renewable energy but also serve as a core support for building a new power system dominated by new energy sources and achieving the "dual-carbon" strategic goal.

[0003] Liquid metal batteries, a novel energy storage battery technology developed in recent years, use widely available and inexpensive liquid metals or alloys as electrodes and inorganic molten salts as electrolytes. This unique three-layer all-liquid structure breaks the solid-liquid reaction mechanism of traditional batteries, fundamentally avoiding the structural deformation problem of solid electrodes during charge and discharge, thus possessing an ultra-long cycle life. With its significant advantages of long lifespan, high safety, and low cost, liquid metal batteries have shown extremely broad application potential in the field of large-scale energy storage.

[0004] The positive electrode of liquid metal batteries is usually a metal or intermetallic alloy such as antimony (Sb), bismuth (Bi), tin (Sn), lead (Pb), and tellurium (Te). However, these metals have poor wettability on commonly used graphite current collectors, which can easily lead to delamination, resulting in structural instability and low capacity utilization. Summary of the Invention

[0005] The purpose of this section is to outline some aspects of embodiments of the present invention and to briefly describe some preferred embodiments. Simplifications or omissions may be made in this section, as well as in the abstract and title of this application, to avoid obscuring the purpose of these documents; however, such simplifications or omissions should not be construed as limiting the scope of the invention.

[0006] In view of the problems existing in the above and / or prior art, the present invention is proposed.

[0007] Therefore, the purpose of this invention is to overcome the shortcomings of the prior art and provide a method for in-situ modification of positive electrode current collectors using plasma technology.

[0008] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a method for in-situ modification of a positive electrode current collector using plasma technology, characterized in that it includes: The current collector is placed in the plasma reaction chamber, a vacuum is drawn and the reaction gas is introduced; the plasma discharge is turned on, and the reaction time is set to allow the reaction gas to react on the surface of the current collector to form bonds. The plasma processing power is 100-300W, and the time is 10-30min.

[0009] In a preferred embodiment of the present invention, the reacting gas includes one or more of CF4, N2, and O2.

[0010] In a preferred embodiment of the method described in this invention, the current collector comprises graphite and stainless steel.

[0011] As a preferred embodiment of the method described in this invention, the shape of the current collector includes a cylinder and / or a square barrel.

[0012] In a preferred embodiment of the method described in this invention, the radio frequency source of the plasma is 2.45-40MHz.

[0013] In a preferred embodiment of the method described in this invention, the radio frequency source of the plasma is 13.56 MHz.

[0014] In a preferred embodiment of the method described in this invention, the plasma processing power is 200W.

[0015] In a preferred embodiment of the method described in this invention, the plasma treatment time is 10 minutes.

[0016] Another object of the present invention is to overcome the shortcomings of the prior art and provide a modified positive current collector prepared by a method.

[0017] Another objective of this invention is to overcome the shortcomings of the prior art and provide an application of a modified positive electrode current collector in energy storage batteries.

[0018] Beneficial effects of this invention: (1) The plasma treatment method adopted in this invention is to bombard the surface of the current collector with active plasma generated by high voltage ionization, so as to react with the current collector or exchange energy. The plasma source has a high reaction energy. For gases such as CF4 that are difficult to decompose at room temperature or under heat treatment, it can effectively break the CF bond and generate high-energy F atoms, thereby reacting with the current collector. Compared with the traditional method of pyrolyzing nitrogen-containing or fluorine-containing organics to react with materials, the reaction time is greatly shortened, even by orders of magnitude. Secondly, the reaction temperature is below 100°C, which does not damage the morphology and structure of the material.

[0019] (2) The present invention can obtain modified current collectors with different bonds on the surface by simply changing the reaction gas, and has high controllability.

[0020] (3) The plasma used in this invention can induce an electric field on the surface of the current collector, thereby etching the surface. By controlling parameters such as reaction power and time, current collectors with modified layers of different thicknesses can be obtained.

[0021] (4) The present invention can generate specific bonds in situ on the surface of the current collector, avoiding voids or cracks caused by physical bonding.

[0022] (5) The present invention has a short processing time and can process multiple current collectors at the same time, making it suitable for mass production. Attached Figure Description

[0023] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein: Figure 1 This is a flowchart of the preparation method of the plasma-modified positive electrode current collector according to the present invention; Figure 2 This is a scanning electron microscope (SEM) image of the graphite current collector in the blank group of this invention; Figure 3 This is a scanning electron microscope (SEM) image of the graphite current collector obtained in Example 1 of the present invention; Figure 4 This is the X-ray energy dispersive X-ray spectroscopy (EDS mapping) of the graphite current collector obtained in Example 1 of the present invention, corresponding to the F element distribution; Figure 5 This is a contact diagram between the positive electrode and the current collector in the blank group of this invention; Figure 6 This is the contact diagram between the positive electrode and the current collector obtained in Embodiment 2 of the present invention; Figure 7 This is a graph showing the calculated adsorption energies between Bi and different gas-introduced elements in Examples 1-4 of this invention; Figure 8 This is a comparison chart of the charge-discharge curves of the liquid metal batteries in Example 3 and the blank group at a rate of 0.1C. Figure 9 This is a comparison chart of the charge-discharge curves of the Li-Bi liquid metal batteries of Comparative Example 1 and Example 2 of the present invention at a rate of 0.3C. Figure 10This is a comparison chart of the charge-discharge curves of the Li-Bi liquid metal batteries of Comparative Example 2 and Example 4 of the present invention at a rate of 0.3C. Figure 11 This is a comparison chart of the charge-discharge curves of the Li-Sb liquid metal batteries of Comparative Example 3 and Example 6 of the present invention at a rate of 0.1C. Detailed Implementation

[0024] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the examples in the specification.

[0025] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0026] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0027] Unless otherwise specified, all raw materials used in the embodiments of this invention are commercially available.

[0028] Example 1 (1) Place the cleaned graphite current collector parallel to the bottom of the plasma cavity, evacuate to 50 Pa, and then introduce CF4 gas for 5 minutes to remove the air in the cavity. (2) Adjust the power of the plasma equipment to 100W, the radio frequency source to 13.56MHz, turn on the discharge, so that the plasma beam bombards the graphite surface evenly, and the processing time is 20 minutes. (3) After the reaction is complete, stop the discharge and continue to pass CF4 gas through the cooling process for 5 minutes. After cooling to room temperature, pass air through the current collector and remove the current collector to obtain a graphite current collector with CF bonds on the surface.

[0029] (4) Battery assembly process Surface cleaning treatment of the positive electrode graphite current collector: The graphite current collector is placed in ethanol and ultrasonically cleaned for 10 minutes to remove oil and dust impurities attached to the surface; it is vacuum dried at 100℃ for 3 hours, and after cooling to room temperature, it is transferred to a glove box for later use.

[0030] In an inert gas (Ar) glove box, the negative electrode is prepared by weighing lithium metal particles and placing them in a quartz container. The container is then placed on a temperature-controlled heating platform and heated to 200°C (higher than the lithium melting point of 180.5°C). After the lithium metal is completely melted into a liquid state, the pretreated nickel foam is slowly immersed into the liquid lithium and kept immersed for 5-8 minutes. During this time, the container is gently shaken to ensure that the liquid lithium fully wets the pore structure of the nickel foam.

[0031] Under the protection of inert gas (Ar), the positive electrode Bi is assembled with the battery body: the positive electrode is placed in a graphite current collector, and then the dry electrolyte (LiF-LiCl-LiBr, molar ratio of 22:31:47) is heated to above the electrolyte melting point (440℃) to melt it. The molten salt is slowly poured into the graphite current collector. When the molten salt is in a flowing state and has not solidified, the foamed nickel composite negative electrode with adsorbed liquid lithium is gently placed into the molten salt, ensuring that the foamed nickel is completely submerged in the molten salt and has no direct contact with the positive electrode.

[0032] The battery casing is encapsulated under inert gas (Ar) protection: laser welding technology is used to seal the seam between the casing and the top cover. Ar gas is continuously introduced during the welding process to prevent oxidation of the welded area.

[0033] Example 2 The difference from Example 1 is that the power of the equipment in step (2) is 150W and the processing time is 15 minutes.

[0034] Example 3 The difference from Example 1 is that the power of the equipment in step (2) is 200W and the processing time is 10 minutes.

[0035] Example 4 The difference from Example 3 is that step (3) replaces CF4 gas with N2 gas.

[0036] Example 5 The difference from Example 2 is that the current collector in step (1) is stainless steel, and the positive electrode in step (4) is Sb.

[0037] Example 6 The difference from Example 3 is that the positive electrode in step (4) is Sb, and in step (3) the CF4 gas is replaced with O2 gas.

[0038] Figure 2 and Figure 3 The images show SEM images of the untreated graphite current collector surface (blank group) and the graphite current collector surface obtained in Example 1, respectively. It can be seen that the untreated graphite current collector surface is relatively smooth, with only some pits. In contrast, the graphite current collector surface obtained in Example 1 shows more pits, which is attributed to the etching effect of the CF4 matrix on the graphite current collector surface.

[0039] Figure 4 It is explained that in Example 1, after CF4 plasma treatment, F element was introduced into the graphite surface, forming CF bonds.

[0040] Figure 5 and Figure 6 The contact angles of molten Bi metal with the untreated graphite current collector surface in the blank group and the graphite current collector surface obtained in Example 1 were measured, respectively. It can be seen that the contact angle between the untreated blank group and the molten Bi metal is significantly larger than that of the graphite current collector obtained in Example 2, indicating that the treatment with CF4 plasma can effectively improve the wettability of the liquid metal cathode on the graphite current collector.

[0041] Figure 7 This diagram shows the calculated adsorption energies between Bi and different gases (CF4, N2, O2, H2) introduced in Examples 1-4 of this invention. It can be seen that the adsorption energies between Bi and F, N, and O are all negative, indicating the adsorption effect of F, N, and O on Bi, demonstrating that the addition of F, N, and O significantly improves the wettability between the cathode and the current collector. However, the adsorption energies between Bi and C and H on the graphite current collector are positive, indicating that Bi has difficulty adsorbing C and H. Figure 8 The graph shows a comparison of charge-discharge curves of Li-Bi batteries in the blank group using untreated graphite current collectors and in the modified graphite current collectors obtained in Example 3. It can be seen that the voltage difference between the charge-discharge plateaus in Example 3 is 0.12V, while the voltage difference in the blank group is 0.16V. This indicates that the improved wettability between the liquid metal cathode and the current collector effectively reduces contact resistance, thereby reducing battery polarization.

[0042] Comparative Example 1 The blank group consists of untreated, custom-sized graphite current collectors, which are used directly after being ultrasonicated with alcohol for 10 minutes. Specifically: 6Ah battery: It is cylindrical in shape, with an inner diameter of 30cm, an outer diameter of 40cm, a height of 55cm, and a bottom thickness of 5cm.

[0043] 20Ah battery: It is cylindrical in shape, with an inner diameter of 60cm, an outer diameter of 64cm, a height of 60cm, and a bottom thickness of 2cm.

[0044] Comparative Example 2 The difference between this comparative example and Example 2 is that the processing time of 15 minutes in step (2) is replaced with 5 minutes, while the rest of the steps are the same as in Example 2. Due to the insufficient processing time, this comparative example still has a large polarization compared to Example 2. The difference between the charge and discharge voltage plateaus at a 0.3C rate is 0.25V, while the difference between the charge and discharge voltage plateaus in Example 2 is 0.21V.

[0045] Comparative Example 3 The difference between this comparative example and Example 4 is that the processing power of 200W in step (2) is replaced with 50W, while the rest of the steps are the same as in Example 4. Due to the lower processing power, this comparative example still has a large polarization compared to Example 4, with a charge-discharge voltage plateau difference of 0.1V at a 0.1C rate, while the charge-discharge voltage plateau difference in Example 2 is 0.05V.

[0046] Comparative Example 4 The difference between this comparative example and Example 6 is that the CF4 gas in steps (1) and (3) is replaced with Ar, while the remaining steps are the same as in Example 6. Since Ar cannot form chemical bonds with graphite on the surface and cannot improve the simple wettability between the current collector and the positive electrode, this comparative example still has a large polarization compared to Example 6. The difference in charge-discharge voltage plateau at 0.1C rate is 0.12V, while the difference in charge-discharge voltage plateau in Example 6 is 0.05V.

[0047] Figure 9 The graph shows a comparison of the charge-discharge curves of Li-Bi batteries in the graphite current collector of Comparative Example 1 and the modified graphite current collector obtained in Example 2. It can be seen that the voltage difference between the charge-discharge plateaus in Example 2 is 0.21V, while the voltage difference between the charge-discharge plateaus in Comparative Example 1 is 0.25V, indicating that insufficient processing time cannot significantly improve the wettability between the graphite current collector and the positive electrode. Figure 10 The graph shows a comparison of the charge-discharge curves of the Li-Bi battery in the graphite current collector of Comparative Example 2 and the modified graphite current collector obtained in Example 4. It can be seen that the voltage difference between the charge-discharge plateaus in Example 4 is 0.05V, while the voltage difference between the charge-discharge plateaus in Comparative Example 2 is 0.1V, indicating that insufficient processing power cannot significantly improve the wettability between the graphite current collector and the positive electrode. Figure 11 The graph shows a comparison of the charge-discharge curves of Li-Sb batteries in the graphite current collector of Comparative Example 3 and the modified graphite current collector obtained in Example 6. It can be seen that the voltage difference between the charge-discharge plateaus in Example 6 is 0.05V, while the voltage difference between the charge-discharge plateaus in Comparative Example 3 is 0.12V, indicating that Ar treatment cannot improve the wettability between the graphite current collector and the positive electrode.

[0048] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the present invention.

Claims

1. A method for in-situ modification of a positive electrode current collector using plasma technology, characterized in that: include, The current collector is placed in the plasma reaction chamber, a vacuum is drawn and the reaction gas is introduced; the plasma discharge is turned on, and the reaction time is set to allow the reaction gas to react on the surface of the current collector to form bonds. The plasma processing power is 100-300W, and the time is 10-30min.

2. The method as described in claim 1, characterized in that: The reactant gas includes one or more of CF4, N2, and O2.

3. The method as described in claim 1, characterized in that: The current collector includes graphite and stainless steel.

4. The method as described in claim 3, characterized in that: The shape of the current collector includes cylinder and / or square barrel.

5. The method as described in claim 1, characterized in that: The radio frequency source of the plasma is 2.45-40MHz.

6. The method as described in claim 5, characterized in that: The radio frequency source of the plasma is 13.56MHz.

7. The method as described in claim 1, characterized in that: The plasma processing power is 200W.

8. The method as described in claim 1, characterized in that: The plasma treatment time is 10 minutes.

9. The modified positive electrode current collector prepared by the method according to claims 1 to 8.

10. The application of the modified positive electrode current collector as described in claim 9 in energy storage batteries.

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