Liquid metal / polymer composite three-dimensional current collector and rapid preparation method thereof

Abstract

The present application relates to the field of negative electrode-free lithium metal battery, and more particularly discloses a liquid metal / polymer composite three-dimensional current collector and a rapid preparation method thereof, which comprises the following steps: S1, printing a flexible polymer substrate according to a three-dimensional model by using a composite powder through additive manufacturing technology; S2, carrying out wet treatment on the polymer substrate; S3, modifying the surface of the polymer substrate; S4, oxidizing the liquid metal and transferring it to the surface of the polymer substrate; and S5, assembling a half battery by using the polymer substrate with a liquid metal surface coating and a lithium sheet, and applying a current to make the liquid metal surface deposit lithium in situ. The method combines additive manufacturing and three-dimensional transfer technology to prepare a polymer-based negative electrode current collector with good flexibility and light weight, which has a regular pore structure and a lithiumophilic liquid metal coating, and can synergistically promote the uniform deposition and densification growth of lithium, thereby solving the problems of dendrite growth and volume change in lithium metal batteries.

Description

Technical Field

[0001] This invention relates to the field of negative electrode-free lithium metal batteries, and more specifically, to a liquid metal / polymer composite three-dimensional current collector and its rapid preparation method. Background Technology

[0002] Lithium metal has a low density (0.53 g / cm³). 3 Lithium metal (LMW) batteries are considered the holy grail of lithium-ion battery anode materials due to their advantages such as low potential (-3.04 V vs. SHE) and high theoretical specific capacity (3860 mAh / g). Among these, anode-free LMW batteries are expected to have an energy density exceeding 400 Wh / kg and offer advantages in cost and battery manufacturing, making them the ultimate choice for lithium metal batteries. However, issues such as lithium dendrite growth, interface instability, and electrode volume changes significantly limit the development and application of anode-free LMW batteries.

[0003] To address the aforementioned issues, methods for improving lithium metal battery anode current collectors can be broadly categorized into two types: chemical modification and structural modification. The former involves chemically modifying the current collector. For example, Chinese patent CN114649502A discloses a liquid metal coating, its preparation method, and its application in lithium-free lithium metal batteries. This method involves coating a planar foil surface with liquid metal to prepare the lithium metal battery anode. The deposition of lithium metal on the current collector becomes more ordered and denser due to the influence of the liquid metal coating. The latter method optimizes the current collector by constructing a three-dimensional structure. For instance, Chinese patent CN115347196A discloses a three-dimensional porous current collector for lithium batteries, its preparation method, and its application. This method involves immersing a metal foil in an oxidation etching solution to obtain a surface-porous three-dimensional current collector. The porous structure can reduce local current density to suppress lithium dendrite growth and alleviate volume expansion during lithium insertion and extraction. Furthermore, current researchers often combine these two methods, attempting to composite metal / non-metal lithiophilic layers with porous current collector materials to prepare lithium metal battery anodes. For example, Chinese patent CN112216811A discloses a method for preparing an ultrathin lithium metal anode, which achieves stable and uniform lithium deposition by electrospinning a layer of electrochemically stable hybrid lithium-loving fibers on the surface of copper foil.

[0004] The above-mentioned methods for preparing lithium metal anode current collectors can effectively improve the lithium storage performance and cycle stability of the anode. However, there are also obvious shortcomings and drawbacks: (1) For two-dimensional current collectors (planar foils), it is still impossible to solve the problem of electrode volume change during lithium delithiation and lithium insertion. (2) Combining metal / non-metal lithiophilic layers with porous current collector materials, these porous material substrates include various metal foams, dealloyed porous materials, metal meshes, etc., which are not conducive to improving the mass energy density of lithium metal batteries. (3) Chemical etching and other methods are usually difficult to precisely control the shape, size and structural distribution of pores, which is not conducive to the uniform distribution of electric field and ion concentration field, and irregular disordered pore channels may hinder the solid-phase transport of lithium ions. Therefore, how to design a new three-dimensional composite current collector with regular pore structure still needs to be studied. Summary of the Invention

[0005] To address the aforementioned shortcomings and improvement needs of existing technologies, this invention provides a liquid metal / polymer composite three-dimensional current collector and its rapid preparation method. This method combines additive manufacturing with three-dimensional transfer technology to produce a polymer-based negative electrode current collector with good flexibility and relatively light weight. It possesses both a regular porous structure and a lithiophilic liquid metal coating, which synergistically promotes uniform lithium deposition and densification growth, thereby solving problems such as dendrite growth and volume changes in lithium metal batteries.

[0006] To achieve the above objectives, according to one aspect of the present invention, a rapid preparation method for a liquid metal / polymer composite three-dimensional current collector is provided, comprising the following steps:

[0007] S1. Construct a three-dimensional model of the battery negative electrode, and use additive manufacturing technology to print a flexible polymer substrate according to the constructed three-dimensional model using composite powder. The composite powder includes polymer powder and rheology modifier powder.

[0008] S2. Wet the polymer substrate; thoroughly wet the polymer substrate with a mixture of polyvinyl alcohol and flame retardant.

[0009] S3. Modify the surface of the polymer substrate by introducing hydroxyl and carboxyl polar groups;

[0010] S4. Oxidize the liquid metal and transfer it to the surface of the polymer substrate;

[0011] S5. Assemble a half-cell by attaching a polymer substrate with a liquid metal surface coating to a lithium sheet, and apply an electric current to deposit lithium in situ on the liquid metal surface.

[0012] As a further preferred embodiment, in step S1, the additive manufacturing technology is selective laser sintering, fused deposition modeling, or photopolymer 3D printing.

[0013] As a further preferred embodiment, in step S1, the polymer powder is thermoplastic polyurethane; and the rheology modifier is at least one of fumed silica and polyethylene wax powder.

[0014] As a further preferred embodiment, in step S1, the mass ratio of the polymer powder to the rheology modifier in the composite powder is 98:1 to 100:1.

[0015] As a further preferred embodiment, in step S2, the degree of polymerization of the polyvinyl alcohol used in the polyvinyl alcohol and flame retardant mixed solution is 500~2400, the degree of alcoholysis is 88%, the flame retardant is ammonium polyphosphate or melamine, the mass fraction of polyvinyl alcohol is 70~92%, and the mass fraction of the flame retardant is 8~30%.

[0016] As a further preferred embodiment, in step S3, the surface of the polymer substrate is treated with low-temperature plasma technology, wherein the treatment atmosphere of the low-temperature plasma technology is oxygen or argon.

[0017] As a further preferred embodiment, in step S4, the liquid metal is a room temperature gallium-based liquid metal, including any one of gallium, gallium-indium alloy, and gallium-indium-tin alloy.

[0018] As a further preferred embodiment, in step S5, the current density for in-situ lithium deposition is 0.1 mA cm⁻¹. –2 ~ 2 mAcm –2 The capacity is 1 mAh cm –2 ~ 10 mAh cm –2 .

[0019] According to another aspect of the present invention, a liquid metal / polymer composite three-dimensional current collector is provided, which is prepared by the above-described rapid preparation method.

[0020] In summary, compared with the prior art, the above-described technical solutions conceived by this invention mainly possess the following technical advantages:

[0021] 1. The lithium metal battery anode with a regular porous structure formed by 3D printing can effectively alleviate the volume expansion during the charging and discharging process of lithium metal batteries; at the same time, the directional porous structure is conducive to reducing the local current density and uniform lithium ion flux, thereby reducing the lithium dendrite growth rate.

[0022] 2. Using a polymer-based lithium metal battery anode helps reduce the weight of the lithium metal anode and improve the mass energy density of the lithium metal battery. At the same time, adding flame retardants to the polyvinyl alcohol coating can effectively prevent the polymer substrate from burning.

[0023] 3. By transferring liquid metal onto a polymer substrate, not only is the conductivity of the current collector guaranteed, but the pre-deposition of lithium alloys the liquid metal to form a lithium-liquid metal alloy layer, providing more lithium-affinity sites for lithium deposition. This further promotes uniform nucleation and densification of lithium on the liquid metal surface, improving the cycle stability and safety of lithium metal batteries. Attached Figure Description

[0024] Figure 1 This is a flowchart illustrating the preparation method of a liquid metal / polymer composite three-dimensional current collector according to an embodiment of the present invention.

[0025] Figure 2 This is a schematic diagram of the preparation process of the liquid metal / polymer composite three-dimensional current collector in an embodiment of the present invention. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0027] Please see Figure 1 and Figure 2 This invention proposes a liquid metal / polymer composite three-dimensional current collector and its rapid preparation method, specifically including the following steps:

[0028] S1. Construct a three-dimensional model of the battery negative electrode, and use additive manufacturing technology to print a flexible polymer substrate according to the constructed three-dimensional model using composite powder. The composite powder includes polymer powder and rheology modifier powder.

[0029] Specifically, the additive manufacturing technology is selective laser sintering, fused deposition modeling, or photopolymer 3D printing. Selective laser sintering is also known as SLS. The polymer powder is thermoplastic polyurethane, which has good temperature resistance compared to the battery's operating temperature range. The rheology modifier is at least one of fumed silica and polyethylene wax powder. The mass ratio of polymer powder to rheology modifier in the composite powder is 98:1 to 100:1. The rheology modifier prevents powder agglomeration and improves powder flowability. At the same time, excessive rheology modifier can lead to poor polymer powder melting and bonding during laser sintering, resulting in decreased sample accuracy and performance. In this embodiment, a mass ratio of 100:1 is preferred.

[0030] Preferably, the three-dimensional model of the battery negative electrode is a three-period minimally curved porous structure of 40 mm × 25 mm × 2 mm. To ensure its mechanical strength, the volume fraction of the polymer substrate is between 15% and 25% to prevent it from easily breaking during the cycling process of the lithium metal battery, while also helping to improve the energy density of the lithium metal battery.

[0031] S2. In order to ensure the adhesion effect between the liquid metal and the polymer, the polymer substrate is fully impregnated with a mixed solution of polyvinyl alcohol and flame retardant and dried until a film is formed to obtain a polymer substrate coated with flame retardant polyvinyl alcohol.

[0032] Specifically, the polyvinyl alcohol used in the polyvinyl alcohol and flame retardant mixture has a degree of polymerization of 500-2400 and a degree of alcoholysis of 88%. The flame retardant used is ammonium polyphosphate or melamine. The mass fraction of polyvinyl alcohol is 70-92%, and the mass fraction of flame retardant is 8-30%.

[0033] Preferably, the impregnation process requires immersing the polymer substrate in a mixed solution of polyvinyl alcohol and flame retardant, and continuously stirring the solution until no more bubbles are observed emerging from the polymer substrate, ensuring that the entire surface of the substrate is wetted by the solution. Afterward, it is placed in an electric heating drying oven for drying. The mass fraction of the flame retardant is 8-30%. Within this range, the polyvinyl alcohol film formed on the surface of the polymer substrate after drying has the best flame retardant effect.

[0034] S3. The substrate surface is modified using low-temperature plasma technology to introduce hydroxyl and carboxyl polar groups;

[0035] Specifically, the processing atmosphere of the low-temperature plasma technology is either oxygen or argon.

[0036] Preferably, the low-temperature plasma treatment process parameters are: Ar atmosphere, power of 122 W, time of 5 min, and pressure of 10 Pa; or O2 atmosphere, power of 122 W, time of 2 min, and pressure of 15 Pa. Low-temperature plasma treatment can introduce polar oxygen-containing functional groups such as hydroxyl, carbonyl, and carboxyl groups onto the surface of the flame-retardant polyvinyl alcohol coating, thereby forming an active coating surface, which effectively improves the adhesion stability of liquid metal and prevents it from falling off during cyclic charging and discharging.

[0037] S4. Oxidize and transfer room temperature liquid metal onto the surface of a polymer substrate;

[0038] Specifically, the liquid metals mentioned are all room temperature gallium-based liquid metals, including any one of gallium, gallium-indium alloy, and gallium-indium-tin alloy.

[0039] Preferably, the oxidation process can be assisted by a magnetic stirrer. The metal oxide Ga2O3 generated during the stirring process can effectively reduce the surface tension and fluidity of the liquid metal. At the same time, the metal oxide can form strong hydrogen bonds with the polyvinyl alcohol film, thereby promoting the stable adhesion of the liquid metal. Then, the polymer substrate is placed in the liquid metal and stirred until both the inner and outer surfaces are adhered before being taken out, thus forming a stable liquid metal surface coating.

[0040] S5. Assemble a half-cell by attaching a polymer substrate with a liquid metal surface coating to a lithium sheet, and apply an electric current to deposit lithium in situ on the liquid metal surface.

[0041] Specifically, the current density for in-situ lithium deposition is 0.1 mA cm⁻¹. –2 ~ 2 mA cm –2 The capacity is 1 mAh cm –2 ~10 mAh cm –2 This current density and capacity range is conducive to the uniform nucleation and deposition of lithium, avoiding excessive current density and capacity, which can easily lead to dendrite formation and make it difficult to diffuse on the surface of liquid metal.

[0042] Preferably, the current density of the in-situ pre-deposited lithium is 0.5 mA cm⁻¹. –2 The capacity is 5 mAh cm –2 In-situ pre-deposition of lithium can alloy liquid lithium metal, providing more lithophile sites for subsequent lithium deposition.

[0043] This invention combines laser selective sintering (SSS) technology with three-dimensional electrode structure design to solve problems such as dendrite growth and volume expansion in lithium metal batteries, and is expected to develop a new generation of energy storage devices. 3D printing technology has a high degree of freedom in structural design, and can obtain electrodes with complex geometries with the help of computer graphics. Compared with the traditional electrode manufacturing process, the highly automated manufacturing process and convenient synthesis route reduce the manufacturing cost and time of commercial electrodes. At the same time, this invention also combines liquid metal transfer technology to improve the nucleation and deposition behavior of lithium through alloying, and further obtains lithium metal battery anodes with good lithium storage performance and cycle stability. This is of great significance to promoting the development of rechargeable lithium metal batteries.

[0044] The present invention will be further described below with reference to specific embodiments.

[0045] Example 1

[0046] The preparation of a liquid metal / polymer composite three-dimensional current collector includes the following steps:

[0047] (1) Mix thermoplastic polyurethane and fumed silica powder in a planetary ball mill at a mass ratio of 100:1 and rotate at a speed of 600 rpm for 3 minutes.

[0048] (2) The mixed powder was placed into a laser selective sintering (SSS) printing equipment for printing. The sintering temperature was set to 90 °C, the laser output power to 25 W, and the scanning speed to 2000 mm / s. The designed negative electrode structure model is a three-period minimal surface, and the printed part size is 40 mm × 25 mm × 2 mm.

[0049] (3) Add 10% melamine to water that is 9 times the total mass of the material, stir and dissolve at 70°C for 1 hour, then raise the temperature to 95°C, and add 90% polyvinyl alcohol 2499 particles while stirring until they are completely dissolved to obtain a mixed solution of polyvinyl alcohol and flame retardant.

[0050] (4) Immerse the polymer substrate of the molded part completely in the mixed solution of polyvinyl alcohol and flame retardant, stir until no more bubbles escape from the polymer substrate, then take it out and let it stand for 10 min, and then place it in an electric heating drying oven at 50 ℃ for 6 h.

[0051] (5) The room temperature gallium-based liquid metal was stirred and oxidized using a magnetic stirrer at a speed of 200 rpm for 8 hours. The gallium-based liquid metal was a gallium-indium eutectic alloy, in which the mass fraction of gallium was 75% and the mass fraction of indium was 25%.

[0052] (6) The polymer substrate dried by low-temperature plasma treatment was used. The process parameters were Ar atmosphere, power of 122 W, time of 5 min, and pressure of 10 Pa.

[0053] (7) The polymer substrate treated with low temperature plasma is quickly immersed in the oxidized liquid metal and stirred until the liquid metal adheres to both the inner and outer surfaces of the polymer substrate. Then it is taken out to obtain a stable liquid metal surface coating.

[0054] (8) Assemble a half-cell by attaching a polymer substrate with a liquid metal surface coating to a lithium sheet, and then charge it at 0.2 mA cm⁻¹. –2 In-situ deposition of current density 2 mAh cm –2 Lithium is transferred onto liquid metal to ultimately obtain a liquid metal / polymer composite three-dimensional current collector.

[0055] Example 2

[0056] The preparation of a liquid metal / polymer composite three-dimensional current collector includes the following steps:

[0057] (1) Mix thermoplastic polyurethane and polyethylene wax powder in a planetary ball mill at a mass ratio of 100:1 and rotate at a speed of 600 rpm for 3 minutes.

[0058] (2) The mixed powder was placed into a laser selective sintering (SSS) printing equipment for printing. The sintering temperature was set to 90 °C, the laser output power to 25 W, and the scanning speed to 2000 mm / s. The designed negative electrode structure model is a three-period minimal surface, and the printed part size is 40 mm × 25 mm × 2 mm.

[0059] (3) Add 20% melamine to water at 9 times the total mass of the material, stir and dissolve at 70°C for 1.5 hours, then raise the temperature to 95°C, and add 80% polyvinyl alcohol 2499 particles while stirring until they are completely dissolved to obtain a mixed solution of polyvinyl alcohol and flame retardant.

[0060] (4) Immerse the polymer substrate of the molded part completely in the mixed solution of polyvinyl alcohol and flame retardant, stir until no more bubbles escape from the polymer substrate, then take it out and let it stand for 10 min, and then place it in an electric heating drying oven at 50 ℃ for 5 h.

[0061] (5) The room temperature gallium-based liquid metal was stirred and oxidized using a magnetic stirrer at a speed of 200 rpm for 8 hours. The gallium-based liquid metal was a gallium-indium eutectic alloy, in which the mass fraction of gallium was 75% and the mass fraction of indium was 25%.

[0062] (6) The polymer substrate dried by low-temperature plasma treatment was used. The process parameters were Ar atmosphere, power of 122 W, time of 5 min, and pressure of 10 Pa.

[0063] (7) The polymer substrate treated with low temperature plasma is quickly immersed in the oxidized liquid metal and stirred until the liquid metal adheres to both the inner and outer surfaces of the polymer substrate. Then it is taken out to obtain a stable liquid metal surface coating.

[0064] (8) Assemble a half-cell by attaching a polymer substrate with a liquid metal surface coating to a lithium sheet, and then charge it at 0.5 mA cm⁻¹. –2 In-situ deposition of current density 5 mAh cm⁻¹ –2 Lithium is transferred onto liquid metal to ultimately obtain a liquid metal / polymer composite three-dimensional current collector.

[0065] Example 3

[0066] The preparation of a liquid metal / polymer composite three-dimensional current collector includes the following steps:

[0067] (1) Mix thermoplastic polyurethane and fumed silica in a planetary ball mill at a mass ratio of 100:1 and rotate at a speed of 600 rpm for 3 minutes.

[0068] (2) The mixed powder was placed into a laser selective sintering (SSS) printing equipment for printing. The sintering temperature was set to 90 °C, the laser output power to 25 W, and the scanning speed to 2000 mm / s. The designed negative electrode structure model is a three-period minimal surface, and the printed part size is 40 mm × 25 mm × 2 mm.

[0069] (3) Add 10% of ammonium polyphosphate to water at a volume of 9 times the total mass of the material, stir and dissolve at 98°C for 1 hour, then cool down to 95°C, and add 90% of polyvinyl alcohol 2099 particles while stirring until they are completely dissolved to obtain a mixed solution of polyvinyl alcohol and flame retardant.

[0070] (4) Immerse the polymer substrate of the molded part completely in the mixed solution of polyvinyl alcohol and flame retardant, stir until no more bubbles escape from the polymer substrate, then take it out and let it stand for 10 min, and then place it in an electric heating drying oven at 50 ℃ for 6 h.

[0071] (5) The room temperature gallium-based liquid metal was stirred and oxidized using a magnetic stirrer at a speed of 200 rpm for 2 hours. The gallium-based liquid metal was a gallium-indium eutectic alloy, in which the mass fraction of gallium was 80% and the mass fraction of indium was 20%.

[0072] (6) The polymer substrate dried by low-temperature plasma treatment is used. The process parameters are O2 atmosphere, power of 122 W, time of 2 min and pressure of 15 Pa.

[0073] (7) The polymer substrate treated with low temperature plasma is quickly immersed in the oxidized liquid metal and stirred until the liquid metal adheres to both the inner and outer surfaces of the polymer substrate. Then it is taken out to obtain a stable liquid metal surface coating.

[0074] (8) Assemble a half-cell by attaching a polymer substrate with a liquid metal surface coating to a lithium sheet, and then charge it at 0.2 mA cm⁻¹. –2 In-situ deposition of current density 2 mAh cm –2 Lithium is transferred onto liquid metal to ultimately obtain a liquid metal / polymer composite three-dimensional current collector.

[0075] Example 4

[0076] The preparation of a liquid metal / polymer composite three-dimensional current collector includes the following steps:

[0077] (1) Mix thermoplastic polyurethane and fumed silica in a planetary ball mill at a mass ratio of 100:1 and rotate at a speed of 600 rpm for 3 minutes.

[0078] (2) The mixed powder was placed into a laser selective sintering printing equipment for printing. The sintering temperature was set to 90 ℃, the laser output power to 25 W, and the scanning speed to 2000 mm / s. The designed negative electrode structure model is a three-period minimal surface, and the printed part size is 40 mm × 25 mm × 2 mm.

[0079] (3) Add 20% of ammonium polyphosphate to water at a volume of 9 times the total mass of the material, stir and dissolve at 98°C for 1.5 hours, then cool down to 95°C, and add 80% of polyvinyl alcohol 2099 particles while stirring until they are completely dissolved to obtain a mixed solution of polyvinyl alcohol and flame retardant.

[0080] (4) Immerse the polymer substrate of the molded part completely in the mixed solution of polyvinyl alcohol and flame retardant, stir until no more bubbles escape from the polymer substrate, then take it out and let it stand for 10 min, and then place it in an electric heating drying oven at 50 ℃ for 5 h.

[0081] (5) The room temperature gallium-based liquid metal was stirred and oxidized using a magnetic stirrer at a speed of 200 rpm for 2 hours. The gallium-based liquid metal was a gallium-indium-tin alloy, in which the mass fraction of gallium was 68.5%, the mass fraction of indium was 21.5%, and the mass fraction of tin was 10%.

[0082] (6) The polymer substrate dried by low-temperature plasma treatment is used. The process parameters are O2 atmosphere, power of 122 W, time of 2 min and pressure of 15 Pa.

[0083] (7) The polymer substrate treated with low temperature plasma is quickly immersed in the oxidized liquid metal and stirred until the liquid metal adheres to both the inner and outer surfaces of the polymer substrate. Then it is taken out to obtain a stable liquid metal surface coating.

[0084] (8) Assemble a half-cell by attaching a polymer substrate with a liquid metal surface coating to a lithium sheet, and then charge it at 0.5 mA cm⁻¹. –2 In-situ deposition of current density 5 mAh cm⁻¹ –2 Lithium is transferred onto liquid metal to ultimately obtain a liquid metal / polymer composite three-dimensional current collector.

[0085] Example 5

[0086] The preparation of a liquid metal / polymer composite three-dimensional current collector includes the following steps:

[0087] (1) Mix thermoplastic polyurethane and fumed silica powder in a planetary ball mill at a mass ratio of 98:1 and rotate at a speed of 600 rpm for 3 minutes.

[0088] (2) The mixed powder was placed into a laser selective sintering (SSS) printing equipment for printing. The sintering temperature was set to 90 °C, the laser output power to 25 W, and the scanning speed to 2000 mm / s. The designed negative electrode structure model is a three-period minimal surface, and the printed part size is 40 mm × 25 mm × 2 mm.

[0089] (3) Add 10% melamine to water that is 9 times the total mass of the material, stir and dissolve at 70°C for 1 hour, then raise the temperature to 95°C, and add 90% polyvinyl alcohol 2499 particles while stirring until they are completely dissolved to obtain a mixed solution of polyvinyl alcohol and flame retardant.

[0090] (4) Immerse the polymer substrate of the molded part completely in the mixed solution of polyvinyl alcohol and flame retardant, stir until no more bubbles escape from the polymer substrate, then take it out and let it stand for 10 min, and then place it in an electric heating drying oven at 50 ℃ for 6 h.

[0091] (5) The room temperature gallium-based liquid metal was stirred and oxidized using a magnetic stirrer at a speed of 200 rpm for 2 hours. The gallium-based liquid metal was a gallium-indium-tin alloy, in which the mass fraction of gallium was 68.5%, the mass fraction of indium was 21.5%, and the mass fraction of tin was 10%.

[0092] (6) The polymer substrate dried by low-temperature plasma treatment was used. The process parameters were Ar atmosphere, power of 122 W, time of 5 min, and pressure of 10 Pa.

[0093] (7) The polymer substrate treated with low temperature plasma is quickly immersed in the oxidized liquid metal and stirred until the liquid metal adheres to both the inner and outer surfaces of the polymer substrate. Then it is taken out to obtain a stable liquid metal surface coating.

[0094] (8) Assemble a half-cell by attaching a polymer substrate with a liquid metal surface coating to a lithium sheet, and then charge it at 0.5 mA cm⁻¹. –2 In-situ deposition of current density 2 mAh cm –2 Lithium is transferred onto liquid metal to ultimately obtain a liquid metal / polymer composite three-dimensional current collector.

[0095] Example 6

[0096] The preparation of a liquid metal / polymer composite three-dimensional current collector includes the following steps:

[0097] (1) Mix thermoplastic polyurethane and fumed silica powder in a planetary ball mill at a mass ratio of 99:1 and rotate at a speed of 600 rpm for 3 minutes.

[0098] (2) The mixed powder was placed into a laser selective sintering (SSS) printing equipment for printing. The sintering temperature was set to 90 °C, the laser output power to 25 W, and the scanning speed to 2000 mm / s. The designed negative electrode structure model is a three-period minimal surface, and the printed part size is 40 mm × 25 mm × 2 mm.

[0099] (3) Add 20% of ammonium polyphosphate to water at a volume of 9 times the total mass of the material, stir and dissolve at 98°C for 1.5 hours, then cool down to 95°C, and add 80% of polyvinyl alcohol 2099 particles while stirring until they are completely dissolved to obtain a mixed solution of polyvinyl alcohol and flame retardant.

[0100] (4) Immerse the polymer substrate of the molded part completely in the mixed solution of polyvinyl alcohol and flame retardant, stir until no more bubbles escape from the polymer substrate, then take it out and let it stand for 10 min, and then place it in an electric heating drying oven at 50 ℃ for 6 h.

[0101] (5) The room temperature gallium-based liquid metal was stirred and oxidized using a magnetic stirrer at a speed of 200 rpm for 8 hours. The gallium-based liquid metal was a gallium-indium eutectic alloy, in which the mass fraction of gallium was 75% and the mass fraction of indium was 25%.

[0102] (6) The polymer substrate dried by low-temperature plasma treatment was used. The process parameters were Ar atmosphere, power of 122 W, time of 5 min, and pressure of 10 Pa.

[0103] (7) The polymer substrate treated with low temperature plasma is quickly immersed in the oxidized liquid metal and stirred until the liquid metal adheres to both the inner and outer surfaces of the polymer substrate. Then it is taken out to obtain a stable liquid metal surface coating.

[0104] (8) Assemble a half-cell by attaching a polymer substrate with a liquid metal surface coating to a lithium sheet, and then charge it at 1 mA cm⁻¹. –2 In-situ deposition of current density 2 mAh cm –2 Lithium is transferred onto liquid metal to ultimately obtain a liquid metal / polymer composite three-dimensional current collector.

[0105] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A rapid preparation method for a liquid metal / polymer composite three-dimensional current collector, characterized in that, Includes the following steps: S1. Construct a three-dimensional model of the battery negative electrode. Using additive manufacturing technology, print a flexible polymer substrate based on the constructed three-dimensional model using composite powder. The composite powder includes polymer powder and rheology modifier powder. The polymer powder is thermoplastic polyurethane. The rheology modifier is at least one of fumed silica and polyethylene wax powder. The mass ratio of polymer powder to rheology modifier in the composite powder is 98:1 to 100:

1. S2. Wetting the polymer substrate: The polymer substrate is thoroughly wetted with a mixture of polyvinyl alcohol and flame retardant; the degree of polymerization of the polyvinyl alcohol used in the mixture is 500-2400, the degree of hydrolysis is 88%, the flame retardant is ammonium polyphosphate or melamine, the mass fraction of polyvinyl alcohol is 70-92%, and the mass fraction of the flame retardant is 8-30%. S3. Modify the surface of the polymer substrate by introducing hydroxyl and carboxyl polar groups; treat the surface of the polymer substrate using low-temperature plasma technology, wherein the treatment atmosphere of the low-temperature plasma technology is oxygen or argon. S4. Oxidize the liquid metal and transfer it to the surface of the polymer substrate; S5. Assemble a half-cell by attaching a polymer substrate with a liquid metal surface coating to a lithium sheet, and apply an electric current to deposit lithium in situ on the liquid metal surface.

2. The rapid preparation method of the liquid metal / polymer composite three-dimensional current collector as described in claim 1, characterized in that, In step S1, the additive manufacturing technology is laser selective sintering, fused deposition modeling, or photopolymer 3D printing.

3. The rapid preparation method of the liquid metal / polymer composite three-dimensional current collector as described in claim 1, characterized in that, In step S4, the liquid metal is a room temperature gallium-based liquid metal, including any one of gallium, gallium-indium alloy, and gallium-indium-tin alloy.

4. The rapid preparation method of the liquid metal / polymer composite three-dimensional current collector as described in claim 1, characterized in that, In step S5, the current density for in-situ lithium deposition is 0.1 mA cm⁻¹. –2 ~ 2 mA cm –2 The capacity is 1 mAh cm –2 ~ 10mAh cm –2 .

5. A liquid metal / polymer composite three-dimensional current collector, characterized in that, It is prepared by the rapid preparation method as described in any one of claims 1-4.

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