Self-healing type liquid drop inhibiting negative electrode for liquid metal battery and preparation method of self-healing type liquid drop inhibiting negative electrode

Abstract

The invention discloses a self-healing liquid drop inhibition negative electrode for a liquid metal battery and a preparation method. The method comprises the following steps: immersing a porous conductive substrate into a polymer solution, carrying out ultrasonic-assisted permeation, heating and curing to obtain a dynamic bond modified substrate; preparing low-melting-point liquid metal, performing gradient degassing on the modified substrate, performing vacuum impregnation on the modified substrate in molten alloy at high temperature, and performing ultrasonic assistance and pressurized permeation; temporarily plugging a pore inlet of the substrate by using a plugging agent, depositing a conductive polymer coating on the surface of the substrate by using an electrochemical polymerization method, removing the plugging agent, and carrying out vacuum evaporation on liquid metal; and preheating the composite substrate, immersing into molten negative electrode metal, preserving heat and adsorbing to obtain a finished product. By constructing a three-layer synergistic structure of dynamic bond modification, liquid metal filling and surface limitation of a conductive network, a core technology path of binding force balance regulation and self-healing synergy is constructed, and formation of metal liquid drops is inhibited from the source; the method adapts to high-temperature working conditions of liquid metal batteries and is suitable for the field of large-scale energy storage.

Description

Technical Field

[0001] This invention relates to the field of liquid metal battery electrode technology, and particularly to a self-healing anti-droplet negative electrode for liquid metal batteries and its preparation method. It is applicable to liquid metal batteries that need to suppress the formation of metal droplets, ensure the amount of metal adsorption, and limit the surface of the conductive layer in a high-temperature molten salt electrolyte environment. Background Technology

[0002] Liquid metal batteries, with their advantages of high energy density, long cycle life, and low raw material cost, have become a core candidate technology for large-scale electrochemical energy storage. Their core structure typically consists of a liquid metal anode, a molten salt electrolyte, and a cathode. Different liquid metal battery systems vary in electrode material selection and operating temperature. Among them, the lithium-bismuth liquid metal battery, with its core structure of "nickel-iron foam adsorbed molten lithium (anode) - molten salt electrolyte - bismuth (cathode)", operates at a temperature of 450-550℃ and is one of the key research directions in the current field of liquid metal batteries.

[0003] However, existing liquid metal battery anodes (typically represented by lithium-bismuth systems) suffer from four major pain points in practical applications, severely restricting battery performance and safety:

[0004] (1) Metal gravity shedding and pore damage: Nickel-iron foam is usually designed with high porosity to ensure metal adsorption. However, during charging and discharging, the metal deposits in the pores are easily affected by gravity and fall off to form droplets. In addition, during the cycle, the foam skeleton will generate microcracks due to volume changes, which will lead to the destruction of the integrity of the pore structure and further aggravate metal shedding and capacity decay.

[0005] (2) Problems of uneven current and Lorentz force enhancement: The conductivity of molten salt electrolytes has natural spatial differences. The conductive network of traditional nickel-iron foam lacks uniformity design, resulting in excessively high local current density during charging and discharging, which triggers strong Lorentz forces. This force stretches and disperses the metal deposits in the pores, accelerates the formation of metal droplets, and may eventually cause short circuits in the metal bridges between electrodes.

[0006] (3) Metal-cathode interface tension mismatch problem: Taking the lithium-bismuth system as an example, the interface tension difference between lithium and bismuth is significant (lithium has low surface tension and bismuth has high surface tension). Similar problems of interface tension mismatch between electrode metal and cathode material are also common in other liquid metal systems, which makes it difficult for metal deposits to exist stably on the negative electrode surface. They are easy to detach from the substrate and diffuse towards the positive electrode, forming isolated droplets, which destroy the stability of the electrode-electrolyte interface and reduce the coulombic efficiency of the battery.

[0007] (4) Problems of conductive layer penetration and pore blockage: Existing conductive layer preparation mostly adopts immersion polymerization or spraying process. The conductive material can easily penetrate into the pores inside the nickel-iron foam through capillary action, blocking the metal deposition and ion transport channels, resulting in a decrease in metal adsorption and exacerbating the formation of metal droplets.

[0008] Existing solutions mostly adopt single-function modification strategies. Furthermore, existing lithium-ion battery dynamic bond technology is not resistant to high temperatures and has limited functionality. Liquid metal technology suffers from improper filling and poor compatibility. None of these solutions have a synergistic mechanism and cannot fundamentally regulate the balance of gravity, Lorentz force, and surface tension. Consequently, it is difficult to simultaneously achieve the core requirements of "suppressing metal droplets and ensuring high metal adsorption." This problem has not been effectively solved in various liquid metal battery systems.

[0009] Therefore, there is an urgent need to design a self-healing anode structure that takes into account anti-gravity adsorption, equalization of current to suppress Lorentz force, interfacial tension matching, and conductive layer surface limitation. This structure can solve the above pain points through multi-layer functional synergy and adapt to the high-temperature operating conditions and energy storage application requirements of liquid metal batteries (including but not limited to lithium bismuth systems). Summary of the Invention

[0010] To address the aforementioned technical problems, this invention provides a self-healing anti-droplet anode for liquid metal batteries and its preparation method. This invention utilizes a synergistic process mechanism of "adsorption-constraint-current equalization-surface limitation" to fundamentally regulate the balance of gravity, Lorentz force, and surface tension, effectively suppressing metal droplet formation while ensuring the amount of metal adsorbed necessary for normal battery operation.

[0011] In a first aspect, the present invention provides a method for preparing a self-healing anti-droplet negative electrode for liquid metal batteries, which is achieved by the following technical solution.

[0012] A method for preparing a self-healing anti-droplet negative electrode for liquid metal batteries includes the following steps:

[0013] S1. Substrate pretreatment: The porous conductive substrate is cleaned with organic solvent, the oxide layer is removed with acidic solution, rinsed and dried before use;

[0014] S2. Preparation of dynamic bond modified layer: Prepare a polymer solution containing dynamic reversible bonds, immerse the pretreated porous conductive substrate in the polymer solution, perform ultrasonic-assisted permeation, and then heat and cure under inert gas protection to remove ungrafted polymer and obtain the dynamic bond modified substrate.

[0015] S3. Positive electrode compatible liquid metal filling: Prepare low melting point liquid metal compatible with the target battery positive electrode material. After the modified substrate is degassed by gradient, it is vacuum impregnated with molten alloy at high temperature, and ultrasonic-assisted and pressure-driven infiltration is performed. After cooling in an inert gas atmosphere, excess metal on the surface is removed.

[0016] S4. Preparation of a surface-defined self-healing uniform conductive network: The inlet of the substrate pores is temporarily sealed with a removable plugging agent. A conductive polymer coating is deposited on the substrate surface by electrochemical polymerization. After removing the plugging agent, liquid metal of the same material as the filler layer is vacuum evaporated to form a composite conductive network.

[0017] S5. Metal adsorption: Under inert gas protection, the composite substrate is preheated and then immersed in molten negative electrode metal for heat preservation and adsorption. After removing excess metal, the product is obtained by cooling.

[0018] The liquid metal battery of the present invention includes, but is not limited to, lithium bismuth liquid metal battery, and can also be adapted to other liquid metal battery systems such as lithium-based, sodium-based, and potassium-based. When adapting to different systems, the type of dynamic bond polymer, the composition of the liquid metal filling layer, the conductive polymer material, and the process parameters can be adjusted.

[0019] Furthermore, in step S1, the conductive substrate includes one or more of nickel-iron foam, nickel-chromium foam, titanium-based porous material, and stainless steel porous mesh.

[0020] Furthermore, in step S2, the polymer containing dynamic reversible bonds is selected from one or a combination of polymers containing acylhydrazone bonds and polymers containing boron-oxygen bonds; the polymer has a thermal decomposition temperature ≥600℃, is resistant to molten salt corrosion, and does not chemically react with lithium. Its dynamic reversible bonds (acylhydrazone bonds, boron-oxygen bonds) can reversibly break and recombine at the battery operating temperature (400-600℃), possessing self-repairing capabilities. Specifically, the polymer containing acylhydrazone bonds is selected from polyacylhydrazone-ether sulfone; the polymer containing boron-oxygen bonds is selected from polyboronate-siloxane.

[0021] By adopting the above technical solution, the thermal decomposition temperature of polymers containing dynamic reversible bonds covers the operating temperature of corresponding liquid metal batteries (such as 450-550℃ for lithium bismuth systems), and they are resistant to molten salt corrosion. The dynamic reversible bonds can achieve reversible exchange at high temperatures.

[0022] Furthermore, in step S2, when preparing the lithium bismuth liquid metal battery, the concentration of the polymer solution containing acylhydrazone bonds is 5-20 wt%. The pretreated porous conductive substrate is immersed in the polymer solution, and the ultrasonic-assisted permeation time is 10-30 min with an ultrasonic power of 100-300 W. Under inert gas protection, the temperature is raised and cured using a gradient temperature program with a heating rate of 2-5℃ / min, a curing temperature of 120-200℃, and a holding time of 2-6 h. The polymer coating is grafted onto the inner wall of the substrate pores through solution permeation-temperature curing, and the coating thickness is controlled at 1-5 μm to avoid clogging the internal pores of the substrate and to ensure unobstructed metal adsorption and ion transport channels.

[0023] Furthermore, the solvent in the polymer solution containing acylhydrazone bonds is selected from one or more of N,N-dimethylformamide, dimethyl sulfoxide, and tetrahydrofuran.

[0024] By adopting the above technical solution, the polymer coating is grafted onto the inner wall of the substrate pores through solution penetration-heat curing. The coating thickness is controlled within a range that does not block the pores, ensuring unobstructed metal adsorption channels.

[0025] Furthermore, in step S3, when the liquid metal battery is a lithium bismuth liquid metal battery, the liquid metal is a gallium indium bismuth alloy containing 10-20 wt% bismuth element, and 0.1-0.3 wt% of modifying elements are added to the alloy. The modifying elements are selected from one or more of silver, antimony, and tin. After melting, impurities are removed by filtration.

[0026] Furthermore, in step S3, the gradient degassing procedure for the modified substrate is as follows: atmospheric pressure → 50-100 Pa, holding for 30-60 min → 1-10 Pa, holding for 60-120 min; high-temperature vacuum impregnation temperature is the melting point of liquid metal + 50-100℃, and the impregnation time is 60-180 min; ultrasonic auxiliary power is 200-400 W, and the ultrasonic time is 20-40 min; pressurized permeation pressure is 0.1-0.5 MPa, and the holding time is 30-60 min; the inert gas atmosphere cooling rate is 1-3℃ / min, and the continuity of the liquid metal filling layer is maintained during the cooling process to avoid cracking or peeling.

[0027] By adopting the above technical solution, the liquid metal filling process uses "gradient degassing-high temperature impregnation-ultrasonic assistance-pressurized infiltration-gradient cooling" to ensure that the liquid metal fills the pore and gap areas of the substrate and forms a continuous constraint network.

[0028] Furthermore, in step S4, the removable plugging agent is selected as paraffin emulsion. The removable plugging agent is applied by spraying and subsequently removed by heating or solvent cleaning.

[0029] Furthermore, in step S4, the conductive polymer includes one or more of polythiophene polymers, polypyrrole polymers, and polyaniline polymers; the conductive polymer has a thermal decomposition temperature ≥500℃, a conductivity ≥10 S / cm at the battery operating temperature, is resistant to molten salt corrosion, does not chemically react with lithium and liquid metal filling layers, and possesses dynamic self-healing properties. Specifically, the thiophene polymer is selected as poly(3,4-ethylenedioxythiophene); the polypyrrole polymer is selected as polypyrrole; and the polyaniline polymer is selected as polyaniline.

[0030] Furthermore, in step S4, the removable plugging agent is applied by spraying at a pressure of 0.2-0.5 MPa and a distance of 10-20 cm, resulting in a plugging agent coating thickness of 5-10 μm. Electrochemical polymerization employs a three-electrode system: a composite substrate as the working electrode, a platinum sheet as the counter electrode, and a silver / silver chloride electrode as the reference electrode. The concentration of conductive monomers in the polymerization solution is 0.1-0.5 mol / L, the electrolyte (LiCl) concentration is 0.5-1.0 mol / L, the current density is 1-5 mA / cm², and the energizing time is 10-30 min. The plugging agent is removed by heating at 200-300℃ or by solvent cleaning. Vacuum evaporation is performed at a vacuum level of 1-10 Pa, a evaporation temperature of liquid metal melting point +30-80℃, a evaporation time of 20-60 min, and a liquid metal evaporation thickness of 1-3 μm, filling only the gaps in the conductive coating and not penetrating the internal pores of the substrate.

[0031] By adopting the above technical solution, the composite conductive network is prepared by "surface polymer conductive layer + liquid metal evaporation composite". The liquid metal only fills the gaps in the conductive coating and does not enter the internal pores of the substrate.

[0032] Furthermore, in step S5, nitrogen or argon (purity ≥ 99.999%) is selected as the inert gas; the preheating temperature is consistent with the temperature of the molten negative electrode metal (e.g., 350-550℃ when the molten negative electrode is lithium), and the preheating holding time is 20-40 min; the holding adsorption time is 30-90 min (the temperature fluctuation range of molten lithium is ≤ ±10℃); the cooling adopts a gradient cooling method with a cooling rate of 1-4℃ / min. After cooling to room temperature, excess negative electrode metal on the surface is removed to ensure that the adsorption amount of negative electrode metal meets the requirements for battery cycle use (lithium adsorption amount ≥ 5 mg / cm²).

[0033] By adopting the above technical solution, metal adsorption is carried out under inert gas protection, the preheating temperature is the same as the molten metal temperature, and the heat preservation adsorption time ensures that the metal adsorption amount meets the requirements for normal battery operation.

[0034] All materials involved in the process steps of this invention possess high-temperature thermal stability and resistance to molten salt corrosion at the corresponding operating temperature of liquid metal batteries, and there is no risk of high-temperature failure.

[0035] Secondly, the present invention provides a method for preparing a self-healing anti-droplet negative electrode for liquid metal batteries, which is achieved by the following technical solution.

[0036] A self-healing anti-droplet negative electrode for liquid metal batteries prepared by the above preparation method.

[0037] Specifically, the droplet-suppressing negative electrode comprises, from the inside out, a dynamically bond-modified porous conductive substrate, a positive electrode-compatible liquid metal self-healing filling layer, and a surface-defined self-healing uniform conductive network. The three-layer structure works together to achieve droplet suppression and self-healing functions, ensuring the metal adsorption requirements. This negative electrode is suitable for various liquid metal batteries, including but not limited to lithium bismuth liquid metal batteries.

[0038] This application has the following beneficial effects.

[0039] 1. Significant droplet suppression effect: Through the synergistic process of "dynamic bond adsorption enhancement + high surface tension constraint of liquid metal + uniform conductive anti-Lorentz force", the force balance is controlled from the root, effectively suppressing the formation of metal droplets and solving the risk of battery short circuit. This effect can be stably achieved in lithium bismuth system and other liquid metal systems.

[0040] 2. Ensuring Metal Adsorption Requirements: Through the synergistic process of high-porosity substrate design, dynamic bond modification to enhance metal adhesion, and surface confinement of conductive layer to avoid pore blockage, the metal adsorption channels are ensured to be unobstructed, meeting the metal adsorption requirements for the normal operation of various liquid metal batteries.

[0041] 3. Synergistic self-healing function: Through the layered self-healing process design of dynamic bond modification layer, liquid metal filling layer and composite conductive network, pore damage, metal dispersion area and conductive defects are repaired respectively, which significantly improves the long-term cycle stability of battery and adapts to the long-cycle use requirements of different liquid metal batteries.

[0042] 4. Strong adaptability to high-temperature conditions: All materials selected in the preparation process have high-temperature thermal stability and resistance to molten salt corrosion. The parameters of each process step can be flexibly adjusted according to the working temperature of different liquid metal systems (such as lithium bismuth system 450-550℃), with no risk of high-temperature failure.

[0043] 5. Great industrialization potential: All preparation steps are based on existing mature equipment and process improvements, requiring no special experimental conditions, with strong process controllability, facilitating large-scale production and application, and adapting to the mass production needs of different liquid metal batteries.

[0044] 6. Multi-system adaptability: The core technical solution of this invention is not limited to the lithium bismuth liquid metal battery system. By adjusting the material selection and process parameters, it can be widely applied to various liquid metal batteries such as lithium-based, sodium-based, and potassium-based batteries, breaking through the system limitations of the existing technology.

[0045] 7. Simultaneous resolution of multiple pain points: This invention constructs a full-process synergistic preparation system of "adsorption-constraint-current equalization-surface limitation", which breaks through the limitations of existing single modification strategies and simultaneously solves the four core pain points commonly found in various liquid metal batteries: metal gravity shedding, uneven current, mismatch of interfacial tension, and penetration and blockage of conductive layer. Attached Figure Description

[0046] Figure 1 This is a flowchart of the preparation process of the present invention;

[0047] Figure 2 This is a schematic diagram of the distribution of various materials in the negative electrode of the present invention, wherein: 1. Dynamic bond modification layer; 2. Positive electrode compatible liquid metal filling layer; 3. Negative electrode metal; 4. Nickel-iron foam; 5. Surface-defined self-healing uniform conductive network. Detailed Implementation

[0048] The present invention will be further described below with reference to embodiments. Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods. Unless otherwise specified, the materials used in the preparation process in the following embodiments have not undergone further processing and are all commercially available.

[0049] 1. Core Design Concept

[0050] This invention is based on the core mechanism of liquid metal batteries, namely, "metal droplet formation originates from the imbalance of gravity, Lorentz force, and surface tension" (with the lithium droplet formation mechanism in the lithium-bismuth system as a typical example). It proposes a design concept of "self-healing force balance regulation + conductive layer surface confinement + high metal adsorption synergy," achieving the goal through the synergistic effect of three functional layers.

[0051] (1) Dynamic bond modification layer: enhances the adsorption capacity of metals (such as lithium) and self-repairs pore damage, and counteracts the effect of gravity on metal detachment;

[0052] (2) Liquid metal filling layer: High surface tension dominates the force balance, matches the interface characteristics of metal (such as lithium) and cathode (such as bismuth), and constrains the metal to maintain a continuous shape;

[0053] (3) Surface-defined conductive layer: deposited only on the surface of the foam skeleton, with uniform current distribution to weaken the Lorentz force and without clogging the pores;

[0054] The three elements work together to achieve an integrated "adsorption-constraint-flow equalization" system, while ensuring the amount of metal adsorption and self-healing function, thus inhibiting the formation of metal droplets from the root.

[0055] The design concept of this invention is not limited to the lithium-bismuth system. For other liquid metal batteries, the same technical effect can be achieved by adjusting the type of dynamic bond polymer, the composition of the liquid metal filling layer and the conductive layer material according to the interface characteristics between the negative electrode metal (such as sodium, potassium and so on) and the positive electrode material, the operating temperature and other parameters.

[0056] 2. Technical Solution Steps

[0057] 2.1 Substrate Pretreatment

[0058] Nickel-iron foam suitable for high-temperature operating conditions was selected as the substrate material. This substrate needs to have high porosity, high specific surface area, good conductivity, and mechanical strength to provide sufficient adsorption sites and structural support for metals (such as lithium). The pretreatment process includes: cutting the nickel-iron foam to the target size, ultrasonically cleaning it with organic solvents to remove surface oil, immersing it in an acidic solution to remove the surface oxide layer, rinsing it with deionized water until neutral, and then vacuum drying it for later use.

[0059] The choice of substrate material in this step is versatile. In addition to nickel-iron foam, other high-temperature resistant and corrosion-resistant porous conductive substrates can be used, depending on the working temperature and corrosion characteristics of different liquid metal systems.

[0060] 2.2 Preparation of Dynamic Bond Modification Layer

[0061] 2.2.1 Polymer preparation: Select aromatic monomers with thermal stability covering the operating temperature of the target liquid metal battery (e.g., 450-550℃ for lithium-bismuth system), resistance to molten salt corrosion, and no reaction with negative electrode metal (e.g., lithium), and prepare polymers containing dynamic reversible bonds (e.g., acylhydrazone bonds) through polymerization reaction. The polymers must have both a rigid main chain structure and dynamic repair function.

[0062] 2.2.2 Grafting modification: Prepare a polymer solution, immerse the pretreated nickel-iron foam in the solution, and promote the polymer to penetrate into the inner wall of the pores by means of ultrasonic assistance, etc. Then, gradually heat up and cure under inert gas protection to form a uniform coating of polymer on the inner wall of the pores, ensuring that the pores are not blocked;

[0063] 2.2.3 Post-treatment: After curing, remove the ungrafted free polymer and vacuum dry to obtain the dynamically bonded modified nickel-iron foam substrate.

[0064] For different liquid metal systems, the adsorption characteristics of different negative electrode metals and the battery operating temperature can be adapted by adjusting the dynamic bond type and main chain structure of the polymer.

[0065] 2.3 Bismuth-compatible liquid metal filling process (taking bismuth-compatible as an example)

[0066] 2.3.1 Liquid metal preparation: Select a low-melting-point alloy system (such as gallium-indium-bismuth alloy) that has good chemical compatibility with the target cathode material (such as bismuth in the lithium-bismuth system). The alloy should have a melting point lower than the battery operating temperature, be a low-viscosity liquid at high temperatures, and have a surface tension significantly higher than the gravity and Lorentz force of the anode metal (such as lithium). Add trace amounts of modifying elements to the alloy, melt it, filter it to remove impurities, and obtain a high-purity liquid metal raw material.

[0067] 2.3.2 Gradient degassing: The modified nickel-iron foam is placed in a vacuum impregnation device, and the gas in the foam pores is gradually removed by gradient pressure reduction to create unobstructed conditions for liquid metal filling;

[0068] 2.3.3 High-temperature filling: The vacuum-treated foam is immersed in molten liquid metal. Ultrasonic assistance is used to promote the penetration of liquid metal into the pores and gaps. At the same time, appropriate pressure is applied to enhance the filling effect, ensuring that the liquid metal only fills the pore and gap areas and does not occupy the core space of metal (such as lithium) deposition.

[0069] 2.3.4 Cooling and trimming: Gradually cool under an inert gas atmosphere to remove excess liquid metal from the surface and ensure that the liquid metal forms a continuous constraint network.

[0070] For non-lithium bismuth liquid metal battery systems, it is only necessary to adjust the alloy composition of the liquid metal filling layer to make it compatible with the corresponding cathode material and match the surface tension characteristics of the anode metal, while keeping the filling process universal.

[0071] 2.4 Fabrication of Surface-Defined Self-Healing Uniform Conductive Network

[0072] 2.4.1 Temporary pore sealing: Use a removable sealing agent (such as paraffin emulsion) to temporarily seal the foam pore inlets to prevent subsequent conductive materials from penetrating into the internal pores;

[0073] 2.4.2 Surface conductive layer polymerization: Prepare a conductive polymer monomer solution and electrolyte system, and deposit a conductive polymer coating on the surface of the foam skeleton using electrochemical polymerization and other methods. The conductive polymer must have high-temperature conductivity stability and dynamic self-healing ability.

[0074] 2.4.3 Removal of plugging agent: Temporary plugging agent is removed by means of heating decomposition or solvent cleaning to clear the pore inlet and ensure that the metal (such as lithium) adsorption and ion transport channels are unobstructed;

[0075] 2.4.4 Liquid metal composite: Liquid metal of the same material as the filler layer is deposited on the surface of the conductive polymer coating through vacuum evaporation or other methods to fill the tiny gaps in the conductive coating, complete the conductive path, and form a composite conductive network with both self-healing properties and uniform conductivity.

[0076] The conductive network fabrication process in this step is universal, and suitable high-temperature stable conductive polymers and liquid metal materials can be selected according to the working temperature of different liquid metal systems.

[0077] 2.5 Metal Adsorption (Taking Lithium Adsorption as an Example)

[0078] The composite foam anode prepared above is preheated to a set temperature under inert gas protection, and then immersed in molten metal (such as lithium) for heat preservation and adsorption to ensure that the metal is fully deposited in the foam pores. After adsorption is completed, excess metal on the surface is removed, and after cooling, a complete self-healing anti-droplet anode is obtained.

[0079] For other liquid metal systems, it is only necessary to adjust the preheating temperature, the type of molten metal, and the adsorption time to match the physicochemical properties of the corresponding negative electrode metal.

[0080] 3. Characteristics of the negative electrode structure obtained by this preparation method

[0081] The self-healing anti-droplet negative electrode obtained by the above preparation method comprises, from the inside out, a three-layer synergistic structure consisting of a dynamically bonded modified nickel-iron foam substrate, a positive electrode compatible liquid metal self-healing filling layer, and a surface-defined self-healing uniform conductive network. Each layer achieves the following synergistic characteristics through process design:

[0082] Dynamic bond modification layer: The adsorption effect of the polymer coating improves the adhesion stability of metals (such as lithium), and the dynamic reversible bonds enable self-repair of pore damage and counteract lithium detachment caused by gravity.

[0083] Liquid metal filling layer: It is liquid at high temperature, which can fill the gaps and achieve droplet fusion and self-healing. Its high surface tension dominates the force balance and constrains lithium to maintain a continuous shape.

[0084] Surface-defined conductive network: deposited only on the foam surface, without blocking internal pores, uniform current distribution to weaken Lorentz force, and self-healing of conductive defects through the dynamic properties of conductive materials.

[0085] The negative electrode structure of this invention has good system adaptability. By adjusting the composition of each layer of materials, it can meet the usage requirements of different liquid metal batteries. The lithium bismuth system is only one typical application form.

[0086] This specific implementation uses a lithium-bismuth liquid metal battery as an example. In practical applications, the following can be adjusted according to parameters such as the type of negative electrode metal, the characteristics of the positive electrode material, and the operating temperature of the target liquid metal battery system:

[0087] 1. The type and synthesis parameters of the dynamic bond polymer are selected to ensure that it does not react with the negative electrode metal and is resistant to corrosion by the corresponding molten salt.

[0088] 2. The alloy composition of the liquid metal filler layer ensures its compatibility with the positive electrode material and its surface tension is adapted to the negative electrode metal;

[0089] 3. The types of conductive polymers and polymerization parameters, the temperature and time of the metal adsorption step, and other process parameters; all adjustments do not deviate from the core technical concept of this invention and are all within the protection scope of this invention.

[0090] The embodiments described herein are preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Therefore, all equivalent changes made in accordance with the structure, shape, and principle of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing a self-healing anti-droplet negative electrode for liquid metal batteries, characterized in that: Includes the following steps: S1. Substrate pretreatment: The porous conductive substrate is cleaned with organic solvent, the oxide layer is removed with acidic solution, rinsed and dried before use; S2. Preparation of dynamic bond modified layer: Prepare a polymer solution containing dynamic reversible bonds, immerse the pretreated porous conductive substrate in the polymer solution, perform ultrasonic-assisted permeation, and then heat and cure under inert gas protection to remove ungrafted polymer and obtain the dynamic bond modified substrate. S3. Positive electrode compatible liquid metal filling: Prepare low melting point liquid metal compatible with the target battery positive electrode material. After the modified substrate is degassed by gradient, it is vacuum impregnated with molten alloy at high temperature, and ultrasonic-assisted and pressure-driven infiltration is performed. After cooling in an inert gas atmosphere, excess metal on the surface is removed. S4. Preparation of a surface-defined self-healing uniform conductive network: The inlet of the substrate pores is temporarily sealed with a removable plugging agent. A conductive polymer coating is deposited on the substrate surface by electrochemical polymerization. After removing the plugging agent, liquid metal of the same material as the filler layer is vacuum evaporated to form a composite conductive network. S5. Metal adsorption: Under inert gas protection, the composite substrate is preheated and then immersed in molten negative electrode metal for heat preservation and adsorption. After removing excess metal, the product is obtained by cooling.

2. The method for preparing a self-healing anti-droplet negative electrode for liquid metal batteries according to claim 1, characterized in that: In step S1, the conductive substrate includes one or more of nickel-iron foam, nickel-chromium foam, titanium-based porous material, and stainless steel porous mesh.

3. The method for preparing a self-healing anti-droplet negative electrode for liquid metal batteries according to claim 1, characterized in that: In step S2, the polymer containing dynamic reversible bonds is selected from one or a combination of two of the following: polymers containing acylhydrazone bonds and polymers containing boron-oxygen bonds.

4. The method for preparing a self-healing anti-droplet negative electrode for liquid metal batteries according to claim 1, characterized in that: In step S2, when preparing the lithium bismuth liquid metal battery, the concentration of the polymer solution containing acylhydrazone bonds is 5-20 wt%. The pretreated porous conductive substrate is immersed in the polymer solution, and the ultrasonic-assisted permeation time is 10-30 min with an ultrasonic power of 100-300 W. The curing is carried out under inert gas protection using a gradient heating program with a heating rate of 2-5℃ / min, a curing temperature of 120-200℃, and a holding time of 2-6 h.

5. The method for preparing a self-healing anti-droplet negative electrode for liquid metal batteries according to claim 1, characterized in that: In step S3, when the liquid metal battery is a lithium bismuth liquid metal battery, the liquid metal is a gallium indium bismuth alloy containing 10-20 wt% bismuth element, and 0.1-0.3 wt% of modifying elements are added to the alloy. The modifying elements are selected from one or more of silver, antimony, and tin. After melting, impurities are removed by filtration.

6. The method for preparing a self-healing anti-droplet negative electrode for liquid metal batteries according to claim 1, characterized in that: In step S3, the gradient degassing procedure for the modified substrate is as follows: atmospheric pressure → 50-100 Pa, holding for 30-60 min → 1-10 Pa, holding for 60-120 min; high-temperature vacuum impregnation temperature is the melting point of liquid metal + 50-100℃, and the impregnation time is 60-180 min; ultrasonic auxiliary power is 200-400 W, and the ultrasonic time is 20-40 min; pressurized permeation pressure is 0.1-0.5 MPa, and the holding time is 30-60 min; the inert gas atmosphere cooling rate is 1-3℃ / min.

7. The method for preparing a self-healing anti-droplet negative electrode for liquid metal batteries according to claim 1, characterized in that: In step S4, the conductive polymer includes one or more of polythiophene polymers, polypyrrole polymers, and polyaniline polymers.

8. The method for preparing a self-healing anti-droplet negative electrode for liquid metal batteries according to claim 1, characterized in that: In step S4, the removable plugging agent is applied by spraying at a pressure of 0.2-0.5 MPa and a distance of 10-20 cm, resulting in a plugging agent coating thickness of 5-10 μm. Electrochemical polymerization employs a three-electrode system: a composite substrate as the working electrode, a platinum sheet as the counter electrode, and a silver / silver chloride electrode as the reference electrode. The concentration of conductive monomers in the polymerization solution is 0.1-0.5 mol / L, the electrolyte concentration is 0.5-1.0 mol / L, the current density is 1-5 mA / cm², and the energizing time is 10-30 min. The plugging agent is removed by heating at 200-300℃ or by solvent cleaning. Vacuum evaporation is performed at a vacuum level of 1-10 Pa, a evaporation temperature of +30-80℃ (the melting point of the liquid metal), a evaporation time of 20-60 min, and a liquid metal coating thickness of 1-3 μm.

9. The method for preparing a self-healing anti-droplet negative electrode for liquid metal batteries according to claim 1, characterized in that: In step S5, nitrogen or argon is used as the inert gas; the preheating temperature is the same as the temperature of the molten negative electrode metal, and the preheating holding time is 20-40 min; the holding adsorption time is 30-90 min; the cooling adopts a gradient cooling method, and the cooling rate is 1-4℃ / min.

10. A self-healing anti-droplet negative electrode for liquid metal batteries prepared by any one of the preparation methods described in claims 1-9.

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