Negative porous current collector for low-temperature sodium-based liquid metal battery as well as preparation method and application of negative porous current collector

Abstract

The invention provides a negative porous current collector for a low-temperature sodium-based liquid metal battery and a preparation method and application of the negative porous current collector. The preparation method comprises the following steps: taking three-dimensional porous metal foam as a current collector matrix; and carrying out surface cleaning and inert atmosphere pretreatment on the current collector substrate, and assembling the pretreated negative electrode current collector and a liquid sodium negative electrode. By adopting the foam metal current collector, the cycle stability of the battery can be remarkably improved, the material consumption of the current collector is reduced, the preparation cost of the battery is reduced while the performance is guaranteed, and the balance between the performance and the economical efficiency is realized.

Description

Technical Field

[0001] This invention belongs to the field of electrochemical liquid metal battery technology, specifically relating to a porous current collector for a low-temperature sodium-based liquid metal battery, its preparation method, and its application. Background Technology

[0002] Electrochemical energy storage technology has gained widespread attention due to its high energy efficiency, scalability, and rapid response capabilities. Liquid metal batteries (LMBs), with their three-layer structure consisting of a liquid metal anode, a molten salt electrolyte, and a liquid metal cathode, exhibit unique advantages. These include self-healing capabilities, suppression of dendrite formation, long cycle life, and low cost, making LMBs highly suitable for grid-scale stationary energy storage.

[0003] Compared to room-temperature electrochemical systems, liquid metal batteries face a series of engineering and chemical disadvantages when operating at 300–500°C. Higher operating temperatures impose greater demands on insulation, sealing, and safety redundancy. Molten salts have a stronger corrosive and creep-inducing effect on the metal casing and seals, limiting material selection and increasing lifespan uncertainty. Most critically, the negative electrode active metals (lithium / sodium / potassium) in common molten salt systems exhibit high diffusivity, easily leading to self-discharge chains of dissolution, diffusion, and redeposition. They also form uncontrolled interfacial reactions with the current collector, ultimately resulting in active material loss, increased interfacial resistance, and decreased cycle efficiency. Therefore, effectively immobilizing lithium / sodium / potassium in a high-temperature molten salt environment, reducing their reactivity with the electrolyte and current collector, and cutting off dissolution and migration pathways are key bottlenecks determining the long-term stability and lifespan of the system. Summary of the Invention

[0004] 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.

[0005] In view of the problems existing in the above and / or prior art, the present invention is proposed.

[0006] Therefore, the purpose of this invention is to overcome the shortcomings of the prior art and provide a porous current collector for a low-temperature sodium-based liquid metal battery, its preparation method, and its application.

[0007] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a method for preparing a porous current collector for a low-temperature sodium-based liquid metal battery, comprising: using a three-dimensional porous metal foam as the current collector substrate; performing surface cleaning and inert atmosphere pretreatment on the current collector substrate; and assembling the pretreated negative electrode current collector with a liquid sodium negative electrode.

[0008] As a preferred embodiment of the preparation method described in this invention, the three-dimensional porous metal foam includes one of copper foam, molybdenum foam, nickel-tin foam, and nickel-copper foam.

[0009] As a preferred embodiment of the preparation method described in this invention, the porosity of the three-dimensional porous metal foam is 80%~95% and the average pore size is 200~800μm.

[0010] As a preferred embodiment of the preparation method described in this invention, the pretreatment includes ultrasonically cleaning the current collector substrate with ethanol and deionized water for 10-30 minutes to remove surface oil and impurities, and then drying it in a vacuum oven at 120-200°C for 2-4 hours and cooling it to room temperature.

[0011] As a preferred embodiment of the preparation method described in this invention, the assembly involves immersing the negative electrode current collector in molten liquid sodium for 5-15 minutes in an argon atmosphere.

[0012] Another objective of this invention is to overcome the shortcomings of the prior art and provide a porous current collector for a low-temperature sodium-based liquid metal battery prepared by a specific method.

[0013] As a preferred embodiment of the porous current collector for the negative electrode of the low-temperature sodium-based liquid metal battery described in this invention, it significantly suppresses lithium / sodium negative electrode dissolution and related self-discharge at 300–500°C.

[0014] Another objective of this invention is to overcome the shortcomings of the prior art and provide a liquid metal battery, the liquid metal battery comprising the above-mentioned low-temperature sodium-based liquid metal battery negative electrode porous current collector, molten salt electrolyte and liquid metal positive electrode.

[0015] In a preferred embodiment of the liquid metal battery described in this invention, the porous current collector of the negative electrode is connected to the negative electrode post of the battery casing through a conductive connector.

[0016] In a preferred embodiment of the liquid metal battery described in this invention, the positive electrode is connected to the positive electrode post of the battery casing via a molybdenum-based conductive connector.

[0017] In a preferred embodiment of the liquid metal battery described in this invention, the weld between the connector and the current collector is protected by an argon atmosphere.

[0018] Beneficial effects of this invention: This patent innovatively applies porous foam metals such as copper foam, molybdenum foam, nickel-copper foam, and nickel-tin foam alloys to the current collector design of liquid metal batteries. While ensuring high conductivity of the current collector, it significantly expands the interfacial contact area between the current collector and the liquid electrode, effectively reducing interfacial contact resistance, accelerating charge transfer between the electrode and the current collector, and reducing local overpolarization. Among these, molybdenum foam possesses excellent high-temperature resistance to molten salt corrosion, making it suitable for the high-temperature operating environment of liquid metal batteries and significantly extending the current collector's lifespan. Copper foam exhibits good interfacial compatibility with some liquid negative electrode metals (such as sodium and lithium), reducing side reactions between the current collector and the liquid electrode. Nickel-copper foam and nickel-tin foam alloys combine the performance advantages of both metals, retaining high conductivity while further enhancing high-temperature corrosion resistance and interfacial compatibility. Furthermore, the porous foam structure can accommodate the volume fluctuations of the liquid electrode during charging and discharging, avoiding the current collector from peeling off due to changes in electrode morphology. Compared with traditional compacted current collectors, the foam metal current collector used in this invention can significantly improve the cycle stability of the battery, while reducing the amount of current collector material used. This ensures performance while reducing battery manufacturing costs, achieving a balance between performance and economy. Attached Figure Description

[0019] 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 comparison chart of capacity-voltage curves for large-capacity batteries with different negative electrode current collectors according to the present invention.

[0020] Figure 2 This is a diagram showing the cyclic stability of the foamed molybdenum anode current collector of the present invention.

[0021] Figure 3 This is a diagram showing the cyclic stability of the foamed copper negative electrode current collector of the present invention.

[0022] Figure 4 This is a diagram showing the cyclic stability of the foamed nickel-tin negative electrode current collector of the present invention.

[0023] Figure 5 This diagram illustrates how the adsorption capacity of the current collector on the negative electrode directly affects the stability of the negative electrode side, as shown in Comparative Example 1 of this invention. 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 this invention are commercially available.

[0028] Example 1 The preparation and assembly of a foamed molybdenum anode current collector suitable for Na||Bi-Sn liquid metal batteries at 270~370℃ are carried out according to the following steps: (1) Select foamed molybdenum with suitable specifications as the negative electrode current collector substrate: the foamed molybdenum has a porosity of 85% and an average pore size of 300μm. It is cut into circular pieces with a diameter of 50mm and a thickness of 5mm to ensure that the size is compatible with the stainless steel shell (inner diameter 56mm) of the battery and the graphite crucible. (2) Under the protection of inert gas (Ar), the surface of the foamed molybdenum was cleaned: the circular foamed molybdenum was placed in ethanol and deionized water in sequence, and ultrasonically cleaned for 15 min and 20 min respectively to remove the oil and dust impurities attached to the surface; it was vacuum dried at 150℃ for 3 h to completely remove the residual moisture in the pores, and then transferred to the glove box for later use after cooling to room temperature. (3) In an inert gas (Ar) glove box, prepare liquid sodium and complete sodium adsorption of the foam molybdenum current collector: Weigh 2.7g of metallic sodium particles and put them into a quartz container. Place the container on a temperature-controlled heating platform and heat it to 100~110℃ (above the melting point of sodium, 98℃). After the metallic sodium has completely melted into liquid, slowly immerse the pretreated foam nickel into the liquid sodium and keep it immersed for 5~8 minutes. During this period, gently shake the container to ensure that the liquid sodium fully wets the pore structure of the foam molybdenum. (4) Under the protection of inert gas (Ar), the composite negative electrode and the battery body are assembled: First, Bi metal and Sn metal with a molar ratio of 7:3 are melted and heated at 400°C for 40 minutes as the alloy positive electrode and placed in a graphite crucible. Then, the dry mixed salt is heated to 320~330°C (higher than the electrolyte melting point of 313°C) to melt it. The molten salt is slowly poured into the graphite crucible. When the molten salt is in a flowing state and has not solidified, the foam molybdenum composite negative electrode with adsorbed liquid sodium is gently placed into the molten salt to ensure that the foam molybdenum is completely submerged in the molten salt and has no direct contact with the alloy positive electrode.

[0029] (5) Under the protection of inert gas, the battery casing is encapsulated: the appropriate stainless steel top cover is fastened onto the casing containing the composite negative electrode, LiCl-LiBr-KBr electrolyte and positive electrode, and the position of the top cover is adjusted so that the electrode post and the foamed nickel current collector are precisely connected through the nickel-based conductive connector; then the joint between the casing and the top cover is sealed by laser welding technology, and Ar gas is continuously introduced during the welding process to prevent oxidation of the welding area; (6) Verification of negative electrode current collector performance: Place the packaged battery in the test furnace, heat it to 400℃ (within the working range of 350~450℃) and maintain a constant temperature, and connect the battery test system.

[0030] Example 2 A method for preparing and assembling a foamed copper anode current collector suitable for Na||Bi-Sn liquid metal batteries at 270~370℃, characterized by the following steps: (1) Select foamed copper with suitable specifications as the negative electrode current collector substrate: the foamed copper has a porosity of 85% and an average pore size of 400μm. It is cut into circular pieces with a diameter of 50mm and a thickness of 5mm to ensure that the size is compatible with the battery stainless steel shell (inner diameter 56mm) and the graphite crucible. (2) Under the protection of inert gas (Ar), the surface of the foamed copper is cleaned: the circular foamed copper is placed in ethanol and deionized water in sequence, and ultrasonically cleaned for 15 min and 20 min respectively to remove the oil and dust impurities attached to the surface; vacuum dry at 150℃ for 3 h to completely remove the residual moisture in the pores, and transfer it to the glove box for later use after cooling to room temperature. (3) In an inert gas (Ar) glove box, prepare liquid sodium and complete sodium adsorption of the foamed copper current collector: Weigh 2.7g of metallic sodium particles and put them into a quartz container. Place the container on a temperature-controlled heating platform and heat it to 100~110℃ (above the melting point of sodium, 98℃). After the metallic sodium has completely melted into liquid, slowly immerse the pretreated foamed copper into the liquid sodium and keep it immersed for 5~8 minutes. During this period, gently shake the container to ensure that the liquid sodium fully wets the pore structure of the foamed copper. (4) Under the protection of inert gas (Ar), the composite negative electrode and the battery body are assembled: First, Bi metal and Sn metal with a molar ratio of 7:3 are melted and heated at 400°C for 40 minutes as the alloy positive electrode and placed in a graphite crucible. Then, the dry mixed salt is heated to 320~330°C (higher than the electrolyte melting point of 313°C) to melt it. The LiCl-LiBr-KBr molten salt is slowly poured into the graphite crucible. When the molten salt is in a flowing state and has not solidified, the foamed copper composite negative electrode with adsorbed liquid sodium is gently placed into the molten salt to ensure that the foamed copper is completely submerged in the molten salt and has no direct contact with the alloy positive electrode.

[0031] (5) Under the protection of inert gas, the battery casing is encapsulated: the appropriate stainless steel top cover is fastened to the casing containing the composite negative electrode, electrolyte and positive electrode, and the position of the top cover is adjusted so that the electrode post and the foamed copper current collector are precisely connected through the nickel-based conductive connector; then the joint between the casing and the top cover is sealed by laser welding technology, and Ar gas is continuously introduced during the welding process to prevent oxidation of the welding area. (6) Verification of negative electrode current collector performance: Place the packaged battery in the test furnace, heat it to 400℃ (within the working range of 350~450℃) and maintain a constant temperature, and connect the battery test system.

[0032] Example 3 A foamed nickel-tin anode current collector for Na||Bi-Sn liquid metal batteries suitable for 270~370℃ is prepared and assembled, characterized by the following steps: (1) Select a suitable foamed nickel-tin as the negative electrode current collector substrate: the foamed nickel-tin has a porosity of 85% and an average pore size of 350μm. It is cut into circular pieces with a diameter of 50mm and a thickness of 5mm to ensure that the size is compatible with the battery stainless steel shell (inner diameter 56mm) and the graphite crucible. (2) Under the protection of inert gas (Ar), the surface of the foamed nickel-tin was cleaned: the circular foamed nickel-tin was placed in ethanol and deionized water in sequence, and ultrasonically cleaned for 15 min and 20 min respectively to remove the oil and dust impurities attached to the surface; it was vacuum dried at 150℃ for 3 h to completely remove the residual moisture in the pores, and then transferred to the glove box for later use after cooling to room temperature. (3) In an inert gas (Ar) glove box, prepare liquid sodium and complete sodium adsorption of the foamed nickel-tin current collector: Weigh 2.7g of metallic sodium particles and put them into a quartz container. Place the container on a temperature-controlled heating platform and heat it to 100~110℃ (above the melting point of sodium, 98℃). After the metallic sodium has completely melted into liquid, slowly immerse the pretreated foamed nickel-tin into the liquid sodium and keep it immersed for 5~8 minutes. During this period, gently shake the container to ensure that the liquid sodium fully wets the pore structure of the foamed copper. (4) Under the protection of inert gas (Ar), the composite negative electrode and the battery body are assembled: First, Bi metal and Sn metal with a molar ratio of 7:3 are melted and heated at 400°C for 40 minutes as the alloy positive electrode and placed in a graphite crucible. Then, the dry mixed salt is heated to 320~330°C (higher than the electrolyte melting point of 313°C) to melt it. The molten salt is slowly poured into the graphite crucible. When the molten salt is in a flowing state and has not solidified, the foamed nickel-tin composite negative electrode with adsorbed liquid sodium is gently placed into the molten salt to ensure that the foamed nickel-tin is completely submerged in the molten salt and has no direct contact with the alloy positive electrode.

[0033] (5) Under the protection of inert gas, the battery casing is encapsulated: the appropriate stainless steel top cover is fastened to the casing containing the composite negative electrode, LiCl-LiBr-KBr-CsCl electrolyte and positive electrode, and the position of the top cover is adjusted so that the electrode post and the foamed nickel-tin current collector are precisely connected through the nickel-based conductive connector; then the joint between the casing and the top cover is sealed by laser welding technology, and Ar gas is continuously introduced during the welding process to prevent oxidation of the welding area; (6) Verification of negative electrode current collector performance: Place the packaged battery in the test furnace, heat it to 400℃ (within the working range of 350~450℃) and maintain a constant temperature, and connect the battery test system.

[0034] Figure 1 It can be seen that all three different negative electrode current collectors can operate at a capacity of over 10Ah. Figure 2 The battery in the test operated stably for 120 cycles with a coulombic efficiency of 98%. Figure 3 The battery in the test cell operated stably for 80 cycles with a coulombic efficiency of 99%. Figure 4 The battery in this model operates stably for 135 cycles with a coulombic efficiency of 99%, making it the best performing of the three.

[0035] Comparative Example 1 The difference between this comparative example and Example 3 is that the foamed nickel-tin in step (1) is replaced with foamed iron-nickel, and the remaining steps are the same as in Example 1.

[0036] A current collector with a nickel content of 50% and a pore density of 50 PPI was used as the negative electrode, and Bi7Sn3 was used as the positive electrode. Stability tests were conducted by charging at 0.35 C and discharging at 0.35 C.

[0037] The results are as follows Figure 5 As shown, the current collector's adsorption capacity on the negative electrode directly affects the stability of the negative electrode side.

[0038] 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 preparing a porous current collector for a low-temperature sodium-based liquid metal battery, characterized in that: include, A three-dimensional porous metal foam was used as the current collector substrate. The current collector substrate was surface cleaned and pretreated with an inert atmosphere. The pretreated negative electrode current collector was then assembled with a liquid sodium negative electrode. The three-dimensional porous metal foam includes one of the following: copper foam, molybdenum foam, nickel-tin foam, and nickel-copper foam.

2. The preparation method according to claim 1, characterized in that: The porosity of the three-dimensional porous metal foam is 80%~95%, and the average pore size is 200~800μm.

3. The preparation method according to claim 1, characterized in that: The pretreatment includes ultrasonically cleaning the current collector substrate with ethanol and deionized water for 10-30 minutes to remove surface oil and impurities, then drying it in a vacuum oven at 120-200°C for 2-4 hours and cooling it to room temperature.

4. The preparation method according to claim 1, characterized in that: The assembly involves immersing the negative electrode current collector in molten liquid sodium for 5-15 minutes in an argon atmosphere.

5. The porous current collector for a low-temperature sodium-based liquid metal battery prepared by the preparation method according to claims 1 to 4.

6. The porous current collector for a low-temperature sodium-based liquid metal battery as described in claim 5, characterized in that: Significantly suppresses lithium / sodium anode dissolution and related self-discharge at 300–500℃.

7. A liquid metal battery, characterized in that: The liquid metal battery includes the low-temperature sodium-based liquid metal battery negative electrode porous current collector, molten salt electrolyte, and liquid metal positive electrode as described in claim 5.

8. The liquid metal battery as described in claim 7, characterized in that: The porous current collector of the negative electrode is connected to the negative electrode post of the battery casing through a conductive connector.

9. The liquid metal battery as described in claim 7, characterized in that: The positive electrode is connected to the positive terminal of the battery casing via a molybdenum-based conductive connector.

10. The liquid metal battery as described in claim 7, characterized in that: The weld between the connector and the current collector is protected by an argon atmosphere.

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