Method for improving discharge performance of liquid metal battery

Abstract

The invention belongs to the technical field of energy storage batteries, and particularly relates to a method for improving the discharge performance of a liquid metal battery, liquid metal comprises a shell and a negative electrode, electrolyte and a positive electrode which are sealed in the shell and are sequentially arranged from top to bottom, the liquid metal battery is heated to the working temperature of 300-600 DEG C, and the discharge performance of the liquid metal battery is improved. Then cooling the top of the shell, and / or heating the bottom of the shell, so that the temperature range of the top of the shell is 10-60 DEG C lower than that of the bottom of the shell, and a certain temperature gradient is formed at the top and the bottom of the liquid metal battery to excite heat convection in a positive electrode, so that concentration polarization is reduced; the discharge performance is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of energy storage batteries, and more specifically, relates to a method for improving the discharge performance of a liquid metal battery. Background Art

[0002] Liquid metal batteries use liquid metal as positive and negative electrodes and inorganic molten salt as electrolyte. In order to meet the melting points of both the electrode and the electrolyte, they need to operate at high temperatures (300-600°C). Due to immiscibility, the three layers of liquid are stratified according to density differences. Liquid metal batteries have the advantages of long cycle life, intrinsic safety, low cost, and easy recycling, making them a highly competitive candidate in the field of large-scale static energy storage.

[0003] Liquid metal batteries have large concentration polarization during the discharge process. Taking Li||Bi batteries as an example, during the discharge process, the low-density metal Li migrates from the negative electrode to the positive electrode through the molten salt electrolyte, deposits at the positive electrode-electrolyte interface and gradually diffuses downward, resulting in a stable density stratification in the positive electrode with a low density in the upper layer and a high density in the lower layer, which inhibits the flow in the positive electrode, so that the transmission of Li in the positive electrode can basically only rely on diffusion, resulting in a large concentration polarization and reducing the discharge voltage. Therefore, promoting the transmission of lithium in the positive electrode during the discharge process and increasing the discharge voltage are issues that need to be solved urgently. Summary of the invention

[0004] In view of the defects of the prior art, the present invention provides a method for improving the discharge performance of a liquid metal battery, the purpose of which is to reduce the concentration polarization in the positive electrode during the discharge process and increase the discharge voltage of the liquid metal battery.

[0005] Provided is a method for improving the discharge performance of a liquid metal battery. The liquid metal battery comprises a shell and a negative electrode, an electrolyte and a positive electrode which are sealed in the shell and arranged in sequence from top to bottom. The liquid metal battery is heated to a working temperature of 300 to 600° C., and then the top of the shell is cooled, and / or the bottom of the shell is heated, so that the temperature of the top of the shell is lower than the temperature of the bottom of the shell by 10 to 60° C.

[0006] Preferably, cooling the top of the shell is performed by natural cooling, wherein the natural cooling is achieved by taking away heat through air convection.

[0007] Preferably, cooling the top of the shell is performed by using a cooling electric device, and the cooling electric device is selected from an electric fan and an air cooler.

[0008] Preferably, cooling the top of the shell is specifically performed by reducing the thickness of the thermal insulation layer on the upper surface of the negative electrode.

[0009] Preferably, heating the bottom of the shell is specifically heating the bottom of the shell, and the heating method is resistance wire or induction heating.

[0010] Preferably, the negative electrode is selected from one or more of lithium, sodium, potassium, magnesium and calcium.

[0011] Preferably, the electrolyte is a metal halide salt mixture, preferably one or more of LiF, LiCl, LiBr, LiI, KCl, KBr, KI, NaCl, NaBr, NaI, CsCl, CsBr, CsI.

[0012] Preferably, the positive electrode is selected from one or more of bismuth, antimony, tellurium, tin and lead.

[0013] In general, the above technical solution conceived by the present invention has the following technical advantages compared with the prior art:

[0014] The present invention maintains the temperature difference between the upper and lower surfaces of the liquid metal battery at 10 to 60K, stimulates thermal convection inside the battery, promotes material transfer through flow, and increases the discharge voltage of the battery. When the upper and lower surface temperatures of the liquid metal battery are equal, the flow in the positive electrode is almost completely suppressed. When the temperature of the upper surface is 10 to 60K lower than that of the lower surface, the thermal convection stimulated by the temperature gradient can break the stable density stratification and form a flow of a certain intensity in the positive electrode. Due to the existence of thermal convection, the concentration polarization in the positive electrode is significantly reduced, and the discharge voltage of the battery is also increased. This method has the advantages of being simple, easy to implement, low cost, and obvious effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 The internal flow field distribution diagram of the liquid metal battery of Example 1 and Comparative Example 1.

[0016] Figure 2 The lithium concentration distribution diagram in the positive electrode of the liquid metal battery of Example 1 and Comparative Example 1.

[0017] Figure 3 The discharge voltage test of the liquid metal battery of Example 1 and Comparative Example 1. DETAILED DESCRIPTION

[0018] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0019] Example 1

[0020] A method for improving the discharge performance of a liquid metal battery is carried out according to the following steps:

[0021] (1) A liquid metal battery with a negative electrode of metallic lithium, an electrolyte of LiCl-KCl eutectic salt, a positive electrode of metallic bismuth, and an operating temperature range of 450°C is placed in a resistance wire heating furnace. The heating time is controlled to ensure that the temperature of the upper surface of the battery is 20°C lower than that of the lower surface by bottom heating.

[0022] (2) After the temperature distribution stabilizes, connect the battery tester to discharge.

[0023] Example 2

[0024] (1) A liquid metal battery with a negative electrode of sodium metal, an electrolyte of LiCl-NaI eutectic salt, a positive electrode of antimony metal, and an operating temperature range of 600°C is used. An electric fan is used to blow and cool the top of the liquid metal battery, and the top heat dissipation method is used to ensure that the temperature of the upper surface of the battery is 15°C lower than that of the lower surface.

[0025] (2) After the temperature distribution stabilizes, connect the battery tester to discharge.

[0026] Example 3

[0027] (1) A liquid metal battery with a negative electrode of sodium metal, an electrolyte of LiCl-NaBr eutectic salt, a positive electrode of antimony metal, and an operating temperature range of 500°C is placed in the air for natural cooling, and the top heat dissipation method is used to ensure that the temperature of the upper surface of the battery is 10°C lower than that of the lower surface.

[0028] (2) After the temperature distribution stabilizes, connect the battery tester to discharge.

[0029] Example 4

[0030] A method for improving the discharge performance of a liquid metal battery is carried out according to the following steps:

[0031] (1) A liquid metal battery with a negative electrode of metallic lithium, an electrolyte of LiCl-KCl eutectic salt, a positive electrode of metallic bismuth, and an operating temperature range of 450°C is placed in a resistance wire heating furnace, and bottom heating is used to ensure that the temperature of the upper surface of the battery is 60°C lower than that of the lower surface.

[0032] (2) After the temperature distribution stabilizes, connect the battery tester to discharge.

[0033] Comparative Example 1

[0034] (1) A liquid metal battery, the negative electrode is metallic lithium, the electrolyte is LiCl-KCl eutectic salt, the positive electrode is metallic bismuth, the operating temperature range is 450°C, and the temperature of the upper surface of the battery is equal to the temperature of the lower surface.

[0035] (2) After the temperature distribution stabilizes, connect the battery tester to discharge.

[0036] Figure 1 The internal flow field distribution diagram of the liquid metal battery of Example 1 and Comparative Example 1. When the temperatures of the upper and lower surfaces of the liquid metal battery are equal, there is almost no flow in the positive electrode, and only self-driven thermal convection exists in the electrolyte; when the temperature of the upper surface of the liquid metal battery is 20°C lower than that of the lower surface, driven by the temperature difference between the upper and lower surfaces, the stable density stratification is broken, and a certain degree of thermal convection is generated in the positive electrode, with the maximum flow rate reaching ~6mm / s.

[0037] Figure 2 The lithium concentration distribution diagram in the positive electrode of the liquid metal battery of Example 1 and Comparative Example 1. When the upper and lower surface temperatures are equal, the lithium concentration at the interface reaches 12.9 mol / L; when there is a temperature gradient between the upper and lower surfaces, with the help of thermal convection in the positive electrode, the interface lithium concentration is reduced to 11.8 mol / L, and the concentration distribution is more uniform, indicating that with the help of thermal convection, the transmission of lithium in the positive electrode has been significantly enhanced.

[0038] like Figure 3 The discharge voltage test of the liquid metal battery of Example 1 and Comparative Example 1 shows that when there is a temperature gradient between the upper and lower surfaces, the flow is stimulated in the positive electrode to promote material transfer, which can effectively increase the discharge voltage of the battery.

[0039] It will be easily understood by those skilled in the art that the above description is only 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 in the protection scope of the present invention.

Claims

1. A method for improving the discharge performance of a liquid metal battery, characterized in that: The liquid metal battery includes a shell and a negative electrode, an electrolyte and a positive electrode which are sealed in the shell and arranged in sequence from top to bottom. The liquid metal battery is heated to an operating temperature of 300 to 600° C., and then the top of the shell is cooled, and / or the bottom of the shell is heated, so that the top temperature of the shell is lower than the bottom temperature of the shell by 10 to 60° C.

2. A method for improving the discharge performance of a liquid metal battery according to claim 1, characterized in that: Specifically, cooling the top of the shell body is performed by natural cooling, wherein the natural cooling is achieved by taking away heat through air convection.

3. A method for improving the discharge performance of a liquid metal battery according to claim 1, characterized in that: The top of the shell is cooled by using a cooling electric device, wherein the cooling electric device is selected from an electric fan and an air cooler.

4. A method for improving the discharge performance of a liquid metal battery according to claim 1, characterized in that: The cooling of the top of the shell is specifically performed by reducing the thickness of the thermal insulation layer on the upper surface of the negative electrode.

5. The method for improving the discharge performance of a liquid metal battery according to claim 1, characterized in that: Heating the bottom of the shell specifically includes heating the bottom of the shell, and the heating method is resistance wire heating or induction heating.

6. A method for improving the discharge performance of a liquid metal battery according to claim 1, characterized in that: The negative electrode is selected from one or more of lithium, sodium, potassium, magnesium and calcium.

7. A method for improving the discharge performance of a liquid metal battery according to claim 1, characterized in that: The electrolyte is a metal halide salt mixture, preferably one or more of LiF, LiCl, LiBr, LiI, KCl, KBr, KI, NaCl, NaBr, NaI, CsCl, CsBr, and CsI.

8. The method for improving the discharge performance of a liquid metal battery according to claim 1, characterized in that: The positive electrode is selected from one or more of bismuth, antimony, tellurium, tin and lead.

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