A method for improving the discharge performance of a liquid metal battery

Abstract

The application belongs to the technical field of energy storage batteries, and more particularly relates to a method for improving the discharging performance of a liquid metal battery, which comprises a shell and a negative electrode, an electrolyte and a positive electrode which are sequentially arranged from top to bottom in the shell and are sealed in the shell, the liquid metal battery is heated to a working temperature of 300-600 DEG C, then the top of the shell is cooled and / or the bottom of the shell is heated, the temperature of the top of the shell is lower than the temperature of the bottom of the shell by 10-60 DEG C, a certain temperature gradient is formed at the top and the bottom of the liquid metal battery, heat convection in the positive electrode is excited, the concentration polarization is reduced, and the discharging performance is improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of energy storage batteries, and more particularly relates to a method for improving the discharging performance of a liquid metal battery. BACKGROUND

[0002] The liquid metal battery uses liquid metal as the positive and negative electrodes and inorganic molten salt as the electrolyte. In order to meet the melting points of the electrodes and the electrolyte, the battery needs to be operated at a high temperature (300-600 DEG C). Due to immiscibility, three layers of liquid are stratified according to the density difference. The liquid metal battery has advantages such as long cycle life, intrinsic safety, low cost, and easy recycling, making it a highly competitive candidate in the field of large-scale static energy storage.

[0003] During the discharging process of the liquid metal battery, there is a large concentration polarization. Taking a Li||Bi battery as an example, during the discharging 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, so that a stable density stratification with small density in the upper layer and large density in the lower layer is formed in the positive electrode, the flow in the positive electrode is inhibited, and thus the transport of Li in the positive electrode can basically only rely on diffusion, resulting in a large concentration polarization and a reduced discharging voltage. Therefore, promoting the transport of lithium in the positive electrode during the discharging process and improving the discharging voltage are currently urgent problems to be solved. SUMMARY

[0004] In view of the defects of the prior art, the application provides a method for improving the discharging performance of a liquid metal battery, which aims to reduce the concentration polarization in the positive electrode during the discharging process and improve the discharging voltage of the liquid metal battery.

[0005] The application provides a method for improving the discharging performance of a liquid metal battery, the liquid metal battery comprising a shell and a negative electrode, an electrolyte and a positive electrode which are sequentially arranged from top to bottom and sealed in the shell, the method comprising the following steps: heating the liquid metal battery to an operating temperature of 300-600 DEG C, then cooling the top of the shell and / or heating the bottom of the shell, so that the temperature of the top of the shell is lower than the temperature of the bottom of the shell by 10-60 DEG C.

[0006] Preferably, the cooling of the top of the shell is specifically cooling by natural cooling, and the natural cooling is cooling by air convection.

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

[0008] Preferably, the cooling of the top of the shell is specifically reducing the thickness of the heat preservation layer on the upper surface of the negative electrode.

[0009] Preferably, the bottom of the shell is heated, in particular by means of a heating wire or an inductor.

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

[0013] Overall, the above technical solutions conceived by the present application compared with the prior art mainly have the following technical advantages:

[0014] The present application maintains the temperature difference between the upper and lower surfaces of the liquid metal battery at 10-60 K, excites the thermal convection inside the battery, promotes mass transfer through flow, and improves the discharge voltage of the battery. When the upper and lower surfaces of the liquid metal battery are at the same temperature, the flow in the positive electrode is almost completely suppressed. When the temperature of the upper surface is 10-60 K lower than that of the lower surface, the thermal convection excited by the temperature gradient can break the stable density stratification and form a certain intensity of flow 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 improved. This method has the advantages of simplicity, easy implementation, low cost, obvious effect, etc. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 The liquid metal battery internal flow field distribution diagram 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 application clearer, the present application will be further described in detail below in combination with the drawings and examples. It should be understood that the specific examples described herein are only used to explain the present application and do not limit the present application. In addition, the technical features involved in each embodiment of the present application 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, which is performed 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, and a positive electrode of metallic bismuth, and an operating temperature range of 450°C, is placed at the bottom of a resistance wire heating furnace, and the heating time is controlled, and a bottom heating method is used to ensure that the temperature of the upper surface of the battery is 20°C lower than that of the lower surface.

[0022] (2) After the temperature distribution stabilizes, a battery tester is connected to perform discharge.

[0023] Example 2

[0024] (1) A liquid metal battery with a negative electrode of metallic sodium, an electrolyte of LiCl-NaI eutectic salt, and a positive electrode of metallic antimony, and an operating temperature range of 600°C, is placed at the top and cooled by an electric fan, and a top cooling 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, a battery tester is connected to perform discharge.

[0026] Example 3

[0027] (1) A liquid metal battery with a negative electrode of metallic sodium, an electrolyte of LiCl-NaBr eutectic salt, and a positive electrode of metallic antimony, and an operating temperature range of 500°C, is placed in the air at the top and cooled naturally, and a top cooling 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, a battery tester is connected to perform discharge.

[0029] Example 4

[0030] A method for improving the discharge performance of a liquid metal battery, which is performed 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, and a positive electrode of metallic bismuth, and an operating temperature range of 450°C, is placed at the bottom of a resistance wire heating furnace, and a bottom heating method 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, a battery tester is connected to perform discharge.

[0033] Comparative Example 1

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

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

[0036] Figure 1 For the internal flow field distribution diagram of the liquid metal battery of Example 1 and Comparative Example 1, when the upper and lower surface temperatures 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 upper surface temperature of the liquid metal battery is 20℃ lower than the lower surface temperature, under the driving of 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 a maximum flow rate of ~ 6mm / s.

[0037] Figure 2 For 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 is 12.9mol / L; and when there is a temperature gradient between the upper and lower surfaces, the lithium concentration at the interface is reduced to 11.8mol / L with the help of thermal convection in the positive electrode, and the concentration distribution is more uniform, indicating that the transport of lithium in the positive electrode is significantly enhanced with the help of thermal convection.

[0038] As Figure 3 For the discharge voltage test of the liquid metal battery of Example 1 and Comparative Example 1, when there is a temperature gradient between the upper and lower surfaces, the flow in the positive electrode is excited to promote mass transfer, which can effectively improve the discharge voltage of the battery.

[0039] Those skilled in the art will readily understand that the above description is only a preferred embodiment of the present application, and is not intended to limit the present application, and any modification, equivalent replacement and improvement made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

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

2. The method of claim 1, wherein, The cooling of the top of the shell is specifically natural cooling, and the natural cooling is achieved by air convection to take away heat.

3. The method of claim 1, wherein the method is performed in a liquid metal battery. The cooling of the top of the shell is specifically cooling by an electric cooling device, and the electric cooling device is selected from an electric fan and a cold air machine.

4. The method of claim 1, wherein the method is performed in a liquid metal battery. The cooling of the top of the shell is specifically reducing the thickness of the upper surface heat preservation layer of the negative electrode.

5. The method of claim 1, wherein the method is performed in a liquid metal battery. The heating of the bottom of the shell is specifically heating by an electric resistance wire or an electric inductor.

6. The method of claim 1, wherein the method is performed in a liquid metal battery. The negative electrode is selected from one or more of lithium, sodium, potassium, magnesium and calcium.

7. The method of claim 1, wherein the method is performed in a liquid metal battery. The electrolyte is a metal halide salt mixture.

8. The method of claim 7, wherein the method is performed in a liquid metal battery. The metal halide salt mixture is selected from one or more of LiF, LiCl, LiBr, LiI, KCl, KBr, KI, NaCl, NaBr, NaI, CsCl, CsBr and CsI.

9. The method of claim 1, wherein the method is performed in a liquid metal battery. The positive electrode is selected from one or more of bismuth, antimony, tellurium, tin and lead.

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