Positive electrode material for liquid metal battery, preparation method of positive electrode material and liquid metal battery

Abstract

The invention relates to the technical field of energy storage batteries, in particular to a positive electrode material for a liquid metal battery, a preparation method of the positive electrode material and the liquid metal battery, the positive electrode material is an alloy composed of tellurium and a transition metal element, the chemical formula of the alloy is TenX1-n, X is the transition metal element, n is the molar percentage of tellurium in the alloy, and n is the molar percentage of tellurium in the alloy. N is more than 50% and less than 100%, the transition metal element is one or more of Cr, Mn, Fe, Co, Zn, Cd, Rh and Pd, the solubility of Te in the molten salt electrolyte is effectively inhibited by adding the transition metal element, and the coulombic efficiency and cycling stability of the liquid metal battery are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of energy storage batteries, and in particular to a positive electrode material for a liquid metal battery and a preparation method thereof, and a liquid metal battery. Background Art

[0002] The efficient storage and utilization of renewable energy is an important support for the sustainable development of human society. Among the many energy storage technologies, electrochemical energy storage technology is gradually replacing traditional physical energy storage methods due to its high efficiency, flexibility, and environmental protection, becoming one of the key technologies for renewable energy consumption and large-scale grid-connected energy storage.

[0003] In recent years, liquid metal batteries have been widely studied as a new type of energy storage battery. Its characteristic is that at the working temperature, the battery presents a "three-liquid layer" configuration, namely the upper and lower layers of liquid metal (alloy) electrodes and the molten salt electrolyte in the middle layer. The highly self-healing properties of liquid metal (alloy) electrodes can avoid the problems of dendrite growth and structural collapse that occur in solid electrodes during the cycle process. Therefore, in theory, liquid metal batteries have an ultra-long cycle life (>15 years). At the same time, the battery uses inorganic molten salt as an electrolyte, so the battery has high safety characteristics and will not catch fire or explode under extreme conditions. In addition, the battery materials are widely available and inexpensive, the battery structure is simple, and the capacity is easy to enlarge and manufacture (>500Ah). In summary, liquid metal batteries are very suitable for large-scale power storage needs.

[0004] Among the selectable alkali metal and alkaline earth metal negative electrodes, lithium-based liquid metal batteries constructed based on metallic Li exhibit the best cycle stability and relatively high energy density (>400Wh / kg) due to the high electronegativity of Li and its low solubility in molten salt electrolytes. Based on lithium negative electrodes, multi-electrode materials with Sb, Bi, and Te as the main active materials have been fully expanded. Among them, Sb-based and Bi-based positive electrodes are the most mature and extensively studied and both have excellent electrochemical properties. However, the design of the bimetallic electrode pair makes it difficult for the battery operating voltage to break through 1V (the lithiation voltage of Sb is about 0.92V, and the lithiation voltage of Bi is only about 0.6V). Therefore, the volume energy density of liquid metal batteries is severely limited, especially for the practical application needs of modular design of future electrochemical energy storage power stations.

[0005] Tellurium (Te) has a lithiation voltage of up to 1.68 V (about 1.8 times that of Sb and 2.8 times that of Bi) and a lithiation capacity of about 644 Wh kg -1The theoretical specific energy of Te is considered to be a highly competitive high-voltage and high-specific-energy cathode material for liquid metal batteries. However, there are still huge challenges in achieving stable and efficient operation of Te-based liquid metals. On the one hand, the high solubility of Te and lithium polytelluride in molten salts leads to severe self-discharge and shuttle effect of the battery, low coulombic efficiency and poor cycle stability. On the other hand, the low conductivity of Te (2×10 2 S m-1) makes the cathode Te utilization rate less than 60%.

[0006] Prior art CN107482209B discloses a positive electrode material for liquid and semi-liquid metal batteries, the positive electrode material comprising metal Te or Te alloy formed by Te and one or more single substances of Sn, Sb, Pb, and Bi, and the battery has a voltage of up to about 1.5 and 1.7 V. In 2018, the article "Tellurium-tin based electrodes enabling liquid metal batteries for high specific energy storage applications" published in the journal Energy Storage Materials reported Li||Te-Sn liquid metal energy storage battery. The alloying of Sn and Te increased the conductivity of the Te electrode by two orders of magnitude, and explained the inhibitory effect of the inert Sn metal on the dissolution of the electrode Te. The battery's initial efficiency was 99%, but during the subsequent 70 cycles of operation, the coulombic efficiency gradually decayed to below 90%, making it difficult to operate stably for a long time. Prior art CN114171808B discloses a high energy density liquid metal battery and its preparation method. The positive electrode material is a Te-based alloy formed by metal Te and one of Cu, Ag, and Au, which further improves the electrode conductivity and inhibits the dissolution of Te. The battery has a current density of 200 mA cm -2 When the discharge voltage is 1.55V, the coulombic efficiency is 94.5%, the capacity utilization rate is 90.7%, and the energy density is 409kWh kg -1 Both methods have achieved the improvement of the conductivity of the Te electrode and the suppression of Te dissolution, and the coulombic efficiency and stability of the battery have been improved. However, to achieve a high-voltage Te-based liquid metal battery with higher coulombic efficiency and positive electrode utilization, it is necessary not only to suppress the dissolution of Te, but also to solve the shuttle effect caused by the dissolution of the discharge product lithium telluride. Summary of the invention

[0007] In view of the defects of the prior art, the present invention provides a positive electrode material and a preparation method for a liquid metal battery, and a liquid metal battery, which solve the technical problems of low conductivity and high solubility of tellurium in molten salt in the prior art of tellurium-based positive electrode materials.

[0008] According to a first aspect of the present invention, a positive electrode material for a liquid metal battery is provided, wherein the positive electrode material is an alloy composed of tellurium and a transition metal element, and the composition of the alloy is Te n X 1-n , wherein X is a transition metal element, n is the molar percentage of tellurium in the alloy, n is greater than 50% and less than 100%, and the transition metal element is one or more of Cr, Mn, Fe, Co, Zn, Cd, Rh, and Pd.

[0009] According to another aspect of the present invention, a method for preparing the positive electrode material for a liquid metal battery is provided, wherein tellurium element and the transition metal element are mixed, placed in a crucible current collector, and heated under the protection of an inert gas after mixing to allow the tellurium element and the transition metal element to undergo a sufficient alloying reaction, and the positive electrode material is obtained after natural cooling.

[0010] Preferably, the alloying reaction temperature is 650-750°C.

[0011] Preferably, the alloying reaction time is 3 to 5 minutes.

[0012] Preferably, the inert gas is selected from argon and helium.

[0013] Preferably, the material of the crucible current collector is graphite.

[0014] According to another aspect of the present invention, there is provided a liquid metal battery prepared by using the above-mentioned positive electrode material.

[0015] In general, the above technical solution conceived by the present invention has the following technical advantages compared with the prior art:

[0016] The present invention provides a high-voltage, high-coulomb efficiency Te-based liquid metal battery, which alloys metalloid Te and one or more transition metals such as Cr, Mn, Fe, Co, Zn, Cd, Rh, Pd, etc. as positive electrode materials, and the molar percentage of Te element is more than 50% and less than 100%. Since the conductivity of the alloy element is at least 3 orders of magnitude higher than that of the metalloid Te element, the alloying of the two can increase the electronic conductivity of the Te-based electrode by 2-3 orders of magnitude, thereby improving the utilization rate and electrochemical performance of Te. In addition, the solubility of Te in the molten salt electrolyte is effectively suppressed, and the coulomb efficiency and cycle stability of the battery are improved. More importantly, the metal Te compound formed during the discharge process can effectively promote the conversion process of lithium polytelluride and reduce the shuttle effect of lithium polytelluride, thereby achieving a higher coulomb efficiency (200mA cm- 2Liquid metal battery with coulombic efficiency greater than 97%, positive electrode utilization greater than 98%, and voltage greater than 1.4V at current density. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 Schematic diagram of the cross-sectional structure of the metal electrode energy storage battery of Examples 1 to 18;

[0018] Figure 2 is the charge and discharge performance curve of the metal electrode battery using Example 3;

[0019] Figure 3 The charge and discharge performance curve of the metal electrode energy storage battery using Example 2;

[0020] Figure 4 This is the cycle performance curve of the metal electrode energy storage battery using Example 2.

[0021] Among them, 1. a combined structural part 1 of a battery top cover and an electrode rod; 2. an insulating ceramic seal; 3. a battery lower shell; 4. a positive electrode current collector; 5. a negative electrode current collector with a negative electrode material absorbed therein; 6. a molten salt electrolyte; 7. a positive electrode material. DETAILED DESCRIPTION

[0022] 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.

[0023] Example 1

[0024] Cathode materialTe 95％ Co 5％ Preparation: Metal Te and transition metal Co are weighed according to the molar ratio and placed in a graphite crucible current collector. After mixing, they are heated at 650°C for 4 minutes under the protection of inert Ar gas to allow the metal Te and transition metal Co to undergo a sufficient alloying reaction. After natural cooling, Te 95％ Co 5％ Alloy electrode.

[0025] Manufacturing of Liquid Metal Batteries:

[0026] Containing Te 95％ Co 5％The graphite crucible with alloy electrode is placed inside the lower shell of the battery, and a certain amount of mixed molten salt electrolyte LiCl-KCl is added, the mass content of LiCl is 44.8%, and the mass content of KCl is 55.2wt%. The negative electrode collector storing the negative electrode metal material Li is connected to the battery top cover, and then assembled to the lower shell of the battery, and the top cover and the lower shell of the battery are welded and sealed to obtain the high-voltage liquid metal battery. It is then placed in a battery test furnace, and after heating to the required operating temperature of the battery, it is tested by heat preservation. The operating temperature of the battery is 580°C. The cross-sectional structure diagram of the specific liquid metal battery working system is shown as follows. Figure 1 shown.

[0027] Example 2

[0028] The difference from Example 1 is that the positive electrode material is Te 90 Co 10 .

[0029] Example 3

[0030] The difference from Example 1 is that the positive electrode material is Te 80 Co 20 .

[0031] Example 4

[0032] The difference from Example 1 is that the positive electrode material is Te 70 Co 30 .

[0033] Example 5

[0034] The difference from Example 1 is that the positive electrode material is Te 60 Co 40 .

[0035] Example 6

[0036] The difference from Example 1 is that the positive electrode material is Te 95 Mn5.

[0037] Example 7

[0038] The difference from Example 1 is that the positive electrode material is Te 90 Co 10 .

[0039] Example 8

[0040] The difference from Example 1 is that the positive electrode material is Te 80 Mn 20 .

[0041] Example 9

[0042] The difference from Example 1 is that the positive electrode material is Te 90 Cr 10 .

[0043] Example 10

[0044] The difference from Example 1 is that the positive electrode material is Te 80 Cr 20 .

[0045] Embodiment 11

[0046] The difference from Example 1 is that the positive electrode material is Te 90 Fe 10 .

[0047] Example 12

[0048] The difference from Example 1 is that the positive electrode material is Te 90 Zn 10 .

[0049] Embodiment 13

[0050] The difference from Example 1 is that the positive electrode material is Te 90 Fe5Mn5.

[0051] Embodiment 14

[0052] The difference from Example 1 is that the positive electrode material is Te 80 Fe 10 Mn 10 .

[0053] Embodiment 15

[0054] The difference from Example 1 is that the positive electrode material is Te 90 Cr5Mn5.

[0055] Example 16

[0056] The difference from Example 1 is that the positive electrode material is Te 80 Cr 10 Mn 10 .

[0057] Embodiment 17

[0058] The difference from Example 1 is that the positive electrode material is Te 80 Cr 10 Co 10 .

[0059] Embodiment 18

[0060] The difference from Example 1 is that the positive electrode material is Te 80 Fe 10 Co10 .

[0061] Comparative Example 1

[0062] Different from Example 1, the positive electrode material is Te.

[0063] Table 1 Performance test of liquid metal battery in Examples 1-18

[0064]

[0065]

[0066] Figure 2 The charge and discharge performance curve of the liquid metal energy storage battery of Example 2 of the present invention is shown in FIG. 1 , wherein the operating temperature is 580° C. and the current density is 200 mA cm -2 , discharge voltage 1.48V, Coulomb efficiency 97.8%, capacity utilization 98.1%.

[0067] Figure 3 The charge and discharge performance curve of the liquid metal energy storage battery of Example 18 of the present invention is shown in FIG. 1 , wherein the operating temperature is 600° C. and the current density is 200 mA cm -2 , discharge voltage 1.45V, Coulomb efficiency 97.2%, capacity utilization 98.2%.

[0068] Figure 4 The liquid metal battery of Example 2 of the present invention is used at 200 mA cm -2 The cycling performance under the current density is 270 cycles, and the battery capacity retention rate is still 99%.

[0069] The above test results show that when the positive electrode material is Te in comparative example 1, the coulombic efficiency is 80% and the capacity utilization rate is 55%. In the high-voltage positive electrode material of the liquid metal battery of the present invention, the alloying of transition metal and Te increases the electronic conductivity of the Te electrode, reduces the solubility of the active ingredient Te in the molten salt, and increases the utilization rate of Te to more than 98%; more importantly, it effectively promotes the conversion of lithium polytelluride, thereby inhibiting the dissolution of lithium polytelluride, and further increases the coulombic efficiency of the Te-based liquid metal battery to more than 97%.

[0070] 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 positive electrode material for a liquid metal battery, characterized in that: The positive electrode material is an alloy composed of tellurium and transition metal elements, and the composition of the alloy is Te n X 1-n , wherein X is a transition metal element, n is the molar percentage of tellurium in the alloy, n is greater than 50% and less than 100%, and the transition metal element is one or more of Cr, Mn, Fe, Co, Zn, Cd, Rh, and Pd.

2. The method for preparing a positive electrode material for a liquid metal battery according to claim 1, characterized in that: After the tellurium element and the transition metal element are mixed, they are placed in a crucible current collector, and after mixing, they are heated under the protection of an inert gas to allow the tellurium element and the transition metal element to undergo a sufficient alloying reaction, and after natural cooling, the positive electrode material is obtained.

3. The method for preparing a positive electrode material for a liquid metal battery according to claim 2, characterized in that: The alloying reaction temperature is 650-750°C.

4. The method for preparing a positive electrode material for a liquid metal battery according to claim 2, characterized in that: The alloying reaction time is 3 to 5 minutes.

5. The method for preparing a positive electrode material for a liquid metal battery according to claim 2, characterized in that: The inert gas is selected from argon and helium.

6. The method for preparing a positive electrode material for a liquid metal battery according to claim 2, characterized in that: The material of the crucible current collector is graphite.

7. A liquid metal battery prepared using the positive electrode material as claimed in claim 1.

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