Negative electrode structure applied to an aluminum battery

Abstract

PURPOSE: To provide a negative electrode structure applied to an aluminum battery.SOLUTION: A negative electrode structure includes first and second metal layers. The first metal layer has first reduction capability; the second metal layer has second reduction capability; the second metal layer is arranged on the first metal layer; and the first reduction capability higher than the second reduction capability corrodes and dissolves the second metal layer in an aluminum battery.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a negative electrode structure, and more particularly to a negative electrode structure applied to an aluminum battery.

Background Art

[0002] An aluminum battery is an electrochemical energy storage device having a metal foil as a negative electrode, and has advantages such as preferable safety and low cost. Further, since the negative electrode of the aluminum battery electrochemically reacts with an electrolyte (for example, chloroaluminate ionic liquid) during the charge and discharge process, metal deposition, metal dissolution, etc. occur on the negative electrode.

Summary of the Invention

Problems to be Solved by the Invention

[0003] The mechanism of the discharge capacity depends on the rate of the metal dissolution reaction.

Means for Solving the Problems

[0004] The present invention provides a negative electrode structure applied to an aluminum battery that can effectively improve the rate of the metal dissolution reaction, thereby increasing the energy density of the aluminum battery.

[0005] The negative electrode structure applied to the aluminum battery of the present invention includes a first metal layer and a second metal layer. The first metal layer has a first reduction ability. The second metal layer has a second reduction ability. The second metal layer is disposed on the first metal layer, and since the first reduction ability is higher than the second reduction ability, the second metal layer corrodes and dissolves in the aluminum battery.

[0006] In one embodiment of the present invention, the reaction potential of the first metal layer in the chloroaluminate ionic liquid is at least 0.5 volts higher than the oxidation potential of the second metal layer.

[0007] In one embodiment of the present invention, the oxidation potential range of the first metal layer in the chloroaluminate ionic liquid is between 0.5 volts and 1 volt.

[0008] In one embodiment of the present invention, the oxidation potential range of the second metal layer in the chloroaluminate ionic liquid is between -0.1 volts and 0.1 volts.

[0009] In one embodiment of the present invention, the first metal layer contains zinc, copper, nickel, or titanium.

[0010] In one embodiment of the present invention, the second metal layer contains aluminum.

[0011] In one embodiment of the present invention, the thickness range of the first metal layer is between 10 micrometers (μm) and 100 μm.

[0012] In one embodiment of the present invention, the thickness range of the second metal layer is between 0.5 μm and 50 μm.

[0013] In one embodiment of the present invention, the first metal layer is in direct contact with the second metal layer.

[0014] In one embodiment of the present invention, electron transfer occurs at the contact surface between the first metal layer and the second metal layer.

Advantages of the Invention

[0015] As described above, the negative electrode structure applied to the aluminum battery of the present invention has a design of two metal layers stacked on top of each other. In this way, the galvanic corrosion mechanism can be used to effectively improve the rate of the metal dissolution reaction, thereby increasing the energy density of the aluminum battery.

[0016] To make it easier to understand the features and advantages of the present invention, the following specific embodiments will be described in detail in conjunction with the drawings.

Brief Description of the Drawings

[0017]

Figure 1

Figure 2

Figure 3

Figure 4

Modes for Carrying Out the Invention

[0018] To make the content of the present invention easier to understand, the following specific embodiments are provided as examples that can actually implement the present invention. For clarity, many practical details are described in the following description. However, it should be understood that the present invention should not be limited by practical details. In other words, in some embodiments of the present invention, practical details are not necessary.

[0019] The present invention will be described in more detail with reference to the drawings of the embodiments. However, since the present invention can be implemented in various forms, it should not be limited to the embodiments described here. The thickness, size, or magnitude of layers or regions in the drawings may be exaggerated for clarity. The same or similar reference numerals represent the same or similar elements, and will not be repeatedly described one by one in the following paragraphs.

[0020] Unless otherwise specified, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by those skilled in the art to which the present invention pertains.

[0021] Unless otherwise specified, the term "between" used herein to define a range of values is intended to cover the recited endpoint values and the ranges therebetween. For example, a size range between a first value and a second value means that the size range covers the first value, the second value, and any value between the first value and the second value.

[0022] FIG. 1 is a partial schematic view of a negative electrode structure applied to an aluminum battery according to one embodiment of the present invention. FIG. 2 is a partial schematic view of an electrochemical cell for measuring a metal reaction potential. FIG. 3 is a schematic view comparing the peak current results of aluminum dissolution in chloroaluminate ionic liquids of Examples and Comparative Examples. FIG. 4 is a schematic view showing the peak current results of aluminum dissolution in chloroaluminate ionic liquids of nickel foil and titanium foil.

[0023] Referring to FIG. 1, in the present embodiment, the negative electrode structure 100 applied to the aluminum battery 101 includes a first metal layer 110 and a second metal layer 120, and the second metal layer 120 is disposed on the first metal layer 110. Further, the first metal layer 110 has a first reduction ability, the second metal layer 120 has a second reduction ability, and since the first reduction ability is higher than the second reduction ability, the second metal layer 120 corrodes and dissolves in the aluminum battery 101. Therefore, the negative electrode structure 100 applied to the aluminum battery 101 of the present embodiment has a design of two metal layers stacked on each other. In this way, by utilizing the galvanic corrosion mechanism, the rate of the metal dissolution reaction can be effectively improved, and the energy density of the aluminum battery can be increased. Here, the reduction ability refers to the ability to obtain electrons. Therefore, a metal with a low reduction ability may easily lose electrons to be oxidized. In this way, at the contact surface between the first metal layer 110 and the second metal layer 120, electron transfer naturally occurs (as shown in FIG. 1, the second metal layer 120 is an electron (e -) is lost, and electrons move from the second metal layer 120 to the first metal layer 110, so the second metal layer 120 corrodes and dissolves, releasing metal ions). Here, the first metal layer 110 is in direct contact with the second metal layer 120.

[0024] Furthermore, in this embodiment, due to the material selection, the metal to be dissolved is used as the anode (i.e., the second metal layer 120), and the metal with high reducing ability is selected as the cathode (i.e., the first metal layer 110). Therefore, the second metal layer 120 corrodes and dissolves by the galvanic corrosion mechanism (the different reduction reactivities of the two metals form a potential difference. By comparison, the anode metal corrodes, while the cathode metal is less likely to corrode), thereby effectively improving the rate of the metal dissolution reaction of the negative electrode structure 100. The negative electrodes of other batteries (e.g., lithium batteries) do not undergo electrochemical reactions, so metal dissolution is not required. Instead, it is necessary to protect the electrodes from corrosion. Therefore, even if the negative electrodes of other batteries (e.g., lithium batteries) have a laminated structure of two metal layers, the reliability still decreases due to the galvanic corrosion mechanism. However, in this embodiment, with the above-described settings and mechanisms, the energy density of the aluminum battery 101 can be increased, thereby improving the performance of the aluminum battery 101.

[0025] It should be noted that the aluminum battery 101 in FIG. 1 schematically shows the negative electrode structure 100 for clarity and does not show the actual configuration inside the aluminum battery 101. Also, inside the aluminum battery 101, there is also the presence of an electrolyte (e.g., chloroaluminum ionic liquid, which may be l-ethyl-3-methylimidazole chloride (EMIC) or l-butyl-3-methylimidazole chloride (BMIC)).

[0026] In some embodiments, the oxidation potential of the first metal layer 110 in the chloroaluminum ionic liquid is at least 0.5 volts higher than the reaction potential of the second metal layer 120. The oxidation potential range of the first metal layer 110 in the chloroaluminum ionic liquid may be between 0.5 volts and 1 volt, and the reaction potential range of the second metal layer 120 in the chloroaluminum ionic liquid may be between -0.1 volts and 0.1 volts.

[0027] For example, the first metal layer 110 contains zinc, copper, nickel, or titanium, and the second metal layer 120 contains aluminum. The reduction ability is measured by the reaction potential and can be obtained by measuring the oxidation potential as in the present invention. The higher the oxidation potential of the metal layer, the lower the possibility that the metal itself is oxidized, so it is more likely to be reduced (high reduction ability). As shown in Table 1, when the oxidation potential of the titanium foil is about 0.8 volts (V) higher than that of the aluminum foil, it means that the titanium foil is more likely to recover than the aluminum foil. Since a contact corrosion mechanism is formed in the laminate, the aluminum foil is oxidized to release electrons and dissolve the aluminum foil. Therefore, due to the difference in the oxidation potential of different metal foils in the chloroaluminum ionic liquid, a metal with a high reduction ability is selected as the current collector. The metal to be dissolved (for example, aluminum) is deposited on the current collector metal foil (for example, zinc, copper, nickel, or titanium) having a high oxidation potential by electroplating. The contact corrosion reaction increases the dissolution rate and the dissolution amount of aluminum in the negative electrode structure 100, thereby enhancing the aluminum dissolution reaction in the negative electrode structure 100, but the present invention is not limited thereto. Table 1 shows the oxidation potentials of metal foils such as aluminum foil, zinc foil, copper foil, nickel foil, and titanium foil measured by Tafel extrapolation. The reaction potential can be obtained by the electrochemical cell shown in FIG. 2 (including the reference electrode 10, the auxiliary electrode 12, the working electrode 14 (test metal), and the electrolyte 20 (AlCl3 - EMIC)).

[0028]

Table 1

[0029] Furthermore, using a chloroaluminate ionic liquid (AlCl3 2 EMIC) having a surface with a current density of 50 mA / cm - a 1.5-μm-thick aluminum layer was coated on a 50-μm-thick metal (nickel, titanium) having a high reducing ability. Cyclic voltammetry was performed in a three-electrode electrochemical cell and measured at a scanning rate of 10 mV / s. The difference between a nickel foil-plated aluminum negative electrode with a total thickness of 51.5 μm in the electrolyte (Example 1), a titanium foil-plated aluminum negative electrode with a total thickness of 51.5 μm in the electrolyte (Example 2), and an aluminum foil with a total thickness of 50 μm (Comparative Example 1) was compared at the same scanning rate, and the detailed results are shown in Fig. 3. Also, based on the above analysis method, nickel foil and titanium foil were also measured. As shown in Fig. 4, it was found that no current of the aluminum dissolution reaction was generated in the same electrochemical window (located at the position of a current density of 0). Here, the potential on the X-axis in Figs. 3 and 4 was obtained by comparing with Al / Al 3+

[0030] From the results of Figs. 3 and 4, the following conclusions can be drawn. The peak current of aluminum dissolution in Example 1 and Example 2 increased by more than 300% compared with Comparative Example 1. That is, the nickel foil-plated aluminum negative electrode and the titanium foil-plated aluminum negative electrode can effectively increase the amount of the aluminum dissolution reaction and can also increase the aluminum dissolution rate at the same scanning rate. In this case, when the negative electrode is disposed in an aluminum battery, the energy density can be effectively increased. Comparing Fig. 3 and Fig. 4, the nickel foil-plated aluminum negative electrode and the titanium foil-plated aluminum negative electrode with a high amount and rate of the aluminum dissolution reaction are indeed affected by the galvanic corrosion mechanism, thereby improving the aluminum dissolution reactivity.

[0031] ​Currently, metallic aluminum foil is often used as the negative electrode of an aluminum battery. Metallic aluminum foil is prone to oxidation and can form dense alumina on its surface. In this way, AlCl4, which is originally expected to undergo an aluminum dissolution reaction during the discharge process, - By selectively corroding the oxide layer, the rate of the aluminum dissolution reaction is reduced and the amount of dissolved aluminum is decreased, so the energy density of the aluminum battery cannot be effectively increased. Therefore, the design of the present embodiment in which two metal layers are stacked on top of each other can increase the amount of dissolved aluminum before the formation of the oxide layer, thereby effectively increasing the energy density of the aluminum battery, but the present invention is not limited thereto.

[0032] In some embodiments, a chloroaluminate ionic liquid can be used to electroplate a metal with a lower reduction ability (e.g., aluminum) onto the surface of a metal with a higher reduction ability (e.g., zinc, copper, nickel, or titanium). In this way, the coating can be uniformly controlled, the process can be simplified, and mass production can be facilitated, but the present invention is not limited thereto. Here, there may be an appropriate electroplating mechanism corresponding to the selected ionic liquid, but it will not be repeatedly described here.

[0033] In some embodiments, the range of the thickness D1 of the first metal layer 110 is between 10 μm and 100 μm, and the range of the thickness D2 of the second metal layer 120 is between 0.5 μm and 50 μm, but the present invention is not limited thereto. The thickness D1 of the first metal layer 110 and the thickness D2 of the second metal layer 120 can be determined according to actual design requirements.

[0034] In the above content, the composition (e.g., positive electrode and / or separator) and configuration of the aluminum battery not otherwise described should be obtained by those of ordinary skill in the technical field of the present invention based on any content that covers the spirit and scope included in the appended claims, so it will not be repeatedly described here.

[0035] As described above, the negative electrode structure applied to the aluminum battery of the present invention has a design of two metal layers stacked on top of each other. In this way, the galvanic corrosion mechanism can be used to effectively improve the rate of the metal dissolution reaction, thereby increasing the energy density of the aluminum battery.

[0036] Although the present invention has been disclosed in the above embodiments, these embodiments are not intended to limit the present invention. Those skilled in the art can make some changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention should be defined by the appended claims.

Industrial Applicability

[0037] The negative electrode structure of the present invention can be applied to an aluminum battery.

Explanation of Reference Numerals

[0038] 10 Reference electrode 12 Auxiliary electrode 14 Working electrode 20 Electrolyte 101 Aluminum battery 100 Negative electrode structure 110 First metal layer 120 Second metal layer D1, D2 Thickness

Claims

1. A negative electrode structure applied to an aluminum battery, having a first reducing ability, a first metal layer which is a metal foil, having a second reducing ability, a second metal layer containing aluminum, and including, wherein the second metal layer is disposed on the first metal layer, and since the first reducing ability is higher than the second reducing ability, a negative electrode structure in which the second metal layer corrodes and dissolves in the aluminum battery.

2. The negative electrode structure according to claim 1, wherein a reaction potential of the first metal layer in an aluminum chloride ionic liquid is at least 0.5 volts higher than an oxidation potential of the second metal layer.

3. The negative electrode structure according to claim 1, wherein an oxidation potential range of the first metal layer in an aluminum chloride ionic liquid is between 0.5 volts and 1 volt.

4. The negative electrode structure according to claim 1, wherein an oxidation potential range of the second metal layer in an aluminum chloride ionic liquid is between -0.1 volts and 0.1 volts.

5. The negative electrode structure according to claim 1, wherein the first metal layer contains zinc, copper, nickel, or titanium.

6. The negative electrode structure according to claim 1, wherein a thickness range of the first metal layer is between 10 μm and 100 μm.

7. The negative electrode structure according to claim 1, wherein a thickness range of the second metal layer is between 0.5 μm and 50 μm.

8. The negative electrode structure according to claim 1, wherein the first metal layer is in direct contact with the second metal layer.

9. The negative electrode structure according to claim 1, wherein electron transfer occurs at a contact surface between the first metal layer and the second metal layer.

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