Aluminum electrolytic capacitor and electrolyte thereof

Abstract

This invention provides an aluminum electrolytic capacitor and its electrolyte, which includes an electrolyte, an organic solvent, and functional additives, wherein the functional additives include metal oxides with a dielectric constant ≥7. The metal oxides with a dielectric constant ≥7 account for at most 3 wt% of the total weight of the electrolyte.

Description

Technical Field

[0001] This invention relates to an aluminum electrolytic capacitor and its electrolyte. Background Technology

[0002] Aluminum electrolytic capacitors are widely used in circuits due to their large capacitance, serving as power smoothers and decoupling agents. With the booming development of the electronics industry, electronic devices have increasingly higher requirements for adaptability to high and low temperature environments, thus necessitating electrolytes that are not easily degraded at high temperatures and can operate at low temperatures.

[0003] However, the electrolytes currently used in the industry often exhibit increased viscosity and decreased fluidity at low temperatures, leading to problems such as increased capacitor impedance and decreased electrolytic capacitor capacity.

[0004] Therefore, an electrolyte that remains stable at low temperatures is needed. Summary of the Invention

[0005] One embodiment of the present invention provides an electrolyte for an aluminum electrolytic capacitor, comprising: an electrolyte, an organic solvent, and a functional additive of a metal oxide with a dielectric constant ≥7. The metal oxide with a dielectric constant ≥7 accounts for at most 3 wt% of the total weight of the electrolyte.

[0006] An embodiment of the present invention provides an aluminum electrolytic capacitor, comprising: a core, including: an anode foil; a cathode foil; and a separating membrane located between the anode foil and the cathode foil; and an electrolyte for the aluminum electrolytic capacitor, wherein the core is immersed in the electrolyte.

[0007] To make the above features and advantages of the present invention more apparent and understandable, specific embodiments are described below in conjunction with the accompanying drawings. Attached Figure Description

[0008] Figure 1 This is a disassembly diagram of an aluminum electrolytic capacitor according to an embodiment of the present invention. Detailed Implementation

[0009] The following description provides detailed examples and accompanying drawings, but these examples are not intended to limit the scope of the invention. Furthermore, the drawings are for illustrative purposes only and are not drawn to their original dimensions. For ease of understanding, identical components will be labeled with the same symbols, and will not be described again in the following paragraphs.

[0010] The terms "includes," "includes," and "has" used in the text are all open-ended, meaning "includes but not limited to."

[0011] As used herein, “about,” “approximately,” or “substantially” includes the value mentioned and the average value within an acceptable range of deviations that can be determined by someone of ordinary skill in the art, taking into account limitations of the measurement system. For example, “about” may mean within one or more standard deviations of the value, or within ±30%, ±20%, ±10%, ±5%. Furthermore, the use of “about,” “approximately,” or “substantially” herein may be chosen to select a more acceptable range of deviations or standard deviations depending on their different natures, and a single standard deviation may not be applicable to all properties.

[0012] The terminology used herein is for illustrative purposes only and is not intended to limit the invention. Unless otherwise defined in the context, the singular form includes the plural form.

[0013] This invention proposes an electrolyte for an aluminum electrolytic capacitor and an aluminum electrolytic capacitor, which reduces the performance degradation of the capacitor caused by the poor fluidity of the electrolyte at low temperatures, such as capacitance decay and impedance increase.

[0014] First, please refer to Figure 1 This is a disassembly diagram of an aluminum electrolytic capacitor according to an embodiment of the present invention, wherein the aluminum electrolytic capacitor 10 includes a core 20, a container 30, an electrolyte 40, a positive / negative electrode 50, and a top cover 60.

[0015] The element 20 includes an anode foil 22, a cathode foil 24, a separating membrane 26, and a fixing material 28, wherein the anode foil 22 and the cathode foil 24 are as follows: Figure 1 The relative positions of the electrodes are not limited, as long as they are separated by the separator 26. The positive / negative electrodes 50 are connected to the anode foil 22 and the cathode foil 24 respectively to form lead-out portions, and the separator 26 can be, for example, electrolytic paper or other insulating material, but is not limited thereto. Finally, the anode foil 22, the cathode foil 24 and the separator 26 are fixed with a fixing material 28 such as electronic tape to form the element 20.

[0016] Next, the element 20, after being fixed as described above, is immersed in the electrolyte 40 in the container 30. This container can be, for example, an aluminum container, but is not limited to this. Then, the container 30 containing the electrolyte 40 and the element 50 is sealed with a cover 60 to obtain an aluminum electrolytic capacitor according to the present invention. This cover 60 can be made of a rubber seal material such as rubber resin, but is not limited to this. Figure 1 As shown, the top cover 60 allows the positive / negative electrode 50, which is in the form of a guide pin, to pass through and be exposed outside the top cover 60 to facilitate the application of voltage, but is not limited to this arrangement.

[0017] In some embodiments, the electrolyte 40 includes an electrolyte, an organic solvent, and a functional additive, wherein the functional additive includes a metal oxide with a dielectric constant ≥7.

[0018] In some embodiments, metal oxides with a dielectric constant ≥7 may include valve metal oxides with a dielectric constant ≥7 or ferroelectric materials with a dielectric constant ≥7.

[0019] In some embodiments, the metal oxide with a dielectric constant ≥7 may be selected from one or more of the group consisting of alumina, zirconium oxide, titanium dioxide, niobium oxide, barium titanate, tantalum oxide, chromium oxide, zinc oxide, technetium oxide, tungsten oxide, hafnium oxide, bismuth oxide, antimony oxide, and vanadium oxide.

[0020] In some embodiments, the dielectric constant of the metal oxide included in the functional additive may be between about 7 and 6000, for example, 7-5000.

[0021] The addition of metal oxides with a dielectric constant ≥ 7 to the electrolyte of aluminum electrolytic capacitors can overcome the performance degradation caused by poor electrolyte flow when aluminum electrolytic capacitors operate in low-temperature environments.

[0022] In some embodiments, the weight of the metal oxide with a dielectric constant ≥7 may account for up to 3 wt% of the total weight of the electrolyte, for example, 0.3 wt%-3 wt%, 0.3 wt%-2.5 wt%, 0.5 wt%-2.5 wt%, etc. If the amount of metal oxide with a dielectric constant ≥7 added is too small, it will be insufficient to prevent the electrolyte 40 of the aluminum electrolytic capacitor 10 from solidifying at low temperatures and resulting in poor fluidity. However, if the amount of metal oxide with a dielectric constant ≥7 added is too large, it may increase the viscosity of the electrolyte 40 of the aluminum electrolytic capacitor 10 and reduce its fluidity, leading to a decrease in the capacitance of the aluminum electrolytic capacitor 10, or even preventing the impregnation of elements.

[0023] In some embodiments, the electrolyte included in the electrolyte 40 may include ammonium azelaate, ammonium adipate, ammonium sebacate, ammonium dodecanoate, C6-C8 dicarboxylic acid with side chains, ammonium borate, or a combination thereof.

[0024] In some embodiments, the organic solvent included in the electrolyte 40 may include ethylene glycol, diethylene glycol, propylene glycol, 1,4-butanediol, glycerol, N,N-dimethylformamide, butyrolactone, diethylene glycol methyl ether, diethylene glycol monobutyl ether, valerate, or combinations thereof.

[0025] To make the foregoing contents and other objects, features and advantages of this disclosure more apparent and understandable, preferred embodiments are described below in detail with reference to the accompanying drawings.

[0026] First, it should be noted that the following embodiments and comparative examples will use electrolytes 40 with different compositions to manufacture their aluminum electrolytic capacitors 10 in the manner described below, as... Figure 1 The aluminum electrolytic capacitor 10 shown includes an element 20 immersed in an electrolyte 40 within a container 30. In the following embodiments and comparative examples, the element 20 is housed within a container 30 with a cylindrical aluminum shell having a bottom, and is immersed in an electrolyte 40 of different compositions. The open end of the aluminum shell container 30 is sealed with a rubber resin cap 60. After charging and aging, an aluminum electrolytic capacitor 10 (a pin-type aluminum electrolytic capacitor) with a rated voltage of 450 WV, a rated capacitance of 33 µF, and capacitor assembly dimensions of 18 mm in diameter and 20 mm in length is produced.

[0027] Experimental Group 1: Electrolyte Composition and Low-Temperature Performance Containing Functional Additives

[0028] As shown in Table 1 below, Examples 1-4 and Comparative Examples 1-3 used 6.5% ammonium 2-butyloctanoate and 3.5% ammonium sebacic acid as electrolytes, accounting for 6.5% of the total mass of the electrolyte. Alumina with a dielectric constant of 7-10 (0.5% of the total mass of the electrolyte) was used as the functional additive in Example 1; zirconium oxide with a dielectric constant of 25-29 (1% of the total mass of the electrolyte) was used as the functional additive in Example 2; titanium dioxide with a dielectric constant of 80-100 (1% of the total mass of the electrolyte) was used as the functional additive in Example 3; barium titanate with a dielectric constant of 4000-6000 (0.5% of the total mass of the electrolyte) was used as the functional additive in Example 4; and silicon dioxide with a dielectric constant of 3.5-4.5 (1% of the total mass of the electrolyte) was used as the functional additive in Comparative Example 2. Germanium dioxide with a dielectric constant of 5-6 was used as a functional additive in Comparative Example 3, while no functional additive was added in Comparative Example 1; ethylene glycol was used as the organic solvent in Examples 1-4 and Comparative Examples 1-3 to prepare different electrolyte compositions for Examples 1-4 and Comparative Examples 1-3.

[0029] In Examples 1-3, aluminum oxide, zirconium oxide, and titanium dioxide were added respectively, which are valve metal oxides with a dielectric constant ≥7, and in Example 4, barium titanate was added, which is a ferroelectric material oxide with a dielectric constant ≥7.

[0030] Then, Examples 1-4 and Comparative Examples 1-3 with different electrolyte compositions were placed in an environment of -25°C, and the state of these electrolytes was observed. The results are as follows:

[0031] [Table 1]

[0032]

[0033] As shown in Table 1 above, the electrolyte of Comparative Example 1 without functional additives solidified into a solid at -25°C, indicating that functional additives with a dielectric constant greater than zero have almost no fluidity at low temperatures below -25°C, which may lead to problems such as a rapid increase in capacitor impedance.

[0034] Second experimental group: Performance of electrolyte containing functional additives and aluminum electrolytic capacitors

[0035] This second experimental group used the electrolytes from Examples 1-4 and Comparative Examples 1-3 of the first experimental group to manufacture pin-type aluminum electrolytic capacitors with a rated voltage of 450 WV and a rated capacitance of 33 µF, according to the manufacturing method described in the first experimental group. The capacitance and electrical impedance of these aluminum electrolytic capacitors were measured at room temperature (20°C) and at a low temperature (-40°C), respectively. The results are shown in Table 2. The method for measuring the capacitance and impedance of the above-mentioned aluminum electrolytic capacitors can be found in JP2019-29598A.

[0036] In the -40℃ low-temperature characteristics field of Table 2 below, the capacitance and impedance measured at -40℃ have been converted into capacitance change rate and impedance ratio, respectively. The impedance ratio is impedance at -40℃ / impedance at 20℃, and the capacitance change rate is capacitance at -40℃ / capacitance at 20℃. The smaller the absolute value of capacitance change rate and impedance ratio, the smaller the change in capacitance and impedance at room temperature and low temperature, indicating that the aluminum electrolytic capacitor made of the electrolyte composition can still maintain its stability at low temperature.

[0037] [Table 2]

[0038]

[0039] As shown in Table 2 above, the aluminum electrolytic capacitor using the electrolyte of Comparative Example 3 showed a bulging bottom at room temperature of 20°C. This indicates that the composition of the electrolyte of Comparative Example 3 caused gas to be generated inside the capacitor. This unstable state is prone to danger, so the measurement of its capacitance was excluded. This phenomenon also shows that the composition of the electrolyte of Comparative Example 3 is not suitable for aluminum electrolytic capacitors.

[0040] Furthermore, the experimental results of capacitance change rate and impedance ratio in Table 2 show that the low-temperature characteristics of Examples 1-4 are better than those of Comparative Examples 1-2. Currently, the product specification in the aluminum electrolytic capacitor industry is an impedance ratio ≤ 6. However, the aluminum electrolytic capacitor made using the electrolyte of the present invention with added metal oxide functional additives with a dielectric constant ≥ 7 has an impedance ratio of less than 5 at -40°C, indicating that the aluminum electrolytic capacitor made with the electrolyte of the present invention can still operate stably at low temperatures.

[0041] Third Experimental Group: Electrolyte Composition and Capacitor Performance Containing Functional Additives

[0042] Example 5 and Comparative Example 4 of the third experimental group were prepared according to the method described in Example 1 of the first and second experimental groups, producing an electrolyte and a pin-type aluminum electrolytic capacitor with a rated voltage of 450 WV and a rated capacitance of 33 µF, except that the alumina content of the functional additive with a dielectric constant of 7-10 was increased from 0.5 wt% to 2.5 wt% and 5 wt%, respectively. However, the electrolyte prepared in Comparative Example 4 had too high a viscosity to impregnate elements, making it impossible to manufacture a capacitor.

[0043] In addition, Comparative Example 5 and Comparative Example 6 were also prepared according to the method described in Example 1 of the first and second experimental groups to produce electrolytes and needle-type aluminum electrolytic capacitors with a rated voltage of 450 WV and a rated capacitance of 33 µF. The only difference was the addition of 16 wt% of low freezing point liquids: diethylene glycol butyl ether with a freezing point of -68°C and γ-butyrolactone with a freezing point of -43°C, respectively, to replace alumina as functional additives.

[0044] Then, for the electrolyte and aluminum electrolytic capacitor prepared in Example 5 and Comparative Examples 4-6 above, the state of the electrolyte was observed in a low temperature environment of -25°C as in the first experimental group, and the capacitance and impedance of the aluminum electrolytic capacitor were measured in a room temperature environment of 20°C and a low temperature environment of -40°C as in the second experimental group. The change in capacitance and the impedance ratio in the low temperature environment of -40°C were calculated. The results are shown in Table 3 below.

[0045] [Table 3]

[0046]

[0047] As shown in Table 3 above, the electrolytes of Example 5 and Comparative Examples 4-6 were both in liquid state in a low-temperature environment of -25°C.

[0048] As shown in Table 3, taking the functional additive alumina as an example, the aluminum electrolytic capacitor made by adding 2.5 wt% alumina to the electrolyte in Example 5 has similar performance to the aluminum electrolytic capacitor made in Example 1. However, the electrolyte added with 5 wt% alumina in Comparative Example 4 has too high a viscosity to impregnate the elements, resulting in the inability to produce a capacitor.

[0049] Furthermore, as can be seen from Comparative Examples 5-6 in Table 3, even the aluminum electrolytic capacitors made with electrolytes containing low-freezing-point liquids still exhibit a higher absolute value of capacitance change rate in low-temperature environments than those in Examples 1 and 5. This indicates that aluminum electrolytic capacitors made with the functional additives of the present invention as electrolytes are more suitable for low-temperature environments than those made with electrolytes containing low-freezing-point liquids.

[0050] Fourth experimental group: Capacitor performance containing functional additives

[0051] In the fourth experimental group, aluminum electrolytic capacitors made with the electrolytes of Example 5 and Comparative Example 1 were tested for capacitance and dissipation factor (DF). The dissipation factor can be regarded as the degree of energy loss of a material under the action of an electric field. The smaller the value, the smaller the energy loss. Moreover, energy loss is often manifested in the form of heat energy. Therefore, the smaller the DF value, the better its thermal stability.

[0052] First, the capacitance and dissipation factor of the aluminum electrolytic capacitors of Example 5 and Comparative Example 1 were measured. Then, according to the industry testing standard for electrolytic capacitors, after a 1000-hour ripple current test at 125°C, their capacitance and dissipation factor were measured again, and the results are shown in Table 4 below.

[0053] [Table 4]

[0054]

[0055] After 1000 hours of 125°C ripple current testing, the DF value of the aluminum electrolytic capacitor corresponding to Comparative Example 1 without added functional additives increased significantly, while the DF value of the aluminum electrolytic capacitor corresponding to Example 5 with added alumina as a functional additive was significantly lower than that of Comparative Example 1. This indicates that Example 5 with added alumina as a functional additive has better thermal stability than Comparative Example 1 without added functional additives.

[0056] Based on the results of the four sets of experiments above, it can be concluded that the electrolyte of aluminum electrolytic capacitors containing functional additives, including metal oxides with a dielectric constant ≥ 7, exhibits better state and stability at low temperatures compared to electrolytes without added metal oxides with a dielectric constant less than 7 or with added low-freezing-point liquids.

[0057] As described above, the present invention provides an electrolyte for an aluminum electrolytic capacitor and an aluminum electrolytic capacitor. By adding functional additives including metal oxides with a dielectric constant ≥7, a low-temperature stable electrolyte for an aluminum electrolytic capacitor is provided to overcome the performance degradation caused by poor electrolyte flow.

[0058] Furthermore, by using the electrolyte of the aluminum electrolytic capacitor of the present invention, aluminum electrolytic capacitors with low temperature resistance and long life can be developed to meet the specifications of the electronic component market for capacitor operating temperature, service life, impedance characteristics, etc., and to meet the performance requirements of electronic devices for environmental tolerance, thus having considerable market application value.

[0059] Although the present invention has been disclosed above with reference to embodiments, it is not intended to limit the present invention. Anyone skilled in the art can make some modifications and refinements without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be determined by the appended claims.

Claims

1. An electrolyte for an aluminum electrolytic capacitor, characterized by comprising comprises: an electrolyte; an organic solvent; and a functional additive comprising a metal oxide having a dielectric constant ≥ 7, wherein the metal oxide having a dielectric constant ≥ 7 is present in an amount of at most 3 wt% of the total weight of the electrolyte. wherein the metal oxide is selected from one or more of the group consisting of aluminum oxide, zirconium oxide, titanium dioxide, niobium oxide, barium titanate, tantalum oxide, chromium oxide, zinc oxide, technetium oxide, tungsten oxide, hafnium oxide, bismuth oxide, antimony oxide, and vanadium oxide.

2. The electrolyte for an aluminum electrolytic capacitor according to claim 1, wherein wherein the dielectric constant is between 7 and 6000.

3. The electrolyte for an aluminum electrolytic capacitor according to claim 1, wherein wherein the functional additive is present in an amount of 0.5 wt% to 2.5 wt% of the total weight of the electrolyte.

4. The electrolyte for an aluminum electrolytic capacitor according to claim 1, wherein wherein the metal oxide having a dielectric constant ≥ 7 is present in an amount of 0.3 wt% to 3 wt% of the total weight of the electrolyte.

5. The electrolyte for an aluminum electrolytic capacitor according to claim 1, wherein wherein the metal oxide having a dielectric constant ≥ 7 is present in an amount of 0.5 wt% to 3 wt% of the total weight of the electrolyte.

6. The electrolyte for an aluminum electrolytic capacitor according to claim 1, wherein wherein the metal oxide having a dielectric constant ≥ 7 is present in an amount of 0.5 wt% to 2.5 wt% of the total weight of the electrolyte.

7. The electrolyte for an aluminum electrolytic capacitor according to claim 1, wherein wherein the electrolyte comprises ammonium azelate, ammonium adipate, ammonium sebacate, ammonium dodecanedioate, ammonium C6-C8 branched-chain dicarboxylate, ammonium borate, or a combination thereof.

8. The electrolyte for an aluminum electrolytic capacitor according to claim 1, wherein wherein the organic solvent comprises ethylene glycol, diethylene glycol, propylene glycol, 1,4-butanediol, glycerol, N,N-dimethylformamide, γ-butyrolactone, caprolactone, diethylene glycol methyl ether, diethylene glycol monobutyl ether, valerolactone, or a combination thereof.

9. The electrolyte for an aluminum electrolytic capacitor according to claim 1, wherein 10. An aluminum electrolytic capacitor comprising: an element comprising: an anode foil; a cathode foil; and a separator film between the anode foil and the cathode foil; and an electrolyte of the aluminum electrolytic capacitor of any one of claims 1 to 9, wherein the element is impregnated in the electrolyte. ​

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