TWI858905B - Solid electrolytic capacitor and hybrid electrolytic capacitor - Google Patents

Abstract

A hybrid electrolytic capacitor includes an anode foil with a dielectric oxide film thereon, a cathode foil, and a separator film between the anode foil and the cathode foil. A solid electrolyte is formed on the surface of the dielectric oxide film on the anode foil, and the solid foil includes a conductive polymer. A liquid electrolyte filled in a space between the anode foil, the cathode foil, and the separator film, and the liquid electrolyte includes a solvent with a boiling point higher than 150˚C. The solid electrolyte, the liquid electrolyte, or both includes a zwitterionic compound having a chemical structure of

Description

Solid Electrolytic Capacitors and Hybrid Electrolytic Capacitors

The present invention relates to an electrolytic capacitor, and more particularly to the composition of an electrolyte thereof.

Electrolytic capacitors are usually made by oxidizing the metal surface to form a porous dielectric, and introducing liquid or solid conductive materials into this porous structure to form the cathode and anode. Commonly used aluminum capacitors are made by winding or stacking, and other electrical connectors and packaging are used on the outside to obtain electrolytic capacitors.

The low-temperature capacitance decay rate and low-temperature ESR resistance increase rate of current electrolytic capacitors at low temperatures are relatively high, so a novel electrolyte composition is urgently needed to overcome the above problems.

The solid electrolytic capacitor provided in one embodiment of the present invention comprises: an anode foil having a dielectric oxide film thereon; a cathode foil; a separator film located between the anode foil and the cathode foil; and a solid electrolyte formed on the surface of the dielectric oxide film on the anode foil; wherein the solid electrolyte comprises a conductive polymer and an amphoteric ion compound, wherein the chemical structure of the amphoteric ion compound is ; wherein R ¹ is a C _1-6 straight or branched alkyl group; R ² , R ³ , and R ⁴ are each independently H or a C _1-6 straight or branched alkyl group; and L is a C _1-12 straight or branched alkyl group.

In some embodiments, the zwitterionic compound accounts for 1 wt % to 50 wt % of the solid electrolyte.

In some embodiments, the conductive polymer includes poly (3,4-dioxyethylthiophene: polystyrene sulfonic acid) (PEDOT:PSS), poly (thiophene), poly (p-phenylene sulfide), polycarbazole, polyindole, polyaniline, polypyrrole, poly (fluorene), polyphenylene, polypyrene, polyazulene, polynaphthalene, poly (acetylene), or poly (p-phenylene vinylene).

The hybrid electrolytic capacitor provided by the embodiment of the present invention includes: an anode foil having a dielectric oxide film thereon; a cathode foil; a separator film located between the anode foil and the cathode foil; a solid electrolyte formed on the surface of the dielectric oxide film on the anode foil, and the solid electrolyte includes a conductive polymer; and a liquid electrolyte filled in the space between the anode foil, the cathode foil, and the separator film, and the liquid electrolyte includes a solvent with a boiling point higher than 150°C, wherein the solid electrolyte, the liquid electrolyte, or both of the above include a zwitterionic compound, whose chemical structure is ; wherein R ¹ is a C _1-6 straight or branched alkyl group; R ² , R ³ , and R ⁴ are each independently H or a C _1-6 straight or branched alkyl group; and L is a C _1-12 straight or branched alkyl group.

In some embodiments, when the solid electrolyte includes the amphoteric ionic compound, the amphoteric ionic compound accounts for 1 wt % to 50 wt % of the solid electrolyte.

In some embodiments, when the liquid electrolyte includes amphoteric ionic compounds, the amphoteric ionic compounds account for 1 wt % to 50 wt % of the liquid electrolyte.

In some embodiments, when the solid electrolyte and the liquid electrolyte include amphoteric ionic compounds, the chemical structure of the amphoteric ionic compound in the solid electrolyte is the same as the chemical structure of the amphoteric ionic compound in the liquid electrolyte.

In some embodiments, when the solid electrolyte and the liquid electrolyte include amphoteric ionic compounds, the chemical structure of the amphoteric ionic compound in the solid electrolyte is different from the chemical structure of the amphoteric ionic compound in the liquid electrolyte.

In some embodiments, the solvent having a boiling point higher than 150°C includes propylene glycol, glycerol, γ-butyrolactone, γ-valerolactone, N-methylpyrrolidone, dimethyl sulfoxide, or cyclobutane sulfone.

In some embodiments, the liquid electrolyte further includes a liquid polymer.

In some embodiments, the liquid polymer includes a polyalkylene glycol.

In one embodiment of the present invention, a wound blank electrode body is used to prepare a capacitor. As shown in FIG1 , the anode foil 101 and cathode foil 103 contained in the wound blank electrode body 100 are metal foils, and the anode foil 101 further has a dielectric oxide film 201 such as a porous metal oxide thereon. A separator 102 is sandwiched between the anode foil 101 and the cathode foil 103. The anode foil 101 and the cathode foil 103 can each be made of bismuth, magnesium, aluminum, germanium, tin, antimony, bismuth, titanium, zirconium, uranium, vanadium, niobium, tungsten, or alloys thereof. The dielectric oxide film 201, such as a porous metal oxide, may be a porous oxide of a metal corresponding to the anode foil 101. For example, the anode foil 101 may be an aluminum foil, and the dielectric oxide film 201 may be a porous aluminum oxide. The isolation film 102 may be cellulose, polyethylene terephthalate, polybutylene terephthalate, polyethylene, polypropylene, polyvinylidene fluoride, other suitable polymers, a mixture thereof, or a multi-layer structure thereof. The anode foil 101 , the cathode foil 103 , and the separator 102 are rolled into a roll, and the anode wire 104 and the cathode wire 105 are connected to the anode foil 101 and the cathode foil 103 , respectively, to form a rolled blank electrode body 100 .

As shown in FIG. 2A , a solid electrolyte 202 may be formed on the surface of the dielectric oxide film 201 on the anode foil 101 in the wound blank electrode 100. The method for forming the solid electrolyte 202 may be to immerse the wound blank electrode 100 in a dispersion containing the solid electrolyte, repeatedly evacuate and release the vacuum for multiple times so that the surface of the dielectric oxide film 201 on the anode foil 101 of the wound blank electrode 100 adsorbs the dispersion containing the solid electrolyte and then dries. The adsorption and drying steps are repeated multiple times to form the solid electrolyte 202 on the surface of the dielectric oxide film 201 on the anode foil 101.

As shown in FIG3 , the wound blank electrode body 100 having the solid electrolyte 202 is placed in a housing 301. The housing 301 is covered with a cover 302, and then the housing 301, the cover 302, the gap between the anode lead 104 and the cathode lead 105 are sealed with a packaging glue 303 to form a package 300, that is, a solid electrolytic capacitor (containing only the solid electrolyte 202 but no liquid electrolyte).

On the other hand, a solid electrolyte 202 is formed on the surface of the dielectric oxide film 201 on the anode foil 101 in the wound blank electrode 100. The formation method is as described above and will not be repeated here. Then, the wound blank electrode 100 with the solid electrolyte 202 is immersed in the liquid electrolyte 203, and the vacuum is repeatedly drawn and released for many times to facilitate the electrode to absorb the liquid electrolyte 203. The combination of the liquid electrolyte 203 and the solid electrolyte 202 is the mixed electrolyte 200. After the rolled blank electrode body 100 with the hybrid electrolyte 200 is placed in the housing 301, the housing 301 is covered with a cover 302, and then the housing 301, the cover 302, the gap between the anode lead 104 and the cathode lead 105 are sealed with a packaging glue 303 to form a package 300, that is, a hybrid electrolytic capacitor (containing a solid electrolyte 202 and a liquid electrolyte 203) is formed.

In one embodiment, the solid electrolytic capacitor includes an anode foil 101 (having a dielectric oxide film 201 thereon), a cathode foil 103, and a separator 102 located between the anode foil 101 and the cathode foil 103, as shown in FIG2A. The solid electrolyte 202 is formed on the surface of the dielectric oxide film 201 on the anode foil 101, and the solid electrolyte 202 includes a conductive polymer and an amphoteric ion compound, wherein the chemical structure of the amphoteric ion compound is R ¹ is a C _1-6 straight or branched alkyl group, R ² , R ³ , and R ⁴ are each independently H or a C _1-6 straight or branched alkyl group; and L is a C _1-12 straight or branched alkyl group.

In some embodiments, the amphoteric compound accounts for 1 wt% to 50 wt% of the solid electrolyte 202. If the proportion of the amphoteric compound is too low, the effect is similar to that of no amphoteric compound; if the proportion of the amphoteric compound is too high, it is not conducive to the matrix properties of the conductive polymer. In some embodiments, the conductive polymer includes poly (3,4-dioxyethylthiophene: polystyrene sulfonic acid) (PEDOT:PSS), poly (thiophene), poly (p-phenylene sulfide), polycarbazole, polyindole, polyaniline, polypyrrole, poly (fluorene), polyphenylene, polypyrene, polyazulene, polynaphthalene, poly (acetylene), or poly (p-phenylene vinylene).

The hybrid electrolytic capacitor provided by one embodiment of the present invention includes an anode foil 101 (having a dielectric oxide film 201 thereon), a cathode foil 103, and a separator 102 located between the anode foil 101 and the cathode foil 103, as shown in FIG2B. A solid electrolyte 202 is formed on the surface of the dielectric oxide film 201 on the anode foil 101, and the solid electrolyte 202 includes a conductive polymer. The types of conductive polymers are as described above and are not repeated here. A liquid electrolyte 203 is filled in the space between the anode foil, the cathode foil, and the separator, and the liquid electrolyte 203 includes a solvent having a boiling point higher than 150°C.

In the hybrid electrolytic capacitor, the solid electrolyte 202, the liquid electrolyte 203, or both of them include amphoteric ionic compounds, the chemical structure of which is R ¹ is a C _1-6 straight or branched alkyl group; R ² , R ³ , and R ⁴ are each independently H or a C _1-6 straight or branched alkyl group; and L is a C _1-12 straight or branched alkyl group.

In some embodiments, when the solid electrolyte 202 includes the amphoteric ionic compound, the amphoteric ionic compound accounts for 1 wt% to 50 wt% of the solid electrolyte. If the proportion of the amphoteric ionic compound is too low, the effect is similar to that of the solid electrolyte without the amphoteric ionic compound; if the proportion of the amphoteric ionic compound is too high, it is not conducive to the matrix properties of the conductive polymer. In some embodiments, when the liquid electrolyte 203 includes the amphoteric ionic compound, the amphoteric ionic compound accounts for 1 wt% to 50 wt% of the liquid electrolyte. If the proportion of the amphoteric ionic compound is too low, the effect is similar to that of the solid electrolyte without the amphoteric ionic compound. If the proportion of the amphoteric ionic compound is too high, the viscosity will be too thick and not conducive to filling and adsorption. The most appropriate proportion is between 10 wt% and 30 wt%.

In some embodiments, when the solid electrolyte 202 and the liquid electrolyte 203 include amphoteric ionic compounds, the chemical structure of the amphoteric ionic compound in the solid electrolyte 202 is the same as the chemical structure of the amphoteric ionic compound in the liquid electrolyte 203.

In some embodiments, when the solid electrolyte 202 and the liquid electrolyte 203 include amphoteric ionic compounds, the chemical structure of the amphoteric ionic compound in the solid electrolyte 202 is different from the chemical structure of the amphoteric ionic compound in the liquid electrolyte 203.

In some embodiments, the solvent with a boiling point higher than 150°C includes propylene glycol, glycerol, γ-butyrolactone, γ-valerolactone, N-methylpyrrolidone, dimethyl sulfoxide or cyclobutane sulfone. If the boiling point of the solvent is lower than or equal to 150°C, it is easy to explode when exposed to high temperature, and the electrolyte scatters and causes a short circuit. For safety considerations, in some embodiments, the liquid electrolyte further includes a liquid polymer such as polyalkylene glycol, which helps to increase the stability of the liquid electrolyte. In some embodiments, the polyalkylene glycol can be polyethylene glycol. In some embodiments, the molecular weight of the polyalkylene glycol can be 200 to 2000. If the molecular weight of the polyalkylene glycol is too low, the boiling point is too low and does not meet the requirements. If the molecular weight of the alkyl diol is too high, it may be solid rather than liquid.

It is worth noting that the above-mentioned method for forming the capacitor is only used as an example and is not intended to limit the present invention. A person skilled in the art can use any method to form the capacitor of the present invention, but is not limited to the above-mentioned method.

In addition, the formation method of the zwitterionic compound can be to react an imidazole compound with a sultone compound as follows. It is understood that the following method for synthesizing the zwitterionic compound is only used for example and is not intended to limit the present invention. A person with ordinary knowledge in the art can use any method to synthesize the zwitterionic compound, and is not limited to the following synthesis method.

In some embodiments, the chemical structure of the zwitterionic compound formed by the above reaction can be , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , or other suitable chemical structures.

Experiments show that solid electrolytic capacitors or hybrid electrolytic capacitors using amphoteric ionic compounds have lower low-temperature capacitance decay rate and low-temperature ESR resistance increase rate.

In order to make the above contents and other purposes, features, and advantages of this disclosure more clearly understood, the following is a detailed description of the embodiments with the accompanying drawings as follows: [Embodiment]

In the following embodiments, a wound blank electrode (CHINSAN electronic) is used. The wound blank electrode contains an anode foil whose surface is oxidized to porous aluminum oxide (such as a dielectric oxide film), a cathode foil is an aluminum foil with a smooth surface, and a separator film is sandwiched between the anode foil and the cathode foil. The anode foil, the cathode foil, and the separator film are wound into a roll, and the anode wire and the cathode wire are connected to the anode foil and the cathode foil respectively to form a wound blank electrode.

Immerse the wound blank electrode in the dispersion and repeatedly evacuate and release the vacuum for several times to promote adsorption. Then dry the wound blank electrode adsorbing the dispersion at a high temperature for a period of time. Repeat the adsorption and drying steps three times to form a solid electrolyte on the surface of the dielectric oxide film on the anode foil. Place the wound blank electrode with the solid electrolyte in an outer casing. Cover the outer casing with a cover, and then seal the outer casing, the cover, the anode wire, and the gap between the cathode wire with a packaging glue to form a solid electrolytic capacitor (containing only solid electrolyte and no liquid electrolyte).

On the other hand, after forming a solid electrolyte on the surface of the porous aluminum oxide (such as a dielectric oxide film) on the anode foil, the wound blank electrode with the solid electrolyte is immersed in the liquid electrolyte, and the vacuum is repeatedly evacuated and released for many times to facilitate the electrode to absorb the liquid electrolyte. The combination of the liquid electrolyte and the solid electrolyte is a hybrid electrolyte. After the wound blank electrode with the hybrid electrolyte is placed in an outer casing, the outer casing is covered with a cover, and then the outer casing, the cover, the gap between the anode wire and the cathode wire are sealed with a packaging glue, so as to form a hybrid electrolytic capacitor (containing a solid electrolyte and a liquid electrolyte).

In the following examples, the viscosity of the dispersion or liquid electrolyte was measured using a rheometer (Brookfield LVDV-II pro) at a shear rate of 100 Hz at 25°C.

In the following examples, the dispersion (2.5 g) was dried at 130° C. for 3 hours, and the solid content of the dispersion was measured by differential gravimetric method.

In the following example, an LCR meter (Agilent 4263B) was used to measure the capacitance of a capacitor at 35V at room temperature, -40°C, and -55°C at 120 Hz to calculate the low-temperature capacitance decay rate (%) of the capacitor at low temperature compared to the capacitor at room temperature.

In the following example, an LCR meter (Agilent 4263B) was used to measure the equivalent series resistance (ESR) of a capacitor at 35V at room temperature, -40°C, and -55°C at 100 KHz to calculate the low temperature ESR resistance increase rate (%) of the capacitor at low temperature compared to the capacitor at room temperature.

Synthesis Example 1 (Compound I-1) 1-Methylimidazole (24.6 g, 0.3 mol) was dissolved in ethylene glycol dimethyl ether (100 g) and heated to 80°C under a nitrogen system. 1,4-Butanesulfonate (40.8 g, 0.3 mol) was gradually added dropwise to the solution over 1 hour, and then maintained at 80°C for 3 hours, and then cooled to 0°C to 5°C to precipitate a white solid. The solid was collected after filtration and dried under vacuum to obtain Compound I-1 (43.2 g), which appeared as white crystals. The hydrogen spectrum of compound I-1 is as follows: ¹ H-NMR (500 MHz, CD ₃ OD): 1.78-1.84 (m, 2H), 2.04-2.10 (m, 2H), 2.87 (t, 2H, J=7.5Hz), 3.96 (s, 3H), 4.29 (t, 2H, J=7.3Hz), 7.59 (d, 1H, J=2.5Hz), 7.68 (d, 1H, J=2.5Hz), 8.99 (s, 1H). The carbon spectrum of compound I-1 is as follows: ¹³ C-NMR (125 MHz, CD ₃ OD): 22.88, 30.00, 36.69, 50.44, 51.61, 123.83, 125.13, 138.12. The above reaction is shown in the following formula: .

Synthesis Example 2 (Compound I-2) 1,2-dimethylimidazole (28.8 g, 0.3 mol) was dissolved in ethylene glycol dimethyl ether (100 g) and heated to 80°C under a nitrogen system. 1,4-Butanesulfonate (40.8 g, 0.3 mol) was gradually added dropwise to the solution over 1 hour, and then maintained at 80°C for 3 hours, and then cooled to 0°C to 5°C to precipitate a white solid. The solid was collected after filtration and dried under vacuum to obtain compound I-2 (60.2 g), which appeared as white crystals. The hydrogen spectrum of compound I-2 is as follows: ¹ H-NMR (500 MHz, CD ₃ OD): 1.82-1.88 (m, 2H), 2.02-2.08 (m, 2H), 2.70 (s, 3H), 2.89 (t, 2H, J=7.3Hz), 3.87 (s, 3H), 4.25 (t, 2H, J=7.50Hz), 7.52 (d, 1H, J=2.0Hz), 7.59 (d, 1H, J=2.0Hz). The carbon spectrum of compound I-2 is as follows: ¹³ C-NMR (125 MHz, CD ₃ OD): 9.67, 22.99, 29.59, 35.54, 51.58, 122.38, 123.78, 146.12. The above reaction is shown in the following formula: .

Preparation Example 1 (Liquid Electrolyte H-1) Propylene glycol (50 g) and compound I-1 (25 g) were mixed and heated to dissolve, and then liquid polymer PEG-400 (25 g) was added. After stirring and cooling to room temperature, liquid electrolyte H-1 was obtained.

Preparation Example 2 (Liquid Electrolyte H-2) Propylene glycol (85 g) and compound I-2 (15 g) were mixed and heated to dissolve. After stirring and cooling to room temperature, liquid electrolyte H-2 was obtained.

Preparation Example 3 (Liquid Electrolyte H-3) Propylene glycol (60 g) and liquid polymer PEG-400 (30 g) were mixed and heated to dissolve. After stirring and cooling to room temperature, liquid electrolyte H-3 was obtained.

Preparation Example 4 (Dispersion D-1, without zwitterionic compounds) Take a liquid containing 1.3% PEDOT/PSS (85 g, purchased from CP-WL2A of Dali Polymer, pH=4.0) and a mixed liquid (15 g, the weight ratio of propylene glycol: glycerol: PEG-400 is 1:2:2) and stir vigorously to obtain dispersion D-1.

Preparation Example 5 (Dispersion D-2, containing compound I-1) Take a liquid containing 1.3% PEDOT/PSS (85 g, purchased from CP-WL2A of Dali Polymer, pH=4.0), a mixed liquid (14 g, the weight ratio of propylene glycol: glycerol: PEG-400 is 1:2:2), and compound I-1 (1 g) and stir vigorously to obtain dispersion D-2.

The properties of the above liquid electrolyte and dispersion are shown in Table 1:

Table 1 pH Solid content (%) Viscosity(cP) Liquid Electrolyte H-1 - - 54.5 Liquid Electrolyte H-2 - - 47.5 Liquid Electrolyte H-3 - - 43.9 Dispersion D-1 3.09 9.13 13.0 Dispersion D-2 3.08 9.74 12.9

The pH of dispersions D-1 and D-2 was maintained between 3 and 4, the solid content was maintained between 9% and 10%, and the viscosity was maintained at a low level (<15 cP). The viscosity of the liquid electrolyte was maintained below 60 cP, and the adsorption was good during the subsequent immersion of the wound blank electrode.

Example 1 (Solid Electrolytic Capacitor) Immerse a wound blank electrode in dispersion D-2 and repeatedly evacuate and release the vacuum for 8 times to promote adsorption. Then dry the wound blank electrode after adsorbing dispersion D-2 at 135°C for 30 minutes. Repeat the adsorption and drying steps 3 times to form a solid electrolyte on the surface of the porous aluminum oxide (such as a dielectric oxide film) on the anode foil. Place the wound blank electrode with the solid electrolyte in an outer casing. Cover the outer casing with a cover, and then seal the outer casing, the cover, the gap between the anode wire and the cathode wire with a packaging glue to form a solid electrolytic capacitor. Measure the capacitance and ESR of this capacitor at different temperatures to calculate its capacitance decay rate and ESR resistance increase rate at different temperatures.

Example 2 (Hybrid Electrolytic Capacitor) Immerse a wound blank electrode in dispersion D-1 and repeatedly evacuate and release the vacuum for 8 times to promote adsorption. Then dry the wound blank electrode after adsorbing dispersion D-1 at 135°C for 30 minutes. Repeat the adsorption and drying steps 3 times to form a solid electrolyte on the surface of the porous aluminum oxide (such as a dielectric oxide film) on the anode foil. Immerse the wound blank electrode with the solid electrolyte in liquid electrolyte H-1 and repeatedly evacuate and release the vacuum for 8 times to facilitate the electrode to adsorb the liquid electrolyte H-1. The combination of liquid electrolyte H-1 and solid electrolyte is a hybrid electrolyte. After placing the rolled blank electrode body with hybrid electrolyte into the outer casing, the outer casing is covered with a cover, and then the gaps between the outer casing, the cover, the anode wire, and the cathode wire are sealed with a sealing glue to form a hybrid electrolytic capacitor. The capacitance and ESR of this capacitor at different temperatures are measured to calculate its capacitance decay rate and ESR resistance increase rate at different temperatures.

Example 3 (Hybrid Electrolytic Capacitor) Immerse the wound blank electrode in the dispersion D-2 and repeatedly evacuate and release the vacuum for 8 times to promote adsorption. Then dry the wound blank electrode after adsorbing the dispersion D-2 at 135°C for 30 minutes. Repeat the adsorption and drying steps 3 times to form a solid electrolyte on the surface of the porous aluminum oxide (such as a dielectric oxide film) on the anode foil. Immerse the wound blank electrode with the solid electrolyte in the liquid electrolyte H-1 and repeatedly evacuate and release the vacuum for 8 times to facilitate the electrode to adsorb the liquid electrolyte H-1. The combination of the liquid electrolyte H-1 and the solid electrolyte is the hybrid electrolyte. After placing the rolled blank electrode body with hybrid electrolyte into the outer casing, the outer casing is covered with a cover, and then the gaps between the outer casing, the cover, the anode wire, and the cathode wire are sealed with a sealing glue to form a hybrid electrolytic capacitor. The capacitance and ESR of this capacitor at different temperatures are measured to calculate its capacitance decay rate and ESR resistance increase rate at different temperatures.

Example 4 (Hybrid Electrolytic Capacitor) Immerse a wound blank electrode in dispersion D-1 and repeatedly evacuate and release the vacuum for 8 times to promote adsorption. Then dry the wound blank electrode after adsorbing dispersion D-1 at 135°C for 30 minutes. Repeat the adsorption and drying steps 3 times to form a solid electrolyte on the surface of the porous aluminum oxide (such as a dielectric oxide film) on the anode foil. Immerse the wound blank electrode with the solid electrolyte in liquid electrolyte H-2 and repeatedly evacuate and release the vacuum for 8 times to facilitate the electrode to adsorb the liquid electrolyte H-2. The combination of liquid electrolyte H-2 and solid electrolyte is a hybrid electrolyte. After placing the rolled blank electrode body with hybrid electrolyte into the outer casing, the outer casing is covered with a cover, and then the gaps between the outer casing, the cover, the anode wire, and the cathode wire are sealed with a sealing glue to form a hybrid electrolytic capacitor. The capacitance and ESR of this capacitor at different temperatures are measured to calculate its capacitance decay rate and ESR resistance increase rate at different temperatures.

Example 5 (Hybrid Electrolytic Capacitor) Immerse a wound blank electrode in dispersion D-2 and repeatedly evacuate and release the vacuum for 8 times to promote adsorption. Then dry the wound blank electrode after adsorbing dispersion D-2 at 135°C for 30 minutes. Repeat the adsorption and drying steps 3 times to form a solid electrolyte on the surface of the porous aluminum oxide (such as a dielectric oxide film) on the anode foil. Immerse the wound blank electrode with the solid electrolyte in liquid electrolyte H-2 and repeatedly evacuate and release the vacuum for 8 times to facilitate the electrode to adsorb the liquid electrolyte H-2. The combination of liquid electrolyte H-2 and solid electrolyte is a hybrid electrolyte. After placing the rolled blank electrode body with hybrid electrolyte into the outer casing, the outer casing is covered with a cover, and then the gaps between the outer casing, the cover, the anode wire, and the cathode wire are sealed with a sealing glue to form a hybrid electrolytic capacitor. The capacitance and ESR of this capacitor at different temperatures are measured to calculate its capacitance decay rate and ESR resistance increase rate at different temperatures.

Example 6 (Hybrid Electrolytic Capacitor) Immerse the wound blank electrode in the dispersion D-2 and repeatedly evacuate and release the vacuum for 8 times to promote adsorption. Then dry the wound blank electrode after adsorbing the dispersion D-2 at 135°C for 30 minutes. Repeat the adsorption and drying steps 3 times to form a solid electrolyte on the surface of the porous aluminum oxide (such as a dielectric oxide film) on the anode foil. Immerse the wound blank electrode with the solid electrolyte in the liquid electrolyte H-3 and repeatedly evacuate and release the vacuum for 8 times to facilitate the electrode to adsorb the liquid electrolyte H-3. The combination of the liquid electrolyte H-3 and the solid electrolyte is the hybrid electrolyte. After placing the rolled blank electrode body with hybrid electrolyte into the outer casing, the outer casing is covered with a cover, and then the gaps between the outer casing, the cover, the anode wire, and the cathode wire are sealed with a sealing glue to form a hybrid electrolytic capacitor. The capacitance and ESR of this capacitor at different temperatures are measured to calculate its capacitance decay rate and ESR resistance increase rate at different temperatures.

Comparative Example 1 (Solid Electrolytic Capacitor) Immerse the wound blank electrode in the dispersion D-1 and repeatedly evacuate and release the vacuum for 8 times to promote adsorption. Then dry the wound blank electrode after adsorbing the dispersion D-1 at 135°C for 30 minutes. Repeat the adsorption and drying steps 3 times to form a solid electrolyte on the surface of the porous aluminum oxide (such as a dielectric oxide film) on the anode foil. Place the wound blank electrode with the solid electrolyte in an outer casing. Cover the outer casing with a cover, and then seal the outer casing, the cover, the gap between the anode wire and the cathode wire with a packaging glue to form a solid electrolytic capacitor. Measure the capacitance and ESR of this capacitor at different temperatures to calculate its capacitance decay rate and ESR resistance increase rate at different temperatures.

Comparative Example 2 (Hybrid Electrolytic Capacitor) Immerse the wound blank electrode in the dispersion D-1 and repeatedly evacuate and release the vacuum for 8 times to promote adsorption. Then dry the wound blank electrode after adsorbing the dispersion D-1 at 135°C for 30 minutes. Repeat the adsorption and drying steps 3 times to form a solid electrolyte on the surface of the porous aluminum oxide (such as a dielectric oxide film) on the anode foil. Immerse the wound blank electrode with the solid electrolyte in the liquid electrolyte H-3 and repeatedly evacuate and release the vacuum for 8 times to facilitate the electrode to adsorb the liquid electrolyte H-3. The combination of the liquid electrolyte H-3 and the solid electrolyte is the hybrid electrolyte. After placing the rolled blank electrode body with hybrid electrolyte into the outer casing, the outer casing is covered with a cover, and then the gaps between the outer casing, the cover, the anode wire, and the cathode wire are sealed with a sealing glue to form a hybrid electrolytic capacitor. The capacitance and ESR of this capacitor at different temperatures are measured to calculate its capacitance decay rate and ESR resistance increase rate at different temperatures.

The composition of the above capacitors and the capacitance decay rate at different temperatures (compared to the capacitance at room temperature) are shown in Table 2:

Table 2 The composition of zwitterions in solid electrolytes Composition of zwitterions in liquid electrolytes Capacitance decay rate at -40 ˚C δCap ^{RT →-40 ˚ C} Capacitance decay rate at -55˚C δCap ^{RT→-55 ˚ C} Embodiment 1 I-1/D-2 No liquid electrolyte -23.4% -28.1% Comparison Example 1 - /D-1 No liquid electrolyte -27.6% -31.5% Embodiment 2 - /D-1 I-1/H-1 -12.6% -18.1% Embodiment 3 I-1/D-2 I-1/H-1 -12.7% -17.3% Embodiment 4 - /D-1 I-2/H-2 -14.7% -19.8% Embodiment 5 I-1/D-2 I-2/H-2 -11.8% -16.2% Embodiment 6 I-1/D-2 -/H-3 -12.9% -19.0% Comparison Example 2 - /D-1 -/H-3 -13.6% -20.8%

Table 2 shows that Example 1, a solid electrolyte containing compound I-1, has a low-temperature capacitance decay rate (δCap) of a solid electrolytic capacitor lower than that of Comparative Example 1, indicating that amphoteric ionic compounds such as compound I-1 can improve the problem of low-temperature capacitance decay. The hybrid electrolytic capacitor of Comparative Example 2 has a good low-temperature capacitance decay rate (-13.6%) at -40°C, but a poor low-temperature capacitance decay rate (-20.8%) at a more severe low temperature such as -55°C. In addition to having a good low-temperature capacitance decay rate (optimum -11.8%) at -40°C, the hybrid electrolytic capacitors of Examples 2 to 6 of the present invention are superior to Comparative Example 2 in low-temperature capacitance decay rates (optimum -16.2%) at more severe low temperatures such as -55°C. From the above, it can be seen that adding amphoteric ionic compounds (such as compound I-1 or I-2) to solid electrolytes, liquid electrolytes, or both can reduce the low-temperature capacitance decay rate of hybrid electrolytic capacitors.

Table 3 Zwitterionic/Solid Electrolyte Zwitterionic/Liquid Electrolyte ESR resistance increase rate at -40°C δESR ^{RT →-40°C} ESR resistance increase rate at -55°C δESR ^{RT →-55°C} Embodiment 1 I-1/D-2 No liquid electrolyte +8.91% +22.3% Comparison Example 1 - /D-1 No liquid electrolyte +16.4% +25.1% Embodiment 2 - /D-1 I-1/H-1 +13.9% +17.0% Embodiment 3 I-1/D-2 I-1/H-1 +11.0% +15.0% Embodiment 4 - /D-1 I-2/H-2 +6.01% +18.0% Embodiment 5 I-1/D-2 I-2/H-2 +8.83% +18.2% Embodiment 6 I-1/D-2 -/H-3 +7.57% +21.7% Comparison Example 2 - /D-1 - /H-3 +10.1% +24.7%

As shown in Table 3, the solid electrolytic capacitor or hybrid electrolytic capacitor using amphoteric ion compounds in the embodiments of the present invention has an ESR resistance increase rate at a severe temperature of -55°C that is lower than that of the comparative example. The above experiments prove that the electrolytic capacitor using amphoteric ion compounds has a lower low-temperature ESR resistance increase rate.

Although the present disclosure has been disclosed as above with several preferred embodiments, they are not intended to limit the present disclosure. Anyone with ordinary knowledge in the relevant technical field can make any changes and modifications without departing from the spirit and scope of the present disclosure. Therefore, the protection scope of the present disclosure shall be defined by the scope of the attached patent application.

100: Wound blank electrode 101: Anode foil 102: Isolation film 103: Cathode foil 104: Anode conductor 105: Cathode conductor 200: Hybrid electrolyte 201: Dielectric oxide film 202: Solid electrolyte 203: Liquid electrolyte 300: Package 301: Housing 302: Cover 303: Package glue

FIG. 1 is a schematic diagram of a wound blank electrode in an embodiment of the present invention. FIG. 2A is a schematic diagram of an electrode and a solid electrolyte in an embodiment of the present invention. FIG. 2B is a schematic diagram of an electrode and a mixed electrolyte in an embodiment of the present invention. FIG. 3 is a schematic diagram of an electrolytic capacitor in an embodiment of the present invention.

101: Anode foil

102: Isolation film

103: cathode foil

200:Mixed electrolyte

201: Dielectric oxide film

202: Solid electrolyte

203: Liquid electrolyte

Claims (11)

A solid electrolytic capacitor comprises: an anode foil having a dielectric oxide film thereon; a cathode foil; a separator film located between the anode foil and the cathode foil; and a solid electrolyte formed on the surface of the dielectric oxide film on the anode foil; wherein the solid electrolyte comprises a conductive polymer and an amphoteric ion compound, wherein the chemical structure of the amphoteric ion compound is ; wherein R ¹ is a C _1-6 straight or branched alkyl group; R ² , R ³ , and R ⁴ are each independently H or a C _1-6 straight or branched alkyl group; and L is a C _1-12 straight or branched alkyl group. A solid electrolytic capacitor as claimed in claim 1, wherein the amphoteric ionic compound accounts for 1 wt% to 50 wt% of the solid electrolyte. A solid electrolytic capacitor as claimed in claim 1, wherein the conductive polymer comprises poly (3,4-dioxyethylthiophene:polystyrene sulfonic acid) (PEDOT:PSS), poly (thiophene), poly (p-phenylene sulfide), polycarbazole, polyindole, polyaniline, polypyrrole, poly (fluorene), polyphenylene, polypyrene, polyazulene, polynaphthalene, poly (acetylene), or poly (p-phenylene vinylene). A hybrid electrolytic capacitor comprises: an anode foil having a dielectric oxide film thereon; a cathode foil; a separator film located between the anode foil and the cathode foil; a solid electrolyte formed on the surface of the dielectric oxide film on the anode foil, and the solid electrolyte comprises a conductive polymer; and a liquid electrolyte filled in the space between the anode foil, the cathode foil, and the separator film, and the liquid electrolyte comprises a solvent having a boiling point higher than 150°C; wherein the solid electrolyte, the liquid electrolyte, or both of the above comprises an amphoteric ionic compound having a chemical structure of ; wherein R ¹ is a C _1-6 straight or branched alkyl group; R ² , R ³ , and R ⁴ are each independently H or a C _1-6 straight or branched alkyl group; and L is a C _1-12 straight or branched alkyl group. In the hybrid electrolytic capacitor of claim 4, when the solid electrolyte includes the amphoteric ionic compound, the amphoteric ionic compound accounts for 1 wt% to 50 wt% of the solid electrolyte. In the hybrid electrolytic capacitor of claim 4, when the liquid electrolyte comprises the amphoteric ionic compound, the amphoteric ionic compound accounts for 1 wt% to 50 wt% of the liquid electrolyte. In the hybrid electrolytic capacitor of claim 4, wherein the solid electrolyte and the liquid electrolyte include the amphoteric ionic compound, the chemical structure of the amphoteric ionic compound in the solid electrolyte is the same as the chemical structure of the amphoteric ionic compound in the liquid electrolyte. In the hybrid electrolytic capacitor of claim 4, wherein the solid electrolyte and the liquid electrolyte include the zwitterionic compound, the chemical structure of the zwitterionic compound in the solid electrolyte is different from the chemical structure of the zwitterionic compound in the liquid electrolyte. A hybrid electrolytic capacitor as claimed in claim 4, wherein the solvent having a boiling point higher than 150°C comprises propylene glycol, glycerol, γ-butyrolactone, γ-valerolactone, N-methylpyrrolidone, dimethyl sulfoxide or cyclobutane sulfone. A hybrid electrolytic capacitor as claimed in claim 4, wherein the liquid electrolyte further includes a liquid polymer. A hybrid electrolytic capacitor as claimed in claim 10, wherein the liquid polymer comprises polyalkylene glycol.

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