CN113363076B

CN113363076B - Overvoltage automatic short-circuit protection capacitor

Info

Publication number: CN113363076B
Application number: CN202110905415.3A
Authority: CN
Inventors: 何霄云; 杨波; 陆小燕; 魏金京; 朱羽
Original assignee: NANTONG JIANGHAI CAPACITOR CO Ltd
Current assignee: NANTONG JIANGHAI CAPACITOR CO Ltd
Priority date: 2021-08-09
Filing date: 2021-08-09
Publication date: 2021-11-02
Anticipated expiration: 2041-08-09
Also published as: CN113363076A

Abstract

The invention relates to an overvoltage automatic short-circuit protection capacitor, which is characterized by comprising a winding body formed by winding a cathode foil, an electrolytic paper and an anode foil with an oxide film dielectric formed on the surface in sequence, wherein the winding body is internally provided with a conductive polymer layer and a working electrolyte for soaking the winding body with the conductive polymer layer; the electrolytic paper is positioned between the cathode foil and the anode foil; the electrolytic paper comprises the following materials in percentage by weight: 40-70% of wood pulp, 25-55% of reinforcing fiber and 1-5% of nano regenerated fiber; the nanometer regenerated fiber is cellulose acetate nanofiber and/or nanometer cuprammonium fiber, the diameter of the fiber is 50-600 nm, and the length-diameter ratio is larger than 2. The capacitor has an automatic short-circuit protection function under overpressure, and can prevent the explosion-proof valve at the bottom from being exploded.

Description

Overvoltage automatic short-circuit protection capacitor

Technical Field

The invention relates to the technical field of capacitors, in particular to a capacitor with overvoltage automatic short-circuit protection.

Background

The electrolytic capacitor adopts a coiled metal oxide film to form a cylindrical capacitor with a three-layer structure of a metal oxide positive electrode foil, electrolytic paper and a metal oxide negative electrode foil, and a metal aluminum lead strip is a lead-out end and is soaked in corresponding electrolyte to form a passive component for filtering. With the development of domestic and foreign industrial electronic and electrical equipment, the requirement of DC circuit output in a circuit is higher and higher, the demand of a capacitor is continuously increased, and the technical level of the modern capacitor becomes the bottleneck limiting the miniaturization development of the circuit in three components.

Among them, an electrolytic solution and an electrolytic paper are important materials affecting an electrolytic capacitor. When the power grid fluctuates or the 220V voltage is connected to the 380V voltage to cause overvoltage, the explosion-proof valve at the bottom of the high-voltage aluminum electrolytic capacitor for the conventional bus voltage input filtering can be exploded, a large amount of gasified liquid is sprayed inside, and if the liquid is accumulated in a high-voltage area of a circuit board, the liquid can cause the circuit to be ignited to cause fire due to the conductivity of the liquid. At present, the fire hazard problem caused by a high-voltage aluminum electrolytic capacitor is particularly prominent in the high-voltage frequency converter industry, the photovoltaic industry and the variable-frequency air conditioning industry.

The electrolytic paper is used as an adsorption carrier of the electrolyte, constitutes a cathode of the electrolytic capacitor together with the electrolyte, and plays a role of isolating the two electrode foils, and is also called as isolating paper, so that the electrolytic paper is required to have not only harsh physical requirements but also excellent electrical properties. The conventional electrolytic paper is made of pure wood pulp, a capacitor made of the electrolytic paper has lower breakdown voltage resistance, when overvoltage is generated, the conventional electrolyte is matched to cause the internal heating of the capacitor to increase the internal steam pressure so as to explode the explosion-proof valve to spray the electrolyte with a large amount of gas, the temperature during spraying reaches about 180 ℃ plus 250 ℃, the electrolyte causes the high-voltage area of the circuit board to be polluted and generates a conductive phenomenon, and serious people generate fire.

The electrolyte is the actual cathode of the aluminum electrolytic capacitor, the performance of the electrolyte plays a decisive role in the performance of the aluminum electrolytic capacitor, the existing electrolyte formula mainly comprises solute and solvent, and although the voltage resistance and the high temperature resistance of the electrolyte can be improved, the generation of hydrogen cannot be inhibited. Chinese patent 201510557960.2 (flame-retardant electrolyte and preparation method thereof) discloses that hydrogen can be reduced by adding a proper amount of nitroanisole, and although the formula can absorb hydrogen generated by the reaction of aluminum electrode foil and electrolyte and has obvious effects on improving performances such as high temperature resistance and flame retardance, the saturated vapor pressure in the product is still large under instantaneous over-voltage, and the gas sprayed out when the explosion-proof valve of the product is opened is very large.

Therefore, in order to solve the technical problem that the aluminum electrolytic capacitor with the explosion-proof valve is exploded to cause fire, the development of the aluminum electrolytic capacitor capable of automatically performing short-circuit protection under an overvoltage state is urgently needed, and the aluminum electrolytic capacitor can not be exploded even if the explosion-proof valve is arranged, and generates an automatic short-circuit protection effect.

Disclosure of Invention

In order to solve the technical problem that an explosion-proof valve of an aluminum electrolytic capacitor is exploded to cause fire, an overvoltage automatic short-circuit protection capacitor is provided. When the high-voltage overvoltage occurs to the aluminum electrolytic capacitor, the high-voltage aluminum electrolytic capacitor can be instantly protected by the dotted short circuit to cut off the path of continuous heating in the high-voltage aluminum electrolytic capacitor, so that the explosion-proof valve at the bottom is prevented from being exploded, and the fire problem caused by the ejection of electrolyte is avoided.

In order to achieve the purpose, the invention is realized by the following technical scheme:

overvoltage automatic short-circuit protection capacitor: the electrolytic paper comprises a wound body formed by winding a cathode foil, electrolytic paper and an anode foil with an oxide film dielectric formed on the surface in sequence, wherein a conductive polymer layer is arranged in the wound body, and a working electrolyte solution for immersing the wound body with the conductive polymer layer; the electrolytic paper is positioned between the cathode foil and the anode foil;

the working electrolyte comprises the following raw materials in percentage by weight: 70-80% of ethylene glycol, 6-10% of boric acid, 4-6% of ammonium pentaborate, 6-8% of 1,6-DDA, 1.5-4% of mannitol, 0.2-0.8% of ammonium hypophosphite and 0.5-2% of a polarizing agent;

the electrolytic paper comprises the following materials in percentage by weight: 40-70% of wood pulp, 25-55% of reinforcing fiber and 1-5% of nano regenerated fiber. The prepared capacitor has the function of overvoltage automatic short-circuit protection under higher voltage.

Further, the reinforcing fiber is hemp pulp fiber or cotton pulp fiber; the nanometer regenerated fibers are cellulose acetate nanofibers and/or nanometer cuprammonium fibers, the diameter of the fibers is 50-600 nm, the length-diameter ratio is larger than 2, the fibers can be prepared by an electrostatic spinning method, and the fibers have good liquid absorption and air permeability; the conductive polymer layer is a PEDOT/PSS conductive polymer film layer, and the wound body is repeatedly soaked and dried at high temperature by adopting a PEDOT/PSS water dispersion liquid to obtain the conductive polymer film.

Further, the working electrolyte comprises the following raw materials in percentage by weight: 77% of ethylene glycol, 8% of boric acid, 5.5% of ammonium pentaborate octahydrate, 6.5% of 1,6-DDA, 1.7% of mannitol, 0.3% of ammonium hypophosphite and 1% of a polarizing agent.

Still further, the polarizing agent is an organic compound containing a benzene ring, and the molecular structure of the polarizing agent comprises one or more functional groups of nitro, acetylene bonds, double bonds and sulfonic acid groups.

Preferably, the polarizing agent is one or more of p-nitrobenzenesulfonic acid, 3-nitrobenzenesulfonic acid, 4-nitrobenzeneacetylene, 1-ethynyl-2-nitrobenzene, 3-nitrostyrene and beta-nitrostyrene.

More preferably, the polarizing agent is p-nitrobenzenesulfonic acid or 3-nitrobenzenesulfonic acid.

Further, the preparation method of the working electrolyte comprises the following steps:

(1) heating ethylene glycol to a first degree, adding the residual raw materials without ammonium hypophosphite, and stirring until the raw materials are completely dissolved;

(2) heating up again to a second degree on the basis of the step (1), then adding the ammonium hypophosphite, and continuously stirring until the material is clarified;

(3) and (3) continuously raising the temperature on the basis of the step (2), carrying out third-degree heating and heat preservation, and cooling to obtain the working electrolyte.

Further, the temperature of the first degree of heating is 80-85 ℃; the temperature of the second degree of heating is 100 ℃; the temperature of the third degree heating is 120 +/-5 ℃, and the heat preservation time is 3-5 h.

The beneficial technical effects are as follows:

the working electrolyte of the invention comprises ethylene glycol as a solvent, boric acid, ammonium pentaborate octahydrate and 1,6-DDA as solutes, mannitol and hypophosphorous acid as additives and a polarizing agent. Boric acid and ammonium pentaborate in the working electrolyte of the invention are subjected to esterification reaction with ethylene glycol under heating, and the esterification reaction formula is B (OH)₃ + 2HO-CH₂-CH₂-OH→H[B(O₂C₂H₄)₂] + 3H₂O, generating borate and water, wherein the generated borate is used for providing oxygen ions for the electrolyte to repair the damaged oxide film on the surface of the anode; the 1,6-DDA macromolecular compound solution can be ionized into positive and negative ions with charging capacity, and the addition of the solution can increase the conductive repair capacity of the electrolyte and simultaneously increase the conductive repair capacity of the electrolyteThe sparking voltage is increased, so that the electrolyte has better conductive capability under certain working voltage; the addition of the additive ammonium hypophosphite can improve the formation efficiency of the electrolyte, and the ionized phosphoric acid can react with an aluminum oxide film on the surface of the capacitor anode foil to produce an aluminum phosphate conversion film with a stable structure, so that the voltage resistance stability of the capacitor product is improved; the polaroid can eliminate gas (mainly hydrogen) released by electrolyte in the working process, nitro contained in the molecular structure of the polaroid has a strong electron-withdrawing induction effect, or acetylene bonds and double bonds in the molecular structure can generate hydrogenation reaction with hydrogen, and sulfonic acid groups combined with a benzene ring structure can supplement and dope a conductive polymer layer (PEDOT/PSS) so as to prevent the problem of conductivity reduction of the conductive polymer layer caused by the fact that the conductive polymer layer is dedoped under the high-temperature working state of the capacitor, so that the problem of rapid ESR rise at high temperature is solved, and the sulfonic acid groups can instantly dope and supplement the conductive polymer layer to reduce the ESR rise degree.

The capacitor prepared by the working electrolyte of the invention can not explode the explosion-proof valve even under the overvoltage state of higher voltage, because the working electrolyte of the invention has better high temperature resistance and voltage-proof stability, can absorb hydrogen generated by heating under overpressure in the capacitor after working for a long time at high temperature so as to reduce the saturated vapor pressure in the capacitor, prolong the service life of the capacitor, and can generate automatic short-circuit protection action under overpressure so as to prevent the damage of circuit board pollution caused by capacitor explosion. After the electrolytic paper added with the nano-grade regenerated fibers absorbs working electrolyte, the electrolytic paper can be instantly clicked and penetrated under the overpressure of higher voltage to generate short circuit, and an internal heating path can be cut off in time, so that the phenomenon of overhigh internal saturated vapor pressure caused by overheat in a capacitor is avoided, the explosion of a bottom explosion-proof valve is prevented, the electrolyte is prevented from being sprayed out, and the effect of protecting the capacitor and a circuit board is achieved.

The aluminum electrolytic capacitor provided by the invention has the advantages that the electrolytic paper and the electrolyte are improved, so that the instantaneous point-like short circuit can be generated under the overvoltage state of higher voltage to prevent the explosion of the explosion-proof valve, thereby playing a role in protecting the capacitor and a circuit board, when the instantaneous point-like short circuit is generated under the overvoltage state of higher voltage, the way for continuously heating the capacitor can be immediately cut off, the phenomenon of overhigh internal saturated vapor pressure caused by overheating in the capacitor is avoided, and the explosion of the explosion-proof valve at the bottom can be prevented and the electrolyte can be prevented from being sprayed out. The principle of the effect is as follows: the nanometer regenerated fiber is added into the electrolytic paper, so that the electrolytic paper has better uniformity, the breakdown voltage consistency of the electrolytic paper is greatly improved, the breakdown voltage deviation of the electrolytic paper cannot exceed 60V, the breakdown voltage deviation of the original wood pulp fiber electrolytic paper maximally exceeds 380V, the improved electrolyte is matched on the basis of improving the breakdown voltage consistency of the electrolytic paper, the capacitor can generate instant point-like short circuit under the overpressure of higher voltage, the way of continuously heating in the capacitor is cut off immediately, so that the overheating phenomenon does not occur in the capacitor, and the two cooperate with each other to generate the overvoltage self-protection function under the higher voltage, thereby playing the role of protecting the capacitor and a circuit board, preventing the explosion of a bottom explosion-proof valve and stopping the ejection of the electrolyte. The meaning of instantaneous punctiform short circuit is: after the nano-grade regenerated fibers are added into the conventional electrolytic paper, the uniformity is improved, the electrolytic paper is used as an adsorption carrier of electrolyte, when the electrolyte is over-pressurized, the pressure resistance on the electrolytic paper is instantly reduced, and the electrolytic paper is punctured to generate punctiform micropores, namely, instant punctiform short circuit is generated. And the conventional electrolytic paper can explode violently after being overpressured, and uncertain risks such as surface breakdown of an aluminum shell or explosion rupture of a bottom explosion-proof valve can occur.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the invention, its application, or uses. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Unless specifically stated otherwise, the numerical values set forth in these examples do not limit the scope of the invention. Techniques, methods known to those of ordinary skill in the relevant art may not be discussed in detail, but are intended to be part of the specification where appropriate. In all examples shown and discussed herein, any particular value should be construed as merely illustrative, and not limiting. Thus, other examples of the exemplary embodiments may have different values.

The experimental methods of the following examples, which are not specified under specific conditions, are generally determined according to national standards; if no corresponding national standard exists, the method is carried out according to the universal international standard or the standard requirement proposed by related enterprises. Unless otherwise indicated, all parts are parts by weight and all percentages are percentages by weight.

The conductive polymer layers in the following examples and comparative examples are PEDOT/PSS conductive polymer film layers. And repeatedly dipping the wound body by PEDOT/PSS aqueous dispersion and drying at high temperature of about 160 ℃ to obtain the wound body.

Example 1

The working electrolyte of the capacitor with overvoltage automatic short-circuit protection comprises the following raw materials in percentage by weight: 74.5 percent of glycol, 10 percent of boric acid, 5 percent of ammonium pentaborate octahydrate, 6 percent of 1,6-DDA, 3.8 percent of mannitol, 0.2 percent of ammonium hypophosphite and 0.5 percent of polarizing agent p-nitrobenzenesulfonic acid.

The preparation method of the working electrolyte comprises the following steps:

(1) heating ethylene glycol to 80-85 ℃, sequentially adding boric acid, ammonium pentaborate octahydrate, 1,6-DDA and mannitol, and stirring until the materials are completely dissolved;

(2) heating to 100 ℃ on the basis of the step (1), adding ammonium hypophosphite, and continuously stirring until the material is clear;

(3) and (3) continuously heating to 120 +/-5 ℃ on the basis of the step (2), preserving heat for 4 hours, and cooling to obtain the working electrolyte.

Example 2

The working electrolyte of the capacitor with overvoltage automatic short-circuit protection comprises the following raw materials in percentage by weight: 77% of ethylene glycol, 8% of boric acid, 5.5% of ammonium pentaborate octahydrate, 6.5% of 1,6-DDA, 1.7% of mannitol, 0.3% of ammonium hypophosphite and 1% of polarizing agent 3-nitrobenzenesulfonic acid.

The working electrolyte was prepared in the same manner as in example 1.

Example 3

The working electrolyte of the capacitor with overvoltage automatic short-circuit protection comprises the following raw materials in percentage by weight: 78.5 percent of glycol, 6 percent of boric acid, 4.5 percent of ammonium pentaborate octahydrate, 7.5 percent of 1,6-DDA, 1.5 percent of mannitol, 0.5 percent of ammonium hypophosphite and 1.5 percent of polarizing agent 1-ethynyl-2-nitrobenzene.

The working electrolyte was prepared in the same manner as in example 1.

Comparative example 1

The working electrolyte of this comparative example was: 78% of ethylene glycol, 8% of boric acid, 5.5% of ammonium pentaborate octahydrate, 6.5% of 1,6-DDA, 1.7% of mannitol and 0.3% of ammonium hypophosphite. No polarising agent was added.

The working electrolyte was prepared in the same manner as in example 1.

The parameters of the working electrolytes prepared in examples 1 to 3 and comparative example 1 are shown in table 1.

Table 1 parameters of working electrolytes of examples 1-3, comparative example 1 configurations

Example 4

The working electrolyte of example 1 was applied to the production of a high-voltage aluminum electrolytic capacitor (450V 470 μ F, size Φ 35 x 45) comprising a roll wound in this order of a cathode foil, an electrolytic paper, an anode foil having an oxide film dielectric formed on the surface thereof, a conductive polymer layer in the roll, and the working electrolyte of this example impregnated with the roll having the conductive polymer layer; the electrolytic paper is positioned between the cathode foil and the anode foil;

the electrolytic paper comprises the following materials in percentage by weight: 60% of wood pulp, 40% of hemp pulp fiber and electrolytic paper manufacturing equipment which adopts rotary screen and long screen composite equipment.

Example 5

The high-voltage aluminum electrolytic capacitor of this example was produced in the same manner as in example 4, except that the working electrolyte of example 2 was used.

Example 6

The high-voltage aluminum electrolytic capacitor of this example was produced in the same manner as in example 4, except that the working electrolyte of example 3 was used.

Example 7

The working electrolyte of example 2 was applied to the production of a high-voltage aluminum electrolytic capacitor (450V 470 μ F, size Φ 35 x 45) comprising a roll wound in this order from a cathode foil, an electrolytic paper, an anode foil having an oxide film dielectric formed on the surface thereof, a conductive polymer layer in the roll, and the working electrolyte of example 1 in which the roll having the conductive polymer layer was impregnated; the electrolytic paper is positioned between the cathode foil and the anode foil;

the electrolytic paper comprises the following raw materials in percentage by weight: 60% of wood pulp, 37% of hemp pulp fiber and 3% of cellulose acetate nanofiber, and the electrolytic paper is manufactured by adopting a rotary screen and fourdrinier combined device.

Preparing cellulose acetate nano-fibers: dissolving chemically pure cellulose acetate in formic acid, stirring for 12h, preparing a spinning solution, and performing electrostatic spinning to obtain the cellulose acetate nanofiber, wherein the diameter of the cellulose acetate nanofiber is 300-600nm, and crushing a membrane obtained by electrostatic spinning until the length-diameter ratio is more than 2.

Example 8

The working electrolyte of example 2 was used to prepare a high-voltage aluminum electrolytic capacitor (450V 470 μ F, size Φ 35 x 45) comprising a roll wound in this order from a cathode foil, an electrolytic paper, and an anode foil having an oxide film dielectric formed on the surface thereof, a conductive polymer layer in the roll, and the working electrolyte of example 2 in which the roll having the conductive polymer layer was impregnated; the electrolytic paper is positioned between the cathode foil and the anode foil;

the electrolytic paper comprises the following raw materials in percentage by weight: 60% of wood pulp, 39% of jute pulp fiber and 1% of cellulose acetate nanofiber, and the electrolytic paper is manufactured by adopting rotary screen and fourdrinier combined equipment.

Example 9

The working electrolyte of example 2 was used to prepare a high-voltage aluminum electrolytic capacitor (450V 470 μ F, size Φ 35 x 45) comprising a roll wound in this order from a cathode foil, an electrolytic paper, and an anode foil having an oxide film dielectric formed on the surface thereof, a conductive polymer layer in the roll, and the working electrolyte of example 3 in which the roll having the conductive polymer layer was impregnated; the electrolytic paper is positioned between the cathode foil and the anode foil;

the electrolytic paper comprises the following raw materials in percentage by weight: 60% of wood pulp, 35% of hemp pulp fiber and 5% of cellulose acetate nanofiber, and the electrolytic paper is manufactured by adopting a rotary screen and fourdrinier combined device.

Comparative example 2

The high voltage aluminum electrolytic capacitor of this comparative example was prepared the same as example 4 except that the working electrolyte of comparative example 1 was used.

Comparative example 3

The high voltage aluminum electrolytic capacitor of this comparative example was prepared in the same manner as in example 7, except that the working electrolyte of comparative example 1 was used.

The compositions of the electrolytic paper and the electrolytic solution in the capacitors of examples 4 to 9 and comparative examples 2 to 3 are shown in Table 2.

TABLE 2 compositions of electrolytic paper and electrolytic solution in capacitors of examples 4 to 9 and comparative examples 2 to 3

(Note: 74.5% of ethylene glycol, 10% of boric acid, 5% of ammonium pentaborate octahydrate, 6% of 1,6-DDA, 3.8% of mannitol, 0.2% of ammonium hypophosphite and 0.5% of polarizing agent p-nitrobenzenesulfonic acid; working electrolyte in example 1.

Note two: 77% of ethylene glycol, 8% of boric acid, 5.5% of ammonium pentaborate octahydrate, 6.5% of 1,6-DDA, 1.7% of mannitol, 0.3% of ammonium hypophosphite and 1% of polarizing agent 3-nitrobenzenesulfonic acid; example 2 working electrolyte.

Third, note: 78.5% of ethylene glycol, 6% of boric acid, 4.5% of ammonium pentaborate octahydrate, 7.5% of 1,6-DDA, 1.5% of mannitol, 0.5% of ammonium hypophosphite and 1.5% of a polarizing agent 1-ethynyl-2-nitrobenzene; example 3 working electrolyte.

And D, injecting: 78% of ethylene glycol, 8% of boric acid, 5.5% of ammonium pentaborate octahydrate, 6.5% of 1,6-DDA, 1.7% of mannitol and 0.3% of ammonium hypophosphite; comparative example 1 working electrolyte. )

Test example 1

The capacitors of examples 4 to 6 and comparative example 2 above were subjected to durability tests by applying a rated dc voltage at a high temperature of 105 c, and 5 capacitors of each of examples and comparative examples were fabricated and subjected to measurement tests of electrical parameters of the capacitors, and the average values were obtained. In the measurement of electrical parameters of the capacitor, capacitance (Cap, 25 ℃ C. 120 Hz), loss tangent (Df, 25 ℃ C. 120 Hz), and equivalent series resistance (ESR, 25 ℃ C. 100 KHz) were measured using an LCR tester, model 4284A, manufactured by Agilent, and leakage current (Lc, 25 ℃ C. applied with a rated voltage of 35V for 1 minute) was measured using a leakage current tester, model TH2689A, manufactured by Tongh. mu.i. The measured data are shown in Table 3.

TABLE 3 durability test of aluminum electrolytic capacitors (450V 470. mu.F) of examples 4 to 6 and comparative example 2

As is clear from Table 3, in examples 4 to 6, when different proportions of the polarizing agents having different functional groups were added, the vapor pressure in the product was significantly different and the degree of swelling at the bottom was different after the 5000-hour high-temperature life test. The capacitor of example 4 has an ESR increase of about 74.6% and a normal product appearance after 5000 hours of operation at 105 ℃, the capacitor of example 5 has an ESR increase of about 79.3% and a normal product appearance after 5000 hours of operation at 105 ℃, and the capacitor of example 6 has an ESR increase of about 104.4% and a slight bottom-out in product appearance after 5000 hours of operation at 105 ℃, because the polarizing agent of example 6 does not contain a benzene ring structure containing a sulfonic acid group in the molecular structure of the polarizing agent, and when the polarizing agent of a benzenesulfonic acid structure is not contained, the ESR increase is large due to partial dedoping of the conductive polymer layer at high temperature, gas generation of the electrolyte may be increased, and the electron withdrawing effect of an acetylene bond is small relative to that of a nitro group, so that other absorption rates are relatively small compared with those of examples 4 and 5 (i.e., the internal vapor pressure of example 6 is relatively smaller than that of example 4 and example 4, 5) even though the amount of the polarizing agent used in example 3 is large, the ESR still rises more than 100% and the product appearance has a slight bottom.

And the electrolyte of the capacitor in the comparative example 2 is not added with the polarizing agent, so that gas generated inside the capacitor after the high-temperature test of the product cannot be digested and absorbed, the bottom explosion-proof valve is exploded, and the electrolyte is sprayed out.

The capacitors of examples 4 to 6 and comparative example 2 were subjected to an overvoltage resistance test by starting the pressurization at 500V and increasing 10V every 1 minute until the highest voltage at which the product failed was taken as the breakdown voltage (or overvoltage resistance), and the test results are shown in table 4 below.

TABLE 4 overvoltage resistance of aluminum electrolytic capacitors (450V 470. mu.F) of examples 4 to 6 and comparative example 2

As can be seen from table 4, the working electrolytes of examples 1 to 3 of the present invention can improve the breakdown voltage resistance of the high-voltage electrolytic capacitor, and can satisfy the automatic short-circuit protection effect under overvoltage. The polaroid containing the electron-withdrawing group is added into the working electrolyte, so that the gas generated in the operation process of the capacitor can be absorbed, the saturated vapor pressure of the working electrolyte is reduced, the internal point breakdown is generated under the overpressure condition of the capacitor, and the internal heating path of the capacitor is cut off immediately, so that the explosion of the bottom explosion-proof valve is prevented, and the electrolyte is prevented from being sprayed out.

Test example 2

The aluminum electrolytic capacitors of examples 7 to 9 and comparative example 3 were subjected to a 105 ℃ load accelerated life test according to AEC-Q200 for 5000 hours, and then an equivalent series resistance (ESR, 23 ℃ C. 100 KHz) was measured using an Agilent model 4284A LCR tester; the breakdown voltage resistance test method is that 10V is added every 1 minute from 500V until the highest voltage of the product is failed; in each example and each comparative example, 5 corresponding aluminum electrolytic capacitors were manufactured and tested, and the test results were averaged, and the specific data are shown in table 5.

TABLE 5 Performance of aluminum electrolytic capacitors of examples 7 to 9 and comparative example 3

(Note: high-voltage electrolytic capacitor with aluminum electrolytic capacitor specification of 450V470 muF.)

As shown in Table 5, the breakdown voltage of the capacitors of examples 7-9 is higher than that of examples 4-6, and it can be seen that the addition of the nano-sized regenerated fibers further improves the breakdown voltage of the capacitors, and the appearance of the capacitor at the time of product failure under overpressure is relatively stable without obvious abnormality. After the product is operated at 105 ℃ for 5000 hours, the ESR rise rate is relatively stable and is not more than 1 time, and the appearance of the product is not obviously abnormal.

Comparing example 5 with example 8, it is known that the breakdown voltage of the electrolytic paper under overvoltage can be improved by adding the nano regenerated fibers into the electrolytic paper, and the electrolyte of the invention can reduce the internal saturated vapor pressure, so that the interior of the product instantaneously undergoes punctiform breakdown after overvoltage, i.e. the automatic short-circuit protection function is generated and potential adverse problems such as explosion of an explosion-proof valve are avoided. The nanometer regenerated fiber and the unmodified electrolyte are added into the conventional electrolytic paper (comparative example 3), although the improvement of the uniformity of the electrolytic paper is beneficial to improving the breakdown voltage resistance, the electrolytic paper is used as an adsorption carrier of the electrolyte, and when the electrolyte is over-pressurized, the electrolyte in the comparative example 3 still has the problem of overlarge saturated vapor pressure and the problem of explosion of an explosion-proof valve. The conventional electrolytic paper + unmodified electrolyte (comparative example 2) may have violent explosion after overpressure, and uncertain risks such as surface breakdown of an aluminum shell or explosion rupture of a bottom explosion-proof valve may occur, so that the explosion rupture of the explosion-proof valve occurs when the capacitor is under overpressure.

The normal use voltage of the high-voltage aluminum electrolytic capacitor manufactured by the electrolytic paper and the electrolyte is 450V, the allowable surge voltage is 500V, and the short-circuit protection voltage is controlled to be 560 +/-30V.

The invention carries out explosion suppression of an explosion-proof valve on the capacitor from two aspects, on one hand, the working electrolyte of the invention can be independently adopted to realize the function of automatic short-circuit protection under overpressure, and the electrolyte absorbs gas generated in the operation process of the capacitor through the added polarizing agent so as to reduce the internal saturated vapor pressure; on the other hand, the electrolyte and the electrolytic paper are simultaneously improved to realize the function of automatic short-circuit protection under overpressure, the nano regenerated fibers are added into the electrolytic paper to improve the uniformity of the electrolytic paper so as to improve the breakdown-resistant voltage, after the improved electrolytic paper absorbs the improved electrolyte, the internal saturated vapor pressure is reduced, the breakdown-resistant voltage is improved, the breakdown-resistant voltage is further improved by combining the electrolytic paper, so that the capacitor can generate instant point-like short circuit under overpressure of higher voltage, the way of continuous heating in the capacitor can be immediately cut off so that the overheating phenomenon does not occur in the capacitor, the two cooperate with each other to generate the function of overvoltage self-protection under higher voltage, the explosion of the bottom explosion-proof valve is prevented, and the problem of electrolyte ejection is avoided.

The working electrolyte or the combination of the electrolytic paper and the electrolyte has instant point breakdown in the product under the over-voltage of higher voltage and can cut off the internal heating path in time, so that the phenomenon of overhigh internal saturated vapor pressure caused by overheating in the capacitor is avoided, the explosion of a bottom explosion-proof valve is prevented, the electrolyte is prevented from being sprayed out, and the capacitor and a circuit board are protected.

The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art should be considered to be within the technical scope of the present invention, and the technical solutions and the inventive concepts thereof according to the present invention should be equivalent or changed within the scope of the present invention.

Claims

1. An overvoltage self-short-circuit protection capacitor comprising a wound body formed by winding a cathode foil, an electrolytic paper, and an anode foil having an oxide film dielectric formed on the surface thereof in this order, the wound body having a conductive polymer layer therein, and a working electrolyte solution for impregnating the wound body having the conductive polymer layer therein; the electrolytic paper is positioned between the cathode foil and the anode foil;

the electrolytic paper comprises the following materials in percentage by weight: 40-70% of wood pulp, 25-55% of reinforcing fiber and 1-5% of nano regenerated fiber.

2. The overvoltage crowbar protection capacitor of claim 1 wherein said reinforcing fibers are hemp pulp fibers or cotton pulp fibers; the nanometer regenerated fibers are cellulose acetate nanofibers and/or nanometer cuprammonium fibers, the diameter of the fibers is 50-600 nm, and the length-diameter ratio of the fibers is more than 2; the conductive polymer layer is a PEDOT/PSS conductive polymer film layer.

3. The overvoltage automatic short-circuit protection capacitor according to claim 1, wherein said working electrolyte comprises the following raw materials in weight percent: 77% of ethylene glycol, 8% of boric acid, 5.5% of ammonium pentaborate octahydrate, 6.5% of 1,6-DDA, 1.7% of mannitol, 0.3% of ammonium hypophosphite and 1% of a polarizing agent.

4. The overvoltage automatic short-circuit protection capacitor according to claim 3, wherein the polarization agent is an organic compound containing a benzene ring, and the molecular structure of the polarization agent comprises one or more functional groups selected from a nitro group, an acetylene bond, a double bond and a sulfonic group.

5. The overvoltage crowbar protection capacitor of claim 4 wherein the polarizer is one or more of p-nitrobenzenesulfonic acid, 3-nitrobenzenesulfonic acid, 4-nitrobenzeneacetylene, 1-ethynyl-2-nitrobenzene, 3-nitrostyrene, β -nitrostyrene.

6. The overvoltage automatic short-circuit protection capacitor according to any one of claims 3 to 5, wherein the working electrolyte is prepared by a method comprising the steps of:

7. The overvoltage crowbar protection capacitor of claim 6 wherein the first degree of heating is at a temperature of 80-85 ℃; the temperature of the second degree of heating is 100 ℃; the temperature of the third degree heating is 120 +/-5 ℃, and the heat preservation time is 3-5 h.