WO2018107813A1

WO2018107813A1 - Aluminum electrolytic capacitor

Info

Publication number: WO2018107813A1
Application number: PCT/CN2017/099761
Authority: WO
Inventors: 季张林; 丁继华; 徐永华; 徐志友
Original assignee: 南通江海电容器股份有限公司
Priority date: 2016-12-16
Filing date: 2017-08-30
Publication date: 2018-06-21
Also published as: CN106783176A

Abstract

Provided is an aluminum electrolytic capacitor, comprising an outer shell (1), an inner shell (2), a sealing material (3) and a core (4). The sealing material (3) is put into the inner shell (2) to form a seal, and the inner shell (2) and the outer shell (1) are assembled in an associated manner. The core (4) is disposed inside the inner shell (2) and comprises an electrolytic paper (401), a positive electrode foil piece (402), a negative electrode foil piece (403), a positive lead wire (404) and a negative lead wire (405). One side of the positive electrode foil piece (402) and one side of the negative electrode foil piece (403) are respectively connected to the electrolytic paper (401). The positive lead wire (404) is fixed on the other side of the positive electrode foil piece (402), and the negative lead wire (405) is fixed on the other side of the negative electrode foil piece (403). Surface-extended and capacity-increased micropores are formed on the surface of the negative lead wire (405) to form an oxide film. Sparkover breakdown of the capacitor during use is avoided, thereby obviously improving the stability and service life of the capacitor.

Description

Aluminum electrolytic capacitors

Technical field

The invention belongs to the technical field of capacitors, and in particular to an aluminum electrolytic capacitor.

Background technique

As shown in Fig. 1, in the conventional aluminum electrolytic capacitor, the positive and negative foils and the electrolytic paper are directly connected, and then taken out by the lead wires. In the conventional capacitor, the actual amount of the anode is stored in the electrolytic capacitor. It is larger than the cathode.

As shown in Fig. 2, in the figure, the Ca capacity is composed of an anodized film and an electrolytic paper impregnated with an electrolyte; Ra can be regarded as an insulation resistance of an anodized film; Cc capacitance is a cathode oxide film and impregnation electrolysis The composition of the liquid electrolytic paper, Rc can be regarded as the insulation resistance of the cathode oxide film (Rc also includes the composite resistance of the electrolyte and electrolytic paper).

When a DC voltage V is applied to the circuit of Fig. 2, the voltages across C and Cc are Va and Vc, respectively, and V = Va + Vc, and Va / Vc = Ra / Rc.

In addition, in the ideal case, Va / Vc = Ra / Rc = Cc / Ca, when the anode and cathode are stored in the same amount of electricity, but the anodized film is specially oxidized, the Ra value is very high, and the cathode oxide film Very thin, Rc value is very small, therefore, the Ra/Rc ratio is extremely large. If you want Cc/Ca to obtain the same ratio as Ra/Rc at this time, the Cc value must be very very large. In the existing capacitor, Both satisfy the following formula:

Ra / Rc > Cc / Ca, that is: Va / Vc > Cc / Ca, into: Va * Ca > Vc * Cc.

Because: Qa = Va * Ca; Qc = Vc * Cc, you get: Qa > Qc.

This shows that in an actual electrolytic capacitor, the anode stores a larger amount of electricity than the cathode.

Therefore, the actual capacitor storage capacity is shown in Figure 3:

At this time, if the charging voltage is V volt (Note: for the flash capacitor, the V value is the DC voltage; for the capacitor applied to the large ripple current, the V value is the peak value of the ripple voltage), the capacitor is short-circuited (extremely discharged) ), as shown in Figure 4, a parallel form of two capacities Ca and Cc is formed:

The voltage between the two ends forms a Vc' due to the discharge, and the discharge is performed only on the Qc where the charge is relatively small, and Qa-Qc is the charge remaining without being discharged.

Therefore, the residual voltage Vc' is determined by Ca + Cc and Qa - Qc, and the formula is as follows:

Formula 1:

From the above formula, the voltage (Vc') applied to the cathode oxide film may be high during discharge (relative to the natural oxide film withstand voltage of about 1 V), which causes oxidation of the negative electrode and gas generation inside the capacitor. And other undesirable phenomena. Therefore, in the discharge of the capacitor, in order not to cause an oxidation reaction, the withstand voltage V' on the cathode Cc must satisfy the following formula 2:

Formula 2:

Since V=Va+Vc, Equation 2 can be further reduced to Equation 3:

Formula 3:

At the time of discharge, even if a voltage Vc' is applied to the cathode, an oxidation reaction does not occur, and in order to satisfy such a requirement, a cathode foil having a high specific volume (large Cc capacity) or a cathode foil or a lead wire may be used in advance. A higher formation voltage (Vc is large) is formed. However, even if such a condition is satisfied, a voltage flashover will eventually occur because the capacitor has a large ripple current or a short time voltage difference, because of the capacitance on the lead plate or lead strip of the negative electrode of the capacitor. (Unit area capacity) is very low. According to Equation 3, the Vc' on the lead plate or lead strip will be very high, that is, when discharged, a high voltage is generated on the lead plate or the lead strip. This high pressure is reversed for the negative electrode and is pulsed. After a period of time, an oxide film is gradually formed on the negative electrode, and the gas inside the capacitor is more and more, and the hydrogen absorbing agent in the electrolyte is continuously absorbed. The results have two conditions: First, the ripple current at the beginning is extremely large, so that the Vc' voltage is very high, the oxidation reaction is intense and the voltage jumps quickly; second, the ripple current is much larger than normal, under the Vc' voltage. The oxide film is gradually formed, and as time passes, the capacity Cc of the negative electrode continuously decreases, and the voltage of Vc' rises continuously, and a voltage flashover occurs after reaching a certain critical point.

At present, the existing technical solution is to add a connection compatibilizing device to the negative lead strip, although this method can solve The negative electrode jumps, but it increases the complexity of the production equipment.

Summary of the invention

The technical problem to be solved by the present invention is to provide an aluminum electrolytic capacitor which avoids the occurrence of flashover breakdown of the capacitor during use without increasing the complexity of the existing equipment.

The technical solution adopted by the present invention to solve the technical problem thereof is to provide an aluminum electrolytic capacitor comprising an outer casing, an inner casing, a sealing material and a core package, wherein the sealing material is filled into the inner casing to form a seal, and the inner casing and the outer casing are assembled. The core package is disposed inside the inner casing, and the core package comprises an electrolytic paper, a positive electrode foil, a negative electrode foil, a positive electrode lead wire and a negative electrode lead wire, one side of the positive electrode foil piece and one side of the negative electrode foil piece Connected to the electrolytic paper respectively, the positive electrode lead wire is fixed on the other side of the positive electrode foil, the negative electrode lead wire is fixed on the other side of the negative electrode foil, and the surface of the negative electrode lead wire is formed with a surface expansion and capacity expansion. Micropores and form an oxide film.

As a preferred embodiment of the present invention, the surface of the negative electrode lead wire is subjected to purification etching to form micropores.

As another preferred embodiment of the present invention, the surface of the negative electrode lead wire is electrochemically etched to form micropores.

As another preferred embodiment of the present invention, the anode lead wire is subjected to a chemical conversion treatment to form an oxide film on the surface.

As another preferred embodiment of the present invention, the positive electrode foil and the negative electrode foil are crimped and then wound on an electrolytic paper.

As another preferred embodiment of the present invention, the positive electrode foil and the negative electrode foil are wound on the electrolytic paper by cold press welding.

As another preferred embodiment of the present invention, the positive electrode lead wire and the negative electrode lead wire are lead plates or lead wires.

As another preferred embodiment of the present invention, the positive electrode lead wire and the negative electrode lead wire are respectively connected to the positive electrode foil piece and the negative electrode foil piece by cold press welding.

Beneficial effect

The invention forms the micropores of the surface by expanding and increasing the capacity of the negative electrode lead wire, and forms an oxide film on the surface by chemical conversion treatment, thereby achieving a stronger voltage withstand effect and avoiding the occurrence of flashover breakdown, thereby obviously The stability of high capacitor applications increases service life.

DRAWINGS

FIG. 1 is an internal structural view of a conventional capacitor core package.

Figure 2 is an equivalent circuit diagram of the capacitor during charging and discharging.

Figure 3 is a graph of the actual charge stored by the capacitor.

Figure 4 is a diagram showing the parallel form of two capacities Ca and Cc.

Figure 5 is a schematic view of the structure of the present invention.

Fig. 6 is a view showing the internal structure of the core package of the present invention.

detailed description

The invention is further illustrated below in conjunction with specific embodiments. It is to be understood that the examples are not intended to limit the scope of the invention. In addition, it should be understood that various changes and modifications may be made by those skilled in the art in the form of the present invention.

An aluminum electrolytic capacitor as shown in FIGS. 4 and 5 includes a casing 1, an inner casing 2, a sealing material 3, and a core package 4. The sealing material 3 is fitted into the inner casing 2 to form a seal, the inner casing 2 is fitted with the outer casing 1, and the core package 4 is disposed inside the inner casing 2.

The core package 4 includes an electrolytic paper 401, a positive electrode foil 402, a negative electrode foil 403, a positive electrode lead wire 404, and a negative electrode lead wire 405. One side of the positive electrode foil 402 and one side of the negative electrode foil 403 are respectively connected to the electrolytic paper 401, and the positive electrode foil 402 and the negative electrode foil 403 are wound on the electrolytic paper 401 by riveting or cold-press welding. The positive electrode lead wire 404 is fixed to the other side of the positive electrode foil 402, the negative electrode lead wire 405 is fixed to the other side of the negative electrode foil 403, and the positive electrode lead wire 404 and the negative electrode lead wire 405 are lead plates or lead wires, and the positive electrode lead wires 404 are provided. The negative electrode lead wires 405 are connected to the positive electrode foil 402 and the negative electrode foil 403 by cold press welding, respectively.

The surface of the negative electrode lead wire 405 is subjected to purification etching or electrochemical etching to form a microporous cavity which is expanded and enlarged, thereby increasing the surface area. After the surface of the negative electrode lead strip 405 is expanded and expanded, it is subjected to a chemical conversion treatment to form an oxide film on the surface thereof, and has a withstand voltage capability. Through the above improvements, the occurrence of flashover breakdown is avoided, thereby significantly improving the stability of the capacitor application and increasing the service life.

Claims

An aluminum electrolytic capacitor comprising a casing (1), an inner casing (2), a sealing material (3) and a core package (4), the sealing material (3) being fitted into the inner casing (2) to form a seal, the inner The shell (2) is assembled with the outer casing (1), the core package (4) is disposed inside the inner casing (2), and the core package (4) comprises electrolytic paper (401), positive electrode foil (402), and negative electrode. a foil (403), a positive lead wire (404), and a negative lead wire (405), one side of the positive electrode foil (402) and one side of the negative electrode foil (403) are respectively connected to the electrolytic paper (401). The positive lead wire (404) is fixed on the other side of the positive electrode foil (402), and the negative electrode lead wire (405) is fixed on the other side of the negative electrode foil (403), characterized in that the negative electrode is taken out The surface of the wire (405) is formed with expanded pores and enlarged pores, and an oxide film is formed.
An aluminum electrolytic capacitor according to claim 1, wherein the surface of said negative electrode lead wire (405) is subjected to purification etching to form micropores.
An aluminum electrolytic capacitor according to claim 1, wherein the surface of said negative electrode lead wire (405) is subjected to electrochemical etching to form micropores.
An aluminum electrolytic capacitor according to claim 1, 2 or 3, wherein said negative electrode lead wire (405) is subjected to a chemical conversion treatment to form an oxide film on the surface.
An aluminum electrolytic capacitor according to claim 1, wherein said positive electrode foil (402) and said negative electrode foil (403) are crimped and then wound on electrolytic paper (401).
An aluminum electrolytic capacitor according to claim 1, wherein said positive electrode foil (402) and said negative electrode foil (403) are cold-welded and then wound on electrolytic paper (401).
An aluminum electrolytic capacitor according to claim 1, wherein said positive electrode lead wire (404) and said negative electrode lead wire (405) are lead plates or lead wires.
An aluminum electrolytic capacitor according to claim 1, wherein said positive electrode lead wire (404) and said negative electrode lead wire (405) are respectively cold pressed by a positive electrode foil (402) and a negative electrode foil (403). )connection.