CN113178335A - High specific volume, ultra-thin type negative electrode foil and liquid aluminum electrolytic capacitor - Google Patents

High specific volume, ultra-thin type negative electrode foil and liquid aluminum electrolytic capacitor Download PDF

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CN113178335A
CN113178335A CN202110473693.6A CN202110473693A CN113178335A CN 113178335 A CN113178335 A CN 113178335A CN 202110473693 A CN202110473693 A CN 202110473693A CN 113178335 A CN113178335 A CN 113178335A
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negative electrode
specific volume
electrode foil
resin
aluminum substrate
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CN113178335B (en
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吕上
朱金勇
蒋武斌
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Anhui Nanuo Foil Co ltd
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Anhui Nanuo Foil Co ltd
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
    • H01G9/00—Electrolytic capacitors, rectifiers, detectors, switching devices, light-sensitive or temperature-sensitive devices; Processes of their manufacture
    • H01G9/004—Details
    • H01G9/04—Electrodes or formation of dielectric layers thereon
    • H01G9/048—Electrodes or formation of dielectric layers thereon characterised by their structure
    • H01G9/055—Etched foil electrodes
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23F—NON-MECHANICAL REMOVAL OF METALLIC MATERIAL FROM SURFACE; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL; MULTI-STEP PROCESSES FOR SURFACE TREATMENT OF METALLIC MATERIAL INVOLVING AT LEAST ONE PROCESS PROVIDED FOR IN CLASS C23 AND AT LEAST ONE PROCESS COVERED BY SUBCLASS C21D OR C22F OR CLASS C25
    • C23F1/00—Etching metallic material by chemical means
    • C23F1/10—Etching compositions
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    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
    • H01G9/00—Electrolytic capacitors, rectifiers, detectors, switching devices, light-sensitive or temperature-sensitive devices; Processes of their manufacture
    • H01G9/0029—Processes of manufacture
    • H01G9/0032—Processes of manufacture formation of the dielectric layer
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
    • H01G9/00—Electrolytic capacitors, rectifiers, detectors, switching devices, light-sensitive or temperature-sensitive devices; Processes of their manufacture
    • H01G9/004—Details
    • H01G9/04—Electrodes or formation of dielectric layers thereon
    • H01G9/042—Electrodes or formation of dielectric layers thereon characterised by the material
    • H01G9/045—Electrodes or formation of dielectric layers thereon characterised by the material based on aluminium
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
    • H01G9/00—Electrolytic capacitors, rectifiers, detectors, switching devices, light-sensitive or temperature-sensitive devices; Processes of their manufacture
    • H01G9/004—Details
    • H01G9/07—Dielectric layers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
    • H01G9/00—Electrolytic capacitors, rectifiers, detectors, switching devices, light-sensitive or temperature-sensitive devices; Processes of their manufacture
    • H01G9/145—Liquid electrolytic capacitors
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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Abstract

The invention relates to a high-specific-volume ultra-thin negative electrode foil and a liquid aluminum electrolytic capacitor, wherein the negative electrode foil comprises an aluminum base material and a dielectric layer, holes are formed on the surface of the aluminum base material by etching, the dielectric layer is a coating rolled on the holes and the surface of the aluminum base material, the slurry of the coating is prepared by selecting dielectric oxide particles of valve metal, organic resin, dispersant and solvent according to the mass ratio of 1: 0.1-1: 0.0001-0.01: 5-50, the slurry is coated on the surface of the aluminum base material with the holes, and is dried in a high-temperature furnace at 100-300 ℃, and then is carbonized under the conditions of oxygen isolation and temperature control at 400-600 ℃ to form a coating before rolling. The negative electrode foil obtained by the etching and rolling process not only reduces the resistance of the coating and increases the capacity of the capacitor, but also has thin thickness, strong conductivity, strong adhesiveness and strong safety.

Description

High specific volume, ultra-thin type negative electrode foil and liquid aluminum electrolytic capacitor
The application is a production process of a negative electrode foil and divisional application of the negative electrode foil and a liquid aluminum electrolytic capacitor, wherein the application date is 2019, 03 and 20, and the application number is 201910214466.4.
Technical Field
The invention belongs to the technical field of capacitors, and particularly relates to a high-specific-volume ultrathin negative electrode foil and a liquid aluminum electrolytic capacitor.
Background
As is well known, miniaturization of electronic components has been an industry hotspot. In recent years, various smart terminals have been rapidly developed in the fields of consumer electronics for consumer use, industrial manufacturing, automotive electronics, military communications, and the like. The realization of these terminal functions is free from component support without miniaturization, and the realization of more functions in a limited space has become a necessary trend, and the demand for component miniaturization will continue to continue.
The capacitor is an essential device in an electronic circuit as a basic component, is generally used for functions of AC resistance direct current, filtering, bypass, coupling and quick charge and discharge, can be used for reducing ripples and absorbing noise generated by a switching regulator, and can also be used for post-stage voltage stabilization to improve the stability and transient response capability of equipment. No ripple noise or residual jitter should appear in the power supply output. Among various types of capacitors, the liquid aluminum electrolytic capacitor is still the most cost-effective choice in terms of volume-to-volume ratio and volume-to-price ratio, and is widely applied to consumer electronics, communication products, automation control, automobile industry, photoelectric products, high-speed railways, aviation and military equipment and the like.
According to the capacitance calculation formula C = epsilon S/d of the capacitor, wherein C is the capacitance, epsilon is the dielectric constant of the dielectric, S is the facing area of the positive electrode plate and the negative electrode plate of the capacitor, and d is the distance between the positive electrode plate and the negative electrode plate, it can be seen that the capacitance of the capacitor is in direct proportion to the dielectric constant of the dielectric, the area of the electrode plates is in direct proportion, and the distance between the electrodes is in inverse proportion.
In the actual structure of the liquid aluminum electrolytic capacitor, there are two capacitors, in which the positive electrode foil and the electrolyte form a capacitor C1, the electrolyte and the negative electrode foil form a capacitor C2, and the two capacitors are connected in series, and the total capacity C = (C1 × C2)/(C1 + C2), and in order to increase the total capacity, the capacities of the positive electrode foil and the negative electrode foil need to be increased. The first method of capacity increase is to increase the dielectric constant of the dielectric, using a valve metal with a high oxide dielectric constant, such as: tantalum, niobium, and the like, but these metals are rare metals, and are relatively small in the amount of resources on the earth, expensive, and lower in cost performance than aluminum; the second method is to reduce the distance between electrodes, and in the liquid aluminum electrolytic capacitor, the dielectric is Al oxide203The film layer, the distance between electrodes is the thickness of the oxide film, and the positive electrode foil film layer is in direct proportion to the capacitor withstand voltage, so that the thickness of the oxide film cannot be reduced at the same level as the withstand voltage. The oxide film of the negative foil is stable, and the extremely thin oxide layer formed on the surface of the negative foil is only slightly thicker than the natural oxide film and cannot be reduced any more; the third method is a conventional method for increasing the area of the electrode foil to increase the capacity and miniaturize the capacity. For a long time, the miniaturization of the liquid aluminum electrolytic capacitor depends on the surface-enlarging corrosion technology of the aluminum foil, namely, the surface of the aluminum foil is corroded into a spongy cavity by an electrochemical corrosion method, so that the area of the spongy cavity is enlarged. With the continuous progress of the technology, the face expansion times are increased year by year. However, the current technology has reached its physical limit basically, the increasing speed is very slow, taking the negative electrode foil as an example, the specific volume is 500uF/cm2The left and right are maximum degrees, but after the capacitor is connected with the positive foil capacitor in series, the whole capacitance capacity is still greatly influenced, and the liquid aluminum electrolytic capacitor is prevented from being further smallAnd (4) forming.
Research has been conducted for many years to increase the specific volume of the negative foil and reduce the loss of the capacity of the positive foil, and a more advanced scheme is to attach a material with a high dielectric constant to an aluminum substrate and increase epsilon to increase the capacity. Among them, Japanese capacitor corporation developed a method of plating titanium on an aluminum substrate by vapor deposition, the titanium surface was in the form of a pyramid having irregularities to increase the surface area to some extent, and then passivated to form TiO on the surface2Film due to TiO2Has a specific Al content203The specific volume of the negative electrode foil made by the method is greatly improved, but the specific volume can only reach 1000 uF/cm due to the nonideal surface area2To the extent that, in low voltage bulk capacitors, there is still some loss of positive foil capacitance.
However, in order to increase the capacitance of a capacitor, chinese patent 201080013193.4 relates to an electrode structure, a capacitor, a battery, and a method for manufacturing an electrode structure, the electrode structure having: aluminum material; a dielectric layer formed on a surface of the aluminum material; and an intermediate layer containing aluminum and carbon, which is formed between the aluminum material and the dielectric layer and in at least a partial region of the surface of the aluminum material, wherein the dielectric layer contains dielectric particles containing a valve metal, and an organic layer is formed on at least a partial surface of the dielectric particles. Meanwhile, the manufacturing method of the electrode structure body comprises the following steps: 1) a mixture layer forming step of forming a mixture layer containing dielectric particles of a valve metal and a binder on a surface of an aluminum material; 2) and a heating step of heating the aluminum material having the mixture layer formed thereon in a state of being placed in a space containing a hydrocarbon-containing substance.
Although the above electrode structure has a dielectric particle layer of valve metal attached to an aluminum foil to increase the specific volume of the electrode, the dielectric particles are densely bonded to the aluminum foil by aluminum carbide, and thus it is necessary to heat the electrode in a space containing hydrocarbon substances, which is not preferable in terms of safety and economy.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provide an improved high-specific-volume and ultrathin negative electrode foil.
The liquid aluminum electrolytic capacitor is mainly characterized in that cavities are formed by the shrinkage of a binder after high temperature, so that electrolyte can enter the surface of titanium dioxide particles in a coating through the cavities, therefore, the distance between the electrolyte and a negative foil electrode is only the diameter of the titanium dioxide particles, the distance between a positive plate electrode and a negative plate electrode is greatly reduced, the positive area and the negative area of the positive plate electrode and the negative plate electrode of the capacitor are increased by combining the increase of the dielectric constant, the capacitance is revolutionarily improved, the volume with the same capacity can be reduced by 20%, and the liquid aluminum electrolytic capacitor makes great contribution to the miniaturization of the capacitor.
In order to solve the technical problems, the invention adopts a technical scheme that:
a high specific volume and ultrathin negative electrode foil comprises an aluminum base material and a dielectric layer, wherein holes are formed on the surface of the aluminum base material by etching, the aperture of each hole is 50-500 nm, and the depth of each hole is 100-1000 nm; the dielectric layer is a coating rolled on the holes and the surface of the aluminum substrate, the thickness of the coating formed on the surface of the aluminum substrate after rolling is 50% -80% of the thickness of the coating formed on the surface of the aluminum substrate before rolling, the slurry of the coating is prepared from dielectric oxide particles of valve metal, organic resin, dispersant and solvent according to the mass ratio of 1: 0.1-1: 0.0001-0.01: 5-50, the materials are uniformly mixed, the slurry is coated on the surface of the aluminum substrate with the holes, the aluminum substrate is dried for 10-300 s in a high-temperature furnace at 100-300 ℃, and then the aluminum substrate is carbonized under the conditions of oxygen isolation and temperature control of 400-600 ℃ to form the coating before rolling.
Preferably, the pores are distributed over the surface of the aluminum substrate at a density of 1X 103～9×105Per cm2。
Preferably, the aperture of the hole is 100-300 nm; the hole depth of the hole is 400-700 nm; the holes are distributed on the surface of the aluminum substrate with a density of 1 × 104～5×104Per cm2. At this time, it is preferableAnd realizing the compact combination of the dielectric layer and the surface of the aluminum substrate.
Preferably, the thickness of the coating formed on the surface of the aluminum substrate after rolling is 0.5 to 5 μm.
According to a specific embodiment and preferred aspect of the present invention, the valve metal has an average particle size of 10 to 500nm and is one or more of magnesium, thorium, cadmium, tungsten, tin, tantalum, titanium, hafnium, zirconium and niobium. Generally, the average particle size of the oxide dielectric particles of the selected valve metal is 40 to 200 nm. In the case of non-spherical particles, the particle size is defined as the average of the major axis diameter and the minor axis diameter.
Meanwhile, the organic resin in the present application is: a carboxyl-modified polyolefin resin; a vinyl acetate resin; vinyl chloride resin; vinyl chloride-vinyl acetate copolymer resin; a vinyl alcohol resin; a fluorinated vinyl resin; acrylic resin; a polyester resin; a urethane resin; an epoxy resin; urea resin; a phenolic resin; an acrylonitrile resin; nitrocellulose resins; paraffin wax; synthetic resins such as polyethylene wax; and natural resins such as wax, tar, glue, lacquer, rosin, beeswax and the like, and the main functions of the coating are as follows: 1. enabling physical connection between the dielectric particles; 2. after the heat treatment, the dielectric particles are carbonized to form electrical continuity between the dielectric particles and the aluminum substrate.
The solvents in this application are: ketones, esters, alcohols, aromatics, aliphatics, water, etc., which mainly function as: 1. the viscosity of the slurry is adjusted, so that the coating is convenient; 2. and after drying, volatilizing to leave a gap, so that the electrolyte can conveniently enter the coating and contact with the dielectric particles.
The dispersing agent in this example is: fatty acids, fatty amides, metallic soaps and the like, which mainly play a role in: reduce the aggregation of particles in a dispersion system and facilitate the mixing and dispersion of slurry.
The other technical scheme of the invention is as follows: a liquid aluminum electrolytic capacitor comprises a core package, wherein the core package comprises the negative electrode foil.
Meanwhile, the production process of the negative electrode foil comprises the following steps:
s1, selecting an aluminum substrate, wherein the aluminum content is 99.0-99.9%;
s2, a step of forming a dielectric layer, comprising the steps of: a) preparing slurry; b) etching the surface of the aluminum substrate to form holes, coating the slurry on the surface of the aluminum substrate with the holes, drying the surface, feeding the aluminum substrate into a rolling mill, pressing the coating into the holes, and compacting the coating on the holes and the surface of the aluminum substrate; c) carbonizing, wherein the aperture of the hole is 50-500 nm, and the hole depth is 100-1000 nm; and the thickness of the coating formed on the surface of the aluminum substrate after rolling is 50-80% of the thickness of the coating formed on the surface of the aluminum substrate before rolling.
Preferably, the selected aluminum substrate is put into a hydrochloric acid solution with the concentration of 0.1-4 mol/L and the temperature of 20-100 ℃ for soaking for 5-60 s, then a nitric acid solution with the concentration of 2-4 wt% is adopted for washing, and then the aluminum substrate is washed by clean water and dried. The method mainly comprises the steps that an aluminum substrate is soaked in an acid solution, impurities in the aluminum substrate and aluminum form a micro-battery effect, holes are corroded in the surface of the aluminum substrate, and meanwhile, the size of the expected holes is achieved by controlling the reaction temperature, the acid concentration and the reaction time, so that the finally formed dielectric layer and the aluminum substrate are high in combination firmness and not prone to falling off.
Preferably, before the step c), drying for 10-300 s in a high temperature furnace at 100-300 ℃ to complete the drying of the coating surface. The purpose of the drying at this point is: part of the solvent in the mixture layer is volatilized, the corresponding volume is emptied, and surface drying is realized.
Preferably, in step c) of S2, the heat treatment temperature is 400 to 600 ℃, the heat treatment time is 1 to 48 hours, and the carbonization is performed under the condition of isolating oxygen.
The conditions for excluding oxygen mainly refer to an inert gas atmosphere, a vacuum atmosphere or a reducing atmosphere.
Due to the adoption of the technical scheme, compared with the prior art, the invention has the following advantages:
the negative electrode foil obtained by the etching and rolling process not only reduces the resistance of the coating and increases the capacity of the capacitor, but also has thin thickness, strong conductivity, strong adhesiveness and strong safety.
Drawings
Fig. 1 is a schematic structural view of a negative electrode foil according to the present invention before rolling;
fig. 2 is a schematic view of a rolled negative electrode foil according to the present invention;
FIG. 3 is a schematic view of the particle structure of FIG. 1 (before rolling);
FIG. 4 is a schematic view of the particle structure of FIG. 2 (after rolling);
wherein: 1. an aluminum substrate; 10. a hole; 2. a dielectric layer; 2a, a bonding layer; 2b, a covering layer.
Detailed Description
The preferred embodiments of the present invention will be described in conjunction with the accompanying drawings, and it will be understood that they are described herein for the purpose of illustration and explanation and not limitation.
Example 1
Referring to fig. 1 and 2, the present embodiment provides a high specific volume, ultra-thin negative electrode foil, which includes an aluminum substrate 1 and a dielectric layer 2 formed on the surface of the aluminum substrate 1.
Specifically, the production process of the negative electrode foil comprises the following steps:
s1, selecting an aluminum substrate, wherein the aluminum substrate is an aluminum foil with the aluminum content of 99.5% and the thickness of 30 mu m;
s2, a step of forming a dielectric layer, comprising the steps of: a) preparing slurry; b) etching the surface of the aluminum substrate to form holes, coating the slurry on the surface of the aluminum substrate with the holes, drying the surface, feeding the aluminum substrate into a rolling mill, pressing the coating into the holes, and compacting the coating on the holes and the surface of the aluminum substrate; c) and carbonizing.
In the step a), the oxide dielectric particles of the valve metal, the organic resin, the dispersant and the solvent are mixed according to the mass ratio of 1: 0.5: 0.001: 8, and are stirred and mixed uniformly to prepare slurry.
In this example, the oxide of the valve metal is titanium dioxide particles, and the average particle diameter of the titanium dioxide particles is 50 to 80 nm; the adopted organic resin is phenolic resin; the solvent used is acetone; the adopted dispersant is triolein.
Step b) it can be carried out in three steps: firstly, forming holes; secondly, coating to form a coating; and thirdly, rolling, and elaborating each step in detail below.
Soaking the selected aluminum substrate in 0.5mol/L hydrochloric acid solution at the temperature of 60 +/-2 ℃ for 10s, washing by using 3wt% nitric acid aqueous solution, washing by using clean water and drying. Through the aluminum base material soaking in the acid solution, impurities in the aluminum base material and aluminum form a micro-battery effect, holes are corroded on the surface of the aluminum base material, and meanwhile, the size of the expected holes is achieved by controlling the reaction temperature, the acid concentration and the reaction time, so that the finally formed dielectric layer and the aluminum base material are high in combination firmness and not prone to falling off
Specifically, the holes 10 are recessed from the surface of the aluminum substrate 1, the diameter of the holes 10 is 100-150 nm, the depth of the holes is 400-500 nm, and the distribution density of the holes on the surface of the aluminum substrate 1 is 3 × 103Per cm2。
Secondly, the prepared slurry is directly and uniformly coated on the surface of the aluminum substrate, and then dried in a tunnel furnace at 200 + -5 ℃ for 90 seconds to dry the surface of the coating, wherein the thickness of the coating formed upward from the surface of the aluminum substrate (excluding the wall surface of the hole) is 4.2 μm.
In (c), a part of the coating is pressed into the holes and fills the holes to form a bonding layer 2a by rolling, and the remaining part is pressed against the bonding layer 2a and the surface covering layer 2b of the aluminum substrate 1.
In this example, the thickness of the covering layer 2b after rolling was 2.7 μm, i.e., 64.3% of the thickness of the coating layer before rolling.
In the step c), the rolled foil is put into a reducing atmosphere for heat treatment, the temperature of the heat treatment is 580 +/-5 ℃, the time of the heat treatment is 12 +/-1 h, so that the organic resin in the coating is carbonized to form a conductive framework, and the titanium dioxide nano-particles are attached to the surface of the aluminum substrate and are electrically conducted with the aluminum substrate 1 to form the dielectric layer 2.
Meanwhile, the formation process of the joining layer and the clad layer before and after rolling can be clearly expressed by the description of fig. 3 and 4.
The specific volume of the aluminum substrate after etching is 25uF/cm through testing2(ii) a The specific volume of the negative electrode foil formed with the dielectric layer was 5207uF/cm2(10 times of the specific volume in the prior art, so the anode foil can be called a high specific volume and ultrathin anode foil); intercepting a negative foil sample with the length multiplied by the width of 15cm multiplied by 1cm, and carrying out resistance detection along the length direction, wherein the resistance of the negative foil sample is 13.5m omega; the adhesion obtained by tape peeling was 93%, and the calculation method for the adhesion test was: adhesion (%) = (weight of sample after peeling-weight of aluminum foil itself used as a base material ÷ (weight of sample before peeling-weight of aluminum foil itself used as a base material) × 100%, which is a means commonly used in the art and will not be described in detail here, and specific volume after adhesion test is 4822 uF/cm2。
Example 2
The structure and the process of the high specific volume and ultrathin negative electrode foil related to the implementation are basically the same as those of the embodiment 1, and the difference is that:
1) the forming process of the holes in this example is: soaking the selected aluminum substrate in a hydrochloric acid solution with the concentration of 0.5mol/L and the temperature of 80 ℃ for 15s, then washing the aluminum substrate by using a 3wt% nitric acid aqueous solution, then washing the aluminum substrate by using clear water and drying the aluminum substrate.
Specifically, the aperture of the holes 10 is 150 to 250nm, the depth of the holes is 450 to 550nm, and the distribution density of the holes on the surface of the aluminum substrate 1 is 1 × 104Per cm2。
2) In the embodiment, the titanium dioxide particles, the organic resin, the dispersant and the solvent are mixed according to the mass ratio of 1: 0.6: 0.002: 10, and are stirred and mixed uniformly to prepare the slurry.
3) In this example, the slurry coating applied to the surface of the aluminum substrate was dried in a tunnel oven at 280. + -. 5 ℃ for 50 seconds to effect surface drying of the coating and then rolled, and the thickness of the covering layer 2b after rolling was 2.5 μm, that is, 59.5% of the thickness of the coating before rolling.
4) And in the step c), the rolled foil is put into an inert gas atmosphere for heat treatment, the temperature of the heat treatment is 500 +/-5 ℃, the time of the heat treatment is 20 +/-1 h, so that the organic resin in the coating is carbonized to form a conductive framework, and the nano-scale particles of the titanium dioxide are attached to the surface of the aluminum substrate and are electrically conducted with the aluminum substrate to form the dielectric layer 2.
The specific volume of the aluminum substrate after etching is 53uF/cm after testing2(ii) a The specific volume of the negative electrode foil formed with the dielectric layer was 5012uF/cm2(ii) a Intercepting a negative foil sample with the length multiplied by the width of 15cm multiplied by 1cm, and carrying out resistance detection along the length direction, wherein the resistance of the negative foil sample is 14.2m omega; adhesion obtained by tape stripping was 98%; the specific volume after the adhesion test was 4903uF/cm2。
Example 3
The structure and the process of the high specific volume and ultrathin negative electrode foil related to the implementation are basically the same as those of the embodiment 1, and the difference is that:
1) the forming process of the holes in this example is: soaking the selected aluminum substrate in a hydrochloric acid solution with the concentration of 1mol/L and the temperature of 80 ℃ for 20s, then washing by using a 3wt% nitric acid aqueous solution, then washing by using clear water and drying.
Specifically, the aperture of the holes 10 is 250-300 nm, the depth of the holes is 600-700 nm, and the distribution density of the holes on the surface of the aluminum substrate 1 is 4 × 105Per cm2。
2) In this example, titanium dioxide particles, organic resin, dispersant and solvent were mixed in a mass ratio of 1: 0.5: 0.002: 8, and stirred to be mixed uniformly to prepare a slurry.
3) In this example, the slurry coating applied to the surface of the aluminum substrate was dried in a tunnel oven at 110. + -. 5 ℃ for 240 seconds to effect surface drying of the coating and then rolled, and the thickness of the covering layer 2b after rolling was 2.4. mu.m, that is, 57.2% of the thickness of the coating before rolling.
4) And in the step c), the rolled foil is put into a vacuum atmosphere for heat treatment, the temperature of the heat treatment is 450 +/-5 ℃, the time of the heat treatment is 30 +/-1 h, so that the organic resin in the coating is carbonized to form a conductive framework, and the titanium dioxide nano-particles are attached to the surface of the aluminum substrate and are electrically conducted with the aluminum substrate to form the dielectric layer 2.
After testing, the specific volume of the aluminum substrate after etching is 97uF/cm2(ii) a The specific volume of the negative electrode foil with the dielectric layer formed thereon was 4378uF/cm2(ii) a Intercepting a negative foil sample with the length multiplied by the width of 15cm multiplied by 1cm, and carrying out resistance detection along the length direction, wherein the resistance of the negative foil sample is 15.1m omega; adhesion obtained by tape stripping was 99%; the specific volume after the adhesion test was 4350 uF/cm2。
Comparative example 1
The negative foil structure and process involved in this comparative example are essentially the same as example 1, except that:
in this comparative example, the coated foil was directly fed into a heating furnace without a rolling process to be carbonized.
The specific volume of the aluminum substrate after etching is 53uF/cm after testing2(ii) a The specific volume of the negative electrode foil formed with the dielectric layer was 5811uF/cm2(ii) a Intercepting a negative foil sample with the length multiplied by the width of 15cm multiplied by 1cm, and carrying out resistance detection along the length direction, wherein the resistance of the negative foil sample is 14.2m omega; adhesion obtained by tape stripping was 46%; specific volume after adhesion test was 2549 uF/cm2。
Comparative example 2
The negative foil structure and process involved in this comparative example are essentially the same as example 1, except that:
1) the formation process of the holes in this comparative example was: soaking the selected aluminum substrate in a hydrochloric acid solution with the concentration of 1.5mol/L and the temperature of 90 ℃ for 25s, then washing by using a 3wt% nitric acid aqueous solution, then washing by using clear water and drying.
Specifically, the diameter of the holes 10 is 600 to 700nm, the depth of the holes is 1100 to 1200nm, and the distribution density of the holes on the surface of the aluminum substrate 1 is 2 × 106Per cm2。
2) In this comparative example, the thickness of the covering layer 2b after rolling was 1.9 μm, that is, 45.2% of the thickness of the coating layer before rolling.
After testing, the specific volume of the aluminum substrate after etching is 204uF/cm2(ii) a The specific volume of the negative electrode foil with the dielectric layer formed thereon was 3148uF/cm2(ii) a Cutting a negative foil sample with length multiplied by width of 15cm multiplied by 1cm along the length directionDetecting the resistance, wherein the resistance is 17.8m omega; adhesion obtained by tape stripping was 99%; the specific volume after the adhesion test was 3127uF/cm2。
Comparative example 3
The negative foil structure and process involved in this comparative example are essentially the same as example 1, except that:
1) in this comparative example, the surface of the aluminum substrate was etched (i.e., the surface was flat and had no holes).
2) The thickness of the cover layer after rolling was 3.5 μm, i.e. 83.3% of the thickness of the coating layer before rolling.
The specific volume of the aluminum substrate which is not subjected to the etching treatment is tested to be 63uF/cm2(ii) a The specific volume of the negative electrode foil formed with the dielectric layer was 5538uF/cm2(ii) a Intercepting a negative foil sample with the length multiplied by the width of 15cm multiplied by 1cm, and carrying out resistance detection along the length direction, wherein the resistance of the negative foil sample is 13.1m omega; adhesion obtained by tape stripping was 11%; the specific volume after the adhesion test was 735 uF/cm2。
As can be seen from the comparative analysis, the main factors affecting the specific volume and adhesion of the negative electrode foil are shown in two aspects: firstly, etching to form a hole; and II, rolling. Meanwhile, there is a close relationship between the two, such as:
the dielectric layer formed by shallow etching or no etching, rolling and carbonization can fall off and have insufficient adhesion in a tape stripping test; the holes formed by etching are too large or too deep, and a large amount of dielectric layers are sunk into the aluminum substrate after rolling, so that although the adhesion meets the requirement, the titanium dioxide particles embedded in the aluminum substrate are tightly combined with the aluminum foil, no gap exists, and the electrolyte cannot permeate into the titanium dioxide particles, so that the titanium dioxide particles embedded in the aluminum foil cannot play the role of a dielectric medium, and the specific volume is reduced more.
In addition, in the liquid aluminum electrolytic capacitor produced by using the negative electrode foil according to embodiments 1 to 3, the value of epsilon is greatly increased by selecting titanium dioxide particles having an extremely high dielectric constant as the valve metal particles; the surface area S of the coating is greatly improved by stacking the nano-scale particles and shrinking the binder, and the binder shrinks after high temperature to form holes, so that electrolyte can enter the surface of the titanium dioxide particles in the coating through the holes, and the distance d between the electrolyte and the negative foil electrode is only the diameter of the titanium dioxide particles. Thus, the specific volume of the capacitor is improved revolutionarily by increasing epsilon and S and decreasing d, so that the capacitor volume of the capacitor can be reduced by 20% in the capacitor with the same capacity, and great contribution is made to the miniaturization of the capacitor.
Finally, it should be noted that: although the present invention has been described in detail with reference to the embodiments, it will be apparent to those skilled in the art that modifications may be made to the embodiments or portions thereof without departing from the spirit and scope of the invention.

Claims (10)

1. A high specific volume, ultra-thin type negative electrode foil, which comprises an aluminum substrate and a dielectric layer, is characterized in that: etching the surface of the aluminum substrate to form holes, wherein the hole diameter is 50-500 nm, and the hole depth is 100-1000 nm; the dielectric layer is a coating rolled on the surfaces of the holes and the aluminum substrate, the thickness of the coating formed on the surface of the aluminum substrate after rolling is 50% -80% of the thickness of the coating formed on the surface of the aluminum substrate before rolling, wherein the slurry of the coating is prepared from valve metal oxide dielectric particles, organic resin, dispersant and solvent according to the mass ratio of 1: 0.1-1: 0.0001-0.01: 5-50, the materials are mixed, stirred and mixed uniformly, the slurry is coated on the surface of the aluminum substrate with the holes, dried for 10-300 s in a high-temperature furnace at 100-300 ℃, and then carbonized under the conditions of oxygen isolation and temperature control at 400-600 ℃ to form the coating before rolling.
2. The high specific volume, ultra-thin type negative electrode foil according to claim 1, wherein: the holes are arranged on the surface of the aluminum substrateThe density of the distribution on the surface is 1X 103～9×105Per cm2。
3. The high specific volume, ultra-thin type negative electrode foil according to claim 1 or 2, wherein: the aperture of the hole is 100-300 nm; the hole depth of the hole is 400-700 nm.
4. The high specific volume, ultra-thin type negative electrode foil according to claim 1, wherein: the thickness of the coating formed on the surface of the aluminum substrate after rolling is 0.5 to 5 μm.
5. The high specific volume, ultra-thin type negative electrode foil according to claim 1, wherein: the grease is as follows: a carboxyl-modified polyolefin resin; a vinyl acetate resin; vinyl chloride resin; vinyl chloride-vinyl acetate copolymer resin; a vinyl alcohol resin; a fluorinated vinyl resin; acrylic resin; a polyester resin; a urethane resin; an epoxy resin; urea resin; a phenolic resin; an acrylonitrile resin; nitrocellulose resins; paraffin wax; synthetic resins such as polyethylene wax; and natural resins such as wax, tar, glue, lacquer or rosin.
6. The high specific volume, ultra-thin type negative electrode foil according to claim 1, wherein: the solvent is as follows: ketones, esters, alcohols, aromatics, aliphatics or water.
7. The high specific volume, ultra-thin type negative electrode foil according to claim 1, wherein: the dispersant is as follows: fatty acids, fatty amides or metallic soaps.
8. The high specific volume, ultra-thin type negative electrode foil according to claim 1, wherein: the average grain diameter of the valve metal is 10-500 nm, and the valve metal is one or more of magnesium, thorium, cadmium, tungsten, tin, tantalum, titanium, hafnium, zirconium and niobium.
9. The high specific volume, ultra-thin type negative electrode foil according to claim 1, wherein: the coating carbonization is completed in inert gas atmosphere, vacuum atmosphere or reducing atmosphere.
10. A liquid aluminum electrolytic capacitor comprises a core package, and is characterized in that: the core package comprises a high specific volume, ultra-thin body negative foil according to any one of claims 1 to 9.
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