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CN-122000205-A - Sintered anode foil resistant to large ripple current, preparation method of sintered anode foil and electrolytic capacitor

CN122000205ACN 122000205 ACN122000205 ACN 122000205ACN-122000205-A

Abstract

The invention relates to the technical field of anode foil processing, in particular to a sintered anode foil resistant to large ripple current, a preparation method thereof and an electrolytic capacitor; the method comprises the steps of mixing aluminum powder with a dry powder binder in a dry mode to form composite powder, preheating a clean aluminum base band with a roughened surface, depositing the composite powder on the surface of the aluminum base band under the action of a pulse electrostatic field to form a gradient pore structure coating, carrying out in-situ heating pre-curing on the aluminum base band with the gradient pore structure coating, and then sintering to form a metallurgical bonding of a gradient pore structure to obtain a sintered anode foil resistant to large ripple current.

Inventors

  • ZHANG CHENGZHI
  • JIN JUN
  • ZHANG HONGBING
  • QIAN PENG
  • ZHU JUN
  • WU YONGQING

Assignees

  • 南通江海电容器股份有限公司

Dates

Publication Date
20260508
Application Date
20260409

Claims (10)

  1. 1. The preparation method of the sintered anode foil resistant to the large ripple current is characterized by comprising the following steps of: S1, carrying out dry mixing on aluminum powder and a dry powder binder to form composite powder; s2, preheating a clean aluminum-based belt with roughened surface, and performing multistage pulse electrostatic deposition on the composite powder under the action of a pulse electrostatic field to form a gradient pore structure coating on the surface of the aluminum-based belt; S3, performing in-situ heating pre-solidification on the aluminum base band with the gradient pore structure coating, and then sintering to form metallurgical bonding of the gradient pore structure, so as to obtain the sintered anode foil resistant to large ripple current.
  2. 2. The preparation method of the high ripple current resistant sintered anode foil according to claim 1 is characterized by comprising the steps of selecting aluminum powder with unimodal average particle size distribution and a dry powder binder to form composite powder, or selecting aluminum powder with multimodal average particle size distribution and a dry powder binder to form multi-stage composite powder with gradually increased particle size gradient respectively, carrying out multi-stage pulse electrostatic spraying on the aluminum-based belt to deposit the composite powder or the multi-stage composite powder, and regulating and controlling the parameters to carry out multi-stage deposition to form a gradient pore structure coating with gradually increased porosity from the surface of the base belt, wherein the pulse electrostatic field negative voltage is gradually increased from 10 kV to 100kV, the pulse frequency is gradually decreased within the range of 1500Hz-50Hz, and the duty ratio is gradually increased within the range of 5% -95%; The purity of the aluminum powder is at least 4N, and the median particle diameter of the aluminum powder is in the range of 0.5-8 microns, wherein the dry powder binder is selected from polyvinylidene fluoride powder and/or thermoplastic acrylic resin powder, and the average particle diameter of the dry powder binder is less than 1 micron; The mass ratio of the dry powder binder in the composite powder is 0.5% -5%; The gradient pore structure coating has a total thickness of 30 microns to 80 microns.
  3. 3. The preparation method of the high ripple current resistant sintered anode foil according to claim 2 is characterized in that aluminum powder with multiple median particle size distributions from small particle size to large particle size is selected to form multi-stage composite powder with gradually increased particle size gradients with a dry powder binder, then the aluminum base band sequentially passes through at least two pulse electrostatic spraying chambers to carry out multi-stage pulse electrostatic spraying deposition under the action of a pulse electrostatic field, the pulse electrostatic spraying chambers can spray the multi-stage composite powder onto the surface of the aluminum base band, the number of the pulse electrostatic spraying chambers is correspondingly set according to the particle size gradient number of the multi-stage composite powder, and the spraying parameters of the pulse electrostatic spraying chambers are regulated so that the multi-stage composite powder sequentially covers the surface of the aluminum base band according to the rule of gradually increased particle size gradient number gradients, thereby forming gradient pore structure coatings with gradually increased pore sizes from a base band to the outside on the surface of the aluminum base band.
  4. 4. The method for preparing the sintered anode foil resistant to large ripple current according to claim 3, wherein the multi-stage composite powder comprises a primary composite powder and a secondary composite powder; the primary composite powder consists of aluminum powder with the average particle size of 1-3 mu m and a dry powder binder; The secondary composite powder consists of aluminum powder with the average particle size ranging from 3 mu m to 8 mu m and a dry powder binder.
  5. 5. The method for preparing the sintered anode foil resistant to the large ripple current according to claim 4, wherein first-stage pulse electrostatic spraying of the first-stage composite powder to the surface of the aluminum base belt is performed in a first pulse electrostatic spraying chamber to form a bottom layer, and second-stage pulse electrostatic spraying of the second-stage composite powder to the surface of the bottom layer is performed in a second pulse electrostatic spraying chamber to form a surface layer; The primary pulse electrostatic spraying parameters are that the pulse electrostatic field is regulated and controlled to be between 10 kV and 50kV, the pulse frequency is 600-1000 Hz, and the duty ratio is 20-40%; The secondary pulse electrostatic spraying parameters are that the pulse electrostatic field is regulated and controlled within the range of negative voltage 50kV to negative voltage 100kV, the pulse frequency is 100Hz-500Hz, and the duty ratio is 50% -80%.
  6. 6. The method for preparing a sintered anode foil resistant to large ripple currents as claimed in claim 3, wherein said multi-stage composite powder comprises a first composite powder, a second composite powder and a third composite powder; the first composite powder consists of aluminum powder with the average particle size ranging from 0.5 mu m to 2 mu m and a dry powder binder; The second composite powder consists of aluminum powder with the average particle size of 2-4 mu m and a dry powder binder; The third composite powder consists of aluminum powder with the average particle size of 4-8 mu m and a dry powder binder.
  7. 7. The method for preparing the sintered anode foil resistant to the large ripple current according to claim 6, wherein a first pulse electrostatic spraying is performed in a first pulse electrostatic spraying chamber to form a bottom layer on the surface of an aluminum base band, a second pulse electrostatic spraying is performed in a second pulse electrostatic spraying chamber to form an intermediate layer on the surface of the bottom layer, and a third pulse electrostatic spraying is performed in a third pulse electrostatic spraying chamber to form a surface layer on the surface of the intermediate layer; the first pulse electrostatic spraying parameters are that the pulse electrostatic field is regulated and controlled to be between negative voltage 10 kV and negative voltage 50kV, the pulse frequency is 600Hz-1000Hz, and the duty ratio is 20% -35%; The second pulse electrostatic spraying parameters are that the pulse electrostatic field is regulated and controlled within the range of negative voltage 50kV to negative voltage 65kV, the pulse frequency is within the range of 400Hz-600Hz, and the duty ratio is within the range of 35% -50%; The third pulse electrostatic spraying parameter is that the pulse electrostatic field is regulated and controlled to be between 65kV and 100kV in negative voltage, the pulse frequency is 100-400 Hz, and the duty ratio is 50-80%.
  8. 8. The method for preparing a sintered anode foil resistant to large ripple current according to any one of claims 1 to 7, wherein the aluminum base tape is preheated after being subjected to alkali degreasing treatment, water washing, drying and surface roughening treatment in sequence; The surface roughening treatment is to make the surface roughness of the aluminum base band at least reach Ra more than or equal to 0.8 mu m; The preheating temperature of the aluminum base band is 50-80 ℃; the temperature of the in-situ heating pre-curing is 20-50 ℃ higher than the softening point temperature of the dry powder adhesive, and the pre-curing heat preservation time is 3-10 seconds; The sintering adopts vacuum sintering treatment, and parameters are set as follows, and the sintering is carried out for 1 hour to 3 hours under the conditions that the vacuum degree is at least 10 -3 Pa and the temperature is 550 ℃ to 630 ℃.
  9. 9. The sintered anode foil resistant to large ripple current is characterized in that the sintered anode foil is prepared by the preparation method of any one of claims 1-8, and structurally comprises an aluminum base band and a gradient pore structure coating deposited and sintered on the surface of the aluminum base band, wherein the microstructure of the gradient pore structure coating is a pore structure with sequentially increasing porosity from the base band to the outside.
  10. 10. Electrolytic capacitor, characterized in that it comprises a sintered anode foil resistant to large ripple currents, produced by the production method according to any one of claims 1-8.

Description

Sintered anode foil resistant to large ripple current, preparation method of sintered anode foil and electrolytic capacitor Technical Field The invention relates to the technical field of anode foil processing, in particular to a sintered anode foil resistant to large ripple current, a preparation method thereof and an electrolytic capacitor. Background The performance of the anode foil of the core component of the aluminum electrolytic capacitor directly determines the specific capacitance, equivalent Series Resistance (ESR), ripple current resistance and service life of the capacitor. As electronic devices continue to develop toward high power density and miniaturization, the requirements for the capability of aluminum electrolytic capacitors to withstand large ripple currents are becoming increasingly stringent. If joule heat generated in the capacitor by ripple current cannot be effectively dissipated, volatilization of electrolyte and degradation of oxide film are accelerated, service life of the device is greatly shortened, and even thermal runaway and safety accidents are caused. The anode foil of the traditional aluminum electrolytic capacitor is mainly prepared by an electrochemical corrosion process (corrosion foil), and a corrosion tunnel is formed on the surface of the aluminum foil by using strong acid and strong alkali to increase the specific surface area, but the problems of high treatment cost of corrosion waste liquid and serious environmental pollution are solved, the corrosion aperture and the corrosion aperture are deeply limited by the thickness of an aluminum foil substrate, the specific capacitance is increased to tend to be a bottleneck, the mechanical strength of the aluminum foil is greatly reduced by deep corrosion, and the subsequent processing fracture risk is increased. In order to overcome the defect of corrosion foil, aluminum powder sintering type anode foil technology is increasingly paid attention to. The current mainstream sintered foil is mostly coated by wet coating process, namely aluminum powder, organic binder and a large amount of organic solvent (such as NMP, benzene solvent, etc.) are mixed for pulping and then coated on an aluminum base band. The wet process has the defects of serious volatilization and pollution of an organic solvent, high waste gas treatment cost, influence on the reliability of a device due to solvent residues, internal stress generated by drying and shrinkage of slurry, microcrack, layering or uneven pores of a coating, weakening of the wetting efficiency of electrolyte, insufficient decomposition of an organic binder in a high-temperature sintering stage, increased leakage current due to carbon residues left, complicated slurry preparation, drying and solvent recovery system and high production cost. In the prior art, in the field of lithium ion batteries and supercapacitors, dry rolling has been used for the preparation of electrode sheets. However, the above prior art is directed to an electrochemical energy storage electrode using lithium intercalation/deintercalation or double electric layer charge and discharge as a working mechanism, and its core performance index is energy density and rate capability, so that the requirements on thermal management of the electrode are relatively loose, and the working frequency is generally not more than hundreds of hertz. However, the working mechanism of the aluminum electrolytic capacitor is basically different from that of the energy storage device. The anode foil of the aluminum electrolytic capacitor takes an aluminum oxide film as a medium, and works under the conditions of high frequency (hundreds of kHz) and high ripple current, and the internal thermal power density of the capacitor is extremely high. Under the condition of large ripple current, the anode foil porous layer needs to meet two critical requirements of mutual restriction, namely (1) electrolyte needs to quickly and deeply permeate the porous layer to ensure smooth ion transmission channels and reduce ion transmission impedance, and (2) the porous layer needs to have high-efficiency axial (namely outward from an aluminum-based belt) heat conduction capability so as to rapidly conduct out joule heat generated by the ripple current and avoid local overheating. This dual requirement puts far more demanding performance constraints on the pore structure, pore size distribution and pore channel connectivity of the porous layer than lithium battery or supercapacitor electrodes, and the prior art cannot directly meet the above special requirements. In view of the above background, there is a need to develop a solvent-free, low-pollution anode foil preparation process suitable for high-frequency and large-ripple conditions of aluminum electrolytic capacitors. Disclosure of Invention Aiming at the technical problems that in the existing wet aluminum powder sintered foil process, organic solvent pollution is serious, cracks and pore struct