CN114540932A - Process method for improving uniformity of electrode foil pores - Google Patents
Process method for improving uniformity of electrode foil pores Download PDFInfo
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- C25F3/00—Electrolytic etching or polishing
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Abstract
The invention relates to a process method for improving the pore forming uniformity of an electrode foil, which comprises the following steps: the method comprises the following steps of pretreatment, first cleaning, aluminum foil surface pretreatment, first corrosion reaming, second cleaning, second corrosion reaming, third cleaning, acid cleaning, fourth cleaning and drying treatment. Wherein, in the step of pretreating the surface of the aluminum foil, preset pits or laser temperature rising points are formed on the front side and the back side of the aluminum foil. Actual experiments prove that a series of initial corrosion points with good distribution density uniformity and consistent appearance can be formed on the surface of the aluminum foil by the aid of the preset pits or laser temperature raising points, the occurrence of hole combination is effectively eliminated, and good bedding is made for effectively improving the uniformity of subsequent electrolytic corrosion of the aluminum foil.
Description
Technical Field
The invention relates to the technical field of electrode foil manufacturing, in particular to a process method for improving the pore forming uniformity of an electrode foil.
Background
Along with the miniaturization trend of aluminum electrolytic capacitors, higher capacity requirements are provided for medium and high voltage anode foils, the randomness of corrosion initial points is caused due to the nonuniformity of impurity ions, surface oxide film states and surface defects of corrosion foils prepared by the traditional manufacturing process, and further the distribution density of first-level corrosion holes is uneven, after secondary reaming corrosion, the nonuniform situation of the corrosion holes is more obvious, and the first factor restricting the capacity improvement is achieved.
Chinese invention patent CN105336499A discloses a pretreatment method for anode aluminum foil corrosion of an electrolytic capacitor, which comprises the following steps: pretreatment, primary corrosion, intermediate cleaning, secondary corrosion and aftertreatment. The pretreatment is carried out before the aluminum foil is subjected to electrolytic corrosion, and mainly has the functions of removing oil stains, impurities, oxidation films and the like on the surface of the aluminum foil, readjusting the tissue structure of the aluminum foil, and improving the surface state of the aluminum foil to ensure that the surface of the aluminum foil is uniform. The pretreatment process is that the aluminum foil is soaked in acid liquor for a period of time at a certain temperature to remove oil stains and oxidation films on the surface of the aluminum foil. And then forming an initial eroded cave on the surface of the aluminum foil through primary corrosion, and carrying out corrosion reaming on the initial eroded cave in the secondary corrosion step.
However, metal impurities inevitably remain on the surface of the aluminum foil, and due to the high concentration of the acid solution, in the process of removing oil stains and the oxide film on the surface, impurity elements such as iron and copper remaining on the surface layer of the aluminum foil are also dissolved, so that the distribution density of the primary corrosion holes is uneven, and after secondary reaming corrosion, the uneven situation of the corrosion holes is more obvious, and foil surface color difference is formed, which directly affects the consistency of the aluminum foil. In addition, processing defects (surface pits or bumps with an out-of-size) remain on the surface of the aluminum foil, and the surface pits or bumps become corrosion-prone areas due to the influence of potential energy difference, so that the problem of non-uniformity of the distribution density of the primary corrosion holes is further worsened. The concrete points are as follows: after the aluminum foil is subjected to the holing treatment (fine pores are formed on the front and back surfaces of the aluminum foil in an acid corrosion mode), the distribution uniformity of formed holes is extremely poor, and the pore sizes and the depths are different. In the subsequent reaming corrosion, the area with high hole density may generate and cause the capacity attenuation, and the part with low hole density is not fully utilized, thereby causing the capacity extraction rate of the electrode foil to be low. Thus, a skilled person is urgently needed to solve the above problems.
Disclosure of Invention
Therefore, in view of the above-mentioned problems and drawbacks, the present inventors have collected relevant information, evaluated and considered in many ways, and continuously conducted experiments and modifications by technicians with many years of research and development experience in this field, which finally resulted in the appearance of the process for improving the uniformity of the electrode foil pores.
In order to solve the technical problem, the invention relates to a process method for improving the pore-forming uniformity of an electrode foil, which comprises the following steps:
s1, pretreatment; placing the aluminum foil in the first acid solution, wherein the temperature value is T1, and the holding time is T1; the first acid liquid is weakly acidic, and the pH value is not less than 6;
s2, cleaning for the first time to remove the first acid liquor remained on the surface of the aluminum foil;
s3, pretreating the surface of the aluminum foil; uniformly distributed preset pits or laser heating points are formed on the front side and the back side of the aluminum foil;
s4, primary corrosion reaming; placing the aluminum foil in a second acid solution with a temperature value of T2, and introducing current into the second acid solution for a holding time of T2;
s5, cleaning for the second time to remove the second acid liquor remained on the surface of the aluminum foil;
s6, secondary corrosion reaming; placing the aluminum foil in a third acid solution with a temperature value of T3, and introducing current into the third acid solution for a holding time of T3;
s7, cleaning for the third time to remove the third acid liquor remained on the surface of the aluminum foil;
s8, acid washing, namely placing the aluminum foil in fourth acid liquor with a temperature value of T4, and keeping the temperature for T4 to corrode metal impurities remained on the surface of the aluminum foil;
s9, cleaning for the fourth time to remove the fourth acid liquid and the impurity corrosive substance remained on the surface of the aluminum foil;
and S10, drying to dry the aluminum foil.
As a further improvement of the technical scheme of the invention, the transverse section of the preset pit is circular. Assuming that the depth value of the preset pit is d, the diameter size value is r and the mutual spacing value is w, d is more than or equal to 20 nm and less than or equal to 30nm, r is more than or equal to 30nm and less than or equal to 50nm, and w is more than or equal to 200nm and less than or equal to 600 nm.
As a further improvement of the technical scheme of the invention, the preset pits are formed on the aluminum foil by a press roll. A plurality of profiling bulges matched with the preset concave pit in shape are uniformly distributed on the circumferential side wall of the compression roller. The number of the press rolls is set to 2, and the two sides of the aluminum foil are symmetrically arranged to form a passing gap through which the aluminum foil freely passes. During its passage through the gap, the aluminium foil is constantly subjected to a rigid pressure from the pressure roller.
As a further improvement of the technical scheme of the invention, the laser temperature rise point is formed on the aluminum foil by a laser. The number of lasers was set to 2, the two sides of the aluminum foil were symmetrically arranged, and the temperature of the generated focal point was below 600 ℃. The transverse section of the laser temperature rise point is circular. Assuming that the depth value of the laser temperature rise point is d2, the diameter size value is r2, and the mutual spacing value is w2, then 20 nm-20 nm d 2-30 nm, 30 nm-30 nm r 2-50 nm, and 200 nm-200 nm w 2-600 nm.
As a further improvement of the technical scheme of the invention, in step S1, the first acid solution is 0.1mol/L HCL solution, T1 is more than or equal to 68 ℃ and less than or equal to 71 ℃, and T1 is more than or equal to 0.8S and less than or equal to 1.5S.
As a further improvement of the technical solution of the present invention, T1=70 ℃ and T1=1 s.
As a further improvement of the technical scheme of the invention, in step S4, the second acid solution is 0.5mol/L HCL and 1.2mol/L H2SO4The temperature T2 is more than or equal to 68 ℃ and less than or equal to 71 ℃, and the temperature T2 is more than or equal to 60S and less than or equal to 65S. Current isGradient attenuation, and maximum current value of 2A/cm2The minimum current value is 1.5A/cm2。
As a further improvement of the technical scheme of the invention, T2=70 ℃ and T2=60 s.
As a further improvement of the technical scheme of the invention, in step S6, the third acid solution is HNO of 0.3mol/L3The solution has T3 not less than 70 ℃ and not more than 75 ℃ and T3 not less than 90S and not more than 110S. The current is constant and is stabilized at 0.6A/cm2。
As a further improvement of the technical scheme of the invention, T3=72 ℃ and T3=100 s.
As a further improvement of the technical scheme of the invention, in step S8, the fourth acid solution is 0.03ml/L nitric acid solution, T4 is more than or equal to 58 ℃ and less than or equal to 60 ℃, and T4 is more than or equal to 60S and less than or equal to 70S.
As a further improvement of the technical scheme of the invention, T4=60 ℃ and T4=60 s.
As a further improvement of the present invention, in step S10, the aluminum foil obtained in step S9 is placed in an oven, and the heating temperature is controlled to 220 ℃. The heating cavity of the oven is always filled with inert gas.
Compared with the traditional preparation method of the electrode foil for the medium-high voltage aluminum electrolytic capacitor, the technical scheme disclosed by the invention omits the conventional step of corrosion and hole formation, and replaces the conventional step by the preset pits or laser heating points generated on the surface of the aluminum foil. The preset pits and the laser temperature-raising points are physical defects formed on the aluminum foil and can be used as starting points of subsequent corrosion to finally form uniformly-distributed corrosion holes.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
FIG. 1 is a metallographic picture of an electrode foil for a medium-high voltage aluminum electrolytic capacitor produced by a conventional method.
FIG. 2 is a metallographic picture of an electrode foil for a medium-high voltage aluminum electrolytic capacitor produced by the method in example 1.
Detailed Description
For the purpose of enhancing understanding of the present invention, the present invention will be further described in detail with reference to the following examples, which are provided for illustration only and are not to be construed as limiting the scope of the present invention. The methods are conventional methods, not specifically described.
Example 1
The process method for improving the pore forming uniformity of the electrode foil comprises the following steps:
s1, pretreatment; placing the aluminum foil in a weakly acidic solution (0.1 mol/L HCL solution), wherein the pH value is not less than 6, the temperature value is controlled at 68 ℃, and the holding time is 0.8S; only the oil stain remained on the surface of the aluminum foil is neutralized and removed, and the aluminum foil body is not corroded;
s2, cleaning for the first time, namely washing the aluminum foil by using clean water to remove the HCL solution remained on the surface of the aluminum foil;
s3, pretreating the surface of the aluminum foil; preset pits are formed on the front and back surfaces of the aluminum foil; only for the front surface of the aluminum foil, the number of the preset pits is set to be a plurality and the preset pits are uniformly distributed.
A method for forming the preset pits is proposed, and specifically comprises the following steps: and forming the preset pits on the aluminum foil by a pressing roller. A plurality of profiling bulges matched with the preset concave pit in shape are uniformly distributed on the circumferential side wall of the compression roller. The number of the pressing rollers is set to 2, and both sides of the aluminum foil are symmetrically arranged to form a passing gap through which the aluminum foil freely passes. During its passage through the gap, the aluminium foil is constantly subjected to a rigid pressure from the pressure roller.
S4, performing primary corrosion reaming to increase the radial size of the preset pit; placing the aluminum foil in 0.5mol/L HCL and 1.2mol/L H at a temperature of 68 DEG C2SO4And passing a current through the mixed solution for a retention time of 60 s. The introduced current is in gradient attenuation, and the maximum current value is 2A/cm2The minimum current value is 1.5A/cm2。
S5, cleaning for the second time, and cleaning the surface of the aluminum foil with clean water again to remove the second acid liquid remained on the surface of the aluminum foil;
s6, carrying out secondary corrosion reaming to increase the radial size of the preset pits again; placing the aluminum foil in HNO with the temperature value of 70 ℃ of 0.3mol/L3Introducing current into the solution, and keeping the current for 90 s;
s7, cleaning for the third time, and removing the third acid liquor remained on the surface of the aluminum foil by using clean water again;
s8, acid washing, namely placing the aluminum foil in a nitric acid solution with the temperature value of 58 ℃ and the concentration of 0.03ml/L, and keeping the temperature for 60S to corrode metal impurities remained on the surface of the aluminum foil;
s9, cleaning for the fourth time to remove the nitric acid solution and the impurity corrosive substances remained on the surface of the aluminum foil;
s10, drying, putting the obtained aluminum foil into an oven, and controlling the heating temperature at 220 ℃.
Example 2
The process method for improving the pore forming uniformity of the electrode foil comprises the following steps:
s1, pretreatment; placing the aluminum foil in a weakly acidic solution (0.1 mol/L HCL solution), wherein the pH value is not less than 6, the temperature value is controlled at 70 ℃, and the holding time is 1S; only the oil stain remained on the surface of the aluminum foil is neutralized and removed, and the aluminum foil body is not corroded;
s2, cleaning for the first time, namely washing the aluminum foil by using clean water to remove the HCL solution remained on the surface of the aluminum foil;
s3, pretreating the surface of the aluminum foil; preset pits are formed on the front and back surfaces of the aluminum foil; only for the front surface of the aluminum foil, the number of the preset pits is set to be a plurality and the preset pits are uniformly distributed.
A method for forming the preset pits is proposed, and specifically comprises the following steps: and forming the preset pits on the aluminum foil by a pressing roller. A plurality of profiling bulges matched with the preset concave pit in shape are uniformly distributed on the circumferential side wall of the compression roller. The number of the press rolls is set to 2, and the two sides of the aluminum foil are symmetrically arranged to form a passing gap through which the aluminum foil freely passes. During its passage through the gap, the aluminium foil is constantly subjected to a rigid pressure from the pressure roller.
S4, performing primary corrosion reaming to increase the radial size of the preset pit; placing the aluminum foil in 0.5mol/L HCL and 1.2mol/L H at a temperature of 70 DEG C2SO4And a current was applied to the mixed solution for a holding time of 62 s. The introduced current is in gradient attenuation, and the maximum current value is 2A/cm2The minimum current value is 1.5A/cm2。
S5, cleaning for the second time, and cleaning the surface of the aluminum foil with clean water again to remove the second acid liquid remained on the surface of the aluminum foil;
s6, carrying out secondary corrosion reaming to increase the radial size of the preset pits again; placing the aluminum foil in HNO with the temperature value of 72 ℃ of 0.3mol/L3Introducing current into the solution, and keeping the time for 100 s;
s7, cleaning for the third time, and removing the third acid liquor remained on the surface of the aluminum foil by using clean water again;
s8, acid washing, namely placing the aluminum foil in 0.03ml/L nitric acid solution with the temperature value of 59 ℃ and keeping the temperature for 60S to corrode metal impurities remained on the surface of the aluminum foil;
s9, cleaning for the fourth time to remove the nitric acid solution and the impurity corrosive substances remained on the surface of the aluminum foil;
s10, drying, putting the obtained aluminum foil into an oven, and controlling the heating temperature at 220 ℃.
Example 3
The process method for improving the pore forming uniformity of the electrode foil comprises the following steps:
s1, pretreatment; placing the aluminum foil in a weakly acidic solution (0.1 mol/L HCL solution), wherein the pH value is not less than 6, the temperature value is controlled at 71 ℃, and the holding time is 1.5S; only the oil stain remained on the surface of the aluminum foil is neutralized and removed, and the aluminum foil body is not corroded;
s2, cleaning for the first time, namely washing the aluminum foil by using clean water to remove the HCL solution remained on the surface of the aluminum foil;
s3, pretreating the surface of the aluminum foil; preset pits are formed on the front and back surfaces of the aluminum foil; only for the front surface of the aluminum foil, the number of the preset pits is set to be a plurality and the preset pits are uniformly distributed.
A method for forming the pre-pits is proposed, which comprises the following steps: and forming the preset pits on the aluminum foil by a pressing roller. A plurality of profiling bulges matched with the preset concave pit in shape are uniformly distributed on the circumferential side wall of the compression roller. The number of the press rolls is set to 2, and the two sides of the aluminum foil are symmetrically arranged to form a passing gap through which the aluminum foil freely passes. During its passage through the gap, the aluminium foil is constantly subjected to a rigid pressure from the pressure roller.
S4, performing primary corrosion reaming to increase the radial size of the preset pit; placing the aluminum foil in 0.5mol/L HCL and 1.2mol/L H with the temperature value of 71 DEG C2SO4And a current was applied to the mixture for a retention time of 65 s. The introduced current is in gradient attenuation, and the maximum current value is 2A/cm2The minimum current value is 1.5A/cm2。
S5, cleaning for the second time, and cleaning the surface of the aluminum foil with clean water again to remove the second acid liquid remained on the surface of the aluminum foil;
s6, carrying out secondary corrosion reaming to increase the radial size of the preset pits again; placing the aluminum foil in HNO with the temperature value of 75 ℃ of 0.3mol/L3Introducing current into the solution, and keeping the current for 110 s;
s7, cleaning for the third time, and removing the third acid liquor remained on the surface of the aluminum foil by using clean water again;
s8, acid washing, namely placing the aluminum foil in a nitric acid solution with the temperature value of 60 ℃ of 0.03ml/L for 70S to corrode metal impurities remained on the surface of the aluminum foil;
s9, cleaning for the fourth time to remove the nitric acid solution and the impurity corrosive substances remained on the surface of the aluminum foil;
s10, drying, putting the obtained aluminum foil into an oven, and controlling the heating temperature at 220 ℃.
In examples 1, 2 and 3, the conventional step of etching the hair holes was eliminated and replaced by pre-pits. The preset pits are physical defects formed on the aluminum foil and can be used as starting points of subsequent corrosion, and finally, uniformly distributed corrosion holes are formed.
Example 4
The process method for improving the pore forming uniformity of the electrode foil comprises the following steps:
s1, pretreatment; placing the aluminum foil in a weakly acidic solution (0.1 mol/L HCL solution), wherein the pH value is not less than 6, the temperature value is controlled at 68 ℃, and the holding time is 0.8S; only the oil stain remained on the surface of the aluminum foil is neutralized and removed, and the aluminum foil body is not corroded;
s2, cleaning for the first time, namely washing the aluminum foil by using clean water to remove the HCL solution remained on the surface of the aluminum foil;
s3, pretreating the surface of the aluminum foil; laser temperature rise points are formed on the front side and the back side of the aluminum foil; only for the front of the aluminum foil, the number of the laser temperature rise points is set to be a plurality of and is uniformly distributed.
A method for forming a laser temperature rise point is proposed, which comprises the following specific steps: and forming the laser temperature rise point on the aluminum foil by a laser. The number of lasers was set to 2, the two sides of the aluminum foil were symmetrically arranged, and the temperature of the generated focal point was below 600 ℃.
S4, primary corrosion reaming, and forming an initial corrosion pit by chemically corroding the laser temperature rise point; placing the aluminum foil in 0.5mol/L HCL and 1.2mol/L H at a temperature of 68 DEG C2SO4And passing a current through the mixed solution for a retention time of 60 s. The introduced current is in gradient attenuation, and the maximum current value is 2A/cm2The minimum current value is 1.5A/cm2。
S5, cleaning for the second time, and cleaning the surface of the aluminum foil with clean water again to remove the second acid liquid remained on the surface of the aluminum foil;
s6, secondary corrosion reaming is carried out to increase the radial size of the initial corrosion pit again; placing the aluminum foil in HNO with the temperature value of 70 ℃ of 0.3mol/L3Introducing current into the solution, and keeping the current for 90 s;
s7, cleaning for the third time, and removing the third acid liquor remained on the surface of the aluminum foil by using clean water again;
s8, acid washing, namely placing the aluminum foil in a nitric acid solution with the temperature value of 58 ℃ and the concentration of 0.03ml/L, and keeping the temperature for 60S to corrode metal impurities remained on the surface of the aluminum foil;
s9, cleaning for the fourth time to remove the nitric acid solution and the impurity corrosive substances remained on the surface of the aluminum foil;
s10, drying, putting the obtained aluminum foil into an oven, and controlling the heating temperature at 220 ℃.
Example 5
The process method for improving the pore forming uniformity of the electrode foil comprises the following steps:
s1, pretreatment; placing the aluminum foil in a weakly acidic solution (0.1 mol/L HCL solution), wherein the pH value is not less than 6, the temperature value is controlled at 70 ℃, and the holding time is 1S; only the oil stain remained on the surface of the aluminum foil is neutralized and removed, and the aluminum foil body is not corroded;
s2, cleaning for the first time, namely washing the aluminum foil by using clean water to remove the HCL solution remained on the surface of the aluminum foil;
s3, pretreating the surface of the aluminum foil; laser temperature rise points are formed on the front side and the back side of the aluminum foil; only for the front of the aluminum foil, the number of the laser temperature rise points is set to be a plurality of and is uniformly distributed.
A method for forming a laser temperature rise point is proposed, which comprises the following specific steps: and forming the laser temperature rise point on the aluminum foil by a laser. The number of lasers was set to 2, the two sides of the aluminum foil were symmetrically arranged, and the temperature of the generated focal point was below 600 ℃.
S4, primary corrosion reaming, and chemical corrosion is carried out on the laser temperature rise point toForming an initial corrosion pit; placing the aluminum foil in 0.5mol/L HCL and 1.2mol/L H at a temperature of 70 DEG C2SO4And a current was applied to the mixed solution for a holding time of 62 s. The introduced current is in gradient attenuation, and the maximum current value is 2A/cm2The minimum current value is 1.5A/cm2。
S5, cleaning for the second time, and cleaning the surface of the aluminum foil with clean water again to remove the second acid liquid remained on the surface of the aluminum foil;
s6, secondary corrosion reaming is carried out to increase the radial size of the initial corrosion pit again; placing the aluminum foil in HNO with the temperature value of 72 ℃ of 0.3mol/L3Introducing current into the solution, and keeping the time for 100 s;
s7, cleaning for the third time, and removing the third acid liquor remained on the surface of the aluminum foil by using clean water again;
s8, acid washing, namely placing the aluminum foil in 0.03ml/L nitric acid solution with the temperature value of 59 ℃ and keeping the temperature for 60S to corrode metal impurities remained on the surface of the aluminum foil;
s9, cleaning for the fourth time to remove the nitric acid solution and the impurity corrosive substances remained on the surface of the aluminum foil;
s10, drying, putting the obtained aluminum foil into an oven, and controlling the heating temperature at 220 ℃.
Example 6
The process method for improving the pore forming uniformity of the electrode foil comprises the following steps:
s1, pretreatment; placing the aluminum foil in a weakly acidic solution (0.1 mol/L HCL solution), wherein the pH value is not less than 6, the temperature value is controlled at 71 ℃, and the holding time is 1.5S; only the oil stain remained on the surface of the aluminum foil is neutralized and removed, and the aluminum foil body is not corroded;
s2, cleaning for the first time, namely washing the aluminum foil by using clean water to remove the HCL solution remained on the surface of the aluminum foil;
s3, pretreating the surface of the aluminum foil; laser temperature rise points are formed on the front side and the back side of the aluminum foil; only for the front of the aluminum foil, the number of the laser temperature rise points is set to be a plurality of and is uniformly distributed.
A method for forming a laser temperature rise point is proposed, which comprises the following specific steps: and forming the laser temperature rise point on the aluminum foil by a laser. The number of lasers was set to 2, the two sides of the aluminum foil were symmetrically arranged, and the temperature of the generated focal point was below 600 ℃.
S4, primary corrosion reaming, and forming an initial corrosion pit by chemically corroding the laser temperature rise point; placing the aluminum foil in 0.5mol/L HCL and 1.2mol/L H with the temperature value of 71 DEG C2SO4And a current was applied to the mixture for a retention time of 65 s. The introduced current is in gradient attenuation, and the maximum current value is 2A/cm2The minimum current value is 1.5A/cm2。
S5, cleaning for the second time, and cleaning the surface of the aluminum foil with clean water again to remove the second acid liquid remained on the surface of the aluminum foil;
s6, secondary corrosion reaming is carried out to increase the radial size of the initial corrosion pit again; placing the aluminum foil in HNO with the temperature value of 75 ℃ of 0.3mol/L3Introducing current into the solution, and keeping the current for 110 s;
s7, cleaning for the third time, and removing the third acid liquor remained on the surface of the aluminum foil by using clean water again;
s8, acid washing, namely placing the aluminum foil in a nitric acid solution with the temperature value of 60 ℃ of 0.03ml/L for 70S to corrode metal impurities remained on the surface of the aluminum foil;
s9, cleaning for the fourth time to remove the nitric acid solution and the impurity corrosive substances remained on the surface of the aluminum foil;
s10, drying, putting the obtained aluminum foil into an oven, and controlling the heating temperature at 220 ℃.
In examples 4, 5 and 6, the conventional step of etching the via hole is eliminated and replaced by a laser temperature increasing point. The laser temperature rise points are physical defects formed on the aluminum foil and can be used as starting points of subsequent corrosion, and corrosion holes which are uniformly distributed are formed finally. After the laser temperature-raising points are formed on the aluminum foil, the aluminum foil enters the primary corrosion reaming in time (the circulation speed is very high, and the interval time is generally less than 5 s), so that after the aluminum foil enters the acid liquid tank, even if the aluminum foil is made of high-heat-conductivity material, the laser temperature-raising points have larger temperature difference compared with other adjacent areas, the corrosion rate of the laser temperature-raising points is favorably accelerated, the initial corrosion points are quickly formed, and other low-temperature areas are not as long as the initial corrosion points are formed due to the slow corrosion rate.
At this point, it is known that the corrosion progress and the final corrosion quality of the aluminum foil are directly related to the shape and arrangement state of the predetermined pits or laser heating points. In view of this, in the above embodiments 1, 2 and 3, the lateral cross section of the pre-pits is preferably circular. Assuming that the depth value of the preset pit is d, the diameter size value is r and the mutual spacing value is w, d is more than or equal to 20 nm and less than or equal to 30nm, r is more than or equal to 30nm and less than or equal to 50nm, and w is more than or equal to 200nm and less than or equal to 600 nm. In the above-described embodiments 4, 5 and 6, the laser temperature rise point is preferably circular in transverse cross section. Assuming that the depth value of the laser temperature rise point is d2, the diameter size value is r2, and the mutual spacing value is w2, then 20 nm-20 nm d 2-30 nm, 30 nm-30 nm r 2-50 nm, and 200 nm-200 nm w 2-600 nm.
Table 1 shows the specific volume test results of the aluminum foil obtained in examples 1 to 6
TABLE 1
The following conclusions can be drawn after data analysis of table 1: 1) compared with the traditional preparation method, the specific volume, the pore density and the pore occupancy parameters of the aluminum foil prepared by the method are greatly improved; 2) in step S3, namely, in the aluminum foil surface pretreatment stage, no matter the initial corrosion point adopts a preset pit or a laser temperature-raising point, the specific volume test data of the finally prepared aluminum foil pieces are basically consistent, and only slight differences exist; 3) referring to the specific volume of the aluminum foil prepared in example 2 is significantly better than that of examples 1 and 3, the reason for this is that the corrosion rate of the pre-pits is affected to a certain extent due to the difference in temperature and retention time of the acid solution used in the steps of primary corrosion reaming, secondary corrosion reaming and acid washing; 4) referring to example 5, the specific volume of the aluminum foil prepared in example 4 is significantly better than that of example 6, because the etching rate of the laser temperature rising point is affected to some extent due to the difference in the temperature and the holding time of the acid solution used in the steps of primary etching reaming, secondary etching reaming and pickling.
Actual experiments prove that a series of initial corrosion points with good distribution density uniformity and consistent appearance can be formed on the surface of the aluminum foil by the aid of the preset pits or laser temperature raising points, the occurrence of hole merging phenomenon is effectively eliminated, further, good bedding is made for effectively improving the uniformity of subsequent electrolytic corrosion of the aluminum foil, and finally, the uniformity of the capacity of the electrode foil is improved (as shown in figures 1 and 2).
In addition, it should be noted that: 1) in the aluminum foil drying treatment stage, the heating cavity of the drying oven is filled with inert gas all the time, so that the oxidation phenomenon of the aluminum foil after the temperature rise is avoided, and the surface of the aluminum foil is ensured to have good cleanliness; 2) when the aluminum foil is subjected to the heat treatment, cooling is required. The following two common ways are available: a. and transferring the aluminum foil after the heat treatment to the external environment, and naturally cooling. Then the surface of the electrode foil is seriously oxidized due to the action of oxygen in the transfer process and the subsequent cooling process, so that the structural strength and the specific volume performance of the formed electrode foil are influenced; b. the aluminum foil after heat treatment is directly sealed in the oven for cooling, so that the oxidation phenomenon can be effectively avoided, but the equipment utilization rate of the oven is extremely low due to the fact that a large amount of time needs to be consumed, and the purchase number and cost of equipment are increased. In view of this, a preferred cooling solution is proposed here, in particular as follows: the aluminum foil after high-temperature heat treatment is continuously kept in the oven, and inert gases (such as nitrogen and argon) with the temperature lower than 10 ℃ are directly filled into the inner cavity of the oven, so that the cooling time can be greatly shortened, and the oxidation phenomenon is avoided.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (13)
1. A process method for improving the uniformity of electrode foil pores is characterized by comprising the following steps:
s1, pretreatment; placing the aluminum foil in the first acid solution, wherein the temperature value is T1, and the holding time is T1; the first acid liquid is weakly acidic, and the pH value is not less than 6;
s2, cleaning for the first time to remove the first acid liquor remained on the surface of the aluminum foil;
s3, pretreating the surface of the aluminum foil; uniformly distributed preset pits or laser heating points are formed on the front surface and the back surface of the aluminum foil;
s4, primary corrosion reaming; placing the aluminum foil in a second acid solution with a temperature value of T2, and introducing current into the second acid solution for a holding time of T2;
s5, cleaning for the second time to remove the second acid liquor remained on the surface of the aluminum foil;
s6, secondary corrosion reaming; placing the aluminum foil in a third acid solution with a temperature value of T3, and introducing current into the third acid solution for a holding time of T3;
s7, cleaning for the third time to remove the third acid liquor remaining on the surface of the aluminum foil;
s8, acid washing, namely placing the aluminum foil in fourth acid liquor with a temperature value of T4, and keeping the temperature for T4 to corrode metal impurities remained on the surface of the aluminum foil;
s9, cleaning for the fourth time to remove the fourth acid solution and the impurity corrosive substances remained on the surface of the aluminum foil;
and S10, drying to dry the aluminum foil.
2. The process method for improving the uniformity of the electrode foil hair holes according to claim 1, wherein the transverse cross section of the preset concave pits is circular; assuming that the depth value of the preset pits is d1, the diameter size value is r1, and the mutual spacing value is w1, 20 nm-30 nm d 1-50 nm, 30 nm-50 nm r 1-600 nm w 1-600 nm.
3. The method as claimed in claim 2, wherein the predetermined recesses are formed on the aluminum foil by a pressing roller; a plurality of profiling protrusions matched with the preset pits in shape are uniformly distributed on the circumferential side wall of the compression roller; the number of the compression rollers is set to be 2, and the compression rollers are symmetrically arranged on two sides of the aluminum foil so as to form a passing gap through which the aluminum foil can freely pass; during its passage through the through-gap, the aluminium foil is constantly subjected to a rigid pressing force from the pressing roller.
4. The process of claim 1, wherein the laser temperature rise point is formed on the aluminum foil by a laser; the number of the lasers is set to be 2, the lasers are symmetrically arranged on two sides of the aluminum foil, and the temperature of a generated focusing point is lower than 600 ℃; the transverse section of the laser temperature rise point is circular; assuming that the depth value of the laser temperature rise point is d2, the diameter size value is r2, and the mutual distance value is w2, then 20 nm-20 nm d 2-30 nm, 30 nm-30 nm r 2-50 nm, and 200 nm-200 nm w 2-600 nm.
5. The process for improving the uniformity of electrode foil pores in accordance with claim 1, wherein in step S1, the first acid solution is 0.1mol/L HCL solution, T1 ≦ 71 ℃. 0.8S ≦ T1 ≦ 1.5S.
6. The process for improving the uniformity of electrode foil hair holes as claimed in claim 5, wherein T1=70 ℃ and T1=1 s.
7. The process of claim 1, wherein in step S4, the second acid solution is 0.5mol/L HCL and 1.2mol/L H2SO4The temperature T2 is more than or equal to 68 ℃ and less than or equal to 71 ℃, and the temperature T2 is more than or equal to 60S and less than or equal to 65S; the current is in gradient attenuation, and the maximum current value is 2A/cm2The minimum current value is 1.5A/cm2。
8. The process for improving the uniformity of electrode foil hair holes of claim 7, wherein T2=70 ℃ and T2=60 s.
9. The process method for improving the uniformity of electrode foil pores according to claim 1, wherein in step S6, the third acid solution is 0.3mol/L HNO3The solution has T3 of more than or equal to 70 ℃ and less than or equal to 75 ℃ and T3 of more than or equal to 90S and less than or equal to 110S; the current is constant and is stabilized at 0.6A/cm2。
10. The process for improving the uniformity of electrode foil hair holes of claim 9, wherein T3=72 ℃ and T3=100 s.
11. The process for improving the uniformity of the electrode foil pores in accordance with claim 1, wherein in step S8, the fourth acid solution is 0.03ml/L nitric acid solution, T4 is more than or equal to 58 ℃ and less than or equal to 60 ℃, and T4 is more than or equal to 60S and less than or equal to 70S.
12. The process for improving the uniformity of electrode foil hair holes of claim 11, wherein T4=60 ℃ and T4=60 s.
13. The process for improving the uniformity of the pores in the electrode foil according to claim 1, wherein in step S10, the aluminum foil obtained in step S9 is placed in an oven, and the heating temperature is controlled below 220 ℃; the heating cavity of the oven is always filled with inert gas.
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