KR102364363B1 - Process for preparing current collector for pseudo capacitor - Google Patents

Abstract

The manufacturing method according to the present invention is to form a nickel plating layer by an electroless plating method in a simpler process by pre-treating and activating the surface of an aluminum foil under specific conditions to easily manufacture a current collector for a water-based electrolyte water capacitor. , the current collector for water capacitors manufactured according to this method uses inexpensive aluminum foil instead of expensive nickel (Ni) and titanium (Ti) current collectors, and even in water capacitors using water-based electrolytes, high electrical conductivity and low interface with electrodes In addition to resistance characteristics, there is an excellent effect of electrochemical stability according to voltage change.

Description

Manufacturing method of current collector for water capacitor {PROCESS FOR PREPARING CURRENT COLLECTOR FOR PSEUDO CAPACITOR}

The present invention relates to a method for manufacturing a current collector for a water capacitor.

As energy demand increases significantly around the world, interest in energy storage technology is increasing, and as the field of application expands to energy for mobile phones, camcorders, notebook PCs, and even electric vehicles, efforts to research and develop electrochemical devices are increasing. are becoming increasingly concrete.

In particular, recently, interest in rechargeable batteries capable of charging and discharging is emerging, and among the currently applied secondary batteries, lithium secondary batteries developed in the early 1990s are in the spotlight because of their high operating voltage and extremely high energy density. . At the same time, research on a supercapacitor as an energy storage device having a higher energy density than that of a conventional capacitor and a higher output than a typical lithium ion battery is being conducted in various fields. Such supercapacitors can be simply classified into electrical double-layer capacitors (EDLCs) and pseudo-capacitors according to the mechanism of storing energy.

These energy storage devices are mostly composed of an anode and a cathode made of carbon material or transition metal oxide, and a non-aqueous electrolyte. However, non-aqueous electrolytes made of organic solvents used in lithium ion batteries, water capacitors, and supercapacitors, etc. are highly flammable, which leads to poor safety and low ionic conductivity, limiting the application of high-output products. Accordingly, as an attempt to increase safety and output, lithium ion batteries and water capacitors. A lot of research is being done to use an aqueous electrolyte for supercapacitors. However, in the case of using such an aqueous electrolyte, since the current collector of the water capacitor is exposed to the aqueous electrolyte, there is a problem in that electrochemical stability is deteriorated according to a voltage change during operation.

On the other hand, the current collector of a water capacitor requires high electrical conductivity, electrochemical stability, and low interfacial resistance with electrodes. In particular, in the case of a metal current collector, it is important to select an appropriate current collector because the electrochemical stability in the electrolyte varies greatly depending on the type of metal. For this reason, nickel (Ni) and titanium (Ti) current collectors with excellent corrosion resistance are mainly used in water-based capacitors using aqueous electrolytes. However, in this case, since the current collector occupies a significant portion of the total cell price, price competitiveness is not good in the actual commercial market.

Therefore, even in a water-based capacitor using an aqueous electrolyte, research on a current collector for a water-based capacitor having excellent electrochemical stability according to voltage change as well as high electrical conductivity and low interfacial resistance characteristics with electrodes is continuously required.

An object of the present invention is to provide a method for manufacturing a current collector for a water capacitor.

Another object of the present invention is to provide a current collector for a water capacitor manufactured by the above manufacturing method.

In order to solve the above problems, the present invention includes the steps of pre-treating the surface of an aluminum foil (step 1) under a temperature condition of 40 to 80 ℃ using an aqueous alkali solution; Activating the surface of the pretreated aluminum foil under a temperature condition of 50 to 80° C. using an aqueous inorganic acid solution having a concentration of 25 to 50 vol% (step 2); and forming a nickel plating layer on the surface of the activated aluminum foil by an electroless plating method using a plating solution containing a nickel salt and a phosphorus-based reducing agent (step 3); It provides a manufacturing method of

Hereinafter, the present invention will be described in detail for each step.

aluminum of foil Steps to pretreat the surface (Step 1)

Step 1 is a pretreatment step of cleaning the surface of the aluminum foil so that the electroless plating using the nickel plating solution is effectively performed in the subsequent step.

In particular, the pretreatment step of step 1 corresponds to de-oxidizing the oxide film on the surface of the aluminum foil.

When the aluminum foil has electrochemical stability and electrical conductivity suitable for a water-based electrolyte water capacitor, it serves as a substrate on which a nickel (Ni) plating layer with excellent corrosion resistance is formed. In addition, the aluminum foil may have an average thickness of about 0.01 to 0.05 mm or about 0.015 to 0.04 mm. The aluminum foil may have an average thickness of about 0.01 mm or more in terms of securing sufficient support when forming the nickel plating layer, and may be about 0.05 mm or less in terms of realizing excellent electrical conductivity without increasing the weight of the final device.

Step 1 consists of pre-treating the surface of the aluminum foil under a temperature condition of about 40 to 80 ℃, or about 45 to 70 ℃, or about 50 to 65 ℃ using an aqueous alkali solution. The pretreatment step should be performed at about 40° C. or higher in order to effectively remove the oxide film on the surface of the aluminum foil, and should be performed at about 80° C. or less in terms of preventing excessive corrosion or deformation of the aluminum foil. .

In addition, the pretreatment time of step 1 may be about 5 to 60 seconds, or about 10 to 50 seconds, or about 20 to 45 seconds. The pretreatment step may be performed for about 5 seconds or more to sufficiently remove the oxide film on the surface of the aluminum foil, and may be performed for about 60 seconds or less in terms of improving overall process efficiency.

The pretreatment step may be performed by immersing the aluminum foil in an aqueous alkali solution.

The aqueous alkali solution may be one containing an alkali compound with high solubility in water, and preferably contains at least one of alkali compounds such as sodium hydroxide (NaOH), potassium hydroxide (KOH), and lithium hydroxide (LiOH). can

The concentration of the aqueous alkali solution may be about 5 to 55 wt% (wt%), or about 10 to 50 wt%. In addition, the pH of the aqueous alkali solution may be about 9 to 14, or about 10 to 14. The concentration and pH of the aqueous alkali solution may be applied within the ranges as described above in terms of improving process safety and efficiency while effectively removing the oxide film on the surface of the aluminum foil.

In step 1, the surface of the aluminum foil is pretreated under a specific temperature condition using an aqueous alkali solution, thereby removing the oxide film and performing an effective plating process.

of step 1 above pre-treated aluminum of foil Activating the surface (Step 2)

The step 2 is a step of activating the surface of the aluminum foil, which has been cleaned by removing the oxide film and the like through the pretreatment of step 1, using a high-temperature aqueous inorganic acid solution.

In general, the conventional process of electroless plating nickel on a metal surface performs a zincate treatment process before plating, thereby forming a Zn layer on the metal surface to make a nucleation site. . However, since such a zincate treatment process has to go through a multi-step process, the overall process becomes very complicated, and there is a problem of treating the waste zincate solution remaining after the process is completed.

Accordingly, in the present invention, electroless plating using a nickel plating solution in a subsequent step by treating the aluminum foil pretreated in step 1 with a high temperature aqueous solution of inorganic acid to activate it without a conventional zincate treatment process It is characterized by making it happen.

In step 2, the surface of the pre-treated aluminum foil is activated under a temperature condition of about 50 to 80 ℃, or about 60 to 80 ℃, or about 65 to 80 ℃ using an inorganic acid aqueous solution (activation) is made up of The activation treatment step should be performed at a high temperature of about 50° C. or higher, and when nickel nucleation sites are sufficiently formed on the surface of the aluminum foil, the subsequent nickel plating process can be effectively performed. In addition, the activation treatment step should be performed at about 80° C. or less in terms of preventing excessive corrosion or deformation of the aluminum foil in the inorganic acid treatment process.

The activation treatment time of step 2 may be about 30 to 100 seconds, or about 30 to 90 seconds, or about 35 to 80 seconds. The activation step can be performed for about 30 seconds or more in terms of sufficiently making the roughening process in which nickel nucleation sites are formed on the surface of the aluminum foil, and in about 100 seconds or less in terms of enhancing the overall process efficiency. can be done

The activation treatment step may be performed by immersing the aluminum foil in a high temperature aqueous inorganic acid solution.

The inorganic acid aqueous solution may include an inorganic acid compound exhibiting sufficient acidity to roughen the surface of the aluminum foil from which the oxide film has been removed. The inorganic acid aqueous solution may include at least one of inorganic acid compounds such as nitric acid (HNO ₃ ), sulfuric acid (H ₂ SO ₄ ), and phosphoric acid (H ₂ PO ₄ ).

The concentration of the inorganic acid aqueous solution may be about 20 to 55 vol% (vol%), or about 25 to 50 vol%. In addition, the pH of the inorganic acid aqueous solution may be about 1 to 4.5, or about 1 to 4. The concentration and pH of the inorganic acid aqueous solution may be applied within the ranges as described above in terms of enhancing process safety and efficiency while sufficiently performing a roughening process in which nickel nucleation sites are formed on the surface of the aluminum foil.

In step 2, the surface of the aluminum foil is micro-etched and roughened with an aqueous inorganic acid solution such as HNO ₃ under a high temperature condition of about 50 to 80 ° C., so that the known zincate treatment Even without a process, it is possible to easily create a nucleation site that allows nickel to be easily plated in the subsequent electroless nickel plating process.

Activated aluminum in step 2 above of foil Nickel on the surface the plating layer forming step (step 3)

Step 3 is a step of forming a nickel plating layer by an electroless plating method on the surface of the aluminum foil that has been activated according to step 2 above.

The nickel electroless plating process of step 3 is a plating method in which Ni is reduced on the surface of a target material by a spontaneous catalytic reaction to form a coating layer, and is characterized by a high phosphorus content in the coating layer. For example, the phosphorus content in the coating layer may be about 8 wt% or more or 8 to 15 wt%. In general, the electroless plating process is a coating technology commercialized in many fields because the process is simple, economical, and applicable to various target materials. Since a nickel coating film that is densely grown to a constant thickness is advantageous in corrosion resistance, both electrochemical stability and electrical conductivity can be satisfied.

The electroless plating method is performed using a plating solution containing a nickel salt and a phosphorus-based reducing agent.

The nickel salt exists in a dissociated state in the electroless plating solution, and a component capable of forming a nickel plating layer by causing a substitution reaction with aluminum may be used. Preferably, at least one of nickel compounds such as NiSO ₄ , NiCl ₂ , and Ni(NO ₃ ) ₂ may be used.

The nickel salt may be used at a concentration of about 10 to 40 g/L, or about 15 to 35 g/L, based on the total volume of the plating solution. The content of the nickel salt may be added at a concentration of about 10 g/L or more to form a nickel plating layer sufficient to express high electrical conductivity, electrochemical stability, and low interfacial resistance characteristics with an electrode when applied as a current collector for a water capacitor. In consideration of the ease of handling of the electroless plating solution, it can be used at a concentration of about 40 g/L or less.

The phosphorus-based reducing agent effectively undergoes a substitution reaction with nickel and aluminum, which are plating metals, in the electroless plating method, and the reduction plating reaction continues to form a sufficient plating layer. Preferably, at least one of phosphorus compounds such as NaH ₂ PO ₂ , KH ₂ PO ₂ , and NH ₄ H ₂ PO ₂ may be used.

The phosphorus-based reducing agent may be used at a concentration of about 10 to 40 g/L, or about 20 to 35 g/L g/L, based on the total volume of the plating solution. The content of the phosphorus-based reducing agent may be added at a concentration of about 10 g/L or more in terms of allowing a sufficient nickel and aluminum substitution reaction to occur by the electroless plating method, and about 40 g/L in consideration of the ease of handling of the electroless plating solution, etc. It can be used in concentrations of L or less.

The plating solution used in the nickel electroless plating method may further include additional components such as a complexing agent, a buffer, and a stabilizer in addition to the nickel salt and the phosphorus-based reducing agent. For example, the plating solution is sodium acetate, sodium citrate, sodium succinate, lactic acid, malic acid as a complexing agent together with a nickel salt and a phosphorus-based reducing agent. ) and the like; at least one of compounds such as ammonium chloride and boric acid as a buffer; at least one of compounds such as potassium iodate and lead chloride as a stabilizer; and water.

On the other hand, the electroless plating process of step 3 may be performed at a temperature of about 70 to 95 ℃, or about 70 to 85 ℃. In addition, the electroless plating process may be performed for about 20 to 60 minutes (min), or about 30 to 60 minutes (min). Here, the electroless plating process may be performed at a temperature and time within the range as described above in terms of enhancing overall process efficiency while allowing a dense nickel coating film to grow to a predetermined thickness on the surface of an aluminum foil.

The nickel plating layer formed on the surface of the aluminum foil through the electroless plating method of step 3 is densely grown to a uniform thickness and exhibits high adhesion. In particular, the nickel plating layer may have an average thickness of about 50 nm or more, or 50 nm to 2000 nm, or about 60 nm or more. The average thickness of the nickel plating layer may be about 50 nm or more in terms of high electrical conductivity, electrochemical stability, and low interfacial resistance characteristics with electrodes when applied as a current collector for a water capacitor.

In step 3, a uniform nickel plating layer can be formed by a nickel electroless plating method after activating the surface of the aluminum foil with an aqueous solution of a high temperature inorganic acid. It is possible to obtain an excellent effect of electrochemical stability according to voltage change as well as interfacial resistance characteristics.

for water capacitor current collector

In addition, the present invention provides a current collector for a water capacitor manufactured by the above-described manufacturing method. In particular, the current collector for the water capacitor includes an aluminum foil having a nickel plating layer formed thereon in the same manner as described above.

The current collector has high electrical conductivity, electrochemical stability, and low interfacial resistance with electrodes. In particular, even in a water capacitor using an aqueous electrolyte, the electrochemical stability according to voltage conversion in the aqueous electrolyte during operation is very excellent.

In addition, the present invention provides an electrode assembly [capacitor] including the current collector for the water capacitor. As an energy storage material, a water capacitor has the advantage of having improved energy density using intercalation or redox reaction on the electrode material surface along with high output and cycle stability, which are basic characteristics of a capacitor.

As in the following examples, when the aluminum foil with a nickel plating layer formed according to the present invention is used for manufacturing a current collector for a water capacitor, an inexpensive aluminum foil is used instead of an expensive nickel (Ni), titanium (Ti) current collector. In addition to high electrical conductivity and low interfacial resistance characteristics with electrodes, electrochemical stability according to voltage change in aqueous electrolytes is very excellent.

As described above, the manufacturing method according to the present invention pre-treats and activates the surface of an aluminum foil under specific conditions to form a nickel plating layer using an electroless plating method in a simpler process to produce a current collector for an aqueous electrolyte water capacitor. Because it is easy to manufacture, the current collector for a water supply capacitor manufactured in this way has high electrical conductivity and high electrical conductivity even in a water supply capacitor using an aqueous electrolyte even by using an inexpensive aluminum foil instead of an expensive nickel (Ni) or titanium (Ti) current collector. It has an excellent effect of electrochemical stability according to voltage change along with low interfacial resistance characteristics with electrodes.

1 shows an SEM image of the surface of an aluminum foil that was subjected to the activation process of step 2 at a high temperature according to Example 1 of the present invention.
2 shows an SEM image of the surface of the electroless nickel plated aluminum foil current collector according to Example 1 of the present invention.
3 shows an SEM image of the surface of an aluminum foil that has been subjected to the activation process of step 2 at a high temperature according to Example 2 of the present invention.
4 shows an SEM image of the surface of the electroless nickel-plated aluminum foil current collector according to Comparative Example 2 of the present invention.
5 shows an SEM image of the surface of an aluminum foil that was subjected to the activation process of step 2 at a low temperature according to Comparative Example 3 of the present invention.
6 shows an SEM image of the surface of an aluminum foil that was subjected to the activation process of step 2 at a low temperature according to Comparative Example 4 of the present invention.
7 is a graph measured by cyclic voltammetry in the electrode system of Experimental Example 1 using an aluminum foil current collector plated with electroless nickel according to Example 1 of the present invention (x-axis: Ag/AgCl Voltage versus reference electrode, y-axis: amount of current).
8 is a graph measured by cyclic voltammetry in the electrode system of Experimental Example 1 using an aluminum foil current collector subjected to only pretreatment according to Comparative Example 1 of the present invention (x-axis: Ag /AgCl voltage compared to the reference electrode, y-axis: amperage).

Hereinafter, preferred examples are presented to help the understanding of the present invention. However, the following examples are only provided for easier understanding of the present invention, and thus the content of the present invention is not limited thereto.

Example One

The entire nickel plating (Ni-plating) process was performed in the order of pretreatment (deoxidizing) in step 1, activation treatment in step 2, and nickel plating (Ni-plating) in step 3. A distilled water rinsing is included between each step.

(Step 1)

Aluminum foil was prepared with an average thickness of about 0.02 mm (Fukuda Metal). The aluminum foil was immersed in about 10 wt% of an aqueous NaOH solution under a condition of about 60° C. for about 30 seconds (sec), and the surface of the aluminum foil was pretreated (deoxidizing).

(Step 2)

The pre-treated aluminum foil was immersed in 25 vol% of HNO ₃ aqueous solution at about 70° C. for about 40 sec to activate the surface of the aluminum foil.

The result of observation with a scanning microscope (SEM, Scanning Electron Microscope) image of the aluminum foil surface activated through step 2 is shown in FIG. 1 , and as shown in FIG. 1 , the surface is roughened and the subsequent It was directly confirmed that a nucleation site of Ni was created in the electroless plating process and the surface of the aluminum foil was effectively activated.

(Step 3)

The activated aluminum foil contains 25 g/L of NiSO ₄ .6H ₂ O, 30 g/L of NaH ₂ PO ₂ .H ₂ O, 40 g/L of sodium citrate, and sodium acetate trihydrate. (sodium acetate trihydrate) 15 g/L, potassium iodate 20 mg/L, N-hexadecyl trimethyl ammonium chloride at a content of 5 mg/L A nickel plating layer was formed on the surface of the activated aluminum foil by an electroless plating method for about 30 min under a condition of about 85 ° C.

The result of observing the thus generated nickel plating layer with a scanning electron microscope (SEM) image is shown in FIG. 2 , and it can be seen that a uniform Ni plating layer is formed as shown in FIG. 2 .

Example 2

A nickel plating layer was formed on the surface of the aluminum foil in the same manner as in Example 1, except that in the activation process of step 2, the concentration of the HNO ₃ aqueous solution was changed to 50 vol%.

The result of observation with a scanning microscope (SEM, Scanning Electron Microscope) image of the aluminum foil surface activated through step 2 is shown in FIG. 3 , and as shown in FIG. 3 , the surface is roughened and the subsequent electroless It was directly confirmed that the nucleation site of Ni was created in the plating process and the surface of the aluminum foil was effectively activated.

In addition, as a result of observing the thus produced nickel plating layer with a scanning electron microscope (SEM) image, it was found that a uniform Ni plating layer was formed.

comparative example One

Without the activation treatment (activation) of step 2 and the nickel plating (Ni-plating) treatment of step 3, the pretreatment (deoxidizing) of step 1 was performed as follows.

(Step 1)

Aluminum foil was prepared with an average thickness of about 0.02 mm (Fukuda Metal). The aluminum foil was immersed in about 10 wt% of an aqueous NaOH solution at about 60° C. for about 30 sec to pre-treat and deoxidize the surface of the aluminum foil.

comparative example 2

After the pretreatment (deoxidizing) of step 1, the nickel plating of step 3 (Ni-plating) was immediately performed without the activation treatment of step 2 (Ni-plating).

(Step 1)

Aluminum foil was prepared with an average thickness of about 0.02 mm (Fukuda Metal).

The aluminum foil was immersed in about 10 wt% of an aqueous NaOH solution at about 60° C. for about 30 sec to pre-treat and deoxidize the surface of the aluminum foil.

(Step 3)

Without the activation treatment process of step 2, the pre-treated aluminum foil was used with 25 g/L of NiSO ₄ .6H ₂ O, 30 g/L of NaH ₂ PO ₂ .H ₂ O, and sodium citrate. 40 g / L, sodium acetate trihydrate 15 g / L, potassium iodate 20 mg / L, N-hexadecyl trimethyl ammonium chloride (N-hexadecyl trimethyl ammonium chloride) A nickel plating layer was formed on the surface of the activated aluminum foil by an electroless plating method for about 30 min under a condition of about 85° C. using a plating solution containing a content of 5 mg/L.

The result of observing the thus generated nickel plating layer with a scanning electron microscope (SEM) image is shown in FIG. 4 , and it can be seen that a uniform Ni plating layer is not formed as shown in FIG. 4 .

comparative example 3

A nickel plating layer was formed on the surface of the aluminum foil in the same manner as in Example 1, except that the activation process of step 2 was performed at room temperature.

As a result of observation with a scanning electron microscope (SEM) image of the surface of the aluminum foil treated with HNO ₃ aqueous solution at low temperature in step 2, the oxide film was removed in step 1 and the remaining components were removed without surface activation. It was directly confirmed that only (de-smutting) was performed.

In addition, the result of observing the thus generated nickel plating layer with a scanning electron microscope (SEM) image is shown in FIG. 5 , and it can be seen that a uniform Ni plating layer is not formed as shown in FIG. 5 .

comparative example 4

A nickel plating layer was formed on the surface of the aluminum foil in the same manner as in Example 2, except that the activation process of step 2 was performed at room temperature.

As a result of observation with a scanning electron microscope (SEM) image of the surface of the aluminum foil treated with HNO ₃ aqueous solution at low temperature in step 2, the oxide film was removed in step 1 and the remaining components were removed without surface activation. It was directly confirmed that only (de-smutting) was performed.

In addition, the result of observing the thus produced nickel plating layer with a scanning electron microscope (SEM) image is shown in FIG. 6 , and it can be seen that a uniform Ni plating layer is not formed as shown in FIG. 6 .

Experimental example

After preparing electrodes using the electroless nickel-plated aluminum foil prepared in Example 1 or the Al foil subjected to only the pretreatment of step 1 according to Comparative Example 1 as current collectors, respectively, CV and constant current measurement was performed, and the results are shown in Table 1 below.

For electrochemical performance measurement, active material (LiTi ₂ (PO ₄ ) ₃ ):conductive material (acetylene black):binder (PVDF) was dispersed in NMP in a mass ratio of 85:10:5, and then a loading amount of about 2.65 mg/cm ² (based on total solids) was applied on a glassy carbon electrode.

CV and constant current measurements were performed in 1 M Li ₂ SO ₄ aqueous solution as an Ag/AgCl reference electrode.

Specific capacitance (at 5th cycle, F/g) Example 1 263.3 Comparative Example 1 164.42

Meanwhile, graphs measured by cyclic voltammetry in the electrode system of Experimental Example 1 using aluminum foils prepared according to Example 1 and Comparative Example 1 as a current collector are shown in FIGS. 7 and 8 , respectively.

As shown in FIG. 7, according to Example 1, in the CV measurement using Ni-plated Al foil as a current collector, an intercalation peak of LiTi ₂ (PO ₄ ) ₃ was clearly observed and 5 remained stable throughout the cycle.

On the other hand, as shown in FIG. 8, in the case of the Al foil subjected to only the pretreatment of step 1 according to Comparative Example 1, it was observed that the peak decreased as the charge and discharge were repeated in the CV measurement, which The increase in electrical resistance due to oxide film growth is considered to be the cause.

Claims (18)

Pre-treating the surface of the aluminum foil (step 1) under a temperature condition of 40 to 80 ℃ using an aqueous alkali solution (step 1);
Without a zincate treatment process for the pretreated aluminum foil, using an inorganic acid aqueous solution having a concentration of 25 to 50 vol% under a temperature condition of 65 ° C to 80 ° C of the pretreated aluminum foil activating the surface (step 2); and
Including; forming a nickel plating layer on the surface of the activated aluminum foil by an electroless plating method using a plating solution containing a nickel salt and a phosphorus-based reducing agent (step 3);
A method of manufacturing a current collector for a water capacitor.
According to claim 1,
The aluminum foil has an average thickness of 0.01 to 0.05 mm,
manufacturing method.
According to claim 1,
The alkali is at least one selected from the group consisting of sodium hydroxide, potassium hydroxide, and lithium hydroxide,
manufacturing method.
According to claim 1,
The concentration of the aqueous alkali solution is 5 to 55% by weight,
manufacturing method.
According to claim 1,
In step 1, performing the pre-treatment step by an immersion method,
manufacturing method.
According to claim 1,
The pretreatment time of step 1 is 5 to 60 seconds,
manufacturing method.
According to claim 1,
The inorganic acid is at least one selected from the group consisting of nitric acid, sulfuric acid, and phosphoric acid,
manufacturing method.
According to claim 1,
In step 2, performing the activation treatment step by an immersion method,
manufacturing method.
According to claim 1,
The activation processing time of step 2 is 30 to 100 seconds,
manufacturing method.
The method of claim 1,
The nickel salt is at least one selected from the group consisting of NiSO ₄ , NiCl ₂ , and Ni(NO ₃ ) ₂ ,
manufacturing method.
According to claim 1,
The phosphorus-based reducing agent is at least one selected from the group consisting of NaH ₂ PO ₂ , KH ₂ PO ₂ , and NH ₄ H ₂ PO ₂ ,
manufacturing method.
According to claim 1,
The nickel salt is contained in a concentration of 10 to 40 g / L,
manufacturing method.
According to claim 1,
The phosphorus-based reducing agent is included in a concentration of 10 to 40 g / L,
manufacturing method.
According to claim 1,
The plating solution further comprises at least one selected from the group consisting of a complexing agent, a buffer, and a stabilizer,
manufacturing method.
According to claim 1,
The electroless plating temperature of step 3 is 70 to 95 ℃,
manufacturing method.
According to claim 1,
The electroless plating time of step 3 is 20 to 60 minutes,
manufacturing method.
According to claim 1,
The nickel plating layer has an average thickness of 50 nm or more,
manufacturing method.
The current collector for a water capacitor, which is manufactured by the manufacturing method of any one of claims 1 to 17.

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