KR20080026888A - Electrochemical device having improved wettability between electrode and electrolyte, and method for preparing the same - Google Patents

Abstract

A method for manufacturing an electrochemical device having improved wettability between an electrode and an electrolyte is provided to improve performances of an electrochemical device and reduce a production process time of the electrochemical device. A method for manufacturing an electrochemical device comprising an oxidation electrode, a reduction electrode, and an electrolyte and having improved wettability between electrodes and an electrolyte, includes a step of applying an electrical perturbation in an alternating current or pulse form to both ends of the oxidation electrode and reduction electrode between which the electrolyte is interposed. The electrochemical device is at least one selected from the group consisting of a battery, a capacitor, a fuel cell, and an electrochromic device.

Description

ELECTROCHEMICAL DEVICE HAVING IMPROVED WETTABILITY BETWEEN ELECTRODE AND ELECTROLYTE, AND METHOD FOR PREPARING THE SAME

1 is a schematic diagram schematically illustrating the principle of the electrowetting.

2 is a schematic diagram schematically illustrating the concept of the present invention.

The present invention relates to an electrochemical device having an improved wettability between an electrode and an electrolyte, and a method of manufacturing the same, and specifically, by applying electrical perturbation to an electrochemical device using the principle of electrowetting, The present invention relates to a method capable of improving the performance of an electrochemical device by improving the wettability between an electrode constituting the device and an electrolyte, and shortening the manufacturing time of the electrochemical device.

Electrowetting refers to the contact angle of an electrolyte and the interface between two fluids by controlling the interfacial tension between the electrolyte and the insulator by applying a voltage from the outside while a thin insulator is inserted between the electrolyte (or conductive fluid) and the electrode. Changing skills refers to technology. Whereas existing studies on wettability are about wettability itself, which is represented by contact angle, and has static characteristics, electrowetting has a dynamic characteristic of controlling the contact angle by using an electrical signal. Application is possible. For example, a lab on a chip that can be examined through a drop of blood or DNA, an electronic paper that can be folded freely, and an electronic paper that can be adjusted at close range can be applied to a mobile phone. The liquid lens etc. which are considered are mentioned.

On the other hand, in the manufacturing process of electrochemical devices such as batteries (battery), capacitors, electrochromic devices (electrochromic devices), etc., the impregnation of the electrolyte or the wetting of the electrode (wetting) generally takes a long time. It is a process. Furthermore, as the thickness of the electrode or the amount of active material per unit area increases, the wetting time of the electrode increases.

In order to improve the wettability of the electrode, a method of injecting an electrolyte solution at a high temperature or injecting the electrolyte solution under a pressurized or reduced pressure state is used.

In the present invention, using the electrowetting method, it was found that by repeatedly applying alternating current or pulsed electrical perturbation to the electrochemical device, wetting between the electrode and the electrolyte can be improved very simply within a short time.

Accordingly, the present invention provides a method for manufacturing an electrochemical device which is treated to improve the wettability between an electrode and an electrolyte by applying an electrical perturbation in the form of alternating current or pulse, and separately so that the wettability of the electrochemical device manufactured by the above method is improved. It is an object to provide a pretreated electrode and a method for producing the electrode.

The present invention provides a method of manufacturing an electrochemical device including an anode, a cathode, and an electrolyte, the method comprising applying an electrical or perturbation in the form of alternating current or a pulse between the anode and the cathode in which the electrolyte is interposed therebetween Including a, it provides a method for producing an electrochemical device with improved wettability between the electrode and the electrolyte.

The present invention also provides an electrochemical device comprising an anode, a cathode, and an electrolyte, wherein a pretreatment for applying an alternating current or pulsed electrical perturbation to both ends of the anode and the cathode in which the electrolyte is interposed is performed. The present invention provides an electrochemical device characterized in that the wettability between the electrode and the electrolyte is improved.

The present invention also provides a method of manufacturing an electrode having improved wettability with an electrolyte, including applying an alternating current or pulsed electrical perturbation to an electrode in a treatment tank having an electrolyte, and an electrode manufactured by the method. do.

Hereinafter, the present invention will be described in detail.

The electrochemical device uses an electrochemical reaction between the electrodes. Since the ions generated at the anode are transferred to the cathode, the cathode, through the electrolyte, the ions generated at the electrode are transferred between the electrode and the electrolyte to be transferred to the electrolyte. Wetability is important. Conventional electrochemical devices have a separate wetting process in order to improve wetness between the electrodes and the electrolyte, and in particular, in the case of secondary batteries, the electrode-through the formation and aging process during the process. Wetting between electrolytes induces a well known process that requires a very long time. In order to shorten the wetting time, a method of heating or pressurizing the electrolyte is often used, but in this case, it takes about 1 to 2 weeks.

The present invention is characterized in that the wettability between the electrode and the electrolyte is improved by using an electrowetting method in order to perform the wetting of the electrochemical device in a simpler and shorter time.

Electrowetting (Electrowetting), as described above, by controlling the interfacial tension between the electrolyte and the insulator by applying electrical perturbation such as voltage or current from the outside while a thin insulator is inserted between the electrolyte (or conductive fluid) and the electrode The technique of changing the contact angle of the electrolyte and the interfacial phenomenon between the two fluids.The electrocapillary phenomenon, which is the basis of electrowetting, was proposed by Gabriel Lippmann in 1875. The height is lowered. However, when the electrocapillary phenomenon is used, the electrolyte is decomposed when the applied voltage exceeds a few hundred millivolts, and a solution of this is the current electrowetting method, also called EWOD (Electrowetting on dielectric). That is, by disposing the thin insulating film between the electrode and the electrolyte, it is possible to suppress the decomposition of the electrolyte, to prevent the flow of electricity to the fluid, and to suppress the reaction between the fluid and the electrode.

Referring to the principle of the electrowetting method illustrated in FIG. 1, when the electric field E is applied between the electrode and the electrolyte, the contact angle θ between the electrolyte and the electrode may be represented by Equation 1 below.

[Equation 1]

cos θ = cosθ ₀ + (c / 2γ) V ²

In this case, θ ₀ is a contact angle when V = 0, c is capacitance per unit area, and γ represents surface tension.

That is, according to Equation 1, the larger the applied voltage V, the larger the cos θ value, that is, the smaller the contact angle θ, which means that the wettability between the electrode and the electrolyte is improved and the wetting is better. do. Of course, experimentally, the contact angle does not become infinitely small due to the increase in voltage, and it seems to cause saturation at a constant contact angle.

The method of manufacturing the electrochemical device of the present invention is generally in addition to the manufacturing method of the electrochemical device known to those skilled in the art, the voltage and current in the form of an alternating current or a pulse between the anode and the cathode with an electrolyte interposed therebetween It may be to include applying the same electrical perturbation.

That is, the electrochemical device is generally configured to include an anode, a cathode, and an electrolyte, and after fabricating the respective components, assembled in an electrochemical device, in the completed state, electrical perturbation in the form of alternating current or pulse By applying to the electrochemical device, the wettability between the electrode and the electrolyte can be improved.

The advantages of applying AC perturbation compared to DC perturbation are as follows. In general, when a direct current perturbation is applied to an electrochemical device, a current flows in either direction between the anode and the cathode, and as a result, a phenomenon in which the electrochemical device is charged or discharged is inevitably accompanied. At this time, when the amount of charge due to perturbation of the DC is accumulated, the electrochemical device is exposed to the risk of overcharge or overdischarge. Such overcharge or overdischarge may cause deterioration of the electrochemical device as well as safety problems of explosion / ignition. On the other hand, when alternating perturbation is applied to the electrochemical device, the total amount of charge flowing between the anode and the cathode becomes zero, so there is no risk of overcharge or overdischarge.

The same may be true for pulsed electrical perturbation. That is, by adjusting the time that the pulse is applied and the time that is not applied, it is possible to provide a time for the electrochemical device can be relaxed after being affected by the pulse perturbation. In addition, by sequentially applying pulses of opposite polarity to each other may exhibit an effect similar to the AC perturbation as a whole.

Therefore, in the present invention, by applying the electrical perturbation in the form of alternating current or pulse to the electrochemical device, while improving the wetting between the electrode and the electrolyte, and overcharge, over-discharge, etc., which may adversely affect the performance of the electrochemical device during the wetting process The device can be protected from problems.

The electrochemical device of the present invention is not particularly limited as long as the device includes an anode, a cathode, and an electrolyte and causes an electrochemical reaction. Preferably, the electrochemical device may be a battery, a capacitor, a fuel cell, or an electrochromic device. have.

In the manufacturing method of the present invention, the electrical perturbation applied to the electrochemical device to improve the wettability between the electrode and the electrolyte may be in the form of alternating current or pulse.

When the electrical perturbation applied to the electrochemical device is in the form of an alternating current, the applied alternating current may have a frequency in the range of 1 Hz to 1 MHz. In general, when the ionic conductivity of the electrolyte is low, the use of a low frequency is advantageous for the electrode and the wetting of the electrolyte, and the higher the ion conductivity of the electrolyte is known to weaken the correlation between the frequency and the wettability, in the case of the present invention Depending on the type of electrolyte used, the frequency of the alternating current electrical perturbation can be varied.

In addition, the amplitude of the alternating current applied may be in the range of 1 mA to 100 A or in the range of 10 mV to 1000 V. As described above, when the applied voltage is increased, the wettability between the electrode and the electrolyte is improved, but will not increase indefinitely, and thus, the preferred voltage and current range in the present invention may be in the above range.

When the electrical perturbation applied to the electrochemical device is in the form of a pulse, the applied pulse current may have a waveform of a semi-square wave, sawtooth wave, triangle wave, rectangular wave, or Gaussian wave, and the waveform may be alone or 2 More than one waveform may be mixed with each other.

In addition, the applied pulse current may have a frequency in the range of 1 Hz to 1 MHz.

In addition, the amplitude of the applied pulse current may be in the range of 1 mA to 100 A or in the range of 10 mV to 1000 V.

In addition, the applied pulse current is 1 μsec. It may have a pulse duration (duration time) in the range of ~ 1 hr.

In the manufacturing method of the present invention, the amount of charge transferred to the electrochemical device by the application of the above-described electrical perturbation may be in the range of 0.1% to 15% of the maximum capacity of the electrochemical device. In the case of a lithium secondary battery, the amount of charge applied to the battery by a general formation process is generally 15% or more of the battery capacity, and when the amount of the charge is higher than that, the irreversible capacity of the electrochemical device is greatly increased. . The manufacturing method of the present invention applies less than 15% of the electrochemical perturbation of the electrochemical device capacity, which is smaller than that of the general formation process, so that the wettability between the electrode and the electrolyte in a shorter time can be avoided without causing such a problem. Can be improved.

When the alternating current or the pulse voltage is applied by the electrowetting method, the temperature of the electrochemical device may be maintained at 30 ° C to 80 ° C. Since the interfacial energy for controlling wettability tends to decrease with increasing temperature, the electrowetting method of the present invention may be performed at room temperature, but preferably 30 ° C. to 80 ° C., more preferably 40 ° C. to 60 ° C. It can also carry out by heating up, and at this time, the wet processing time can be further shortened.

The electrochemical device manufacturing method of the present invention uses an electrowetting method, and the electrowetting method may be configured to place an insulating film between the electrode and the electrolyte. In the method of the present invention, it is not necessarily required to include an insulating film between the electrode and the electrolyte as described above, but preferably may further include a separate separator or insulator film between the anode and the cathode. When the separator includes a separator between the anode and the cathode, such as a secondary battery, the separator may serve as an insulating film. However, in the configuration of the electrochemical device that does not include a separator, it may also correspond to the configuration of the present invention to further include a separate insulator film between the anode and the cathode, even if the electrochemical device including a separator It may further comprise an insulator film.

As the separator of the secondary battery, a separator well known in the art may be used, and non-limiting examples thereof include a polypropylene-based, polyethylene-based, and polyolefin-based porous separator.

The insulator film which may be separately included is not particularly limited as long as it is an insulator film having low electrical conductivity. Examples of the insulator film may include inorganic insulators such as Al ₂ O ₃ , BaTiO ₃ , SiO ₂ , and SiN, parylene-N, and parylene-. Polymeric insulators such as C, Teflon film, polydimethylsilozane (PDMS), etc. may be used.

On the other hand, the present invention includes the configuration of the electrowetting treatment in addition to the electrode alone, in addition to the electrowetting treatment after completing the electrochemical device by assembling the anode, the cathode, the electrolyte. For example, before the electrode and the electrolyte are combined to form an electrochemical device, the wettability with the electrolyte is applied by applying an electrical perturbation in the form of alternating current or pulse in a treatment tank having the same electrolyte as the electrolyte used for the electrochemical device. The electrode can be pretreated to improve it.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. However, the present invention is not limited thereto.

Example 1

LiCoO ₂ is used as positive electrode active material and artificial graphite is used as negative electrode active material to make slurry by weight ratio of active material, conductive carbon and binder PVDF as 88: 6: 6 and coated on metal foil with thickness of 15 ㎛ to make positive electrode and negative electrode. Using a solution of LiPF ₆ 1M in EC: EMC (weight ratio 1: 2) as an electrolyte, prepare a pouch-shaped battery.

AC power is connected to both terminals of the battery, and electrowetting is performed at 60 Hz and 0.4 V for 1 hour.

 Comparative Example 1

A battery produced in the same manner as in Example 1 was connected to a 0.7 V DC power supply and subjected to a formation process for 24 hours.

The wettability improvement effect between the electrode and the electrolytic solution by the electrowetting process of the present invention can be confirmed indirectly by comparing the battery characteristics of the battery produced in Example 1 and Comparative Example 1.

According to the present invention, a small amount of charge can be added in a simpler manner than a conventional wet method by applying an electrical or perturbation of alternating current or pulse to the anode and the cathode of the electrochemical device using the electrowetting method. Even if the wettability between the electrode and the electrolyte can be improved. Therefore, the performance of the electrochemical device can be improved, and the time required for the wetting of the electrolyte can be shortened to shorten the manufacturing process time of the electrochemical device.

Claims (14)

A method of manufacturing an electrochemical device comprising an anode, a cathode, and an electrolyte, the method comprising applying an electrical perturbation in the form of alternating current or pulse to both ends of the anode and the cathode interposed therebetween Including a step, a method of manufacturing an electrochemical device with improved wettability between the electrode and the electrolyte. The method of claim 1, wherein the electrochemical device is one selected from the group consisting of a battery, a capacitor, a fuel cell, and an electrochromic device. The method according to claim 1, wherein the electrical perturbation in the form of alternating current applied has a frequency in the range of 1 Hz to 1 MHz. The method according to claim 1, wherein the amplitude of the electrical perturbation in the form of alternating current applied is in the range of 1 mA to 100 A or in the range of 10 mV to 1000 V. The method according to claim 1, wherein the pulsed electrical perturbation has at least one waveform selected from the group consisting of semi-square waves, sawtooth waves, triangle waves, rectangular waves, and Gaussian waves. The method of claim 1, wherein the electrical perturbation in the form of pulses applied has a frequency in the range of 1 Hz to 1 MHz. 2. A method according to claim 1, wherein the amplitude of the electrical perturbation in the form of pulses applied is in the range of 1 mA to 100 A or in the range of 10 mV to 1000 V. The method of claim 1, wherein the electrical perturbation in the form of pulses applied is 1 μsec. To 1 hr. A manufacturing method characterized by having a pulse duration of a range. The method of claim 1, wherein the amount of charge transferred to the electrochemical device by applying the voltage is in the range of 0.1% to 15% of the maximum capacity of the electrochemical device. The method according to claim 1, wherein the temperature of the electrochemical device is maintained at 30 ° C. to 80 ° C. when the alternating current or pulse type electrical perturbation is applied. The method of claim 1, further comprising a separate separator or insulator film between the anode and the cathode. In an electrochemical device comprising an anode, a cathode, and an electrolyte, pretreatment is performed by applying an electric or electric perturbation in the form of alternating current or pulse to both ends of the anode and the cathode interposed between the electrolyte and the electrode. Electrochemical device characterized in that the wettability between the electrolyte and the electrolyte is improved. A method of manufacturing an electrode having improved wettability with an electrolyte, comprising applying electrical perturbation in the form of alternating current or pulse to the electrode in a treatment tank having an electrolyte. The electrode is characterized in that the pre-treatment to improve the wettability with the electrolyte by applying electric perturbation in the form of alternating current or pulse to the electrode in the treatment tank having the electrolyte.

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