KR200266593Y1 - Electric Energy Storage System - Google Patents

Abstract

An electric energy storage device capable of increasing the stability of a polymer separator or a polymer insulating material by controlling the arrangement of an anode and a cathode is disclosed. An electric energy storage device of the present invention includes an electrode including an anode and a cathode, a separator positioned between the anode and the cathode to electrically insulate them, an electrolyte for impregnating the electrode and the membrane to enable conduction of ions, and An electrical energy storage device comprising a housing for preserving the component in a sealed state, wherein the outermost electrode adjacent to the housing is an anode. By allowing the anode to come to the outermost portion instead of the cathode, it is possible to prevent the formation of side reactions by charging and discharging and to increase the stability of the polymer, thereby preventing the deterioration of reliability of the electric energy storage device.

Description

Electric Energy Storage System

The present invention relates to an electrical energy storage device, and more particularly, to an electrical energy storage device that can increase the stability of a separator or a polymer material by controlling the arrangement of an anode and a cathode.

In general, an electric energy storage device using a liquid such as an electric double layer capacitor, an electrolytic capacitor, or a battery is largely composed of an anode and a cathode including an active material that stores electrical energy and a current collector that serves as a movement path of charges emitted or supplied from the active material. It is located between the anode and the cathode and electrically insulates the anode and the cathode, and is impregnated with a separator made of porous paper or porous polymer, which is impregnated with the electrode and the membrane, and supplies ions to the electrode and enables conduction of ions. It consists of an electrolyte, a housing for keeping each component in a sealed state, and a terminal for connecting the electrical energy storage device to the outside.

A general electrical energy storage device is manufactured by winding or stacking electrodes and separators in a cylindrical shape to form an electrode body in a plate shape, injecting an electrolyte solution into the electrode body, placing it in a housing, and sealing it, or placing the electrode body in a housing, By injection and sealing. A method of manufacturing such a wound and plate-shaped electrode body will be described in more detail with reference to the accompanying drawings.

1A and 1B are schematic diagrams for explaining a method of manufacturing a conventional cylindrical electrical energy storage device by a winding method, respectively, and a state in which the components are stacked before winding up to manufacture the cylindrical electrical energy storage device of FIG. 1A. Schematic diagram.

Referring to Figure 1a, the device is obtained in a cylindrical shape by winding each part, the unfolded end portion has a polymer separation membrane 10 on the outermost side, the cathode 20 is disposed as a first electrode therein, The polymer separator 10 is again positioned inside the cathode 20, and the anode 30 is disposed as a second electrode therein. Therefore, both the anode 30 and the cathode 20 are separated by the polymer separator 10 and the cathode 20 is located at the outermost side. Reference numerals 15a and 15b denote terminals of the positive electrode, and 16a and 16b denote terminals of the negative electrode.

In order to obtain a cylindrical device having such a structure, as shown in FIG. 1B, each part must be stacked and wound. At the uppermost end, the anode 30 is positioned in the shape of a rectangular elongated plate, and the polymer separator 10, the cathode 20, and the polymer separator 10 are positioned at the bottom thereof. After stacking the parts in this order, the uppermost positive electrode is wound up so that the winding type device as shown in Fig. 1A is obtained. As a result, a cathode is provided in the outermost part as an electrode.

2A and 2B are schematic perspective views of a conventional electric energy storage device manufactured in a plate shape, respectively, and a cross-sectional view of each component in the electric energy storage device of FIG. 2A.

Referring to FIG. 2A, each part is laminated in the order of the polymer separator 10, the positive electrode 30, the polymer separator 10, and the negative electrode 20, and the polymer insulator 40 surrounds the laminate at the outermost side. Each electrode has a structure in which the terminals 15a and 15b of the positive electrode and the terminals 16a and 16b of the negative electrode are formed to protrude in a predetermined direction to form a bundle.

In order to manufacture the stacked type device having such a structure, each component is laminated in the order shown in FIG. 2B. That is, the polymer insulator 40, the polymer separator 10, the positive electrode 30, the polymer separator 10, the negative electrode 20 from the top end ... the polymer separator 10, the positive electrode 20, the polymer separator 10 , The cathode 20, the polymer separator 10, and the polymer insulator 40 are laminated in order.

As a result, in the electrode body active material manufactured in a plate shape, one side of the outermost side has a positive electrode and the other side of the outermost side has a negative electrode. Packed with.

As shown in the drawings, in the manufacture of a general electrical energy storage device, a cathode is positioned outward as an electrode, which is selected due to a capacitance difference between an anode and a cathode in an electric double layer capacitor. Anion is mainly collected at the reactor-shaped anode of the electric double layer capacitor to form an electric double layer, and cations are mainly collected at the cathode to form an electric double layer to store energy. In addition, ammonium-based organic ions are mainly used as cations instead of metal ions, and ions containing fluorine are used as anions. However, since the size of the cation is usually about 50% larger than the size of the anion, when looking at the actual energy capacity, the capacity of the negative electrode where the cations are mainly collected becomes smaller than that of the positive electrode where the negative ions are mainly collected. For this reason, according to the literature, it is known that when the amount of the active material of the negative electrode is added about 10%, the storage capacity is further increased.

On the other hand, the electric double layer capacitor using the organic electrolyte until now has been mainly used at 2.3V, the research to increase the voltage used in recent years continues to proceed. However, if the electrode body active material used without problem at 2.3 V is applied with a potential higher than that, the porous polymer separator is broken or melted away at the cathode rather than the cathode, and dissolves the electrical insulating material on the polymer. There is a phenomenon that causes. In particular, this phenomenon occurs as a large hole in the porous polymer membrane or the polymer electrical insulating material directly contacting the electrode active material.

In addition, this phenomenon is more severe when using a nitrile electrolyte such as acetonitrile than when using a carbonate electrolyte such as propylene carbonate. In addition, no decomposition or physical property change of the polymer is observed in the porous polymer membrane inserted therebetween so that the negative electrode and the positive electrode contact each other in the electrode active material, but are disposed at the end of the electrode active material, When the electrode of either polarity is arranged only on one side, denaturation of the polymer is observed.

In addition, the phenomenon of the polymer is characteristically observed when the potential is further applied at the cathode than at the anode. The reason why the decomposition of the polymer material on the cathode side becomes a problem is that it is easier to widen the voltage range of the cathode than to increase the voltage range of the anode due to the electrochemical characteristics between the electrolyte and the active material when attempting to increase the voltage used in the electric double layer capacitor. It is believed that the polymer material is selectively decomposed at the negative electrode, and the negative electrode active material is directly in contact with the metal case made of aluminum, and the potential region of the negative electrode is similar to the reduction potential of aluminum in the presence of water, which is very likely to corrode the case. It will grow big.

An object of the present invention is to provide an electrical energy storage device that can increase the stability of the separator or the polymer material by adjusting the arrangement of the positive electrode and the negative electrode in order to solve the above problems of the prior art.

1A and 1B are schematic diagrams (FIG. 1A) for explaining a method of manufacturing a conventional cylindrical electrical energy storage device by a winding method, respectively, and overlapping each component before winding to manufacture the cylindrical electrical energy storage device of FIG. 1A. It is a schematic diagram (FIG. 1B) which shows a state of laying.

2A and 2B are schematic perspective views (FIG. 2A) of a conventional electric energy storage device manufactured in a plate shape, respectively, and a cross-sectional view (FIG. 2B) for explaining the stacked state of each component in the electric energy storage device of FIG. 2A. .

3 is a graph of the change of the rayon polymer used as the separator for the electric double layer capacitor by FT-IR using the ATR method, a is a graph obtained by measuring before the polymer is changed, b is after the polymer is denatured It is a graph obtained by measuring.

4A and 4B are schematic diagrams (FIG. 4A) for explaining a method of manufacturing a cylindrical electrical energy storage device according to the present invention by winding method, respectively, and each component before winding to manufacture the cylindrical electrical energy storage device of FIG. 4A. It is a schematic diagram (FIG. 4B) which shows the state which overlapped.

Figures 5a and 5b are each made in a plate shape and a schematic perspective view of the electrical energy storage device according to the present invention (Fig. 5a) and a cross-sectional view showing the stacked state of each component in the electrical energy storage device of Figure 5a (Fig. 5b )to be.

<Explanation of symbols for the main parts of the drawings>

10, 110: polymer membrane

20, 120: cathode

30, 130: anode

40, 140: polymer insulator

In order to achieve the above object, in the present invention

An electrode including a positive electrode and a negative electrode, a separator positioned between the positive electrode and the negative electrode to electrically insulate them, and an electrolyte solution and the component to be impregnated in the electrode and the separator to enable conduction of ions in a sealed state. An electrical energy storage device comprising a housing for preservation, wherein the outermost electrode adjacent to the housing is an anode.

In particular, it is preferable that the electrical energy storage device is a wound storage device formed by winding an anode, a separator, and a cathode, or a plate-shaped storage device formed by stacking a cathode, a separator, and a cathode. In addition, the energy storage device is preferably an electric double layer capacitor or a secondary battery.

The present invention is preferably applied when the electrolyte solution contains an organic electrolyte, in particular, a nitrile-based electrolyte, and also when the separator is made of rayon.

As a result, when looking at the configuration of the present invention, the electrode disposed in the outermost part in order to suppress the side reactions caused by the by-products generated in the negative electrode in the case of lamination or winding in the conventional electrical energy storage device must be positive You can see that it is a structure that has a form.

In particular, an electrical energy storage device using a liquid, such as an electric double layer capacitor or a secondary battery, is disposed between a positive electrode and a negative electrode composed of an active material and a current collector, and a separator made of a porous polymer or the like or laminated together with a plate or It is prepared by winding in a cylindrical form. In the case of the winding type, as in the case of the lamination type or the plate type, it is wrapped with an insulating polymer for electrical insulation, and then sealed in the housing with a little free space, and the electrode body active material is in contact with the housing. The outer-positive side increases the chemical stability of the porous polymer membrane or the electrically insulating material that is the polymer. By increasing the stability of the polymer as described above, the form of the polymer material is maintained as it is, to prevent direct contact between the electrode and the aluminum case, and to prevent the decomposition products of the polymer from melting into the electrolyte.

Hereinafter, the working principle of the present invention will be described in detail.

In the case of polymers that are corroded at the cathode, polymers such as rayon used as a separator and polyethylenetetraphthalate used as a polymer electrical insulator are decomposed, whereas polypropylene is not used as a separator. This is believed to imply the decomposition reaction mechanism of the polymer.

The decomposition of polymers is usually divided into radical reacitons and nucleophiles such as anions, which are more radical reactions in that polypropylene is not decomposed, but rayon or polyethylene tetraphthalate is decomposed. Rather, it is expected to be due to reaction with nucleophiles such as anions.

However, the decomposition reaction of such a polymer occurs only in contact with an active material such as carbon, and does not occur when in contact with a metal such as aluminum. Therefore, it is believed that the cause of the decomposition reaction of the polymer is caused by side reactions present in the active material. In particular, when referring to the decomposition of the electrolyte and the possibility of generation of impurities, the first consideration is the decomposition of water. In general, the decomposition of water that can be expected from the cathode is shown in the following equation (1).

^{_{H 2 O + e - → ½H}} 2 + OH - (2.0V vs. Li / Li +) --- (1)

The active material used as the negative electrode is 2.0V vs. When moving to the potential of Li / Li ⁺ less water be reduced atom OH ^- ions and make, OH ^- ions is a potent nucleoside file likely to be functional. This nucleophile is particularly characteristic only at the end of the electrode body or at the end of the wound part, so that these parts do not touch the counter electrode on the positive side, and the potential is 2.0V vs. It is lowered to Li / Li ⁺ or less, but since the potential of the polymer separator is not applied and ions do not accumulate, it is much easier to diffuse from the electrode surface to the polymer part. Nucleophiles generated by impurities on the electrode surface can be expected to react with the -COO- moiety of the polymer selectively, thereby damaging the polymer's bonding structure and melting.

3 is a graph of the change of the rayon-based polymer used as the separator for the electric double layer capacitor by FT-IR using the ATR method, a is a graph measured before the polymer is changed, b is measured after the polymer is modified One graph.

Graph b is a result of measuring the denatured polymer because the separator was actually used in the electric double layer capacitor and then contacted the active material and the aluminum case together, and was almost changed until it was almost broken. The major difference observed is that the peak at 1730 cm ⁻¹ and the broad peak at about 3400 cm ⁻¹ , which were not present in graph a, are observed in graph b. This peak indicates the presence of -COOH. The breakdown of the structure in the polymer results in the formation of -COOH, suggesting that it is by reaction with a nucleophile such as -OH described above.

This reaction occurs mainly at the innermost part of the electrode body active material, but rather at the outermost side where the negative electrode is exposed. Even if materials capable of decomposing the polymer separator are generated, they are not accumulated in the polymer separator when they are generated inside the electrode body active material, whereas in the outermost part of the electrode body active material, they are likely to accumulate in the polymer separator. This is because it is not easy to move the ionic material formed in the pores of the electrode because no potential is applied to the polymer membrane inside, whereas from the outside, an electric field is formed between the electrode and the aluminum case because the electrode body active material contacts the aluminum case. This is because the formation of ions moves along the electric field, making ion accumulation in the polymer membrane much easier.

Generally, polyethylene or polypropylene, which is a polymer that does not react with nucleophile and has excellent chemical stability, is difficult to use because of poor thermal stability and high cost when used as a porous material. Because of its high reactivity, there is a need to improve it.

Since the electrons are mainly transferred from the cathode, the impurities react with the electrons, and then a reduction reaction occurs to form anions. On the cathode, the electrons are mainly released, so that the impurities are easily oxidized to generate gas. This is because impurities on the carbon surface often contain nonmetallic elements such as oxygen such as water and functional groups. For this reason, polymer degradation on the cathode side is considered much easier than on the anode side. In addition, when the polymer is decomposed, ions such as OH ⁻ come into direct contact with aluminum, and a very low potential is applied. In this case, the corrosion potential of aluminum increases.

Therefore, it is necessary to prevent the cathode surface from coming out in order to solve the problems such as impurity increase, reliability decrease, and case corrosion caused by the impurities generated in the cathode contacting the insulating polymer or the aluminum case.

Hereinafter, the present invention will be described in detail through specific examples.

<Example 1>

The manufacture of an energy storage device manufactured in a wound form will be described with reference to FIGS. 4A and 4B. In the winding type, when the cathode is wound to the outermost side instead of the cathode, damage to the polymer separator of the outermost surface can be prevented. In order to manufacture in such a form, it must be manufactured in a state where each element is arranged as shown in FIG. 4B.

4A and 4B are schematic views for explaining a method of manufacturing a cylindrical electrical energy storage device according to the present invention by a winding method, respectively, and a state in which each component is overlapped before winding up to manufacture the cylindrical electrical energy storage device of FIG. 4A. It is a schematic diagram showing.

Looking at Figure 4a, the device is obtained in a cylindrical shape by winding each part, the unfolded end portion has a polymer separation membrane 110 in the outermost, the anode 130 is disposed as a first electrode therein, The polymer separator 110 is again positioned inside the anode 130, and the cathode 120 is disposed as a second electrode therein. Therefore, both of the anode 130 and the cathode 120 are separated by the polymer separator 110, and the anode 130 is positioned at the outermost side. Reference numerals 115a and 115b denote terminals of the positive electrode and 116a, and 116b denote terminals of the negative electrode.

In order to obtain a cylindrical device having such a structure, each part must be stacked and wound as shown in FIG. 4B. At the top end, the cathode 120 is positioned in the shape of a rectangular elongated plate, and the polymer separator 110, the anode 130, and the polymer separator 110 are positioned under the cathode 120. After stacking the parts in this order, the uppermost cathode is wound up so that the winding type device as shown in Fig. 4A is obtained. As a result, an anode is provided in the outermost part as an electrode.

<Example 2>

An example of an electrical energy storage device manufactured in the form of a plate will be described with reference to FIGS. 5A and 5B. In the case of stacking the positive electrode and the negative electrode for the manufacture of the plate type, the positive electrode should be arranged at both sides of the outermost part which is in contact with the case.

5A and 5B, respectively, are formed in a plate shape and have a schematic perspective view of an electric energy storage device according to the present invention, and a cross-sectional view illustrating the stacked state of each component in the electric energy storage device of FIG. 5A.

Referring to FIG. 5A, each part is stacked in the order of the polymer separator 110, the negative electrode 120, the polymer separator 110, and the positive electrode 130, and the polymer insulator 140 surrounds the laminate at the outermost side. From each electrode, the terminals 115a, 115b and 115c of the positive electrode and the terminals 116a, 116b and 116c of the negative electrode are formed to protrude in a predetermined direction to form a bundle.

In order to manufacture the stacked type device having such a structure, each component is laminated in the order shown in FIG. 5B. That is, the polymer insulator 140, the polymer separator 110, the positive electrode 130, the polymer separator 110, the negative electrode 120 from the top end ... the polymer separator 110, the negative electrode 130, the polymer separator 110 The anode 130, the polymer separator 110, and the polymer insulator 140 are laminated in the order of manufacture. As a result, the anode is disposed on both outermost sides.

The electric energy storage device of the present invention as described above may be more easily applied to an energy storage device using an organic electrolyte such as an electric double layer capacitor or a secondary battery.

According to the present invention, it is possible to prevent the deterioration of the stability of the energy storage device by preventing the reaction of the secondary reactants due to charging and discharging, and also preventing the reaction of the secondary reactant and the polymer by allowing the anode to come to the outermost portion instead of the negative electrode.

Although described above with reference to a preferred embodiment of the present invention, those skilled in the art will be able to variously modify and change the present invention without departing from the spirit and scope of the present invention described in the claims below. It will be appreciated.

Claims (8)

An electrode including a positive electrode and a negative electrode, a separator positioned between the positive electrode and the negative electrode to electrically insulate them, and an electrolyte solution and the component to be impregnated in the electrode and the separator to enable conduction of ions in a sealed state. An electrical energy storage device comprising a housing for preservation, wherein the outermost electrode adjacent to the housing is an anode. The electric energy storage device according to claim 1, wherein the electric energy storage device is a winding-type electric energy storage device formed by winding an anode, a separator, and a cathode, the anode being an outermost wound electrode. The electrical energy storage device according to claim 1, wherein the electrical energy storage device is a plate-shaped electrical energy storage device in which an anode, a separator, and a cathode are stacked, and the electrodes located at the top and the bottom thereof are both anodes. The electric energy storage device according to claim 1, wherein the energy storage device is an electric double layer capacitor or a secondary battery. The electrical energy storage device according to claim 1, wherein the electrolyte solution comprises an organic electrolyte. The electrical energy storage device according to claim 5, wherein the organic electrolyte is a nitrile electrolyte. The electrical energy storage device according to claim 1, wherein the separator is made of rayon. The electrical energy storage device according to claim 3, wherein the separator and the polymer insulator made of polyethylenetetraphthalate are further disposed on the outer and outermost electrodes.