KR20080064474A - Electrolyte for improving life characteristics of olivine type battery at a high temperature and secondary battery comprising the same - Google Patents

Abstract

A secondary battery using an electrode active material having an olivine type crystal structure is provided to prevent degradation of the electrode active material caused by an acid including HF, thereby realizing improved lifespan and high-temperature storage characteristics. A secondary battery comprises: (a) a cathode; (b) an anode; (c) a separator; and (d) an electrolyte containing an electrolyte salt and an organic solvent, wherein either or both of the cathode and the anode comprise an electrode active material having an olivine type crystal structure, and the electrolyte further comprises (e) a compound that chemically reacts with an acid(H+) to produce a chemical reaction product other than water.

Description

ELECTROLYTE FOR IMPROVING LIFE CHARACTERISTICS OF OLIVINE TYPE BATTERY AT A HIGH TEMPERATURE AND SECONDARY BATTERY COMPRISING THE SAME}

The present invention uses an electrolyte solution containing an electrolyte additive capable of reducing the concentration of strong acid (HX) that is present in a battery and causes a decrease in performance, thereby preventing elution of the olivine-based electrode active material by the HX and the battery. The present invention relates to a secondary battery having improved overall performance such as long life characteristics and high temperature storage characteristics.

Recently, as miniaturization and light weight of electronic equipment have been realized and the use of portable electronic devices has become common, research on lithium secondary batteries having high energy density has been actively conducted. A lithium secondary battery is prepared by using a material capable of inserting and detaching lithium ions as a negative electrode and a positive electrode, and filling an organic or polymer electrolyte between the positive electrode and the negative electrode, and lithium ions can be inserted and removed from the positive electrode and the negative electrode. Electrical energy is generated by oxidation and reduction reactions.

LiCoO ₂ has been reported to be useful as a cathode active material of a lithium secondary battery in 1980, and many studies have been conducted to date, and have been mainly employed as a cathode active material of commercialized lithium secondary batteries. However, since cobalt (Co) is one of the scarce resources on earth, development of a new cathode active material is in progress. In particular, LiFePO ₄ has a large volume density of 3.6 g / cm ² , generates a high potential of 3.4 V, and a theoretical capacity of 170 mAh / g. Fe is abundant in resources and can be manufactured at a low price. LiFePO ₄ contains one Li per electrochemically desorbable Li element at an initial state, thus replacing LiCoO ₂ . It is expected to be an active material. In addition, LiMPO ₄ substituted with a transition metal instead of Fe of LiFePO ₄ is also known. Interestingly, the potential of Li can be changed in various ways depending on the type of M.

With the general formula Li _x MPO ₄ (M = Fe, Mn, Co, Ni, Cu, Zn, Mg, Cr, V, Mo, Ti, Al, Nb, B, Ga, 0.05 ≦ x ≦ 1.2) The compound to be displayed has an olivine-type crystal structure and has excellent cycle characteristics because the change in crystal structure accompanying charge and discharge is small. In addition, since oxygen atoms in the crystal are stably present by covalent bonds with phosphorus, there is an advantage that the possibility of oxygen emission is small and the safety is excellent even when the battery is exposed to a high temperature environment.

On the other hand, in the lithium secondary battery, the long life characteristics and high temperature storage characteristics of the battery is an essential element that the battery should have. In the battery using the above-described conventional cathode active material, HF, which is a strong acid, is formed by reacting with moisture present in an electrode or an electrolyte and lithium salt, for example, LiPF ₆ , which is accompanied by undesirable side reactions. That is, the generated HF not only dissolves and degenerate the positive electrode material, but also forms lithium fluoride (LiF) on the surface of the anode, resulting in an increase in electrical resistance and generation of gas, thereby degrading the life of the battery. It is occurring. In particular, when the battery is constructed using the olivine-based electrode active material (eg, Li _x MPO ₄ ) having the olivine-type crystal structure described above, there is a risk that the transition metal (M) is eluted into the electrolyte by HF. If the transition metal reacts with the electrolyte to generate gas, the safety of the battery may be threatened. The eluted transition metal precipitates on the opposite negative electrode as a metal phase, preventing the insertion and desorption of lithium ions, thereby lowering the voltage. The problem of shortening the lifespan may occur. Note that at this time, the dissolution rate of the electrode by the HF is raised at high temperatures, HF has a great problem in battery cycle life and storage at high temperatures.

In order to solve the above-mentioned problems caused when the battery is constructed by using an electrode active material having an olivine-type crystal structure, the present inventors have described the chemicals of HX (X = F, Cl, Br, I) and chemicals that cause a decrease in battery performance. By using an electrolyte additive that reacts to generate organic matter except water, the battery is prevented from deterioration of the olivine-based electrode active material by HX (X = F, Cl, Br, I), such as HF, and shortening of the battery life. It has been found to increase the lifespan characteristics and high temperature storage characteristics of.

Accordingly, an object of the present invention is to provide a battery electrolyte containing the electrolyte additive and a lithium secondary battery containing the electrolyte.

The present invention (a) a positive electrode; (b) a cathode; (c) separators; And (d) an electrolyte containing an electrolyte salt and an organic solvent, wherein the positive electrode, the negative electrode, or the positive electrode is an electrode including an electrode active material having an olivine crystal structure, Electrolyte solution provides a secondary battery characterized in that it comprises a compound (e) to produce a chemical reaction product excluding water through a chemical reaction with acid (H ⁺ ).

In addition, the present invention (a) an electrode active material having an olivine-type crystal structure; And (b) a compound for producing a chemical reaction product except water through a chemical reaction with an acid (H ⁺ ).

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in detail.

The present invention provides a battery having an olivine-based electrode active material, HX (X = F, which causes dissolution of the transition metal present in the olivine type crystal structure, resulting in a decrease in the life of the battery, etc.). A compound capable of reducing the concentration of Cl, Br, I) is used as an electrolyte additive or an electrode additive.

HX (X = F, Cl, Br, I) is a strong acid produced by the reaction of lithium-containing halogen salts such as lithium-containing fluoride salts and lithium-containing chloride salts used as electrolyte salts with a small amount of water present in the battery. As an example, it is essentially accompanied by undesirable side reactions as described above when present in the battery. In particular, in the case of constructing a battery using an electrode active material having an olivine crystal structure, the overall lattice energy rise and lattice structure deformation of the electrode are caused by HX, and a phase change accompanies the dissolution of transition metal from the electrode active material. (dissolution) is serious.

Thus, in the present invention, by using a compound that performs a spontaneous chemical reaction with HX (X = F, Cl) present in the battery as a component of the electrolyte or electrode, HX (X = F, Cl in addition to reducing the HX concentration in the battery , Br, I) can fundamentally solve the problem of performance degradation of the battery described above.

In other words, it prevents the leaching of transition metals from the olivine-based electrode active material to directly prevent the reduction of the capacity of the anode material, and the eluted transition metal ions form a thick film on the surface of the cathode to act as a resistance. It is prevented at the source. Therefore, by increasing the internal resistance of the electrode and preventing the generation of gas, it is possible to improve the overall performance of the battery, such as the electromotive force, life characteristics of the battery.

In addition, in the present invention, organic matter except water is generated as a reaction product generated by the chemical reaction between the above-described electrolyte additive and HX, so that even if a small amount of water is present, the electrolyte salt (for example, lithium-containing fluorine salt, etc.) and water and In addition to fundamentally preventing the HF generation reaction itself is inevitably generated by the reaction of, there is an advantage that can continuously maintain the HF reduction effect (인해).

One of the elements constituting the secondary battery electrolyte according to the present invention may be used without particular limitation as long as it is a compound that produces a chemical reaction product except water through a chemical reaction with acid (H ⁺ ). In this case, the acid (H ⁺ ) is HX (X = F, Cl, Br, I) that is formed by the reaction of (i) at least one electrolyte salt composed of a lithium-containing halogen salt with (ii) water present in the battery. May be, but is not limited thereto.

The compound is an ionic salt compound capable of dissociating in an aqueous or non-aqueous solvent, and includes other conventional anions except for hydroxyl group (OH ⁻ ) which reacts with acid (H ⁺ ) to produce water. It is desirable to. The anion is not particularly limited, and non-limiting examples thereof include benzoate, phthalate, malate, succinate, citrate or mixtures thereof. Etc.

Chemical reactions that the compound and HX (X = F, Cl, Br, I) spontaneously perform are not particularly limited and include conventional chemical reactions known in the art. In addition, the product of the chemical reaction is not particularly limited as long as it is a compound other than water, for example, it may be benzoic acid, phthalic acid, maleic acid, succinic acid, citric acid and the like. In addition to the compounds described above, carboxylic acid (RCOOH), sulfonic acid (RCO ₃ H), sulfinic acid (RSO ₂ H ₄ ), phenolic acid (ArOH), enol (RCH = C (OH) R ₁ ), thiophenol (ArSH) ), Imide (RCONHCOR), oxime (RCH = NOH), aromatic sulfonamide (ArSO ₂ NH ₂ , ARSO ₂ NHR ₁ ), primary and secondary nitro compounds (RCH ₂ NO ₂ , RCHNO ₂ ) It belongs to the scope of the invention.

The electrolyte solution containing the electrolyte additive described above excludes water through a chemical reaction between (i) HX (X = F, Cl, Br, I) present in the battery and (ii) acid (H ⁺ ) contained in the electrolyte. It is possible to reduce the concentration of HX (X = F, Cl, Br, I) through a chemical reaction with anion among the compounds that produce the chemical reaction product.

As such, the amount of HX remaining in the electrolyte solution of the present invention for which the concentration of HX (X = F, Cl, Br, I) is reduced is preferably 50 ppm or less, but is not limited thereto. In addition, the acidity (pH) of the initial electrolyte solution in which HX is present is about 4.x (0 <x <9), while the acidity (pH) of the electrolyte solution is increased to 5 or more after the reduction of HX concentration is achieved. At this time, since a product such as benzoic acid releases H ⁺ ions only at pH 7.0 or higher, the effect of pH change by the product may be insignificant.

The content of the compound (c) can be adjusted according to the goal of improving the overall performance of the battery, but preferably 0.01 to 10 parts by weight per 100 parts by weight of the electrolyte. When less than 0.01 part by weight, the desired long-life characteristics and high temperature storage characteristics are insignificant, and when it exceeds 10 parts by weight, the capacity of the battery is reduced due to the side reaction of the surplus compound, the viscosity of the electrolyte is increased, and the ion conductivity is reduced. Performance degradation will occur.

Battery electrolytes to which the compound is to be added together include conventional electrolyte components known in the art, such as electrolyte salts and organic solvents.

Using the electrolyte salts is A ⁺ B ^- A salt of the structure, such as, A ⁺ is Li ^+, Na ^+, K ⁺ comprises an alkaline metal cation or an ion composed of a combination thereof, such as, and B ^- is PF ₆ ^-, BF _{^{4 -, Cl -, Br -}} , I -, ClO 4 -, AsF 6 -, CH 3 CO 2 -, CF 3 SO 3 -, N (CF 3 SO 2) 2 -, C (CF 2 SO 2) 3 ^- is a salt containing an anion ion or a combination thereof, such as. In particular, a lithium salt is preferable.

Organic solvents may be used conventional solvents known in the art, such as cyclic carbonates and / or linear carbonates, non-limiting examples of propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl Carbonate (DMC), dipropyl carbonate (DPC), dimethyl sulfoxide, acetonitrile, dimethoxyethane, diethoxyethane, tetrahydrofuran, N-methyl-2-pyrrolidone (NMP), ethylmethyl carbonate (EMC) Gamma butyrolactone (GBL), fluoroethylene carbonate (FEC), methyl formate, ethyl formate, propyl formate, methyl acetate, ethyl acetate, propyl acetate, pentyl acetate, methyl propionate, ethyl propionate, ethyl propionate, butyl propionate or these And mixtures thereof. Moreover, the halogen derivative of the said organic solvent can also be used.

In addition, for the purpose of improving charge and discharge characteristics, flame retardancy, etc., the electrolyte includes, for example, pyridine, triethyl phosphite, triethanolamine, cyclic ether, ethylene diamine, n-glyme, hexaphosphate triamide, Nitrobenzene derivative, sulfur, quinone imine dye, N-substituted oxazolidinone, N, N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxy ethanol, vinylene carbonate, aluminum trichloride, etc. This may be added. In some cases, in order to impart nonflammability, a halogen-containing solvent such as carbon tetrachloride and ethylene trifluoride may be further included, or carbon dioxide gas may be further included to further improve the high temperature storage characteristics.

The electrode for secondary batteries according to the present invention is not particularly limited as long as it is manufactured using a lithium-containing composite oxide having an olivine crystal structure as an electrode active material.

The olivine-based electrode active material represented by LiFePO ₄ is a compound of regular olivine structure, also known as mineral trypite, and octahedral oxygen occupied by tetrahedral anion structural unit (XO ₄ ) ^n- and transition metal M It belongs to the general group known as a polyanion compound with a. These general groups are Li _x MXO ₄ (olivine), Li _x M ₂ (XO ₄ ) ₃ (NASICON), VOPO ₄ , LiFe (P ₂ O ₇ ) or LiFe (P ₂ O ₇ ) or Fe ₄ (P ₂ O ₇ ) structures and structures associated with them. Here, X is made of a metal capable of occupying the tetrahedral position in the polyanion group, and may have P, As, S, Si, Mo, W, Al, or B as having a significant covalent bond property. In addition, in Li _x MPO ₄ , the metal may be at least one of Fe, Mn, Co, Ni, cu, Zn, Mg, Cr, V, Mo, Ti, Al, Nb, B, and Ga, but is not limited thereto. no. (Where 0.05 ≦ x ≦ 1.2)

The olivine-based electrode active material may be used as an electrode component of the positive electrode and / or the negative electrode, and particularly, a positive electrode capable of continuously achieving high capacity through improving the life characteristics of the olivine-based positive electrode is preferable.

The electrode of the present invention may be prepared by mixing a conventional positive electrode active material and / or negative electrode active material in addition to the olivine-based electrode active material described above.

As the cathode active material, a conventional cathode active material that can be used for a cathode of a conventional secondary battery may be used, and non-limiting examples thereof include LiM _x O _y (M = Co, Ni, Mn, Co _a Ni _b Mn _c ) and Lithium transition metal composite oxides (for example, lithium manganese composite oxides such as LiMn ₂ O ₄ , lithium nickel oxides such as LiNiO ₂ , lithium cobalt oxides such as LiCoO ₂ , and some of manganese, nickel, and cobalt oxides of these oxides Substituted with a transition metal or the like, or vanadium oxide containing lithium) or a chalcogen compound (for example, manganese dioxide, titanium disulfide, molybdenum disulfide, or the like). Preferably LiCoO ₂ , LiNiO ₂ , LiMnO ₂ , LiMn ₂ O ₄ , Li (Ni _a Co _b Mn _c ) O ₂ (0 <a <1, 0 <b <1, 0 <c <1, a + b + c = 1), LiNi _1-Y Co _Y O ₂ , LiCo _1-Y Mn _Y O ₂ , LiNi _1-Y Mn _Y O ₂ (where 0 ≦ Y <1), Li (Ni _a Co _b Mn _c ) O ₄ (0 <a <2, 0 <b <2, 0 <c <2, a + b + c = 2), LiMn _2-z Ni _z O ₄ , LiMn _2-z Co _z O ₄ ( Here, 0 <Z <2), LiCoPO ₄ , Li _{1 + a} Mn _2-a O ₄ (where a is 0 to 0.33), LiMnO ₃ , LiMn ₂ O ₃ , LiMnO ₂ , LiMn _2-a M _a 0 ₂ where M = Co, Ni, Fe, Cr, Zn or Ta, and a = 0.01 to 0.1, Li ₂ Mn ₃ MO ₈ , where M = Fe, Co, Ni, Cu or Zn ), LiMn ₂ O ₄ or a mixture thereof in which Li is partially substituted with alkaline earth metal ions.

The negative electrode active material may be a conventional negative electrode active material that can be used for the negative electrode of a conventional secondary battery, non-limiting examples of lithium metal or lithium alloy, carbon, petroleum coke, activated carbon, graphite lithium adsorbents such as graphite or other carbons. Non-limiting examples of the positive electrode current collector is a foil made by aluminum, nickel or a combination thereof, and non-limiting examples of the negative electrode current collector by copper, gold, nickel or copper alloy or a combination thereof Foils produced.

The method for manufacturing the electrode according to the present invention is not particularly limited, but is prepared by applying and drying a conventional method known in the art as an example, that is, an electrode slurry including a positive electrode active material or a negative electrode active material on a current collector. . In this case, a small amount of a conductive agent and / or a binder may be optionally added.

The secondary battery of the present invention using the above-mentioned electrolyte and electrode in combination is preferably a lithium secondary battery, and non-limiting examples thereof include a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery or a lithium ion polymer secondary. Batteries and the like.

The secondary battery according to the present invention may be preferably used as a power source for a vehicle, in particular, a hybrid electric vehicle, in view of excellent low temperature output characteristics, high temperature storage characteristics, rate characteristics, and the like. However, it is not limited thereto.

The secondary battery may be prepared by inserting a porous separator between a positive electrode and a negative electrode in a conventional manner known in the art and adding the electrolyte.

The separator that may be used in the present invention is not particularly limited, but a porous separator may be used, for example, a polypropylene-based, polyethylene-based, or polyolefin-based porous separator. Alternatively, a porous separator into which inorganic particles are introduced may also be used.

The shape of the secondary battery manufactured by the above method is not limited, but may be cylindrical, square, pouch type or coin type using a can.

In addition, the present invention (a) an electrode active material having an olivine-type crystal structure; And (b) a compound for producing a chemical reaction product except water through a chemical reaction with an acid (H ⁺ ). In this case, the electrode may be an anode and / or a cathode.

The electrode may be formed by coating the above-described compound on the surface of the electrode active material of the olivine crystal structure, or in combination with the electrode material, or by coating on the surface of the other electrode prepared. In addition, it may be formed on the surface of the electrode active material by performing charge and discharge using the above-described electrolyte solution.

As such, a compound that produces a chemical reaction product other than water through a chemical reaction with the acid (H ⁺ ) may be formed on a part or all of an electrode formed on part or all of the surface of an olivine-based electrode active material or a surface of a prepared electrode. The lithium secondary battery having the formed electrode not only prevents dissolution of the olivine-based electrode active material due to HX (X = F, Cl, Br, I) and consequent degeneration of the electrode active material, and consequently the electricity of the electrode. Increased resistance and gas generation can be prevented to improve battery life characteristics. In particular, since the dissolution rate of the electrode by HF increases at high temperature, the above-mentioned problem is fundamentally solved due to the reduced concentration of HF in the present invention, whereas a great problem arises in battery cycle life and storage at high temperature. By doing so, there is an advantage that the high temperature storage characteristics can be improved.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. However, the following examples are for illustrating the present invention, and the scope of the present invention is not limited thereto.

Example 1

LiFePO ₄ was used as a positive electrode active material, and a conductive agent and a binder were added to NMP (N-methyl-2-pyrrolidone) to prepare a positive electrode slurry, and then a positive electrode was prepared by coating it on an aluminum (Al) current collector.

As the negative electrode active material, artificial graphite and amorphous graphite (hard carbon) were mixed to prepare a negative electrode slurry by adding a binder to NMP, and then coated on a copper (Cu) current collector to prepare a negative electrode.

Electrolyte solution is EC / EMC (1: 2 volume ratio) solution in 1M LiPF ₆ 0.02 parts by weight of ammonium benzoate (AB) and 1 part by weight of vinylene carbonate were added to the electrolyte.

After interposing a polyolefin-based separator between the prepared positive electrode and the negative electrode, an electrolyte solution to which the above-described electrolyte additive was added was prepared to manufacture a battery.

Comparative Example 1

A lithium secondary battery was manufactured in the same manner as in Example 1, except that ammonium benzoate (AB) was not used in the electrolyte.

Experimental Example 1. Comparative evaluation of the HF concentration of the electrolyte

In order to evaluate the HF concentration increase amount in the electrolyte solution containing the electrolyte additive according to the present invention, the following experiment was performed.

The electrolyte solution of Example 1 to which ammonium benzoate was added was used, and an electrolyte solution without an electrolyte additive was used as a control thereof. The initial acidity (pH) of the electrolyte was measured, and the changed acidity (pH) was measured again after exposure to air for 1 month at room temperature.

As a result of the experiment, the electrolyte solution of the present invention showed that the electrolyte solution additive was not used in the initial acidity (pH) as well as the increase in HF concentration in the electrolyte solution stored at room temperature compared to the electrolyte solution of Comparative Example 1 was significantly excellent (Table 1 Reference). This demonstrates that not only can the concentration of HF in the cell be significantly reduced through chemical reaction of electrolyte additives, such as ammonium benzoate, contained in the electrolyte, but also HF, and this effect can be sustained.

Example 1 Comparative Example 1 Initial residual HF amount (ppm) 20-30 ppm Initial pH after 1 month 5.18 3.33 Remaining HF amount (ppm) 23.5944 2001.8256

Experimental Example 2. Evaluation of Long-Term Storage Characteristics of Lithium Secondary Battery

In order to evaluate the high temperature performance of the lithium secondary battery including the electrolyte additive according to the present invention, the following experiment was conducted.

Each battery is charged at a current of 4.2C to 3V with a current of 0.5C, measured for its initial capacity, and stored for 8 weeks, followed by repeated charging and discharging at 4.2C to 3V with a current of 0.5C. Measured.

As a result of the experiment, it was found that the battery of Example 1 using ammonium benzoate as the electrolyte component was improved about 7% of the high temperature discharge power retention rate compared to the battery of Comparative Example 1 having a conventional electrolyte solution (see Table 2). Through this, the lithium secondary battery of the present invention was confirmed that the long-term storage characteristics are excellent.

Ammonium benzoate content in electrolyte (Based on 100 parts by weight of electrolyte) Battery retention characteristics after 8 weeks (%) Example 1 0.02 parts by weight 89 Comparative Example 1 X 82

In the present invention, by using an olivine-based electrode in combination with an electrolyte that reduces the concentration of HX through a chemical reaction with HX (X = F, Cl, Br, I), it is possible to provide improved long-life characteristics and high temperature storage characteristics of the battery. .

Claims (12)

(a) an anode; (b) a cathode; (c) separators; And (d) an electrolyte containing an electrolyte salt and an organic solvent, wherein the positive electrode, the negative electrode, or the positive electrode is an electrode including an electrode active material having an olivine crystal structure, Electrolyte is a secondary battery characterized in that it comprises a compound (e) to produce a chemical reaction product except water through a chemical reaction with acid (H ⁺ ). The secondary battery of claim 1, wherein the acid is HX (X = F, Cl, Br, I) formed by a reaction between (i) an electrolyte salt containing a lithium-containing halide salt and (ii) moisture present in the battery. . The secondary battery of claim 1, wherein the compound (e) is an ion-bonding salt compound, and includes anion except for hydroxyl group (OH ⁻ ). The method of claim 3, wherein the anion except for the hydroxyl group is selected from the group consisting of benzoate, phthalate, malate, succinate and citrate. Secondary battery. The method of claim 1, wherein the electrolyte is a chemical reaction product except water through (i) HX (X = F, Cl) present in the battery and (ii) acid (H ⁺ ) contained in the electrolyte solution. A secondary battery characterized in that the resulting compound is a chemical reaction to reduce the HX (X = F, Cl) concentration. The secondary battery of claim 1, wherein an acidity (pH) of the electrolyte is in a range of 2 to 6. 6. The secondary battery of claim 1, wherein the content of the compound (e) is in a range of 0.001 to 10 parts by weight based on 100 parts by weight of an electrolyte. The method of claim 1, wherein the electrode active material having an olivine-type crystal structure is Li _x MPO ₄ (M = Fe, Mn, Co, Ni, Cu, Zn, Mg, Cr, V, Mo, Ti, Al, Nb, B And Ga, at least one selected from Ga, and 0.05 ≦ x ≦ 1.2). The method of claim 1, wherein the secondary battery is characterized in that the dissolution of the transition metal in the olivine-type electrode active material is prevented by decreasing the concentration of HX (X = F, Cl) present in the battery. battery. The secondary battery according to claim 1, which is a lithium secondary battery. (a) an electrode active material having an olivine-type crystal structure; And (b) compounds that produce chemical reaction products, except water, through chemical reactions with acids (H ⁺ ) Secondary battery electrode comprising a. 12. The method of claim 11, wherein the electrode is used as a component of the electrode material or a coating component of the electrode prepared by using a compound that produces a chemical reaction product except water through a chemical reaction with acid (H ⁺ ) Characterized in that the electrode produced.