JP2009129736A - Calcium/air battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an air battery using a negative electrode active material which is superior in stability under normal environment than metal lithium, and of low cost in terms of material cost. <P>SOLUTION: A gas diffusion type electrode 1 which is obtained by pressing on a titanium mesh a sheet-like electrode fabricated by mixing and roll-forming carbon black powder and a binder (polytetra-fluoroethylene) is fixed to a positive electrode case 4 by spot welding, and a separator 2 in which an electrolytic solution obtained by dissolving calcium perchlorate into acetonitrile at a concentration of 1 mol/liter is injected a proper quantity and impregnated is overlapped on the electrode 1, and further, a negative electrode 3 consisting of calcium which is pressurized and adhered on a stainless negative electrode case 6 is superposed on this and, by inserting and caulking this in a recess of a polypropylene gasket 5, a coin type calcium/air battery is manufactured. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a calcium / air battery.

  Commercially available zinc / air batteries have a large discharge capacity of about 300 mAh / g, and are therefore mainly used for hearing aids. However, since a voltage of only 1V can be obtained as compared with a lithium battery using a non-aqueous electrolyte, it is considered difficult to use in a wide range.

  In recent years, by using electrochemical reduction of oxygen similar to a zinc / air battery as a positive electrode reaction system, combined with metallic lithium instead of zinc as a negative electrode, and using a nonaqueous solvent system as an electrolyte, / Attempts have been made to produce air secondary batteries.

Until now, as described in Patent Documents 1 and 2 below, by using a gas diffusion electrode to which an appropriate catalyst is added or a stable ionic liquid, the discharge capacity reaches 5000 mAh / g. Successful construction of high energy density battery.
JP 2004-119278 A Japanese Patent Laid-Open No. 2005-26023

  However, metallic lithium used as a negative electrode has low stability under normal circumstances such as contact with air or water, and is dangerous to safety. There are problems such as higher material costs for the negative electrode material compared to a kind of zinc / air battery.

  The present invention has been made in view of the above problems, and the problem to be solved by the present invention is that the negative electrode active material is superior to metallic lithium in stability under a normal environment and inexpensive in terms of material cost. It is providing the air battery using.

In the present invention, in order to solve the above problem, as described in claim 1,
Metal calcium or an alloy containing calcium is used as a negative electrode active material, an organic electrolyte is used, a gas diffusion electrode having carbon as a constituent element is used as a positive electrode, and oxygen in the air is used as a positive electrode active material Constructs a calcium / air battery.

In the present invention, as described in claim 2,
2. The calcium / air battery according to claim 1, wherein the organic electrolyte is an electrolyte dissolved in acetonitrile or dimethylformamide.

In the present invention, as described in claim 3,
3. The calcium / air battery according to claim 1, wherein the gas diffusion electrode contains a transition metal metal oxide containing at least one of Co, Ni, Fe, and Mn.

In the present invention, as described in claim 4,
3. The calcium / air battery according to claim 1, wherein the gas diffusion electrode contains a transition metal-based porphyrin or transition metal-based phthalocyanine containing at least one of Co, Ni, Fe, and Mn. Constitute.

In the present invention, as described in claim 5,
The gas diffusion electrode contains a substance obtained by heating a transition metal-based porphyrin or transition metal-based phthalocyanine containing at least one of Co, Ni, Fe, and Mn to a thermal decomposition temperature or higher in an inert gas. The calcium / air battery according to claim 1, 2, or 4 is configured.

  According to the present invention, a calcium / air battery is manufactured which is superior in terms of energy density and voltage as compared to a zinc / air battery, is safer than a lithium / air battery, and is inexpensive in terms of material cost. And can be provided.

  The present invention uses oxygen in the air as a positive electrode active material, and as a negative electrode active material, metal calcium or an alloy containing calcium, which is superior in stability under a normal environment than metal lithium and inexpensive in terms of material cost (for example, A calcium / air battery using a calcium-tin alloy containing 50% by weight or more of calcium, using an organic electrolytic solution as an electrolytic solution, and using a gas diffusion electrode having carbon as a constituent element as a positive electrode. It is to provide.

  Furthermore, in the calcium / air battery according to the present invention, excellent battery characteristics can be obtained when acetonitrile or dimethylformamide is used as the organic solvent of the organic electrolyte.

  Further, in order to construct a high energy density / high voltage calcium / air battery, a transition metal metal oxide containing at least one of Co, Ni, Fe, and Mn is added to the gas diffusion type electrode. By using this method, a high energy density / high voltage calcium / air battery can be obtained.

  For the same purpose, transition metal-based porphyrin or transition metal-based phthalocyanine containing at least one of Co, Ni, Fe, and Mn is added to a gas diffusion electrode including carbon, a binder, and a current collector sheet as constituent elements. As a result, the same effect as in the case of the metal oxide can be obtained.

  Furthermore, the carbon powder to which carbon and transition metal porphyrin containing at least one of Co, Ni, Fe, and Mn or transition metal phthalocyanine is added is heat-treated in an inert gas using an electric furnace or the like. Thus, by using a gas diffusion electrode using a powder of a product obtained by thermally decomposing at least part of the transition metal porphyrin or transition metal phthalocyanine, the performance of the battery is improved. A calcium / air battery with improved density and voltage characteristics can be produced.

  The structure and constituent materials of the calcium / air battery according to the present invention will be described below.

  In order to form a gas diffusion electrode in which an electrochemical reduction reaction of oxygen as a positive electrode active material proceeds, a mixture of carbon powder and binder (binder) powder such as polytetrafluoroethylene (PTFE) is made of titanium. Formed by means such as a method of pressure forming on a support such as a mesh, or a method of dispersing the above-mentioned mixture in a solvent such as an organic solvent to form a slurry and applying it on a metal mesh and drying, etc. This surface is in contact with the atmosphere, and the other surface is in contact with the electrolyte. Further, in order to increase the strength of the electrode and prevent leakage of the electrolytic solution, it is possible to produce an electrode having more excellent stability by performing not only cold pressing but also hot pressing.

  The reaction on the gas diffusion type electrode can be expressed as follows.

Ca ²⁺ + (1/2) O ₂ + 2e ⁻ → CaO (1)
Calcium ions (Ca ²⁺ ) in the above formula are dissolved from the negative electrode by electrochemical oxidation and migrate to the positive electrode surface. Oxygen (O ₂ ) is taken into the gas diffusion electrode from the atmosphere.

  The negative electrode is formed by forming calcium, which is a negative electrode active material, into a sheet shape, and pressing the sheet onto a conductor such as nickel or stainless steel. As the negative electrode active material, an alloy containing calcium as a main component (for example, a calcium-tin alloy containing 50% by weight or more of calcium) can be used in addition to calcium metal.

  The reaction of the negative electrode (metallic calcium) during discharge can be expressed as follows.

Ca → Ca ²⁺ + 2e ⁻ (2)
Any electrolyte solution that can dissolve calcium as shown in the formula (2) can be used. For example, a metal salt containing calcium ions (for example, calcium perchlorate), which is an electrolyte, is dissolved in an organic solvent. The organic electrolyte obtained in this way can be used, or a solid electrolyte or ionic liquid can also be used.

  Various other publicly known materials can be used for other constituent elements such as a structural material such as a separator and a battery case, and these are not particularly limited.

  In the following embodiments, the battery was manufactured in an argon atmosphere, and the battery discharge test was performed in a normal living environment.

  Exemplary embodiments of a calcium / air battery according to the present invention will be described below in detail with reference to the accompanying drawings. In addition, this invention is not limited to what was shown to the following example of embodiment, In the range which does not change the summary, it can implement suitably.

[Embodiment 1]
Carbon black powder and a binder (polytetrafluoroethylene) were mixed at a weight ratio of 70:30 and roll-formed to produce a sheet-like electrode. The sheet-like electrode was pressed onto a titanium mesh to obtain a gas diffusion electrode. Using this, a coin-type calcium / air battery was produced.

  FIG. 1 is a schematic view of the cross section, in which 1 is a gas diffusion electrode, 2 is a separator (electrolyte impregnation), 3 is a negative electrode, 4 is a positive electrode case, 5 is a gasket, and 6 is a negative electrode case.

  A circular air hole (18 mm in diameter) for taking oxygen into the gas diffusion electrode 1 was formed on the bottom surface of the positive electrode case 4. The gas diffusion type electrode 1 was placed on a stainless steel positive electrode case 4, and the titanium mesh at the outer edge of the electrode was fixed to the positive electrode case 4 by spot welding.

  In addition, the polytetrafluoroethylene dispersion was applied to the outer edge of the electrode, dried at about 100 ° C., and the solvent was removed to prevent leakage of the electrolyte from the outer edge of the gas diffusion electrode 1.

  A microporous separator 2 made of polypropylene is disposed on the gas diffusion electrode 1, and after an appropriate amount of electrolyte is injected and impregnated therein, the positive electrode portion is placed on a stainless negative electrode case 6 (in FIG. 1, the lower surface). ) Was covered with a metal calcium negative electrode 3 in pressure contact, inserted into the recess of the polypropylene gasket 5, pressed and caulked to produce a coin-type calcium / air battery having a thickness of 2 mm and a diameter of 23 mm. .

  Examples of the electrolyte include propylene carbonate (PC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), γ-butyrolactone (GBL), N, N-dimethylformamide (DMF), acetonitrile (AN In each of the seven types of solvents, calcium perchlorate was dissolved and used at a concentration of 1 mol / liter.

The battery was subjected to a discharge test at a current density of 0.05 mA / cm ² (standardized by the area of the gas diffusion electrode 1 exposed to the atmosphere) and a discharge end voltage of 1.0 V.

  As a result, it was confirmed that all the batteries showed discharge behavior and could be operated as calcium / air batteries.

  FIG. 2 shows the discharge characteristics of a battery using AN, DMC, and GBL as organic solvents. From this figure, it can be seen that AN has the largest discharge capacity of 800 mAh / g (standardized by battery weight) and the average discharge voltage is 2.1 V, which is a high voltage. In the case of DMC and GBL, the voltage drop from the open circuit voltage was very large, and the discharge capacity was also significantly inferior to that of AN.

  Table 1 shows data related to the discharge measurement of all the batteries.

この表より、使用する溶媒の種類によって、放電電圧や放電容量が著しく異なることがわかる。カルシウム/空気電池は、使用する溶媒によって、大放電容量を示し優れた特性を示すもの（ＡＮ、ＤＭＦ)、中庸なもの（ＤＭＣ、ＤＥＣ、ＥＭＣ)、小さな放電容量しか示さないもの（ＰＣ、ＧＢＬ）に区別されることがわかった。

From this table, it can be seen that the discharge voltage and discharge capacity differ significantly depending on the type of solvent used. Depending on the solvent used, calcium / air batteries have large discharge capacity and excellent characteristics (AN, DMF), moderate (DMC, DEC, EMC), and small discharge capacity (PC, GBL). ).

  As described above, according to the present embodiment, it was found that the calcium / air battery can obtain a large discharge capacity by using AN or DMF as the solvent used in the electrolytic solution. It has also been confirmed that similar performance can be obtained even if a mixed solvent of AN and DMF is used.

[Embodiment 2]
The gas diffusion electrode 1 is a transition metal metal oxide containing at least one of Co, Ni, Fe, and Mn that is highly active in oxygen reduction reaction (as shown below, it acts as a catalyst for electrode reaction. The battery performance can be improved. The details of the experimental method and experimental results will be described below.

Transition metal oxide (Co ₃ O ₄ , NiO, Fe ₂ O ₃ , MnO ₂ ), carbon black powder, and binder (polytetrafluoroethylene) are mixed at a weight ratio of 50:30:30 and roll-formed. A sheet electrode was prepared. The electrode manufacturing method and battery manufacturing method after this step were performed in the same manner as in the first embodiment. As for the electrolytic solution, as in the first embodiment, a battery was prepared using seven types of organic solvents.

  The battery discharge test was performed in the same manner as in the first embodiment. As a result, as compared with the first embodiment, the discharge voltage was improved by 0.1 to 0.2 V in any of the batteries. Table 2 shows the discharge capacity of the battery according to the present embodiment together with the result of adding no catalyst in the first embodiment.

いずれの電池でも、ガス拡散型電極１への触媒添加により、放電容量が向上していることがわかる。これは、これらの遷移金属酸化物が正極での酸素還元反応に対して触媒活性を有していることを示している。しかしながら、本実施の形態例においても使用する溶媒によって、大放電容量を示し優れた特性を示すもの（ＡＮ、ＤＭＦ）、中庸なもの（ＤＭＣ、ＤＥＣ、ＥＭＣ）、小さな放電容量しか示さないもの（ＰＣ、ＧＢＬ）に区別されることがわかった。

In any of the batteries, it can be seen that the discharge capacity is improved by adding the catalyst to the gas diffusion electrode 1. This indicates that these transition metal oxides have catalytic activity for the oxygen reduction reaction at the positive electrode. However, also in this embodiment, depending on the solvent used, those having a large discharge capacity and showing excellent characteristics (AN, DMF), moderate (DMC, DEC, EMC), and those showing only a small discharge capacity ( PC, GBL).

[Embodiment 3]
By adding porphyrin or phthalocyanine, which is a macrocyclic organic compound having high activity in oxygen reduction reaction and containing Co, Ni, Fe, Mn as a central metal, to the gas diffusion electrode 1, the performance of the battery can be improved. (Again, this is called a catalyst because the additive is catalytic). The details of the experimental method and experimental results will be described below. Further, a porphyrin compound containing a central metal (M = Co, Ni, Fe, Mn) is abbreviated as MP, and a phthalocyanine compound containing a central metal (M = Co, Ni, Fe, Mn) is abbreviated as MPc.

  A transition metal macrocyclic organic compound (MP, MPc, M = Co, Ni, Fe, Mn) and carbon black powder are dispersed in an aqueous solution of butanol at a weight ratio of 5: 3, vigorously stirred, and suction filtered. The powder was dried at 100 ° C. overnight. The catalyst / carbon mixed powder and the binder (polytetrafluoroethylene) were mixed at a weight ratio of 8: 2 and roll-molded to produce a sheet-like electrode. The electrode manufacturing method and battery manufacturing method after this step were performed in the same manner as in the first embodiment. As for the electrolytic solution, as in the first embodiment, a battery was prepared using seven types of organic solvents.

  The battery discharge test was performed in the same manner as in the first embodiment. As a result, as compared with the first embodiment, the discharge voltage was improved by 0.1 to 0.2 V in any of the batteries. Table 3 shows the discharge capacity of the battery according to the present embodiment together with the result of adding no catalyst in the first embodiment.

いずれの電池でも、ガス拡散型電極１への触媒添加により、放電容量が向上していることがわかる。これは、これらの遷移金属系大環状有機化合物が正極での酸素還元反応に対して触媒活性を有していることを示している。また、電解液については、実施の形態例１、２と同様に、ＡＮ及びＤＭＦ溶媒を用いたものが、良好な電池性能を示した。

In any of the batteries, it can be seen that the discharge capacity is improved by adding the catalyst to the gas diffusion electrode 1. This indicates that these transition metal-based macrocyclic organic compounds have catalytic activity for the oxygen reduction reaction at the positive electrode. As for the electrolytic solution, as in Embodiments 1 and 2, those using AN and DMF solvents showed good battery performance.

[Embodiment 4]
By adding porphyrin or phthalocyanine, which is a macrocyclic organic compound having high activity in oxygen reduction reaction and containing Co, Ni, Fe, Mn as a central metal, to the gas diffusion electrode 1, the performance of the battery can be improved. What can be achieved is described in the third embodiment. In this embodiment, a technique for further improving the performance of the macrocyclic organic compound catalyst will be described.

  A transition metal-based macrocyclic organic compound (MP, MPc, M = Co, Ni, Fe, Mn) catalyst / carbon mixed powder produced in the same manner as in Embodiment 3 was thoroughly pulverized, and argon gas was circulated. Heat treatment was performed in an electric furnace at 1000 ° C. As will be described later, the catalytic activity is improved by this heat treatment. In this method, if the flow gas is an inert gas and the heat treatment temperature is 400 ° C. or higher, the same catalytic activity improvement effect can be obtained. The electrode manufacturing method and the battery manufacturing method after the heat treatment were performed in the same manner as in the first embodiment. As for the electrolytic solution, as in the first embodiment, a battery was prepared using seven types of organic solvents. The battery discharge test was performed in the same manner as in the first embodiment.

  As a result, in any of the batteries, the discharge voltage was improved by 0.2 to 0.3 V as compared with the third embodiment. Table 4 shows the discharge capacity of the battery according to the present embodiment together with the result of adding no catalyst in the first embodiment.

いずれの電池でも、実施の形態例１に示した触媒無添加の電池よりも放電容量が向上していることがわかる。また、実施の形態例３の結果と比較しても、放電容量は更に向上することがわかった。この結果は、カーボン粉末中に分散した遷移金属系大環状有機化合物を熱処理することによって、酸素還元反応に対する触媒活性が向上することを示している。また、電解液については、実施の形態例１、２と同様に、ＡＮ及びＤＭＦ溶媒を用いたものが、良好な電池性能を示した。

In any of the batteries, it can be seen that the discharge capacity is improved as compared with the battery with no catalyst shown in the first embodiment. Further, it was found that the discharge capacity was further improved compared with the result of the third embodiment. This result shows that the catalytic activity for the oxygen reduction reaction is improved by heat-treating the transition metal macrocyclic organic compound dispersed in the carbon powder. As for the electrolytic solution, as in Embodiments 1 and 2, those using AN and DMF solvents showed good battery performance.

  It is considered that the transition metal-based macrocyclic organic compound is completely thermally decomposed by the heat treatment in an inert gas at 1000 ° C. described above. As a result, the catalytic activity is improved. Even if this thermal decomposition is not complete, if at least a part of the transition metal macrocyclic organic compound is thermally decomposed by heat treatment in an inert gas, the degree of thermal decomposition is increased. Depending on the situation, the catalytic activity may be improved. That is, the gas diffusion electrode 1 is made of a substance obtained by heating a transition metal-based porphyrin or transition metal-based phthalocyanine containing at least one of Co, Ni, Fe, and Mn to a temperature equal to or higher than its thermal decomposition temperature in an inert gas. By containing, an electrode with improved catalytic activity may be obtained.

[Comparative Example 1]
The discharge performance of the calcium / air battery obtained in the present invention was compared with that of a lithium / air battery and a zinc / air battery.

  In the lithium / air battery of the comparative example, a lithium foil was used for the negative electrode, and the CoP catalyst-added gas diffusion electrode 1 subjected to the heat treatment of Example 4 was used for the positive electrode. The electrolyte was prepared by dissolving lithium perchlorate in an AN solvent at a concentration of 1 mol / liter. The battery case, separator, and the like were the same as those in the first embodiment.

  Moreover, the zinc / air battery used the gas diffusion type electrode 1 to which the CoP catalyst was added, in which the zinc foil was used for the negative electrode and the heat treatment of the fourth embodiment was applied to the positive electrode. As the electrolytic solution, an aqueous potassium hydroxide solution having a concentration of 8 mol / liter was used. The battery case was the same as that in Embodiment 1, and the separator was hydrophilic.

  The discharge curves of the lithium / air battery and the zinc / air battery (discharge end voltage 0.5 V) produced in this manner were used using the AN-based electrolyte solution and heat-treated CoP catalyst shown in the fourth embodiment. FIG. 3 shows the results of the calcium / air battery. From this figure, it can be seen that the calcium / air battery and the lithium / air battery have higher discharge voltage and considerably higher discharge capacity than the commercially available and widely used zinc / air battery. In addition, although the average discharge voltage is slightly lower than that of the lithium / air battery, the calcium / air battery has a discharge capacity that is about 1.4 times larger and has a very high energy density.

  Calcium has a higher reserve than lithium and is advantageous in terms of cost and has high chemical stability and is advantageous in terms of safety.

  From the above results, it can be seen that the calcium / air battery is a high-performance battery having features of high energy density, low cost, and high safety.

[Industrial applicability]
As described above, according to the present invention, a calcium / air battery having features of high energy density, low cost, and high safety can be manufactured and provided, and this battery can be used as a driving power source for various electronic devices. As a result, a great effect can be achieved.

1 is a cross-sectional view of a coin-type calcium / air battery according to the present invention. It is a discharge curve of a calcium / air battery (no catalyst added) using AN, DMC, and GBL as organic solvents. 3 is a discharge curve of a calcium / air battery, a lithium / air battery, and a zinc / air battery in Comparative Example 1. FIG.

Explanation of symbols

  1: Gas diffusion type electrode, 2: Separator, 3: Negative electrode, 4: Positive electrode case, 5: Gasket, 6: Negative electrode case.

Claims (5)

  Metal calcium or an alloy containing calcium is used as a negative electrode active material, an organic electrolyte is used, a gas diffusion electrode having carbon as a constituent element is used as a positive electrode, and oxygen in the air is used as a positive electrode active material Calcium / air battery.   The calcium / air battery according to claim 1, wherein the organic electrolytic solution is an electrolyte dissolved in acetonitrile or dimethylformamide.   The calcium / air battery according to claim 1, wherein the gas diffusion electrode contains a transition metal metal oxide containing at least one of Co, Ni, Fe, and Mn.   3. The calcium / air battery according to claim 1, wherein the gas diffusion electrode contains transition metal porphyrin or transition metal phthalocyanine containing at least one of Co, Ni, Fe, and Mn.   The gas diffusion electrode contains a substance obtained by heating a transition metal-based porphyrin or transition metal-based phthalocyanine containing at least one of Co, Ni, Fe, and Mn to a thermal decomposition temperature or higher in an inert gas. The calcium / air battery according to claim 1, 2, or 4.

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