JP5560736B2 - Fuel cell - Google Patents

Description

The present invention relates to a fuel cell using catalytic metal-supported carbon.

  Conventionally, catalytic metal-supported carbon in which a catalytic metal such as Pt is supported on the surface of carbon particles has been used in various ways as an electrode material in the field of electrochemistry.

  For example, the catalyst layer of a fuel cell uses a catalyst metal-supported carbon in which a catalyst metal such as Pt is supported on the surface of carbon particles, which is important for promoting an electrochemical reaction of hydrogen or oxygen smoothly. It plays a role (for example, Patent Documents 1 and 2).

  Further, the present inventors have found that the charge / discharge current can be increased by mixing the catalyst metal-supported carbon with the positive electrode material of the lithium ion battery, and a patent application has already been filed for a lithium ion battery using this. (Japanese Patent Application No. 2008-237350).

JP 2006-277792 A JP 2003-308849 A

  However, the conventional catalyst metal-supporting carbon may cause an electrochemical oxidation reaction of the carbon supporting the catalyst metal at a high potential.

  For this reason, for example, a potential shift phenomenon (that is, when the hydrogen supply is partially insufficient in the plane of the fuel cell, the potential at which the positive electrode potential greatly exceeds the normal operating potential of 1 V or less (vs SHE)) In some cases, a phenomenon that reaches 1.5 V or more occurs (potential shift phenomenon is known in phosphoric acid type fuel cells, but the inventors have also found in solid polymer fuel cells. It has been confirmed that the same phenomenon occurs), but the catalytic metal-supported carbon is exposed to a high potential, and it may be altered and the catalytic activity may be reduced.

Further, such a potential shift phenomenon is known to occur also in a Li ion battery or a sodium ion battery, and there is a concern that oxidation of carbon as a conductive agent contained in a positive electrode active material becomes a problem. Furthermore, in the lithium ion battery, the applicant of the present application tried to increase the charge / discharge current by mixing the catalyst metal-supported carbon with the positive electrode material as described in Japanese Patent Application No. 2008-237350 filed earlier. In this case, when the positive electrode material is charged at a high potential (for example, Li ₂ CoPO ₄ F), there is a problem that the graphite structure of carbon is electrochemically oxidized and deteriorated. For this reason, charging / discharging in a positive electrode cannot be performed smoothly, but it was difficult to utilize it effectively, although the positive electrode substance has a large energy density.

  The present invention has been made in view of the above-described conventional situation, and a catalytic metal-supporting carbon in which carbon and a solvent are stable and hardly deteriorated even when the catalytic metal-supporting carbon is exposed to a high potential, and the catalytic activity is hardly reduced. Providing is a problem to be solved.

Catalytic metal supporting carbon used in the present invention is characterized in that a conductive diamond-like carbon emissions.

The catalytic metal supporting carbon used in the present invention, the carbon that is carrying a catalyst metal and a conductive diamond-like carbon emissions. Conductive diamond-like carbon or glassy carbon has a wider potential window than graphite in an aqueous solvent. Also, non-aqueous solvent electrolytes such as lithium ion battery electrolytes have a wider potential window than graphite. Therefore, even when used in an aqueous system such as a catalyst layer of a fuel cell, or when used in a non-aqueous electrolyte solution such as a lithium ion battery, carbon can stably exist and is supported on the carbon. A smooth electrochemical reaction can proceed on the catalytic metal. In addition, there is little risk of decomposing the solvent to a high potential.

It is a cyclic voltammogram in the dilute sulfuric acid of carbon black and carbon black graphitized by heat treatment. It is a cyclic voltammogram in the dilute sulfuric acid of various electrodes. Potential of the electrode in the Experimental Examples 1 to 3 and a lithium-ion battery electrolyte solution obtained by dissolving LiPF ₆ in the positive electrode for lithium batteries of Comparative Examples 1 to 3 - a current curve. Potential of the electrode in the experimental examples 1, 3 and a lithium-ion battery electrolyte solution obtained by dissolving the positive electrode LiBF ₄ and for lithium batteries of Comparative Examples 1 to 3 - a current curve. It is the electric potential-current curve of the electrode in the electrolyte solution for lithium ion batteries which melt | dissolved LiTFSI of the positive electrode for lithium batteries of Experimental example 1 and Comparative Examples 1-3. 3 is a potential-current curve of electrodes of Reference Example 1 and Experimental Example 1. 2 is a graph showing cell characteristics of the fuel cell of Example 1. FIG.

In the present invention as the carbon carrying the catalyst metal, a conductive diamond-like carbon emissions.

Conductive diamond-like carbon is a carbon having an amorphous structure in which both diamond bonds (SP ₃ hybrid orbital bonds between carbons) and graphite bonds (SP ₂ hybrid orbital bonds between carbons) are mixed. The conductivity is 1000 Ωcm or less. However, in addition to the amorphous structure, those having a phase composed of a crystal structure partially composed of a graphite structure (that is, a hexagonal crystal structure composed of SP ₂ hybrid orbital bonds) and thereby exhibiting conductivity are also included. . Diamond-like carbon having properties intermediate between graphite and diamond adjusts the conductivity by adjusting the ratio of SP ₂ hybrid orbital bonds and SP ₃ hybrid orbital bonds of the carbon atoms constituting diamond-like carbon during film formation. be able to.
In the specification and drawings, the conductive diamond-like carbon may be simply referred to as “diamond-like carbon”.

  Further, glassy carbon refers to glassy carbon that is generated when carbon is denatured at a high temperature in a reducing atmosphere.

  In aqueous electrolytes, conductive diamond-like carbon and glassy carbon have a much wider potential window than carbon black and graphite. For example, Carbon, vol. 11, 403 (1973) shows the results of measuring a cyclic voltammograph in 2N sulfuric acid using carbon black (Vulcan XC-72), which is often used as a catalyst carbon support, as an electrode. (See FIG. 1 (a)), it has only a narrow potential window of about 0.05V to 1.0V with respect to the standard hydrogen electrode. In addition, when the carbon black is heat-treated at 2700 ° C. to have a graphite structure, the range of the potential window is slightly widened, but it is still about 0.05 to 1.2V. (See FIG. 1 (b)).

  In contrast, diamond-like carbon and glassy carbon, as shown in Fig. 2, have a much wider potential window than carbon black and graphite (started in 1996, Research Project for Future Development Science Promotion Project). For this reason, diamond-like carbon or glassy carbon loaded with a catalytic metal can exist stably even at a high potential. For this reason, for example, if this is used for a catalyst layer of a fuel cell, even if an abnormal phenomenon called a potential shift phenomenon occurs and the potential becomes high, the carbon of the catalyst layer becomes difficult to change and And a smooth electrochemical reaction can proceed.

On the other hand, the catalyst metal supported on the catalyst metal-supporting carbon used in the present invention is not particularly limited as long as it is a metal having a function as an electrochemical reaction catalyst. For example, Pt, Ru, Rh, Pd, Ag, Ir, Au, Ni, Cu, etc. are mentioned. These may be used alone or an alloy thereof.

<Experimental example>
Hereinafter, in order to prove the effect of the invention of the catalytic metal-supported carbon used in the present invention, various conductive substance powders are mixed with PTFE powder to produce a disk-shaped electrode by a hot press method, and a potential-current curve is obtained. It was measured.

(Experimental example 1)
In Experimental Example 1, a glassy carbon pulverized product (average particle size 0.5 μm) and PTFE powder were mixed at a weight ratio of 80:20, and an 8 mmφ disk-shaped electrode was produced by hot pressing.

(Experimental example 2)
In Experimental Example 2, glassy carbon (average particle size 8 μm) and PTFE powder were mixed at a weight ratio of 80:20, and a disk-shaped electrode of 8 mmφ was produced by hot pressing.

(Experimental example 3)
In Experimental Example 3, diamond-like carbon powder (average particle size 0.03 μm) and PTFE powder were mixed at a weight ratio of 80:20, and a disk-shaped electrode of 8 mmφ was produced by hot pressing.

(Comparative Example 1)
Comparative Example 1 is a commercially available glassy carbon plate itself.

(Comparative Example 2)
In Comparative Example 2, acetylene black (“HS-100” manufactured by Denki Kagaku Kogyo Co., Ltd.) and PTFE powder were mixed at a weight ratio of 80:20, and a disk-shaped electrode of 8 mmφ was produced by hot pressing.

(Comparative Example 3)
In Experimental Example 3, acetylene black (“HS-100” manufactured by Denki Kagaku Kogyo Co., Ltd.) was heat-treated at 3000 ° C. for 3 hours in a vacuum and PTFE powder were mixed at a weight ratio of 80:20, and hot pressing was performed. Thus, a disk-shaped electrode of 8 mmφ was produced.

<Measurement of potential-current curve>
With respect to the electrodes of Experimental Examples 1 to 3 and Comparative Examples 1 to 3 prepared as described above, potential scanning was performed in an electrolyte solution for a lithium ion battery, and a potential-current curve was measured. The electrolytic solution was prepared as follows. That is, a mixed solution is prepared so that ethylene carbonate, dimethyl carbonate, and sebaconitrile are in a volume ratio of 25:25:50, and the lithium electrolyte (any one of LiPF ₆ , LiBF _4, and LiTFSI) is 1 mol / L. The so-dissolved solution was used as an electrolytic solution and placed in a three-electrode electrolytic cell container.

In the measurement of the potential-current curve, the above electrode (area 1.0 cm ² ) was used as a working electrode, a platinum net as a counter electrode, and Li metal as a reference electrode. The sweep speed was 5 mV / sec.

The results are shown in FIGS.
(Measurement results in an electrolyte solution for lithium ion batteries in which LiPF ₆ was dissolved)
As a result, as shown in FIG. 3, the electrodes of Experimental Example 1 using diamond-like carbon and Experimental Examples 2 and 3 using glassy carbon powder have a wider potential window than the glassy carbon plate electrode of Comparative Example 1. I found out that In contrast, in Comparative Example 2 in which carbon black was used as an electrode as it was, the potential window was narrow, and in Comparative Example 3 in which carbon black was heat-treated and graphitized, the potential window was slightly widened, but oxidation exceeded 4 V. It turned out that an electric current began to flow and the potential window was narrower than those of Experimental Examples 1 to 3.

(Measurement results in an electrolyte solution for lithium ion batteries in which LiBF ₄ is dissolved)
Further, as shown in FIG. 4, the electrode of Experimental Example 3 using diamond-like carbon powder and the electrode of Experimental Example 1 using glassy carbon powder in the electrolyte solution for lithium ion batteries in which LiBF ₄ was dissolved Similar to the measurement in the lithium ion battery electrolyte in which LiPF ₆ was dissolved, it was found to have a wide potential window.

(Measurement results in an electrolyte solution for lithium ion batteries in which LiTFSI is dissolved)
Furthermore, as shown in FIG. 5, it was found that the electrode of Experimental Example 1 using the glassy carbon powder had a wide potential window even in the measurement in the electrolyte solution for lithium ion batteries in which LiTFSI was dissolved. In addition, in the measurement results in the electrolyte solution for lithium ion batteries in which LiPF ₆ and LiBF ₄ are dissolved, both the glassy carbon and the diamond-like carbon have a wide potential window. Therefore, even in the case of TFSI, the diamond-like carbon has a wide potential window. Presumed.

  From the above results, in the case where the charge / discharge current is increased by mixing the catalyst metal-supporting carbon with the positive electrode material of the lithium ion battery, if the carbon is a glassy carbon powder or a diamond-like carbon powder, the lithium ion It can be seen that even in a positive electrode that is set to a high potential during battery charging, there is little possibility of decomposing the solvent without being decomposed. From this result, it can be seen that a positive electrode active material having a high energy density in which a charging reaction is performed at a high potential can be effectively utilized.

<Preparation of catalytic metal-supported carbon>
Catalytic metal supporting carbon used in the present invention, the conductive diamond-like carbon Powder, by applying the same metal loading procedure described in JP 2003-308849 Laid described above, be readily prepared it can. That is, first, prepared commercial conductive diamond-like carbon Powder, immersing them powder dinitrodiammineplatinum nitric acid solution of platinum concentration 2.2 wt%. And after fully stirring, 100% ethanol is added as a reducing agent. The solution is then refluxed for 6 hours with stirring, filtered and dried. Thus, it is possible to obtain a platinum-supported conductive diamond-like carbon emissions easily. Also, further, the supported platinum conductive diamond-like carbon emissions after immersion in ruthenium chloride solution 100 g, by performing the same operation, platinum and ruthenium supported is diamond-like carbon emissions were binary catalytic metal-supported carbon You can also get
( Reference Example 1)

Hereinafter, we described in Reference Example 1 embodying the medium metal-supported carbon catalyst.
In Reference Example 1, first, a glassy carbon powder pulverized by a pulverizer was prepared, and platinum was supported on the glassy carbon powder by the method described above. The platinum-supported glassy carbon powder (average particle size 0.5 μm) thus obtained and PTFE powder were mixed at a weight ratio of 80:20, and a disk-shaped electrode of 8 mmφ was produced by hot pressing.

<Measurement of potential-current curve>
The electrode of Reference Example 1 produced as described above was subjected to potential scanning in an electrolyte for a lithium ion battery, and a potential-current curve was measured. The electrolytic solution was prepared as follows. That is, a mixed solution was prepared such that ethylene carbonate, dimethyl carbonate, and sebaconitrile were in a volume ratio of 25:25:50, and a solution in which LiBF ₄ was dissolved to 1 mol / L was used as an electrolytic solution. Placed in an electrolytic cell container.

  The measurement of the potential-current curve is the same as the measurement in the experimental example and the comparative example, and the description is omitted.

As a result, as shown in FIG. 6, although the electrode of Reference Example 1 using platinum-supported glassy carbon powder had a slightly larger current than Experimental Example 1 using glassy carbon powder not supporting platinum, It had almost the same wide potential window.

From the above results, in the case where the charge / discharge current is increased by mixing the catalytic metal-supporting carbon with the positive electrode material of the lithium ion battery, if the carbon is made into a glassy carbon powder, the charge for the lithium ion battery can be reduced. It was found that the positive electrode having a high potential was not decomposed and there was little possibility of decomposing the solvent. From this result, it was found that a positive electrode active material having a high energy density in which a charging reaction is performed at a high potential can be effectively used.
(Example 1 )

In Example 1 , platinum was supported on diamond-like carbon powder, and this was applied to a fuel cell.
That is, a diamond-like carbon powder (average particle size 0.03 μm) was prepared, and platinum was supported on the diamond-like carbon powder by the method described in JP-A-2003-308849. That is, as a platinum solution, 30 g of diamond-like carbon powder was immersed in 900 g (platinum content: 20 g) of a dinitrodiammine platinum nitric acid solution having a platinum concentration of 2.2 wt%, and then 100 ml of 100% ethanol was added as a reducing agent. This solution was stirred and mixed at the boiling point (about 95 ° C.) for 6 hours, and platinum was supported on the carbon powder. Then, after filtration and drying, platinum-supported diamond-like carbon was obtained.
The platinum-supported diamond-like carbon thus obtained and a Nafion solution were mixed to form an air electrode. The hydrogen electrode was prepared by mixing ordinary platinum-supporting carbon and Nafion solution. A gas diffusion layer / a hydrogen electrode / a Nafion membrane / an air electrode / a gas diffusion layer were laminated in this order and hot-pressed to form a membrane-electrode assembly (MEA).

<Evaluation of fuel cell characteristics>
FIG. 7 shows battery characteristics when humidified hydrogen is introduced into the hydrogen electrode and humidified air is introduced into the air electrode. From this figure, it can be seen that diamond-like carbon can be used as a catalyst support for fuel cells. Since diamond-like carbon has a much wider potential window than carbon black and activated carbon, it has excellent durability against the potential shift phenomenon. It is naturally inferred from the technical common knowledge of those skilled in the art that the same effect can be obtained even when glassy carbon powder is used as a carrier instead of diamond-like carbon.

The catalytic metal-supported carbon used in the present invention is also applied to secondary batteries such as lithium ion batteries and sodium ion batteries. Here, a secondary battery such as a lithium ion battery or a sodium ion battery includes an electrolytic solution, a positive electrode, a negative electrode, a separator, and a case.

(Electrolytic solution for lithium ion battery)
The electrolytic solution for a lithium ion battery contains a Li salt (electrolyte) and an organic solvent.
As the Li salt, a general Li salt for a Li ion battery can be used. For example, LiPF ₆ (lithium hexafluorophosphate), LiBF ₄ (lithium tetrafluoroborate), LiTFSI (lithium bis (trifluoromethanesulfonyl) imide), LiTFS (lithium trifluoromethanesulfonate), LiBETI (lithium bis ( Pentafluoroethanesulfonyl) imide) or two or more thereof can be used.
Among them, for those redox potential of the positive electrode is more than 4.5V, it is preferable to use LiPF _6, and / or LiBF _4. In the case of using a LiTFSI and LiTFS and LiBETI, it is preferable to add LiPF ₆ or LiBF _4.

As the organic solvent, a general solvent used for a Li ion battery can be adopted. Such an organic solvent is preferably one or more selected from cyclic carbonates, cyclic carboxylic acid esters and chain carbonates. More preferably, a cyclic carbonate and a chain carbonate are used in combination. Specifically, it is particularly preferable to use ethylene carbonate and dimethyl carbonate in combination. The blending ratio of both is not particularly limited. As the cyclic carboxylic acid ester, γ-butyrolactone can be used.
Furthermore, a nitrile compound can be used as an organic solvent. Here, as the nitrile compound, a chain saturated hydrocarbon dinitrile compound in which a nitrile group is bonded to both ends of a chain saturated hydrocarbon compound, a chain ether in which a nitrile group is bonded to at least one terminal of a chain ether compound. Mention may be made of at least one nitrile compound among nitrile compounds and cyanoacetic acid esters.

Examples of the chain saturated hydrocarbon dinitrile compound in which nitrile groups are bonded to both ends of the chain saturated hydrocarbon compound include succinonitrile NC (CH ₂ ) ₂ CN, glutaronitrile NC (CH ₂ ) ₃ CN, adiponitrile In addition to linear dinitrile compounds such as NC (CH ₂ ) ₄ CN, sebaconitrile NC (CH ₂ ) ₈ CN, dodecanedinitrile NC (CH ₂ ) ₁₀ CN, 2-methylglutaronitrile NCCH (CH ₃ ) _CH 2 _CH 2 CN may have a branched as such. These chain saturated hydrocarbon dinitrile compounds are not particularly limited in carbon number, but are preferably 20 or less. More preferably, it is 7-12.

Examples of the chain ether nitrile compound in which a nitrile group is bonded to at least one end of the chain ether compound include oxydipropionitrile NCCH ₂ CH ₂ —O—CH ₂ CH ₂ CN and 3-methoxypropionitrile CH _{3. -O-CH} 2 CH 2 CN, and the like. These chain ether nitrile compounds are not particularly limited in carbon number, but are preferably 20 or less.
Examples of cyanoacetic acid esters include methyl cyanoacetate, ethyl cyanoacetate, propyl cyanoacetate, and butyl cyanoacetate. These cyanoacetic acid esters are not particularly limited in carbon number, but are preferably 20 or less.

These nitrile compounds have the effect of expanding the potential window particularly in the positive direction in the electrolytic solution.
A dinitrile compound is preferable from the viewpoint of the action of expanding the potential window. Of these, the use of sebacononitrile is more preferable.
However, since a nitrile compound has high viscosity, it is preferable to use together with the above-mentioned chain carbonate ester, cyclic carbonate ester, and / or cyclic carboxylic acid ester. More preferably, a nitrile compound, a chain carbonate ester and a cyclic carbonate ester are used in combination. Dimethyl carbonate can be employed as the chain carbonate, and ethylene carbonate can be employed as the cyclic carbonate.
In this case, the blending ratio of the nitrile compound in the whole organic solvent is preferably 1 to 90% by volume. More preferably, it is 5-70 volume%, More preferably, it is 10-50 volume%.

  Moreover, it is also preferable to add about 0.1 to 3% of various additives (for example, vinylene carbonate, fluoroethylene carbonate, ethylene sulfite). Thereby, a corrosion-resistant film is formed on the negative electrode side, and the corrosion resistance is improved.

The concentration of the Li salt is 0.01 mol / L or more and is lower than the saturated state. When the concentration of the Li salt is less than 0.01 mol / L, ion conduction by Li ions is reduced, and the electric resistance of the electrolytic solution is increased, which is not preferable. On the other hand, exceeding the saturation state is not preferable because the dissolved Li salt precipitates due to environmental changes such as temperature.

(Sodium ion battery electrolyte)
The electrolyte for sodium ion batteries contains Na salt (electrolyte) and an organic solvent.
As the Na salt, those conventionally known as Na salts for Na ion batteries can be used. For example, for example, NaClO ₄ , NaPF ₆ , NaBF ₄ , NaCF ₃ SO ₃ , NaN (CF ₃ SO ₂ ) ₂ , NaN (FSO ₂ ) ₂ , NaN (C ₂ F ₅ SO ₂ ) ₂ , NaC (CF ₃ SO ₂ ) ₃ etc. are mentioned. The mixing ratio of the solvent and the solute is not particularly limited and is appropriately set according to the purpose.
Moreover, it is also preferable to add about 0.1 to 3% of various additives (for example, vinylene carbonate, fluoroethylene carbonate, ethylene sulfite). Thereby, a corrosion-resistant film is formed on the negative electrode side, and the corrosion resistance is improved.

As the organic solvent, a general one used for a Na ion battery can be adopted. As such an organic solvent, one kind or two or more kinds selected from cyclic carbonates, cyclic carboxylic acid esters and chain carbonates are preferable. More preferably, a cyclic carbonate and a chain carbonate are used in combination. Specifically, it is particularly preferable to use ethylene carbonate and dimethyl carbonate in combination. The blending ratio of both is not particularly limited. As the cyclic carboxylic acid ester, γ-butyrolactone or propylene carbonate can be used.
As the chain carbonate, in addition to dimethyl carbonate, diethyl carbonate or ethyl methyl carbonate can be used.
Furthermore, a nitrile compound can be used as an organic solvent. Here, as the nitrile compound, a chain saturated hydrocarbon dinitrile compound in which a nitrile group is bonded to both ends of a chain saturated hydrocarbon compound, a chain ether in which a nitrile group is bonded to at least one terminal of a chain ether compound. Mention may be made of at least one nitrile compound among nitrile compounds and cyanoacetic acid esters.

Examples of the chain saturated hydrocarbon dinitrile compound in which nitrile groups are bonded to both ends of the chain saturated hydrocarbon compound include succinonitrile NC (CH ₂ ) ₂ CN, glutaronitrile NC (CH ₂ ) ₃ CN, adiponitrile In addition to linear dinitrile compounds such as NC (CH ₂ ) ₄ CN, sebaconitrile NC (CH ₂ ) ₈ CN, dodecanedinitrile NC (CH ₂ ) ₁₀ CN, 2-methylglutaronitrile NCCH (CH ₃ ) _CH 2 _CH 2 CN may have a branched as such. These chain saturated hydrocarbon dinitrile compounds are not particularly limited in carbon number, but are preferably 7 to 20. More preferably, it is 10-12.

Examples of the chain ether nitrile compound in which a nitrile group is bonded to at least one end of the chain ether compound include oxydipropionitrile NCCH ₂ CH ₂ —O—CH ₂ CH ₂ CN and 3-methoxypropionitrile CH _{3. -O-CH} 2 CH 2 CN, and the like. These chain ether nitrile compounds are not particularly limited in carbon number, but are preferably 20 or less.
Examples of cyanoacetic acid esters include methyl cyanoacetate, ethyl cyanoacetate, propyl cyanoacetate, and butyl cyanoacetate. These cyanoacetic acid esters are not particularly limited in carbon number, but are preferably 20 or less.

These nitrile compounds have the effect of expanding the potential window particularly in the positive direction in the electrolytic solution. A dinitrile compound is preferable from the viewpoint of the action of expanding the potential window. Of these, the use of sebacononitrile is more preferable.
However, since a nitrile compound has high viscosity, it is preferable to use together with the above-mentioned chain carbonate ester, cyclic carbonate ester, and / or cyclic carboxylic acid ester. More preferably, a nitrile compound, a chain carbonate ester and a cyclic carbonate ester are used in combination. Dimethyl carbonate can be employed as the chain carbonate, and ethylene carbonate can be employed as the cyclic carbonate.
In this case, the blending ratio of the nitrile compound in the whole organic solvent is preferably 1 to 90% by volume. More preferably, it is 15-70 volume%, More preferably, it is 30-50 volume%.

  The concentration of the Na salt is 0.01 mol / L or more and is lower than the saturated state. When the concentration of Na salt is less than 0.01 mol / L, ion conduction due to Na ions is reduced, and the electric resistance of the electrolytic solution is increased, which is not preferable. On the other hand, exceeding the saturated state is not preferable because a dissolved Na salt is precipitated due to environmental changes such as temperature.

(Positive electrode)
The positive electrode includes a positive electrode active material and a current collector.
(Positive electrode active material for lithium ion battery)
The positive electrode active material for a lithium ion battery refers to “a material in which lithium is inserted / extracted in the crystal structure at a higher potential than that of the negative electrode, and oxidation / reduction is performed accordingly”.
Examples of the positive electrode active material include (1) an oxide system, (2) a phosphate system having an olivine type crystal structure, and (3) an olivine fluoride system.

(1) Oxide-based 1-1 specific substances As oxide-based materials, Li _1-x CoO ₂ (x = 0 to 1: layered structure), Li _1-x NiO ₂ (x = 0 to ₁ : layered structure) ), Li _1-x Mn ₂ O ₄ (x = 0 to 1: spinel structure), Li _2−y MnO ₃ (y = 0 to 2) and their solid solutions (herein, solid solutions are those of the above oxide series) In the positive electrode active material, it refers to a material in which metal atoms are mixed in a free ratio. Moreover, what doped the metal atom of these with the other metal atom is also contained. The dopant is not particularly limited as long as the electrochemical characteristics can be changed in the oxidation-reduction reaction. For example, one or more of Li, Mg, Al, Ti, V, Mn, Fe, Co, Ni, Cu, Zn, Zr, Nb, and Mo can be used.
1-2 Characteristics The general discharge potential of this positive electrode active material is less than 5 V (vs Li / Li ⁺ ). However, LiNi _0.5 Mn _1.5 O ₄ partially substituted with Ni in the LiMn ₂ O ₄ system has a discharge potential of 4.7 V, and takes into account overvoltage when performing rapid charging, and 5 V May require a charging voltage exceeding. Further, since LiCoMnO ₄ starts with a discharge voltage of about 5.2V, the charge voltage also exceeds 5V. For this reason, the catalyst metal carrying | support carbon of this invention which can endure these high voltages can be used suitably. In addition, oxide systems generally decompose at less than 300 ° C., and have a relatively large exothermic reaction as oxygen is generated. Therefore, a control circuit that does not cause overcharging is required.

(2) Phosphate-based 2-1 having olivine-type crystal structure Specific substance Examples of phosphate-based olivine-type crystal structures include Li _1-x NiPO ₄ (x = 0 to ₁ ), Li _1-x CoPO ₄ (x = 0 to ₁ ), Li _1-x MnPO ₄ (x = 0 to ₁ ), Li _1-x FePO ₄ (x = 0 to 1) and their solid solutions (herein the solid solution is the above-mentioned phosphorus In the acid salt positive electrode active material, it refers to a material in which metal atoms are mixed in a free ratio. Moreover, what doped the metal atom of these with the other metal atom is also contained. The dopant is not particularly limited as long as the electrochemical characteristics can be changed in the oxidation-reduction reaction. For example, one or more of Mg, Al, Ti, V, Mn, Fe, Co, Ni, Cu, Zn, Zr, Nb, and Mo can be used (see JP 2008-130525 A).
2-2 Characteristics The oxidation-reduction potential of this positive electrode active material is attracting attention because, unlike the above oxide system, if it is less than 300 ° C., the exothermic reaction is small, oxygen is not generated, and safety is high. Of the phosphate systems, the LiCoPO ₄ system has a discharge potential of about 4.8 V, and an electrolyte having a withstand voltage of 5 V or more is required for rapid charging. It is suggested that the discharge potential of LiNiPO ₄ is 5.2 V (vs Li / Li ⁺ ). For this reason, the catalyst metal carrying | support carbon of this invention which can endure such a high voltage can be used suitably.

(3) Olivine fluoride system 3-1 Specific substances Li _2-x NiPO ₄ F (x = 0-2), Li _2-x CoPO ₄ F (x = 0-2) are known, and other Li _{2 -x MnPO 4 F (x = 0~2} ), Li 2-x FePO 4 F (x = 0~2) are considered.
Further, these solid solutions (herein, the solid solution refers to a material in which metal atoms are mixed in a free ratio in the olivine fluoride-based positive electrode active material) can also be mentioned. Furthermore, the thing which doped the metal atom of these with another metal atom is also contained. The dopant is not particularly limited as long as the electrochemical characteristics can be changed in the oxidation-reduction reaction. For example, one or more of Mg, Al, Ti, V, Mn, Fe, Co, Ni, Cu, Zn, Zr, Nb, and Mo can be used.
3-2 Characteristics Similar to the olivine system, the redox potential of this positive electrode active material is different from that of the above oxide system. The effect of battery ignition is considered to be small, and is attracting attention in terms of safety. Moreover, the electric capacity density (mAh / g) of a battery can be made higher than the said phosphate system (refer Unexamined-Japanese-Patent No. 2003-229126). However, for example, the Li ₂ CoPO ₄ F system has an average discharge potential of about 4.8 V, and an electrolytic solution having a withstand voltage of 5 V or more is required for rapid charging. Further, the discharge potential of the Li ₂ NiPO ₄ F system is about 5.2 V (vs Li / Li ⁺ ), and an electrolytic solution having a withstand voltage at 5 V or more is required. For this reason, the catalyst metal carrying | support carbon of this invention which can endure such a high voltage can be used suitably.

(4) Others In addition, lithium-free FeF ₃ , a conjugated polymer using an organic conductive material, a chevrel phase compound, or the like can also be used. In addition, transition metal chalcogenides, vanadium oxides and lithium salts thereof, niobium oxides and lithium salts thereof, and a plurality of different positive electrode active materials may be used in combination.
The average particle diameter of the positive electrode active material particles is not particularly limited, but is preferably 10 nm to 30 μm.

(Positive electrode active material for sodium ion batteries)
The positive electrode active material for a sodium ion battery is a material that can be reversibly oxidized and reduced by charge and discharge, and is required to be a material that can reversibly intercalate and deintercalate sodium ions. The
Examples of such a positive electrode active material include NaFeO ₂ , NaNiO ₂ , NaCoO ₂ , NaMnO ₂ , NaFe _1-x M ¹ _x O ₂ , and NaNi _1-x M ¹ _{x described in} JP2009-129741A. O ₂ , NaCo _1-x M ¹ _x O ₂ , NaMn _1-x M ¹ _x O ₂ (where M ¹ is one or more elements selected from the group consisting of trivalent metals, and 0 ≦ x <0 .5)) and the like. Among these, a composite oxide mainly containing iron and sodium, and using a composite oxide having a hexagonal crystal structure as a positive electrode active material, a high discharge voltage can be obtained. A secondary battery having a high density can be obtained.

More preferably, the positive electrode active material is a composite oxide mainly containing iron and sodium, has a hexagonal crystal structure, and has an interplanar spacing of 2 in the X-ray diffraction analysis of the composite oxide. A complex oxide having a value obtained by dividing the intensity of a peak of 20 angstroms by the intensity of a peak of 5.36 angstroms in plane spacing is 2 or less. In heating a metal compound mixture containing a sodium compound and an iron compound in a temperature range of 400 ° C. or more and 900 ° C. or less, the atmosphere is heated as an inert atmosphere in a temperature range of less than 100 ° C. during the temperature increase. Is preferred.
Moreover, what doped the transition metal atom of these compounds with the other metal atom may be used. The dopant is not particularly limited as long as the electrochemical characteristics can be changed in the oxidation-reduction reaction.

(Current collector for positive electrode)
The positive electrode current collector is a conductive substrate carrying a positive electrode active material.
The molding material for the current collector of the positive electrode is required to be stable during charging. In particular, when using a phosphate-based and olivine fluoride-based positive electrode active material having an olivine-type crystal structure with a high redox potential, it is preferable to use a material excellent in corrosion resistance.
For example, when LiPF ₆ or LiBF ₄ is used as the electrolyte, austenitic stainless steel, Ni, Al, Ti, or the like can be used, but it is preferable to select them appropriately in consideration of the operating potential of the positive electrode active material to be used. For example, when LiPF ₆ is used as the electrolyte, it can be used even at 6 V with respect to the Li / Li ⁺ electrode. However, when LiBF ₄ is used as the electrolyte, SUS304 is 5.8 V or less with respect to the Li / Li ⁺ electrode. It can be used only when charge / discharge is possible. Further, when LiTFSI is used as the electrolyte, it is preferable that LiPF ₆ coexists in order to form a corrosion-resistant film on the surface of the positive electrode current collector. LiBETI and LiTFS are the same as in LiTFSI.
In addition, a conductive metal material such as Al coated with conductive DLC (diamond-like carbon) by a well-known method can be used as a current collector. When the electrolyte is a lithium salt such as LiBF ₄ or LiPF ₆ that easily forms a fluoride film, a thick fluoride film is formed on the aluminum and the corrosion resistance is improved, but the electronic conductivity is lowered, and consequently The increase in output accompanying the increase in ohmic overvoltage is impeded. If the conductive metal material such as Al is coated with the conductive DLC, the fluoride film is generated only in a very small area of the defective portion of the conductive DLC. For this reason, even if the voltage is increased, the decrease in electron conductivity is negligible, and it is possible to prevent the decrease in output due to the increased voltage, which is a concern.
Here, the conductive diamond-like carbon is carbon having an amorphous structure in which both diamond bonds (SP ₃ hybrid orbital bonds between carbons) and graphite bonds (SP ₂ hybrid orbital bonds between carbons) are mixed. Among them, the conductivity is 1000 Ωcm or less. However, in addition to the amorphous structure, those having a phase composed of a crystal structure partially composed of a graphite structure (that is, a hexagonal crystal structure composed of SP ₂ hybrid orbital bonds) and thereby exhibiting conductivity are also included. . Diamond-like carbon having properties intermediate between graphite and diamond adjusts the conductivity by adjusting the ratio of SP ₂ hybrid orbital bonds and SP ₃ hybrid orbital bonds of the carbon atoms constituting diamond-like carbon during film formation. be able to.
Of course, you may coat | cover the said corrosion-resistant electroconductive metal material with electroconductive DLC.
The shape and structure of the current collector can be arbitrarily designed according to the structure of the positive electrode active material and the battery.

(Pretreatment of positive electrode)
The positive electrode for a lithium ion battery and the positive electrode for a sodium ion battery are incorporated into a pretreatment electrolyte in which a lithium salt (or sodium salt) is dissolved in an organic solvent containing 1% by volume or more of a nitrile compound before being incorporated into the lithium ion battery. An immersion treatment step of immersing the positive electrode is performed, and a positive voltage treatment step of applying a positive voltage to the electrode is further performed. The electrode thus pretreated has a wide potential window even when used in an electrolyte solution containing no nitrile compound or in a lithium ion battery using an electrolyte solution with a small amount of nitrile compound added. It becomes difficult to disassemble (see Japanese Patent Application No. 2009-180007). The reason why the electrode has such a wide potential window is presumed to be that a corrosion-resistant film containing nitrogen as a component is formed on the electrode.

(Negative electrode)
The negative electrode includes a negative electrode active material and a current collector.
(Anode active material for lithium ion battery)
The negative electrode active material for lithium ion batteries refers to “a material in which lithium is inserted / extracted in the crystal structure at a lower potential than that of the positive electrode, and oxidation / reduction is performed accordingly”.
Examples of the negative electrode active material for a lithium ion battery include various carbon materials such as artificial graphite, natural graphite, and hard carbon, lithium titanate (Li ₄ Ti ₅ O ₁₂ ), H ₂ Ti ₁₂ O ₂₅ , and H ₂ Ti _6. Examples thereof include O ₁₃ and Fe ₂ O ₃ . Moreover, the composite material which mixed these suitably can also be mentioned. Furthermore, there may be mentioned Si fine particles and Si thin films, and fine particles and thin films in which these Si are Si-based alloys such as Si—Ni, Si—Cu, Si—Nb, Si—Zn, Si—Sn. Further, SiO oxide, Si-SiO ₂ composite, Si-SiO ₂ - can be given complex, etc., such as carbon.

(Anode active material for sodium ion battery)
The negative electrode active material for a sodium ion battery is a “substance that allows sodium ions to enter and exit as a negative electrode of a secondary battery and reversibly repeat oxidation and reduction”. In the present invention, Li ₄ Ti ₅ O ₁₂ is used.

(Current collector for negative electrode)
The current collector for the negative electrode can be formed of a general-purpose conductive metal material, Cu, Al, Ni, Ti, austenitic stainless steel, or the like.
However, when a nitrile compound is used for the electrolytic solution (including combined use with other organic solvents), it is necessary to select appropriately according to the Li salt in the electrolytic solution. That is, when LiPF ₆ or LiBF ₄ is used as the electrolyte, austenitic stainless steel, Ni, Al, Ti, or the like can be used. However, it is necessary to select appropriately according to the operating potential of the negative electrode active material to be used. In the case of using carbon or Si as the negative electrode active material, when LiBF ₄ is used as the electrolyte, a current collector made of Al, Ni, Ti, austenitic stainless or the like other than Cu can be used. In the case where lithium titanate or a Fe ₂ O ₃ based compound is used as the negative electrode active material, all of the above materials containing Cu are applicable. On the other hand, when LiPF _{6 is} used as the electrolyte, Al, Ni and Ti are preferable, and austenitic stainless steel and Cu are not preferable. In addition, when LiTFSI, LiBETI, or LiTFS is used as the electrolyte, any of Ni, Ti, Al, Cu, and austenitic stainless steel can be used.

(Electroconductive member for positive electrode)
Some positive electrode active materials have low electrical conductivity. Therefore, it is preferable to provide a sufficient electron conduction path between the positive electrode active material and the current collector by interposing a conductive electron conduction member.
Here, the form of the electron conducting member is not particularly limited as long as an electron conducting path can be formed between the positive electrode active material and the current collector. For example, carbon black such as acetylene black, graphite powder, diamond-like carbon, glassy Conductive powder (conductive aid) such as carbon can be used. Diamond-like carbon and glassy carbon have a much wider potential window than carbon black and graphite, and are excellent in corrosion resistance when a high potential is applied, and therefore can be suitably used. Moreover, it is also preferable to use the catalyst metal carrying | support carbon of this invention as these conductive support agents. Examples of the metal fine particles include Pt, Au, Ni and the like. These may be used alone or an alloy thereof. In addition, as the electron conductive material, a conductive film (such as a DLC film) covering the positive electrode active material or a conductive thin film (such as a gold thin film) in which the positive electrode active material is embedded can be used.
In particular, since the Li ₂ NiPO ₄ F-based positive electrode active material has low conductivity of its own and / or its surface coating, it does not function as a positive electrode of a lithium ion battery if it is simply supported on a current collector. There is a case. In order to evaluate the performance of the Li ₂ NiPO ₄ F-based positive electrode active material, it can be physically driven into a conductive thin film such as gold with a hammer or the like to form the positive electrode of the battery.
Here, the Li ₂ NiPO ₄ F-based positive electrode active material refers to Li ₂ NiPO ₄ F and a material appropriately doped with dopant.

(Electroconductive member for negative electrode)
As the positive electrode electron conducting member, carbon black such as acetylene black can be used.

(Separator)
The separator is immersed in the electrolytic solution, separates the positive electrode and the negative electrode, prevents a short circuit therebetween, and allows the passage of Li ions.
Examples of such separators include porous films made of polyolefin resins such as polyethylene and polypropylene.

(Case)
The case is formed of a material having corrosion resistance against the electrolytic solution. The shape can be arbitrarily designed according to the intended use of the battery.
When using an electrolytic solution in which a lithium salt is dissolved, a base material made of austenitic stainless steel, a case made of Ti, Ni and / or Al can be used. However, there are cases where it is necessary to select appropriately depending on the operating potential of the positive electrode and negative electrode active material to be used.
When the case also serves as a current collector or is electrically coupled to the current collector, the case is formed of the same or the same material as the current collector forming material of each electrode.

  The present invention is not limited to the description of the embodiment of the invention. Various modifications may be included in the present invention as long as those skilled in the art can easily conceive without departing from the description of the scope of claims.

The catalytic metal-supported carbon used in the present invention can be used for a catalyst layer of a fuel cell, a positive electrode material of a lithium ion battery, and the like.

Claims (1)

A fuel cell comprising an air electrode formed by mixing a conductive diamond-like carbon powder carrying a catalyst metal and an electrolyte ,
The conductive diamond-like carbon is conductive among carbons having an amorphous structure in which both diamond bonds (SP ₃ hybrid orbital bonds between carbons) and graphite bonds (SP ₂ hybrid orbital bonds between carbons ) are mixed. In addition to the amorphous structure, it has a phase partially composed of a crystal structure composed of a graphite structure ( hexagonal crystal structure composed of SP ₂ hybrid orbital bonds). The fuel cell, including one that exhibits its properties .

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