JP5695062B2 - Electrode for ion secondary battery, method for producing electrode for ion secondary battery, lithium ion secondary battery, and magnesium ion secondary battery - Google Patents

Description

  The present invention relates to an electrode for an ion secondary battery, a method for producing an electrode for an ion secondary battery, a lithium ion secondary battery, and a magnesium ion secondary battery.

  Examples of the ion secondary battery include a plurality of types depending on the type of metal responsible for electrical conduction, such as a lithium ion secondary battery, a magnesium ion secondary battery, a sodium ion secondary battery, and a calcium ion secondary battery. Since these ion secondary batteries can be charged and stored, can be used repeatedly, and are highly convenient, they are used in a wide range of fields.

  Among the above, lithium ion secondary batteries have high voltage, capacity, and energy density, so in particular, mobile phones, laptop computers, storage batteries for power generation facilities such as wind power and solar power, electric vehicles, uninterruptible power supplies, and household storage batteries. It is used in many fields.

  In addition, among the above, magnesium ion secondary batteries can use a relatively inexpensive and large amount of magnesium in place of lithium, which is a rare metal, and can move two electrons. The discharge capacity is expected to be twice that of the lithium ion secondary battery. For this reason, the magnesium ion secondary battery is attracting attention as a next-generation ion secondary battery that replaces the lithium ion secondary battery, and research and development are currently underway.

  The structure of these ion secondary batteries will be schematically described. Graphite is disposed as a negative electrode, and a conductor capable of storing metal ions having a strong ionization tendency in an ionic state is disposed as a positive electrode. And the positive electrode are filled with an electrolytic solution or a gel electrolyte.

  In order to improve the performance of the ion secondary battery, further improvements are required for the electrodes such as the positive electrode and the negative electrode, the electrolyte, and other components not described above. , Techniques, etc. have been proposed.

  For example, an electrode, particularly a positive electrode, is conventionally applied to a surface of a current collector such as an aluminum foil by applying a mixture prepared by kneading an electrode active material, a conductive additive and an organic binder, and then drying. It was manufactured by press molding. In recent years, for example, the invention described in Patent Document 1 has been proposed in order to realize a positive electrode that maintains a high charge / discharge capacity even at a high charge / discharge rate and is excellent in charge / discharge cycle characteristics.

Patent Document 1 discloses a nano-sized microcrystalline oxide selected from TiO ₂ , NiO, MnO _{2 and the} like, and a glass phase selected from P ₂ O ₅ , SiO ₂ , B ₂ O _{3, and the} like. An electrode consisting of a size microcrystalline oxide-glass composite mesoporous powder or thin film is described.
Further, as a method for producing the powder or thin film, a block polymer or a surfactant is used as a template, and a metal alkoxide, a metal chloride, an aqueous solution of PO (OC ₂ H ₅ ) ₃ or an alcohol such as ethanol is used. A step of adding hydrochloric acid (HCl) to the dissolved solution, a step of producing a powder having a glass phase metal oxide-inorganic oxide composite mesostructure structure by a sol-gel method, and aging at room temperature to 90 ° C. for gelation A step of producing a glass phase metal oxide-glass phase composite mesoporous powder by removing the block polymer or the surfactant by heat treatment at 350-400 ° C. in the air, and further, 400-700 It describes that a glass phase metal oxide is subjected to a phase transition process to microcrystals by heat treatment at ℃.

Japanese Patent No. 4528975

However, the conventional method and the method described in Patent Document 1 have a problem that it is difficult to reduce the cost because the manufacturing process is complicated.
Moreover, since it is necessary to include an organic binder in the conventional method, there is a problem that the charge / discharge capacity is reduced accordingly.

  The present invention has been made to solve the above-mentioned problem, and is an ion secondary battery electrode capable of realizing low cost and high charge / discharge capacity, a method for producing an ion secondary battery electrode, a lithium ion secondary battery, and magnesium. It is an object to provide an ion secondary battery.

In order to solve the above-mentioned problems, the present invention provides an electrode for an ion secondary battery provided with a vanadium oxide film formed by spraying or fusing on the surface of a conductor , and the vanadium oxide film is non-crystallized. It was set as the electrode for ion secondary batteries characterized by including crystalline .
The present invention also provides an ion secondary battery electrode manufacturing method for manufacturing the above-mentioned ion secondary battery electrode, wherein a powdered thermal spray material containing vanadium oxide is sprayed on the surface of a conductor. It was set as the manufacturing method of the electrode for ion secondary batteries characterized by providing a vanadium oxide film.
Further, a lithium ion secondary battery or a magnesium ion secondary battery using the above-described electrode for an ion secondary battery was obtained.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the electrode for ion secondary batteries which can implement | achieve low cost and high charging / discharging capacity, the electrode for ion secondary batteries, a lithium ion secondary battery, and a magnesium ion secondary battery can be provided. .

It is sectional drawing explaining the structure of the electrode for ion secondary batteries which concerns on one Embodiment. FIG. 2 is a schematic configuration diagram of an apparatus (film forming apparatus) 201 that provides a vanadium oxide film 103 on the surface of the conductor 102 shown in FIG. 1. It is sectional drawing of the film | membrane surface part which formed the unevenness | corrugation in the surface simultaneously with crystallizing a part of vanadium oxide film | membrane 103 shown in FIG. FIG. 2 is an enlarged schematic cross-sectional view illustrating a state in which a part of the vanadium oxide film 103 illustrated in FIG. 1 is crystallized to include a crystal and an amorphous state. FIG. 4 is an enlarged schematic cross-sectional view illustrating a state in which a part of the vanadium oxide film 303 illustrated in FIG. 3 is crystallized and includes a crystal and an amorphous state. Is a conceptual diagram showing the crystal structure of the X _a V ₂ O ₅ crystal of monoclinic (0.26 ≦ a ≦ 0.59). X is at least one element selected from Cu, Ag, Fe, alkaline earth metal and alkali metal. It is a partial cross section figure which shows the structure of the ion secondary battery which concerns on one Embodiment. It is a schematic block diagram which shows schematic structure of the bipolar model cell used for the characteristic evaluation of the electrode for lithium ion secondary batteries. It is a schematic block diagram which shows schematic structure of the 3 pole type model cell used for the characteristic evaluation of the electrode for lithium ion secondary batteries. It is a schematic block diagram which shows schematic structure of the 3 pole type model cell used for the characteristic evaluation of the electrode for magnesium ion secondary batteries.

  DESCRIPTION OF EMBODIMENTS Hereinafter, an embodiment for carrying out an electrode for an ion secondary battery, a method for producing an electrode for an ion secondary battery, a lithium ion secondary battery, and a magnesium ion secondary battery according to the present invention will be described with reference to the drawings as appropriate. .

First, an ion secondary battery electrode according to an embodiment of the present invention will be described.
As shown in FIG. 1, an ion secondary battery electrode 101 according to an embodiment is provided with a vanadium oxide coating (hereinafter also simply referred to as “coating”) 103 on the surface of a conductor 102. Yes. The vanadium oxide film 103 contains vanadium oxide that is amorphous or vanadium oxide that is crystalline and amorphous.
Such an electrode 101 can be suitably used as a positive electrode of an ion secondary battery.

  When the electrode 101 is used as the positive electrode, the conductor 102 can be formed of at least one of aluminum, aluminum alloy, copper, copper alloy, and carbon conventionally used for the positive electrode. From the viewpoints of electronic conductivity and battery operating potential, aluminum or an aluminum alloy is preferable. The conductor 102 may be a foil or a plate, but is preferably in the form of a mesh from the viewpoint of achieving high adhesion to the coating 103 and reducing the weight. For example, the thickness of the foil is preferably 10 to 20 μm.

  Note that the electrode 101 can also be used as a negative electrode. When the electrode 101 is used as a negative electrode, the conductor 102 is preferably formed of metallic lithium or a lithium alloy if it is a lithium ion secondary battery, and is formed of metal magnesium or a magnesium alloy if it is a magnesium ion secondary battery. It is preferable to do this. In addition, when using for the negative electrode of these ion secondary batteries, if the lithium ion and the magnesium ion are pre-doped, the conductor 102 used for the negative electrode may be the same as the conductor 102 described for the positive electrode. it can. In this case, copper or an alloy thereof is preferable from the viewpoints of electronic conductivity and battery operating potential. For the same reason as described above, it is preferable that the conductor 102 has a mesh shape. For example, the thickness of the foil is preferably 10 to 20 μm. In addition, the pre dope in this invention means that a metal ion is previously contained in an electrode by an electrochemical means.

The vanadium oxide film 103 in the present invention has a low glass transition temperature, and can be directly provided on the surface of the conductor 102 by a technique such as thermal spraying, so that the manufacturing process can be greatly reduced as compared with the conventional case. Cost reduction can be achieved. Moreover, since it can provide directly by thermal spraying, it is not necessary to add organic binders, such as a polyvinylidene fluoride (PVDF), and this can also reduce cost.
Furthermore, since the coating 103 contains vanadium oxide, it is highly conductive and can act as an electrode active material. Therefore, it is necessary to add a conductive aid such as carbon black, graphite, or carbon fiber. There is no. Accordingly, not only can the cost be reduced by this, but also the vanadium oxide can be included in the amount not added with the organic binder or the conductive auxiliary agent, so that the charge / discharge capacity can be improved.
Vanadium oxide can be contained in the vanadium oxide coating 103 in a molar fraction of about 0.5 to 0.9, for example, about 0.703.

  The coating 103 is composed of vanadium (V), phosphorus (P), copper (Cu), silver (Ag), iron (Fe), alkaline earth metal (Group 2 element), and alkali metal (Group 1 element). It is preferable to contain at least one element selected from the inside.

  As described above, vanadium takes the form of an oxide in the vanadium oxide film 103. Although details will be described later, vanadium oxide has a unique crystal structure. Such a crystal structure has voids with a size from the atomic level to the molecular level, which enables insertion and removal of metal ions such as lithium ions and magnesium ions.

Phosphorus forms an oxide and has a function of making the glass phase of the vanadium oxide film 103 stable and strong. Examples of the phosphorus oxide in the vanadium oxide film 103 include a PO ₄ tetrahedron. Phosphorus can be contained in the vanadium oxide coating 103 in terms of the raw material P ₂ O ₅ in a molar fraction of about 0.05 to 0.20, for example, about 0.09. In the present invention, glass means a solid having a network structure with random atomic arrangement and exhibiting a glass transition phenomenon.

At least one element selected from copper, silver, alkaline earth metal and alkali metal functions as a nucleating agent when crystallized. Thereby, the orientation and crystal structure of the vanadium oxide film 103 can be optimized, the insertion and desorption of ions are facilitated, the deterioration of the crystal structure accompanying the charge / discharge cycle is reduced, and the charge / discharge capacity retention rate Is improved. Here, examples of the alkaline earth metal include beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), and barium (Ba). Examples of the alkali metal include lithium (Li), sodium (Na), potassium (K), rubidium (Rb), and cesium (Cs). These elements can also be contained in the vanadium oxide film 103 in the state of oxides similarly to phosphorus. The total amount of these elements can be contained in the vanadium oxide film 103 in a molar fraction of about 0.06 to 0.29, for example, about 0.107 for Li ₂ O.

In addition to these, glass modifying components such as WO ₃ , MoO ₃ , Fe ₂ O ₃ , MnO ₂ , BaO, Sb ₂ O ₃ and Bi ₂ O ₃ may be added as appropriate. By adding these components, the characteristics of the glass amorphous phase, such as water resistance, thermal expansion, and characteristic temperature can be adjusted.

  The vanadium oxide coating 103 according to the present invention is prepared by crushing a glass block manufactured using the above-described material to prepare a powdered thermal spray material containing vanadium oxide, and then using the material, the surface of the conductor 102 It can be manufactured by thermal spraying. For example, the powder spray material may have an average particle diameter of about 10 μm.

  The glass block is mixed with elements such as vanadium oxide and phosphorus within the range of the molar fractions described above, and the resulting mixed powder is placed in a container such as a platinum crucible and melted in a melting furnace such as an electric furnace. It can be manufactured by casting into a graphite mold or the like. The melting conditions in the melting furnace may be, for example, a temperature rising rate of 5 ° C./min, a target temperature of 1000 to 1100 ° C., and after maintaining the target temperature for 1 hour while stirring. The graphite mold is preferably preheated to 150 to 300 ° C. before casting molten glass.

  In thermal spraying, a thermal spray material is heated using a combustion flame or electric energy to make the thermal spray particles melt or close to the thermal spray material and sprayed onto the surface of the thermal spray target to form a film. In the present invention for forming the coating 103, powdered glass (glass powder) serving as a thermal spray material is heated to a temperature equal to or higher than the glass transition temperature of the glass powder and sprayed. Thermal spraying includes atmospheric pressure plasma spraying, low pressure plasma spraying, flame spraying, high-speed flame spraying, arc spraying, cold spraying, etc., but any method is applicable in the present invention.

FIG. 2 shows a schematic configuration diagram of an apparatus (coating film forming apparatus 201) for providing the vanadium oxide film 103 on the surface of the conductor 102 by flame spraying as an example of thermal spraying.
As shown in FIG. 2, the coating film forming apparatus 201 includes a gas supply apparatus 202, a gas supply pipe 203, a gas heater 204, a working gas supply pipe 205, a spray nozzle 206, and a glass powder supply apparatus 207. And a glass powder supply pipe 208.

  The high-pressure gas supplied from the gas supply device 202 passes through the gas supply pipe 203 branched into two paths, and the gas that has passed through one path is supplied to the gas heater 204. The gas heated by the gas heater 204 is supplied to the spray nozzle 206 through the working gas supply pipe 205. The gas passing through the other path is supplied to the glass powder supply device 207, and is supplied to the spray nozzle 206 through the glass powder supply pipe 208 together with the glass powder as the working gas. The working gas and the glass powder supplied to the spray nozzle 206 are ejected from the tip of the spray nozzle 206 toward the surface of the conductor 102 in a state of being melted or close to it, thereby forming the coating 103.

  Here, as the gas supplied from the gas supply device 202, for example, air can be used. When air is used as the gas, the supply pressure can be set to 0.5 MPa, for example, and the temperature can be set to a temperature higher than the softening point of the glass powder (for example, 300 ° C.). Moreover, the supply speed | rate of glass powder can be 10 g / min etc., for example. In addition, when providing the vanadium oxide film 103 on the surface of the conductor 102, it is preferable to carry out while heating the conductor 102, and the temperature can be 150 degreeC etc., for example.

  As another embodiment in which the vanadium oxide film 103 is provided on the surface of the conductor 102, for example, the glass powder produced as described above is applied in the form of a paste on the surface of the conductor 102, and a predetermined temperature described later is applied. It can also be obtained by heating with. Here, the paste-like glass powder (glass powder paste) can be prepared, for example, by mixing glass powder, ethyl cellulose as a binder, and butyl carbitol acetate as a solvent. And after apply | coating the glass powder paste prepared in this way to the surface of the conductor 102 by the screen printing method, the spray coat method, etc. (application method), it heats at about 150 degreeC and removes butyl carbitol acetate. Then, by heating to 330 ° C. or higher and above the softening point of glass to remove ethyl cellulose and fusing the glass powder, the vanadium oxide film 103 in the present invention can be formed on the surface of the conductor 102. .

In the spraying or coating method, when glass powder that is relatively easy to crystallize is used, a vanadium oxide glass powder that is difficult to crystallize and has a low softening point temperature is 5% by volume with respect to the former glass powder. When about 20% is added, the film 103 is more easily formed. As the glass powder to be added, for example, a V-Te-P-Fe-O-based glass powder having a softening point of 356 ° C (the molar fraction of the glass powder is V ₂ O ₅ : Te ₂ O: P ₂ O ₅ : Fe ₂ O ₃ = 0.430: 0.313: 0.153: 0.104) is preferred.

  As shown in FIG. 1, the surface of the vanadium oxide film 103 formed by thermal spraying on the surface of the conductor 102 is substantially flat. However, as shown in FIG. It can also be. When unevenness is provided on the surface like the coating 303, the specific surface area is increased and the reactivity with the electrolytic solution is improved. Therefore, the ion secondary battery electrode 301 provided with the coating 303 can improve the charge / discharge capacity and the charge / discharge rate. The unevenness is formed by, for example, forming a flat film on the surface of the conductor 302 and then heating the stamper with the unevenness on the surface of the flat film while heating at a temperature equal to or higher than the softening point of the film. can do. Heating can be performed in a microwave heating furnace or an electric furnace. The irregularities need not be regular, and similar effects can be obtained even with irregular irregularities such as cracks. When heating by a microwave heating furnace, the stamper is preferably made of quartz glass that does not absorb microwaves, and when heated by an electric furnace, nickel or stainless steel is preferable.

  The vanadium oxide coating 103 (also coating 303) provided by spraying on the surface of the conductor 102 (same for the conductor 302) is flat although the entire coating 103 is in an amorphous state. Some of them and those with irregularities can be crystallized partially to contain crystals and amorphous. 4 is a cross-sectional schematic enlarged view showing a state in which a part of the vanadium oxide film 103 shown in FIG. 1 is crystallized to include a crystal 401 and an amorphous 402, and FIG. FIG. 4 is an enlarged schematic cross-sectional view showing a state in which a part of the vanadium oxide film 303 shown in FIG. 3 is crystallized to include a crystal 501 and an amorphous 502.

  When the volume fraction of amorphous 402 (same for amorphous 502) in the vanadium oxide film 103 increases, the atomic spacing in amorphous 402 is wider than that of crystal 401 (same for crystal 501). Ion desorption / insertion during discharge is facilitated, and cycle deterioration is reduced. Therefore, although a charge / discharge capacity maintenance rate can be improved, on the other hand, charge / discharge capacity falls.

  On the other hand, when the volume fraction of the crystal 401 with respect to the amorphous 402 in the vanadium oxide coating 103 increases, the charge / discharge capacity can be improved, but on the other hand, the charge / discharge capacity maintenance ratio decreases.

  Whether the entire film 103 remains amorphous 402 or includes the crystal 401 and the amorphous 402 depends on the charge / discharge capacity maintenance rate of the ion secondary battery, It can be appropriately determined according to the purpose whether to place importance on or to place importance on these balances. For example, when a long life is required, such as an ion storage battery for power storage, in order to improve the charge / discharge capacity maintenance rate, a completely amorphous phase is not required without passing through a crystallization step. An ion secondary battery may be constituted by the vanadium oxide film 103 as it is.

  When the vanadium oxide film 103 includes the crystal 401 and the amorphous 402, the volume fraction of the crystal 401 with respect to the amorphous 402 in the film 103 is preferably 94% or less. When the volume fraction exceeds 94%, the volume fraction of the crystal 401 with respect to the amorphous 402 in the coating 103 is too high, and the charge / discharge capacity retention rate may be reduced.

The main crystal 401 in the vanadium oxide film 103 is preferably monoclinic. That is, it is preferable that the crystal occupying the most in the crystal lattice that the vanadium oxide film 103 can take is a monoclinic crystal. FIG. 6 is a conceptual diagram showing the crystal structure of a monoclinic X _a V ₂ O ₅ crystal (0.26 ≦ a ≦ 0.59). X is at least one element selected from Cu, Ag, Fe, alkaline earth metal and alkali metal. In the figure, O atom represents an oxygen atom, V atom represents a vanadium atom, and X atom represents at least one element selected from the selected group.

As shown in FIG. 6, the X _a V ₂ O ₅ crystal is composed of double-chain VO ₆ octahedrons 601 arranged in the b-axis direction. This double chain is also connected in the a-axis direction and the c-axis direction, and forms a three-dimensional tunnel structure. The tunnel gap along the a-axis direction is the widest, and reversible ions are inserted into the tunnel. The insertion of ions into the tunnel is easier when the crystal 401 of the coating 103 is oriented, especially when the [100] crystal orientation is oriented perpendicular to the surface of the conductor 102. Easy to do. That is, when the crystal orientation of the crystal 401 is oriented in this way with respect to the surface of the conductor 102, a tunnel along the a-axis direction is formed so as to be parallel to the thickness direction of the conductor 102. Therefore, the insertion and desorption of ions is facilitated, the deterioration of the crystal structure accompanying the charge / discharge cycle is reduced, and the charge / discharge capacity retention rate can be improved. In addition, since cations (that is, X) are regularly bonded to each other, the layers composed of the double-chain VO ₆ octahedron 601 are associated with tunnel expansion and contraction due to ion insertion and desorption. Peeling between layers is suppressed. Thereby, the deterioration of the crystal structure accompanying the charge / discharge cycle can be reduced, and the charge / discharge capacity retention rate can be improved.

Such crystallization of the vanadium oxide film 103 can be performed by heating in an electric furnace, but is more preferably performed in a microwave heating furnace from the viewpoint of the degree of orientation of precipitated crystals and shortening of the heating time. The heating by the microwave can be performed by, for example, irradiating the microwave with the frequency of 2.45 GHz while controlling the appropriate time and output. Note that at the time of heating by the microwave, the temperature of the coating 103 is measured by a radiation thermometer or the like so that the temperature of the coating 103 is equal to or higher than the crystallization temperature of glass (for example, about 370 ° C.). If the heating temperature is lower than the crystallization temperature, it cannot be crystallized.
For example, a vanadium oxide film formed using a molar fraction of V ₂ O ₅ of 0.703, Li ₂ O of 0.107, Fe ₂ O ₃ of 0.1, and P ₂ O ₅ of 0.09 When the above-described treatment is performed on the film 103 and an X-ray diffraction analysis is performed on the coating film 103, precipitation of monoclinic Li _0.3 V ₂ O ₅ oriented in [100] can be confirmed. Further, the volume fraction of the crystal 401 with respect to the amorphous 402 is about 90%.

  Here, when the unevenness is formed on the surface of the film 103 as described above, the crystallization of the vanadium oxide film 103 and the formation of the unevenness can be performed simultaneously. Furthermore, in the present invention, the ratio of the amorphous 402 in the surface layer portion of the vanadium oxide coating 103 can be made higher than the inside. This is more preferable because it facilitates ion insertion and removal.

  The vanadium oxide film 103 can be pre-doped with metal ions such as lithium ions and magnesium ions in advance. These ions only need to be suitable for the ion secondary battery to be manufactured. For example, lithium ions may be pre-doped with lithium ions, and magnesium ions may be pre-doped with magnesium ions.

The pre-doping of metal ions can be performed by an electrochemical method. For example, in the case of an ion secondary battery electrode 101 in which a vanadium oxide film 103 is provided on the surface of an aluminum alloy foil used as the conductor 102, the electrode 101 is used as a cathode, and a metal to be predoped such as lithium or magnesium is used as an anode. These can be pre-doped by immersing them in a non-aqueous electrolyte and applying a voltage between the two electrodes. As an electrolytic solution in this case, for example, 1 mol / L of lithium hexafluorophosphate (LiPF ₆ ) is added to a solvent in which ethylene carbonate (EC) and ethyl methyl carbonate (EMC) are mixed at a volume ratio of 1: 2. What was dissolved can be used. Examples of other solvents that can be used for pre-doping include ionic liquids. The applied voltage can be 3 V, for example, and the application time can be 1 hour, for example.

For example, as another embodiment in the case of pre-doping with lithium ions, lithium salts such as lithium chloride (LiCl) and lithium acetate (AcOLi), or butyl lithium (C ₄ H ₉ Li) and naphthalene lithium (C ₁₀ H) ₈ Li) and the like, and a method of immersing the electrode for ion secondary battery 101 in a mixed solution of an organic lithium compound such as Li) and an organic solvent. At this time, ultrasonic wave irradiation, microwave irradiation, or the like is performed in a state where the film 103 is immersed, or a noble metal anode electrode is provided, and a voltage is applied between the anode electrode and the ion secondary battery electrode 101. Thereby, the amount of pre-doping and the efficiency of pre-doping can be improved.

For example, as another embodiment in the case of pre-doping lithium ions, for example, a molten salt containing lithium such as lithium nitrate (LiNO ₃ ) that melts below the melting point of the aluminum alloy foil used as the conductor 102, It is heated to a temperature not lower than the melting point of the aluminum alloy foil and a temperature between the glass transition point and the softening point of the coating 103, and the ion secondary battery electrode 101 is immersed in this, or in the same manner as described above, a noble metal anode electrode is further provided. It can also be pre-doped by applying a voltage between the anode electrode and the ion secondary battery electrode 101.

An electrode for an ion secondary battery 101 according to an embodiment of the present invention is provided with a vanadium oxide film 103 on the surface of a conductor 102. Since the coating 103 does not contain an organic binder, the charge / discharge capacity can be improved accordingly. Further, when the coating 103 is formed by thermal spraying, the manufacturing process can be greatly reduced, and the cost can be reduced. Further, when the coating 103 is made of amorphous 402, the charge / discharge capacity retention ratio can be improved, and when the film 103 includes the crystal 401 and the amorphous 402, a high charge / discharge capacity and charging / discharging capacity are achieved. It is possible to achieve both discharge capacity maintenance rates.
Heretofore, the ion secondary battery electrode 101 according to an embodiment of the present invention has been described in detail.

Next, an ion secondary battery according to an embodiment of the present invention using the above-described ion secondary battery electrode 101 will be described.
Examples of the ion secondary battery include a lithium ion secondary battery using lithium and a magnesium ion secondary battery using magnesium. Since these can be implemented with the same structure, in the following description, a lithium ion secondary battery will be described as a representative.

  As shown in FIG. 7, the lithium ion secondary battery 701 is in contact with the positive electrode 702 and the positive electrode 702 when the ion secondary battery electrode 101 (not shown in FIG. 7) is used as the positive electrode 702. A positive electrode current collector 703 that collects electricity, a negative electrode 704 that is a counter electrode of the positive electrode 702, a negative electrode current collector 705 that contacts the negative electrode 704 and collects electricity, a positive electrode 702, a negative electrode 704, and a container 706 And a separator 708 that can be impregnated with the electrolytic solution 707 are liquid-tightly configured in the container 706. Note that conductive carbon (not shown) may be attached to the negative electrode 704 by coating or the like.

  The positive electrode current collector 703 can be formed of an aluminum alloy foil or the like, the negative electrode current collector 705 can be formed of a copper alloy foil or the like, and the separator 708 is a laminated layer of polyethylene and polypropylene having a microporous structure. It can be formed of a film or the like. The container 706 may be formed of, for example, stainless steel or aluminum alloy in a bottomed cylindrical shape or a bottomed rectangular tube shape and can be hermetically sealed by the lid 709 and the gasket 710.

In the case of a lithium ion secondary battery, the electrolytic solution 707 is, for example, lithium hexafluorophosphate (LiPF ₆ ) in a solvent in which ethylene carbonate (EC) and ethyl methyl carbonate (EMC) are mixed at a volume ratio of 1: 2. In which 1 mol / L is dissolved and 0.8% by mass of vinylene carbonate (VC) is further added. On the other hand, in the case of a magnesium ion secondary battery, for example, a PC solution of 0.4 mol% / L Mg (ClO ₄ ) ₂ and 0.1 mol% / L NaClO ₄ can be used.

Note that the positive electrode current collector 703, the negative electrode 704, the negative electrode current collector 705, the container 706, the electrolytic solution 707, the separator 708, the lid 709, and the gasket 710 are not limited to the above-described ones. It can be embodied by a known material used for an ion secondary battery such as a battery or a magnesium ion secondary battery.
For example, the negative electrode of the magnesium ion secondary battery can be formed of an AZ31 alloy (a magnesium alloy to which 3% aluminum and 1% zinc are added) or the like.

The lithium ion secondary battery having such a configuration can achieve, for example, an initial charge / discharge capacity of 345 mAh / g, a charge / discharge capacity after 51 cycles of 331 mAh / g, and a charge / discharge capacity maintenance ratio of after 51 cycles of 96%. it can.
The magnesium ion secondary battery having such a configuration achieves, for example, an initial charge / discharge capacity of 300 mAh / g, a charge / discharge capacity after 10 cycles of 285 mAh / g, and a charge / discharge capacity maintenance ratio after 10 cycles of 95%. be able to.

  Next, examples in which the effects of the present invention have been confirmed will be described.

[1] Manufacture of glass powder First, glass powder used as a thermal spray material was manufactured. In a platinum crucible, V ₂ O ₅ , Li ₂ O, Fe ₂ O ₃ , and P ₂ O ₅ are blended so that the molar fractions are 0.703, 0.107, 0.100, and 0.090, respectively. And mixed to prepare 200 g of mixed powder.
And this was heated with the electric furnace. The heating in the electric furnace was performed while maintaining the glass with stirring for 1 hour from the time when the target temperature (1000 to 1100 ° C.) was reached at a heating rate of 5 ° C./min.
Thereafter, the platinum crucible was taken out from the melting furnace and cast into a graphite mold that had been heated and held in advance at 150 to 300 ° C. to produce a glass block, which was pulverized. The average particle size of the crushed glass powder was 10 μm.
As a result of measuring the characteristic points of the glass powder by differential thermal analysis (DTA), the glass transition point (Tg) was 252 ° C., the yield point (Mg) was 271 ° C., the first crystallization start temperature was 315 ° C., and the second The crystallization start temperature was 428 ° C.

[2] Vanadium Oxide Film Formation Next, a vanadium oxide film was formed on the surface of the conductor using the glass powder produced in [1]. The film was formed by flame spraying. The flame spraying was performed using a coating film forming apparatus (see FIG. 2). As the conductor, an aluminum alloy foil (N5-8X-073 manufactured by Mitsubishi Aluminum Co., Ltd.) having a thickness of 20 μm was used. The thermal spraying conditions were as follows, and the average thickness of the vanadium oxide film formed was about 10 μm.

《Spraying conditions》
・ Distance from tip of spray nozzle to aluminum alloy foil: approx. 15mm
・ Working gas: Air ・ Working gas supply pressure: 0.5 MPa
・ Working gas supply temperature: 300 ℃
・ Glass powder feed rate: 10 g / min ・ Aluminum alloy foil heating temperature: 150 ° C.

[3] Crystallization of vanadium oxide film Next, the vanadium oxide film formed on the surface of the conductor in [2] was crystallized. The vanadium oxide coating was crystallized using a microwave heating furnace. As the microwave heating furnace, a microwave reactor μ reactor (microwave frequency: 2.45 GHz) manufactured by Shikoku Keiki Kogyo Co., Ltd. was used. In the heating by the microwave, the temperature of the coating was measured with a radiation thermometer, and the output of the microwave and the irradiation time were controlled so that the temperature of the coating was about 370 ° C. In this study, it was about 10 min at 1000 W.
After the film was irradiated with microwaves and heated, the surface of the film was subjected to X-ray diffraction analysis. As a result, monoclinic Li _0.3 V ₂ O ₅ oriented in [100] was precipitated and amorphous The volume fraction of crystals relative to quality was found to be 90%.

[4] Pre-doping of lithium ions into vanadium oxide film Next, lithium ions were pre-doped into the vanadium oxide film crystallized in [3]. The lithium ion pre-doping was performed by an electrochemical method. First, a conductor provided with a coating was used as a cathode, metallic lithium was used as an anode, and these were immersed in a non-aqueous electrolyte and applied between both electrodes at a voltage of 3 V for 1 hour to pre-dope lithium ions into the coating. The electrolyte used was a solution in which 1 mol / L of lithium hexafluorophosphate (LiPF ₆ ) was dissolved in a solvent in which ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were mixed at a volume ratio of 1: 2. It was.

[5] Characteristic Evaluation of Electrode for Lithium Ion Secondary Battery In [4], a conductor obtained by pre-doping lithium ions on a vanadium oxide film was punched into a disk shape having a diameter of 15 mm to produce an electrode according to Example 1. The manufactured electrode according to Example 1 was used as a positive electrode (shown as a positive electrode 801 in FIG. 8), and charge / discharge characteristics were evaluated by a bipolar model cell.

FIG. 8 shows a schematic configuration of a bipolar model cell used for evaluating the characteristics of an electrode for a lithium ion secondary battery. As shown in FIG. 8, a positive electrode 801 and an aluminum current collector foil 802, and a negative electrode 803 and a copper current collector foil 804 obtained by applying PIC (Pseudo Isotoropic Carbon) to a copper foil are impregnated with an electrolytic solution. After laminating via the separator 805 and sandwiching them with two SUS jigs 806, they were put in a glass container to form a battery cell. The electrolytic solution used was prepared by dissolving 1 mol / L of lithium hexafluorophosphate (LiPF ₆ ) in a solvent in which ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were mixed at a volume ratio of 1: 2, and further 0.8 What added the mass% vinylene carbonate (VC) was used.

The charge / discharge evaluation was performed at room temperature using a charge / discharge tester (TOSCAT3100U manufactured by Toyo System Co., Ltd.), and started from charging. Charging / discharging was performed in CC (Constant Current) mode, and the cell voltage was set to 1.5 to 4.2V. The current density during charging and discharging, the first time a 0.057mA / cm ^2, the second and subsequent cycles was 0.28mA / cm ^2.

  On the other hand, an electrode for comparison with the electrode according to Example 1 was manufactured by a conventional method. Such an electrode is composed of the glass powder produced in [1], Ketjen Black (Lion Co., Ltd. EC600JD, particle size: 34.0 nm or less) as a conductive additive, and N-methyl-2-pyrodoline (as a binder). Polyvinylidene fluoride (PVDF) (# 7305 manufactured by Kureha Co., Ltd.) dissolved in 5% by mass in NMP) was mixed using a mortar at a mass ratio of 85: 5: 10. At this time, in order to adjust the viscosity, the slurry was slurried while appropriately mixing NMP. The obtained slurry was applied onto a 20 μm thick aluminum alloy foil (N5-8X-073 manufactured by Mitsubishi Aluminum Co., Ltd.) using a blade coater with a gap of 200 μm. This was dried in air at 90 ° C. × 2 hr, and then punched out into a disk shape having a diameter of 15 mm. Next, after pressing at about 400 MPa, the electrode according to Comparative Example 1 was manufactured by vacuum drying at 120 ° C. for 1 hour. Then, the manufactured electrode according to Comparative Example 1 was used as a positive electrode (shown as a positive electrode 901 in FIG. 9), and charge / discharge characteristics were evaluated by a tripolar model cell.

FIG. 9 shows a schematic configuration of a three-pole model cell used for evaluating the characteristics of the lithium ion secondary battery electrode. As shown in FIG. 9, a positive electrode 901 and an aluminum current collector foil 902, a negative electrode Li plate 903, and a reference electrode Li plate 904 are laminated via a separator 905 having a thickness of 30 μm impregnated with an electrolytic solution, These were sandwiched between two SUS jigs 906 and then placed in a glass container to form a battery cell. The electrolyte used was a solution in which 1 mol / L of lithium hexafluorophosphate (LiPF ₆ ) was dissolved in a solvent in which ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were mixed at a volume ratio of 1: 2. .

The charge / discharge evaluation was performed at room temperature using the same apparatus as described above. Charging / discharging was performed in CC (Constant Current) mode, the cell voltage was set to 1.5 to 4.2 V, and the discharge was started. Current density during charging and discharging, the first time a 0.057mA / cm ^2, the second and subsequent cycles was 0.28mA / cm ^2. In addition, the charging / discharging capacity | capacitance of the positive electrode was taken as the value which remove | divided the obtained charging / discharging capacity | capacitance by the mixture mass which consists of glass powder, a conductive support agent, and a binder.

The following was confirmed as an evaluation of the charge / discharge characteristics.
The electrode (positive electrode) according to Example 1 had an improved charge / discharge capacity and an improved charge / discharge capacity retention rate after 51 cycles as compared with the electrode (positive electrode) according to Comparative Example 1.
Specifically, in the lithium ion secondary battery using the electrode according to Comparative Example 1 as the positive electrode, the initial charge / discharge capacity was 320 mAh / g, and the charge / discharge capacity after 51 cycles was 260 mAh / g. That is, the charge / discharge capacity retention ratio after 51 cycles was 81%.
On the other hand, in the lithium ion secondary battery using the electrode according to Example 1 as the positive electrode, the initial charge / discharge capacity was 345 mAh / g, and the charge / discharge capacity after 51 cycles was 331 mAh / g. That is, the charge / discharge capacity retention ratio after 51 cycles was 96%.

  In addition, after implementing [1] and [2] under the same conditions, the condition of [3], in particular, by changing the microwave irradiation time between 0 to 15 minutes, As shown in Table 1, the volume fraction of the crystals was varied between 0 and 100%. Electrodes according to 1 to 6 were produced. In Table 1 below, no. The electrode according to No. 3 is the same as the electrode according to Example 1 described above. No. The respective electrodes according to 1, 2, 4, and 5 were processed under the same conditions as in [4], and the charge / discharge characteristics were evaluated by the bipolar model cell described in [5]. Table 1 shows the volume fraction (%) of the crystal relative to the amorphous for each electrode, the initial charge / discharge capacity (mAh / g), and the charge / discharge capacity retention ratio (%) after 51 cycles.

As shown in Table 1, No. 1 in which the volume fraction of crystals relative to amorphous was 0%. Although the initial charge / discharge capacity was slightly lower than that of the other electrodes, the electrode according to 1 maintained a charge / discharge capacity retention rate of 51% after 51 cycles and was extremely excellent. Therefore, it is strongly suggested that the volume fraction of the crystal with respect to the amorphous is 0%, that is, if the vanadium oxide film is amorphous, it is suitable for providing a long-life lithium ion secondary battery. It was.
No. 1 in which the volume fraction of crystals relative to amorphous was 94%. The electrode according to No. 4 has a high initial charge capacity and a relatively good charge / discharge capacity retention rate after 51 cycles, suggesting that it is suitable for providing a high charge / discharge capacity lithium ion secondary battery. It was.
On the other hand, the volume fraction of crystals with respect to amorphous exceeded 94%. In the electrodes according to 5 and 6, neither the initial charge / discharge capacity nor the charge / discharge capacity retention ratio after 51 cycles was satisfactory.

[6] Characteristic Evaluation of Magnesium Ion Secondary Battery Electrode Next, a vanadium oxide film is formed on the surface of the aluminum alloy foil under the same conditions as described in [1] to [3]. Without pre-doping, as described in [5], the electrode according to Example 2 was manufactured by punching into a disk shape having a diameter of 15 mm. Using this as a positive electrode (shown in FIG. 10 as a positive electrode 1001), the charge / discharge characteristics were evaluated by a three-pole model cell.

FIG. 10 shows a schematic configuration of a three-pole model cell used for evaluating the characteristics of the magnesium ion secondary battery electrode. As shown in FIG. 10, a positive electrode 1001, an aluminum current collector foil 1002, a magnesium alloy (AZ31 alloy) negative electrode 1003, and a reference electrode magnesium alloy (AZ31 alloy) plate 1004 having a thickness of 30 μm impregnated with an electrolytic solution. After laminating through the separator 1005, these were sandwiched between two SUS jigs 1006, and then put into a glass container to form a battery cell. The electrolytic solution used was a PC solution containing 0.4 mol% / L Mg (ClO ₄ ) ₂ and 0.1 mol% / L NaClO ₄ .

The charge / discharge evaluation was performed at room temperature using a charge / discharge tester (TOSCAT3100U manufactured by Toyo System Co., Ltd.) as described above, and started from charging. Charging / discharging was performed in CC (Constant Current) mode, and the cell voltage was set to 0.5 to 3.0V. The current density during charging and discharging, the first time a 0.057mA / cm ^2, the second and subsequent cycles was 0.28mA / cm ^2.

  On the other hand, an electrode for comparison with the electrode according to Example 2 was manufactured by a conventional method. Such an electrode is composed of the glass powder produced in [1], Ketjen Black (Lion Co., Ltd. EC600JD, particle size: 34.0 nm or less) as a conductive additive, and N-methyl-2-pyrodoline (as a binder). Polyvinylidene fluoride (PVDF) (# 7305 manufactured by Kureha Co., Ltd.) dissolved in 5% by mass in NMP) was mixed using a mortar at a mass ratio of 85: 5: 10. At this time, in order to adjust the viscosity, the slurry was slurried while appropriately mixing NMP. The obtained slurry was applied onto a 20 μm thick aluminum alloy foil (N5-8X-073 manufactured by Mitsubishi Aluminum Co., Ltd.) using a blade coater with a gap of 200 μm. This was dried in air at 90 ° C. × 2 hr, and then punched out into a disk shape having a diameter of 15 mm. Next, after pressing at about 400 MPa, the electrode according to Comparative Example 2 was manufactured by vacuum drying at 120 ° C. for 1 hour. Then, the manufactured electrode according to Comparative Example 2 was used as the positive electrode, and the charge / discharge characteristics were evaluated under the same model cell and conditions as those of the tripolar model cell described with reference to FIG.

The following was confirmed as an evaluation of the charge / discharge characteristics.
Compared with the electrode (positive electrode) according to Comparative Example 2, the electrode (positive electrode) according to Example 2 had an improved charge / discharge capacity and an improved charge / discharge capacity retention rate after 10 cycles.
Specifically, in the magnesium ion secondary battery using the electrode according to Comparative Example 2 as the positive electrode, the initial charge / discharge capacity was 250 mAh / g, and the charge / discharge capacity after 10 cycles was 175 mAh / g. That is, the charge / discharge capacity retention rate after 10 cycles was 70%.
On the other hand, in the magnesium ion secondary battery using the electrode according to Example 2 as the positive electrode, the initial charge / discharge capacity was 300 mAh / g, and the charge / discharge capacity after 10 cycles was 285 mAh / g. That is, the charge / discharge capacity retention rate after 10 cycles was 95%.

101 Ion secondary battery electrode (electrode)
102 Conductor 103 Vanadium oxide coating (coating)
DESCRIPTION OF SYMBOLS 201 Coating film formation apparatus 202 Gas supply apparatus 203 Gas supply pipe 204 Gas heater 205 Working gas supply pipe 206 Spray nozzle 207 Glass powder supply apparatus 208 Glass powder supply pipe 301 Ion secondary battery electrode 302 Conductor 303 Vanadium oxide film (Coating)
401 Crystal 402 Amorphous 501 Crystal 502 Amorphous 601 Double-chain VO ₆ octahedron 701 Lithium ion secondary battery 702 Positive electrode 703 Positive electrode current collector 704 Negative electrode 705 Negative electrode current collector 706 Container 707 Electrolyte 708 Separator 709 Lid 710 Gasket 801 Positive electrode 802 Aluminum current collector foil 803 Negative electrode 804 Copper current collector foil 805 Separator 806 SUS jig 901 Positive electrode 902 Aluminum current collector foil 903 Negative Li plate 904 Reference electrode Li plate 905 Separator 906 SUS jig 1001 Positive electrode 1002 Aluminum current collector foil 1003 Magnesium alloy (AZ31 alloy) negative electrode 1004 Magnesium alloy (AZ31 alloy) plate of reference electrode 1005 Separator 1006 SUS jig

Claims (13)

An electrode for an ion secondary battery provided with a vanadium oxide film formed by thermal spraying or fusing on a surface of a conductor , wherein the vanadium oxide film contains a crystal and an amorphous material. An electrode for an ion secondary battery. An electrode for an ion secondary battery according to claim 1,
The vanadium oxide film contains vanadium, phosphorus, and at least one element selected from copper, silver, iron, alkaline earth metal and alkali metal. Secondary battery electrode. An electrode for an ion secondary battery according to claim 1 ,
An electrode for an ion secondary battery, wherein a volume fraction of crystals with respect to amorphous in the vanadium oxide film is 94% or less. An electrode for an ion secondary battery according to claim 1 ,
An electrode for an ion secondary battery, wherein a main crystal in the vanadium oxide film is a monoclinic crystal. Provide a vanadium oxide film formed by softening on the surface of the conductor,
The vanadium oxide film is an electrode for an ion secondary battery containing crystal and amorphous,
An electrode for an ion secondary battery, wherein the crystal in the vanadium oxide film is oriented. An electrode for an ion secondary battery according to claim 5 ,
An electrode for an ion secondary battery, wherein the [100] crystal orientation of the crystal oriented in the vanadium oxide film is perpendicular to the surface of the conductor. An electrode for an ion secondary battery in which a vanadium oxide film formed by softening is provided on the surface of a conductor,
An electrode for an ion secondary battery, wherein irregularities are formed on the surface of the vanadium oxide film. An electrode for an ion secondary battery according to claim 1,
An electrode for an ion secondary battery, wherein the vanadium oxide film is pre-doped with lithium ions. An electrode for an ion secondary battery according to claim 1,
An electrode for an ion secondary battery, wherein the conductor is made of at least one of aluminum, an aluminum alloy, copper, a copper alloy, and carbon. A method for producing an ion secondary battery electrode for producing an ion secondary battery electrode according to any one of claims 1 to 9 ,
A method for producing an electrode for an ion secondary battery, comprising a step of spraying a powder thermal spray material containing vanadium oxide on a surface of a conductor to provide a vanadium oxide film. A manufacturing method of an ion secondary battery electrode according to the first 0 wherein claims,
A method for producing an electrode for an ion secondary battery, comprising the step of heating the conductor provided with the vanadium oxide film at the crystallization temperature of the vanadium oxide film after the step. A lithium ion secondary battery comprising the ion secondary battery electrode according to any one of claims 1 to 9 . A magnesium ion secondary battery using the electrode for an ion secondary battery according to any one of claims 1 to 9 .

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