JP6302163B2 - Method for producing corrosion-resistant metal member for battery - Google Patents

Description

  The present invention relates to a corrosion-resistant metal member for a battery that contacts a battery electrolyte, and relates to a corrosion-resistant metal member used for, for example, an electrode member such as a current collector for a storage battery or a battery cell case.

  In general, titanium metal is excellent in corrosion resistance because it forms a passivating film in air, and is widely used because it forms alloys with copper, tin, iron, aluminum, vanadium, chromium, cobalt, nickel, molybdenum, etc. It is a metal material.

  Such titanium metal is known to form a thin glassy carbon on the surface of its polished surface in order to improve wear resistance and lubricity when used in fastening parts such as bolts and nuts. (Patent Document 1).

  Further, it is known that the surface of a thick titanium metal carburized layer used for a fastening member such as a screw is polished and further oxidized to form a titanium oxide layer, on which glassy carbon is formed ( Patent Document 2).

Japanese Patent No. 3347287 JP 2012-31459 A

  However, in the techniques described in Patent Documents 1 and 2 described above, glassy carbon is used to improve the wear resistance or lubricity of the surface of a thick structural material. It is not intended to improve the corrosion resistance of the metal member used in the above.

  Further, in the above-described prior art, a thick metal member serving as a glassy carbon base material cannot be easily processed by bending deformation or the like.

By the way, the corrosion-resistant metal member used for the electrode member such as the current collector for the storage battery and the inner surface of the battery cell case is an electrolyte solution containing highly corrosive halide ions such as fluoride ions and chloride ions. When used in contact, a specific metal material such as platinum having extremely excellent corrosion resistance is used.

  For example, due to the corrosive nature of the chloride ions present in such corrosive electrolytes, many small pores of corrosion called “pitting corrosion” occur on the surface of titanium metal with excellent corrosion resistance. There is.

  Thus, in a corrosion-resistant metal material for a battery that can use only a specific expensive metal material such as platinum, the selection range of the material is narrow, and it is difficult to suppress the manufacturing cost, and it is difficult to manufacture a practical storage battery. There is a problem that can not be.

In addition, as described above, the known glassy carbon form is not supposed to be used to withstand bending deformation, and cannot be diverted to a part that can bend and deform a bulky bulk product surface. .

  Accordingly, an object of the present invention is to solve the above-described problems, expand the range of selection of a corrosion-resistant metal member for a battery that comes into contact with the battery electrolyte, and satisfy the corrosion resistance and formability. In addition, it is to be a corrosion-resistant metal member that can be used for an electrode member such as a current collector that requires conductivity or a cell case for a battery that is in contact with an electrolytic solution.

  In order to solve the above-described problems, the present invention provides a corrosion-resistant metal member for a battery in which a glassy carbon thin film layer is integrally provided on the surface of a sheet-like metal member that is in contact with the battery electrolyte.

  As described above, the sheet-like metal member integrally provided with the glassy carbon thin film layer deforms together with the glassy carbon thin film layer according to the bending characteristics of the sheet that can be bent and deformed. A mode in which thin sheets are wound or stacked according to the shape is also possible, and the extremely excellent corrosion resistance inherent to glassy carbon can also be exhibited.

  For this reason, the surface of the sheet-like metal member is protected from the battery electrolyte by the glassy carbon thin film layer, and “pitting corrosion” does not occur or is suppressed. It becomes a corrosion-resistant metal member that can be used for an electrode member such as a current collector or a battery cell case in contact with an electrolytic solution.

  As described above, the vitreous carbon can be used in applications where the thin film of vitreous carbon is in contact with a strong corrosive liquid such as an electrolytic solution for a battery while ensuring the property capable of bending deformation.

  In the above corrosion-resistant metal member for a battery, in order for the glassy carbon thin film layer to be integrated and sufficiently deformed in accordance with the bending characteristics of the sheet, the glassy carbon thin film layer has a thickness of 0.1 to 0.1 mm. It is preferably 1 μm.

  In a thin glassy carbon thin film layer having a thickness of less than 0.1 μm, for example, “pitting corrosion” in contact with an electrolyte containing highly corrosive halide ions such as fluoride ions and chloride ions. It is difficult to completely prevent corrosion, and it is not preferable, and a relatively thick glassy carbon thin film layer exceeding 1 μm is not preferable because bending deformability tends to be hindered instead of obtaining corrosion resistance more than necessary. is there.

  A case where the sheet-like metal member is a current collector can be cited as an embodiment in which such preferable characteristics as a corrosion-resistant metal member for a battery can be sufficiently exhibited.

  The current collector may be wound into a roll as a filmed electrode member for a battery cell, or may be formed as thin as a metal foil and laminated to a resin film. In this case, if the sheet-like metal member is integrally provided with the glassy carbon thin film layer, excellent corrosion resistance and bending deformability can be exhibited at the same time.

  In addition, when the sheet metal member is made of a titanium metal material, the inherent properties of titanium metal such as workability, lightness, strength, and variety of types of alloys are exhibited, and the battery is extremely useful. It becomes a corrosion-resistant metal member.

In addition, when the battery is a magnesium storage battery, it is possible to solve the problem that only platinum as a positive electrode side current collector material has been selected so far, and the selection of the current collector material can be greatly expanded. it can.

  As a method for producing a corrosion-resistant metal member having the advantageous characteristics as described above, a glassy carbon thin film layer having a thickness of 0.1 to 1 μm is formed by plasma carburization on the surface of a sheet-like hard carburizing metal material. The manufacturing method of the corrosion-resistant metal member which contacts with the electrolyte solution for batteries which consists of doing can be employ | adopted.

  By subjecting the surface of the hardly carburizable metal material to plasma carburization, an extremely thin glassy carbon thin film layer having a thickness of 0.1 to 1 μm can be reliably formed on the surface of the metal material.

  Since the present invention is a corrosion-resistant metal member in which a glassy carbon thin film layer is integrally provided on the surface of a sheet-like metal member that is in contact with the battery electrolyte, such a corrosion-resistant metal member that is in contact with the battery electrolyte is It can be used for electrode members such as current collectors that require electrical conductivity or battery cases that come into contact with electrolytes, which can expand the range of selection of metal materials and satisfy corrosion resistance and formability. There is an advantage that it becomes a possible corrosion-resistant metal member.

Scanning electron micrograph showing the surface of the battery current collector of Example 1 and its cross section Chart showing the Raman spectrum of the surface of the battery current collector of Example 1 (A) Scanning electron micrograph showing the surface of Example 1 before the electrolysis test, (b) Scanning electron micrograph showing the surface of Example 1 after the electrolysis test (A) Scanning electron micrograph showing the surface of the comparative example 1 before the electrolytic test, (b) Scanning electron micrograph showing the surface of the comparative example 1 after the electrolytic test The chart which shows the Raman spectrum of the collector surface for batteries of Example 2 (A) Scanning electron micrograph showing the surface of Example 2 before the electrolysis test, (b) Scanning electron micrograph showing the surface of Example 2 after the electrolysis test (A) Scanning electron micrograph showing the surface of the comparative example 2 before the electrolytic test, (b) Scanning electron micrograph showing the surface of the comparative example 2 after the electrolytic test. (A) Cyclic voltammogram showing the relationship between the potential and current density of the working electrode (Ti current collector coated with a glassy carbon thin film) of Example 1 in the electrolytic test with respect to the reference electrode (Mg), and (b) in the electrolytic test. Cyclic voltammogram showing the relationship between the potential and current density of the working electrode (SUS316L current collector coated with a glassy carbon thin film) of Example 2 relative to the reference electrode (Mg). (A) to (g) are cyclic voltammograms showing the relationship between potential and current density of various working electrodes with respect to a reference electrode (Mg) in an electrolytic test.

Embodiments of the present invention will be described below with reference to the accompanying drawings.
The battery corrosion-resistant metal member of the embodiment shown in the scanning electron micrograph of FIG. 1 is used in contact with the battery electrolyte, and is, for example, a sheet metal for a secondary battery made of a titanium metal foil. A glassy carbon thin film layer 2 is integrally provided on the surface of the member 1 by plasma carburization. In addition, the code | symbol 2a in a figure is the surface of the glassy carbon thin film layer 2. FIG.

The battery electrolyte according to the present invention is an electrolyte containing highly corrosive halide ions such as fluoride ions (F ⁻ ) and chloride ions (Cl ⁻ ). In addition, bromide ions (Br ⁻ ), iodide ions (I ⁻ ), asterathionide ions (At ⁻ ), and the like can be given.

Specific examples of the electrolyte include tetrahydrofuran-based electrolytes (0.5M PhMgCl, 0.25M AlCl ₃ THF solution) based on Grignard reagents known as magnesium battery electrolytes.

  In addition to the electrolyte solution containing halide ions, the battery corrosion-resistant metal member of the embodiment can be used in other well-known electrolyte solutions and solvents. Examples of such a solvent include water, ethanol. Alcohols such as acetonitrile, organic solvents such as acetonitrile and tetrahydrofuran derivatives, and ionic liquids (liquid salts composed only of anions and cations).

  The sheet-like metal member used in the present invention is formed in a sheet shape that is thin enough that the metal member can be bent. The metal material includes titanium metal, stainless steel, other steels, aluminum, Well-known pure metals such as copper and nickel, or alloys thereof with other metals can be mentioned.

  Such a metal is preferably a metal having a melting point of about 800 ° C. or higher so that plasma carburizing treatment at a relatively low temperature is possible, and a thin glassy carbon can be formed by carburizing treatment. Further, it is preferably a metal having a low carbon absorption capacity, that is, a hardly carburizable metal or a metal surface-treated as such, and a metal having a low coefficient of thermal expansion.

  The thickness of the sheet-like metal member used in the present invention may be adjusted according to each case of a thin plate shape, a film shape, and a foil shape. For example, it is used for a current collector of a secondary battery, etc. Laminate the rolled metal on the surface of the resin sheet substrate of the substrate and heat it to bond it, or form the metal itself in close contact with the surface of the sheet substrate by thermal spraying or plating Can do.

  And the process of forming a glassy (amorphous) carbon layer on the surface of such a sheet-like metal member by plasma carburization is performed as follows.

The pressure of the hydrocarbon-based gas under the plasma carburizing treatment condition is preferably 13 to 4000 Pa. Such a pressure of the hydrocarbon gas efficiently forms an amorphous carbon (glassy carbon) film mainly on the titanium metal surface. A low pressure of less than 13 Pa is not preferable because the amount of carbon in the film formation layer is small and film formation is not sufficient. Moreover, practicality may be impaired at a high pressure exceeding 4000 Pa. From such a tendency, the more preferable pressure of the hydrocarbon gas is 100 to 2666 Pa.

  The atmospheric temperature of the plasma heat treatment for forming the glassy carbon layer in the present invention is preferably 400 to 1100 ° C, more preferably 500 to 1100 ° C, and further preferably 530 to 890 ° C. If the temperature is lower than the predetermined range, the adhesion of glassy carbon to the titanium metal surface is unfavorable. Further, at a high temperature exceeding the above-mentioned predetermined range, a treatment temperature higher than this is not preferable in order to ensure the strength characteristics of titanium.

Under such conditions, plasma heat treatment for forming a glassy carbon layer by plasma carburizing treatment is performed, and thereafter, carburizing gas in the processing chamber is exhausted, nitrogen gas is introduced into the processing chamber, and titanium metal is introduced. The material is cooled to room temperature and removed from the processing chamber.

[Example 1]

A titanium metal sheet (thickness: 500 μm) serving as a base material for the current collector was formed into an amorphous carbon layer having a thickness of about 1 μm by plasma carburization in an atmospheric gas temperature range of 500 to 700 ° C. in a vacuum apparatus.

About the surface of the obtained electrical power collector, the Raman spectrum was measured using the micro Raman laser microscope, and the result shown in FIG. 2 was obtained. In addition, the measurement was performed by laser irradiation with a wavelength of 532 nm using Nanophoton RAMAN-11.

As is apparent from the results shown in FIG. 2, the Raman spectrum has a G band peak (near 1594 cm ⁻² ) indicating a crystalline carbon peak and a D band peak (1330 cm ⁻²⁾ indicating an amorphous carbon peak. The presence of a glassy carbon layer was confirmed.
Next, the following electrolysis test was performed on the current collector of Example 1, and the surface before and after the test was photographed with a scanning electron microscope. The results are shown in FIGS. 3 (a) and 3 (b).

[Electrolysis test]
The current collector of Example 1 is used as a working electrode, the counter electrode and the reference electrode are made of magnesium (Mg), and a tetrahydrofuran electrolyte (0.5M PhMgCl, 0.2
5M AlCl ₃ THF solution) was used to perform potential scanning in which the potential of the working electrode with respect to the reference electrode was changed from 0 to +4 V at 10 mV / sec in a test cell.

  As is clear from the results of FIG. 3, Example 1 having a glassy carbon thin film coating showed almost no change in the surface shape according to the scanning electron micrograph before and after the electrolytic test.

[Comparative Example 1]
In Example 1, a current collector was produced in exactly the same manner except that the glass-like carbon thin film layer was not formed without performing the plasma carburizing treatment, and the above electrolytic test was performed on the current collector. The front and back surfaces were photographed with a scanning electron microscope, and the results are shown in FIGS. 4 (a) and 4 (b).

  As is apparent from the results of FIG. 4, pitting corrosion was observed on the surface after the electrolytic test in Comparative Example 1 having no glassy carbon thin film coating.

[Example 2]
A current collector was produced in exactly the same manner except that stainless steel (SUS316L) was used instead of titanium metal in Example 1. About the surface of the obtained electrical power collector, the Raman spectrum was measured using the micro Raman spectroscopy apparatus, and the result shown in FIG. 5 was obtained.

As is apparent from the results shown in FIG. 5, the Raman spectrum has a G band (near 1594 cm ⁻² ) showing a crystalline carbon peak and a D band (near 1330 cm ⁻² ) showing an amorphous carbon peak. Was observed even though it was small, and the presence of a very thin glassy carbon layer considered to have a thickness of about 0.1 to 0.5 μm was observed.

Next, the above-described electrolytic test was performed on the current collector of Example 2, and the surface before and after the test was photographed with a scanning electron microscope. The results are shown in FIGS. 6 (a) and 6 (b).
As is clear from the results of FIG. 6, Example 2 having a glassy carbon thin film coating showed some small pitting corrosion after the electrolytic test, but it was corrosion enough to withstand use as a current collector. The surface shape hardly changed.

[Comparative Example 2]
In Example 2, a current collector was prepared in exactly the same manner except that the glass-like carbon thin film layer was not formed without performing the plasma carburizing treatment, and the above-described electrolytic test was performed. The front and back surfaces were photographed with a scanning electron microscope, and the results are shown in FIGS. 7 (a) and 7 (b).

  As is apparent from the results of FIG. 7, pitting corrosion was observed on the surface after the electrolytic test in Comparative Example 2 having no glassy carbon thin film coating.

  Moreover, the result of the cyclic voltammogram which shows the relationship between the electric potential and electric current density in the electrolysis test of above-mentioned Example 1, 2 was shown to Fig.8 (a) (b). For reference, potential scanning is performed by changing the potential with respect to the reference electrode (Mg) from −1 to +4 V at 10 mV / sec using various metals and glassy carbon as a working electrode. The results of cyclic voltammograms showing the relationship are shown in FIGS. 9 (a) to 9 (g).

  As is clear from these results, the current collector material coated with the glassy carbon thin film showed the same stability as platinum (Pt), but other copper, nickel, In stainless steel, titanium, and aluminum metal, remarkable oxidative dissolution was observed with increasing potential, and the steel was unstable.

1 sheet-like metal member 2 glassy carbon thin film layer 2a surface

Claims (4)

A glassy carbon thin film layer having a thickness of 0.5 to 1 μm that prevents pitting corrosion while being in contact with the battery electrolyte is applied to the surface of a sheet-like hardly carburizable metal material, and the pressure of the hydrocarbon gas. The manufacturing method of the corrosion-resistant metal member which contacts with the electrolyte solution for batteries consisting of forming by the plasma carburizing process in 100-2666Pa and the atmospheric gas temperature range of 500-700 degreeC .   The method for producing a corrosion-resistant metal member in contact with the battery electrolyte according to claim 1, wherein the corrosion-resistant metal member in contact with the battery electrolyte is a current collector.   The method for producing a corrosion-resistant metal member in contact with the battery electrolyte according to claim 1 or 2, wherein the corrosion-resistant metal member in contact with the battery electrolyte is a sheet-like titanium metal member. The said battery is a magnesium storage battery, The manufacturing method of the corrosion-resistant metal member which contacts the electrolyte solution for batteries in any one of Claims 1-3.