Flexible substrate processing apparatus

1. A method for reducing graphene oxide to form graphene with the use of a flexible substrate processing apparatus, the flexible substrate processing apparatus comprising:

a substrate carrying-out portion comprising an unwinder provided with a first bobbin configured so that a flexible substrate is wound around the first bobbin;

a reduction treatment portion comprising a first bath configured to be provided with an electrolyte, a first electrode configured so that the flexible substrate is located in parallel with the first electrode in the first bath, and first rollers configured so that the flexible substrate is soaked in the electrolyte, wherein the electrolyte includes an aprotic solvent;

a washing portion comprising a second bath configured to be provided with a washing solution and second rollers configured to support the flexible substrate so that the flexible substrate is soaked in the washing solution;

a drying portion comprising a drying means; and

a substrate carrying-in portion comprising a winder provided with a second bobbin configured to take up the flexible substrate,

wherein one or more of the first bobbin, the second bobbin, the first rollers, and the second rollers serve as a second electrode,

the method comprising the steps of:

making the flexible substrate be contact with the first bobbin and taking the flexible substrate up in the substrate carrying-out portion;

making the flexible substrate and the first electrode be soaked in the electrolyte in the first bath;

reducing graphene oxide contained in a film-like structure body formed on the flexible substrate to form graphene by supplying a certain potential to the second electrode so that the flexible substrate is at the same potential as the second electrode, wherein the film-like structure body further comprises an electrode active material;

washing the film-like structure body and the flexible substrate in the second bath;

drying the film-like structure body and the flexible substrate with the use of the drying means in the drying portion; and

taking the flexible substrate up by the second bobbin

wherein a reduction potential for the reducing step to be supplied is a reduction potential determined relative to a redox potential of lithium metal, and

wherein the reduction potential for the reducing step to be supplied is 2.0 V.

2. The method according to claim 1 , further comprising the steps of:

forming the film-like structure body over a surface of the flexible substrate; and drying the film-like structure body formed on the flexible substrate.

3. The method according to claim 1 , further comprising the step of:

forming a stack of the flexible substrate and plural flexible substrates other than the flexible substrate before taking the flexible substrate up by the second bobbin.

4. The method according to claim 1 ,

wherein a proportion of carbon atoms in the graphene measured by X-ray photoelectron spectroscopy greater than or equal to 80% and less than or equal to 90%,

wherein a proportion of oxygen atoms in the graphene measured by X-ray photoelectron spectroscopy is greater than or equal to 10% and less than or equal to 20%, and

wherein a proportion of sp2-bonded carbon atoms of carbon atoms in the graphene is greater than or equal to 50% and less than or equal to 70%.

5. The method according to claim 1 ,

wherein a proportion of part of oxygen remaining in the graphene is higher than or equal to 2% and lower than or equal to 20%.

6. The method according to claim 1 ,

wherein a material used for the film-like structure body is a mixture in which an oxide and an organic compound are mixed.

7. The method according to claim 4 ,

wherein the graphene comprises a sulfate ion.

8. The method according to claim 4 ,

wherein the electrode active material is a positive electrode active material.