Sulfur-based active material
The present invention provides a sulfur-based active material prepared using an inexpensive polymer material as a starting material and a method of preparing the sulfur-based active material. A non-aqueous electrolyte secondary battery such as a lithium-ion secondary battery provided with an electrode comprising the sulfur-based active material has a large charging and discharging capacity and an excellent cyclability.
1. A sulfur-based active material prepared by baking a starting material comprising:
elemental sulfur and
a copolymer comprising methacrylonitrile, acrylonitrile and (meth)acrylic ester as monomer components.
2. The sulfur-based active material of claim 1 , characterized in that in a Raman spectrum, there are peaks at around 1,530 cm −1 , at around 1,320 cm −1 , at around 940 cm −1 , at around 470 cm −1 , at around 370 cm −1 , and at around 310 cm −1 .
3. The sulfur-based active material of claim 1 , wherein a temperature for baking the starting material is from 250 to 550° C.
4. The sulfur-based active material of claim 1 , wherein the starting material further comprises an electrically conductive additive.
5. The sulfur-based active material of claim 4 , wherein the electrically conductive additive is an electrically conductive carbon material.
6. The sulfur-based active material of claim 1 , wherein the total content of sulfur in the sulfur-based active material is 35% by mass or more as measured by elemental analysis.
7. The sulfur-based active material of claim 1 , wherein the sulfur-based active material is composed of five elements, C, H, N, S and O.
8. The sulfur-based active material of claim 1 , wherein the copolymer is a methacrylonitrile-acrylonitrile-methyl methacrylate copolymer.
9. The sulfur-based active material of claim 1 , wherein the weight ratio of the copolymer to the elemental sulfur is in the range of 100 parts by mass of the copolymer to 250 to 2,000 parts by mass of the elemental sulfur.
10. The sulfur-based active material of claim 1 , wherein the weight ratio of the copolymer to the elemental sulfur is in the range of 100 parts by mass of the copolymer to 300 to 1,500 parts by mass of the elemental sulfur.
11. An electrode for a non-aqueous electrolyte secondary battery, the electrode comprising the sulfur-based active material of claim 1 .
12. A non-aqueous electrolyte secondary battery comprising the electrode of claim 11 .
13. A method of preparing a sulfur-based active material, the method comprising a step of baking a starting material comprising elemental sulfur and a polymer including methacrylonitrile as a monomer component.