Active material, method of manufacturing active material, electrode, and secondary battery
A secondary battery includes a cathode, an anode including an active material, and non-aqueous electrolytic solution. The active material includes a center portion and a covering portion provided on part or all of the center portion. The center portion includes silicon, tin, or both as constituent elements. The covering portion includes a plurality of fibrous carbon materials. Part or all of the fibrous carbon materials extend in a direction along a surface of the center portion and are closely attached to the center portion.
1. A secondary battery, comprising:
a cathode;
an anode including an active material; and
a non-aqueous electrolytic solution,
wherein:
the active material including a center portion, and a covering portion provided on a first part of the center portion,
the center portion including at least one of silicon (Si) or tin (Sn) as constituent elements,
the covering portion including a plurality of fibrous carbon materials,
an entire length of each fibrous carbon material of a first set of the plurality of fibrous carbon materials extends in a direction along a surface of the center portion,
the entire length of the each fibrous carbon material of the first set of the plurality of fibrous carbon materials includes a first end portion, a middle portion and a second end portion,
the entire length of the each fibrous carbon material of the first set of the plurality of fibrous carbon materials is attached to the center portion, and
a second set of the plurality of fibrous carbon materials is tangled with one another.
2. The secondary battery according to claim 1 , wherein the covering portion includes a mesh structure that comprises the second set of the plurality of fibrous carbon materials.
3. The secondary battery according to claim 1 , wherein
the anode includes a plurality of the active materials, and
a third set of the plurality of fibrous carbon materials is in the plurality of the active materials, wherein fibrous carbon materials of the third set of the plurality of fibrous carbon materials are cross-linked with each other.
4. The secondary battery according to claim 1 , wherein the plurality of fibrous carbon materials comprises at least one of carbon nanotubes or carbon nanofibers.
5. The secondary battery according to claim 1 , wherein 85 percent or higher of the plurality of fibrous carbon materials have a fiber length equal to or smaller than 4 micrometers.
6. The secondary battery according to claim 1 , wherein the plurality of fibrous carbon materials has an average fiber diameter equal to or smaller than 102 nanometers.
7. The secondary battery according to claim 1 , wherein a ratio of an area of a G-band peak to an area of a D-band peak (the area of the G-band peak/the area of the D-band peak) is equal to or greater than 1 in Raman spectrum of the plurality of fibrous carbon materials that is measured by Raman spectroscopy.
8. The secondary battery according to claim 1 ,
wherein the anode includes a plurality of the active materials, and
wherein the center portion has a median size (D50) equal to or smaller than 7.8 micrometers.
9. The secondary battery according to claim 1 , wherein each fibrous carbon material of the plurality of fibrous carbon materials has a carboxyl group (—COOH) on a surface thereof.
10. The secondary battery according to claim 1 , wherein a peak derived from a 1s orbit of oxygen (O) is detected as a result of element analysis of the plurality of fibrous carbon materials by X-ray photoelectron spectroscopy (XPS).
11. The secondary battery according to claim 1 , wherein the center portion comprises at least one of silicon, an alloy of silicon, a compound of silicon, tin, an alloy of tin, or a compound of tin.
12. The secondary battery according to claim 1 ,
wherein the active material includes an intermediate portion provided on the first part of the center portion, the intermediate portion including carbon (C) as a constituent element, and
wherein the covering portion is provided on the center portion with the intermediate portion in between.
13. The secondary battery according to claim 1 , wherein the active material includes carbon as a constituent element.
14. The secondary battery according to claim 1 , wherein the secondary battery is a lithium ion secondary battery.
15. The secondary battery according to claim 1 , wherein the center portion comprises at least one of a single granular body, and wherein an atomic ratio of oxygen to silicon is from 0.5 to 1.8.
16. The secondary battery according to claim 12 , wherein an electric resistance of the intermediate portion is lower than an electric resistance of the center portion.