Method for producing active material, active material and battery
A main object of the present disclosure is to provide a novel active material of which volume change due to charge and discharge is small. The present disclosure achieves the object by providing a method for producing an active material having a composition represented by Na x M y Si 46 (M is a metal element other than Na, x and y satisfy 0<x, 0≤y, y≤x, and 0<x+y<8), and a silicon clathrate I type crystal phase, the method comprising: a preparing step of preparing a precursor compound having the silicon clathrate I type crystal phase; and a liquid treatment step of bringing the precursor compound into contact with a polar liquid so as to desorb a Na element from the precursor compound and obtain the active material.
1. A method for producing an active material having a composition represented by Na x M y Si 46 (M is a metal element other than Na, x and y satisfy 0<x, 0≤y, y≤x, and 0<x+y<8), and a silicon clathrate I type crystal phase, the method comprising:
a preparing step of preparing a precursor compound having the silicon clathrate I type crystal phase; and
a liquid treatment step of bringing the precursor compound into contact with a polar liquid so as to desorb a Na element from the precursor compound and obtain the active material.
2. The method for producing the active material according to claim 1 , wherein the polar liquid contains at least one kind of water, alcohol, and inorganic acid.
3. The method for producing the active material according to claim 1 , wherein the polar liquid contains at least one kind of water and alcohol.
4. The method for producing the active material according to claim 1 , wherein the preparing step is a step of conducting a heat treatment to a NaSi compound containing at least a Na element and a Si element under decompressed pressure so as to desorb the Na element from the NaSi compound and obtain the precursor compound.
5. The method for producing the active material according to claim 4 , wherein, in the heat treatment, heat treatment temperature is less than 550° C. and heat treatment time is 12 hours or less.
6. The method for producing the active material according to claim 1 , wherein the x and they satisfy 1.1≤x+y.
7. An active material comprising a composition represented by Na x M y Si 46 (M is a metal element other than Na, x and y satisfy 0<x, 0≤y, y≤x, and 0<x+y<8), and a silicon clathrate I type crystal phase; wherein
a residue of a polar liquid is present on a surface of the active material.
8. The active material according to claim 7 , wherein the residue of the polar liquid contains at least one kind of alcohol and inorganic acid.
9. A battery comprising a cathode layer, an electrolyte layer, and an anode layer in this order, wherein
the anode layer contains the active material according to claim 7 .
10. The active material according to claim 7 , wherein x is less than or equal to 4.3.
11. The active material according to claim 7 , wherein y is greater than 0.
12. The active material according to claim 7 , wherein an average primary particle size of the composition is 50 nanometers (nm) or more.
13. The active material according to claim 12 , wherein the average primary particle size of the composition is 3,000 nm or less.
14. The active material according to claim 12 , wherein an average secondary particle size of the composition is 1 micron (μm) or more.
15. The active material according to claim 14 , wherein the average secondary particle size is 60 μm or less.
16. The active material according to claim 7 , wherein a ratio of a diamond type crystal phase to the silicon clathrate I type crystal phase to in the composition is 1.2 or less.
17. The active material according to claim 7 , wherein a ratio of a silicon clathrate II type crystal phase to the silicon clathrate I type crystal phase to in the composition is 1 or less.
18. The active material according to claim 7 , wherein a ratio of a Zintl crystal phase to the silicon clathrate I type crystal phase to in the composition is 0.5 or less.
19. The active material according to claim 7 , wherein M is an alkali metal element or an alkaline earth metal element, and y is greater than 0.
20. The active material according to claim 7 , wherein y is greater than 0, and M is selected from the group consisting of an 11 th group element, a 12 th group element, a 13 th group element, a 15 th group element and a 16 th group element.