Active material, anode layer, battery, and methods for producing these
A main object of the present disclosure is to provide an active material wherein a volume variation due to charge/discharge is small. The present disclosure achieves the object by providing an active material comprising a silicon clathrate II type crystal phase, including a void inside a primary particle, and a void amount of the void with a fine pore diameter of 100 nm or less is 0.05 cc/g or more and 0.15 cc/g or less.
1. An active material comprising a silicon clathrate II type crystal phase,
including a void inside a primary particle, and
a void amount of the void with a fine pore diameter of 100 nm or less is 0.05 cc/g or more and 0.15 cc/g or less.
2. The active material according to claim 1 , wherein, as peaks of the silicon clathrate II type crystal phase, peak “A” at a position of 2θ=20.09°±0.50° and peak “B” at a position of 2θ=31.72°±0.50° are observed in X-ray diffraction measurement using a CuKα ray, and
when an intensity of the peak “A” is regarded as I A , an intensity of the peak “B” is regarded as I B , and a maximum intensity in 2θ=22° to 23° is regarded as I M , I A /I M and I B /I M are respectively more than 1.
3. The active material according to claim 1 , wherein, peak “X” at a position of 99.2 eV±0.4 eV as a peak of Si(2p) deriving from Si, and peak “Y” at a position of 103.6 eV±0.4 eV as a peak of Si(2p) deriving from SiO 2 are observed in X-ray photoelectron spectroscopy measurement, and
when an intensity of the peak “X” is regarded as I X , and an intensity of the peak “Y” is regarded as I Y , I Y /I X is 1.30 or less.
4. The active material according to claim 3 , wherein the I Y /I X is 0.81 or less.
5. An anode layer comprising the active material according to claim 1 .
6. A battery comprising a cathode layer, an anode layer, and an electrolyte layer formed between the cathode layer and the anode layer, and
the anode layer is the anode layer according to claim 5 .
7. A method for producing an active material, the method comprising:
a preparing step of preparing an intermediate including a silicon clathrate II type crystal phase of claim 1 ,
an alloying step of obtaining an alloy compound by alloying the intermediate and a Li based material so as a molar ratio (Li/Si) of Li included in the Li based material to Si included in the intermediate is 3 or less, and
a Li removing step of removing the Li from the alloy compound and forming a void inside a primary particle.
8. The method for producing an active material according to claim 7 , wherein the Li/Si is 0.5 or more.
9. The method for producing an active material according to claim 7 , wherein, in the Li removing step, the Li is removed from the alloy compound using an ethanol.
10. A method for producing an anode layer, the method comprising:
an active material producing step of producing an active material by the method for producing an active material according to claim 7 , and
an anode layer forming step of forming an anode layer using the active material.
11. A method for producing a battery, the method comprising:
an active material producing step of producing an active material by the method for producing an active material according to claim 7 , and
an anode layer forming step of forming an anode layer using the active material.