SOLID ELECTROLYTE AND METHOD FOR PRODUCING SAME

1 . A solid electrolyte comprising:

a lithium (Li) element, a phosphorous (P) element, a sulfur (S) element, and a halogen (X) element,

wherein the solid electrolyte has a crystal phase that has an argyrodite-type crystal structure,

the crystal phase that has an argyrodite-type crystal structure has a crystallite size of 40 nm or less, and

the solid electrolyte satisfies a ratio Ia/Ib of 0.2 or less, the ratio Ia/Ib being the ratio of Ia relative to Ib, where Ia represents the intensity of a peak A observed in a range of 2θ=27.0°±0.5° in an X-ray diffraction pattern obtained by measuring the solid electrolyte with an X-ray diffractometer (XRD) using CuKα1 rays, and Ib represents the intensity of a peak B observed in a range of 2θ=25.5°±1.0° in the X-ray diffraction pattern.

2 . The solid electrolyte according to claim 1 ,

wherein the solid electrolyte satisfies a ratio IC/I0 of 1.55 or less, the ratio IC/I0 being the ratio of IC relative to I0, where IC represents the maximum count number of a peak C observed in a range of 2θ=21.3°±0.3° in the X-ray diffraction pattern, and I0 represents the intensity of a background observed in a range of 2θ=23.5°±0.5° in the X-ray diffraction pattern.

3 . The solid electrolyte according to claim 1 ,

wherein the solid electrolyte has a brightness L* value in an L*a*b* colorimetry system of 90 or less.

4 . The solid electrolyte according to claim 1 ,

wherein the solid electrolyte has a cumulative volume particle size D 50 at 50% cumulative volume obtained using a laser diffraction scattering particle size distribution measurement method of 5 μm or less.

5 . The solid electrolyte according to claim 1 ,

wherein a molar ratio of the halogen (X) element to the phosphorous (P) element is 1.1 or more, and

a molar ratio of the sulfur (S) element to the phosphorous (P) element is 4.9 or less.

6 . The solid electrolyte according to claim 1 ,

wherein the halogen (X) element includes a chlorine (Cl) element and a bromine (Br) element.

7 . A method for producing a solid electrolyte, comprising:

a calcination step of calcining a raw material composition at 200° C. or more to obtain a calcined product, the raw material composition containing a lithium (Li) element, a phosphorous (P) element, a sulfur (S) element, and a halogen (X) element; and

a crushing step of crushing the calcined product by applying a crushing energy E represented by the following equation (1) of 200 J·sec/g or more to the calcined product,

E (J·sec/g)=½ntmv 2 /s   (1)

where n represents the number of crushing media, t represents crushing time (sec), m represents the mass (kg) of each of the crushing media, v represents the speed (m/sec) of the crushing media, and s represents the mass (g) of a target to be crushed.

8 . The method according to claim 7 ,

wherein the calcined product is crushed to have a cumulative volume particle size D 50 at 50% cumulative volume obtained using a laser diffraction scattering particle size distribution measurement method of 5 μm or less.

9 . An electrode material mixture comprising:

the solid electrolyte according to claim 1 ; and

an active material.

10 . A solid electrolyte layer comprising:

the solid electrolyte according to claim 1 .

11 . A battery comprising:

a positive electrode layer;

a negative electrode layer; and

a solid electrolyte layer provided between the positive electrode layer and the negative electrode layer,

wherein the battery contains the solid electrolyte according to claim 1 .