All-solid-state battery

An all-solid-state battery comprising:

• a positive electrode layer;
• a separator layer;
• and
• a negative electrode layer,
• wherein the positive electrode layer includes at least one selected from the group consisting of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminate, and lithium iron phosphate,
• the separator layer is interposed between the positive electrode layer and the negative electrode layer,
• the separator layer includes a sulfide solid electrolyte,
• the sulfide solid electrolyte has a composition represented by the following formula (1):
• vLiI-wLiBr-(100-v-w)(Li2S—P2S5) (1)
• in the above formula (1),
• v represents an amount of substance fraction in percentage of a component derived from LiI, and satisfies the relationship of 10≤v≤20,
• w represents an amount of substance fraction in percentage of a component derived from LiBr, and satisfies the relationship of 0≤w≤15, and
• (100-v-w) represents an amount of substance fraction in percentage of a component derived from Li2S—P2S5,
• in a cross section parallel to the thickness direction of the separator layer, a line analysis is performed by a scanning electron microscope-energy dispersive X-ray spectroscopy to measure an atom concentration of sulfur and an atom concentration of iodine on a straight line extending from the negative electrode layer to the positive electrode layer in parallel to the thickness direction,
• from the results of the line analysis, a regression line represented by the following formula (2) is derived:
• y=ax+b (2),
• the regression line has a slope from 0.019 to 0.036,
• in the above formula (2),
• x represents an independent variable,
• x represents a position in the thickness direction, and
• a position of an interface between the separator layer and the negative electrode layer in the thickness direction is defined as x=0, and a position of an interface between the separator layer and the positive electrode layer in the thickness direction is defined as x=1,
• y represents a dependent variable,
• y is a ratio of the atom concentration of iodine to the atom concentration of sulfur at the position x,
• a represents a slope of the regression line, and
• b represents an intercept of the regression line.