COMPOSITE ACTIVE MATERIAL

1 . A composite active material comprising

an active material, and

a surface portion that is disposed on a surface of the active material and that

contains a sulfur-containing compound,

wherein the sulfur-containing compound contains a crystalline phase having an argyrodite-type crystal structure.

2 . The composite active material according to claim 1 , wherein the active material contains a lithium (Li) element and an element M,

wherein the element M is at least one selected from the group consisting of a nickel (Ni) element, a cobalt (Co) element, a manganese (Mn) element, and an aluminum (Al) element, or

the element M comprises a combination of

at least one element selected from the group consisting of a nickel (Ni) element, a cobalt (Co) element, and an aluminum (Al) element, and

at least one element selected from the group consisting of: transition metal elements that are present between Group 3 elements and Group 11 elements on the periodic table; and typical metal elements in Periods 2 to 4 on the periodic table.

3 . The composite active material according to claim 2 , wherein the element M includes at least a nickel (Ni) element, a cobalt (Co) element, and a manganese (Mn) element.

4 . The composite active material according to claim 1 , wherein the active material has a core particle and a coating portion disposed on a surface of the core particle.

5 . The composite active material according to claim 4 , wherein the coating portion contains a lithium (Li) element, an element A, where A is at least one of a titanium (Ti) element, a zirconium (Zr) element, a tantalum (Ta) element, a niobium (Nb) element, and an aluminum (Al) element, and an oxygen (O) element.

6 . The composite active material according to claim 1 , wherein a coverage of the active material by the surface portion is 50% or more and 100% or less.

7 . The composite active material according to claim 1 , wherein a thickness of the surface portion is more than 0 nm and 500 nm or less.

8 . The composite active material according to claim 1 , wherein the sulfur-containing compound contains a lithium (Li) element, a phosphorus (P) element, a sulfur (S) element, and a halogen (X) element.

9 . The composite active material according to claim 8 , wherein the halogen (X) element includes at least a bromine (Br) element.

10 . The composite active material according to claim 8 , wherein an atomic ratio X/P of the halogen (X) element to the phosphorus (P) element is more than 1.0.

11 . The composite active material according to claim 8 , wherein the halogen (X) element includes at least a chlorine (Cl) element and a bromine (Br) element, and an atomic ratio (Cl+Br)/P of the total of the chlorine (Cl) element and the bromine (Br) element to the phosphorus (P) element is more than 1.0.

12 . An electrode material mixture comprising the composite active material according to claim 1 , a solid electrolyte, and a conductive material.

13 . The electrode material mixture according to claim 12 , wherein the solid electrolyte is a material different from the sulfur-containing compound.

14 . A coating composition comprising the electrode material mixture according to claim 12 , a binder, and a solvent.

15 . An electrode comprising the electrode material mixture according to claim 12 and a binder.

16 . A battery comprising a positive electrode layer, a negative electrode layer, and a solid electrolyte layer located between the positive electrode layer and the negative electrode layer,

wherein the positive electrode layer contains the composite active material according to claim 1 .

17 . The battery according to claim 16 ,

wherein the solid electrolyte layer contains a solid electrolyte, and

the sulfur-containing compound and the solid electrolyte are different materials.