Positive electrode layer for all-solid secondary battery, all-solid secondary battery including the same, and method of preparing the same

A method of preparing an all-solid secondary battery, the method comprising:

• mixing a positive active material, a binder, a sulfide solid electrolyte, a conducting agent, and a compound represented by Formula 1 to prepare a composition for forming a positive active material layer;
• forming a positive electrode layer by coating and drying the composition for forming a positive active material layer on a positive electrode current collector to form a positive active material layer on the positive electrode current collector;
• providing a negative electrode layer including a negative electrode current collector and a first negative active material layer;
• preparing a stack by providing a solid electrolyte between the negative electrode layer and the positive electrode layer, the solid electrolyte including a sulfide solid electrolyte;
• and
• pressing the stack,
• R1—C(═O)O—R2 Formula 1
• wherein, in Formula 1,
• R1 is a C1-C2 alkyl group, and
• R2 is a C7-C9 alkyl group.

A composition for forming a positive active material layer for an all-solid secondary battery, the composition comprising:

• a positive active material;
• a binder;
• a conducting agent;
• a sulfide solid electrolyte;
• and
• a compound represented by Formula 1,
• R1—C(═O)O—R2 Formula 1
• wherein, in Formula 1,
• R1 is a C1-C2 alkyl group, and
• R2 is a C7-C9 alkyl group.