Solution for Forming Layer That Contains Solid Electrolyte for All-Solid-State Alkali Metal Secondary Batteries, Coated Active Material Particles, Electrode, All-Solid-State Alkali Metal Secondary Battery and Method for Manufacturing Same

A coated active material particle for a positive electrode and/or a negative electrode of an all-solid-state alkali metal secondary battery, wherein the coated active material particle includes an active material particle and a layer containing a solid electrolyte that coats a surface along an outer shape thereof;

• and the solid electrolyte contains A2S and MxSy (A is selected from Li and Na;
• M is selected from P, Si, Ge, B, Al and Ga;
• and x and y are a number that gives a stoichiometric ratio in accordance with a species of M).

An electrode for an all-solid-state alkali metal secondary battery comprising an assembly of a plurality of active material particles and a layer containing a solid electrolyte that coats a surface along an outer shape of individual active material particles and fills a gap between the active material particles, wherein the solid electrolyte contains A2S and MxSy (A is selected from Li and Na;

• M is selected from P, Si, Ge, B, Al and Ga;
• and x and y are a number that gives a stoichiometric ratio in accordance with a species of M);
• and the electrode is a positive electrode and/or a negative electrode.