Positive electrode active material and positive electrode plate for all-solid-state lithium secondary battery, all-solid-state lithium secondary battery, and apparatus

An all-solid-state lithium secondary battery, comprising:

• a positive electrode plate, a negative electrode plate, and a solid-state electrolyte membrane disposed between the positive electrode plate and the negative electrode plate, wherein the positive electrode plate comprises:
• a positive electrode current collector;
• and
• a positive electrode active substance layer disposed on at least one surface of the positive electrode current collector, wherein the positive electrode active substance layer comprises a sulfide solid-state electrolyte and a positive electrode active material,
• wherein the positive electrode active material comprises a positive electrode active substance and a sodium thiosulfate coating layer coating a surface of the positive electrode active substance,
• wherein the sodium thiosulfate coating layer is a continuous amorphous membrane layer on the surface of the positive electrode active substance,
• wherein a mass ratio of element sulfur on a surface of the positive electrode active material to element sulfur in the solid-state electrolyte ranges from 0.06:1 to 0.28:1, and wherein a volume-based median particle size Dv50 of the positive electrode active substance is 3 μm to 20 μm.