Solid-state battery

A solid-state battery comprising:

• a negative electrode layer including a negative electrode active material;
• a positive electrode layer;
• and
• a solid electrolyte layer positioned between the positive electrode layer and the negative electrode layer, wherein
• the negative electrode active material includes:
• graphite particles, each of which is an aggregate of a plurality of primary particles including graphite and has a void inside;
• and
• a solid electrolyte disposed inside the void of each of the graphite particles, the graphite particles have a median size of 300 nm or more and 30 μm or less, at least a portion of the void is filled with the solid electrolyte,
• the void has a minimum diameter of 1 nm or more and 70 nm or less, and
• wherein an outer surface of each of the graphite particles is partially covered by a solid electrolyte made of a same material as the solid electrolyte disposed inside the void of each of the graphite particles with a coating rate of 10% or less, and the coating rate is determined by:
• observing the outer surface of each of the graphite particles using a scanning electron microscope to obtain an image;
• calculating by using image processing on the image, a first area of each of the graphite particles and a second area of the solid electrolyte;
• and
• calculating a ratio of the second area to the first area as the coating rate.