A battery includes a positive electrode, a negative electrode, and an electrolyte layer disposed between the positive electrode and the negative electrode. The electrolyte layer includes a first layer, a second layer, and a mixture layer disposed between the first layer and the second layer. The first layer includes a first solid electrolyte material. The second layer includes a second solid electrolyte material, the second solid electrolyte material being different from the first solid electrolyte material. The mixture layer includes the first solid electrolyte material and the second solid electrolyte material.