All solid battery and manufacturing method of the same

An all solid battery comprising:

• a multilayer structure in which each of a plurality of solid electrolyte layers and each of a plurality of internal electrodes are alternately stacked, each of the plurality of internal electrodes consists of an electrode active material, a solid electrolyte and a conductive auxiliary agent, the multilayer structure having a rectangular parallelepiped shape, the plurality of internal electrodes being alternately exposed at two different faces of the multilayer structure to an outer surroundings of the multilayer structure;
• a first cover layer provided on an upper face of the multilayer structure in a stacking direction;
• and a second cover layer provided on a lower face of the multilayer structure in the stacking direction, wherein each thickness of the plurality of internal electrodes is equal to or more than each thickness of the plurality of solid electrolyte layers, wherein Vickers hardness of the plurality of solid electrolyte layers and Vickers hardness of the first and second cover layers are larger than Vickers hardness of the plurality of internal electrodes, wherein the plurality of solid electrolyte layers, the first cover layer and the second cover layer are made of Li1.3Al0.3Ge1.7(PO4)3, wherein each of the plurality of solid electrolyte layers, the first cover layer and the second cover layer includes a sintering assistant of Li3PO4, and wherein an amount of the sintering assistant in each of the plurality of solid electrolyte layers, the first cover layer and the second cover layer is 0.3 mol % or more and 10 mol % or less.