Provided are an electrolyte for a sodium secondary battery and a sodium secondary battery using the same. More particularly, the sodium secondary battery includes an anode containing sodium, a cathode containing a transition metal, and a sodium ion conductive solid electrolyte provided between the anode and the cathode, wherein the cathode is impregnated in an electrolyte containing a molten sodium salt and an electrolyte additive, the electrolyte additive including an inorganic sodium salt.

A plate-shaped lithium composite oxide is used as a positive electrode of a lithium ion battery. The plate-shaped lithium composite oxide is composed of a plurality of bound primary particles. The plurality of bound primary particles are respectively constituted by a lithium composite oxide having a layered rock-salt structure. An average number of the primary particles disposed in a thickness direction perpendicular to a plate face is less than or equal to 6.

A lithium and zinc ion bi-polar battery includes, in one example, a plurality of carbon or titanium bi-polar current collectors arranged with cells to form a stack of bi-polar configuration such that each of the bi-polar current collectors is between and in direct contact with a zinc electrode and lithium-ion intercalation electrode of an adjacent pair of the cells.