A three-dimensional (“3D”) electrode structure includes a current collecting layer, a plurality of plates protruding from the current collecting layer and including an active material, and a base layer provided between the current collecting layer and the plurality of plates. The base layer includes an active material-metal sintered composite. The plurality of plates includes an active material-metal sintered composite. A metal content of the active material-metal sintered composite of the plurality of plates is less than a metal content of the active material-metal sintered composite of the base layer. At least one partition wall supporting the plurality of plates is further provided on the base layer.