A top cap structure for a power battery is provided. The power battery top cap structure includes a first and second electrode assemblies, and a top cap piece. The first electrode assembly includes a first electrode column having an upper and lower sections, a first seal member and a first connection block. The upper section and the first connection block are formed from a first base metal. The lower section is formed from a second base metal different from the first base metal. The upper section includes a step portion, and the lower section is joined with a bottom surface of the upper section below the top cap piece. The first seal member includes a horizontal extending portion. The horizontal extending portion is disposed between a lower surface of the top cap piece and the step portion. The top portion of the upper section connects with the first connection block.