Battery monomer and battery

The utility model relates to a single battery and a battery. The single battery comprises a battery unit and an electrode leading-out piece, the battery unit comprises two groups of battery cells which are oppositely arranged, each of the two groups of battery cells comprises a plurality of battery cell monomers which are arranged in a laminated manner, and each battery cell monomer comprises a tab group; the electrode lead-out piece comprises a plurality of connecting parts, and each connecting part is welded with the tab group of at least one battery cell monomer; according to the utility model, the structure that a plurality of tab groups are simultaneously welded with the connecting piece is changed, so that the connecting strength of the tab groups and the connecting part is improved, the risks of cracking and pseudo soldering of the tab groups are reduced, the battery short circuit and safety risk caused by inverted insertion of the tab groups into the electrode assembly are avoided, the welding power i