Battery monomer, battery, electric equipment and welding method

The invention is suitable for the technical field of power batteries, and provides a battery monomer, a battery, electric equipment and a welding method. The battery monomer comprises a shell, and a pole is arranged on the shell; the electrode assembly is accommodated in the shell, the electrode assembly comprises a plurality of laminated pole pieces, each pole piece comprises a main body part and a tab part extending from the main body part to the pole column, the plurality of tab parts are laminated and form a tab, and the tab is used for electrically connecting the main body part to the pole column; the protection sheet is welded on the tab and forms a first fusion part, the protection sheet is also welded on the pole and forms a second fusion part, and the second fusion part extends into the pole from the protection sheet along the first direction; the projection of the first fusion part on the pole is at least partially overlapped with the projection of the second fusion part on the pole; according to th