A battery cell, comprising: an electrode assembly; a shell assembly, configured to accommodate the electrode assembly and comprising a first side plate and a second side plate, wherein the first side plate and the second side plate are located on two sides of the electrode assembly along a first direction respectively; a pressure relief mechanism, disposed on the first side plate; and a support member, disposed between the electrode assembly and the first side plate, and configured to support the electrode assembly, wherein a duct is provided on the support member, and the duct is configured to guide gas between the second side plate and the support member into the pressure relief mechanism, so that the pressure relief mechanism is actuated to release a pressure when the pressure reaches a threshold; and a first recess is formed on a side that is of the second side plate and that faces the electrode assembly, and the first recess is configured to accommodate at least a part of the electrode assembly; wherein the second side plate comprises an end cap and an insulation piece, the insulation piece is located on a side that is of the end cap and that faces the electrode assembly, and the insulation piece forms the first recess on the side that faces the electrode assembly;and, wherein the insulation piece comprises a first body and a first bulge, the first body comprises a first inner surface and a first outer surface opposite to each other, the first inner surface faces the electrode assembly, the first bulge is disposed protrusively on the first outer surface, and the first recess is formed on a side that is of the first bulge and that faces the electrode assembly, and sinks against the first inner surface; and a fourth recess is formed on a side that is of the end cap and that faces the electrode assembly, and the fourth recess is configured to accommodate the first bulge. an electrode assembly; a shell assembly, configured to accommodate the electrode assembly and comprising a first side plate and a second side plate, wherein the first side plate and the second side plate are located on two sides of the electrode assembly along a first direction respectively; a pressure relief mechanism, disposed on the first side plate; and a support member, disposed between the electrode assembly and the first side plate, and configured to support the electrode assembly, wherein a duct is provided on the support member, and the duct is configured to guide gas between the second side plate and the support member into the pressure relief mechanism, so that the pressure relief mechanism is actuated to release a pressure when the pressure reaches a threshold; and a first recess is formed on a side that is of the second side plate and that faces the electrode assembly, and the first recess is configured to accommodate at least a part of the electrode assembly; wherein the second side plate comprises an end cap and an insulation piece, the insulation piece is located on a side that is of the end cap and that faces the electrode assembly, and the insulation piece forms the first recess on the side that faces the electrode assembly;and, wherein the insulation piece comprises a first body and a first bulge, the first body comprises a first inner surface and a first outer surface opposite to each other, the first inner surface faces the electrode assembly, the first bulge is disposed protrusively on the first outer surface, and the first recess is formed on a side that is of the first bulge and that faces the electrode assembly, and sinks against the first inner surface; and a fourth recess is formed on a side that is of the end cap and that faces the electrode assembly, and the fourth recess is configured to accommodate the first bulge.