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 (X) 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 (X) 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 . <EOS>