A secondary battery, comprising: an outer casing, comprising a case and a cap assembly connected to each other, the case is provided with an opening, the cap assembly comprises a cap plate and an electrode terminal connected to the cap plate, wherein the cap plate is adapted to cover the opening; an electrode assembly accommodated in the case and comprising a main body and a tab extending out from the main body, wherein the tab is electrically connected to the electrode terminal; a vent disposed on the cap plate; and an insulating member at least partially disposed between the electrode assembly and the vent, the main body has a first surface facing the vent, and the insulating member comprises a main cover body covering at least a portion of the first surface, the electrode assembly comprises two tabs, each of which extends from the first surface toward the cap plate, the main cover body comprises a first cover member and a second cover member, the first surface has a center line dividing the first surface into a first region and a second region disposed opposite to each other in a thickness direction of the electrode assembly, and the two tabs are disposed in the first region and bent toward the second region in the thickness direction, wherein the first cover member is adapted to at least cover the second region, and the second cover member is adapted to at least cover the first region, and the first cover member and the second cover member are independently formed, wherein the secondary battery further comprises connecting pieces, and two connecting pieces in pairs are located between the cap plate and the electrode assembly, wherein each of the connecting pieces comprises a terminal connection portion connected to the electrode terminal and a tab connection portion connected to the tab; and the second cover member is further adapted to cover a surface of the tab connection portion facing the cap plate, and a portion of the second cover member located between the two connecting pieces in a length direction of the electrode assembly is connected to the first cover member, wherein a projection of the vent on the first surface is at least partially covered by the insulating member. an outer casing, comprising a case and a cap assembly connected to each other, the case is provided with an opening, the cap assembly comprises a cap plate and an electrode terminal connected to the cap plate, wherein the cap plate is adapted to cover the opening; an electrode assembly accommodated in the case and comprising a main body and a tab extending out from the main body, wherein the tab is electrically connected to the electrode terminal; a vent disposed on the cap plate; and an insulating member at least partially disposed between the electrode assembly and the vent, the main body has a first surface facing the vent, and the insulating member comprises a main cover body covering at least a portion of the first surface, the electrode assembly comprises two tabs, each of which extends from the first surface toward the cap plate, the main cover body comprises a first cover member and a second cover member, the first surface has a center line dividing the first surface into a first region and a second region disposed opposite to each other in a thickness direction of the electrode assembly, and the two tabs are disposed in the first region and bent toward the second region in the thickness direction, wherein the first cover member is adapted to at least cover the second region, and the second cover member is adapted to at least cover the first region, and the first cover member and the second cover member are independently formed, wherein the secondary battery further comprises connecting pieces, and two connecting pieces in pairs are located between the cap plate and the electrode assembly, wherein each of the connecting pieces comprises a terminal connection portion connected to the electrode terminal and a tab connection portion connected to the tab; and the second cover member is further adapted to cover a surface of the tab connection portion facing the cap plate, and a portion of the second cover member located between the two connecting pieces in a length direction of the electrode assembly is connected to the first cover member, wherein a projection of the vent on the first surface is at least partially covered by the insulating member.