An insulating film, being configured to wrap a battery assembly, wherein the insulating film comprises a bottom coverage area , N side coverage areas (221-224) and N pairs of bonding areas (231-238), N is an integer greater than 2; the bottom coverage area having N sides (211-214), and the N side coverage areas (221-224) being respectively connected to the bottom coverage area at the N sides (211-214), and can bend toward the bottom coverage area along the N sides (211-214) respectively; each pair of the N pairs of bonding areas (231-238) being located between two adjacent side coverage areas of the N side coverage areas (221-224), and being connected to the two adjacent side coverage areas respectively; each pair of bonding areas is configured to make the bottom coverage area and the N sides coverage areas (221-224) form a space wrapping the battery assembly by bonding surfaces on the same side of each pair of bonding areas when the N sides coverage areas (221-224) bend toward the bottom coverage area ; wherein each pair of bonding areas can respectively bend along the connecting side with the side coverage area to bond the surfaces on the same side of each pair of bonding areas; wherein N is 4, and the insulating film is configured to wrap a cuboid shaped battery assembly; wherein the bottom coverage area and four side coverage areas (221-224) are both rectangular, and the expanded state of the insulating film is a cross shape; wherein in the expanded state of the insulating film, each pair of bonding areas presents as an L shape; characterized in that a width of a first bonding area in each pair of bonding areas is greater than a width of a second bonding area, and after bonding, each pair of bonding areas can bend toward the side coverage area adjacent to the second bonding area, wherein the part that is not bonded with the second bonding area in the first bonding area is configured to bond to the side coverage area adjacent to the second bonding area. the bottom coverage area having N sides (211-214), and the N side coverage areas (221-224) being respectively connected to the bottom coverage area at the N sides (211-214), and can bend toward the bottom coverage area along the N sides (211-214) respectively; each pair of the N pairs of bonding areas (231-238) being located between two adjacent side coverage areas of the N side coverage areas (221-224), and being connected to the two adjacent side coverage areas respectively; each pair of bonding areas is configured to make the bottom coverage area and the N sides coverage areas (221-224) form a space wrapping the battery assembly by bonding surfaces on the same side of each pair of bonding areas when the N sides coverage areas (221-224) bend toward the bottom coverage area ; wherein each pair of bonding areas can respectively bend along the connecting side with the side coverage area to bond the surfaces on the same side of each pair of bonding areas; wherein N is 4, and the insulating film is configured to wrap a cuboid shaped battery assembly; wherein the bottom coverage area and four side coverage areas (221-224) are both rectangular, and the expanded state of the insulating film is a cross shape; wherein in the expanded state of the insulating film, each pair of bonding areas presents as an L shape; characterized in that a width of a first bonding area in each pair of bonding areas is greater than a width of a second bonding area, and after bonding, each pair of bonding areas can bend toward the side coverage area adjacent to the second bonding area, wherein the part that is not bonded with the second bonding area in the first bonding area is configured to bond to the side coverage area adjacent to the second bonding area. <EOS>