Secondary battery and preparation method thereof, energy storage system and power utilization device

Abstract

The invention relates to the technical field of energy storage, and discloses a secondary battery and a preparation method thereof, an energy storage system and an electric device. The secondary battery comprises a shell and a battery cell assembly, the shell comprises a first shell body and a second shell body which are connected. The first shell is provided with a containing cavity and an opening communicated with the containing cavity, and the second shell seals the opening. The first shell comprises a bottom wall and a plurality of side walls which define a containing cavity on the bottom wall, and the area of the surface, facing the containing cavity, of the bottom wall is larger than that of the surface, facing the containing cavity, of any side wall. And the second shell is provided with a negative pole insulated from the second shell. And the battery core assembly is arranged in the accommodating cavity. The battery cell assembly comprises a positive pole piece, a negative pole piece and a diaphragm for separating the positive pole piece from the negative pole piece, the positive pole piece is provided with a positive pole lug, and the negative pole piece is provided with a negative pole lug. According to the secondary battery and the preparation method thereof, the energy storage system and the power utilization device provided by the invention, the working performance of the secondary battery can be improved.

Description

Technical Field

[0001] This application relates to the technical field of energy storage, and particularly relates to a secondary battery, a preparation method thereof, an energy storage system, and an electrical device. Background Art

[0002] With the continuous development of new energy technologies, the demand for energy storage systems is also increasing. An energy storage system can effectively store electrical energy and output the electrical energy when needed externally. The energy storage system uses a secondary battery as an energy storage unit. The secondary battery has good charge and discharge cycle characteristics and can form an electrochemical energy storage system with a wide range of applications.

[0003] As an important part of the energy storage system, the secondary battery affects the performance of the energy storage system. In particular, as the energy storage unit of the energy storage system, the working performance of the secondary battery determines the amount of electrical energy that the energy storage system can store and the charge and discharge efficiency. Therefore, how to design the structure of the secondary battery to improve its working performance is an important issue. Summary of the Invention

[0004] The purpose of the embodiments of this application is to provide a secondary battery, a preparation method thereof, an energy storage system, and an electrical device, which can help improve the working performance of the secondary battery.

[0005] To solve the above technical problems, the embodiments of this application provide a secondary battery. The secondary battery includes a housing and a core component. The housing includes a first housing and a second housing connected to each other. The first housing is provided with a receiving cavity and an opening communicating with the receiving cavity, and the second housing closes the opening. The first housing includes a bottom wall and a plurality of side walls surrounding the receiving cavity on the bottom wall. The area of the surface of the bottom wall facing the receiving cavity is larger than the area of the surface of any side wall facing the receiving cavity. The second housing is provided with a negative electrode post insulated from the second housing. The core component is disposed in the receiving cavity. The core component includes a positive electrode plate, a negative electrode plate, and a separator separating the positive electrode plate and the negative electrode plate. The positive electrode plate is provided with a positive electrode tab, and the negative electrode plate is provided with a negative electrode tab. The core component includes a first surface and a second surface disposed opposite to each other, and a third surface connecting the first surface and the second surface. The first surface faces the bottom wall, and the second surface faces the second housing. The positive electrode tab is bent and extended from the third surface to the first surface, and the negative electrode tab is bent and extended from the third surface to the second surface. The part of the positive electrode tab extending to the first surface is connected to the bottom wall, and the part of the negative electrode tab extending to the second surface is connected to the negative electrode post.

[0006] The embodiments of this application also provide a preparation method of a secondary battery. The preparation method of the secondary battery includes: Provide a housing, which includes a first housing and a second housing. The first housing is provided with a receiving cavity and an opening communicating with the receiving cavity. The first housing includes a bottom wall and a plurality of side walls surrounding the receiving cavity on the bottom wall. The area of the surface of the bottom wall facing the receiving cavity is larger than the area of the surface of any side wall facing the receiving cavity. The second housing is provided with a negative electrode post insulated from the second housing; Manufacture an electric core assembly, and bend and extend the positive electrode tab on the top surface of the electric core assembly to the first side surface, and bend and extend the negative electrode tab on the top surface of the electric core assembly to the second side surface; Place the electric core assembly in the receiving cavity, make the first side surface of the electric core assembly face the bottom wall, and connect the part of the positive electrode tab extending to the first side surface to the bottom wall, and connect the part of the negative electrode tab extending to the second side surface to the negative electrode post; Connect the first housing and the second housing to seal the opening with the second housing.

[0007] An embodiment of the present application also provides an energy storage system, which includes a box body and a battery module. The box body is provided with an inner cavity. The battery module is arranged in the inner cavity, and the battery module includes a plurality of the above-mentioned secondary batteries.

[0008] An embodiment of the present application also provides an electrical device, which includes the above-mentioned energy storage system.

[0009] The secondary battery, its preparation method, energy storage system, and electrical device provided by the embodiment of the present application form a packaging shell of the secondary battery through the cooperation of the first housing and the second housing. The bottom wall of the first housing and the second housing correspond to the part of the packaging shell that occupies a large space, and the larger surface of the electric core assembly faces the bottom wall and the second housing respectively. At the same time, the positive electrode tab of the electric core assembly is bent and extended to the first surface and forms a connection relationship with the bottom wall. The negative electrode tab of the electric core assembly is bent and extended to the second surface and forms a connection relationship with the negative electrode post provided on the second housing. Thereby, the structure of the secondary battery is simplified, and the influence of the complex manufacturing process on the working performance of the secondary battery is reduced. Moreover, the use of ear connection pieces is reduced, the installation space formed by the cooperation of different housings can be effectively utilized, the capacity of the secondary battery is increased, and the working performance of the secondary battery is further improved. Description of the Drawings

[0010] One or more embodiments are exemplarily illustrated by the pictures in the corresponding drawings. These exemplary illustrations do not limit the embodiments. Elements with the same reference numerals in the drawings are represented as similar elements. Unless otherwise stated, the drawings in the drawings do not constitute a proportional limitation.

[0011] Figure 1 It is a three-dimensional structure schematic diagram of a secondary battery provided by some embodiments of the present application; Figure 2It is a schematic three-dimensional structure diagram of a secondary battery provided by some embodiments of the present application from another perspective; Figure 3 It is an exploded structure diagram of a secondary battery provided by some embodiments of the present application; Figure 4 It is an exploded structure diagram of a secondary battery provided by some embodiments of the present application from another perspective; Figure 5 It is a rear view structure diagram of a secondary battery provided by some embodiments of the present application; Figure 6 It is along Figure 5 The sectional structure diagram in the A-A direction in; Figure 7 It is Figure 6 The enlarged structure diagram at B in; Figure 8 It is Figure 6 The enlarged structure diagram at C in; Figure 9 It is an internal structure diagram of a secondary battery provided by some embodiments of the present application; Figure 10 It is a structure diagram of the second housing in a secondary battery provided by some embodiments of the present application; Figure 11 It is along Figure 10 The sectional structure diagram in the D-D direction in; Figure 12 It is Figure 11 The enlarged structure diagram at E in; Figure 13 It is a matching structure diagram of a cell assembly and a second insulating film in a secondary battery provided by some embodiments of the present application; Figure 14 It is Figure 13 The enlarged structure diagram at F in; Figure 15 It is a matching structure diagram of a cell assembly and a second insulating film in a secondary battery provided by some embodiments of the present application from another perspective; Figure 16 It is Figure 15 The enlarged structure diagram at G in; Figure 17 It is a matching structure diagram of a second insulating film and a cell assembly when the second insulating film is unfolded in a secondary battery provided by some embodiments of the present application; Figure 18 It is a structure diagram when a second insulating film wraps a cell assembly in a secondary battery provided by some embodiments of the present application; Figure 19 It is a schematic three-dimensional structure diagram of a plastic part in a secondary battery provided by some embodiments of the present application; Figure 20 It is a schematic perspective view of a plastic part in a secondary battery provided by some embodiments of the present application from another perspective; Figure 21 It is a schematic structural view when the secondary batteries provided by some embodiments of the present application are assembled into a battery module; Figure 22 It is a flowchart of a preparation method of a secondary battery provided by some embodiments of the present application. Detailed implementation manners

[0012] To make the objectives, technical solutions, and advantages of the embodiments of the present application clearer, the following will elaborate on each implementation manner of the present application with reference to the accompanying drawings. However, those of ordinary skill in the art can understand that in each implementation manner of the present application, many technical details are presented for readers to better understand the present application. However, even without these technical details and various changes and modifications based on the following implementation manners, the technical solutions claimed in the present application can still be achieved. The division of the following embodiments is for convenience of description and should not constitute any limitation to the specific implementation manners of the present application. The various embodiments can be combined and cross-referenced with each other on the premise of no contradiction.

[0013] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in the specification and claims of this application and the above drawings are intended to cover non-exclusive inclusion.

[0014] In the description of the embodiments of the present application, unless otherwise clearly specified and limited, technical terms such as "installation", "connection", and "coupling" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral body; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the internal communication of two components or the interaction relationship between two components. For those of ordinary skill in the art, the specific meanings of the above terms in the embodiments of the present application can be understood according to specific circumstances.

[0015] As the sources of energy become more and more extensive, the importance of energy storage is also increasing day by day. The electrochemical energy storage system formed by secondary batteries is a relatively common energy storage system. For example, the energy storage systems formed by lithium batteries can be seen everywhere in industrial production and daily life. Lithium batteries have the characteristics of high energy density, long single-cell cycle life, high efficiency, cleanliness, and no pollution, so they have been widely used. In particular, square lithium batteries have relatively high structural strength and high energy density at the same time. At the same time, the structure of square lithium batteries is relatively simple, and it is relatively convenient to expand the capacity. It is an important option to improve the energy density by increasing the capacity of a single battery at present.

[0016] At present, secondary batteries generally adopt a structural form in which a bottom case and a top cover are matched to form a square packaging shell, and the top cover is packaged on the top of the battery cell assembly. At the same time, the positive and negative electrode tabs of the battery cell assembly are folded and welded on the positive and negative connection sheets at the top of the bare battery cell, and then welded on the top cover. Structures such as positive and negative electrode posts and explosion-proof valves are provided on the top cover. In the production and assembly process of square secondary batteries, the positive electrode tab and the negative electrode tab of the battery cell assembly need to be welded to the positive electrode post and the negative electrode post on the top cover respectively, and then the top cover and the housing are welded. This design requires a lot of connection sheet parts and welding operations, and there is a certain height after the electrode post and the connection sheet are welded, which will occupy a certain space. As a result, the structure of the secondary battery is complex and the manufacturing difficulty is high. Connecting the circuit by welding the connection sheet on the protruding electrode tab of the battery cell assembly is also prone to problems such as poor welding, which affects the welding quality and the stability of later use. At the same time, too many connection sheets also increase the material cost and occupy space, which is not conducive to increasing the capacity of a single battery.

[0017] In order to improve the working performance of secondary batteries, some embodiments of the present application provide a secondary battery. The secondary battery selects the side with a larger surface area of the packaging shell as the entrance when packaging the battery cell assembly. At the same time, the electrode tab part of the battery cell assembly is bent to the two side surfaces with a larger area of the bare battery cell. The positive electrode tab of the battery cell assembly can be directly welded to the housing part, and the housing part is used as the positive electrode structure of the secondary battery, carrying a positive potential. The cover part can be provided with a negative electrode post to be welded to the negative electrode tab of the battery cell assembly. Thereby simplifying the structure of the secondary battery and reducing the impact on the working performance caused by the complex manufacturing process of the secondary battery. At the same time, the installation space in the packaging shell can be effectively utilized, the capacity of the battery single body can be increased, and thus the working performance of the secondary battery can be improved.

[0018] The following combines Figures 1 to 21 to illustrate the structure of the secondary battery provided by some embodiments of the present application.

[0019] As Figures 1 to 21As shown in the figure, the secondary battery 10 provided by some embodiments of the present application includes a housing 11 and a battery cell assembly 12. The housing 11 includes a first housing 111 and a second housing 112 connected to each other. The first housing 111 is provided with a receiving cavity 101 and an opening 102 communicating with the receiving cavity 101, and the second housing 112 closes the opening 102. The first housing 111 includes a bottom wall 1111 and a plurality of side walls 1112 surrounding the receiving cavity 101 on the bottom wall 1111. The area of the surface of the bottom wall 1111 facing the receiving cavity 101 is larger than the area of the surface of any side wall 1112 facing the receiving cavity 101. The second housing 112 is provided with a negative electrode terminal 113 insulated from the second housing 112.

[0020] The battery cell assembly 12 is disposed in the receiving cavity 101. The battery cell assembly 12 includes a positive electrode plate, a negative electrode plate, and a separator separating the positive electrode plate and the negative electrode plate. The positive electrode plate is provided with a positive electrode tab 121, and the negative electrode plate is provided with a negative electrode tab 122. The battery cell assembly 12 includes a first surface 123 and a second surface 124 disposed opposite to each other, and a third surface 125 connecting the first surface 123 and the second surface 124. The first surface 123 faces the bottom wall 1111, and the second surface 124 faces the second housing 112. The positive electrode tab 121 is bent and extended from the third surface 125 to the first surface 123, and the negative electrode tab 122 is bent and extended from the third surface 125 to the second surface 124. The portion of the positive electrode tab 121 extending to the first surface 123 is connected to the bottom wall 1111, and the portion of the negative electrode tab 122 extending to the second surface 124 is connected to the negative electrode terminal 113.

[0021] The housing 11 forms the encapsulation part of the secondary battery 10 and can provide an installation space for the battery cell assembly 12. Moreover, the housing 11 has a high mechanical strength and can play a protective role for the components installed inside. The housing 11 includes a first housing 111 providing the installation space and a second housing 112 cooperating with the first housing 111. The first housing 111 and the second housing 112 are connected to form a square outer shell of the secondary battery 10. Figures 1 to 4 In the first housing 111, the four side walls 1112 surround the bottom wall 1111 to form a receiving cavity 101 with an opening 102 on one side. In actual situations, the number of side walls 1112 of the first housing 111 can also be less than four or more than four to form a quasi-square outer shell. Or a plurality of receiving cavities 101 are separated by some side walls 1112 inside the first housing 111. The first housing 111 and the second housing 112 can be made of aluminum.

[0022] The first housing 111 forms an accommodation cavity 101 through the cooperation of different parts. The bottom wall 1111 is a part of the first housing 111 that occupies a relatively large space, and it cooperates with the second housing 112 to form two sides of the encapsulation housing that occupy a relatively large space. The side walls 1112 are arranged around the bottom wall 1111 to form a square contour. The surfaces of the bottom wall 1111 and the second housing 112 that are away from each other form two relatively large surfaces of the encapsulation housing of the secondary battery 10, and the surfaces of the side walls 1112 that are away from the accommodation cavity 101 form relatively small surfaces of the encapsulation housing of the secondary battery 10.

[0023] The cell assembly 12 is the part of the secondary battery 10 that cooperates with the electrolyte to achieve electrochemical energy storage. During the charge and discharge process of the secondary battery 10, lithium ions can move between the positive electrode plate and the negative electrode plate. The cell assembly 12 uses different electrode plates and separators to form a bare cell through a winding process or a stacking process, and the formed bare cell is the cell assembly 12. For example, Figure 17 and Figure 18 the bare cell shown in is a bare cell formed by a wound core structure.

[0024] In the bare cell, the positive electrode plate leads out the positive electrode tab 121, and the negative electrode plate leads out the negative electrode tab 122. The first surface 123 and the second surface 124 are two relatively large sides of the bare cell, and the third surface 125 is the surface of the bare cell where different tabs are led out and is also the top surface of the bare cell. The positive electrode tab 121 led out on the third surface 125 bends and extends towards the first surface 123, and the negative electrode tab 122 bends and extends towards the second surface 124. This provides favorable conditions for the connection between the bare cell and different housings. In actual situations, there may be a gap between the positive electrode tab 121 and the first surface 123 of the bare cell, or it may be attached to the first surface 123. There may be a gap between the negative electrode tab 122 and the second surface 124 of the bare cell, or it may be attached to the second surface 124.

[0025] In some embodiments of the present application, the secondary battery 10 is formed by the cooperation of the first housing 111 and the second housing 112 to form the packaging housing of the secondary battery 10. The bottom wall 1111 of the first housing 111 and the second housing 112 correspond to the parts of the packaging housing that occupy a relatively large space, and the larger surfaces of the battery cell assembly 12 face the bottom wall 1111 and the second housing 112 respectively. At the same time, the positive electrode tab 121 of the battery cell assembly 12 is bent and extended to the first surface 123, and forms a connection relationship with the bottom wall 1111. The negative electrode tab 122 of the battery cell assembly 12 is bent and extended to the second surface 124, and forms a connection relationship with the negative electrode terminal 113 provided on the second housing 112. Thereby, the structure of the secondary battery 10 is simplified, and the influence of the complex manufacturing process of the secondary battery 10 on its working performance is reduced. Moreover, the use of ear connection pieces is reduced, the installation space formed by the cooperation of different housings can be effectively utilized, the capacity of the secondary battery 10 is increased, and thus the working performance of the secondary battery 10 is improved.

[0026] In some embodiments, the secondary battery 10 may further include a first insulating film 13. The first insulating film 13 includes a main body portion 131, a first extending portion 132, and a second extending portion 133 that are integrally provided. The main body portion 131 is disposed around the battery cell assembly 12 along the edge of the third surface 125 from the first surface 123 of the battery cell assembly 12. The first extending portion 132 covers the third surface 125, and the second extending portion 133 covers the surface of the battery cell assembly 12 facing away from the third surface 125.

[0027] The first insulating film 13 is the part that wraps the battery cell assembly 12, which can effectively seal and protect the bare battery cell and isolate the bare battery cell from the housing 11. The first insulating film 13 is encapsulated outside the battery cell assembly 12. The main body portion 131 is the part that wraps around the periphery of the bare battery cell, and the first extending portion 132 and the second extending portion 133 are the parts that wrap around the two end faces of the bare battery cell. Through the cooperation between different parts, the battery cell assembly 12 can be effectively wrapped. In actual situations, the first insulating film 13 can be made of a polyester film, such as a Mylar film. By using a Mylar film that forms a complete enclosure for the bare battery cell, the safety performance inside the secondary battery 10 can be improved. Moreover, the Mylar film can be formed into an integral structure by laminating and hot melting welding, and the bare battery cell is accommodated therein. The Mylar film may not be welded to the plastic part, which is the part located below the top cover in the secondary battery and insulates the ear connection structure, the battery cell assembly 12 and the top cover of the packaging housing, and is also called the lower plastic. After the structure of the housing 11 is changed, the plastic part 15 no longer cooperates with the cover part, but plays an insulating role between the ear connection structure, the battery cell assembly 12 and the side wall 1112 of the first housing 111. Moreover, the plastic part 15 prevents the battery cell assembly 12 from moving around in the first housing 111.

[0028] The first insulating film 13 wrapping the bare battery cell has a first hollowed-out area 134 and a second hollowed-out area 135. The first hollowed-out area 134 is arranged facing the first surface 123 of the bare battery cell and exposes a part of the positive electrode tab 121. The second hollowed-out area 135 is arranged facing the second surface 124 of the bare battery cell and exposes a part of the negative electrode tab 122. The first hollowed-out area 134 is used to provide an avoidance channel for forming a connection between the positive electrode tab 121 and the bottom wall 1111, and the second hollowed-out area 135 is used to provide an avoidance channel for forming a connection between the negative electrode tab 122 and the second housing 112.

[0029] As Figures 13 to 16 shown, the first extension part 132 may include a first edge 1321 and a second edge 1322 which are oppositely arranged. The first edge 1321 is integrally provided with the main body part 131, and there is a gap at a part of the connection between the first edge 1321 and the main body part 131, forming the first hollowed-out area 134 for the positive electrode tab 121 to pass through. A part of the second edge 1322 is arranged at an interval from the edge of the main body part 131, forming the second hollowed-out area 135 for the negative electrode tab 122 to pass through.

[0030] The first edge 1321 and the second edge 1322 are two edges with a longer length of the first extension part 132, corresponding to the two edges of the top surface of the bare battery cell in the thickness direction. The first edge 1321 is integrally formed with the main body part 131. And there is a gap at a part of the connection between the first edge 1321 and the main body part 131, and the position of the gap corresponds to the part where the positive electrode tab 121 extends to the first surface 123, forming the first hollowed-out area 134 that exposes a part of the positive electrode tab 121. The part of the positive electrode tab 121 extending to the first surface 123 can pass through the first hollowed-out area 134 and is located on the side of the first insulating film 13 away from the battery cell assembly 12.

[0031] The second edge 1322 faces the main body part 131 after the first extension part 132 is folded to cover the top surface of the bare battery cell. And there is a reserved gap between a part of the second edge 1322 and the main body part 131, and the position of the gap corresponds to the part where the negative electrode tab 122 extends to the second surface 124, forming the second hollowed-out area 135 that exposes a part of the negative electrode tab 122. The part of the negative electrode tab 122 extending to the second surface 124 can pass through the second hollowed-out area 135 and is located on the side of the first insulating film 13 away from the battery cell assembly 12.

[0032] In addition, a part of the second edge 1322 is bent to cover the side of the main body part 131 away from the second surface 124 and is fixed on the main body part 131. At least part of the edge of the first extension part 132 is bent to cover the side of the main body part 131 away from the second surface 124 and is fixed on the main body part 131.

[0033] After the first extension part 132 and the second extension part 133 fold to cover the end face of the bare battery cell, they can be connected to the main body part 131. The two side edges of the main body part 131 after surrounding the battery cell assembly 12 for one week can also overlap and be fixed by hot melting. Thus, the wrapping shape of the first insulating film 13 outside the bare battery cell is fixed. A part of the second edge 1322 of the first extension part 132 bends towards the second surface 124 of the bare battery cell to cover the side of the main body part 131 away from the second surface 124. A mutually overlapping part is formed between the first extension part 132 and the main body part 131, and a part of the second edge 1322 of the first extension part 132 can be fixed on the main body part 131 by forms such as hot melting or bonding.

[0034] At least part of the edge of the second extension part 133 also bends towards the second surface 124 of the bare battery cell to cover the side of the main body part 131 away from the second surface 124. A mutually overlapping part is formed between the second extension part 133 and the main body part 131, and a part of the edge of the second extension part 133 can be fixed on the main body part 131 by forms such as hot melting or bonding.

[0035] Figure 17 The cooperation structure of the first insulating film 13 and the battery cell assembly 12 in the unfolded state is schematically shown. Figure 18 The cooperation structure of the first insulating film 13 and the battery cell assembly 12 in the partially folded state is schematically shown. As Figure 17 shown, a first hollowed-out area 134 is provided at the position corresponding to the top surface edge of the battery cell assembly 12 at the folding demarcation position between the main body part 131 and the first extension part 132 to avoid the positive electrode tab 121. At the same time, a first notch 1311 is provided at the edge of the main body part 131 extending out of the folding demarcation position, and a second notch 1323 is provided at the second edge 1322 of the first extension part 132. After the first insulating film 13 completes the folding process, the positions where the first notch 1311 and the second notch 1323 are located correspond to form a second hollowed-out area 135 to avoid the negative electrode tab 122.

[0036] As Figure 3 and Figure 4 shown, the secondary battery 10 may further include a second insulating film 14. The second insulating film 14 wraps the housing 11. The second insulating film 14 is provided with a first through hole 141 and a second through hole 142. The first through hole 141 faces the bottom wall 1111 and exposes a part of the bottom wall 1111, and the second through hole 142 faces the second housing 112 and exposes the negative electrode terminal 113.

[0037] The second insulating film 14 is a protective film for the surface of the housing 11, which can serve as an insulating material between the secondary batteries 10, and can play a good protective role for the secondary batteries 10, preventing a single secondary battery 10 from having an adverse impact on other secondary batteries 10 due to various faults. The second insulating film 14 can be made of a polyester film, such as a PET blue film. In actual situations, by wrapping a blue film on the outside of the housing 11, and leaving a Figure 7 shown positive electrode welding position 103 through the hollowed-out area corresponding to the bottom wall 1111 on the blue film. The reserved positive electrode welding position 103 is used to replace the use of the positive electrode post, forming the positive electrode structure of the secondary battery 10. The positive electrode welding position 103 can be connected to the positive electrode structure or the negative electrode structure of other secondary batteries 10. For example, when connecting multiple secondary batteries 10 in series, only need to make the negative electrode post 113 of one secondary battery 10 abut against the positive electrode welding position 103 of another secondary battery 10, and then form a connection through laser welding, so as to realize the series assembly of multiple secondary batteries 10.

[0038] In order to expose the positive and negative electrodes of the secondary battery 10 and facilitate the connection between the secondary battery 10 and the outside world, when the second insulating film 14 wraps the housing 11, it also has through holes for exposing the positive and negative electrode structures. The first through hole 141 forms an avoidance for the positive electrode structure, and the second through hole 142 forms an avoidance for the negative electrode structure. The first through hole 141 is arranged facing the bottom wall 1111, and the part of the bottom wall 1111 exposing the first through hole 141 forms the positive electrode structure of the secondary battery 10. The second through hole 142 is arranged facing the second housing 112, exposing the negative electrode post 113 on the second housing 112, and the negative electrode post 113 forms the negative electrode structure of the secondary battery 10.

[0039] In some embodiments, the negative electrode post 113 can be arranged adjacent to the edge of the second housing 112, and the first through hole 141 and the second through hole 142 are coaxially arranged in the direction of the opening 102 of the first housing 111.

[0040] That is to say, the negative electrode post 113 is arranged close to the edge of the second housing 112. When multiple secondary batteries 10 are arranged in sequence to form a battery module, the negative electrode post 113 of the previous secondary battery 10 can be correspondingly connected to the part of the bottom wall 1111 of the next secondary battery 10 that exposes the second insulating film 14. By arranging the negative electrode post 113 adjacent to the edge of the second housing 112, it is convenient to connect the negative electrode post 113 of one secondary battery 10 with the bottom wall 1111 forming the positive electrode structure of an adjacent secondary battery 10.

[0041] Meanwhile, the first through hole 141 and the second through hole 142 on the second insulating film 14 are coaxially arranged, and there is a positional correspondence between them. When connecting two secondary batteries 10 in series, it is convenient to keep the positions of the two secondary batteries 10 consistent and in an aligned state on the same plane. When arranging multiple secondary batteries 10 regularly, the position between the negative electrode terminal 113 of one secondary battery 10 and the bottom wall 1111 of the adjacent secondary battery 10 exposed from the second insulating film 14 can be aligned. Thus, it is convenient to connect multiple secondary batteries 10 in series to form a battery module. As Figure 21 shown, multiple secondary batteries 10 can be arranged in sequence along the same direction. The bottom wall 1111 of the previous secondary battery 10 exposed from the first through hole 141 to form the positive electrode welding position 103 can be welded to the negative electrode terminal 113 of the next secondary battery 10 exposed from the second through hole 142, thereby forming a battery module connected in series.

[0042] In actual situations, the distance between the negative electrode terminal 113 and the edge of the second housing 112 can be controlled between 10 millimeters and 20 millimeters. The negative electrode terminal 113 can be located within the region of 90% to 95% in the height direction of the second housing 112.

[0043] In addition, one of the multiple side walls 1112 can be provided with an explosion-proof valve 114, and the second insulating film 14 is provided with a third through hole 143, and the third through hole 143 faces the side wall 1112 and exposes the explosion-proof valve 114.

[0044] The explosion-proof valve 114 can be formed by a thickness-reduced area on the side wall 1112, or formed by scribing on the side wall 1112, or formed by connecting an explosion-proof sheet on the side wall 1112. The explosion-proof valve 114 can timely release the pressure inside the housing 11 to protect the secondary battery 10. The explosion-proof valve 114 is provided on the side wall 1112 of the first housing 111. When the secondary battery 10 is assembled into a battery module, the side wall 1112 faces the outside of the battery module. It can ensure that the explosion-proof valve 114 will not be blocked by adjacent secondary batteries 10.

[0045] The second insulating film 14 is provided with a third through hole 143 that avoids the explosion-proof valve 114, so that the explosion-proof valve 114 can be exposed. The third through hole 143 faces the side wall 1112, which can avoid affecting the normal protection function of the explosion-proof valve 114.

[0046] As Figure 9 shown, the secondary battery 10 can further include a plastic part 15, and the plastic part 15 is arranged in the accommodation cavity 101. As Figure 19 and Figure 20As shown, the plastic part 15 includes a first abutting surface 151 and a second abutting surface 152 which are oppositely arranged. The first abutting surface 151 abuts against the housing 11, and the second abutting surface 152 abuts against the battery cell assembly 12.

[0047] The plastic part 15 is arranged in the housing 11 and abuts against the battery cell assembly 12 and the housing 11 respectively, and can limit the position of the battery cell assembly 12 in the accommodation cavity 101 of the housing 11. The movement of the battery cell assembly 12 in the accommodation cavity 101 is restricted, and the position of the bare battery cell in the housing 11 is fixed, ensuring the stability of the secondary battery 10 during use.

[0048] As Figure 19 and Figure 20 shown, a through hole 153 can be arranged on the plastic part 15 so that the electrolyte can pass through. And, grooves 154 and clamping grooves 155 can be respectively arranged on both sides of the plastic part 15. The groove 154 located on the second abutting surface 152 can provide an accommodation space for the positive electrode tab 121 and the negative electrode tab 122, avoiding adverse effects such as mechanical damage to the tabs. The clamping groove 155 can facilitate the clamping of the plastic part 15 by the tooling, and then the plastic part 15 is loaded into the accommodation cavity 101 of the housing 11.

[0049] Some embodiments of the present application also provide a preparation method for the secondary battery 10. As Figure 22 shown, the preparation method for the secondary battery 10 includes the following steps: Step S110: Provide the housing 11. The housing 11 includes a first housing 111 and a second housing 112. The first housing 111 is provided with an accommodation cavity 101 and an opening 102 communicating with the accommodation cavity 101. The first housing 111 includes a bottom wall 1111 and a plurality of side walls 1112 surrounding the accommodation cavity 101 on the bottom wall 1111. The area of the surface of the bottom wall 1111 facing the accommodation cavity 101 is larger than the area of the surface of any side wall 1112 facing the accommodation cavity 101. The second housing 112 is provided with a negative electrode terminal 113 insulated from the second housing 112.

[0050] The housing 11 is the basis for installing other components of the secondary battery 10. Compared with the housing 11 formed by combining a common bottom case and a top cover, some embodiments of the present application use a side case and a side cover to form the housing 11. In the prior art, two relatively large surfaces of the square packaging shell of the secondary battery 10 are both formed on the bottom case. The bottom case has a relatively large stretching length and a relatively large space depth inside, which is not conducive to saving material costs and is not conducive to the installation of the battery cell assembly 12.

[0051] The height of the first housing 111 that forms the side housing is stretched from the original height of the battery cell assembly 12 to the thickness of the battery cell assembly 12. Therefore, the difficulty decreases, and the overall mold manufacturing cost and maintenance cost etc. decrease accordingly. Since the side housing form has a smaller stretching length, metal aluminum with a thinner thickness can be used for stretching production, which can save material costs and increase the internal space of the housing 11. At the same time, the depth of the accommodation cavity 101 in the side housing is smaller, which is convenient for loading the battery cell assembly 12. The two wall parts of the housing 11 that occupy a larger space are respectively formed in the first housing 111 and the second housing 112. The first housing 111 can directly form the positive electrode structure of the secondary battery 10, and the second housing 112 can be provided with a negative electrode terminal 113 to form the negative electrode structure of the secondary battery 10. The positive and negative electrode structures are arranged on the two large surfaces with a larger area of the packaging housing. The positive and negative electrode tabs are folded outwards towards the outside of the bare battery cell. The first housing 111 can have a smaller stretching length in the orientation direction of the opening 102. Structures such as an explosion-proof valve 114 welding hole and a liquid injection hole can be provided on the side wall 1112 of the first housing 111. The second housing 112, as the cover part, can be provided with a riveting structure to cooperate with the first housing 111.

[0052] In actual situations, by changing the structural form of the housing 11, the terminal on the top of the secondary battery 10 can be cancelled. Since the stretching direction of the housing part of the secondary battery 10 changes from the height direction to the width direction, the thickness of the aluminum shell in the height direction of the secondary battery 10 can be reduced to about 80% of the original. At the same time, after cancelling the terminal structure on the top surface of the battery cell assembly 12, reducing the thickness of the plastic part by 60%, and reducing the thickness of the aluminum shell by 80%, the total height of the bare battery cell of the single battery is increased by about 2% to 5%. Compared with the secondary battery of the same size in the prior art, the capacity of the secondary battery 10 provided by some embodiments of the present application is increased by about 2% to 5%, and the increased energy density is about 2% to 5%. For example, in the secondary battery in the prior art, the thickness of the plastic part is 4.5 mm to 5.5 mm, the thickness of the aluminum shell in the height direction of the secondary battery is 1 mm to 2 mm, the height of the bare battery cell is 185 mm to 205 mm, and the capacity of the secondary battery is 270 Ah to 290 Ah. After adopting the structure of the secondary battery 10 provided by some embodiments of the present application, the thickness of the plastic part 15 can be reduced to 2.7 mm to 3.3 mm, the thickness of the aluminum shell in the height direction of the secondary battery 10 can be reduced to 0.8 mm to 1.6 mm, the height of the bare battery cell can be increased to 188 mm to 215 mm, and the capacity of the secondary battery 10 can be increased to 275 Ah to 350 Ah.

[0053] Step S120: Manufacture the battery cell assembly 12, and bend and extend the positive electrode tab 121 on the top surface of the battery cell assembly 12 to the first side surface, and bend and extend the negative electrode tab 122 on the top surface of the battery cell assembly 12 to the second side surface.

[0054] The battery cell assembly 12 is formed by winding or laminating a positive electrode tab, a negative electrode tab, and a separator. The positive electrode tab leads out a positive electrode ear 121, and the negative electrode tab leads out a negative electrode ear 122. The positive electrode ear 121 bends and extends from the top surface of the bare battery cell to the first side surface, and the negative electrode ear 122 bends and extends from the top surface of the bare battery cell to the second side surface. The first side surface and the second side surface are two surfaces with a larger area of the bare battery cell. By folding the positive and negative electrode ears, the connection position of the positive and negative electrode ears can be transferred from the top surface of the bare battery cell to the two side surfaces with a larger area. Furthermore, a positive and negative electrode structure is formed on the two surfaces with a larger area of the secondary battery 10.

[0055] Step S130: Place the battery cell assembly 12 in the accommodation cavity 101, make the first side surface of the battery cell assembly 12 face the bottom wall 1111, and connect the part of the positive electrode ear 121 extending to the first side surface to the bottom wall 1111, and connect the part of the negative electrode ear 122 extending to the second side surface to the negative electrode terminal 113.

[0056] After both the battery cell assembly 12 and the housing 11 are manufactured, the battery cell assembly 12 can be installed in the accommodation cavity 101 of the first housing 111. During the installation of the battery cell assembly 12, make the first side surface of the bare battery cell face the bottom wall 1111, and after the battery cell assembly 12 is installed, connect the positive electrode ear 121 to the bottom wall 1111. The negative electrode ear 122 is connected to the negative electrode terminal 113 on the second housing 112. Thereby, the positive electrode terminal of the secondary battery 10 is cancelled, and there is no positive and negative electrode connection piece, which can save the number of parts and reduce the cost. By directly welding the positive electrode ear 121 to the bottom wall 1111 of the first housing 111, the first housing 111 is made to carry a positive potential while omitting the positive electrode terminal.

[0057] It should be noted that in the prior art, the ear connection structure is basically formed by the form of a connection piece and a butterfly weld of the ears. The connection piece will occupy the internal space of the housing 11, and at the same time, adding a connection piece increases the part cost. Moreover, the ears are folded on the top surface of the bare battery cell, which requires a large folding space and reduces the overall space utilization efficiency. By changing the ear connection structure, the cost of the secondary battery 10 can be reduced. In actual situations, after the battery cell assembly 12 is installed, the plastic part 15 can be installed continuously. The position of the battery cell assembly 12 in the housing 11 is limited by the plastic part 15. After the ear connection form is changed, the height of the plastic part 15 can be reduced to about 60% of the original.

[0058] In addition, there can be multiple cell components 12, that is, multiple bare cells are encapsulated in the housing 11 at the same time, and the multiple bare cells can be connected in series. Thereby, the self-voltage of the secondary battery 10 is increased, and the number of secondary batteries 10 required to reach the required voltage after grouping is reduced. For example, currently the voltage of the secondary battery 10 is about 3.5V, and the number of secondary batteries 10 required to form a string to reach the designed voltage value of the battery module is relatively large. After two bare cells are connected in series in the housing 11, the voltage of the secondary battery 10 rises from the original 3.35V to 6.7V, the platform voltage of the secondary battery 10 is increased, and the required number of secondary batteries 10 for the same battery module is halved when reaching the required voltage.

[0059] Step S140: Connect the first housing 111 and the second housing 112 to close the opening 102 with the second housing 112.

[0060] After the connection between the cell component 12 and different housings is completed, the connection between the first housing 111 and the second housing 112 can be carried out to close the opening 102 on the first housing 111 with the second housing 112. The connection between the first housing 111 and the second housing 112 can be achieved by welding. At the same time, a rabbet can be provided at the edge of the second housing 112 for positioning to ensure the connection accuracy between the second housing 112 and the first housing 111. In actual situations, after the negative electrode tab 122 is connected to the negative electrode terminal 113, the second housing 112 and the first housing 111 can be welded around, so that the two different housings are connected to form a whole.

[0061] In addition, before providing the housing 11 in step S110, the following steps are further included: Step S101: Open a terminal hole 1121 on the second housing 112.

[0062] Open a terminal hole 1121 on the second housing 112 to connect the negative electrode terminal 113. The second housing 112, as a relatively large cover part, has enough space to set the negative electrode terminal 113. In actual situations, the terminal hole 1121 can be provided near the edge of the second housing 112 so that the installation position of the negative electrode terminal 113 is close to the edge of the second housing 112, which is convenient for subsequent series assembly of multiple secondary batteries 10.

[0063] Step S102: Place the first insulating member 115 and the second insulating member 116 on both sides of the terminal hole 1121 respectively.

[0064] The first insulating member 115 and the second insulating member 116 can play an insulating role between the first housing 111 and the negative electrode terminal 113. Both the first insulating member 115 and the second insulating member 116 are provided as hollow rings, capable of abutting against the inner wall of the terminal hole 1121 to isolate between the negative electrode terminal 113 and the first housing 111. The first insulating member 115 and the second insulating member 116 can also abut against the surface of the inner wall of the terminal hole 1121 where they are connected to the first housing 111, so as to ensure the insulating effect between the negative electrode terminal 113 and the first housing 111. Both the first insulating member 115 and the second insulating member 116 can be made of plastic material.

[0065] As Figure 12 shown, both sides of the terminal hole 1121 respectively have a first stepped surface 1122 and a second stepped surface 1123. The first insulating member 115 abuts against the first stepped surface 1122, and the second insulating member 116 abuts against the second stepped surface 1123. The positions of different insulating members can be restricted by the stepped surfaces.

[0066] Step S103: Abut the negative electrode terminal 113 against the second insulating member 116.

[0067] After the insulating members are arranged, the installation of the negative electrode terminal 113 can be carried out. The negative electrode terminal 113 is located outside the second housing 112 away from the accommodation cavity 101, and its position is defined by the second insulating member 116.

[0068] Step S104: Make the positioning member 117 abut against the first insulating member 115, and make the riveting member 118 pass through the negative electrode terminal 113 and the terminal hole 1121 to be welded to the positioning member 117.

[0069] The riveting member 118 can be integrally connected with the positioning member 117. The positioning member 117 is fixed on the inner surface of the second housing 112 close to the accommodation cavity 101, and the riveting member 118 fixes the negative electrode terminal 113 through the boss structure at its end. That is, the negative electrode terminal 113, the riveting member 118 and the positioning member 117 form an integral body with a conductive function, thus completing the installation of the negative electrode terminal 113 on the second housing 112.

[0070] After manufacturing the battery cell assembly 12 in step S120, the following steps can also be included: Step S121: Provide a first insulating film 13, and the first insulating film 13 includes a main body portion 131, a first extension portion 132 and a second extension portion 133 which are integrally arranged.

[0071] The first insulating film 13 is the part that wraps the battery cell assembly 12, which can effectively seal and protect the bare battery cell and isolate the bare battery cell from the housing 11. The first insulating film 13 is encapsulated on the outside of the battery cell assembly 12. The main body portion 131 is the part that wraps around the periphery of the bare battery cell, and the first extension portion 132 and the second extension portion 133 are the parts that wrap the two end faces of the bare battery cell. The first extension portion 132 and the second extension portion 133 are formed by extending from the edges of the main body portion 131 that are away from each other in opposite directions. Through the cooperation between different parts, the battery cell assembly 12 can be effectively wrapped. In actual situations, the first insulating film 13 can be made of polyester film, such as Mylar film.

[0072] Step S122: Fold the second extension portion 133 so that the second extension portion 133 covers the bottom surface of the battery cell assembly 12.

[0073] Use the second extension portion 133 to cover the bottom surface of the bare battery cell. The area of the second extension portion 133 is larger than the area of the bottom surface of the bare battery cell, so that the bottom surface of the bare battery cell can be covered.

[0074] Step S123: Wrap the main body portion 131 around the surface of the battery cell assembly 12 so that the main body portion 131 covers the first side surface and the second side surface of the battery cell assembly 12, and expose a part of the positive electrode tab 121; Use the main body portion 131 to wrap around the periphery of the bare battery cell. The main body portion 131 covers along the periphery of the bare battery cell and covers the two larger side surfaces of the bare battery cell. At the same time, a part of the positive electrode tab 121 is exposed through the reserved notch on the main body portion 131.

[0075] Step S124: Fold the first extension portion 132 so that the first extension portion 132 covers the top surface of the battery cell assembly 12; Use the first extension portion 132 to cover the top surface of the bare battery cell. The area of the first extension portion 132 is larger than the area of the top surface of the bare battery cell, so that the top surface of the bare battery cell can be covered.

[0076] Step S125: Weld the part of the second extension portion 133 corresponding to the second side surface to the main body portion 131, weld the part of the first extension portion 132 corresponding to the second side surface to the main body portion 131, and expose a part of the negative electrode tab 122.

[0077] By welding the overlapping parts of the first extension part 132 and the main body part 131, and the overlapping parts of the second extension part 133 and the main body part 131, multiple parts of the first insulating film 13 can be connected to form a whole. Thus, the bare battery cell is wrapped inside, and part of the positive electrode tab 121 and the negative electrode tab 122 are exposed. That is, after the positive electrode tab 121 passes through the avoidance hole of the first insulating film 13, different parts of the first insulating film 13 are folded in sequence, and the overlapping area of the folded first insulating film 13 is formed into a whole by hot melt welding. The parts of the positive electrode tab 121 and the negative electrode tab 122 corresponding to the side of the bare battery cell are located on the outer side of the first insulating film 13 away from the bare battery cell.

[0078] In actual situations, after the bare battery cell is completely wrapped with the Mylar film, the positive electrode tab 121 can be welded to the inner surface of the bottom wall 1111 of the first housing 111 facing the accommodation cavity 101. That is, after the battery cell assembly 12 is placed in the accommodation cavity 101 in step S130, the following steps can also be included: Step S131: Weld the positive electrode tab 121 and the bottom wall 1111 from the outer side of the bottom wall 1111 away from the accommodation cavity 101, and the welding process uses friction welding or laser welding.

[0079] In addition, after the bare battery cell is completely wrapped with the Mylar film, the negative electrode tab 122 can also be connected to the negative electrode post 113 on the second housing 112. That is, after the battery cell assembly 12 is placed in the accommodation cavity 101 in step S130, the following steps can also be included: Step S132: Place the second housing 112 on the first housing 111 along the direction of the opening 102.

[0080] That is, place the second housing 112 along the direction parallel to the side wall 1112. At this time, the placement direction of the second housing 112 is parallel to the top surface of the bare battery cell and close to the lead-out surface of the negative electrode tab 122.

[0081] Step S133: Make the negative electrode tab 122 abut against the negative electrode post 113 on the second housing 112.

[0082] After the second housing 112 is placed, the negative electrode tab 122 can be kept upright, that is, the part of the negative electrode tab 122 corresponding to the side of the bare battery cell is far from the side of the bare battery cell, and the negative electrode tab 122 abuts against the negative electrode post 113 on the second housing 112. When the negative electrode post 113 is installed by the positioning part 117 and the riveting part 118, even if the negative electrode tab 122 abuts against the positioning part 117 formed integrally with the negative electrode post 113.

[0083] Step S134: Weld the negative electrode tab 122 and the negative electrode post 113.

[0084] When the negative electrode tab 122 is upright and abuts against the negative electrode terminal 113 of the second housing 112, there is sufficient space to weld the negative electrode tab 122 and the negative electrode terminal 113. Thereby, the connection between the negative electrode tab 122 and the negative electrode terminal 113 is realized. When the negative electrode terminal 113 is installed through the positioning member 117 and the riveting member 118, that is, the negative electrode tab 122 and the positioning member 117 are welded, so that a conductive path is formed between the negative electrode tab 122 and the negative electrode terminal 113.

[0085] After the battery cell assembly 12 is placed in the accommodation cavity 101 in step S130, the following steps may further be included: Step S135: Insert the plastic part 15 into the accommodation cavity 101, and make the plastic part 15 abut against the first housing 111 and the battery cell assembly 12 respectively.

[0086] After the plastic part 15 is inserted into the accommodation cavity 101, it will squeeze the bare battery cell and compress the bare battery cell on the top surface of the bare battery cell. Through the plastic part 15, the position of the bare battery cell in the accommodation cavity 101 can be effectively fixed, preventing the battery cell assembly 12 from moving in the accommodation cavity 101.

[0087] Some embodiments of the present application further provide an energy storage system, which includes a box body and a battery module. The box body is provided with an inner cavity. The battery module is arranged in the inner cavity, and the battery module includes a plurality of the above-mentioned secondary batteries 10.

[0088] The energy storage system can adopt a cabin-level energy storage form, a cluster-level energy storage form and a pack-level energy storage form according to different application scenarios. The secondary battery 10, that is, the battery cell, can be connected in series or in parallel to form a battery module, and the battery module adopts a certain packaging form to form a whole. One or more battery modules can be adopted in the energy storage system, and a certain number of battery modules can form a battery cluster for unified management and control. A plurality of battery modules can be packaged in a box body with a certain volume to form a battery pack, or can be packaged in a container with a larger volume to form a container energy storage system. A plurality of battery modules can be jointly managed and controlled through a battery management system and a thermal management system.

[0089] By simplifying the structure of the secondary battery 10, the influence of the complex manufacturing process of the secondary battery 10 on the working performance can be reduced. At the same time, the installation space in the packaging housing 11 can be effectively utilized to increase the capacity of the battery cell, thereby improving the working performance of the secondary battery 10. Ensure the use performance of the energy storage system.

[0090] Some embodiments of the present application further provide an electrical device, which includes the above-mentioned energy storage system.

[0091] The electrical device can be a daily consumer product, an industrial product, or other electrical devices equipped with an electrochemical energy storage system as an energy supply source.

[0092] Those of ordinary skill in the art can understand that the above embodiments are specific examples for implementing the present application, and in practical applications, various changes can be made to them in form and details without departing from the spirit and scope of the present application.

Claims

1. A secondary battery, characterized in that: include: A shell, comprising a first shell and a second shell connected to each other, the first shell being provided with a receiving cavity and an opening communicating with the receiving cavity, the second shell closing the opening, the first shell comprising a bottom wall and a plurality of side walls enclosing the receiving cavity on the bottom wall, the area of ​​a surface of the bottom wall facing the receiving cavity being larger than the area of ​​a surface of any of the side walls facing the receiving cavity, and the second shell being provided with a negative pole insulated from the second shell; A battery cell assembly is arranged in the accommodating cavity, the battery cell assembly comprises a positive electrode sheet, a negative electrode sheet and a diaphragm separating the positive electrode sheet from the negative electrode sheet, the positive electrode sheet is provided with a positive electrode tab, the negative electrode sheet is provided with a negative electrode tab, the battery cell assembly comprises a first surface and a second surface arranged opposite to each other, and a third surface connecting the first surface and the second surface, the first surface faces the bottom wall, the second surface faces the second shell, the positive electrode tab is bent and extended from the third surface to the first surface, and the negative electrode tab is bent and extended from the third surface to the second surface; The portion of the positive electrode tab extending to the first surface is connected to the bottom wall, and the portion of the negative electrode tab extending to the second surface is connected to the negative electrode column.

2. The secondary battery according to claim 1, characterized in that: It also includes a first insulating film, which includes a main body, a first extending portion and a second extending portion that are integrally arranged, the main body is arranged from the first surface along the edge of the third surface around the battery cell assembly, the first extending portion covers the third surface, and the second extending portion covers the surface of the battery cell assembly facing away from the third surface.

3. The secondary battery according to claim 2, characterized in that: The first extension portion includes a first edge and a second edge that are arranged opposite to each other, the first edge is integrally arranged with the main body, and a portion of the first edge and the main body are connected at a gap to form a first hollow area for the positive electrode tab to pass through, and a portion of the second edge is spaced from the edge of the main body to form a second hollow area for the negative electrode tab to pass through; Part of the second edge is bent to cover the side of the main body away from the second surface and is fixed on the main body, and at least part of the edge of the second extension part is bent to cover the side of the main body away from the second surface and is fixed on the main body.

4. The secondary battery according to claim 1, characterized in that: It also includes a second insulating film, which wraps the shell inside. The second insulating film is provided with a first through hole and a second through hole. The first through hole is arranged toward the bottom wall and exposes a portion of the bottom wall, and the second through hole is arranged toward the second shell and exposes the negative electrode column.

5. The secondary battery according to claim 4, characterized in that: The negative electrode column is arranged adjacent to the edge of the second shell, and the first through hole and the second through hole are coaxially arranged in the direction of the opening.

6. The secondary battery according to claim 4, characterized in that: One of the plurality of side walls is provided with an explosion-proof valve, and the second insulating film is provided with a third through hole, and the third through hole is provided toward the side wall and exposes the explosion-proof valve.

7. The secondary battery according to claim 1, characterized in that: It also includes a plastic part, which is arranged in the accommodating cavity. The plastic part includes a first abutting surface and a second abutting surface that are arranged opposite to each other. The first abutting surface abuts against the shell, and the second abutting surface abuts against the battery core assembly.

8. A method for preparing a secondary battery, characterized in that: include: A shell is provided, the shell comprising a first shell and a second shell, the first shell being provided with a receiving cavity and an opening communicating with the receiving cavity, the first shell comprising a bottom wall and a plurality of side walls enclosing the receiving cavity on the bottom wall, the area of ​​a surface of the bottom wall facing the receiving cavity being larger than the area of ​​a surface of any of the side walls facing the receiving cavity, and the second shell being provided with a negative pole insulated from the second shell; Making a battery cell assembly, so that the positive electrode tab on the top surface of the battery cell assembly is bent and extended to the first side surface, and the negative electrode tab on the top surface of the battery cell assembly is bent and extended to the second side surface; The battery cell assembly is placed in the accommodating cavity, with the first side surface of the battery cell assembly facing the bottom wall, and the portion of the positive electrode tab extending to the first side surface is connected to the bottom wall, and the portion of the negative electrode tab extending to the second side surface is connected to the negative electrode column; The first shell and the second shell are connected so that the second shell closes the opening.

9. The method for preparing a secondary battery according to claim 8, characterized in that: Before providing the housing, it also includes: A pole hole is provided on the second shell; A first insulating member and a second insulating member are respectively placed on both sides of the pole hole; placing the negative electrode post against the second insulating member; The positioning member is abutted against the first insulating member, and the rivet member is passed through the negative pole and the pole hole to be welded to the positioning member.

10. The method for preparing a secondary battery according to claim 8, characterized in that: After making the battery cell components, it also includes: Providing a first insulating film, the first insulating film comprising a main body portion, a first extending portion and a second extending portion which are integrally provided; Folding the second extension portion so that the second extension portion covers the bottom surface of the battery core assembly; Wrapping the main body around the surface of the battery cell assembly so that the main body covers the first side surface and the second side surface of the battery cell assembly and exposes a portion of the positive electrode tab; Folding the first extension portion so that the first extension portion covers the top surface of the battery core assembly; The second extension portion is welded to a portion of the main body corresponding to the second side surface, the first extension portion is welded to a portion of the main body corresponding to the second side surface, and a portion of the negative electrode tab is exposed.

11. The method for preparing a secondary battery according to claim 8, characterized in that: After placing the battery cell assembly in the accommodating cavity, the method further comprises: The positive electrode tab is welded to the bottom wall from the outside of the bottom wall away from the accommodating cavity, and the welding process adopts friction welding or laser welding.

12. The method for preparing a secondary battery according to claim 8, characterized in that: After placing the battery cell assembly in the accommodating cavity, the method further comprises: placing the second shell on the first shell along the direction of the opening; The negative electrode tab is brought into contact with the negative electrode post of the second shell; The negative electrode tab and the negative electrode post are welded.

13. The method for preparing a secondary battery according to claim 8, characterized in that: After placing the battery cell assembly in the accommodating cavity, the method further comprises: Insert the plastic part into the accommodating cavity, and make the plastic part abut against the first shell and the battery core assembly respectively.

14. An energy storage system, characterized in that: include: The box body is provided with an inner cavity; A battery module is arranged in the inner cavity, and the battery module includes a plurality of secondary batteries according to any one of claims 1 to 7.

15. An electrical device, characterized in that: Includes the energy storage system as described in claim 14.

Images