Secondary battery, battery pack, and electronic device

Abstract

The utility model provides a secondary battery, a battery pack and an electronic device. The secondary battery comprises a shell and an electrode assembly, the shell comprises an end wall and a side wall surrounding the end wall; the electrode assembly is accommodated in the shell, the electrode assembly comprises a winding structure formed by laminating and winding a positive pole piece, a diaphragm and a negative pole piece, the negative pole piece comprises a first empty foil area extending out of the diaphragm along the winding shaft direction of the winding structure, and the first empty foil area is electrically connected with the shell; the tail end of the negative pole piece comprises a second empty foil area, at least part of the second empty foil area extends out of the diaphragm in the winding direction of the winding structure and is located on the side, away from the winding shaft, of the negative pole piece, the second empty foil area is the ending end of the winding structure, and the technical problem that the resistance of the shell is large can be solved.

Description

TECHNICAL FIELD

[0001] The utility model relates to a battery technical field, concretely relates to a secondary battery, battery pack and electronic device. BACKGROUND

[0002] Large cylindrical batteries are widely used in new energy vehicles, energy storage power stations, electric tools, and high-end consumer electronics due to their simple structure, good heat dissipation performance, high energy density, and ease of mass production.

[0003] Large cylindrical batteries usually use a shell as the negative electrode. This design not only provides good mechanical strength and sealing, but also effectively reduces the internal resistance of the battery and improves the charging and discharging efficiency of the battery. However, in practical applications, especially in battery modules, the shell has a large resistance, which generates additional voltage drop and heat, causing the temperature of the battery module to rise, affecting the performance and lifespan of the battery. Reducing the resistance of the shell has become one of the important technical problems for improving the performance and safety of large cylindrical batteries. SUMMARY

[0004] The utility model provides a kind of secondary battery, battery pack and electronic device to improve the technical problem of large shell resistance.

[0005] To achieve the above-mentioned purpose and other related purposes, the utility model provides a kind of secondary battery, battery pack and electronic device, which comprises: a shell and an electrode assembly; the shell comprises an end wall and a side wall surrounding the end wall; the electrode assembly is contained in the shell, and the electrode assembly comprises a positive electrode sheet, a separator and a negative electrode sheet stacked and wound to form a winding structure; the negative electrode sheet comprises a first empty foil area extending out of the separator along the winding axis direction of the winding structure, and the first empty foil area is electrically connected with the shell; the tail end of the negative electrode sheet comprises a second empty foil area, which at least partially extends out of the separator along the winding direction of the winding structure and is located on the side of the negative electrode sheet away from the winding axis; and the second empty foil area is the end of the winding structure.

[0006] In the above technical solution, the electrode assembly comprises a positive electrode sheet, a separator and a negative electrode sheet stacked and wound to form a winding structure, and the tail end of the negative electrode sheet comprises a second empty foil area extending out of the separator and located on the side of the negative electrode sheet away from the winding axis, and the second empty foil area is the end of the winding structure. The second empty foil area can conduct electricity, and the second empty foil area is used as the end when the electrode assembly is electrified and expanded, so that the negative electrode sheet can be in contact with the side wall to realize direct electrical connection between the negative electrode sheet and the shell. This setting increases the conduction path, which can effectively reduce the shell resistance and reduce energy loss and heat generation.

[0007] In an example of the secondary battery of the utility model, the inner diameter of the shell is d0, and the length of the second empty foil area along the winding direction of the winding structure is L0, L0>πd0.

[0008] In the technical solution, πd0 is the circumference of the inner side of the shell, and L0>πd0 means that the winding number of the second empty foil area is at least one, which means that the outermost circle of the winding structure is the second empty foil area. To achieve a larger contact area between the inner wall of the shell and the second empty foil area. Further reduce the internal resistance of the shell.

[0009] In the secondary battery example of the utility model, L0<3πd0.

[0010] In the technical solution, L0<3πd0, that is, the winding number of the second empty foil area is less than three. While ensuring that the second empty foil area located in the outermost circle of the winding structure has good contact with the inner wall of the shell, it can alleviate the reduction of the overall energy density of the battery caused by the excessive length of the second empty foil area, and is conducive to improving the space utilization of the shell.

[0011] In the secondary battery example of the utility model, the tail end of the negative electrode sheet further includes a third empty foil area, the third empty foil area is located on the side of the negative electrode sheet facing the winding shaft, and along the winding direction of the winding structure, the length of the second empty foil area is L0, and the length of the third empty foil area is L1, L1=L0.

[0012] In the technical solution, the second empty foil area and the third empty foil area have the same length, which is conducive to reducing the difficulty of processing the negative electrode sheet, improving the processing efficiency and reducing the processing cost.

[0013] In the secondary battery example of the utility model, the diameter of the winding structure is d1, the sum of the thickness of one layer of positive electrode sheet, the thickness of one layer of negative electrode sheet and the thickness of two layers of diaphragm is a, the tail end of the negative electrode sheet further includes a third empty foil area, the third empty foil area is located on the side of the negative electrode sheet away from the winding shaft, and along the winding direction of the winding structure, the length of the second empty foil area is L0, and the length of the third empty foil area is L1, L0-L1<π(d1-a).

[0014] In the technical solution, the length L0 of the second empty foil area and the length L1 of the third empty foil area are different, which means that the starting positions of the second empty foil area and the third empty foil area are staggered, and the length of the second empty foil area is longer than that of the third empty foil area. π(d1-a) is the circumference of the second circle of the negative electrode sheet from outside to inside, and the setting of L0-L1<π(d1-a) means that the distance between the third empty foil area and the second empty foil area is less than the circumference of the second circle of the negative electrode sheet from outside to inside. This setting not only ensures that the second empty foil area has enough contact area with the inner wall of the shell, but also ensures that the overall energy density of the battery is high.

[0015] In the secondary battery example of the utility model, the winding structure includes a first adhesive tape for sealing the tail end, the first adhesive tape covers the tail end of the negative electrode sheet and extends along the winding axis direction of the winding structure.

[0016] In the technical solution, the tail end of the tailing section of the winding structure generally extends along the winding axis direction, and the first adhesive tape extends along the winding axis direction of the winding structure to seal the tail end of the winding structure. This arrangement can cover a larger area of the tail end, which is beneficial to avoid the curling of the tail end of the winding structure and can greatly retain the effective contact area between the second empty foil area and the inner wall of the shell.

[0017] In an example of the secondary battery, the winding structure includes a plurality of second adhesive tapes for sealing the tail end, the second adhesive tapes cover the tail end of the negative electrode sheet and extend along the winding direction of the winding structure, and the plurality of second adhesive tapes are arranged at intervals along the winding axis direction of the winding structure.

[0018] In the technical solution, the second adhesive tape is arranged to extend along the winding direction of the winding structure to seal the winding structure. This arrangement is beneficial to improve the firmness and reliability of the sealing, and the sealing method does not need to be aligned with the tail end of the tailing section, which can improve the sealing efficiency.

[0019] In an example of the secondary battery, the material of the shell is stainless steel.

[0020] In the technical solution, stainless steel has good corrosion resistance, which can prolong the service life of the shell. Stainless steel has high mechanical strength and toughness, and can withstand large mechanical stress, which can better protect the internal structure of the battery. Stainless steel also has high processing performance. Stainless steel does not need to be treated by rust prevention and corrosion resistance, which reduces the production cost.

[0021] In an example of the secondary battery, at least part of the third empty foil area is provided with an expansion adhesive.

[0022] In the technical solution, the expansion adhesive is arranged in the third empty foil area. This arrangement does not reduce the overall energy density of the battery or the area of the second empty foil area that can be used for conduction. The expansion adhesive can expand when it comes into contact with electrolyte, which makes the winding structure and the inner wall of the shell more fully contact, thereby increasing the effective contact area between the second empty foil area and the inner wall of the shell, reducing the shell resistance, and reducing energy loss and heat generation.

[0023] The utility model also provides a battery pack, the battery pack includes any one of the secondary battery.

[0024] The utility model also provides an electronic device, the electronic device includes the battery pack.

[0025] The utility model discloses a secondary battery, electrode assembly includes the positive pole sheet, diaphragm and the negative pole sheet laminated and is wound and forms the winding structure, and the tail end of negative pole sheet includes the diaphragm of protruding, and the second empty foil area of negative pole sheet side away from winding shaft, and the second empty foil area is the winding structure's end. The second empty foil area can conduct electricity, and the second empty foil area is used as the end, when electrode assembly energized expansion, the second empty foil area can contact with side wall to realize negative pole sheet and shell direct conductive connection. The setting increases the conductive path, can effectively reduce the shell resistance, reduces energy loss and heat production. BRIEF DESCRIPTION OF DRAWINGS

[0026] In order to more clearly illustrate the technical scheme in the embodiment of the utility model or prior art, the following will be briefly introduced the drawing needed to be used in the embodiment or prior art description, obviously, the drawing in the following description only some embodiments of the utility model, for ordinary skilled person in the art, under the premise of not paying creative labor, still can obtain other embodiments according to these drawings.

[0027] Figure 1 It is the overall structure schematic diagram of the secondary battery of the utility model one example;

[0028] Figure 2 It is the electrode assembly structure schematic diagram of the secondary battery of the utility model one example;

[0029] Figure 3 It is the local schematic diagram of the winding structure end of the secondary battery of the utility model one example;

[0030] Figure 4 It is Figure 3 The schematic diagram of A, B two sides of the negative pole sheet after unfolding;

[0031] Figure 5 It is the local schematic diagram of the winding structure end of the secondary battery of the utility model one example;

[0032] Figure 6 It is Figure 5 The schematic diagram of A, B two sides of the negative pole sheet after unfolding;

[0033] Figure 7 It is the first adhesive tape pasting schematic diagram of the winding structure of the secondary battery of the utility model one example;

[0034] Figure 8 It is Figure 7 Front view;

[0035] Figure 9 It is the second adhesive tape pasting schematic diagram of the winding structure of the secondary battery of the utility model one example;

[0036] Figure 10 It isFigure 9 a front view of the battery pack;

[0037] Figure 11 a schematic view of an example of the battery pack of the present application;

[0038] Figure 12 a schematic view of an example of the electronic device of the present application.

[0039] Element Number Explanation:

[0040] 1, electronic device; 10, battery pack; 11, working part; 101, box body; 102, box cover; 100, secondary battery; 110, shell; 111, end wall; 112, side wall; 113, opening; 120, electrode assembly; 121, negative pole piece; 1211, negative pole current collector; 1212, first coating area; 1213, first empty foil area; 1214, second empty foil area; 1215, third empty foil area; 1216, negative pole lug; 122, diaphragm; 123, positive pole piece; 1231, positive pole current collector; 1232, second coating area; 1233, fourth empty foil area; 1234, positive pole lug; 124, winding structure; 1241, first adhesive tape; 1242, second adhesive tape; 130, first current collecting member; 140, second current collecting member; 150, pole; 160, end cover. DETAILED DESCRIPTION

[0041] The above and other advantages and effects of the present application will become readily apparent to those of ordinary skill in the art from the following description in conjunction with the accompanying drawings. The present application can be applied in various ways, and the details described in the specification can be modified in various ways based on different viewpoints and applications without departing from the spirit of the present application. It should be noted that the following examples and features in the examples can be combined with each other without conflict. It should also be understood that the terms used in the examples of the present application are used to describe specific embodiments, and are not intended to limit the scope of protection of the present application. Unless otherwise specified, the test methods in the following examples are generally performed under conventional conditions or according to the conditions recommended by the manufacturers.

[0042] When the examples give numerical ranges, it should be understood that, unless the present application indicates otherwise, each numerical range has two endpoints and any number between the two endpoints can be selected. Unless otherwise defined, all technical and scientific terms used in the present application are used by those skilled in the art in the present technical field and in the description of the present application, and any method, device and material of the prior art similar or equivalent to the methods, devices and materials used in the examples of the present application can be used to implement the present application.

[0043] It should be noted that the terms such as "upper", "lower", "left", "right", "middle" and "one" in the present specification are only for the convenience of clear description, and are not intended to limit the scope of the present application. The change or adjustment of the relative relationship is also considered as the scope of the present application without substantial change of the technical content.

[0044] The secondary battery includes an electrode assembly, which is a component in which an electrochemical reaction occurs in the secondary battery, and can include one or more electrode assemblies.

[0045] The electrode assembly is mainly formed by winding or stacking a positive electrode tab and a negative electrode tab, and a separator is usually arranged between the positive electrode tab and the negative electrode tab. The positive electrode tab includes a positive current collector and a positive active material, and the positive active material is coated on the surface of the positive current collector; the area of the positive current collector on which the active material is coated is a coated area, and the area of the positive current collector on which the active material is not coated is a blank foil area, and the blank foil area is wound to form a positive electrode tab of the electrode assembly. The negative electrode tab includes a negative current collector and a negative active material, and the negative active material is coated on the surface of the negative current collector; the area of the negative current collector on which the active material is coated is a coated area, and the area of the negative current collector on which the active material is not coated is a blank foil area, and the blank foil area is wound to form a negative electrode tab of the electrode assembly. Taking a lithium ion cylindrical battery as an example, the material of the positive current collector can be aluminum, and the positive active material can be lithium cobaltate, lithium iron phosphate, ternary lithium or lithium manganate, etc. The material of the negative current collector can be copper, and the negative active material can be carbon or silicon, etc. The material of the separator can be PP (polypropylene) or PE (polyethylene), etc. In order to protect and insulate the battery cell, an insulating film can also be wrapped outside the battery cell, and the insulating film can be synthesized by PP, PE, PET, PVC or other high polymer materials.

[0046] The secondary battery also includes a shell, an end cover and a post, the shell includes an end wall and a side wall surrounding the end wall, one end of the side wall has an opening, the electrode assembly can be assembled into the shell through the opening of the shell, the end cover is used to cover the opening of the shell to achieve sealing, the end cover and / or the end of the shell close to the end cover are electrically connected to the positive tab or the negative tab in the electrode assembly, and the post is electrically connected to the tab of the other polarity of the electrode assembly through the end wall to guide out the electric energy generated by the electrode assembly.

[0047] When a plurality of secondary batteries are applied to electronic devices to form a battery module, the electric energy in the electrode assembly is usually guided out through the post and the end wall, and the current of the end cover and / or the end of the shell close to the end cover needs to flow through the side wall of the shell and then be guided out. However, the inventors found that the resistance of the side wall of the shell is large, which will generate additional voltage drop and heat, causing the temperature of the battery module to rise, affecting the performance and service life of the battery.

[0048] In view of this, the utility model provides a technical scheme, the tail end of negative pole piece includes at least part of the membrane, and the second empty foil area of negative pole piece is located on the side of winding shaft, and the second empty foil area is the end of winding structure. The second empty foil area is used as the end, when the electrode assembly is electrified and expanded, the second empty foil area can be contacted with the side wall to realize the direct conductive connection of the negative pole piece and the shell. The setting increases the conductive path, can effectively reduce the shell resistance, reduces energy loss and heat generation,

[0049] Please refer to Figures 1 to 12 The utility model provides a secondary battery 100, battery pack 10 and electronic device 1, the secondary battery 100 includes: shell 110, electrode assembly 120, pole 150 and end cover 160.

[0050] Please refer to Figure 1 And Figure 2 The shell 110 includes end wall 111 and the side wall 112 around end wall 111, as long as the stable sealing and electric connection relationship can be formed, the connection between end wall 111 and side wall 112 can be realized by multiple ways, for example, can be integrated stamping forming, integrated casting forming or split welding form. The surrounding of side wall 112 is not limited, can be cylindrical, cuboid or prismatic surrounding, also can be along other any closed loop profile that can be matched with end wall 111 surrounding, and the outer edge of end wall 111 is circular in the embodiment, side wall 112 is cylindrical and surrounds the outer edge of end wall 111, and the circular opening 113 is formed at the end of side wall 112 away from end wall 111. The shell 110 surrounded by end wall 111 and side wall 112 forms a containing cavity in it, for containing electrode assembly 120, electrolyte and other necessary components of battery. Specifically, the diameter of shell 110 can be determined according to the specific size of electrode assembly 120, such as 18mm, 21mm, 46mm etc. The material of shell 110 can be multiple, such as copper, iron, aluminum, steel, aluminum alloy etc., in order to prevent rust of shell 110 during long-term use, also can be plated with a layer of anti-rust material such as metal nickel on the surface of shell 110.

[0051] Please refer to Figures 1 to 2 The electrode assembly 120 is arranged inside the shell 110, and the electrode assembly 120 is the component of secondary battery 100 that generates electrochemical reaction. The shell 110 can contain one or more electrode assemblies 120. The electrode assembly 120 includes pole piece and diaphragm 122, and the pole piece and diaphragm 122 are wound to form winding structure 124, specifically, in the embodiment, the electrode assembly 120 includes negative pole piece 121, diaphragm 122 and positive pole piece 123 laminated and wound to form winding structure 124.

[0052] Please refer to Figures 1 to 2The negative electrode tab 121 includes a negative electrode current collector 1211 and a negative electrode active material layer coated on the negative electrode current collector 1211. The negative electrode current collector 1211 has a first coated area 1212 coated with the negative electrode active material layer and a first empty foil area 1213 not coated with the negative electrode active material layer. The first coated area 1212 and the first empty foil area 1213 are arranged axially along the shell 110. The first empty foil area 1213 extends out of the separator 122 along one end of the winding axis of the winding structure 124 and is bent towards the winding axis to form a stacked negative electrode tab 1216. It should be noted that the negative electrode current collector 1211 on both sides of the area where the first empty foil area 1213 is located is not coated with the negative electrode active material. Therefore, the first empty foil area 1213 in this embodiment includes both sides of the negative electrode current collector 1211 not coated with the negative electrode active material.

[0053] Referring to Figures 1 to 2 The positive electrode tab 123 includes a positive electrode current collector 1231 and a positive electrode active material layer coated on the positive electrode current collector 1231. The positive electrode current collector 1231 has a second coated area 1232 coated with the positive electrode active material layer and a fourth empty foil area 1233 not coated with the positive electrode active material layer. The second coated area 1232 and the fourth empty foil area 1233 are arranged axially along the shell 110. The fourth empty foil area 1233 extends out of the separator 122 along the other end of the winding axis of the winding structure 124 and is bent towards the axis of the shell 110 to form a stacked positive electrode tab 1234. It should be noted that the negative electrode current collector 1211 on both sides of the area where the fourth empty foil area 1233 is located is not coated with the positive electrode active material. Therefore, the fourth empty foil area 1233 in this embodiment includes both sides of the positive electrode current collector 1231 not coated with the positive electrode active material.

[0054] Referring to Figures 1 to 2 The separator 122 is arranged between the positive electrode tab 123 and the negative electrode tab 121 to separate the positive electrode active material layer and the negative electrode active material layer. Taking the lithium ion secondary battery 100 as an example, the material of the positive electrode current collector 1231 can be aluminum, the positive electrode active material layer includes a positive electrode active material, and the positive electrode active material can be lithium cobaltate, lithium iron phosphate, ternary lithium, or lithium manganate, etc. The material of the negative electrode current collector 1211 can be copper, the negative electrode active material layer includes a negative electrode active material, and the negative electrode active material can be carbon or silicon, etc. The base material of the separator 122 can be polypropylene (PP) or polyethylene (PE), etc. In order to protect and insulate the battery cell, an insulating film can also be wrapped outside the battery cell, and the insulating film can be synthesized from PP, PE, polyethylene terephthalate (PET), polyvinyl chloride (PVC), or other high molecular polymer materials.

[0055] Please refer to Figure 1 The pole 150 is fixed to the end wall 111 and is electrically connected to the electrode assembly 120. Specifically, the end wall 111 is provided with a pole hole, and the pole 150 is installed through the pole hole and is insulated from the end wall 111. In this embodiment, the pole 150 can be in any suitable form that can pass through the end wall 111 and be electrically connected to the positive electrode tab 1234 of the electrode assembly 120, such as a circular, square, prism, or any other profile that can achieve stable conduction. The pole hole corresponds to the shape of the pole 150. In this embodiment, the cross-section of the pole 150 is circular.

[0056] Please refer to Figure 1 The end cover 160 is sealingly installed in the opening 113. The outer edge of the end cover 160 corresponds to the shape of the opening 113 and is connected to the side wall 112 to seal the opening 113. The installation method of the end cover 160 includes but is not limited to mechanical sealing or welding sealing. In this embodiment, the end cover 160 is sealingly sealed on the opening 113 by mechanical sealing.

[0057] Please refer to Figure 1 , Figure 2 and Figure 7 Further, in the utility model, the positive electrode tab 1234 faces the end wall 111 or the opening 113, and the negative electrode tab 1216 faces the other end of the shell 110. In this embodiment, the positive electrode tab 1234 faces the end wall 111 and is electrically connected to the pole 150 to make the pole 150 positively charged. The negative electrode tab 1216 faces the opening 113, and the shell 110 is electrically connected to the negative electrode tab 1216 to be negatively charged. However, in another embodiment, the negative electrode tab 1216 can be connected to the pole 150, and the positive electrode tab 1234 can be connected to the shell 110. Further, the shell 110 and the negative electrode tab 1216 can be directly electrically connected or indirectly electrically connected through a current collecting member. The pole 150 and the positive electrode tab 1234 can be directly electrically connected or indirectly electrically connected through a current collecting member. In order to reduce the internal resistance and more evenly distribute the current, in this embodiment, the end cover 160 and the negative electrode tab 1216 are indirectly electrically connected through a first current collecting member 130, and the pole 150 and the positive electrode tab 1234 are indirectly electrically connected through a second current collecting member 140.

[0058] Please refer to Figures 2 to 6The tail end of the negative electrode sheet 121 includes a second empty foil area 1214. The second empty foil area 1214 at least partially protrudes from the diaphragm 122 and is located on the side of the negative electrode sheet 121 away from the winding shaft along the winding direction of the winding structure 124. The second empty foil area 1214 is the end of the winding structure 124. It should be noted that the end is the last area used to end the winding structure 124. The second empty foil area 1214 is also an area on the negative electrode current collector 121 that is not coated with a negative electrode active material. The second empty foil area 1214 at least partially protrudes from the diaphragm 122 to ensure that the end of the outermost circle of the winding structure 124 is the second empty foil area 1214. It should be noted that the second empty foil area 1214 is located on the side of the negative electrode sheet 121 away from the winding shaft, and the side of the negative electrode sheet 121 facing the winding shaft is not limited to whether it is coated with a negative electrode active material. The length of the second empty foil area 1214 along the winding direction of the winding structure 124 is not limited, and the number of winding turns can be greater than or equal to one turn, or less than one turn. Since the negative electrode current collector 121 is a conductive material, the second empty foil area 1214 can also be conductive. By using the second empty foil area 1214 as the end, when the electrode assembly 120 is energized and expanded, the second empty foil area 1214 can be in contact with the side wall 112 to achieve direct conductive connection between the negative electrode sheet 121 and the shell 110. This setting increases the conductive path, which can effectively reduce the resistance of the shell 110, reduce energy loss and heat generation.

[0059] Please refer to Figures 3 to 6 In an example of the secondary battery 100 of the present application, the inner diameter of the shell 110 is d0, and the length of the second empty foil area 1214 along the winding direction of the winding structure 124 is L0, L0>πd0. πd0 is the circumference of the inside of the shell 110, and L0>πd0 means that the number of winding turns of the second empty foil area 1214 is at least one turn, which means that the outermost circle of the winding structure 124 is the second empty foil area 1214. To achieve a larger contact area between the inner wall of the shell 110 and the second empty foil area 1214. Further reduce the internal resistance of the shell 110.

[0060] Please refer to Figures 3 to 6 In an example of the secondary battery 100 of the present application, L0 is limited to be less than 3πd0. That is, the number of winding turns of the second empty foil area 1214 is limited to be less than three turns. While ensuring good contact between the second empty foil area 1214 located on the outermost circle of the winding structure 124 and the inner wall of the shell 110, it can alleviate the reduction of the overall energy density of the battery caused by the excessive length of the second empty foil area 1214, and is conducive to improving the space utilization of the shell 110.

[0061] Please refer to Figures 3 to 4 , Figure 3 Figure 2 is a partial schematic view of the end of the winding structure 124 in the present embodiment, Figure 3Only the positive electrode tab 123 and the negative electrode tab 121 are shown, and the separator 122 is omitted. In the example of the secondary battery 100 of the utility model, the tail end of the negative electrode tab 121 further comprises a third empty foil area 1215, and the third empty foil area 1215 is also a region on the negative electrode current collector 1211 which is not coated with the negative electrode active material. The third empty foil area 1215 is located on the side of the negative electrode tab 121 facing the winding shaft, and along the winding direction of the winding structure 124, the length of the second empty foil area 1214 is L0, the length of the third empty foil area 1215 is L1, and L1=L0. The side of the negative electrode tab 121 away from the winding shaft is defined as the outer side, and the side of the negative electrode tab 121 facing the winding shaft is defined as the inner side. As shown in Figure 4 L1 and L0 are not limited in value, only L1=L0 is limited, which means that the second empty foil area 1214 and the third empty foil area 1215 located on the inner and outer sides of the negative electrode tab 121 respectively have the same length, which is conducive to reducing the difficulty of processing the negative electrode tab 121, improving the processing efficiency and reducing the processing cost.

[0062] Please refer to Figures 5 to 6 In the example of the secondary battery 100 of the utility model, the diameter of the winding structure 124 is d1, and the sum of the thickness of one layer of the positive electrode tab 123, the thickness of one layer of the negative electrode tab 121 and the thickness of two layers of the separator 122 is a. The value of a is the thickness of one layer after the positive electrode tab 123, the separator 122, the negative electrode tab 121 and the separator 122 are stacked. The tail end of the negative electrode tab 121 further comprises a third empty foil area 1215, and the third empty foil area 1215 is located on the side of the negative electrode tab 121 away from the winding shaft, and along the winding direction of the winding structure 124, the length of the second empty foil area 1214 is L0, the length of the third empty foil area 1215 is L1, and L0-L1<π(d1-a). In this embodiment, the length L0 of the second empty foil area 1214 and the length L1 of the third empty foil area 1215 are different, which means that the starting positions of the second empty foil area 1214 and the third empty foil area 1215 are staggered, and the length of the second empty foil area 1214 is longer than that of the third empty foil area 1215. π(d1-a) is the circumference of the second coil from the outside to the inside of the negative electrode tab 121, and the setting of limiting L0-L1<π(d1-a) means that the distance between the third empty foil area 1215 and the second empty foil area 1214 is less than the circumference of the second coil from the outside to the inside of the negative electrode tab 121. This setting not only ensures that the second empty foil area 1214 has enough contact area with the inner wall of the shell 110, but also ensures that the battery as a whole has a high energy density, and at the same time improves the utilization rate of the negative electrode active material and reduces the production cost.

[0063] For the convenience of understanding, the winding turns of the third empty foil area 1215 are taken as one turn for illustration. Please refer toFigures 5 to 6 , Figure 5 is a partial view of the end of the winding structure 124 in this embodiment, only the positive electrode sheet 123 and the negative electrode sheet 121 are shown, and the separator 122 is omitted. In this embodiment, the side away from the winding shaft is defined as the outer side, and the side facing the winding shaft is defined as the inner side. The outer and inner sides of the negative electrode sheet 121 in the outermost circle of the winding structure 124 are both empty foil regions without negative active material, the outer side of the negative electrode sheet 121 is the second empty foil region 1214, and the inner side of the negative electrode sheet 121 is the third empty foil region 1215. In order to avoid the occurrence of lithium precipitation, the first coating region 1212 of the negative electrode sheet 121 needs to be more than the second coating region 1232 of the positive electrode sheet 123, that is, the outer side of the second coating region 1232 of the positive electrode sheet 123 needs to be covered with the first coating region 1212 coated with negative active material. As shown in Figure 5 , the outer side of the second coating region 1232 of the positive electrode sheet 123 in the outermost circle is adjacent to the second circle of the negative electrode sheet 121 counted from the outside, so the inner side of the second circle of the negative electrode sheet 121 counted from the outside needs to be coated with negative active material, and the outer side of the second circle of the negative electrode sheet 121 counted from the outside is adjacent to the third empty foil region 1215 of the negative electrode sheet 121, so no negative active material needs to be coated. After the winding structure 124 is unfolded, as shown in Figure 6 , Figure 6 is a view of the inner and outer sides of the same negative electrode sheet 121, the outer side of the negative electrode sheet 121 is marked as surface A, and the inner side of the negative electrode sheet 121 is marked as surface B. As can be seen from Figure 6 , the difference between the length L0 of the second empty foil region 1214 and the length L1 of the third empty foil region 1215 in this embodiment is π(d1-a). In order to reduce the occurrence of lithium precipitation and improve the charging efficiency and safety of the battery, it is preferred that the first coating region 1212 on the inner side of the negative electrode sheet 121 is more than the second coating region 1232 of the positive electrode sheet 123, which will result in the length difference between the second empty foil region 1214 and the third empty foil region 1215 being less than the circumference of the second circle of the negative electrode sheet 121 counted from the outside, that is, L0-L1<π(d1-a).

[0064] Please refer to Figure 7 and Figure 8In the secondary battery 100 example of the utility model, the winding structure 124 includes the first adhesive tape 1241 for sealing the tail end, the first adhesive tape 1241 covers the tail end of the negative pole piece 121 and extends along the winding axis direction of the winding structure 124.It needs to be explained that the tail end of the winding structure 124 is the last section area of the winding structure 124 for tailing, and the tail end of the tail end is the edge at the end of the tail end.Because the tail end of the tail end of the winding structure 124 usually extends along the winding axis direction, the first adhesive tape 1241 extends along the winding axis direction of the winding structure 124 to seal the tail end of the winding structure 124.The width and length of the first adhesive tape 1241 are not limited, which can fix the tail end.The setting can cover a larger area of the tail end, which is conducive to avoiding the winding structure 124 tail end on the one hand, and can retain the effective contact area of the second empty foil area 1214 and the inner wall of the shell 110 to a large extent on the other hand.

[0065] Please refer to Figure 9 And Figure 10 In the secondary battery 100 example of the utility model, the winding structure 124 includes the first adhesive tape 1241 for sealing the tail end, the first adhesive tape 1241 covers the tail end of the negative pole piece 121 and extends along the winding axis direction of the winding structure 124.It needs to be explained that the tail end of the winding structure 124 is the last section area of the winding structure 124 for tailing, and the tail end of the tail end is the edge at the end of the tail end.Because the tail end of the tail end of the winding structure 124 usually extends along the winding axis direction, the first adhesive tape 1241 extends along the winding axis direction of the winding structure 124 to seal the tail end of the winding structure 124.The width and length of the first adhesive tape 1241 are not limited, which can fix the tail end.The setting can cover a larger area of the tail end, which is conducive to avoiding the winding structure 124 tail end on the one hand, and can retain the effective contact area of the second empty foil area 1214 and the inner wall of the shell 110 to a large extent on the other hand.

[0066] In the secondary battery 100 example of the utility model, the material of the shell 110 is stainless steel.For example, it can be SUS340, SUS430, SUS304, 403, etc., which is not limited, and the stainless steel in the embodiment adopts SUS340.Because stainless steel has good corrosion resistance, it can prolong the service life of the shell 110.Stainless steel has high mechanical strength and toughness, and can withstand large mechanical stress, which can better protect the internal structure of the battery.Stainless steel also has high processing performance.Stainless steel does not need to be treated by rust prevention and corrosion resistance, which reduces the production cost.In addition, in the embodiment, the second empty foil area 1214 is in contact with the inner wall of the shell 110, which further increases the conductive path and realizes the effect of effectively reducing the resistance of the stainless steel shell 110, reduces the energy loss and heat generation.

[0067] In the secondary battery 100 example of the utility model, at least part of the third empty foil area 1215 is provided with expansion glue. The expansion glue is a material that can expand under certain conditions (such as water absorption, heat absorption, chemical reaction, etc.). In this embodiment, the expansion glue is a swelling glue that can expand after contacting water and electrolyte. The expansion glue is arranged in the third empty foil area 1215. It will not reduce the overall energy density of the battery nor reduce the area of the second empty foil area 1214 that can be used for conduction. By utilizing the swelling glue's property of swelling when it comes into contact with electrolyte, the winding structure 124 and the inner wall of the shell 110 can be in more sufficient contact, thereby increasing the effective contact area of the second empty foil area 1214 and the inner wall of the shell 110, and further reducing the resistance of the shell 110, reducing energy loss and heat generation.

[0068] Please refer to Figure 11 The utility model also provides a battery pack 10, battery pack 10 includes any one of above-mentioned secondary battery 100, in the utility model battery pack 10 an embodiment, battery pack 10 includes box 101, box cover 102 and multiple secondary batteries 100, multiple secondary batteries 100 are placed in box 101, and are connected in series or parallel with each other, or series and parallel hybrid, and the box cover 102 is capped on the box 101 to protect multiple secondary batteries 100. It should be noted that the battery pack 10 can also include a battery pack 10 thermal management system, a circuit board and other parts in addition to the utility model secondary battery 100. The battery pack 10 can be a battery module or a battery pack, and an energy storage cabinet. Here, it will not be described one by one.

[0069] Please refer to Figure 12The utility model still provides an electronic device 1, electronic device 1 includes the battery pack 10 of above-mentioned. Working part 11 is electrically connected with battery pack 10 to obtain the electric energy support. As an example, electronic device 1 is vehicle, and vehicle can be fuel automobile, gas automobile or new energy automobile, and new energy automobile can be pure electric vehicle, hybrid vehicle or range extended vehicle etc., but not limited to this. Working part 11 is vehicle body, and battery pack 10 is arranged at the bottom of vehicle body, and provides the electric energy support for the running of vehicle or the operation of electrical element in vehicle. However in some other embodiments, electronic device 1 can also be mobile phone, portable device, notebook computer, ship, spacecraft, electric toy and electric tool etc. Spacecraft includes airplane, rocket, space shuttle and spaceship etc. Working part 11 can be the unit component that can obtain the electric energy of battery pack 10 and make corresponding work, for example, the fan blade rotation unit of fan, the dust collection work unit of dust collector etc. Electric toy includes fixed or mobile electric toy, for example, game machine, electric car toy, electric ship toy and electric plane toy etc. Electric tool includes metal cutting electric tool, grinding electric tool, assembly electric tool and railway electric tool, for example, electric drill, electric grinder, electric wrench, electric screwdriver, electric hammer, impact drill, concrete vibrator and electric planer etc. The embodiment of the application does not specially limit the above-mentioned electronic device 1.

[0070] The utility model discloses a secondary battery, electrode assembly includes the positive pole sheet, diaphragm and negative pole sheet laminated and is wound and forms the winding structure, and the tail end of negative pole sheet includes the diaphragm that protrudes, and located the second empty foil area of negative pole sheet side that deviates from winding shaft, and the second empty foil area is the end of winding structure. The second empty foil area can conduct electricity, and the second empty foil area is used as the end, when electrode assembly energization expansion, the second empty foil area can contact with side wall to realize negative pole sheet and shell direct conductive connection. The setting increases the conductive path, can effectively reduce the shell resistance, reduces energy loss and heat production. Therefore, the utility model discloses effectively overcome some practical problems in prior art thereby have very high utilization value and use significance. The above-mentioned embodiment is only illustrative to the principle and effect of the utility model, and is not used for limiting the utility model. Any person skilled in the art can modify or change the above-mentioned embodiment without departing from the spirit and scope of the utility model. Therefore, all equivalent modifications or changes completed by those skilled in the art under the spirit and technical thought disclosed by the utility model still should be covered by the claims of the utility model.

Claims

1. A secondary battery characterized by comprising: The secondary battery comprises: a shell comprising an end wall and a side wall surrounding the end wall; an electrode assembly accommodated in the shell, the electrode assembly comprising a positive electrode sheet, a separator, and a negative electrode sheet laminated and wound to form a wound structure, the negative electrode sheet comprising a first empty foil area extending out of the separator along a winding axis direction of the wound structure, the first empty foil area being electrically connected to the shell; wherein a tail end of the negative electrode sheet comprises a second empty foil area, the second empty foil area extending out of the separator at least partially along a winding direction of the wound structure and being located on a side of the negative electrode sheet away from the winding axis, the second empty foil area being a tail end of the wound structure.

2. The secondary battery according to claim 1, characterized by An inner diameter of the shell is d0, and a length of the second empty foil area along the winding direction of the wound structure is L0, wherein L0>πd0.

3. The secondary battery according to claim 2, characterized by L0<3πd0.

4. The secondary battery according to claim 1, characterized by The tail end of the negative electrode sheet further comprises a third empty foil area, the third empty foil area being located on a side of the negative electrode sheet facing the winding axis, a length of the second empty foil area along the winding direction of the wound structure is L0, and a length of the third empty foil area is L1, wherein L1=L0.

5. The secondary battery according to claim 1, characterized by A diameter of the wound structure is d1, a sum of a thickness of one layer of the positive electrode sheet, a thickness of one layer of the negative electrode sheet, and a thickness of two layers of the separator is a, the tail end of the negative electrode sheet further comprises a third empty foil area, the third empty foil area being located on a side of the negative electrode sheet away from the winding axis, a length of the second empty foil area along the winding direction of the wound structure is L0, and a length of the third empty foil area is L1, wherein L0-L1<π(d1-a).

6. The secondary battery according to any one of claims 1 to 5, characterized by, The wound structure comprises a first adhesive tape for sealing the tail end, the first adhesive tape covering the tail end of the negative electrode sheet and extending along the winding axis direction of the wound structure.

7. The secondary battery according to any one of claims 1 to 5, characterized by, The wound structure comprises a plurality of second adhesive tapes for sealing the tail end, the second adhesive tapes covering the tail end of the negative electrode sheet and extending along the winding direction of the wound structure, and the plurality of second adhesive tapes are arranged at intervals along the winding axis direction of the wound structure.

8. The secondary battery according to claim 1, characterized by The shell is made of stainless steel.

9. The secondary battery according to claim 4, characterized by At least a part of the third empty foil area is provided with an expansion adhesive.

10. A battery pack characterized by comprising: The secondary battery comprises any one of claims 1 to 9.

11. An electronic device, comprising: The battery pack comprises claim 10.

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