Secondary battery and electronic device

Abstract

The invention discloses a secondary battery and an electronic device. The secondary battery includes a first case, a second case, and an electrode assembly. The first shell comprises a first part and a second part, and the second part is arranged on the edge of the first part in a surrounding mode. The second shell comprises a third part and a fourth part, and the fourth part surrounds the edge of the third part; the second shell and the first shell are mutually covered, and the second shell and the first shell are in insulated connection. The electrode assembly comprises a plurality of first pole pieces and a plurality of second pole pieces, and the first pole piece located on the outermost side of the electrode assembly is a first sub-pole piece; and the second pole piece positioned on the outermost side of the electrode assembly is a second sub-pole piece. The first sub-pole piece comprises a first current collector, the first current collector is provided with a first surface and a second surface which are opposite, and the first surface is electrically connected with the first part; the second sub-pole piece comprises a second current collector, the second current collector is provided with a third face and a fourth face which are opposite, and the third face is electrically connected with the third part. According to the scheme, the size of the secondary battery is reduced, and the volume energy density of the secondary battery is improved.

Description

Technical Field

[0001] The present application relates to the field of energy storage technology, and in particular to a secondary battery and an electronic device. Background Art

[0002] In secondary batteries, the requirements for battery energy density are getting higher and higher. In related secondary batteries, the cathode uses a pole to lead out polarity. The part of the pole that is recessed into the shell will occupy a certain size, resulting in a larger gap between the cathode head ear and the shell. The part of the pole that protrudes outside the shell will also occupy the size of the secondary battery, resulting in energy density loss. Summary of the invention

[0003] In view of this, it is necessary to provide a secondary battery and an electronic device that can reduce the size of the secondary battery and improve the volume energy density of the secondary battery.

[0004] The embodiment of the first aspect of the present application provides a secondary battery, including: a first shell, a second shell and an electrode assembly. The first shell is a conductor; the first shell includes a first part and a second part, the second part is arranged around the edge of the first part, and is enclosed with the first part to form a first cavity. The second shell is a conductor; the second shell includes a third part and a fourth part, the fourth part is arranged around the edge of the third part, and is enclosed with the third part to form a second cavity; the second shell and the first shell cover each other, the first cavity and the second cavity are connected to form a receiving cavity, and the second shell is insulated from the first shell. The electrode assembly is received in the receiving cavity; the electrode assembly includes a plurality of first pole pieces and a plurality of second pole pieces, the plurality of first pole pieces are electrically connected, and the plurality of second pole pieces are electrically connected; the first pole piece located at the outermost side of the electrode assembly is the first sub-pole piece; the second pole piece located at the outermost side of the electrode assembly is the second sub-pole piece. The first sub-pole piece and the second sub-pole piece are respectively located at the two outermost sides in the thickness direction of the electrode assembly. The first sub-pole sheet includes a first current collector and a first active material layer, the first current collector has a first surface and a second surface opposite to each other, the first surface is the surface of the first current collector away from the second sub-pole sheet, the first surface is provided with a first empty foil area, the first empty foil area is electrically connected to the first part, and the first active material layer is provided on the second surface; the second sub-pole sheet includes a second current collector and a second active material layer, the second current collector has a third surface and a fourth surface opposite to each other, the third surface is the surface of the second current collector away from the first sub-pole sheet, the third surface is provided with a second empty foil area, the second empty foil area is electrically connected to the third part, and the second active material layer is provided on the fourth surface.

[0005] By setting an empty foil area on one side of the first current collector and the second current collector, the first side of the first current collector is directly electrically connected to the first shell through the first empty foil area, and the third side of the second current collector is directly electrically connected to the second shell through the second empty foil area. The first pole piece and the second pole piece can lead out the polarity through the first shell and the second shell, without setting poles on the first shell and the second shell. Compared with the solution of leading out the polarity through the pole ear, this solution does not need to reserve space for the welding fixture, which is conducive to reducing the overall size of the secondary battery and improving the volume energy density of the secondary battery. In addition, compared with the solution of connecting the pole ear to the shell, this solution can reduce the situation of the pole ear and the shell being pulled and broken when falling, thereby improving the safety performance of the secondary battery.

[0006] In at least one embodiment, along the thickness direction of the secondary battery, the first pole sheet and the second pole sheet are arranged in sequence; the electrode assembly also includes a plurality of first pole tabs, the first pole tabs are electrically connected to the first current collector, and the plurality of first pole tabs are gathered to form a first pole tab group; the electrode assembly also includes a plurality of second pole tabs, the second pole tabs are electrically connected to the second current collector, and the plurality of second pole tabs are gathered to form a second pole tab group.

[0007] The setting of the first pole lug group realizes the electrical connection between multiple first pole pieces, so that the multiple first pole pieces can export the polarity to the first shell through the first sub-pole piece; the setting of the second pole lug group realizes the electrical connection between multiple second pole pieces, so that the multiple second pole pieces can export the polarity to the second shell through the second sub-pole piece.

[0008] In at least one embodiment, along the thickness direction of the secondary battery, multiple first pole sheets and multiple second pole sheets are stacked to form the main body of the electrode assembly, the first pole tab group is stacked between the second part and the main body or between the fourth part and the main body, and the second pole tab group is stacked between the fourth part and the main body or between the second part and the main body.

[0009] The first tab group and the second tab group are stacked respectively, which is beneficial to reducing the space occupied by the first tab group and the second tab group in the receiving cavity, and also reduces the overall space occupied by the electrode assembly, which is beneficial to improving the volume energy density of the secondary battery.

[0010] In at least one embodiment, the secondary battery includes a first adhesive member, which is a conductor; the first adhesive member is bonded between the first surface and the first portion, and / or the first adhesive member is bonded between the third surface and the third portion.

[0011] On the one hand, the first adhesive can fix the electrode assembly to the first part or the third part, so that the electrode assembly is not easy to shake in the receiving cavity during the drop test, thereby improving the drop performance of the secondary battery. On the other hand, the first adhesive as a conductor can improve the electrical connection stability between the first surface and the first shell or the electrical connection stability between the third surface and the second shell.

[0012] In at least one embodiment, the first portion has a first conductive surface, the first conductive surface is provided with a first convex portion, and the first convex portion is electrically connected to the first surface; and / or, The third portion has a second conductive surface, the second conductive surface is provided with a second convex portion, and the second convex portion is electrically connected to the third surface.

[0013] The cooperation between the first protrusion and the first surface is conducive to improving the friction between the first surface and the first conductive surface, so that the electrode assembly and the first shell are not easily moved relative to each other, and the conductive stability between the first sub-pole piece and the first shell is improved. The cooperation between the second protrusion and the third surface is conducive to improving the friction between the third surface and the second conductive surface, so that the electrode assembly and the second shell are not easily moved relative to each other, and the conductive stability between the second sub-pole piece and the second shell is improved.

[0014] In at least one embodiment, the second shell includes a second adhesive, which is filled between the first surface and the first conductive surface, and the second adhesive is located in a portion of the first conductive surface where the first protrusion is not provided, and / or the second adhesive is located in a portion of the second conductive surface where the second protrusion is not provided.

[0015] The second adhesive can further improve the conductivity stability between the first surface and the first conductive surface and / or the third surface and the second conductive surface. And the second adhesive can avoid the first protrusion, so that the first surface and the first shell are electrically connected through the contact between the first protrusion and the first surface. And / or, the second adhesive can avoid the second protrusion, so that the third surface and the second shell are electrically connected through the contact between the second protrusion and the third surface.

[0016] In at least one embodiment, the second portion has a first edge, and the fourth portion has a second edge; along the thickness direction of the secondary battery, the first shell and the second shell are connected and covered by aligning the first edge with the second edge.

[0017] In at least one embodiment, the secondary battery also includes an insulating seal, which includes a first sealing portion, a second sealing portion and a third sealing portion, the third sealing portion is connected between the first sealing portion and the second sealing portion, the first sealing portion is wrapped around and bonded to the outer periphery of the second portion, and the second sealing portion is wrapped around and bonded to the outer periphery of the fourth portion; an insulating gap is formed between the first shell and the second shell, and the third sealing portion seals the insulating gap.

[0018] By providing the insulating seal, insulation between the first shell and the second shell is achieved, and the sealing of the receiving cavity is achieved.

[0019] In at least one embodiment, the peeling force between the insulating seal and the first shell and the second shell is F, and F≥0.5N / mm 2 .

[0020] Since the electrode assembly is closely attached to the first shell and the second shell through the first sub-electrode sheet and the second sub-electrode sheet, it is necessary to resist the expansion force caused by the expansion of the electrode assembly during the long-term use of the secondary battery. The peeling force is F ≥ 0.5N / mm 2 This helps the insulating seal to overcome the above expansion force and improves the sealing performance of the secondary battery when it is subjected to the expansion force of the electrode assembly.

[0021] In at least one embodiment, F ≥ 1 N / mm 2 , further improving the sealing performance of the secondary battery when it is subjected to the expansion force of the electrode assembly.

[0022] In at least one embodiment, the first sealing portion, the second sealing portion and the third sealing portion are integrally arranged.

[0023] The integrated setting can directly bond the entire insulating seal to the first shell and the second shell, reducing the bonding steps; on the other hand, it reduces the joint seams formed between the third sealing part and the second sealing part and the first sealing part, thereby improving the sealing effect of the insulating seal.

[0024] In at least one embodiment, the width of the first sealing portion is W 1 , meet: 0.1mm≤W 1 ≤3mm; and / or, the width of the second sealing portion is W 2 , meet: 0.1mm≤W 2 ≤3mm.

[0025] Ensure that the insulating seal has sufficient bonding area with the first shell and the second shell, thereby improving the sealing between the first shell and the second shell and improving the long-term sealing effect of the secondary battery. And make the bonding width not easy to be too large, which is conducive to reducing the impact on the volume of the secondary battery and reducing the volume energy density loss of the secondary battery.

[0026] In at least one embodiment, 0.3 mm ≤ W 1 ≤1.5mm, and / or, 0.3mm≤W 2 ≤1.5mm. On the premise of improving the long-term sealing effect of the secondary battery, the energy density of the secondary battery is further improved.

[0027] In at least one embodiment, at least a portion of the third sealing portion is located in the insulating gap.

[0028] On the one hand, the third sealing part can support the first shell and the second shell, which is beneficial to maintaining the insulation gap so that the first shell and the second shell are insulated; on the other hand, the third sealing part can also seal the insulation gap to ensure the sealing between the first shell and the second shell.

[0029] A second aspect of the present application provides an electronic device, comprising the secondary battery in any one of the above embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 is a three-dimensional diagram of a secondary battery in one embodiment of the present application.

[0031] Figure 2 yes Figure 1 Exploded view of a secondary battery in FIG.

[0032] Figure 3 is a schematic diagram of an electrode assembly in one embodiment of the present application.

[0033] Figure 4 This is a cross-sectional view of a secondary battery in one embodiment of the present application, showing the connection relationship between the first pole piece and the first shell.

[0034] Figure 5 yes Figure 4 Enlarged view of part V.

[0035] Figure 6 This is a cross-sectional view of a secondary battery in an embodiment of the present application, showing the connection relationship between the second pole piece and the second shell.

[0036] Figure 7 yes Figure 6 Enlarged view of part VII.

[0037] Figure 8 This is a partial cross-sectional view of an embodiment of the present application showing the connection relationship between the first portion and the first sub-pole piece.

[0038] Fig. 9 This is a partial cross-sectional view of an embodiment of the present application, showing the connection relationship between the third portion and the second sub-pole piece.

[0039] Fig.10 This is a partial cross-sectional view of an embodiment of the present application, showing the connection relationship between the first protrusion and the first surface.

[0040] Fig.11 It is a partial cross-sectional view of an embodiment of the present application, showing the connection relationship between the first convex portion and the first concave portion.

[0041] Fig.12 This is a partial cross-sectional view of an embodiment of the present application, showing the connection relationship between the second protrusion and the third surface.

[0042] Fig.13 It is a partial cross-sectional view of an embodiment of the present application, showing the connection relationship between the second protrusion and the second recess.

[0043] Fig.14This is a partial cross-sectional view of a secondary battery in one embodiment of the present application, showing the connection relationship between the outer shell and the insulating seal.

[0044] Fig.15 is a schematic diagram of an electronic device in one embodiment of the present application.

[0045] Main component symbols 1000, electronic device; 100, secondary battery; 10, electrode assembly; 10a, first pole lug group; 10b, second pole lug group; 10c, main body; 11, first pole piece; 11a, first sub-pole piece; 111, first current collector; 1111, first surface; 1112, second surface; 1113, first recess; 112, first active material layer; 12, second pole piece; 12a, second sub-pole piece; 121, second current collector; 1211, third surface; 1212, fourth surface; 1213, second recess; 122, second active material layer; 13, separator; 14, first pole lug; 15 , second pole ear; 20, outer shell; 21, first shell; 211, first part; 2111, first conductive surface; 2112, first convex part; 212, second part; 2121, first edge; 213, first cavity; 22, second shell; 221, third part; 2211, second conductive surface; 2212, second convex part; 222, fourth part; 2221, second edge; 223, second cavity; 23, insulating gap; 30, first adhesive; 40, second adhesive; 50, insulating seal; 51, first sealing part; 52, second sealing part; 53, third sealing part; X, first direction.

[0046] The following specific implementation methods will further illustrate the present application in conjunction with the above-mentioned drawings. DETAILED DESCRIPTION

[0047] The technical solutions in the embodiments of the present application will be described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all of the embodiments.

[0048] In the description of the embodiments of the present application, technical terms such as "first" and "second" are only used to distinguish different objects and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features.

[0049] In secondary batteries, the requirements for battery energy density are getting higher and higher. In related secondary batteries, the cathode uses a pole to lead out polarity. The part of the pole that is recessed into the shell will occupy a certain size, resulting in a larger gap between the cathode head ear and the shell. The part of the pole that protrudes outside the shell will also occupy the size of the secondary battery, resulting in energy density loss.

[0050] The embodiment of the first aspect of the present application provides a secondary battery, including: a first shell, a second shell and an electrode assembly. The first shell is a conductor; the first shell includes a first part and a second part, the second part is arranged around the edge of the first part, and is enclosed with the first part to form a first cavity. The second shell is a conductor; the second shell includes a third part and a fourth part, the fourth part is arranged around the edge of the third part, and is enclosed with the third part to form a second cavity; the second shell and the first shell cover each other, the first cavity and the second cavity are connected to form a receiving cavity, and the second shell is insulated from the first shell. The electrode assembly is received in the receiving cavity; the electrode assembly includes a plurality of first pole pieces and a plurality of second pole pieces, the plurality of first pole pieces are electrically connected, and the plurality of second pole pieces are electrically connected; the first pole piece located at the outermost side of the electrode assembly is the first sub-pole piece; the second pole piece located at the outermost side of the electrode assembly is the second sub-pole piece. The first sub-pole piece and the second sub-pole piece are respectively located at the two outermost sides in the thickness direction of the electrode assembly. The first sub-pole sheet includes a first current collector and a first active material layer, the first current collector has a first surface and a second surface opposite to each other, the first surface is the surface of the first current collector away from the second sub-pole sheet, the first surface is provided with a first empty foil area, the first empty foil area is electrically connected to the first part, and the first active material layer is provided on the second surface; the second sub-pole sheet includes a second current collector and a second active material layer, the second current collector has a third surface and a fourth surface opposite to each other, the third surface is the surface of the second current collector away from the first sub-pole sheet, the third surface is provided with a second empty foil area, the second empty foil area is electrically connected to the third part, and the second active material layer is provided on the fourth surface.

[0051] By setting an empty foil area on one side of the first current collector and the second current collector, the first side of the first current collector is directly electrically connected to the first shell through the first empty foil area, and the third side of the second current collector is directly electrically connected to the second shell through the second empty foil area. The first pole piece and the second pole piece can lead out the polarity through the first shell and the second shell, without setting poles on the first shell and the second shell. Compared with the solution of leading out the polarity through the pole ear, this solution does not need to reserve space for the welding fixture, which is conducive to reducing the overall size of the secondary battery and improving the volume energy density of the secondary battery. In addition, compared with the solution of connecting the pole ear to the shell, this solution can reduce the situation of the pole ear and the shell being pulled and broken when falling, thereby improving the safety performance of the secondary battery.

[0052] The embodiments of the present application are further described below in conjunction with the accompanying drawings.

[0053] like Figures 1 to 3As shown, the first embodiment of the present application provides a secondary battery 100, the secondary battery 100 includes an electrode assembly 10 and a housing 20, the housing 20 has a receiving cavity, and the electrode assembly 10 is received in the receiving cavity. The electrode assembly 10 includes a first pole piece 11, a second pole piece 12 and a diaphragm 13, the diaphragm 13 is disposed between the first pole piece 11 and the second pole piece 12, and the diaphragm 13 is used to isolate the first pole piece 11 and the second pole piece 12.

[0054] In some embodiments, the housing 20 is a hard housing, for example, the housing 20 includes a metal housing of at least one of a steel alloy, an aluminum alloy, and a copper alloy.

[0055] In some embodiments, an electrolyte (not shown) is injected into the receiving cavity of the housing 20 , and the electrolyte components include a solvent, an electrolyte salt, and an additive.

[0056] In some embodiments, the electrolyte salt includes at least one of an organic lithium salt or an inorganic lithium salt.

[0057] In some embodiments, the polarities of the first electrode 11 and the second electrode 12 are different. For example, the first electrode 11 is an anode electrode, and the second electrode 12 is a cathode electrode. For another example, the first electrode 11 is a cathode electrode, and the second electrode 12 is an anode electrode.

[0058] See also Figure 3 In some embodiments, the first pole piece 11 includes a first current collector 111 and a first active material layer 112. Along the thickness direction of the first pole piece 11, the first current collector 111 includes two oppositely disposed surfaces, and the first active material layer 112 is disposed on at least one surface of the first current collector 111 along the thickness direction of the first current collector 111. The thickness direction of the first current collector 111 is consistent with the thickness direction of the first pole piece 11, both being the first direction X.

[0059] See also Figure 3 In some embodiments, the second pole piece 12 includes a second current collector 121 and a second active material layer 122. Along the thickness direction of the second pole piece 12, the second current collector 121 has two oppositely disposed surfaces, and the thickness direction of the second pole piece 12 is consistent with the thickness direction of the second current collector 121. Along the thickness direction of the second current collector 121, the second active material layer 122 is disposed on at least one surface of the second current collector 121. The thickness direction of the second current collector 121 is the first direction X.

[0060] See also Figure 1 and Figure 2In some embodiments, the first shell 21 is a conductor. The first shell 21 includes a first portion 211 and a second portion 212, the second portion 212 is arranged around the edge of the first portion 211, and is enclosed with the first portion 211 to form a first cavity 213. The second shell 22 is a conductor. The second shell 22 includes a third portion 221 and a fourth portion 222, the fourth portion 222 is arranged around the edge of the third portion 221, and is enclosed with the third portion 221 to form a second cavity 223. The second shell 22 and the first shell 21 cover each other, the first cavity 213 and the second cavity 223 are connected to form a receiving cavity, and the second shell 22 is insulated and connected to the first shell 21.

[0061] See also Figures 3 to 5 The electrode assembly 10 includes a plurality of first pole pieces 11 and a plurality of second pole pieces 12. The plurality of first pole pieces 11 are electrically connected to each other, and the plurality of second pole pieces 12 are electrically connected to each other. The first pole piece 11 located at the outermost side of the electrode assembly 10 is the first sub-pole piece 11a, and the second pole piece 12 located at the outermost side of the electrode assembly 10 is the second sub-pole piece 12a. The first sub-pole piece 11a and the second sub-pole piece 12a are located at the two outermost sides in the thickness direction of the electrode assembly 10, respectively. It can be understood that Figure 3 It is only used to illustrate the positional relationship between the first sub-pole piece 11 a , the second sub-pole piece 12 a and the inner pole piece, and does not limit the number of the first pole piece 11 and the second pole piece 12 in the electrode assembly 10 .

[0062] The first sub-electrode sheet 11a includes a first current collector 111 and a first active material layer 112. Along the thickness direction of the first current collector 111, the first current collector 111 has a first surface 1111 and a second surface 1112 relative to each other. The first surface 1111 is the surface of the first current collector 111 away from the second sub-electrode sheet 12a. The first surface 1111 is provided with a first empty foil area, and the first empty foil area is electrically connected to the first part 211. The first active material layer 112 of the first sub-electrode sheet 11a is provided on the second surface 1112. The second sub-pole sheet 12a includes a second current collector 121 and a second active material layer 122. Along the thickness direction of the second current collector 121, the second current collector 121 has a third surface 1211 and a fourth surface 1212 relative to each other. The third surface 1211 is the surface of the second current collector 121 away from the first sub-pole sheet 11a. The third surface 1211 is provided with a second empty foil area, and the second empty foil area is electrically connected to the third part 221. The second active material layer 122 of the second sub-pole sheet 12a is provided on the fourth surface 1212.

[0063] By setting an empty foil area on one side of the first current collector 111 and the second current collector 121, the first side 1111 of the first current collector 111 is directly electrically connected to the first shell 21 through the first empty foil area, and the third side 1211 of the second current collector 121 is directly electrically connected to the second shell 22 through the second empty foil area. The first pole piece 11 and the second pole piece 12 can lead out the polarity through the first shell 21 and the second shell 22, without setting poles on the first shell 21 and the second shell 22. Compared with the solution of leading out the polarity through the pole ear, this solution does not need to reserve space for the welding jig, which is conducive to reducing the overall size of the secondary battery 100 and improving the volume energy density of the secondary battery 100. In addition, compared with the solution of connecting the pole ear to the shell 20, this solution can reduce the situation of the pole ear and the shell 20 being pulled and broken when falling, and improve the safety performance of the secondary battery 100.

[0064] It can be understood that after the secondary battery 100 is used, the electrode assembly 10 will expand to a certain extent in the thickness direction. In the expanded electrode assembly 10, the first sub-pole sheet 11a is deformed toward the first part 211, thereby increasing the force between the first surface 1111 and the first part 211, and improving the electrical connection stability between the first sub-pole sheet 11a and the first shell 21; the second sub-pole sheet 12a is deformed toward the third part 221, thereby increasing the force between the third surface 1211 and the third part 221, and improving the electrical connection stability between the second sub-pole sheet 12a and the second shell 22.

[0065] In some embodiments, a portion of the area on the first surface 1111 of the first current collector 111 is set as the first empty foil area, or the entire area on the first surface 1111 of the first current collector 111 is set as the first empty foil area. Compared with the solution of setting only a portion of the area as the first empty foil area, the solution of setting the entire area as the first empty foil area can improve the electrical connection effect between the first surface 1111 and the first housing 21.

[0066] In some embodiments, a portion of the area on the third surface 1211 of the second current collector 121 is set as the second empty foil area, or the entire area on the third surface 1211 of the second current collector 121 is set as the second empty foil area. Compared with the solution of setting only a portion of the area as the second empty foil area, the solution of setting the entire area as the second empty foil area can improve the electrical connection effect between the third surface 1211 and the second housing 22.

[0067] In some embodiments, the first empty foil area is the surface of the first current collector 111 where the first active material layer 112 is not provided, but a small amount of active material is present and does not affect the electrical connection effect and also falls within the scope of the first empty foil area. The second empty foil area is the surface of the second current collector 121 where the second active material layer 122 is not provided, but a small amount of active material is present and does not affect the electrical connection effect and also falls within the scope of the second empty foil area.

[0068] See also Figure 2 In some embodiments, the first portion 211 and the third portion 221 are arranged in a flat plate shape and form the top and bottom of the housing 20 , and the second portion 212 and the fourth portion 222 form the side of the housing 20 .

[0069] See also Figure 2 and Figure 4 In some embodiments, the second portion 212 has a first edge 2121, and the fourth portion 222 has a second edge 2221. Along the thickness direction of the secondary battery 100, the first shell 21 and the second shell 22 are covered by aligning and connecting the first edge 2121 and the second edge 2221. An insulating gap 23 is formed between the first edge 2121 and the second edge 2221. In the "aligned connection" here, "aligned" means that the shape and size of the first edge 2121 and the second edge 2221 are substantially the same, and an error is allowed when the first edge 2121 and the second edge 2221 are aligned; wherein "connected" is an indirect connection, for example, the first edge 2121 and the second edge 2221 are connected by insulating tape.

[0070] Compared with the solution of staggered connection between the first edge 2121 and the second edge 2221, the solution of aligning the first edge 2121 and the second edge 2221 can reduce the overall size of the first shell 21 and the second shell 22 after they are covered, thereby helping to reduce the volume of the secondary battery 100 and improve the volume energy density of the secondary battery 100.

[0071] See also Figures 4 to 7 In some embodiments, the first pole piece 11 and the second pole piece 12 are sequentially arranged at intervals along the thickness direction of the secondary battery 100. The electrode assembly 10 further includes a plurality of first pole tabs 14, which are electrically connected to the first current collector 111, and the plurality of first pole tabs 14 are gathered to form a first pole tab group 10a; the electrode assembly 10 further includes a plurality of second pole tabs 15, which are electrically connected to the second current collector 121, and the plurality of second pole tabs 15 are gathered to form a second pole tab group 10b.

[0072] The first tab group 10a is provided to realize electrical connection between the plurality of first pole pieces 11, so that the plurality of first pole pieces 11 can lead polarity to the first housing 21 through the first sub-pole piece 11a. The second tab group 10b is provided to realize electrical connection between the plurality of second pole pieces 12, so that the plurality of second pole pieces 12 can lead polarity to the second housing 22 through the second sub-pole piece 12a.

[0073] In some embodiments, the first tab group 10a and the second tab group 10b are not directly connected in structure, so that the first tab 14 and the second tab 15 are not easily broken by the casing 20 in a falling condition, thereby improving the anti-fall performance of the secondary battery 100.

[0074] In some embodiments, the first tab group 10a and the second tab group 10b are arranged on the same side of the electrode assembly 10 in the length direction, thereby reducing the size occupied by the first tab group 10a and the second tab group 10b in the length direction of the electrode assembly 10, which is beneficial to reducing the volume of the secondary battery 100.

[0075] See also Figure 5 and Figure 7 In some embodiments, a plurality of first pole pieces 11 and a plurality of second pole pieces 12 are stacked to form the main body 10c of the electrode assembly 10, the first pole tab group 10a is stacked between the second portion 212 and the main body 10c or between the fourth portion 222 and the main body 10c, and the second pole tab group 10b is stacked between the fourth portion 222 and the main body 10c or between the second portion 212 and the main body 10c. Figure 5 As shown in , the first tab group 10a is stacked between the second portion 212 and the main body portion 10c; Figure 7 As shown in FIG. 1 , the second electrode tab group 10 b is stacked between the fourth portion 222 and the main body portion 10 c.

[0076] The first electrode tab group 10a and the second electrode tab group 10b are stacked, respectively, so as to reduce the occupied space of the first electrode tab group 10a and the second electrode tab group 10b in the receiving cavity, and also reduce the overall occupied space of the electrode assembly 10. Figure 4 and Figure 6 As can be seen from the figure, the first tab group 10a and the second tab group 10b are stacked on the side of the secondary battery 100, thereby reducing the space occupied in the thickness direction of the secondary battery 100, which is beneficial to improving the volume energy density of the secondary battery 100.

[0077] See also Figure 8 In some embodiments, the secondary battery 100 includes a first adhesive member 30 , which is a conductor and is bonded between the first surface 1111 and the first portion 211 .

[0078] On the one hand, the first adhesive 30 can fix the electrode assembly 10 to the first portion 211, so that in a drop test, the electrode assembly 10 is not easy to shake relative to the first shell 21, thereby improving the drop performance of the secondary battery 100. On the other hand, the first adhesive 30, as a conductor, can improve the electrical connection stability between the first surface 1111 and the first shell 21.

[0079] See also Fig. 9In some embodiments, the first adhesive member 30 is bonded between the third surface 1211 and the third portion 221. The first adhesive member 30 can fix the electrode assembly 10 to the third portion 221, so that in a drop test, the electrode assembly 10 is not easy to shake relative to the second shell 22, thereby improving the drop performance of the secondary battery 100. In addition, the first adhesive member 30, as a conductor, can improve the electrical connection stability between the third surface 1211 and the second shell 22.

[0080] In some embodiments, two first adhesive members 30 are provided, wherein one first adhesive member 30 is provided between the first surface 1111 and the first portion 211, and the other first adhesive member 30 is provided between the third surface 1211 and the third portion 221, so as to improve the stability of the electrical connection between the electrode assembly 10 and the first shell portion and the second shell portion.

[0081] See also Fig.10 and Fig.11 In some embodiments, the first portion 211 has a first conductive surface 2111, and the first conductive surface 2111 is provided with a first convex portion 2112, and the first convex portion 2112 is electrically connected to the first surface 1111 of the first current collector 111. For example, the first convex portion 2112 is a burr structure. Specifically, the burr structure is formed on the first conductive surface 2111 by a process such as laser roughening, such as Fig.10 As shown, the burr structure penetrates into the first current collector 111 from the first surface 1111. Alternatively, as shown in Fig.11 As shown, under the action of the first convex portion 2112 , the first current collector 111 is deformed to form a first concave portion 1113 , so that the first convex portion 2112 extends into the first concave portion 1113 , thereby achieving electrical connection between the first convex portion 2112 and the first concave portion 1113 .

[0082] The cooperation between the first protrusion 2112 and the first current collector 111 is conducive to improving the friction between the first surface 1111 and the first conductive surface 2111, so that the electrode assembly 10 and the first shell 21 are not easy to move relative to each other, thereby improving the conductive stability between the first sub-electrode sheet 11a and the first shell 21.

[0083] See also Fig.10 or Fig.11 In some embodiments, the second housing 22 includes a second adhesive 40, which is filled between the first surface 1111 and the first conductive surface 2111, and is located at a portion of the first conductive surface 2111 where the first convex portion 2112 is not provided. The second adhesive 40 can further improve the conductive stability between the first surface 1111 and the first conductive surface 2111. In addition, the second adhesive 40 can avoid the first convex portion 2112, so that the first surface 1111 and the first housing 21 are electrically connected to the first current collector 111 through the first convex portion 2112.

[0084] See also Fig.12 and Fig.13 In some embodiments, the third portion 221 has a second conductive surface 2211, and the second conductive surface 2211 is provided with a second convex portion 2212, and the second convex portion 2212 is electrically connected to the third surface 1211 of the second current collector 121. For example, the second convex portion 2212 is a burr structure. Specifically, the burr structure is formed on the second conductive surface 2211 by a process such as laser roughening. Fig.12 As shown, the burr structure penetrates into the second current collector 121 from the third surface 1211. Alternatively, as Fig.13 As shown, under the action of the second convex portion 2212 , the second current collector 121 is deformed to form a second concave portion 1213 , so that the second convex portion 2212 extends into the second concave portion 1213 , thereby achieving electrical connection between the second convex portion 2212 and the second concave portion 1213 .

[0085] The cooperation between the second protrusion 2212 and the second current collector 121 is conducive to improving the friction between the third surface 1211 and the second conductive surface 2211, so that the electrode assembly 10 and the second shell 22 are not easy to move relative to each other, thereby improving the conductive stability between the second sub-electrode sheet 12a and the second shell 22.

[0086] See also Fig.12 or Fig.13 In some embodiments, the second shell 22 includes a second adhesive 40 , which is filled between the third surface 1211 and the second conductive surface 2211 , and the second adhesive 40 is located at a portion of the second conductive surface 2211 where the second protrusion 2212 is not provided.

[0087] The second adhesive 40 can further improve the conductive stability between the third surface 1211 and the second conductive surface 2211. The second adhesive 40 can avoid the second protrusion 2212, so that the third surface 1211 and the second housing 22 are electrically connected through the contact between the second protrusion 2212 and the second current collector 121.

[0088] In some embodiments, the second adhesive member 40 is a glue layer, and the material of the glue layer can be polypropylene or other materials.

[0089] In some embodiments, the materials of the first shell 21, the first current collector 111 and the first pole tab 14 include the same metal material, and the materials of the second shell 22, the second current collector 121 and the second pole tab 15 include the same metal material, so as to reduce the potential difference between the first pole piece 11 and the first shell 21, reduce the potential difference between the second pole piece 12 and the second shell 22, and reduce the risk of electrochemical corrosion. For example, the first current collector 111 and the first pole tab 14 are both made of metal aluminum, and the first shell 21 is made of aluminum alloy; the second current collector 121 and the second pole tab 15 are both made of metal nickel, and the second shell 22 is made of nickel alloy.

[0090] See also Figure 1 and Fig.14 In some embodiments, the secondary battery 100 further includes an insulating seal 50, the insulating seal 50 includes a first sealing portion 51, a second sealing portion 52 and a third sealing portion 53, the third sealing portion 53 is connected between the first sealing portion 51 and the second sealing portion 52, the first sealing portion 51 is wrapped around and bonded to the outer periphery of the second portion 212, and the second sealing portion 52 is wrapped around and bonded to the outer periphery of the fourth portion 222. An insulating gap 23 is formed between the first shell 21 and the second shell 22, and the third sealing portion 53 seals the insulating gap 23. By setting the insulating seal 50, the insulation between the first shell 21 and the second shell 22 is achieved, and the sealing of the receiving cavity is achieved.

[0091] In addition, by eliminating the pole, there is no need to consider the sealing problem at the connection between the pole and the housing 20 , which can simplify the structure of the secondary battery 100 , reduce the risk points of leakage of the secondary battery 100 , and reduce the cost of the secondary battery 100 .

[0092] In some embodiments, since the electrode assembly 10 is tightly attached to the first shell 21 and the second shell 22 through the first sub-electrode sheet 11a and the second sub-electrode sheet 12a, it is necessary to resist the expansion force caused by the expansion of the electrode assembly 10 during long-term use of the secondary battery 100, so the adhesion of the insulating seal 50 needs to be enhanced.

[0093] In some embodiments, the peeling force between the insulating seal 50 and the first shell 21 and the second shell 22 is F, and F≥0.5N / mm 2 . Peel force: F≥0.5N / mm 2 , which is beneficial for the insulating seal 50 to overcome the above expansion force and improve the sealing performance of the secondary battery 100 when subjected to the expansion force of the electrode assembly 10.

[0094] In some embodiments, F ≥ 1 N / mm 2 , further improving the sealing performance of the secondary battery 100 when it is subjected to the expansion force of the electrode assembly 10.

[0095] In some embodiments, the testing method of the peeling force F is: taking an insulating seal 50 with a width of 6 mm as the test sample, setting the peeling speed to 20 mm / min, and after the insulating seal 50 is soaked in electrolyte at 85°C for 24 hours, the peeling force F between the insulating seal 50 and the first shell 21 and the second shell 22 is measured.

[0096] In some embodiments, the peeling force is improved by grafting maleic anhydride on the entire or a part of the insulating sealant 50 .

[0097] The insulating seal 50 is made of PP (polypropylene). The reason why the adhesion between maleic anhydride grafted polypropylene and metal is enhanced is the change in its chemical structure. The polarity of the grafted polypropylene is enhanced, and it forms a stronger interaction and chemical bonding with the metal surface. In addition, the polar groups will also increase hydrogen bonds and van der Waals forces, improve interfacial compatibility and surface wettability, thereby improving the bonding strength between the insulating seal 50 and the first shell 21 and the second shell 22. These factors work together to significantly enhance the adhesion between the grafted polypropylene and the metal. Specifically, the maleic anhydride grafting rate is set to 0.01%~5%. If the grafting rate is too low, the number of polar groups of maleic anhydride is insufficient, and the polarity of polypropylene and the adhesion to metal cannot be significantly improved; if the grafting rate is too high, the mechanical properties of polypropylene may decrease, such as reduced toughness and ductility. In addition, too many polar groups may cause phase separation or uneven distribution, which is not conducive to further improvement of adhesion.

[0098] See also Figure 1 and Fig.14 In some embodiments, the first sealing portion 51, the second sealing portion 52 and the third sealing portion 53 are integrally arranged. The integral arrangement can directly bond the entire insulating seal 50 to the first shell 21 and the second shell 22, reducing the bonding steps; on the other hand, it reduces the number of joints formed between the third sealing portion 53 and the second sealing portion 52 and the first sealing portion 51, thereby improving the sealing effect of the insulating seal 50.

[0099] See also Figure 1 and Fig.14 In some embodiments, the width of the first sealing portion 51 is W 1 , meet: 0.1mm≤W 1 ≤3mm. As shown in the figure, when the second part 212 is perpendicular to the first part 211, the width direction of the first sealing part 51 is the first direction X shown in the figure. Ensure that the insulating seal 50 and the first shell 21 have sufficient bonding area, thereby improving the sealing between the first shell 21 and the second shell 22 and improving the long-term sealing effect of the secondary battery 100. And make the bonding width not easy to be too large, that is: the first sealing part 51 is not easy to exceed the second part 212, which is conducive to reducing the impact on the volume of the secondary battery 100 and reducing the volume energy density loss of the secondary battery 100.

[0100] In some embodiments, 0.3 mm ≤ W 1 ≤1.5mm, which can further enhance the use safety of the secondary battery 100 while improving the long-term sealing effect of the secondary battery 100.

[0101] See also Figure 1 and Fig.14 In some embodiments, the width of the second sealing portion 52 is W 2, meet: 0.1mm≤W 2 ≤3mm. As shown in the figure, when the fourth part 222 is perpendicular to the third part 221, the width direction of the first sealing part 51 is the first direction X shown in the figure. Ensure that the insulating seal 50 and the second shell 22 have sufficient bonding area, thereby improving the sealing between the first shell 21 and the second shell 22 and improving the long-term sealing effect of the secondary battery 100. And make the bonding width not easy to be too large, that is: the second sealing part 52 is not easy to exceed the fourth part 222, which is conducive to reducing the impact on the volume of the secondary battery 100 and reducing the volume energy density loss of the secondary battery 100.

[0102] In some embodiments, 0.3 mm ≤ W 2 ≤1.5mm, which can further improve the energy density of the secondary battery 100 while improving the long-term sealing effect of the secondary battery 100.

[0103] See also Fig.14 In some embodiments, at least a portion of the third sealing portion 53 is located in the insulating gap 23. On the one hand, the third sealing portion 53 can support the first shell 21 and the second shell 22, which is conducive to maintaining the insulating gap 23, so that the first shell 21 and the second shell 22 are insulated; on the other hand, the third sealing portion 53 can also seal the insulating gap 23 to ensure the sealing between the first shell 21 and the second shell 22.

[0104] See also Fig.15 , an embodiment of the present application further provides an electronic device 1000, which includes the secondary battery 100 in any of the above embodiments.

[0105] In some embodiments, the electronic device 1000 may be a mobile phone, a laptop computer, a tablet computer, a drone, a power tool, an electric toy, a game console, a video recorder, a portable recorder, a radio, or a smart watch, etc., which are not listed one by one here.

[0106] In addition, those skilled in the art should recognize that the above embodiments are only used to illustrate the present application and are not intended to be limiting of the present application. As long as they are within the spirit and scope of the present application, appropriate changes and modifications to the above embodiments are within the scope of the present application.

Claims

1. A secondary battery, characterized in that: include: A first shell, the first shell is a conductor; the first shell includes a first portion and a second portion, the second portion is arranged around the edge of the first portion and encloses the first portion to form a first cavity; A second shell, the second shell is a conductor; the second shell includes a third part and a fourth part, the fourth part is arranged around the edge of the third part, and is enclosed with the third part to form a second cavity; the second shell and the first shell cover each other, the first cavity and the second cavity are connected to form a receiving cavity, and the second shell is insulated and connected to the first shell; An electrode assembly, the electrode assembly is accommodated in the accommodation cavity; the electrode assembly comprises a plurality of first pole pieces and a plurality of second pole pieces, the plurality of first pole pieces are electrically connected to each other, and the plurality of second pole pieces are electrically connected to each other; the first pole piece located at the outermost side of the electrode assembly is a first sub-pole piece; The second pole piece located at the outermost side of the electrode assembly is a second sub-pole piece; the first sub-pole piece and the second sub-pole piece are respectively located at the two outermost sides in the thickness direction of the electrode assembly; The first sub-pole sheet includes a first current collector and a first active material layer, the first current collector has a first surface and a second surface opposite to each other, the first surface is the surface of the first current collector away from the second sub-pole sheet, the first surface is provided with a first empty foil area, the first empty foil area is electrically connected to the first part, and the first active material layer is provided on the second surface; the second sub-pole sheet includes a second current collector and a second active material layer, the second current collector has a third surface and a fourth surface opposite to each other, the third surface is the surface of the second current collector away from the first sub-pole sheet, the third surface is provided with a second empty foil area, the second empty foil area is electrically connected to the third part, and the second active material layer is provided on the fourth surface.

2. The secondary battery according to claim 1, wherein: Along the thickness direction of the secondary battery, the first pole sheet and the second pole sheet are arranged in sequence; the electrode assembly also includes a plurality of first pole tabs, which are electrically connected to the first current collector, and the plurality of first pole tabs are gathered to form a first pole tab group; the electrode assembly also includes a plurality of second pole tabs, which are electrically connected to the second current collector, and the plurality of second pole tabs are gathered to form a second pole tab group.

3. The secondary battery according to claim 2, characterized in that: Along the thickness direction of the secondary battery, multiple first pole sheets and multiple second pole sheets are stacked to form the main body of the electrode assembly, the first pole tab group is stacked between the second part and the main body or between the fourth part and the main body, and the second pole tab group is stacked between the fourth part and the main body or between the second part and the main body.

4. The secondary battery according to claim 2, characterized in that: The secondary battery includes a first adhesive member, which is a conductor; the first adhesive member is bonded between the first surface and the first portion, and / or the first adhesive member is bonded between the third surface and the third portion.

5. The secondary battery according to claim 2, characterized in that: The first portion has a first conductive surface, the first conductive surface is provided with a first convex portion, and the first convex portion is electrically connected to the first surface; and / or, The third portion has a second conductive surface, the second conductive surface is provided with a second convex portion, and the second convex portion is electrically connected to the third surface.

6. The secondary battery according to claim 5, characterized in that: The second shell includes a second adhesive, which is filled between the first surface and the first conductive surface, and is located at a portion of the first conductive surface where the first protrusion is not provided, and / or the second adhesive is filled between the third surface and the second conductive surface, and is located at a portion of the second conductive surface where the second protrusion is not provided.

7. The secondary battery according to any one of claims 1 to 6, characterized in that: The second portion has a first edge, and the fourth portion has a second edge; along the thickness direction of the secondary battery, the first shell and the second shell are connected and covered by aligning the first edge with the second edge.

8. The secondary battery according to any one of claims 1 to 6, characterized in that: The secondary battery also includes an insulating seal, which includes a first sealing portion, a second sealing portion and a third sealing portion, the third sealing portion is connected between the first sealing portion and the second sealing portion, the first sealing portion is wrapped around and bonded to the outer periphery of the second portion, and the second sealing portion is wrapped around and bonded to the outer periphery of the fourth portion; an insulating gap is formed between the first shell and the second shell, and the third sealing portion seals the insulating gap.

9. The secondary battery according to claim 8, characterized in that The peeling force between the insulating seal and the first shell and the second shell is F, satisfying F≥0.5N / mm 2 .

10. The secondary battery according to claim 9, characterized in that F≥1N / mm 2 。 11. The secondary battery according to claim 8, wherein The first sealing portion, the second sealing portion and the third sealing portion are integrally provided.

12. The secondary battery according to claim 8, characterized in that The width of the first sealing portion is W1, which satisfies: 0.1 mm ≤ W1 ≤ 3 mm; And / or, the width of the second sealing portion is W2, satisfying: 0.1 mm≤W2≤3 mm.

13. The secondary battery according to claim 8, characterized in that: 0.3mm≤W1≤1.5mm, and / or, 0.3mm≤W2≤1.5mm.

14. The secondary battery according to claim 8, characterized in that: At least a portion of the third sealing portion is located in the insulating gap.

15. An electronic device, characterized in that: Comprising the secondary battery according to any one of claims 1 to 14.

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