Secondary battery and electronic device

Abstract

The invention provides a secondary battery and electronic equipment. A shell comprises a first wall part, a second wall part, a third wall part, a fourth wall part and a fifth wall part. In the first direction, a first space is formed between the first wall part and the third wall part, the distance between the first wall part and the third wall part is L1, a second space is formed between the second wall part and the third wall part, the distance between the second wall part and the third wall part is L2, and L1 is smaller than L2. The fifth wall portion, the first wall portion, the fourth wall portion, and the second wall portion together form a first step. The first pole piece comprises a first part, a third part and a first connecting part connected between the first part and the third part, the first part is arranged in the first space and extends in the first direction, and the third part is arranged in the second space and extends in the first direction. One end, facing the first wall part, of the first part is connected with a first tab, and the first tab is electrically connected with a first pole on the first wall part. And the space in the shell can be fully utilized, so that the energy density of the secondary battery can be improved.

Description

Technical Field

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

[0002] In many application scenarios, such as portable electronic devices and electric vehicles, there are strict restrictions on the volume of batteries. The internal space of the battery is limited, and the pole, as a necessary structural component, will take up a large space when connected to the pole piece inside the battery, affecting the battery energy density. Summary of the invention

[0003] The present application proposes a secondary battery and an electronic device, aiming to improve the energy density of the secondary battery.

[0004] In the first aspect, the present application proposes a secondary battery, including a shell and an electrode assembly, wherein the electrode assembly is arranged in the shell, and the electrode assembly includes a first pole piece, a separator and a second pole piece arranged in a stacked manner. The shell includes a first wall portion, a second wall portion, a third wall portion, a fourth wall portion and a fifth wall portion. Along the first direction, the first wall portion and the third wall portion are arranged opposite to each other, and there is a first space between the first wall portion and the third wall portion, and the distance from the first wall portion to the third wall portion is L1. Along the first direction, the second wall portion and the third wall portion are arranged opposite to each other, and there is a second space between the second wall portion and the third wall portion, and the second space is connected to the first space, and the distance from the second wall portion to the third wall portion is L2, L1<L2. The fourth wall portion is connected between the first wall portion and the second wall portion, and the fifth wall portion is connected between the first wall portion and the third wall portion, and the fifth wall portion, the first wall portion, the fourth wall portion and the second wall portion together form a first step. The first pole piece includes a first portion, a first connecting portion and a third portion, wherein the first portion is disposed in the first space and extends along the first direction, the third portion is disposed in the second space and extends along the first direction, and the first connecting portion is connected between the first portion and the third portion at one end close to the third wall portion. A first pole lug is connected to one end of the first portion facing the first wall portion, a first pole column is disposed on the first wall portion, and the first pole lug is electrically connected to the first pole column.

[0005] In the above technical solution, in the embodiment of the present application, by folding the first pole piece and placing it in spaces of different lengths, it can better fit the structure of the shell, make full use of the space in the shell, and help improve the energy density of the secondary battery. In addition, the connection between the first part and the third part is arranged close to the third wall, and there is no irregular structure such as the corner of the shell. When the secondary battery is subjected to vibration or external force impact, the contact area between the third wall and the first pole piece is large, which can reduce the damage of the shell to the electrode assembly, such as reducing the damage of the first pole piece and / or the isolation membrane, etc., improve the stability of the electrode assembly in the shell, and effectively reduce the risk of secondary battery performance degradation due to damage to the electrode assembly.

[0006] Furthermore, after the first part and the third part are folded, the first part is directly arranged toward the first wall portion, and the distance between the first part and the first wall portion is relatively short. One end of the first part facing the first wall portion is directly connected to the first pole ear, and is connected to the first pole column through the first pole ear. The polarity of the entire first pole piece can be led out through the first pole column without bending the first pole ear, which can effectively improve the space utilization rate inside the shell and is conducive to improving the energy density of the secondary battery. Furthermore, the first pole column is arranged on the first wall portion, and the distance between the first wall portion and the third wall portion is shorter, which can reduce the overall length of the secondary battery occupied by the first pole column, thereby making full use of the space outside the shell, and further improving the energy density of the secondary battery.

[0007] In some embodiments, 20%≤L1 / L2≤95%. A housing with a specific shape and structure can be designed according to a specific installation space of the electronic device, which is beneficial to improving space utilization and is particularly suitable for small electronic devices.

[0008] In some embodiments, the first connecting portion is an empty foil segment, and the first pole piece is folded at two opposite ends of the first connecting portion so that the first pole piece forms a first part and a third part. The empty foil segment is easier to fold, which can reduce damage to the first pole piece during the folding process.

[0009] In some embodiments, a first insulating layer is provided between the first pole piece and the second pole piece along the thickness direction of the first pole piece, and the first insulating layer covers the first connecting portion. During the folding process, due to the absence of interference from the active material layer, the first connecting portion is softer and easier to bend, which can reduce the resistance during folding, is more conducive to the folding operation of the first pole piece, and can effectively reduce the problems of creases and breakages of the first pole piece due to folding. In addition, the folding portion without the active material layer can be used as a stress buffer area to alleviate the stress concentration phenomenon caused by the volume change of the active material layer, and reduce the risk of cracks or damage to the first pole piece due to excessive stress.

[0010] In some embodiments, along the length direction of the first pole piece, the first connecting portion is connected between the first part and the third part. In the first space, the first part includes a first active material layer disposed facing the second pole piece; in the second space, the third part includes a third active material layer facing the second pole piece. Along the length direction of the first pole piece, the length of the portion where the first insulating layer and the first active material layer overlap in the thickness direction of the first pole piece is D1, 0.2mm≤D1≤2mm, which can facilitate the bonding operation of the first insulating layer to reduce energy density loss and is conducive to fully isolating the first connecting portion from the second pole piece. Similarly, along the length direction of the first pole piece, the length of the portion where the first insulating layer and the third active material layer overlap in the thickness direction of the first pole piece is D3, 0.2mm≤D3≤2mm.

[0011] In some embodiments, the first insulating layer is bonded to the first electrode sheet, which is the positive electrode sheet, so that the negative active material layer has sufficient residual amount to embed the lithium ions released from the positive active material layer, thereby reducing the occurrence of lithium plating and improving the safety performance of the secondary battery.

[0012] In some embodiments, the first insulating layer is a glue layer, the first insulating layer includes a first substrate layer and a first adhesive layer disposed on the surface of the first substrate layer, the first substrate layer includes at least one of polyimide or polyethylene terephthalate, and the first adhesive layer includes at least one of polytetrafluoroethylene, polypropylene, polyethylene or acrylic resin; or, the first insulating layer is an insulating coating, and the first insulating layer includes at least one of aluminum oxide, magnesium oxide, boehmite or zirconium oxide. Each material has good insulation properties, can effectively isolate the first connecting portion from the second pole piece, and reduce the occurrence of short circuit; and has good chemical stability, can adapt to the electrolyte environment, and can remain stable for a long time in the internal environment of the secondary battery; at the same time, it also has a certain mechanical strength, can adapt to the expansion of the pole piece, can adapt to extrusion, stretching or vibration, etc., and is not prone to cracking, deformation and other problems, thereby maintaining the structural integrity and insulation effect of the first insulating layer.

[0013] In some embodiments, the housing further includes a sixth wall portion, which is connected between the second wall portion and the third wall portion. Along the second direction, the distance from the fourth wall portion to the sixth wall portion is L4, and the distance from the fifth wall portion to the sixth wall portion is L5, where L4<L5. The second direction is the direction from the first space to the second space. The housing can be adapted to a specific installation space of the electronic device, which is beneficial to improving the energy density of the secondary battery.

[0014] In some embodiments, along the first direction, the projection of the first pole is located within the projection of the sixth wall portion, so that the first pole does not occupy the entire length of the shell, which can further improve space utilization and thereby improve the energy density of the secondary battery.

[0015] In some embodiments, the housing further includes a seventh wall portion and an eighth wall portion, the seventh wall portion and the eighth wall portion are both connected between the first wall portion and the third wall portion, the seventh wall portion and the eighth wall portion are arranged opposite to each other along the third direction, the first space is located between the seventh wall portion and the eighth wall portion, and the distance from the seventh wall portion to the eighth wall portion is L7. The housing further includes a ninth wall portion and a tenth wall portion, the ninth wall portion and the tenth wall portion are both connected between the second wall portion and the third wall portion, the ninth wall portion and the tenth wall portion are arranged opposite to each other along the third direction, the second space is located between the ninth wall portion and the tenth wall portion, and the distance from the ninth wall portion to the tenth wall portion is L9, L7≤L9. The fourth wall portion extends between the seventh wall portion and the ninth wall portion, and the fourth wall portion is connected to the seventh wall portion and the ninth wall portion; the fifth wall portion, the seventh wall portion, the fourth wall portion and the ninth wall portion together form a second step. The fourth wall portion extends between the eighth wall portion and the tenth wall portion, and the fourth wall portion is connected to the eighth wall portion and the tenth wall portion, and the fifth wall portion, the eighth wall portion, the fourth wall portion and the tenth wall portion together form a third step. Along the third direction, the width of the first part is W1, and the width of the third part is W3, W1≤W3. The first direction, the second direction, and the third direction are mutually perpendicular. According to the distance between each wall portion, the width of the first part and the third part is adjusted to make full use of the internal space of the shell and improve the energy density of the secondary battery. Optionally, 10%≤L7 / L9≤100%, 10%≤W1 / W3≤100%.

[0016] In some embodiments, a first chamfer is provided at the connection between the first wall portion and the seventh wall portion, and a first avoidance position is provided at the first portion, the shape of the first avoidance position corresponds to the first chamfer, and the first avoidance position is arranged facing the first chamfer. The arrangement of the first avoidance position makes the edge of the first pole piece rounded and smooth, which can reduce the risk of piercing the isolation membrane and improve the safety performance of the secondary battery. In addition, the first avoidance position is arranged facing the first chamfer, so that the first pole piece can make full use of the internal space of the secondary battery and improve the energy density of the secondary battery.

[0017] In some embodiments, a second chamfered portion is provided at the connection between the second wall portion and the ninth wall portion, and a second avoidance position is provided at the third portion. The shape of the second avoidance position corresponds to the second chamfered portion, and the second avoidance position is arranged facing the second chamfered portion, which can further enable the first pole piece to make full use of the internal space of the secondary battery and improve the energy density of the secondary battery.

[0018] In some embodiments, the shell includes a accommodating portion and a sixth wall portion, the accommodating portion includes a first wall portion, a second wall portion, a third wall portion, a fourth wall portion and a fifth wall portion that are integrally arranged, and the accommodating portion encloses a first space and a second space. On the side of the second space away from the first space, the accommodating portion is provided with an opening, and the opening is communicated with the second space. The sixth wall portion is connected to the accommodating portion and covers the opening. The electrode assembly can be directly placed in the accommodating portion through the opening. The sixth wall portion is connected to the accommodating portion and covers the opening, thereby making the shell sealed.

[0019] In some embodiments, the secondary battery includes a plurality of first pole pieces and a plurality of first pole ears, and the first portion of each first pole piece is connected to one of the plurality of first pole ears. The secondary battery also includes a first adapter, and the first pole ears of the plurality of first pole pieces are all connected to the first adapter, and the first adapter is connected to the first pole column. The current of the plurality of first pole pieces is gathered by the first adapter, so that the charge and discharge rate performance of the secondary battery can be improved. In addition, the first pole column is arranged on the first wall portion, and the distance between each first pole ear and the first pole column is short. The first adapter does not need to be bent multiple times, which is conducive to making full use of the space inside the shell, thereby improving the energy density of the secondary battery.

[0020] In some embodiments, the second pole piece includes a second portion, a second connecting portion and a fourth portion, the second portion is arranged in the first space and extends along the first direction, the fourth portion is arranged in the second space and extends along the first direction, and the second connecting portion is connected between the second portion and the fourth portion at one end close to the third wall portion. Along the second direction, the first portion and the second portion are stacked, and the third portion and the fourth portion are stacked. The second direction is the direction from the first space to the second space. The second portion is connected to a second pole ear at one end facing the first wall portion, the first wall portion is provided with a second pole column, and the second pole ear is electrically connected to the second pole column.

[0021] By folding the second pole piece and placing them in spaces of different lengths, the second pole piece can better fit the structure of the shell, making full use of the space in the shell, which is beneficial to improving the energy density of the secondary battery. After the second part and the fourth part are folded, the second part is directly arranged toward the first wall portion, and the distance between the second part and the first wall portion is short. The end of the second part facing the first wall portion is directly connected to the second pole ear, and is connected to the second pole column through the second pole ear. The polarity of the entire second pole piece can be led out through the second pole column without bending the second pole ear, which can effectively improve the space utilization rate inside the shell, which is beneficial to improving the energy density of the secondary battery.

[0022] In some embodiments, the shell is a metal shell, and the metal shell includes at least one of aluminum, steel, stainless steel, nickel or copper. The second pole piece includes a second part, a second connecting portion and a fourth part, the second part is arranged in the first space and extends along the first direction, the fourth part is arranged in the second space and extends along the first direction, and the second connecting portion is connected between the second part and the fourth part at one end close to the third wall. Along the second direction, the first part and the second part are stacked, and the third part and the fourth part are stacked; wherein the second direction is the direction from the first space to the second space. The second part is connected to a second pole ear at one end facing the first wall, and the second pole ear is electrically connected to the first wall. The shell can replace the pole to lead out one polarity of the electrode assembly, which can reduce the installation operation of the pole, and can reduce the space occupied by the pole, thereby improving the energy density of the secondary battery.

[0023] In some embodiments, a second connecting portion is provided between the second part and the fourth part, and the second pole piece is folded along the second connecting portion so that the second pole piece forms the second part and the fourth part, which can facilitate the folding of the second pole piece and reduce the risk of cracks, damage, etc. in the second pole piece.

[0024] In a second aspect, the present application further proposes an electronic device, comprising a secondary battery as in any embodiment of the first aspect above.

[0025] Additional aspects and advantages of the embodiments of the present application will be described, shown, or explained in part in the subsequent description through implementation of the embodiments of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] One or more embodiments are exemplarily described by the figures in the corresponding drawings, and these exemplary descriptions are not intended to limit the embodiments. Elements with the same reference numerals in the drawings represent similar elements.

[0027] Figure 1 A schematic diagram of the internal structure of a secondary battery in some embodiments of the present application;

[0028] Figure 2 This is a schematic diagram of the structure of the housing of some embodiments of the present application;

[0029] Figure 3 A schematic diagram of stacking a first pole piece, an isolation film, and a second pole piece in some embodiments of the present application;

[0030] Figure 4 Schematic diagram of the structure of a secondary battery according to some embodiments of the present application (viewed along the second direction Y);

[0031] Figure 5 A schematic diagram of the structure of the first insulating layer in some embodiments of the present application;

[0032] Figure 6 A schematic diagram of the structure of a secondary battery in some embodiments of the present application;

[0033] Figure 7 This is a schematic structural diagram of a first pole piece in some embodiments of the present application;

[0034] Figure 8 A schematic diagram of the structure of a secondary battery in some embodiments of the present application;

[0035] Fig. 9 This is a schematic structural diagram of a first pole piece in some embodiments of the present application;

[0036] Fig.10 This is a schematic diagram of the structure of the housing of some embodiments of the present application;

[0037] Fig.11 This is a schematic diagram of the structure of the housing of some embodiments of the present application;

[0038] Fig.12 Schematic diagram of the internal structure of a secondary battery according to some embodiments of the present application.

[0039] Description of reference numerals:

[0040] 100. Secondary battery;

[0041] 10. Shell; 10a. First space; 10b. Second space; 10c. Accommodation chamber; 10a1. First accommodation portion; 10b1. Second accommodation portion; 10d. First step; 10e1. Second step; 10f1. Third step; 10c1. Accommodation portion; 10c2. Opening; 10d1. Third accommodation portion; 11. First wall portion; 12. Second wall portion; 13. Third wall portion; 131. First sub-wall portion; 132. Second sub-wall portion; 14. Fourth wall portion; 15. Fifth wall portion; 16. Sixth wall portion; 17. Seventh wall portion; 18. Eighth wall portion; 19. Ninth wall portion; 110. Tenth wall portion; 111. First chamfered portion; 112. Second chamfered portion;

[0042] 20. electrode assembly; 21. first pole piece; 211. first part; 2111. first active material layer; 212. first connecting portion; 213. third part; 2131. third active material layer; 2131. first avoidance position; 215. fifth part; 22. second pole piece; 221. second part; 2211. second active material layer; 222. second connecting portion; 223. fourth part; 2231. fourth active material layer; 2132. second avoidance position; 226. sixth part; 23. isolation membrane;

[0043] 30. first pole; 40. second pole;

[0044] 50. first insulating layer; 51. first base material layer; 52. first adhesive layer;

[0045] 60. first pole ear; 70. second pole ear; 80. first adapter;

[0046] X, first direction; Y, second direction; Z, third direction;

[0047] M, fourth direction; N, fifth direction; H, sixth direction. DETAILED DESCRIPTION

[0048] In order to make the purpose, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly 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, not all of the embodiments.

[0049] Reference to "embodiment" in this application means that a particular feature, structure, or characteristic described in conjunction with the embodiment may be included in at least one embodiment of the present application. The appearance of the phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments.

[0050] In the description of the embodiments of the present application, the technical terms "first", "second", etc. 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. In the description of the embodiments of the present application, the meaning of "multiple" and "several" is more than two, unless otherwise clearly and specifically defined.

[0051] In the description of the embodiments of the present application, the term "and / or" is only a description of the association relationship of the associated objects, indicating that there may be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0052] In the first aspect, the present application proposes a secondary battery 100, please refer to Figure 1 The secondary battery 100 includes a housing 10, an electrode assembly 20 and a first pole 30. The electrode assembly 20 is disposed in the housing 10, one end of the first pole 30 is connected to the electrode assembly 20, and the other end is exposed from the housing 10, and the first pole 30 is used to lead out one polarity of the secondary battery 100.

[0053] For the above-mentioned housing 10, please refer to Figure 1 and Figure 2The shell 10 encloses a receiving cavity 10c, which can accommodate the electrode assembly 20 and the electrolyte (not shown in the figure). The electrolyte infiltrates the electrode assembly 20 in the receiving cavity 10c, thereby generating an electrochemical reaction. In an embodiment of the present application, the shell 10 can be formed by punching a metal sheet, and the thickness of the metal sheet can be set to 0.1mm to 0.4mm, so that the shell 10 has a high punching strength. Among them, the metal sheet can be made of aluminum, steel, stainless steel, nickel or copper, so that the shell 10 can lead to a certain polarity of the secondary battery 100, and the above-mentioned first pole 30 can lead to another polarity.

[0054] For the electrode assembly 20, please refer to Figures 1 to 3 The electrode assembly 20 is arranged in the accommodating cavity 10c of the shell 10. The shape of the electrode assembly 20 can be set to match the shell 10 to make full use of the space of the accommodating cavity 10c of the shell 10 and improve the energy density of the secondary battery 100. The electrode assembly 20 includes a first pole piece 21, a second pole piece 22 and a separator 23. The polarity of the first pole piece 21 and the second pole piece 22 are opposite. For example, the first pole piece 21 is a positive pole piece, and the second pole piece 22 is a negative pole piece, or the first pole piece 21 is a negative pole piece, and the second pole piece 22 is a positive pole piece. A plurality of first pole pieces 21 and a plurality of second pole pieces 22 are alternately stacked, and a separator 23 is arranged between adjacent first pole pieces 21 and second pole pieces 22 to form a stacked electrode assembly 20.

[0055] The second electrode piece 22 of the electrode assembly 20 can be directly electrically connected to the housing 10, so that the housing 10 leads to the negative electrode, and the first electrode piece 21 of the electrode assembly 20 can be electrically connected to the first electrode column 30, so that the first electrode column 30 leads to the positive electrode. In some other embodiments, the housing 10 can also lead to the positive electrode, and the first electrode column 30 can lead to the negative electrode. Alternatively, a second electrode column 40 (see Figure 4 ), the second pole piece 22 is connected to the second pole 40, so that the first pole 30 and the second pole 40 lead out positive and negative poles.

[0056] For the first pole 30, please refer to Figure 1 The first pole 30 is disposed in the housing 10, a portion of the first pole 30 is electrically connected to the electrode assembly 20 in the accommodating cavity 10c, and the other portion is exposed from the housing 10. In the embodiment of the present application, the first pole 30 and the housing 10 have opposite polarities, and an insulating adhesive layer (not shown in the figure) may be disposed between the first pole 30 and the housing 10 to reduce the occurrence of short circuits, and the insulating adhesive layer may be bonded between the first pole 30 and the housing 10, which may connect the first pole 30 and the housing 10 on the one hand, and seal the installation gap between the first pole 30 and the housing 10 on the other hand, thereby improving the sealing performance of the secondary battery 100.

[0057] The housing 10 may be in a square, trapezoidal, cylindrical or irregular shape. In the embodiment of the present application, the housing 10 may be in an irregular shape to accommodate the irregular installation space of the electronic device. Figure 2 The housing 10 includes a first wall portion 11, a second wall portion 12, a third wall portion 13, a fourth wall portion 14 and a fifth wall portion 15. Along the first direction X, the first wall portion 11 and the third wall portion 13 are arranged opposite to each other, and a first space 10a is provided between the first wall portion 11 and the third wall portion 13, and a distance from the first wall portion 11 to the third wall portion 13 is L1. Along the first direction X, the second wall portion 12 and the third wall portion 13 are arranged opposite to each other, and a second space 10b is provided between the second wall portion 12 and the third wall portion 13, and the second space 10b is communicated with the first space 10a, so that the first space 10a and the second space 10b together form a receiving chamber 10c of the housing 10. Along the first direction X, the distance from the second wall portion 12 to the third wall portion 13 is L2, and L1<L2. The fourth wall portion 14 is connected between the first wall portion 11 and the second wall portion 12 , the fifth wall portion 15 is connected between the first wall portion 11 and the third wall portion 13 , and the fifth wall portion 15 , the first wall portion 11 , the fourth wall portion 14 and the second wall portion 12 together form a first step 10 d .

[0058] In this way, the housing 10 can be formed into two parts of different lengths, namely the first accommodating part 10a1 and the second accommodating part 10b1. The first accommodating part 10a1 encloses the first space 10a, and the second accommodating part 10b1 encloses the second space 10b. One side of the first accommodating part 10a1 and the second accommodating part 10b1 is the third wall part 13, that is, one side of the two first accommodating parts 10a1 is flush with one side of the second accommodating part 10b1, and the other side forms a first step 10d. The first step 10d can adapt to the space of the electronic device and can avoid the components of the electronic device.

[0059] Please refer to Figures 1 to 3The first pole piece 21 includes a first portion 211, a first connection portion 212 and a third portion 213, wherein the first connection portion 212 is connected between the first portion 211 and the third portion 213. The first portion 211 is disposed in the first space 10a and extends along the first direction X, and the third portion 213 is disposed in the second space 10b and extends along the first direction X. The first portion 211 is connected to the third portion 213 at one end close to the third wall portion 13. For example, the first pole piece 21 is folded along the first connection portion 212 so that the first portion 211 and the third portion 213 are stacked, the folding position is the first connection portion 212, the first connection portion 212 is close to the third wall portion 13, the first portion 211 is placed in the first space 10a, and the third portion 213 is placed in the second space 10b, so that the first portion 211 can be easily extended along the first direction X, and the third portion 213 can be easily extended along the first direction X. One end of the first portion 211 away from the third wall portion 13 is directly disposed toward the first wall portion 11 , and one end of the third portion 213 away from the third wall portion 13 is directly disposed toward the second wall portion 12 .

[0060] In the embodiment of the present application, by folding the first pole piece 21 and placing it in spaces of different lengths, the structure of the housing 10 can be better matched, the space in the housing 10 can be fully utilized, and the energy density of the secondary battery 100 can be improved. In addition, the connection between the first part 211 and the third part 213 is a bending part, that is, the first connection part 212 is a bending part, and the bending part is affected by stress concentration and is more likely to be damaged. The connection between the first part 211 and the third part 213 is arranged close to the third wall part 13, and there is no irregular structure such as the corner of the housing 10. When the secondary battery 100 is subjected to vibration or external force impact, the contact area between the third wall part 13 and the first pole piece 21 is large, which can reduce the damage of the housing 10 to the electrode assembly 20, such as reducing the damage of the first pole piece 21 and / or the isolation film 23, etc., improve the stability of the electrode assembly 20 in the housing 10, and effectively reduce the risk of performance degradation of the secondary battery 100 due to damage to the electrode assembly 20.

[0061] Please refer to Figures 1 to 3, the first portion 211 is connected to the first pole ear 60 at one end facing the first wall portion 11, and the first pole ear 60 can be integrally arranged with the current collector (not shown in the figure) of the first pole piece 21, or can be separately arranged. The first pole 30 is arranged on the first wall portion 11, and the first pole ear 60 is connected to the first pole 30, and the connection method includes but is not limited to welding, clamping, screwing or conductive adhesive bonding. After the first portion 211 and the third portion 213 are folded, the first portion 211 is directly arranged toward the first wall portion 11, and the distance between the first portion 211 and the first wall portion 11 is short. The first portion 211 is directly connected to the first pole ear 60 at one end facing the first wall portion 11, and is electrically connected to the first pole 30 through the first pole ear 60. The polarity of the entire first pole piece 21 (including the first portion 211 and the third portion 213) can be led out through the first pole 30 without bending the first pole ear 60, which can effectively improve the space utilization inside the housing 10, which is conducive to improving the energy density of the secondary battery 100. Furthermore, the first pole 30 is disposed on the first wall portion 11 , and the distance between the first wall portion 11 and the third wall portion 13 is shorter, which can reduce the overall length of the secondary battery 100 occupied by the first pole 30 , thereby making full use of the space outside the shell 10 , and further improving the energy density of the secondary battery 100 .

[0062] In some embodiments, 20%≤L1 / L2≤95%. The housing 10 with a specific shape and structure can be designed according to the specific installation space of the electronic device, which is beneficial to improving the utilization of the space and is particularly suitable for small electronic devices.

[0063] As for the second pole piece 22, the second pole piece 22 can be configured similarly to the first pole piece 21. Figures 1 to 3 The second pole piece 22 includes a second portion 221, a second connecting portion 222 and a fourth portion 223. The second portion 221 is disposed in the first space 10a and extends along the first direction X. The first portion 211 and the second portion 221 are stacked along the second direction Y. The second direction Y is the direction from the first space 10a to the second space 10b. The fourth portion 223 is disposed in the second space 10b and extends along the first direction X. The third portion 213 and the fourth portion 223 are stacked along the second direction Y. The second portion 221 is connected to the fourth portion 223 at one end close to the third wall portion 13.

[0064] For example, the second pole piece 22 is folded so that the second part 221 and the fourth part 223 are stacked, the folding position is the second connecting portion 222, the second connecting portion 222 is close to the third wall portion 13, the second part 221 is placed in the first space 10a, and the fourth part 223 is placed in the second space 10b, so that the second part 221 can be easily extended along the first direction X, and the fourth part 223 can be easily extended along the first direction X. The end of the second part 221 away from the third wall portion 13 is directly arranged toward the first wall portion 11, and the end of the fourth part 223 away from the third wall portion 13 is directly arranged toward the second wall portion 12. By folding the second pole piece 22 and placing them in spaces of different lengths, the second pole piece 22 can better fit the structure of the housing 10, make full use of the space in the housing 10, and help improve the energy density of the secondary battery 100.

[0065] Please refer to further Figure 4 The secondary battery 100 further includes a second pole 40, through which the polarity of the second pole piece 22 can be derived. The second pole 40 is similar to the first pole 30, and the second pole 40 is disposed on the first wall portion 11, and a second pole lug 70 is connected to one end of the second portion 221 facing the first wall portion 11, and the second pole lug 70 is connected to the second pole 40, so that the second pole 40 can lead the polarity of the second pole piece 22.

[0066] After the second part 221 and the fourth part 223 are folded, the second part 221 is directly arranged toward the first wall portion 11, and the distance between the second part 221 and the first wall portion 11 is relatively short. One end of the second part 221 toward the first wall portion 11 is directly connected to the second pole ear 70, and is connected to the second pole column 40 through the second pole ear 70. The polarity of the entire second pole sheet 22 (including the second part 221 and the fourth part 223) can be led out through the second pole column 40 without bending the second pole ear 70, which can effectively improve the space utilization inside the shell 10, and is beneficial to improving the energy density of the secondary battery 100.

[0067] In some other embodiments, the housing 10 is a metal housing 10, and the metal housing 10 includes at least one of steel, aluminum, copper, nickel, nickel alloy or aluminum alloy, and the second pole ear 70 can also be directly connected to the first wall portion 11, that is, the housing 10 leads out a polarity. The housing 10 can replace the second pole 40 to lead out a polarity of the electrode assembly 20, which can reduce the installation operation of the second pole 40 and reduce the space occupied by the second pole 40, thereby improving the energy density of the secondary battery 100.

[0068] In some embodiments, please refer to Figures 1 to 3, along the second direction Y, the first part 211 and the second part 221 are stacked in the first space 10a, and the first part 211 includes a first active material layer 2111 facing the second electrode sheet 22, for example, the first active material layer 2111 is arranged facing the second part 221 of the second electrode sheet 22. The second part 221 includes a second active material layer 2211 facing the first part 211, and the first active material layer 2111 and the second active material layer 2211 can perform ion exchange, thereby generating an electrochemical reaction.

[0069] Similarly, along the second direction Y, the third portion 213 and the fourth portion 223 are stacked in the second space 10b, and the third portion 213 includes a third active material layer 2131 facing the second electrode sheet 22, for example, the third active material layer 2131 is arranged facing the fourth portion 223 of the second electrode sheet 22. The fourth portion 223 includes a fourth active material layer 2231 facing the third portion 213, and the third active material layer 2131 and the fourth active material layer 2231 can perform ion exchange, thereby generating an electrochemical reaction.

[0070] For the folding of the first pole piece 21, in some embodiments, please refer to Figure 3 , the first connecting portion 212 is an empty foil segment, that is, the first connecting portion 212 is not provided with an active material layer, and the first connecting portion 212 is provided between the first portion 211 and the third portion 213. The first pole piece 21 is folded at the opposite ends of the first connecting portion 212, so that the first pole piece 21 forms the first portion 211 and the third portion 213. During the folding process, due to the absence of interference from the active material layer, the first connecting portion 212 is softer and easier to bend, which can reduce the resistance during folding, and is more conducive to the folding operation of the first pole piece 21, which can effectively reduce the problems of creases and breakages of the first pole piece 21 due to folding. In addition, during the charging and discharging process of the secondary battery 100, the first pole piece 21 will undergo a volume change, thereby generating stress. The folded portion without the active material layer can be used as a stress buffer area to alleviate the stress concentration phenomenon caused by the volume change of the active material layer, and reduce the risk of cracks or damage to the first pole piece 21 due to excessive stress.

[0071] For the folding of the second pole piece 22, the second pole piece 22 can be arranged similarly to the first pole piece 21, please refer to Figure 3 A second connecting portion 222 is provided between the second portion 221 and the fourth portion 223. The second connecting portion 222 is a hollow foil segment, that is, the second connecting portion 222 is provided with an active material layer. The second pole piece 22 is folded at opposite ends of the second connecting portion 222, so that the second pole piece 22 forms the second portion 221 and the fourth portion 223. The folding of the second pole piece 22 is facilitated, and the risk of cracks and damage to the second pole piece 22 is reduced.

[0072] In some embodiments, please refer to Figure 3 , along the thickness direction of the first pole piece 21 (the sixth direction H), a first insulating layer 50 is arranged between the first pole piece 21 and the second pole piece 22, and the first insulating layer 50 covers the first connection part 212 and / or the second connection part 222. For example, the first connection part 212 and the second connection part 222 are arranged opposite to each other, and the first insulating layer 50 is arranged between the first connection part 212 and the second connection part 222 to isolate the first connection part 212 and the second connection part 222. It can reduce the exposure of the empty foil and reduce the short circuit caused by the direct contact between the first pole piece 21 and the second pole piece 22. In addition, the first insulating layer 50 can also be bonded to the first connection part 212 or the second connection part 222, which can disperse the stress of the first connection part 212 or the second connection part 222 and reduce the damage of the first connection part 212 or the second connection part 222 caused by bending.

[0073] The first insulating layer 50 may be bonded to the first pole piece 21, or to the second pole piece 22, or to the isolation film 23 between the first pole piece 21 and the second pole piece 22. Taking the bonding of the first insulating layer 50 to the first pole piece 21 as an example, in order to facilitate the bonding operation of the first insulating layer 50 and the first pole piece 21, the first insulating layer 50 may bond part of the first active material layer 2111 and the third active material layer 2131. For example, along the length direction of the first pole piece 21 (the fourth direction M), the length of the portion where the first insulating layer 50 and the first active material layer 2111 overlap in the thickness direction of the first pole piece 21 (the sixth direction H) is D1, which can facilitate the bonding operation of the first insulating layer 50, reduce the energy density loss, and facilitate the full isolation of the first connecting portion 212 and the second pole piece 22.

[0074] Optionally, along the length direction of the first pole piece 21 (the fourth direction M), the length of the overlapping portion of the first insulating layer 50 and the third active material layer 2131 in the thickness direction of the first pole piece 21 (the sixth direction H) is D3, 0.2mm≤D3≤2mm, which can facilitate the bonding operation of the first insulating layer 50 to reduce energy density loss and is beneficial to fully isolate the first connecting portion 212 from the second pole piece 22.

[0075] In some embodiments, the first insulating layer 50 is bonded to the first electrode sheet 21, and the first electrode sheet 21 is a positive electrode sheet. By covering a portion of the positive electrode active material layer (including the first active material layer 2111 and the third active material layer 2131) with the first insulating layer 50, the negative electrode active material layer (including the second active material layer 2211 and the fourth active material layer 2231) can have sufficient surplus to embed lithium ions released from the positive electrode active material layer, thereby reducing the occurrence of lithium plating and improving the safety performance of the secondary battery 100.

[0076] As for the material of the first insulating layer 50, the first insulating layer 50 includes at least one of polyethylene terephthalate, polyetheretherketone, polyimide, polyetherimide, polytetrafluoroethylene, polypropylene, polyethylene, acrylic resin, aluminum oxide, magnesium oxide, boehmite or zirconium oxide. Each material has good insulation performance, which can effectively isolate the first connecting portion 212 from the second pole piece 22 to reduce the occurrence of short circuit; and has good chemical stability, can adapt to the electrolyte environment, and can remain stable for a long time in the internal environment of the secondary battery 100; at the same time, it also has a certain mechanical strength, can adapt to the expansion of the pole piece, can adapt to such as extrusion, stretching or vibration, etc., and is not prone to cracking, deformation and other problems, thereby maintaining the structural integrity and insulation effect of the first insulating layer 50.

[0077] In some embodiments, the first insulating layer 50 is a glue layer, and the first insulating layer 50 includes a first substrate layer 51 and a first adhesive layer 52, and the first adhesive layer 52 is disposed on the surface of the first substrate layer 51. The first substrate layer 51 can be made of materials such as polyimide or polyethylene terephthalate, and the first adhesive layer 52 can be made of polytetrafluoroethylene, polypropylene, polyethylene or acrylic resin or the like. When the first insulating layer 50 is a glue layer, it can be directly bonded to the first active material layer 2111 and the third active material layer 2131. In some other embodiments, an insulating coating such as aluminum oxide, magnesium oxide, zirconium oxide or boehmite can also be used, which can be directly coated on the first connecting portion 212, so that the first connecting portion 212 is insulated from the second pole piece 22.

[0078] In some embodiments, please refer to Figure 1 and Figure 2 , the housing 10 further includes a fourth wall portion 14, a fifth wall portion 15 and a sixth wall portion 16. The fourth wall portion 14 is connected between the first wall portion 11 and the second wall portion 12, and the fourth wall portion 14 and the first wall portion 11 enclose a first step 10d, the fifth wall portion 15 is connected between the first wall portion 11 and the third wall portion 13, and the sixth wall portion 16 is connected between the second wall portion 12 and the third wall portion 13. Along the second direction Y, the distance from the fourth wall portion 14 to the sixth wall portion 16 is L4, and the distance from the fifth wall portion 15 to the sixth wall portion 16 is L5, L4<L5, for example, L4 / L5≤50%. . The housing 10 can be adapted to the specific installation space of the electronic device, which is conducive to improving the energy density of the secondary battery 100.

[0079] Please refer to further Figure 4, along the first direction X, the first step 10d forms a first notch, the first pole 30 is exposed at the first notch, and the projection of the first pole 30 is located within the projection of the sixth wall portion 16. The first notch was originally an empty space formed by the first accommodating portion 10a1 and the second accommodating portion 10b1 due to the different lengths. The first pole 30 is arranged here to effectively utilize this space, reduce space waste, make the secondary battery 100 structure more compact, and help improve the energy density of the secondary battery 100. In addition, the projection of the first pole 30 is located within the projection of the sixth wall portion 16, so that the first pole 30 does not occupy the entire length of the housing 10, which can further improve the space utilization rate, and thus improve the energy density of the secondary battery 100. The second pole 40 can also be arranged similarly.

[0080] In some embodiments, please refer to Figure 2 and Figure 6 The housing 10 further includes a seventh wall portion 17 and an eighth wall portion 18. The seventh wall portion 17 and the eighth wall portion 18 are both connected between the first wall portion 11 and the third wall portion 13. Along the third direction Z, the seventh wall portion 17 and the eighth wall portion 18 are arranged opposite to each other. The first space 10a is located between the seventh wall portion 17 and the eighth wall portion 18. The distance from the seventh wall portion 17 to the eighth wall portion 18 is L7. The housing 10 further includes a ninth wall portion 19 and a tenth wall portion 110. The ninth wall portion 19 and the tenth wall portion 110 are both connected between the second wall portion 12 and the third wall portion 13. Along the third direction Z, the ninth wall portion 19 and the tenth wall portion 110 are arranged opposite to each other. The second space 10b is located between the ninth wall portion 19 and the tenth wall portion 110. The distance from the ninth wall portion 19 to the tenth wall portion 110 is L9. L7≤L9. The fourth wall portion 14 extends between the seventh wall portion 17 and the ninth wall portion 19, and the fourth wall portion 14 is connected to the seventh wall portion 17 and the ninth wall portion 19; the fifth wall portion 15, the seventh wall portion 17, the fourth wall portion 14 and the ninth wall portion 19 together form a second step 10e1. The fourth wall portion 14 extends between the eighth wall portion 18 and the tenth wall portion 110, and the fourth wall portion 14 is connected to the eighth wall portion 18 and the tenth wall portion 110, and the fifth wall portion 15, the eighth wall portion 18, the fourth wall portion 14 and the tenth wall portion 110 together form a third step 10f1. The first direction X, the second direction Y and the third direction Z are perpendicular to each other.

[0081] In the embodiments of this application, please refer to Figure 7 Along the width direction of the first pole piece (fifth direction N), the width of the first portion 211 is W1, the width of the third portion 213 is W3, W1≤W3. Among them, 10%≤L7 / L9≤100%, 10%≤W1 / W3≤100%.

[0082] For example, when the distance between the seventh wall portion 17 and the eighth wall portion 18 is smaller than the distance between the ninth wall portion 19 and the tenth wall portion 110, the width of the first portion 211 can be set to be smaller than the width of the third portion 213. The width of the first portion 211 is smaller, which can adapt to the distance between the seventh wall portion 17 and the eighth wall portion 18, and the width of the third portion 213 is larger, which can adapt to the distance between the ninth wall portion 19 and the tenth wall portion 110. According to the distance between each wall portion, the width of the first portion 211 and the third portion 213 can be adjusted to make full use of the internal space of the housing 10 and improve the energy density of the secondary battery 100. This design helps to optimize the overall shape and size of the secondary battery 100, so that it is more in line with the requirements of different application scenarios, and is particularly suitable for devices with high space requirements, such as portable electronic devices such as Bluetooth headsets and radios. By reasonably designing the width of the housing 10 and the width of each corresponding pole piece, it is convenient to make the secondary battery 100 better adapt to the internal space of the electronic device, and realize the miniaturization and lightweight design of the device.

[0083] In some embodiments, please refer to Figure 8 and Fig. 9 The first chamfered portion 111 is provided at the connection between the first wall portion 11 and the seventh wall portion 17. The first chamfered portion 111 can disperse the external force to a certain extent, reducing the risk of the shell 10 being broken due to the concentration of external force. The first portion 211 is provided with a first avoidance position 2131. The shape of the first avoidance position 2131 corresponds to the first chamfered portion 111. The setting of the first avoidance position 2131 makes the edge of the first pole piece 21 rounded and smooth, which can reduce the risk of piercing the isolation membrane 23 and improve the safety performance of the secondary battery 100. In addition, the first avoidance position 2131 is arranged facing the first chamfered portion 111, so that the first pole piece 21 can make full use of the internal space of the secondary battery 100 and improve the energy density of the secondary battery 100.

[0084] Similarly, a second chamfered portion 112 is provided at the connection between the second wall portion 12 and the ninth wall portion 19, and a second avoidance position 2132 is provided at the third portion 213. The shape of the second avoidance position 2132 corresponds to the second chamfered portion 112, and the second avoidance position 2132 is arranged facing the second chamfered portion 112, which can further enable the first pole piece 21 to make full use of the internal space of the secondary battery 100 and improve the energy density of the secondary battery 100.

[0085] In some embodiments, the secondary battery 100 includes a plurality of first pole pieces 21 and a plurality of first pole tabs 60, and the first portion 211 of each first pole piece 21 is connected to one of the plurality of first pole tabs 60. Figure 1The secondary battery 100 further includes a first adapter 80, and the first pole tabs 60 of the plurality of first pole pieces 21 are all connected to the first adapter 80, and the first adapter 80 is connected to the first pole column 30. The current of the plurality of first pole pieces 21 is gathered by the first adapter 80, so that the charge and discharge rate performance of the secondary battery 100 can be improved. In addition, the first pole column 30 is arranged on the first wall portion 11, and the distance between each first pole tab 60 and the first pole column 30 is short. The first adapter 80 does not need to be bent multiple times, which is conducive to making full use of the space inside the housing 10, thereby improving the energy density of the secondary battery 100.

[0086] Among them, the second pole piece 22 can be configured similarly to the first pole piece 21 , and will not be described one by one in this application.

[0087] Regarding the installation of the electrode assembly 20 in the housing 10, in some embodiments, please refer to Fig.10 The housing 10 includes a housing portion 10c1 and a sixth wall portion 16. For example, before installation, the housing portion 10c1 and the sixth wall portion 16 are separately provided. The housing portion 10c1 includes a first wall portion 11, a second wall portion 12, a third wall portion 13, a fourth wall portion 14, and a fifth wall portion 15 that are integrally provided. The housing portion 10c1 encloses a first space 10a and a second space 10b. On the side of the second space 10b away from the first space 10a, the housing portion 10c1 is provided with an opening 10c2, and the opening 10c2 communicates with the second space 10b. The sixth wall portion 16 is connected to the housing portion 10c1 and covers the opening 10c2. In some other embodiments, the housing portion 10c1 may further include a seventh wall portion 17, an eighth wall portion 18, a ninth wall portion 19, and a tenth wall portion 110.

[0088] In some other embodiments, please refer to Fig.11The housing 10 includes a first accommodating portion 10a1 and a second accommodating portion 10b1. For example, before installation, the first accommodating portion 10a1 and the second accommodating portion 10b1 are separately arranged. The first accommodating portion 10a1 is connected to the second accommodating portion 10b1. The third wall portion 13 includes a first sub-wall portion 131 and a second sub-wall portion 132. The first accommodating portion 10c110a1 includes an integrally arranged first wall portion 11, a first sub-wall portion 131, a fifth wall portion 15, a seventh wall portion 17 and an eighth wall portion 18. The first accommodating portion 10c110a1 encloses a first space 10a. The second accommodating portion 10c110b1 includes an integrally arranged second wall portion 12, a second sub-wall portion 132, a fourth wall portion 14, a ninth wall portion 19, a tenth wall portion 110 and a sixth wall portion 16. The second accommodating portion 10b1 encloses a second space 10b. The electrode assembly 20 can be placed in the first space 10a or the second space 10b first, and then the first accommodating portion 10a1 and the second accommodating portion 10b1 are connected, and the connection method includes but is not limited to welding or bonding, etc. After the first sub-wall portion 131 and the second sub-wall portion 132 are connected, the first sub-wall portion 131 and the second sub-wall portion 132 can be arranged flush, and then the first sub-wall portion 131 and the second sub-wall portion 132 together form the third wall portion 13, and the housing 10 can be sealed. Among them, a flange portion (not shown in the figure) can be provided at the connection between the first accommodating portion 10a1 and the second accommodating portion 10b1, which can facilitate the connection between the first accommodating portion 10a1 and the second accommodating portion 10b1.

[0089] In some embodiments, please refer to Fig.12 , the housing 10 may further include a third accommodating portion 10d1, a fifth portion 215 may be provided corresponding to the first pole piece 21, and a sixth portion 226 may be provided corresponding to the second pole piece 22, thereby making full use of the internal space of the housing 10 and improving the energy density of the secondary battery 100. In some other embodiments, the housing 10 may further include a fourth accommodating portion (not shown in the figure), a fifth accommodating portion (not shown in the figure), etc., the first pole piece 21 may be provided with a seventh portion (not shown in the figure) and a ninth portion (not shown in the figure), etc., and the second pole piece 22 may be provided with an eighth portion (not shown in the figure) and a tenth portion (not shown in the figure), etc.

[0090] In the second aspect, the present application also proposes an electronic device, including a secondary battery 100 as in any embodiment of the first aspect described above. The electronic device of the embodiment of the present application is not particularly limited, and it can be any electronic device known in the prior art. For example, electronic devices include but are not limited to Bluetooth headsets, mobile phones, tablets, laptops, electric toys, electric tools, battery cars, electric cars, ships, spacecraft, and the like. Among them, electric toys can include fixed or mobile electric toys, for example, game consoles, electric car toys, electric ship toys, electric airplane toys, and the like, and spacecraft can include airplanes, rockets, space shuttles, and spacecrafts, and the like.

[0091] Example 1

[0092] <Preparation of positive electrode sheet>

[0093] The positive electrode active material is lithium cobalt oxide, the positive electrode conductive agent is acetylene black, and the positive electrode binder is polyvinylidene fluoride (PVDF, with a weight average molecular weight of 5×10 5 ) are mixed in a mass ratio of 96:2:2, N-methylpyrrolidone (NMP) is added as a solvent, and a positive electrode slurry with a solid content of 75wt% is prepared, and the mixture is stirred evenly under a vacuum mixer. An aluminum foil with a thickness of 10μm, a length of 51mm, and a width of 16.7mm is used as the positive electrode collector. The positive electrode slurry is evenly coated on one surface of the positive electrode collector aluminum foil, and a first empty foil area not coated with the positive electrode slurry is reserved in the middle part of the length direction of the positive electrode collector. Dry at 110°C to obtain a positive electrode sheet coated with a single-sided positive electrode active material layer. After that, the above steps are repeated on the other surface of the aluminum foil to obtain a positive electrode sheet coated with a double-sided positive electrode active material layer. The single-sided coating weight of the positive electrode sheet is 14.6mg / cm 2 .

[0094] <Preparation of negative electrode sheet>

[0095] The negative electrode active material graphite powder, conductive agent conductive carbon black (Super P), and binder styrene-butadiene rubber (SBR) are mixed in a weight ratio of 95:3:2, and then deionized water is added as a solvent to prepare a negative electrode slurry with a solid content of 50wt%, and stirred evenly. A copper foil with a thickness of 6μm, a length of 54mm, and a width of 17.5mm is selected as the negative electrode collector, and the negative electrode slurry is evenly coated on one surface of the negative electrode collector copper foil, and a second empty foil area not coated with the negative electrode slurry is reserved in the middle part of the length direction of the negative electrode collector, and dried at 90°C to obtain a single-sided negative electrode sheet. After the above steps are completed, the single-sided coating of the negative electrode sheet has been completed. After that, the above steps are repeated on the other surface of the negative electrode sheet to obtain a negative electrode sheet with a double-sided coating of the negative electrode active material layer. The single-sided coating weight of the negative electrode sheet is 7.64mg / cm 2 .

[0096] <Preparation of Separator Film>

[0097] Polyethylene (PE) with a thickness of 7 μm and a 2 μm aluminum oxide (Al2O3) coated porous film were used as isolation membranes.

[0098] <Preparation of Insulating Layer>

[0099] Polyethylene terephthalate is selected as the first substrate layer, and acrylic resin is selected as the first bonding layer, and the first bonding layer is compounded with the first substrate layer to form a first insulating layer with a thickness of 10 μm. The first insulating layer is bonded to the first empty foil area of ​​the positive electrode plate.

[0100] <Electrolyte Preparation>

[0101] In a dry argon atmosphere, ethylene carbonate, ethyl methyl carbonate and diethyl carbonate were mixed in a mass ratio of 30:50:20 to obtain an organic solution, and then lithium salt lithium hexafluorophosphate was added to the organic solvent to dissolve and mix evenly to obtain an electrolyte with a lithium salt concentration of 1.15 mol / L.

[0102] <Preparation of lithium-ion batteries>

[0103] The positive electrode tab and the negative electrode tab were die-cut from the prepared positive electrode sheet and negative electrode sheet, respectively, with a length of 12 mm and a width of 3 mm.

[0104] The multi-layer positive electrode sheets and the multi-layer negative electrode sheets prepared above are alternately stacked, and a separator is arranged between adjacent positive electrode sheets and negative electrode sheets, wherein the first insulating layer isolates the first connecting portion (empty foil section) and the second connecting portion (empty foil section) adjacent thereto. After stacking, the positive electrode sheets and the negative electrode sheets are folded along the first empty foil area and the second empty foil area, so that the positive electrode sheets form the first part and the third part, and the negative electrode sheets form the second part and the fourth part, forming an electrode assembly with a total of 22 layers of sheets.

[0105] A shell made of steel is selected, and the shell includes a first accommodating portion and a second accommodating portion. Along the first direction, the length of the first accommodating portion is less than the length of the second accommodating portion, wherein the first accommodating portion is flush with one side of the second accommodating portion, and a first step is formed on the other side. The first part and the second part are placed in the first accommodating portion, and the third part and the fourth part are placed in the second accommodating portion, and the connection between the first part and the third part is close to the flush sides of the two accommodating portions, and the first part, the second part, the third part and the fourth part all extend along the first direction.

[0106] The first pole is arranged on the first wall of the first accommodating part and is arranged toward the first notch of the first step. The multi-layer positive pole tabs are gathered and welded to the first pole through the aluminum sheet, and the multi-layer negative pole tabs are gathered and welded to the first wall through the nickel sheet. After dehydration at 80°C, the electrolyte is injected, and the lithium-ion secondary battery is obtained through the processes of packaging and liquid injection, formation, capacity test, voltage internal resistance test, etc.

[0107] Comparative Example 1 is different from Example 1 in that the first part is not connected to the third part, that is, the positive electrode sheet is not folded, and the first part and the third part are respectively used as separate positive electrode sheets. Each positive electrode sheet (including the first part and the third part) is connected to a positive electrode ear, and each positive electrode sheet is bent and extended to the first pole, and then connected to the first pole. The second part is not connected to the fourth part, that is, the negative electrode sheet is not folded, and the second part and the fourth part are respectively used as separate negative electrode sheets. Each negative electrode sheet (including the second part and the fourth part) is connected to a negative electrode ear, and each negative electrode sheet is bent and extended to the first wall portion, and then connected to the first wall portion. The relevant parameters are shown in Table 1 below.

[0108] Energy density test method: charge the battery to 4.5V with a constant current of 1C, then charge the battery to 0.05C with a constant voltage of 4.5V, discharge the battery to 3V with a constant current of 0.2C, and record the discharge energy E; observe along the second direction (the thickness direction of the first part, perpendicular to the first direction), the overall projected area of ​​the battery is S; along the second direction, the overall height of the battery is H, then the volume of the battery is recorded as V=S×H; then the energy density W=E / V.

[0109] Table 1

[0110] The positive electrode sheet is folded to form the first part and the third part Energy density (Wh / L) Comparative Example 1 no 575 Example 1 yes 583

[0111] According to the above Table 1, combined with Example 1 and Comparative Example 1, it can be known that the energy density of the lithium-ion secondary battery in Example 1 is greater than that in Comparative Example 1. In Example 1, by folding the positive electrode sheet and placing it in spaces of different lengths, it can better fit the structure of the shell, make full use of the space in the shell, and help improve the energy density of the secondary battery. In addition, after the first part and the third part are folded, the first part is directly arranged toward the first pole, directly connected to the first pole ear, and connected to the first pole through the first pole ear. The polarity of the entire first pole sheet can be led out through the first pole without bending the first pole ear, which can effectively improve the space utilization inside the shell, and help improve the energy density of the secondary battery. In addition, the first pole is arranged near the first opening of the shell, which can reduce the overall length of the lithium-ion secondary battery occupied by the first pole, thereby making full use of the space outside the shell, and further improving the energy density of the secondary battery.

[0112] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Under the concept of the present application, the technical features in the above embodiments or different embodiments may also be combined, the steps may be implemented in any order, and there are many other changes in different aspects of the present application as described above, which are not provided in detail for the sake of simplicity. Although the present application has been described in detail with reference to the aforementioned embodiments, a person of ordinary skill in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A secondary battery, comprising a housing and an electrode assembly, wherein the electrode assembly is disposed in the housing, and the electrode assembly comprises a first electrode sheet, a separator and a second electrode sheet which are stacked, characterized in that: The housing comprises a first wall portion, a second wall portion, a third wall portion, a fourth wall portion and a fifth wall portion; Along the first direction, the first wall portion is arranged opposite to the third wall portion, a first space is defined between the first wall portion and the third wall portion, and a distance from the first wall portion to the third wall portion is L1; Along the first direction, the second wall portion is arranged opposite to the third wall portion, a second space is defined between the second wall portion and the third wall portion, the second space is communicated with the first space, and a distance from the second wall portion to the third wall portion is L2, L1<L2; The fourth wall portion is connected between the first wall portion and the second wall portion, the fifth wall portion is connected between the first wall portion and the third wall portion, and the fifth wall portion, the first wall portion, the fourth wall portion and the second wall portion together form a first step; The first pole piece includes a first portion, a first connecting portion and a third portion, the first portion is disposed in the first space and extends along the first direction, the third portion is disposed in the second space and extends along the first direction, and the first connecting portion is connected between the first portion and the third portion at one end close to the third wall portion; A first pole lug is connected to one end of the first portion facing the first wall portion, a first pole is provided on the first wall portion, and the first pole lug is electrically connected to the first pole.

2. The secondary battery according to claim 1, characterized in that: 20%≤L1 / L2≤95%.

3. The secondary battery according to claim 1, characterized in that: The first connecting portion is a hollow foil segment, and the first pole piece is folded and arranged at two opposite ends of the first connecting portion.

4. The secondary battery according to claim 3, characterized in that: Along the thickness direction of the first pole piece, a first insulating layer is arranged between the first pole piece and the second pole piece, and the first insulating layer covers the first connecting portion.

5. The secondary battery according to claim 4, characterized in that: The first connecting portion is connected between the first portion and the third portion along the length direction of the first pole piece; in the first space, the first portion includes a first active material layer disposed facing the second pole piece; in the second space, the third portion includes a third active material layer facing the second pole piece; Along the length direction of the first pole piece, the length of the portion where the first insulating layer and the first active material layer overlap in the thickness direction of the first pole piece is D1, and the length of the portion where the first insulating layer and the third active material layer overlap in the thickness direction of the first pole piece is D3; 0.2mm≤D1≤2mm, and / or, 0.2mm≤D3≤2mm.

6. The secondary battery according to claim 5, characterized in that: The first insulating layer is bonded to the first pole piece, and the first pole piece is a positive pole piece.

7. The secondary battery according to claim 4, characterized in that: The first insulating layer is a glue layer, the first insulating layer includes a first substrate layer and a first adhesive layer disposed on the surface of the first substrate layer, the first substrate layer includes at least one of polyimide or polyethylene terephthalate, and the first adhesive layer includes at least one of polytetrafluoroethylene, polypropylene, polyethylene or acrylic resin; or, The first insulating layer is an insulating coating, and the first insulating layer includes at least one of aluminum oxide, magnesium oxide, boehmite or zirconium oxide.

8. The secondary battery according to claim 1, characterized in that: The housing further includes a sixth wall portion, the sixth wall portion being connected between the second wall portion and the third wall portion; Along the second direction, the distance from the fourth wall portion to the sixth wall portion is L4, and the distance from the fifth wall portion to the sixth wall portion is L5, L4<L5; The second direction is the direction from the first space to the second space.

9. The secondary battery according to claim 8, characterized in that: Along the first direction, the projection of the first pole is located within the projection of the sixth wall portion.

10. The secondary battery according to claim 8, characterized in that: The housing further includes a seventh wall portion and an eighth wall portion, wherein the seventh wall portion and the eighth wall portion are both connected between the first wall portion and the third wall portion, and along the third direction, the seventh wall portion and the eighth wall portion are arranged opposite to each other, the first space is located between the seventh wall portion and the eighth wall portion, and the distance from the seventh wall portion to the eighth wall portion is L7; The housing further includes a ninth wall portion and a tenth wall portion, wherein the ninth wall portion and the tenth wall portion are both connected between the second wall portion and the third wall portion, and along the third direction, the ninth wall portion and the tenth wall portion are arranged opposite to each other, and the second space is located between the ninth wall portion and the tenth wall portion, and the distance from the ninth wall portion to the tenth wall portion is L9, L7≤L9; The fourth wall portion extends between the seventh wall portion and the ninth wall portion, and the fourth wall portion is connected to the seventh wall portion and the ninth wall portion; the fifth wall portion, the seventh wall portion, the fourth wall portion and the ninth wall portion together form a second step; The fourth wall portion extends between the eighth wall portion and the tenth wall portion, and the fourth wall portion is connected to the eighth wall portion and the tenth wall portion, and the fifth wall portion, the eighth wall portion, the fourth wall portion and the tenth wall portion together form a third step; Along the third direction, the width of the first portion is W1, the width of the third portion is W3, and W1≤W3; The first direction, the second direction, and the third direction are perpendicular to each other.

11. The secondary battery according to claim 10, characterized in that: 10%≤L7 / L9≤100%, 10%≤W1 / W3≤100%.

12. The secondary battery according to claim 10, characterized in that: A first chamfered portion is provided at a connection between the first wall portion and the seventh wall portion, a first avoidance position is provided at the first portion, a shape of the first avoidance position corresponds to the first chamfered portion, and the first avoidance position is arranged facing the first chamfered portion; and / or, A second chamfered portion is provided at a connection between the second wall portion and the ninth wall portion, and a second avoidance position is provided at the third portion. The shape of the second avoidance position corresponds to the second chamfered portion, and the second avoidance position is arranged facing the second chamfered portion.

13. The secondary battery according to claim 1, characterized in that: The shell includes a accommodating portion and a sixth wall portion, the accommodating portion includes the first wall portion, the second wall portion, the third wall portion, the fourth wall portion and the fifth wall portion which are integrally arranged, and the accommodating portion encloses the first space and the second space, and the accommodating portion is provided with an opening on a side of the second space away from the first space, and the opening is communicated with the second space, and the sixth wall portion is connected to the accommodating portion and covers the opening.

14. The secondary battery according to any one of claims 1 to 13, characterized in that: The secondary battery comprises a plurality of first pole sheets and a plurality of first pole tabs, and the first portion of each of the first pole sheets is connected to one of the plurality of first pole tabs; The secondary battery further includes a first adapter, the first pole tabs of the plurality of first pole sheets are all connected to the first adapter, and the first adapter is connected to the first pole column.

15. The secondary battery according to claim 1, characterized in that: The second pole piece includes a second portion, a second connecting portion and a fourth portion, the second portion is disposed in the first space and extends along the first direction, the fourth portion is disposed in the second space and extends along the first direction, and the second connecting portion is connected between the second portion and the fourth portion at one end close to the third wall portion; Along the second direction, the first part and the second part are stacked, and the third part and the fourth part are stacked; wherein the second direction is the direction from the first space to the second space; A second pole lug is connected to one end of the second portion facing the first wall portion, a second pole is provided on the first wall portion, and the second pole lug is electrically connected to the second pole.

16. The secondary battery according to claim 1, characterized in that: The second pole piece includes a second portion, a second connecting portion and a fourth portion, the second portion is disposed in the first space and extends along the first direction, the fourth portion is disposed in the second space and extends along the first direction, and the second connecting portion is connected between the second portion and the fourth portion at one end close to the third wall portion; Along the second direction, the first part and the second part are stacked, and the third part and the fourth part are stacked; wherein the second direction is the direction from the first space to the second space; A second pole lug is connected to one end of the second portion facing the first wall portion, and the second pole lug is electrically connected to the first wall portion; The shell is a metal shell, and the metal shell includes one of aluminum, steel, stainless steel, nickel or copper.

17. The secondary battery according to claim 15 or 16, characterized in that: The second connecting portion is a hollow foil segment, and the second pole piece is folded and arranged at two opposite ends of the second connecting portion.

18. An electronic device, characterized in that: Includes the secondary battery according to any one of claims 1 to 17.

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