Secondary battery and electronic device

Abstract

The invention discloses a secondary battery and electronic equipment. The secondary battery comprises a shell, a connecting sheet, a pole and a sealing element, a containing cavity is defined by the shell, the shell comprises a first wall part, and a first through hole communicated with the containing cavity is formed in the first wall part. The connecting piece is arranged on the first wall part and provided with a second through hole, the second through hole is communicated with the first through hole, and a passivation layer is arranged on the side, away from the first wall part, of the connecting piece. The pole comprises a pole body and a flange part, the flange part is arranged on the side, away from the first wall part, of the connecting piece, the pole body is connected with the flange part, and the pole body is partially arranged in the first through hole and the second through hole. And the sealing piece is adhered between the passivation layer and the flange part. According to the secondary battery, the bonding strength of the connecting piece and the shell can be improved, the sealing performance of the secondary battery is improved, in addition, the passivation layer is arranged on the connecting piece, the corrosion resistance, the sealing performance, the adhesion performance and the insulativity can be improved in one step, and the production process of the secondary battery is simplified.

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] With the rapid development of new energy technology, batteries have been widely used in mobile phones, laptops, electric vehicles and other fields. For hard shell batteries, the polarity is usually drawn out by the pole. During the installation of the pole, the pole is usually riveted to form a flange, and the seal is compressed between the pole and the shell to achieve sealing. However, the riveted pole structure is less stable and easily leads to poor sealing. Summary of the invention

[0003] The present application aims to provide a secondary battery and an electronic device, which can improve the sealing performance of the secondary battery.

[0004] In the first aspect, the present application proposes a secondary battery, including a shell, a connecting piece, a pole and a seal. The shell encloses a accommodating cavity, and the shell includes a first wall portion, and the first wall portion is provided with a first through hole communicating with the accommodating cavity. The connecting piece is arranged on the first wall portion, and the connecting piece is provided with a second through hole, and the second through hole is communicated with the first through hole, and a passivation layer is arranged on the side of the connecting piece away from the first wall portion. The pole includes a column and a flange portion, and the flange portion is arranged on the side of the connecting piece away from the first wall portion, and the column is connected to the flange portion, and the column portion is arranged in the first through hole and the second through hole. The seal is bonded between the passivation layer and the flange portion.

[0005] In the above technical solution, the passivation layer can improve the interfacial bonding force between the connecting piece and the seal, and can make the seal better interact with the surface of the connecting piece during the curing or bonding process to form a stronger bond, thereby improving the reliability of the entire connection structure and reducing the risk of the seal falling off or the connection loosening due to factors such as vibration and thermal cycling. Furthermore, the passivation layer is conducive to better fitting of the seal and the connecting piece, so that the seal can be more tightly bonded to the passivation layer, reducing the risk of gaps or leakage at the seal, thereby enhancing the sealing, further reducing electrolyte leakage and reducing external impurities from entering the secondary battery. In addition, the passivation layer can play an isolating and protective role, which can reduce the direct contact between the connecting piece and the electrolyte, reduce the corrosion or oxidation of the surface of the connecting piece, thereby extending the service life of the connecting piece and improving the stability of its mechanical properties. In addition, the passivation layer itself has certain insulating properties, which can further improve the insulation effect between the connecting piece and the pole flange, which is conducive to reducing the short circuit phenomenon inside the secondary battery and improving the safety of the secondary battery. In addition, the passivation layer is disposed on the connecting sheet, which can integrate the improvement of corrosion resistance, the improvement of sealing, the improvement of adhesion and the improvement of insulation in one step, thereby simplifying the production process of the secondary battery.

[0006] In some embodiments, the first wall portion includes a first wall surface facing away from the accommodating cavity and a second wall surface facing the accommodating cavity. The connecting piece is welded to the second wall surface to form a first welding portion. The connecting piece itself can be used as a barrier to block the impact of spatter and sparks generated by welding on the passivation layer. At the same time, it also reduces the impact of the high-temperature oxidizing environment on the passivation layer, which is beneficial to protecting the integrity of the passivation layer between the connecting piece and the seal, thereby allowing the passivation layer to provide a better sealing bonding platform, which can improve the connection stability between the pole and the shell on the one hand, and improve the sealing of the secondary battery on the other hand.

[0007] In some embodiments, when viewed in the opposite direction of the first direction, the passivation layer between the connecting piece and the sealing member includes a non-welding area, and along the second direction, the width of the non-welding area is W2, 0.6mm≤W2≤1.8mm, which is conducive to the passivation layer still maintaining better protection, insulation and improved adhesion properties, thereby improving the sealing of the secondary battery. The first direction is the direction from the first wall to the second wall, and the second direction is the direction from the outer diameter to the inner diameter of the connecting piece.

[0008] In some embodiments, when observed along the first direction, the first welding portion is arranged around the first through hole, and along the second direction, the width of the first welding portion is W1, 0.03mm≤W1≤0.3mm, so that there is a sufficient welding area between the connecting piece and the shell, reducing the impact on the passivation layer between the connecting piece and the seal, and making the connecting piece and the shell more firmly combined, which is conducive to bearing various stresses generated by the secondary battery during the charging and discharging process, and improving the stability of the secondary battery structure and the reliability of the electrical connection.

[0009] In some embodiments, 0.08 mm ≤ W1 ≤ 0.15 mm. Within this range, the first welding portion can provide a more suitable bonding area, further enhancing the welding strength between the connecting piece and the first wall portion of the shell.

[0010] In some embodiments, the first wall portion includes a first wall surface facing away from the accommodating cavity and a second wall surface facing the accommodating cavity. The connecting piece is arranged on the second wall surface, and a convex portion is convexly provided on the surface of the connecting piece facing away from the sealing member, the second through hole passes through the convex portion, the convex portion is at least partially arranged in the first through hole, and the convex portion is welded to the inner wall of the first through hole. The setting of the convex portion provides a more easily operated part for welding, which is more conducive to the welding of the connecting piece and the shell, reduces the heat effect on other parts of the connecting piece and the shell during the welding process, improves the performance of the connecting piece and the integrity of the shell, and also helps to improve the welding efficiency.

[0011] In some embodiments, the first wall portion includes a first wall surface facing away from the accommodating cavity and a second wall surface facing the accommodating cavity, and the connecting piece is arranged on the first wall surface; the wall surface of the connecting piece facing the second through hole is welded to the inner wall of the first through hole. When welding is performed from the side, the welding heat source directly acts on the inner wall of the second through hole and the inner wall of the first through hole, and the welding heat is mainly conducted along the inner wall of the second through hole and the inner wall of the first through hole, so that the area where the passivation layer is located between the connecting piece and the sealing member receives relatively less heat, thereby reducing the risk of the passivation layer being damaged due to overheating.

[0012] In some embodiments, the passivation layer includes chromium oxide, nickel oxide or aluminum oxide, which has better corrosion resistance and high temperature resistance, can reduce electrolyte corrosion and reduce the impact of welding on the passivation layer.

[0013] In some embodiments, the entire outer surface of the connecting piece is provided with a passivation layer, which can further protect the connecting piece and reduce corrosion of the connecting piece.

[0014] In some embodiments, the sealing member includes hot melt adhesive and / or pressure sensitive adhesive, and can be connected to the first wall portion by hot pressing during installation, which is simple and convenient to operate and is beneficial to improving the production efficiency of the secondary battery.

[0015] In some embodiments, the seal comprises a first insulating layer and a second insulating layer stacked, the first insulating layer is bonded between the second insulating layer and the connecting sheet, the melting point of the first insulating layer is T1, 100°C≤T1≤130°C, and any value between 100°C and 130°C can be selected, such as 100°C, 105°C, 110°C, 115°C, 120°C, 125°C or 130°C. The melting point of the second insulating layer is T2, 140°C≤T2≤190°C, and any value between 140°C and 190°C can be selected, such as 140°C, 145°C, 150°C, 155°C, 160°C, 165°C, 170°C, 175°C, 180°C, 185°C or 190°C. The first insulating layer has a lower melting point and will melt first in the temperature range of 100°C to 130°C, thereby forming a pressure relief channel connecting the inside of the shell with the outside world, which can effectively alleviate thermal runaway and reduce the risk of fire or explosion of the secondary battery. In addition, the second insulating layer has a higher melting point. When the first insulating layer melts, the second insulating layer can remain in a solid state, thereby insulating the pole and the shell, thereby reducing the occurrence of short circuits.

[0016] In some embodiments, the seal also includes a third insulating layer, and the third insulating layer is bonded between the second insulating layer and the flange portion along the direction from the first wall portion to the connecting piece, and the melting point of the third insulating layer is T3, 100°C ≤ T3 ≤ 130°C. Under normal operating temperature, the three insulating layers are in a solid state, which can provide a thicker insulation and sealing barrier and improve the bonding strength between the connecting piece and the pole. When the internal temperature of the secondary battery rises, the first insulating layer and the third insulating layer melt, providing more pressure relief channels for the gas inside the secondary battery, which is conducive to timely response to the abnormal increase in the temperature of the secondary battery, and can further alleviate thermal runaway and reduce the risk of fire or explosion of the secondary battery.

[0017] In some embodiments, the first insulating layer, the second insulating layer, and the third insulating layer are independently selected from at least one of PP, LDPE, HDPE, LLDPE, OPP, PS, PVC, PET, PA, or PF. Each material has good chemical stability, can withstand the erosion of the electrolyte, reduce the damage of the seal due to chemical corrosion, and thus improve the sealing of the seal. In addition, each material has low permeability to gas and liquid, which can reduce the leakage of the internal electrolyte, and prevent external air, moisture, etc. from entering the interior of the secondary battery, which is conducive to maintaining the normal operation of the secondary battery.

[0018] In some embodiments, the thickness of the sealant along the direction from the first wall to the connecting piece is H, 0.05mm≤H≤1mm. Under normal temperature conditions, this thickness range enables the sealant to have a good insulation effect. When the temperature rises, the first insulating layer and the third insulating layer will melt according to their melting point characteristics, thereby forming a better pressure relief channel to quickly respond to abnormal increases in the temperature of the secondary battery.

[0019] In some embodiments, 0.1mm≤H≤0.3mm, the thermal response of each insulating layer at high temperature is more precise, which can improve the connection stability between the pole and the connecting piece on the one hand, and can respond to abnormal increases in the stability of the secondary battery in a timely manner on the other hand.

[0020] In some embodiments, along the direction from the first wall to the second wall, the thickness of the connecting sheet is H4, 0.04mm≤H4≤0.5mm, so that the connecting sheet has better structural strength, reduces the deformation of the connecting sheet during the assembly and vibration of the secondary battery, and can reduce the impact of welding on the passivation layer between the connecting sheet and the seal, which can facilitate the welding of the connecting sheet and the shell, and is conducive to improving the connection strength between the connecting sheet and the shell. Furthermore, 0.1mm≤H4≤0.3mm can further reduce the impact on the passivation layer during welding, and reduce the impact on the energy density of the secondary battery.

[0021] In some embodiments, the diameter of the column is R, 0.1mm≤R≤0.6mm. Compared with the riveted pole, the gluing method reduces the mechanical stress and deformation generated during the riveting process, so that the pole can maintain a more precise size and shape, which is beneficial to improve the structural integrity of the pole in the case of small diameter.

[0022] 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.

[0023] 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

[0024] 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.

[0025] Figure 1 A schematic diagram of an exploded structure of a secondary battery according to some embodiments of the present application;

[0026] Figure 2 This is a schematic diagram of the connection structure between the pole and the housing in some embodiments of the present application;

[0027] Figure 3 This is a schematic diagram of the connection structure between the pole and the housing in some embodiments of the present application;

[0028] Figure 4 This is a schematic diagram of the connection structure between the pole and the housing in some embodiments of the present application;

[0029] Figure 5 A schematic diagram of the structure of a passivation layer in some embodiments of the present application;

[0030] Figure 6 A schematic diagram of the structure of a passivation layer in some embodiments of the present application;

[0031] Figure 7 This is a schematic diagram of the connection structure between the pole and the housing in some embodiments of the present application;

[0032] Figure 8 This is a schematic diagram of the connection structure between the pole and the housing in some embodiments of the present application;

[0033] Fig. 9 This is a schematic diagram of the connection structure between the pole and the housing in some embodiments of the present application;

[0034] Fig.10 This is a schematic diagram of the connection structure between the pole and the housing in some embodiments of the present application;

[0035] Fig.11 This is a schematic diagram of the connection structure between the pole and the housing in some embodiments of the present application;

[0036] Fig.12 This is a schematic diagram of the connection structure between the pole and the housing in some embodiments of the present application;

[0037] Fig.13 This is a schematic diagram of the connection structure between the pole and the housing in some embodiments of the present application;

[0038] Fig.14 This is a schematic diagram of the structure of the seal according to some embodiments of the present application.

[0039] Description of reference numerals:

[0040] 100. Secondary battery;

[0041] 10. Shell; 10a. Main body; 10b. Cover; 11. Accommodating cavity; 12. First wall; 121. First wall surface; 122. Second wall surface; 13. First through hole;

[0042] 20. Electrode assembly;

[0043] 30. Pole; 31. Column; 32. Flange;

[0044] 40. sealing member; 41. first insulating layer; 42. second insulating layer; 43. third insulating layer; 44. third through hole;

[0045] 50. Connecting sheet; 51. Passivation layer; 52. Metal sheet; 53. Second through hole; 54. Protrusion;

[0046] 60. First welding part;

[0047] X, first direction; Y, second 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" 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] The technical features involved in the different embodiments of the present application described below can be combined with each other as long as they do not conflict with each other.

[0053] 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 , a pole 30 , a seal 40 and a connecting sheet 50 .

[0054] For the housing 10, please refer to Figure 1 The shell 10 encloses a accommodating cavity 11, and the accommodating cavity 11 can accommodate the electrode assembly 20 and the electrolyte (not shown in the figure). The electrolyte infiltrates the electrode assembly 20 in the accommodating cavity 11, so that an electrochemical reaction occurs. In an embodiment of the present application, the shell 10 can be formed by punching a conductive metal layer, and the thickness of the conductive metal layer can be set to 0.1mm to 0.4mm, so that the shell 10 has a high punching strength. Among them, the conductive metal layer can be made of conductive metal materials such as 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 pole 30 can lead to another polarity. In some other embodiments, the shell 10 can also use soft package materials such as aluminum-plastic film or copper-plastic film, so that the shell 10 has better ductility.

[0055] The housing 10 may be in a square, trapezoidal or cylindrical shape. For example, the square housing 10 is shown in FIG. Figure 1 The housing 10 includes a main body 10a and a cover 10b. The main body 10a is provided with a pit, and one end of the main body 10a is open, and the electrode assembly 20 can be directly placed in the pit through the open end. The cover 10b is connected to the main body 10a and covers the pit, so that the pit forms a receiving chamber 11.

[0056] Please refer to Figure 1 and Figure 2The housing 10 includes a first wall portion 12, which includes a first wall surface 121 facing away from the accommodating cavity 11 and a second wall surface 122 facing the accommodating cavity 11. The first wall portion 12 is provided with a first through hole 13, which passes through the first wall surface 121 and the second wall surface 122, and the first through hole 13 is communicated with the accommodating cavity 11. The pole 30 can be disposed in the first through hole 13 for one polarity of the secondary battery 100.

[0057] For the electrode assembly 20, please refer to Figure 1 The electrode assembly 20 is disposed in the accommodating cavity 11 of the shell 10 , and the shape of the electrode assembly 20 can be configured to match the shell 10 to fully utilize the space of the accommodating cavity 11 of the shell 10 and improve the energy density of the secondary battery 100 .

[0058] The electrode assembly 20 includes a positive electrode sheet (not shown in the figure), a negative electrode sheet (not shown in the figure) and a separator (not shown in the figure), and the positive electrode sheet, the separator and the negative electrode sheet are stacked and wound to form a wound electrode assembly 20. Alternatively, a plurality of positive electrode sheets and a plurality of negative electrode sheets are alternately stacked, and a separator is provided between adjacent positive electrode sheets and negative electrode sheets to form a stacked electrode assembly 20.

[0059] The negative electrode sheet of the electrode assembly 20 can be directly electrically connected to the shell 10, so that the shell 10 leads to the negative electrode, and the positive electrode sheet of the electrode assembly 20 can be electrically connected to the pole 30, so that the pole 30 leads to the positive electrode. In some other embodiments, the shell 10 can also lead to the positive electrode, and the pole 30 leads to the negative electrode.

[0060] For the above-mentioned pole 30, please refer to Figure 1 to Figure 2 The pole 30 is disposed on the first wall 12, a portion of the pole 30 is electrically connected to the electrode assembly 20 in the accommodating cavity 11, and the other portion is exposed from the first wall 12. For example, the pole 30 includes a column 31 and a flange 32 connected to each other. The flange 32 has a larger width and can be connected to the first wall 12. The wider flange 32 can provide a larger connection area, which is beneficial to improving the connection strength between the shell 10 and the pole 30. The column 31 extends into the first through hole 13 to lead out one polarity of the secondary battery 100. For example, please refer to Figure 2 The flange portion 32 can be connected to the first wall surface 121 of the first wall portion 12. At this time, the column 31 extends into the shell 10 through the first through hole 13, so that the column 31 can be electrically connected to the positive electrode sheet or the negative electrode sheet of the electrode assembly 20, and the flange portion 32 is exposed outside the shell 10, and the positive electrode or the negative electrode of the secondary battery 100 can be led out.

[0061] In some other embodiments, please refer to Figure 3The flange portion 32 is connected to the second wall surface 122 of the first wall portion 12 , the flange portion 32 is electrically connected to the positive electrode sheet or the negative electrode sheet of the electrode assembly 20 , and the column 31 is exposed through the first through hole 13 , so that the entire column 30 leads to the positive electrode or the negative electrode of the secondary battery 100 .

[0062] For the seal 40, please refer to Figure 1 and Figure 2 The seal 40 is bonded between the housing 10 and the flange 32, and can seal the installation gap between the housing 10 and the flange 32, so that the first through hole 13 is sealed, reducing electrolyte leakage and reducing external water vapor from entering the housing 10. In the embodiment of the present application, the polarity of the pole 30 and the housing 10 is opposite, and the seal 40 can insulate the pole 30 from the housing 10 to reduce the occurrence of short circuits.

[0063] For the above-mentioned connecting piece 50, please refer to Figure 1 and Figure 2 The connecting piece 50 is disposed on the first wall portion 12 , and the connecting piece 50 is provided with a second through hole 53 , the second through hole 53 is communicated with the first through hole 13 , and the column 31 of the pole 30 can be disposed in the first through hole 13 and the second through hole 53 , thereby leading out the polarity.

[0064] The seal 40 can be bonded between the connecting piece 50 and the flange portion 32 of the pole 30. During the assembly process of the secondary battery 100, the connecting piece 50 can be first fixed to the first wall portion 12, and then the pole 30 can be accurately installed at a predetermined position through the cooperation of the second through hole 53 and the first through hole 13, and the sealing piece 40 is used for bonding and fixing, which is conducive to improving the production efficiency of the secondary battery 100. In addition, the overall connection form of the pole 30, the seal 40 and the connecting piece 50 can be removed from the shell 10 separately. For example, when the inside of the secondary battery 100 or the shell 10 is damaged, the overall connection form of the pole 30, the seal 40 and the connecting piece 50 can be removed and installed in the shell 10 of other secondary batteries 100, which is conducive to enhancing the standardization and generalization of the sealing structure of the pole 30.

[0065] In the embodiment of the present application, a passivation layer 51 is provided on the side of the connecting piece 50 away from the first wall portion 12. For example, the connecting piece 50 includes a metal sheet 52. The passivation layer 51 is formed by surface treatment of the metal sheet 52. The seal 40 is bonded between the passivation layer 51 of the connecting piece 50 and the flange portion 32. The passivation layer 51 can reduce the corrosion or oxidation of the surface of the connecting piece 50. The electrolyte inside the secondary battery 100 has a certain corrosiveness. The passivation layer 51 can play an isolation and protection role, which can reduce the direct contact between the connecting piece 50 and the electrolyte, thereby extending the service life of the connecting piece 50 and improving the stability of its mechanical properties. In addition, the passivation layer 51 itself has a certain insulating property, which can further improve the insulation effect between the connecting piece 50 and the flange portion 32 of the pole 30, which is conducive to reducing the short circuit phenomenon inside the secondary battery 100 and improving the safety of the secondary battery 100.

[0066] At the same time, the inventors of the present application further discovered that the passivation layer 51 can improve the interfacial bonding force between the connecting piece 50 and the sealing member 40, and can make the sealing member 40 better interact with the surface of the connecting piece 50 during the curing or bonding process to form a stronger bond. For example, the formation process of the passivation layer 51 will change the chemical composition of the surface of the connecting piece 50, and some active groups can be introduced, which can react chemically with the corresponding groups in the material of the sealing member 40 to form chemical bonds, thereby enhancing the chemical bond bonding between the connecting piece 50 and the sealing member 40, thereby improving the reliability of the entire connection structure and reducing the risk of the sealing member 40 falling off or the connection being loose due to factors such as vibration and thermal cycles. In addition, the passivation layer 51 enables the sealing member 40 to be more tightly bonded to the passivation layer 51, reducing the risk of gaps or leakage at the seal, thereby enhancing the sealing, further reducing electrolyte leakage and reducing the entry of external impurities into the interior of the secondary battery 100.

[0067] In addition, in the embodiment of the present application, the passivation layer 51 is disposed on the connecting sheet 50, and the improvement of corrosion resistance, sealing performance, adhesion performance, and insulation performance can be integrated in one step, simplifying the production process of the secondary battery 100. Moreover, when the connecting sheet 50 has a problem and needs to be repaired or replaced, the passivation layer 51 is disposed on the connecting sheet 50 and the sealing member 40 is bonded, so that it can be easily disassembled and installed, with little impact on the housing 10 and other components, which is conducive to later maintenance.

[0068] In some embodiments, please refer to Figure 3 and Figure 4, the connecting piece 50 is welded to the second wall surface 122 to form a first welding portion 60. After the connecting piece 50 is arranged on the second wall surface 122, laser penetration welding can be performed on the first wall surface 121 of the first wall portion 12, so that the part of the first wall portion 12 and the part of the connecting piece 50 are rapidly melted to form the first welding portion 60. When the connecting piece 50 is welded to the first wall portion 12, the welding energy directly acts on the contact interface between the two. Since the passivation layer 51 is away from the connection position between the connecting piece 50 and the first wall portion 12, the connecting piece 50 itself can be used as a barrier to block the spatter and sparks generated by welding from impacting the passivation layer 51 between the connecting piece 50 and the sealing member 40. At the same time, the influence of the high temperature oxidation environment on the passivation layer 51 is also reduced, which is beneficial to protecting the integrity of the passivation layer 51, thereby enabling the passivation layer 51 to provide a better bonding platform for the sealing member 40, which improves the connection stability between the pole 30 and the shell 10 on the one hand, and improves the sealing of the secondary battery 100 on the other hand.

[0069] Observed in the opposite direction of the first direction X, the passivation layer 51 includes a non-welding area 511. In the second direction Y, the width of the non-welding area 511 is W2, 0.6 mm ≤ W2 ≤ 1.8 mm, and any value from 0.6 mm to 1.8 mm can be selected, for example, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, 1 mm, 1.1 mm, 1.2 mm, 1.3 mm, 1.4 mm, 1.5 mm, 1.6 mm, 1.7 mm or 1.8 mm, etc. The passivation layer 51 can be effectively protected, and the non-welding area 511 is limited to 0.6 mm to 1.8 mm, which is conducive to the passivation layer 51 still maintaining better protection, insulation, and improved adhesion properties. If it is less than the lower limit, for example, less than 0.6 mm, the protective function of the passivation layer 51 is weakened, which may easily lead to corrosion of the passivation layer 51, and the small non-welding area 511 will affect the bonding strength between the connecting piece 50 and the sealing member 40, resulting in a weakening of the bonding strength between the sealing member 40 and the connecting piece 50, which may cause a decrease in the stability of the internal structure of the secondary battery 100. If it is greater than the upper limit, for example, greater than 1.8 mm, an overly large non-welding area 511 means that the surrounding area that can be effectively welded is relatively smaller. In order to ensure the welding quality, it may be necessary to control higher precision and more accurate energy output, which will reduce welding efficiency, increase production time and cost, and may also lead to a weakening of the bonding strength between the shell 10 and the connecting piece 50.

[0070] In some embodiments, please refer to Figure 5 The non-welding area 511 includes a first non-welding area 511a and a second non-welding area 511b. The width W2 of the non-welding area 511 is the width W of the first non-welding area 511a. 21 The width W of the second non-welding area 511b is 22 In some other embodiments, please refer to Figure 6, the edge of the welding area 512 coincides with the inner diameter of the connecting piece 50 , and the width of the non-welding area 511 is W2 . Optionally, the width of the welding area may also coincide with the outer diameter of the connecting piece 50 .

[0071] In some embodiments, the width of the welding area 512 of the passivation layer 51 may be selected to be less than 0.2 mm to reduce damage to the passivation layer 51 caused by the welding area 512 .

[0072] The first direction X is the direction from the first wall surface 121 to the second wall surface 122, and the second direction Y is the direction from the outer diameter to the inner diameter of the connecting piece 50. The connecting piece 50 is provided with a second through hole 53, and the diameter of the second through hole 53 is the inner diameter of the connecting piece 50. It should be noted that the outer diameter may be the outer diameter of the connecting piece 50 itself or the outer diameter of the fitting circle where it is located, and the inner diameter may be the inner diameter of the connecting piece 50 itself or the diameter of the fitting circle where the second through hole 53 is located. The second direction Y may be perpendicular to the first direction X.

[0073] In some embodiments, when viewed along the first direction X, the first welding portion 60 is disposed around the first through hole 13, and along the second direction Y, the width of the first welding portion 60 is W1, 0.03mm≤W1≤0.3mm, and any value between 0.03mm and 0.3mm can be selected, for example, 0.03mm, 0.04mm, 0.05mm, 0.06mm, 0.07mm, 0.08mm, 0.09mm, 0.1mm, 0.13mm, 0.15mm, 0.17mm, 0.19mm, 2mm, 2.3mm, 2.5mm, 2.9mm or 3mm, etc. This allows the connection sheet 50 and the housing 10 to have a sufficient welding area, so that the two are firmly combined together, which is conducive to bearing various stresses generated by the secondary battery 100 during the charging and discharging process, and improving the structural stability of the secondary battery 100 and the reliability of the electrical connection.

[0074] If the width of the welding portion is small, for example, less than 0.03 mm, the welding joint area between the connecting piece 50 and the first wall portion 12 of the shell 10 will be small, and sufficient connection strength cannot be provided. During the use of the secondary battery 100, the connecting piece 50 may fall off from the shell 10 due to external force or thermal stress, causing the internal connection of the secondary battery 100 to fail, thereby affecting the performance of the secondary battery 100.

[0075] If the welding width is large, for example, exceeding 0.3 mm, excessive heat generated during the welding process will be transferred to the connecting piece 50 and the shell 10, forming a larger heat radiation area, which may cause the mechanical properties of the connecting piece 50 to deteriorate, such as causing damage to the passivation layer 51, or even directly causing the welding area to extend to the passivation layer 51, causing damage to the passivation layer 51, thereby weakening the bonding strength between the seal 40 and the passivation layer 51, affecting the stability of the connection between the pole 30 and the shell 10, and affecting the sealing of the secondary battery 100.

[0076] It can be understood that the connecting piece 50 is provided with a second through hole 53, that is, the connecting piece 50 is annular, and when the connecting piece 50 is welded to the first wall portion 12, the welding area is arranged around the first through hole 13 and the second through hole 53, that is, the first welding portion 60 is also annular, and the width of the first welding portion 60 is half of the difference between the outer diameter of the welding area and the inner diameter of the welding area. Among them, the outer diameter can be regarded as the diameter of the welding area itself or the diameter of the fitting circle where the welding area is located, and the inner diameter can also be determined similarly.

[0077] Furthermore, 0.08mm≤W1≤0.15mm, within this range, the first welding portion 60 can provide a more suitable bonding area, further enhancing the welding strength between the connecting piece 50 and the first wall portion 12 of the shell 10. Compared with the above-mentioned lower limit of 0.03mm, the width of 0.08mm makes the force distribution of the welding point more uniform, reducing the risk of cracking or falling off at the welding point due to local stress concentration, thereby improving the stability and reliability of the secondary battery 100 during long-term use. At the same time, the upper limit of 0.15mm is more conducive to accurately controlling the conduction of welding heat compared to 0.3mm, which is conducive to reducing the impact on the passivation layer 51 of the connecting piece 50, and reducing problems such as excessive damage to the passivation layer 51 due to overheating and obvious deformation of the shell 10.

[0078] In some embodiments, please refer to Figure 7 and Figure 8 The connecting piece 50 is disposed on the second wall surface 122, a convex portion 54 is convexly disposed on the surface of the connecting piece 50 facing away from the sealing member 40, the second through hole 53 passes through the convex portion 54, the convex portion 54 is at least partially disposed in the first through hole 13, and the convex portion 54 is welded to the inner wall of the first through hole 13. For example, the convex portion 54 and the inner wall of the first through hole 13 are directly laser-penetrated and welded on the first wall portion 121 of the first wall portion 12, so that the connecting piece 50 and the first wall portion 12 can be fixed.

[0079] The welding of the protrusion 54 and the inner wall of the first through hole 13 can make the connection between the two more firmly, thereby effectively improving the connection strength between the connecting piece 50 and the shell 10. For example, when the secondary battery 100 is subjected to external impact, vibration, or thermal stress generated during the charging and discharging process, the connecting piece 50 can be reduced from falling off the shell 10, thereby improving the stability of the secondary battery 100 structure.

[0080] Furthermore, the setting of the convex portion 54 provides a more easily operable position for welding, and the convex portion 54 is further away from the passivation layer 51 of the connecting piece 50. When welding, the convex portion 54 is welded to the inner wall of the first through hole 13, which makes it easier to control the welding position and welding quality compared to welding at other parts of the connecting piece 50. Laser and other welding processes can more accurately act on the contact area between the convex portion 54 and the inner wall of the first through hole 13, reduce the thermal impact on the passivation layer 51 and the housing 10 during the welding process, improve the performance of the connecting piece 50 and the integrity of the housing 10, and also help to improve the welding efficiency.

[0081] In addition, since the protrusion 54 is at least partially arranged in the first through hole 13, it is convenient to position and install the connecting piece 50 and the first wall portion 12. When the seal 40 is bonded between the connecting piece 50 and the flange portion 32 of the pole 30, it is convenient to make the seal 40 more accurately fill the corresponding position during the installation process, reduce the sealing gap, thereby improving the sealing performance and more effectively reducing the leakage of electrolyte inside the secondary battery 100 and the intrusion of external impurities.

[0082] In some embodiments, please refer to Figure 2 and Fig. 9 The first wall portion 12 includes a first wall surface 121 facing away from the accommodating cavity 11 and a second wall surface 122 facing the accommodating cavity 11. The connecting piece 50 is arranged on the first wall surface 121. The wall surface of the connecting piece 50 facing the second through hole 53 is welded to the inner wall of the first through hole 13. In the embodiment of the present application, the side welding is adopted, which is welding from the side. The welding heat source directly acts on the inner wall of the second through hole 53 and the inner wall of the first through hole 13. The welding heat is mainly conducted along the inner wall of the second through hole 53 and the inner wall of the first through hole 13, so that the heat received by the area where the passivation layer 51 is located is relatively small, reducing the risk of the passivation layer 51 being damaged due to overheating.

[0083] It should be noted that, no matter which welding method is used, the welding width can be 0.03 mm to 0.3 mm, so that there is enough welding area between the connecting piece 50 and the shell 10, so that the two are firmly combined together, and the influence of welding on the passivation layer 51 between the connecting piece 50 and the sealing member 40 is reduced, so that the sealing of the secondary battery 100 can be improved while improving the connection stability. Similarly, the welding width can be preferably 0.08 mm to 0.15 mm.

[0084] In some embodiments, the passivation layer 51 includes chromium oxide, nickel oxide, or aluminum oxide. For example, the passivation layer 51 is formed on the connecting piece 50 by chemical plating, electroplating, chemical vapor deposition, or physical vapor deposition. Chromium oxide has good chemical stability and good corrosion resistance, and can resist the erosion of chemical substances such as the electrolyte inside the secondary battery 100, thereby improving the stability of the connecting piece 50. Nickel oxide has strong stability, and can maintain stable chemical properties in the working environment of the secondary battery 100. It is not easy to react chemically with other substances inside the secondary battery 100, which can reduce the service life of the connecting piece 50. In addition, nickel oxide has good adhesion, can be firmly attached to the surface of the connecting piece 50, and improves the bonding strength between the connecting piece 50 and the sealing member 40. Aluminum oxide has stable chemical properties and excellent chemical corrosion resistance. It can resist the erosion of the electrolyte well, provide reliable protection for the connecting piece 50, and extend the service life of the connecting piece 50. Aluminum oxide also has good high temperature resistance, which can reduce the impact of welding on the passivation layer 51 and improve the performance stability of the passivation layer 51.

[0085] In some other embodiments, the entire outer surface of the connecting piece 50 is provided with a passivation layer 51, so that the passivation layer 51 can wrap the entire connecting piece 50, which can further reduce the corrosion of the connecting piece 50.

[0086] In the embodiment of the present application, the sealing member 40 is made of hot melt adhesive and / or pressure sensitive adhesive, and can be connected to the first wall portion 12 by hot pressing during installation, which is simple and convenient to operate and is beneficial to improving the production efficiency of the secondary battery 100.

[0087] In some embodiments, please refer to Fig.10 and Fig.11 The sealing member 40 includes a first insulating layer 41 and a second insulating layer 42 which are stacked. The first insulating layer 41 is bonded between the second insulating layer 42 and the connecting piece 50. The melting point of the first insulating layer 41 is T1, 100°C≤T1≤130°C. Any value between 100°C and 130°C can be selected, for example, 100°C, 105°C, 110°C, 115°C, 120°C, 125°C or 130°C.

[0088] The melting point of the second insulating layer 42 is T2, 140℃≤T2≤190℃, and any value between 140℃ and 190℃ can be selected, for example, 140℃, 145℃, 150℃, 155℃, 160℃, 165℃, 170℃, 175℃, 180℃, 185℃ or 190℃, etc.

[0089] During use, the secondary battery 100 may have safety hazards due to internal high temperature and high pressure. For example, when the secondary battery 100 is short-circuited, overcharged or locally overheated, the internal temperature of the secondary battery 100 rises and the gas pressure increases. Since the first insulating layer 41 has a low melting point, it will melt first in the temperature range of 100°C to 130°C, thereby forming a pressure relief channel connecting the inside of the shell 10 with the outside world, which can effectively alleviate thermal runaway and reduce the risk of fire or explosion of the secondary battery 100. In addition, the second insulating layer 42 has a higher melting point. When the first insulating layer 41 melts, the second insulating layer 42 can still remain in a solid state, thereby insulating the pole 30 from the shell 10, thereby reducing the occurrence of short circuits.

[0090] In addition, the channel formed after the first insulating layer 41 is melted can be used as an initial pressure relief path, so that the internal pressure of the secondary battery 100 is initially released. At this time, the second insulating layer 42 remains solid. For example, in the initial pressure relief stage, the thermal runaway of the secondary battery 100 is alleviated. At this time, the seal 40 is still relatively intact. A simple adjustment of the seal 40 can seal the secondary battery 100 again, which is conducive to the reuse of the seal 40.

[0091] In some other embodiments, please refer to Fig.12 and Fig.13 The seal 40 further includes a third insulating layer 43. The third insulating layer 43 is bonded between the second insulating layer 42 and the flange portion 32 along the direction from the first wall portion 12 to the connecting piece 50. The melting point of the third insulating layer 43 is T3, 100°C≤T3≤130°C, and any value between 100°C and 130°C can be selected, such as 100°C, 105°C, 110°C, 115°C, 120°C, 125°C or 130°C. Under normal operating temperature, the three insulating layers are all in a solid state, which can provide a thicker insulation and sealing barrier. On the one hand, it can improve the bonding strength between the connecting piece 50 and the pole 30. On the other hand, it can enhance the sealing effect of the seal 40 on the electrolyte inside the secondary battery 100 and the external moisture and gas, thereby reducing the risk of leakage.

[0092] When the internal temperature of the secondary battery 100 increases, the first insulating layer 41 and the third insulating layer 43 melt, providing more pressure relief channels for the gas inside the secondary battery 100, which is conducive to timely response to the abnormal increase in the temperature of the secondary battery 100, further alleviating thermal runaway, and reducing the risk of fire or explosion of the secondary battery 100.

[0093] As for the material of the seal 40, the first insulating layer 41, the second insulating layer 42 and the third insulating layer 43 are independently selected from at least one of polypropylene (PP), low-density polyethylene (LDPE), high-density polyethylene (HDPE), linear low-density polyethylene (LLDPE), oriented polypropylene (OPP), polystyrene (PS), polyvinyl chloride (PVC), polyethylene terephthalate (PET), polyamide (PA) or phenolic resin (PF). Each material has good chemical stability, can withstand the erosion of the electrolyte, reduce the damage of the seal 40 caused by chemical corrosion, and thus improve the sealing of the seal 40. In addition, each material has low permeability to gas and liquid, which can reduce the leakage of the internal electrolyte and prevent external air, moisture, etc. from entering the interior of the secondary battery 100, which is conducive to maintaining the normal operation of the secondary battery 100.

[0094] As for the adjustment of the melting point of the seal 40, it can be adjusted by blending and modification, and polymer materials with different melting points are blended, and the melting point of the material is changed by the interaction between polymers. For example, blending PP with a high melting point with LDPE with a low melting point can reduce the melting point of PP to a certain extent, while improving the heat resistance of LDPE. It can also be adjusted by adding plasticizers. The plasticizer molecules are inserted between the polymer molecular chains to weaken the forces between the molecular chains, making the molecular chains easier to move, thereby reducing the melting point of the material. For example, adding phthalate plasticizers to PVC can significantly reduce the melting point and hardness of PVC and improve its flexibility. It can also be adjusted by chemical modification, and new groups are introduced into the polymer molecular chain or the structure of the molecular chain is changed through chemical reactions, thereby changing the melting point of the material. For example, copolymerization modification of PET and introduction of a third monomer can destroy the regularity of the PET molecular chain, reduce its crystallinity, and thus reduce the melting point. In addition, it can be adjusted by changing the processing technology. Different processing technologies such as extrusion, injection molding, blow molding, etc., as well as parameters such as temperature, pressure, cooling rate, etc. during the processing, will affect the crystallization behavior and morphology of the polymer, and then affect its melting point. For example, rapid cooling can make the polymer form a smaller crystal size and reduce the melting point of the material.

[0095] Regarding the thickness of the seal 40, in some embodiments, please refer to the figure, along the direction from the first wall portion 12 to the connecting piece 50, the thickness of the seal 40 is H, 0.05mm≤H≤1mm, and any value between 0.05mm and 1mm can be selected, for example, 0.05mm, 0.06mm, 0.07mm, 0.08mm, 0.09mm, 0.1mm, 0.2mm, 0.3mm, 0.4mm, 0.5mm, 0.6mm, 0.7mm, 0.8mm, 0.9mm or 1mm, etc.

[0096] Under normal temperature conditions, this thickness range enables the seal 40 to have a good insulation effect, effectively reducing the electrical short circuit between the connecting piece 50 and the flange portion 32. It can also form an effective barrier to the electrolyte inside the secondary battery 100 and the external water vapor, improve the connection stability between the pole 30 and the shell 10, and improve the sealing of the secondary battery 100. When the temperature rises, the first insulating layer 41 and the third insulating layer 43 will melt according to their melting point characteristics, thereby forming a better pressure relief channel, and quickly responding to the abnormal increase in the temperature of the secondary battery 100. At the same time, the second insulating layer 42 remains solid at a certain temperature stage, so that a better insulation effect is formed between the pole 30 and the shell 10 / connecting piece 50.

[0097] Furthermore, 0.1mm≤H≤0.3mm, within this thickness range, the thermal response of each insulating layer at high temperature is more precise, which on the one hand improves the connection stability between the pole 30 and the connecting piece 50, and on the other hand can promptly respond to the abnormal increase of the stability of the secondary battery 100, thereby reducing material costs and reducing energy density losses.

[0098] In some embodiments, the thickness of the first insulating layer 41 is H1, the thickness of the second insulating layer 42 is H2, and 1 / 3≤H1 / H2≤2. When the temperature rises, the first insulating layer 41 forms a better pressure relief channel to reduce the risk of fire or explosion of the secondary battery 100. At the same time, the second insulating layer 42 also has sufficient thickness to maintain the subsequent insulation effect and reduce the short circuit of the secondary battery 100. Based on the same inventive concept, the thickness of the third insulating layer 43 is H3, and 1 / 3≤H3 / H2≤2.

[0099] As for the thickness of the connecting sheet 50, along the direction from the first wall surface 121 to the second wall surface 122, the thickness of the connecting sheet 50 is H4, 0.04mm≤H4≤0.5mm, and any value between 0.04mm and 0.5mm can be selected, for example, 0.04mm, 0.05mm, 0.06mm, 0.07mm, 0.08mm, 0.09mm, 0.1mm, 0.15mm, 0.2mm, 0.25mm, 0.3mm, 0.35mm, 0.4mm, 0.45mm or 0.5mm, etc. This makes the connecting sheet 50 have a better structural strength, reduces the deformation of the connecting sheet 50 during the assembly and vibration of the secondary battery 100, and within the above thickness range, during welding, the influence on the passivation layer 51 can be reduced, which can facilitate the welding of the connecting sheet 50 and the housing 10, and is conducive to improving the connection strength between the connecting sheet 50 and the housing 10. If the thickness is small, for example, less than 0.04 mm, the passivation layer 51 may be affected during welding, thereby weakening the bonding strength between the seal 40 and the passivation layer 51 and the seal 40. If the thickness is large, for example, greater than 0.5 mm, a large space will be occupied, resulting in a loss of energy density of the secondary battery 100.

[0100] Furthermore, 0.1 mm ≤ H4 ≤ 0.3 mm can further reduce the impact on the passivation layer 51 during welding, and reduce the impact on the energy density of the secondary battery 100 .

[0101] In some embodiments, the diameter of the column 31 is R, 0.1mm≤R≤0.6mm, and any value between 0.1mm and 0.6mm can be selected, for example, 0.1mm, 0.2mm, 0.3mm, 0.4mm, 0.5mm or 0.6mm. In the embodiment of the present application, a structure in which the seal 40 is bonded to the pole 30 is adopted. Since the adhesive pole 30 will not cause a large deformation to the column 31 and the flange portion 32 of the pole 30, a relatively small diameter of the column 31 can be adopted. Compared with the riveted pole 30, the adhesive method reduces the mechanical stress and deformation generated during the riveting process, so that the pole 30 can maintain a more precise size and shape, which is conducive to improving the structural integrity of the pole 30 in the case of a small diameter. In addition, the diameter range of the column 31 from 0.1mm to 0.6mm provides more flexibility for the structural design of the secondary battery 100. The smaller diameter of the column 31 can make the internal layout of the battery more compact, improve the space utilization, and help to achieve the miniaturization design requirements of the secondary battery 100.

[0102] Furthermore, in the present application, a single-layer flange portion is bonded to one side of the first wall portion, which is beneficial for controlling the surface of the passivation layer, reducing scratches and oil stains on the passivation layer, and thereby improving the bonding effect.

[0103] 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.

[0104] Example 1

[0105] Preparation of positive electrode:

[0106] 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) were mixed in a mass ratio of 94:3:3, N-methylpyrrolidone (NMP) was added as a solvent, and a positive electrode slurry with a solid content of 75wt% was prepared, and the mixture was stirred evenly in a vacuum mixer. An aluminum foil with a thickness of 8μm and a length of 1000mm was selected as the positive electrode current collector, and the positive electrode slurry was evenly coated on one surface of the positive electrode current collector aluminum foil, and dried at 110°C to obtain a positive electrode sheet with a single-sided positive electrode active material layer. Afterwards, the above steps were repeated on the other surface of the aluminum foil to obtain a positive electrode sheet with a double-sided positive electrode active material layer.

[0107] Preparation of negative electrode sheet:

[0108] The negative electrode active material graphite powder, silicon powder, conductive carbon black (Super P), and binder styrene-acrylic rubber (SD-3) are mixed in a weight ratio of 89.5:8:1:1.5, 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 5μm and a length of 1050mm is selected as the negative electrode current collector, and the negative electrode slurry is evenly coated on one surface of the negative electrode current collector copper foil, 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.

[0109] Preparation of isolation membrane:

[0110] Polyethylene is selected as a 7 μm substrate layer, and polyvinylidene fluoride is selected as an adhesive layer. An alumina ceramic layer with a thickness of 2 μm is arranged on the side of the adhesive layer away from the substrate layer to prepare a porous isolation membrane.

[0111] Preparation of electrolyte:

[0112] 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.

[0113] Preparation of lithium-ion secondary batteries:

[0114] The positive electrode sheet is welded to the positive electrode ear of the aluminum sheet, and the negative electrode sheet is welded to the negative electrode ear of the nickel sheet. The separator, positive electrode sheet, separator, and negative electrode sheet are stacked in order and wound to obtain an electrode assembly. The electrode assembly is placed in a steel shell, and the shell has a first wall portion, and the first wall portion includes a first wall surface facing away from the shell accommodating cavity and a second wall surface facing the shell accommodating cavity. The connecting piece is surface treated to form a passivation layer of chromium oxide, and a seal made of polypropylene is used to bond the flange portion of the pole to the passivation layer of the connecting piece, and the surface of the connecting piece facing away from the passivation layer is welded to the second wall surface, and the welding width W1 between the connecting piece and the passivation layer is 0.02mm. The width of the connecting piece is 1.8mm, and the welding penetration does not reach the passivation layer. The width of the non-welding area of ​​the passivation layer is 1.8mm, wherein the column of the pole extends to the second through hole of the connecting piece and the first through hole of the first wall. The thickness of the seal is H is 0.1mm. After the processes of packaging, formation, capacity testing, voltage internal resistance testing, etc., a lithium-ion secondary battery is obtained.

[0115] Different from Example 1, the relevant parameters in Examples 2 to 36 and Comparative Example 1 are shown in Table 1 below. Among them, in Comparative Example 1, the connecting piece is not provided with a passivation layer. In Example 25, the connecting piece is provided on the second wall surface, and the connecting piece is also provided with a convex portion, and the convex portion is welded to the inner wall of the first through hole. In Example 26, the connecting piece is provided on the first wall surface, and the connecting piece and the first wall portion are welded from the side. In Example 27, the width of the connecting piece is 1.9 mm, the welding penetration does not reach the passivation layer, and the width of the non-welding area of ​​the passivation layer is 1.9 mm. In Examples 10 to 12 and Examples 28 to 36, the welding penetration reaches the passivation layer, and then a welding area is formed on the passivation layer.

[0116] Peel strength test: According to GB / T 2792-2014 "Test method for peel strength of adhesive tape", the peel strength between the pole and the first wall is tested using a high-speed rail tensile tester. The process is as follows: discharge the lithium-ion secondary battery to 0V, then disassemble the lithium-ion secondary battery, remove the connecting piece, seal and pole bonding structure as a whole, wipe the electrolyte on the surface with dust-free paper, use a multi-functional tensile tester, clamp the connecting piece at one end and the flange of the pole at the other end (special clamping is required), and the tensile speed is usually 50mm / min. Test, when the sample is separated, record the peel strength N / mm at separation.

[0117] Table 1

[0118]

[0119]

[0120] According to the above Table 1, combined with Examples 1 to 26 and Comparative Example 1, it can be seen that when a passivation layer is provided on the connecting sheet and the seal is bonded through the passivation layer, the bonding strength can be effectively improved. The passivation layer can improve the interfacial bonding force between the connecting sheet and the seal, and can enable the seal to better interact with the surface of the connecting sheet during the curing or bonding process to form a stronger bond. Furthermore, the passivation layer is conducive to better fitting of the seal and the connecting sheet, so that the seal can be more tightly bonded to the passivation layer, reducing the risk of gaps or leakage at the seal, thereby enhancing the sealing.

[0121] In combination with Examples 1 to 12, in Examples 1 to 11, the bonding strength is relatively high. In Example 12, the welding width is relatively large, which will cause excessive heat generated during the welding process to be transferred to the connecting piece, forming a larger heat radiation area, which may cause damage to the passivation layer, or even directly cause the welding area to extend to the passivation layer, causing damage to the passivation layer, thereby causing the bonding strength between the seal and the passivation layer 51 to be weakened. In Example 1, the welding width is relatively small, so that the bonding strength between the connecting piece and the shell is weakened, which may cause looseness between the connecting piece and the shell, also affecting the sealing. In combination with Examples 2 to 11, 0.03mm≤W1≤0.3mm can be selected.

[0122] In Examples 4 to 7, the bonding strength is relatively high and the impact on the structural strength of the connecting piece and the shell is relatively small. Considering the need to improve the bonding strength between the connecting piece and the pole while improving the bonding strength between the connecting piece and the shell, in the embodiments of the present application, 0.08mm≤W1≤0.15mm is selected.

[0123] In combination with Examples 13 to 24, Examples 14 to 24 and Example 7 have high bonding strength. In Example 13, the thickness of the seal is small, it is difficult to provide sufficient bonding force, and it may be difficult to form a pressure relief channel. In Example 24, the thickness of the seal is large and the material cost is high, which affects the energy density of the battery, and the bonding strength is similar to that of Example 23. Considering the improvement of bonding strength and the reduction of energy density loss, 0.05mm≤H≤1mm can be selected.

[0124] In Examples 16 to 18 and Example 7, the bonding strength is greater than that of Examples 13 to 15, and the bonding strength is not much different from that of Examples 19 to 24. In Examples 16 to 18 and Example 7, the material cost is lower and the impact on energy density is also smaller. In the embodiments of the present application, 0.1 mm ≤ H ≤ 0.3 mm may be preferred.

[0125] In Examples 25 and 26, convex portion welding and side welding are respectively adopted, which can also reduce the influence of welding on the passivation layer, thereby improving the bonding strength between the connecting piece and the pole.

[0126] In combination with Examples 27 to 36 and Example 9, in Example 36, the area of ​​the non-welding zone of the passivation layer is small, the protective function of the passivation layer is weakened, and the passivation layer is easily corroded. And the excessively large welding area will also affect the bonding strength between the seal and the connecting piece, resulting in a weakening of the bonding strength between the seal and the connecting piece, which may cause the stability of the internal structure of the secondary battery to decrease. In Example 27, the non-welding area is large, and the excessively large non-welding area means that the surrounding area that can be effectively welded is relatively small. In order to ensure the welding quality, it may be necessary to control higher precision and more accurate energy output, which will reduce welding efficiency, increase production time and cost, and its peel strength is also similar to that of Example 9. In addition, the larger non-welding area means that the diameter of the connecting piece is larger, which may affect the thickness of the secondary battery and cause the energy density loss of the secondary battery. Therefore, in the embodiment of the present application, it can be selected that the width of the non-welding area is 0.6mm≤W2≤1.8mm.

[0127] 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, characterized in that: include: A shell body enclosing a receiving cavity, the shell body comprising a first wall portion, the first wall portion being provided with a first through hole communicating with the receiving cavity; A connecting sheet, disposed on the first wall portion, the connecting sheet being provided with a second through hole, the second through hole being communicated with the first through hole, and a passivation layer being provided on a surface of the connecting sheet facing away from the first wall portion; A pole, comprising a column and a flange portion, wherein the flange portion is arranged on a side of the connecting piece away from the first wall portion, the column is connected to the flange portion, and the column portion is arranged in the first through hole and the second through hole; A sealing member is bonded between the passivation layer and the flange portion.

2. The secondary battery according to claim 1, characterized in that: The first wall portion includes a first wall surface facing away from the accommodating cavity and a second wall surface facing the accommodating cavity, and the connecting piece is welded to the second wall surface to form a first welding portion.

3. The secondary battery according to claim 2, characterized in that: Observed in the opposite direction of the first direction, the passivation layer includes a non-welding area, and along the second direction, the width of the non-welding area is W2, 0.6 mm≤W2≤1.8 mm; The first direction is the direction from the first wall surface to the second wall surface, and the second direction is the direction from the outer diameter to the inner diameter of the connecting piece.

4. The secondary battery according to claim 2, characterized in that: When viewed along the first direction, the first welding portion is arranged around the first through hole, and along the second direction, the width of the first welding portion is W1, 0.03 mm≤W1≤0.3 mm; The first direction is the direction from the first wall surface to the second wall surface, and the second direction is the direction from the outer diameter to the inner diameter of the connecting piece.

5. The secondary battery according to claim 4, characterized in that: 0.08mm≤W1≤0.15mm.

6. The secondary battery according to claim 1, characterized in that: The first wall portion includes a first wall surface facing away from the accommodating cavity and a second wall surface facing the accommodating cavity; The connecting piece is arranged on the second wall surface, a convex portion is protruded on the surface of the connecting piece away from the sealing member, the second through hole passes through the convex portion, the convex portion is at least partially arranged on the first through hole, and the convex portion is welded to the inner wall of the first through hole.

7. The secondary battery according to claim 1, characterized in that: The first wall portion includes a first wall surface away from the accommodating cavity and a second wall surface facing the accommodating cavity, and the connecting piece is arranged on the first wall surface; the wall surface of the connecting piece facing the second through hole is welded to the inner wall of the first through hole.

8. The secondary battery according to any one of claims 1 to 7, characterized in that: The passivation layer includes chromium oxide, nickel oxide or aluminum oxide.

9. The secondary battery according to claim 1, characterized in that: The entire outer surface of the connecting sheet is provided with the passivation layer.

10. The secondary battery according to claim 1, characterized in that: The sealing element comprises hot melt adhesive and / or pressure sensitive adhesive.

11. The secondary battery according to claim 1, characterized in that: The sealing member comprises a first insulating layer and a second insulating layer which are stacked; The first insulating layer is bonded between the second insulating layer and the connecting sheet, the melting point of the first insulating layer is T1, 100°C≤T1≤130°C, and the melting point of the second insulating layer is T2, 140°C≤T2≤190°C.

12. The secondary battery according to claim 11, characterized in that: The seal also includes a third insulating layer, which is bonded between the second insulating layer and the flange portion along the direction from the first wall portion to the connecting piece. The melting point of the third insulating layer is T3, 100°C≤T3≤130°C.

13. The secondary battery according to claim 12, characterized in that: The first insulating layer, the second insulating layer and the third insulating layer are each independently selected from at least one of PP, LDPE, HDPE, LLDPE, OPP, PS, PVC, PET, PA or PF.

14. The secondary battery according to claim 1, characterized in that: Along the direction from the first wall portion to the connecting piece, the thickness of the sealing member is H, and 0.05 mm ≤ H ≤ 1 mm.

15. The secondary battery according to claim 14, characterized in that: 0.1mm≤H≤0.3mm.

16. The secondary battery according to claim 1, characterized in that: Along the direction from the first wall surface to the second wall surface, the thickness of the connecting piece is H4, 0.04mm≤H4≤0.5mm.

17. The secondary battery according to claim 16, characterized in that: 0.1mm≤H4≤0.3mm.

18. The secondary battery according to claim 1, characterized in that: The diameter of the column is R, 0.1mm≤R≤0.6mm.

19. An electronic device, characterized in that: The invention comprises the secondary battery according to any one of claims 1 to 18.

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