Secondary battery and electronic device

Abstract

Disclosed in the present application are a secondary battery and an electronic device. The secondary battery comprises a housing, a connecting tab, a pole, and a sealing member. The housing encloses an accommodating cavity; the housing comprises a first wall portion, the first wall portion being provided with a first through hole in communication with the accommodating cavity. The connecting tab is arranged on the first wall portion; the connecting tab is provided with a second through hole in communication with the first through hole, and a passivation layer is provided on the side of the connecting tab facing away from the first wall portion. The pole comprises a column body and a flange portion, wherein the flange portion is arranged on the side of the connecting tab facing away from the first wall portion, and the column body is connected to the flange portion, part of the column body being arranged in the first through hole and the second through hole. The sealing member is bonded between the passivation layer and the flange portion. The bonding strength between the connecting tab and the housing can be improved, and the sealing performance of the secondary battery can be improved. In addition, the passivation layer being provided on the connecting tab enables the improvement of corrosion resistance, sealing performance, adhesion and insulation in a single step, thereby simplifying the production process of the secondary battery.

Description

Secondary batteries and electronic devices

[0001] Cross-reference of related applications

[0002] This application claims priority to Chinese Patent Application No. 202510360557.4, filed on March 25, 2025, entitled “Secondary Battery and Electronic Device”, the entire contents of which are incorporated herein by reference.

[0003] Technical Field

[0004] This application relates to the field of battery technology, and in particular to a secondary battery and electronic device. Background Technology

[0005] With the rapid development of new energy technologies, batteries have been widely used in mobile phones, laptops, electric vehicles, and other fields. For hard-shell batteries, polarity is typically indicated by terminals. During the terminal installation process, the terminals are usually riveted to form flanges, and a seal is compressed between the terminal and the casing to achieve a seal. However, the riveted terminal structure has poor stability and is prone to poor sealing. Summary of the Invention

[0006] This application aims to provide a secondary battery and electronic device that can improve the sealing performance of the secondary battery.

[0007] In one aspect, this application proposes a secondary battery, including a casing, a connecting piece, an electrode post, and a sealing element. The casing encloses a receiving cavity and includes a first wall portion with a first through hole communicating with the receiving cavity. The connecting piece is disposed on the first wall portion and has a second through hole communicating with the first through hole. A passivation layer is disposed on the side of the connecting piece facing away from the first wall portion. The electrode post includes a column and a flange portion. The flange portion is disposed on the side of the connecting piece facing away from the first wall portion, and the column is connected to the flange portion. The column portion is disposed in the first and second through holes. The sealing element is bonded between the passivation layer and the flange portion.

[0008] In the above technical solution, the passivation layer improves the interfacial bonding force between the connecting piece and the seal, enabling the seal to interact better with the surface of the connecting piece during curing or bonding, forming a stronger bond. This improves the reliability of the entire connection structure and reduces the risk of seal detachment or loosening due to vibration, thermal cycling, or other factors. Furthermore, the passivation layer facilitates better fit between the seal and the connecting piece, allowing the seal to adhere more tightly to the passivation layer, reducing the risk of gaps or leaks at the seal, thus enhancing sealing performance and further reducing electrolyte leakage and the entry of external impurities into the secondary battery. Additionally, the passivation layer provides isolation and protection, reducing direct contact between the connecting piece and the electrolyte, minimizing corrosion or oxidation of the connecting piece surface, thereby extending its service life and improving its mechanical stability. Moreover, the passivation layer itself has insulating properties, further improving the insulation between the connecting piece and the electrode flange, which helps reduce short circuits within the secondary battery and enhances its safety. In addition, by setting the passivation layer on the connecting piece, the improvement of corrosion resistance, sealing performance, adhesion and insulation can be integrated into one step, simplifying the production process of secondary batteries.

[0009] In some embodiments, the first wall portion includes a first wall surface facing away from the receiving cavity and a second wall surface facing the receiving cavity. The connecting piece is welded to the second wall surface to form a first weld portion. The connecting piece itself can be used as a barrier to block the impact of welding spatter and sparks on the passivation layer. At the same time, it also reduces the impact of the high-temperature oxidation environment on the passivation layer, which is beneficial to protecting the integrity of the passivation layer between the connecting piece and the seal. This allows the passivation layer to provide a better sealing bonding platform, which on the one hand improves the connection stability between the terminal and the housing, and on the other hand improves the sealing performance of the secondary battery.

[0010] In some embodiments, viewed from the opposite direction of the first direction, the passivation layer between the connecting piece and the seal includes a non-welded area. Along the second direction, the width of the non-welded area is W2, where 0.6mm ≤ W2 ≤ 1.8mm. This allows the passivation layer to maintain good protection, insulation, and improved adhesion, thereby enhancing the sealing performance of the secondary battery. The first direction is from the first wall surface to the second wall surface, and the second direction is from the outer diameter to the inner diameter of the connecting piece.

[0011] In some embodiments, when viewed along the first direction, the first welded portion is arranged around the first through hole, and along the second direction, the width of the first welded portion is W1, 0.03mm≤W1≤0.3mm, which allows the connecting piece and the housing to have sufficient welding area, reduces the impact on the passivation layer between the connecting piece and the seal, and allows the connecting piece and the housing to be more firmly bonded. This is beneficial for withstanding various stresses generated by the secondary battery during charging and discharging, and improves the stability of the secondary battery structure and the reliability of the electrical connection.

[0012] In some embodiments, 0.08mm≤W1≤0.15mm, within which the first weld portion can provide a more suitable bonding area, further enhancing the welding strength between the connecting piece and the first wall of the housing.

[0013] In some embodiments, the first wall portion includes a first wall surface facing away from the receiving cavity and a second wall surface facing the receiving cavity. A connecting piece is disposed on the second wall surface, and a protrusion is provided on the surface of the connecting piece facing away from the seal. A second through hole penetrates the protrusion, and the protrusion is at least partially disposed in the first through hole. The protrusion is welded to the inner wall of the first through hole. The provision of the protrusion provides a more easily operable part for welding, facilitates the welding of the connecting piece to the housing, reduces the thermal impact on other parts of the connecting piece and the housing during the welding process, improves the performance of the connecting piece and the integrity of the housing, and also helps to improve welding efficiency.

[0014] In some embodiments, the first wall portion includes a first wall surface facing away from the receiving cavity and a second wall surface facing the receiving cavity, with a connecting piece disposed 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. Welding is performed from the side, and the welding heat source acts directly on the inner walls of the second and first through holes. The welding heat is mainly conducted along the inner walls of the second and first through holes, thereby reducing the amount of heat received by the passivation layer area between the connecting piece and the seal, and lowering the risk of damage to the passivation layer due to overheating.

[0015] In some embodiments, the passivation layer comprises chromium oxide, nickel oxide, or aluminum oxide, which has better corrosion resistance and high temperature resistance, and can reduce electrolyte corrosion and the impact of welding on the passivation layer.

[0016] In some embodiments, a passivation layer is provided on the entire outer surface of the connecting piece to further protect the connecting piece and reduce corrosion.

[0017] In some embodiments, the sealant includes hot melt adhesive and / or pressure-sensitive adhesive, and can be installed by hot-pressing the connecting piece to the first wall, which is simple and convenient to operate and helps to improve the production efficiency of secondary batteries.

[0018] In some embodiments, the sealing element includes a first insulating layer and a second insulating layer stacked together. The first insulating layer is bonded between the second insulating layer and the connecting piece. The melting point of the first insulating layer is T1, which is 100℃≤T1≤130℃ and can be any value from 100℃ to 130℃, such as 100℃, 105℃, 110℃, 115℃, 120℃, 125℃, or 130℃. The melting point of the second insulating layer is T2, which is 140℃≤T2≤190℃ and can be any value from 140℃ to 190℃, such as 140℃, 145℃, 150℃, 155℃, 160℃, 165℃, 170℃, 175℃, 180℃, 185℃, or 190℃. The first insulating layer has a low melting point, melting first in the temperature range of 100℃ to 130℃, thus forming a pressure relief channel connecting the inside of the casing with the outside, effectively mitigating thermal runaway and reducing the risk of secondary battery fire or explosion. Furthermore, the second insulating layer has a higher melting point; while the first insulating layer melts, the second insulating layer remains solid, thus insulating the terminals from the casing and reducing the occurrence of short circuits.

[0019] In some embodiments, the seal further includes a third insulating layer. Along the direction from the first wall portion to the connecting piece, the third insulating layer is bonded between the second insulating layer and the flange portion. The melting point of the third insulating layer is T3, 100℃≤T3≤130℃. Under normal operating temperature, all three insulating layers are in a solid state, providing a thicker insulation and sealing barrier, and improving the adhesion strength between the connecting piece and the electrode post. When the internal temperature of the secondary battery rises, the first and third insulating layers melt, providing more pressure relief channels for the gas inside the secondary battery. This facilitates timely response to abnormal temperature increases in the secondary battery, further mitigating thermal runaway and reducing the risk of fire or explosion of the secondary battery.

[0020] In some embodiments, 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. Each material exhibits good chemical stability, resisting electrolyte corrosion and reducing damage to the seals due to chemical corrosion, thereby improving the sealing performance. Furthermore, each material has low permeability to gases and liquids, reducing internal electrolyte leakage and preventing external air and moisture from entering the secondary battery, thus contributing to the normal operation of the secondary battery.

[0021] In some embodiments, the thickness of the seal is H, 0.05 mm ≤ H ≤ 1 mm, along the direction from the first wall to the connecting piece. Under normal temperature conditions, this thickness range allows the seal to provide good insulation. When the temperature rises, the first and third insulating layers melt according to their melting point characteristics, thereby forming a better pressure relief channel and rapidly responding to abnormal increases in the secondary battery temperature.

[0022] In some embodiments, 0.1mm≤H≤0.3mm allows for more precise thermal response of each insulating layer at high temperatures, which improves the connection stability between the electrode and the connecting piece and enables timely response to abnormal increases in the temperature of the secondary battery.

[0023] In some embodiments, the thickness of the connecting piece along the direction from the first wall surface to the second wall surface is H4, where 0.04mm ≤ H4 ≤ 0.5mm. This gives the connecting piece better structural strength, reduces deformation during secondary battery assembly and vibration, and minimizes the impact of welding on the passivation layer between the connecting piece and the seal. It also facilitates welding between the connecting piece and the housing, improving the connection strength between them. Furthermore, a thickness of 0.1mm ≤ H4 ≤ 0.3mm further reduces the impact of welding on the passivation layer and the energy density of the secondary battery.

[0024] In some embodiments, the diameter of the post is R, 0.1mm≤R≤0.6mm. Compared with riveted posts, the adhesive bonding method reduces the mechanical stress and deformation generated during the riveting process, allowing the post to maintain a more precise size and shape, which is beneficial to improving the structural integrity of the post in the case of small diameter.

[0025] Secondly, this application also proposes an electronic device including a secondary battery as described in any of the embodiments of the first aspect above.

[0026] Additional aspects and advantages of the embodiments of this application will be described, shown, or illustrated in part by way of implementation of the embodiments of this application in the following description. Attached Figure Description

[0027] One or more embodiments are illustrated by way of example with reference to the accompanying drawings, which are not intended to limit the embodiments, and elements having the same reference numerals in the drawings are designated as similar elements.

[0028] Figure 1 is a schematic diagram of the exploded structure of a secondary battery according to some embodiments of this application;

[0029] Figure 2 is a schematic diagram of the connection structure between the pole and the housing in some embodiments of this application;

[0030] Figure 3 is a schematic diagram of the connection structure between the pole and the housing in some embodiments of this application;

[0031] Figure 4 is a schematic diagram of the connection structure between the pole and the housing in some embodiments of this application;

[0032] Figure 5 is a schematic diagram of the passivation layer structure in some embodiments of this application;

[0033] Figure 6 is a schematic diagram of the passivation layer structure in some embodiments of this application;

[0034] Figure 7 is a schematic diagram of the connection structure between the pole and the housing in some embodiments of this application;

[0035] Figure 8 is a schematic diagram of the connection structure between the pole and the housing in some embodiments of this application;

[0036] Figure 9 is a schematic diagram of the connection structure between the pole and the housing in some embodiments of this application;

[0037] Figure 10 is a schematic diagram of the connection structure between the pole post and the housing in some embodiments of this application;

[0038] Figure 11 is a schematic diagram of the connection structure between the pole and the housing in some embodiments of this application;

[0039] Figure 12 is a schematic diagram of the connection structure between the pole and the housing in some embodiments of this application;

[0040] Figure 13 is a schematic diagram of the connection structure between the pole and the housing in some embodiments of this application;

[0041] Figure 14 is a schematic diagram of the structure of the seal in some embodiments of this application.

[0042] Explanation of reference numerals in the attached figures:

[0043] 100. Secondary batteries;

[0044] 10. Shell; 10a. Main body; 10b. Cover; 11. Receiving cavity; 12. First wall; 121. First wall surface; 122. Second wall surface; 13. First through hole;

[0045] 20. Electrode assembly;

[0046] 30. Pole post; 31. Column body; 32. Flange section;

[0047] 40. Seal; 41. First insulating layer; 42. Second insulating layer; 43. Third insulating layer; 44. Third through hole;

[0048] 50. Connecting piece; 51. Passivation layer; 52. Metal sheet; 53. Second through hole; 54. Protrusion;

[0049] 60. First welding section;

[0050] X, the first direction; Y, the second direction. Embodiments of the present invention

[0051] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly described below with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of this application, but not all embodiments.

[0052] In this application, the reference to "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment that is mutually exclusive with other embodiments.

[0053] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0054] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0055] The technical features involved in the different embodiments of this application described below can be combined with each other as long as they do not conflict with each other.

[0056] In one aspect, this application proposes a secondary battery 100. Referring to Figure 1, the secondary battery 100 includes a housing 10, an electrode assembly 20, a terminal post 30, a sealing element 40, and a connecting piece 50.

[0057] Referring to Figure 1, the housing 10 encloses a receiving cavity 11, which can accommodate the electrode assembly 20 and the electrolyte (not shown in the figure). The electrolyte wets the electrode assembly 20 in the receiving cavity 11, thereby causing an electrochemical reaction. In the embodiments of this application, the housing 10 can be formed by stamping a conductive metal layer. The thickness of the conductive metal layer can be set to 0.1 mm to 0.4 mm, so that the housing 10 has high stamping strength. The conductive metal layer can be made of conductive metal materials such as aluminum, steel, stainless steel, nickel, or copper, so that the housing 10 can lead out one polarity of the secondary battery 100, and the aforementioned electrode post 30 can lead out the other polarity. In some other embodiments, the housing 10 can also be made of soft-pack materials such as aluminum-plastic film or copper-plastic film, so that the housing 10 has better ductility.

[0058] The housing 10 can be square, trapezoidal, or cylindrical, etc. Taking a square housing 10 as an example, please refer to Figure 1. The housing 10 includes a main body 10a and a cover 10b. The main body 10a is provided with a cavity, and one end of the main body 10a is open, so that the electrode assembly 20 can be directly placed in the cavity through the open end. The cover 10b is connected to the main body 10a and covers the cavity, thereby forming a receiving cavity 11.

[0059] Referring to Figures 1 and 2, the housing 10 includes a first wall portion 12, which includes a first wall surface 121 facing away from the receiving cavity 11 and a second wall surface 122 facing the receiving cavity 11. The first wall portion 12 has a first through hole 13, which penetrates the first wall surface 121 and the second wall surface 122 and communicates with the receiving cavity 11. The aforementioned electrode post 30 can be disposed in the first through hole 13 for one polarity of the secondary battery 100.

[0060] Referring to Figure 1, the electrode assembly 20 is disposed in the receiving cavity 11 of the housing 10. The shape of the electrode assembly 20 can be configured to fit the housing 10 so as to make full use of the space of the receiving cavity 11 of the housing 10 and improve the energy density of the secondary battery 100.

[0061] The electrode assembly 20 includes a positive electrode (not shown), a negative electrode (not shown), and a separator (not shown). The positive electrode, separator, and negative electrode are stacked and wound together to form a wound electrode assembly 20. Alternatively, several positive electrode pieces and several negative electrode pieces are stacked alternately, with a separator between adjacent positive and negative electrode pieces to form a stacked electrode assembly 20.

[0062] The negative electrode of the electrode assembly 20 can be directly electrically connected to the housing 10, so that the housing 10 leads out the negative electrode. The positive electrode of the electrode assembly 20 can be electrically connected to the electrode post 30, so that the electrode post 30 leads out the positive electrode. In some other embodiments, the housing 10 can also lead out the positive electrode, and the electrode post 30 can lead out the negative electrode.

[0063] Referring to Figures 1 and 2, the electrode post 30 is disposed on the first wall portion 12. A portion of the electrode post 30 is electrically connected to the electrode assembly 20 within the receiving cavity 11, while the other portion protrudes from the first wall portion 12. For example, the electrode post 30 includes a connected column 31 and a flange portion 32. The flange portion 32 is wider and can be connected to the first wall portion 12. The wider flange portion 32 provides a larger connection area, which is beneficial to improving the connection strength between the housing 10 and the electrode post 30. The column 31 extends into the first through hole 13 to lead out one polarity of the secondary battery 100. For example, referring to Figure 2, the flange portion 32 can be connected to the first wall surface 121 of the first wall portion 12. In this case, the column 31 extends into the housing 10 through the first through hole 13, so that the column 31 can be electrically connected to the positive or negative electrode of the electrode assembly 20, while the flange portion 32 protrudes outside the housing 10 to lead out the positive or negative electrode of the secondary battery 100.

[0064] In some other embodiments, referring to FIG3, the flange 32 is connected to the second wall surface 122 of the first wall 12, the flange 32 is electrically connected to the positive or negative electrode of the electrode assembly 20, and the column 31 is exposed through the first through hole 13, thereby allowing the entire electrode 30 to lead out the positive or negative electrode of the secondary battery 100.

[0065] Referring to Figures 1 and 2, the seal 40 is bonded between the housing 10 and the flange 32, sealing the installation gap between them and thus sealing the first through hole 13. This reduces electrolyte leakage and minimizes the entry of external moisture into the housing 10. In the embodiments of this application, the polarity of the electrode post 30 is opposite to that of the housing 10. The seal 40 insulates the electrode post 30 from the housing 10, reducing the occurrence of short circuits.

[0066] Referring to Figures 1 and 2, the connecting piece 50 is disposed on the first wall portion 12. The connecting piece 50 is provided with a second through hole 53, which communicates with the first through hole 13. The column 31 of the pole post 30 can be disposed in the first through hole 13 and the second through hole 53, thereby leading out the polarity.

[0067] The seal 40 can be bonded between the connecting piece 50 and the flange 32 of the terminal 30. During the assembly of the secondary battery 100, the connecting piece 50 can be fixed to the first wall 12 first, and then the terminal 30 can be accurately installed in a predetermined position through the cooperation of the second through hole 53 and the first through hole 13, and then bonded and fixed using the seal 40, which helps to improve the production efficiency of the secondary battery 100. Furthermore, the overall connection of the terminal 30, the seal 40, and the connecting piece 50 can be removed from the housing 10 individually. For example, when the interior of the secondary battery 100 or the housing 10 is damaged, the overall connection of the terminal 30, the seal 40, and the connecting piece 50 can be removed and installed on the housing 10 of other secondary batteries 100, which helps to enhance the standardization and universality of the sealing structure of the terminal 30.

[0068] In the embodiments of this application, a passivation layer 51 is provided on the side of the connecting piece 50 facing away from the first wall portion 12. For example, the connecting piece 50 includes a metal sheet 52, and the passivation layer 51 is formed by surface treatment of the metal sheet 52. The sealing member 40 is bonded between the passivation layer 51 of the connecting piece 50 and the flange portion 32. The passivation layer 51 can reduce corrosion or oxidation of the surface of the connecting piece 50. The electrolyte inside the secondary battery 100 has a certain degree of corrosiveness, and the passivation layer 51 can play an isolating and protective role, reducing 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. Furthermore, 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 terminal post 30, which is beneficial to reducing short circuits inside the secondary battery 100 and improving the safety of the secondary battery 100.

[0069] Furthermore, the inventors of this application have discovered that the passivation layer 51 can improve the interfacial bonding force between the connecting piece 50 and the sealing element 40, enabling the sealing element 40 to better interact with the surface of the connecting piece 50 during curing or bonding, forming a stronger bond. For example, the formation process of the passivation layer 51 changes the chemical composition of the surface of the connecting piece 50, introducing some active groups. These groups can chemically react with corresponding groups in the material of the sealing element 40 to form chemical bonds, thereby enhancing the chemical bond bonding between the connecting piece 50 and the sealing element 40, thus improving the reliability of the entire connection structure and reducing the risk of the sealing element 40 falling off or the connection loosening due to factors such as vibration and thermal cycling. Moreover, the passivation layer 51 allows the sealing element 40 to adhere more tightly to the passivation layer 51, reducing the risk of gaps or leaks at the seal, thereby enhancing the sealing performance, further reducing electrolyte leakage and reducing the entry of external impurities into the secondary battery 100.

[0070] Furthermore, in the embodiments of this application, the passivation layer 51 is disposed on the connecting piece 50, which integrates improved corrosion resistance, improved sealing, improved adhesion, and improved insulation into one step, simplifying the manufacturing process of the secondary battery 100. Moreover, when the connecting piece 50 malfunctions and requires repair or replacement, the passivation layer 51 on the connecting piece 50 allows for easy disassembly and installation of the adhesive seal 40, minimizing the impact on the housing 10 and other components, thus facilitating later maintenance.

[0071] In some embodiments, referring to Figures 3 and 4, the connecting piece 50 is welded to the second wall surface 122 to form a first welded portion 60. After the connecting piece 50 is disposed 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 a portion of the first wall portion 12 and a portion of the connecting piece 50 rapidly melt to form the first welded portion 60. When the connecting piece 50 is welded to the first wall portion 12, the welding energy acts directly 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 impact of welding spatter and sparks on the passivation layer 51 between the connecting piece 50 and the seal 40. At the same time, it also reduces the impact of the high-temperature oxidation environment on the passivation layer 51, which is beneficial to protecting the integrity of the passivation layer 51. In this way, the passivation layer 51 provides a better bonding platform for the seal 40, which improves the connection stability between the electrode post 30 and the housing 10 on the one hand, and improves the sealing performance of the secondary battery 100 on the other hand.

[0072] Viewed from the opposite direction of the first direction X, the passivation layer 51 includes a non-welded area 511. Along the second direction Y, the width of the non-welded area 511 is W2, 0.6mm ≤ W2 ≤ 1.8mm, and can be any value from 0.6mm to 1.8mm, such as 0.6mm, 0.7mm, 0.8mm, 0.9mm, 1mm, 1.1mm, 1.2mm, 1.3mm, 1.4mm, 1.5mm, 1.6mm, 1.7mm, or 1.8mm. This effectively protects the passivation layer 51, and limiting the non-welded area 511 to 0.6mm to 1.8mm helps the passivation layer 51 maintain good protection, insulation, and improved adhesion. If the thickness is less than the lower limit, for example, less than 0.6 mm, the protective function of the passivation layer 51 is weakened, making it more susceptible to corrosion. Furthermore, a smaller non-welded area 511 will affect the bonding strength between the connecting piece 50 and the seal 40, weakening the bond strength between the seal 40 and the connecting piece 50, potentially reducing the stability of the internal structure of the secondary battery 100. Conversely, if the thickness is greater than the upper limit, for example, greater than 1.8 mm, an excessively large non-welded area 511 means a relatively smaller area available for effective welding. To ensure welding quality, higher precision and more accurate energy output may be required, reducing welding efficiency, increasing production time and cost, and potentially weakening the bond strength between the housing 10 and the connecting piece 50.

[0073] In some embodiments, referring to Figure 5, the non-welding area 511 includes a first non-welding area 511a and a second non-welding area 511b, and the width W2 of the non-welding area 511 is the same as the width W of the first non-welding area 511a. 21 Width W of the second non-welded area 511b 22 The sum of the values. In some other embodiments, referring 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.

[0074] In some embodiments, the width of the welding area 512 of the passivation layer 51 may be less than 0.2 mm to reduce the damage of the welding area 512 to the passivation layer 51.

[0075] Wherein, 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 has 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 can be the outer diameter of the connecting piece 50 itself or the outer diameter of the fitted circle it contains, and the inner diameter can be the inner diameter of the connecting piece 50 itself or the diameter of the fitted circle containing the second through hole 53. The second direction Y can be perpendicular to the first direction X.

[0076] In some embodiments, viewed along the first direction X, the first welded portion 60 is disposed around the first through hole 13. Along the second direction Y, the width of the first welded portion 60 is W1, 0.03mm ≤ W1 ≤ 0.3mm, and any value from 0.03mm to 0.3mm can be selected, such as 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. This allows for sufficient welding area between the connecting piece 50 and the housing 10, ensuring a firm bond between them. This helps withstand various stresses generated during the charging and discharging process of the secondary battery 100, improving the structural stability of the secondary battery 100 and the reliability of the electrical connection.

[0077] If the width of the welded part is small, for example, less than 0.03 mm, the welded joint area between the connecting piece 50 and the first wall part 12 of the housing 10 will be small, which cannot provide sufficient connection strength. During the use of the secondary battery 100, the connecting piece 50 may fall off the housing 10 due to external force or thermal stress, resulting in internal connection failure of the secondary battery 100 and affecting the performance of the secondary battery 100.

[0078] If the weld 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 housing 10, forming a large heat radiation area. This may cause a decrease in the mechanical properties of the connecting piece 50, such as damage to the passivation layer 51, or even directly cause the weld area to extend to the passivation layer 51, causing damage to the passivation layer 51. This will weaken the bonding strength between the seal 40 and the passivation layer 51, affecting the stability of the connection between the terminal post 30 and the housing 10, as well as the sealing performance of the secondary battery 100.

[0079] It is understandable that the connecting piece 50 has a second through hole 53, meaning the connecting piece 50 is annular. When the connecting piece 50 is welded to the first wall portion 12, the welding area surrounds the first through hole 13 and the second through hole 53, meaning the first welding portion 60 is also annular. The width of the first welding portion 60 is half the difference between the outer diameter and the inner diameter of the welding area. The outer diameter can be considered as the diameter of the welding area itself or the diameter of the fitted circle containing the welding area; the inner diameter can be determined similarly.

[0080] Furthermore, within the range of 0.08mm ≤ W1 ≤ 0.15mm, the first weld 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 housing 10. Compared to the lower limit of 0.03mm, the width of 0.08mm makes the stress distribution at the weld point more uniform, reducing the risk of cracking or detachment at the weld 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, compared to 0.3mm, is more conducive to precisely controlling the conduction of welding heat, which helps to reduce the impact on the passivation layer 51 of the connecting piece 50, and reduces problems such as excessive damage to the passivation layer 51 due to overheating and significant deformation of the housing 10.

[0081] In some embodiments, referring to Figures 7 and 8, a connecting piece 50 is disposed on the second wall surface 122. A protrusion 54 protrudes from the surface of the connecting piece 50 opposite to the sealing member 40. A second through hole 53 penetrates the protrusion 54. The protrusion 54 is at least partially disposed in the first through hole 13, and the protrusion 54 is welded to the inner wall of the first through hole 13. For example, laser penetration welding can be performed directly on the first wall portion 121 of the first wall portion 12 to fix the connecting piece 50 to the first wall portion 12.

[0082] Welding the protrusion 54 to the inner wall of the first through hole 13 makes the connection between the two more solid, thereby effectively improving the connection strength between the connecting piece 50 and the housing 10. For example, when the secondary battery 100 is subjected to external impact, vibration or thermal stress generated during charging and discharging, the connecting piece 50 can be reduced from falling off the housing 10, thus improving the stability of the secondary battery 100 structure.

[0083] Furthermore, the protrusion 54 provides a more convenient location for welding. Being further away from the passivation layer 51 of the connecting piece 50, welding the protrusion 54 to the inner wall of the first through hole 13 during welding makes it easier to control the welding position and quality compared to welding other parts of the connecting piece 50. Laser welding processes can more precisely target the contact area between the protrusion 54 and the inner wall of the first through hole 13, reducing the thermal impact on the passivation layer 51 and the housing 10 during welding, improving the performance of the connecting piece 50 and the integrity of the housing 10, while also contributing to increased welding efficiency.

[0084] In addition, since the protrusion 54 is at least partially provided in the first through hole 13, it facilitates the positioning and installation of 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 post 30, it can make the seal 40 fill the corresponding position more accurately during the installation process, reduce the sealing gap, thereby improving the sealing performance and more effectively reducing electrolyte leakage inside the secondary battery 100 and the intrusion of external impurities.

[0085] In some embodiments, referring to Figures 2 and 9, the first wall portion 12 includes a first wall surface 121 facing away from the receiving cavity 11 and a second wall surface 122 facing the receiving cavity 11. A connecting piece 50 is disposed on the first wall surface 121, and 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 embodiments of this application, side welding is used, which is welding from the side. The welding heat source acts directly 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, thereby reducing the amount of heat received by the area where the passivation layer 51 is located, and reducing the risk of the passivation layer 51 being damaged due to overheating.

[0086] It should be noted that, regardless of the welding method described above, the welding width can be between 0.03mm and 0.3mm. This ensures sufficient welding area between the connecting piece 50 and the housing 10, allowing them to be firmly joined together. It also reduces the impact of welding on the passivation layer 51 between the connecting piece 50 and the seal 40, thereby improving both connection stability and the sealing performance of the secondary battery 100. Similarly, a welding width of 0.08mm to 0.15mm is preferred.

[0087] 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 excellent corrosion resistance, resisting the erosion of chemicals such as the electrolyte inside the secondary battery 100, thereby improving the stability of the connecting piece 50. Nickel oxide has strong stability and maintains stable chemical properties in the operating environment of the secondary battery 100, making it less likely to react chemically with other substances inside the secondary battery 100, which can reduce the service life of the connecting piece 50. Furthermore, nickel oxide has good adhesion, firmly adhering to the surface of the connecting piece 50 and improving the bonding strength between the connecting piece 50 and the seal 40. Alumina has stable chemical properties and excellent resistance to chemical corrosion. It can effectively resist the erosion of electrolytes, providing reliable protection for the connecting piece 50 and extending its service life. In addition, alumina 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.

[0088] In some other embodiments, a passivation layer 51 is provided on the entire outer surface of the connecting piece 50, so that the passivation layer 51 completely encapsulates the connecting piece 50, which can further reduce the corrosion of the connecting piece 50.

[0089] In the embodiments of this application, the sealing element 40 is made of hot melt adhesive and / or pressure-sensitive adhesive. During installation, it can be connected to the first wall portion 12 by hot pressing the connecting piece 50. The operation is simple and convenient, which is conducive to improving the production efficiency of the secondary battery 100.

[0090] In some embodiments, referring to Figures 10 and 11, the sealing member 40 includes a first insulating layer 41 and a second insulating layer 42 stacked together. 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℃≤T1≤130℃, and any value from 100℃ to 130℃ can be selected, such as 100℃, 105℃, 110℃, 115℃, 120℃, 125℃ or 130℃, etc.

[0091] The melting point of the second insulating layer 42 is T2, 140℃≤T2≤190℃. Any value from 140℃ to 190℃ can be selected, such as 140℃, 145℃, 150℃, 155℃, 160℃, 165℃, 170℃, 175℃, 180℃, 185℃ or 190℃, etc.

[0092] The secondary battery 100 may pose safety hazards due to internal high temperature and pressure during use. For example, when the secondary battery 100 experiences a short circuit, overcharge, or localized overheating, the internal temperature rises along with the gas pressure. Because the first insulating layer 41 has a low melting point, it will melt first in the temperature range of 100°C to 130°C, thus forming a pressure relief channel connecting the inside of the casing 10 to the outside. This can effectively mitigate thermal runaway and reduce the risk of the secondary battery 100 catching fire or exploding. Furthermore, the second insulating layer 42 has a higher melting point. When the first insulating layer 41 melts, the second insulating layer 42 can remain in a solid state, thereby insulating the terminal 30 from the casing 10 and reducing the occurrence of short circuits.

[0093] In addition, the channel formed after the first insulating layer 41 melts can serve as an initial pressure relief path, allowing the internal pressure of the secondary battery 100 to be 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. The secondary battery 100 can be resealed by making simple adjustments to the seal 40, which is beneficial for the reuse of the seal 40.

[0094] In some other embodiments, referring to Figures 12 and 13, the seal 40 further includes a third insulating layer 43. Along the direction from the first wall portion 12 to the connecting piece 50, the third insulating layer 43 is bonded between the second insulating layer 42 and the flange portion 32. The melting point of the third insulating layer 43 is T3, 100℃≤T3≤130℃, and any value between 100℃ and 130℃ can be selected, such as 100℃, 105℃, 110℃, 115℃, 120℃, 125℃, or 130℃. Under normal operating temperature, all three insulating layers are in a solid state, providing a thicker insulation and sealing barrier. This improves the bonding strength between the connecting piece 50 and the electrode post 30, and enhances the sealing effect of the seal 40 on the internal electrolyte of the secondary battery 100 and on external moisture and gas, reducing the risk of leakage.

[0095] When the internal temperature of the secondary battery 100 rises, 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. This helps to respond promptly to abnormal temperature rises in the secondary battery 100, further mitigating thermal runaway and reducing the risk of fire or explosion of the secondary battery 100.

[0096] For the material of the sealing element 40, the first insulating layer 41, the second insulating layer 42, and the third insulating layer 43 are each 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, and reduces damage to the sealing element 40 due to chemical corrosion, thereby improving the sealing performance of the sealing element 40. Furthermore, each material has low permeability to gases and liquids, which can reduce internal electrolyte leakage and prevent external air and moisture from entering the secondary battery 100, thus helping to maintain the normal operation of the secondary battery 100.

[0097] To adjust the melting point of the sealing components, the following methods can be used: 1) Blending modification: Polymers with different melting points are blended, utilizing the interactions between the polymers to alter the melting point. For example, blending high-melting-point PP with low-melting-point LDPE can lower the melting point of PP to some extent while improving the heat resistance of LDPE. 2) Adding plasticizers: Plasticizer molecules insert into the polymer molecular chains, weakening the intermolecular forces and making the chains more mobile, thus lowering the melting point. For example, adding phthalate plasticizers to PVC can significantly reduce the melting point and hardness of PVC, while improving its flexibility. 3) Chemical modification: Introducing new groups or altering the molecular chain structure through chemical reactions can change the melting point of the material. For example, copolymerizing PET by introducing a third monomer can disrupt the regularity of the PET molecular chains, reducing its crystallinity and thus lowering the melting point. Additionally, the melting point can be adjusted by changing the processing technology. Different processing technologies, such as extrusion, injection molding, and blow molding, as well as parameters such as temperature, pressure, and cooling rate during processing, can affect the crystallization behavior and morphology of polymers, thereby affecting their melting point. For example, rapid cooling can cause polymers to form smaller crystal sizes, lowering the material's melting point.

[0098] Regarding the thickness of the seal 40, in some embodiments, referring to the figure, the thickness of the seal 40 along the direction from the first wall portion 12 to the connecting piece 50 is H, 0.05mm≤H≤1mm, and any value from 0.05mm to 1mm can be selected, such as 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.

[0099] Under normal temperature conditions, this thickness range allows the seal 40 to have good insulation properties, effectively reducing electrical short circuits between the connecting piece 50 and the flange 32. It also effectively blocks the electrolyte inside the secondary battery 100 from external moisture, improving the connection stability between the terminal 30 and the housing 10, and enhancing the sealing performance of the secondary battery 100. When the temperature rises, the first insulating layer 41 and the third insulating layer 43 melt according to their melting point characteristics, thereby forming a better pressure relief channel and quickly responding to abnormal temperature increases in the secondary battery 100. Simultaneously, the second insulating layer 42 remains solid at a certain temperature range, resulting in better insulation between the terminal 30 and the housing 10 / connecting piece 50.

[0100] Furthermore, within the thickness range of 0.1mm≤H≤0.3mm, the thermal response of each insulating layer at high temperature is more precise. This improves the connection stability between the electrode post 30 and the connecting piece 50, and enables timely response to abnormal increases in the stability of the secondary battery 100, thereby reducing material costs and energy density loss.

[0101] 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, reducing the risk of fire or explosion of the secondary battery 100. Simultaneously, the second insulating layer 42 also has sufficient thickness to maintain subsequent insulation effects, reducing the risk of short circuits in 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.

[0102] Regarding the thickness of the connecting piece 50, along the direction from the first wall surface 121 to the second wall surface 122, the thickness of the connecting piece 50 is H4, where 0.04mm ≤ H4 ≤ 0.5mm. Any value from 0.04mm to 0.5mm can be selected, such as 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. This gives the connecting piece 50 better structural strength, reducing deformation of the connecting piece 50 during the assembly of the secondary battery 100 and vibration; and within the above thickness range, the impact on the passivation layer 51 can be reduced during welding, facilitating the welding of the connecting piece 50 to the shell 10 and improving the connection strength between the connecting piece 50 and the shell 10. If the thickness is small, for example, less than 0.04 mm, it may affect the passivation layer 51 during welding, thereby weakening the bond 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, it will occupy a large space, resulting in a loss of energy density in the secondary battery 100.

[0103] Furthermore, 0.1mm≤H4≤0.3mm can further reduce the impact on the passivation layer 51 during welding, as well as the impact on the energy density of the secondary battery 100.

[0104] In some embodiments, the diameter of the column 31 is R, where 0.1mm ≤ R ≤ 0.6mm, and any value from 0.1mm to 0.6mm can be selected, such as 0.1mm, 0.2mm, 0.3mm, 0.4mm, 0.5mm, or 0.6mm. In the embodiments of this application, a structure in which the sealing element 40 is bonded to the electrode post 30 is adopted. Since bonding the electrode post 30 will not cause significant deformation to the column 31 and flange portion 32 of the electrode post 30, a relatively small diameter of the column 31 can be used. Compared with riveting the electrode post 30, the bonding method reduces the mechanical stress and deformation generated during the riveting process, allowing the electrode post 30 to maintain a more precise size and shape, which is beneficial to improving the structural integrity of the electrode post 30 under small diameter conditions. Furthermore, the column 31 diameter range of 0.1mm to 0.6mm provides more flexibility in the structural design of the secondary battery 100. A smaller column 31 diameter allows for a more compact internal layout of the battery, improving space utilization and helping to achieve the miniaturization design requirements of the secondary battery 100.

[0105] Furthermore, in this application, a single-layer flange is used to bond to one side of the first wall, which is beneficial for controlling the surface of the passivation layer, reducing scratches, oil stains, and other issues on the passivation layer, thereby improving the bonding effect.

[0106] Secondly, this application also proposes an electronic device, including a secondary battery 100 as described in any of the embodiments of the first aspect above. The electronic device in this application is not particularly limited and 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, power tools, electric vehicles, electric cars, ships, spacecraft, etc. Among them, electric toys can include stationary or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc., and spacecraft can include airplanes, rockets, space shuttles, and spacecraft, etc.

[0107] Example 1

[0108] Preparation of the positive electrode sheet:

[0109] 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 5×10⁻⁶). 5The materials were mixed at a mass ratio of 94:3:3, with N-methylpyrrolidone (NMP) added as a solvent to prepare a positive electrode slurry with a solid content of 75 wt%, and stirred evenly under vacuum. An aluminum foil with a thickness of 8 μm and a length of 1000 mm was selected as the positive electrode current collector. The positive electrode slurry was uniformly coated on one surface of the aluminum foil and dried at 110°C to obtain a positive electrode sheet with a single-sided coating of positive active material. The above steps were then repeated on the other surface of the aluminum foil to obtain a positive electrode sheet with a double-sided coating of positive active material.

[0110] Preparation of negative electrode sheet:

[0111] A mixture of graphite powder (negative electrode active material), silicon powder, conductive carbon black (Super P) as a conductive agent, and styrene-acrylic rubber (SD-3) as a binder was prepared in a weight ratio of 89.5:8:1:1.5. Deionized water was then added as a solvent to prepare a negative electrode slurry with a solid content of 50 wt%, and the mixture was stirred thoroughly. A copper foil with a thickness of 5 μm and a length of 1050 mm was selected as the negative electrode current collector. The negative electrode slurry was uniformly coated onto one surface of the copper foil and dried at 90°C to obtain a single-sided negative electrode sheet. This completes the single-sided coating of the negative electrode sheet. The above steps were then repeated on the other surface of the negative electrode sheet to obtain a double-sided coated negative electrode sheet.

[0112] Preparation of the separating membrane:

[0113] A porous separator membrane was prepared by using polyethylene as a 7μm substrate layer and polyvinylidene fluoride as an adhesive layer, with an alumina ceramic layer of 2μm thickness placed on the side of the adhesive layer away from the substrate layer.

[0114] Electrolyte preparation:

[0115] In a dry argon atmosphere, ethylene carbonate, methyl ethyl carbonate and diethyl carbonate were mixed in a mass ratio of 30:50:20 to obtain an organic solution. Then, 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.

[0116] Preparation of lithium-ion secondary batteries:

[0117] The positive electrode sheet is welded to the aluminum sheet positive electrode tab, and the negative electrode sheet is welded to the nickel sheet negative electrode tab. The separator, positive electrode sheet, separator, and negative electrode sheet are stacked in sequence and wound to obtain the electrode assembly. The electrode assembly is placed in a steel housing, which has a first wall, including a first wall surface facing away from the housing cavity and a second wall surface facing the housing cavity. A chromium oxide passivation layer is formed on the connecting piece. A polypropylene seal is used to bond the flange of the electrode post to the passivation layer of the connecting piece. The surface of the connecting piece facing away from the passivation layer is welded to the second wall surface. The weld width W1 between the connecting piece and the passivation layer is 0.02 mm. The connecting piece is 1.8 mm wide, and the weld penetration does not reach the passivation layer. The width of the non-welded area of ​​the passivation layer is 1.8 mm. The electrode post extends to the second through hole of the connecting piece and the first through hole of the first wall. The seal thickness H is 0.1 mm. After processes such as encapsulation, formation, capacity testing, and voltage and internal resistance testing, a lithium-ion secondary battery is produced.

[0118] Unlike Example 1, the relevant parameters in Examples 2 to 36 and Comparative Example 1 are shown in Table 1 below. In Comparative Example 1, the connecting piece does not have a passivation layer. In Example 25, the connecting piece is disposed on the second wall surface and also has a protrusion, which is welded to the inner wall of the first through hole. In Example 26, the connecting piece is disposed on the first wall surface, and the connecting piece is welded to the first wall from the side. In Example 27, the width of the connecting piece is 1.9 mm, the weld penetration does not reach the passivation layer, and the width of the non-welded area of ​​the passivation layer is 1.9 mm. In Examples 10 to 12 and Examples 28 to 36, the weld penetration reaches the passivation layer, thereby forming a welded area on the passivation layer.

[0119] Peel strength test: The peel strength between the terminal and the first wall was tested using a high-speed rail tensile testing machine according to GB / T 2792-2014 "Test Method for Peel Strength of Adhesive Tapes". The procedure is as follows: The lithium-ion secondary battery was discharged to 0V, and then the lithium-ion secondary battery was disassembled. The connecting piece, seal, and terminal bonding structure were removed as a whole. The electrolyte on the surface was wiped off with lint-free paper. A multi-functional tensile testing machine was used, with the connecting piece clamped at one end and the flange of the terminal clamped at the other end (a special clamp is required). The tensile speed was usually 50 mm / min. The peel strength (N / mm) at the time of sample separation was recorded.

[0120] Table 1

[0121]

[0122] According to Table 1 above, and in conjunction with Examples 1 to 26 and Comparative Example 1, it can be seen that when a passivation layer is provided on the connecting piece and bonded to the sealant through the passivation layer, the bonding strength can be effectively improved. The passivation layer can improve the interfacial bonding force between the connecting piece and the sealant, enabling the sealant to better interact with the surface of the connecting piece during curing or bonding, forming a stronger bond. Furthermore, the passivation layer facilitates better fit between the sealant and the connecting piece, allowing the sealant to adhere more tightly to the passivation layer, reducing the risk of gaps or leaks at the seal, thereby enhancing sealing performance.

[0123] In both Examples 1 to 12, the bonding strength is relatively high. However, in Example 12, the weld width is larger, which causes excessive heat generated during welding to be transferred to the connecting piece, forming a large heat radiation area. This may damage the passivation layer, or even directly cause the welded area to extend into the passivation layer, damaging it and weakening the bonding strength between the seal and the passivation layer 51. In Example 1, the weld width is smaller, resulting in a weaker bond strength between the connecting piece and the housing, which may lead to loosening between the connecting piece and the housing, also affecting the sealing performance. In both Examples 2 to 11, a thickness of 0.03mm ≤ W1 ≤ 0.3mm can be selected.

[0124] In Examples 4 to 7, the bonding strength is high and the impact on the structural strength of the connecting piece and the shell is small. Considering that while improving the bonding strength between the connecting piece and the pole post, the bonding strength between the connecting piece and the shell is also improved, in the embodiments of this application, 0.08mm≤W1≤0.15mm is selected.

[0125] In conjunction with Examples 13 to 24, Examples 14 to 24, and Example 7, the adhesive strength is relatively high. In Example 13, the thickness of the seal is relatively small, making it difficult to provide sufficient adhesive force and potentially hindering the formation of a pressure relief channel. In Example 24, the thickness of the seal is relatively large, resulting in high material costs and affecting the battery's energy density. Furthermore, the adhesive strength is similar to that of Example 23. Considering improving adhesive strength while reducing energy density loss, a thickness of 0.05mm ≤ H ≤ 1mm can be selected.

[0126] In Examples 16 to 18 and Example 7, the bond strength is greater than that in Examples 13 to 15, and the bond strength is not significantly different from that in Examples 19 to 24. Examples 16 to 18 and Example 7 have lower material costs and less impact on energy density. In the embodiments of this application, a thickness of 0.1 mm ≤ H ≤ 0.3 mm is preferred.

[0127] In Examples 25 and 26, protrusion welding and side welding were used respectively, which can also reduce the impact of welding on the passivation layer and thus improve the bonding strength between the connecting piece and the pole.

[0128] In conjunction with Examples 27 to 36 and Example 9, in Example 36, the area of ​​the non-welded region of the passivation layer is small, which weakens the protective function of the passivation layer and makes it more susceptible to corrosion. Furthermore, an excessively large welded area can affect the bonding strength between the seal and the connecting piece, weakening their bond strength and potentially reducing the stability of the internal structure of the secondary battery. In Example 27, the non-welded region is large. An excessively large non-welded region means that the surrounding area suitable for effective welding is relatively small. To ensure welding quality, higher precision and more accurate energy output may be required, which reduces welding efficiency, increases production time and cost, and its peel strength is similar to that of Example 9. Additionally, a large non-welded region means a larger diameter connecting piece, which may affect the thickness of the secondary battery and cause energy density loss. Therefore, in the embodiments of this application, the width of the non-welded region can be selected as 0.6mm ≤ W2 ≤ 1.8mm.

[0129] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and not to limit them; under the concept of this application, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of different aspects of this application as described above, which are not provided in detail for the sake of brevity; although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or make equivalent substitutions for some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A secondary battery, characterized in that, include: A housing that encloses a receiving cavity, the housing including a first wall portion, the first wall portion being provided with a first through hole communicating with the receiving cavity; A connecting piece is disposed on the first wall portion. The connecting piece is provided with a second through hole, which communicates with the first through hole. A passivation layer is provided on the surface of the connecting piece facing away from the first wall portion. An electrode post includes a post body and a flange portion, the flange portion being disposed on the side of the connecting piece opposite to the first wall portion, the post body being connected to the flange portion, and the post body portion being disposed in the first through hole and the second through hole; A sealing element 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 receiving cavity and a second wall surface facing the receiving cavity, and the connecting piece is welded to the second wall surface to form a first weld portion.

3. The secondary battery according to claim 2, characterized in that, Viewed in the opposite direction of the first direction, the passivation layer includes a non-welded area, and along the second direction, the width of the non-welded area is W2, 0.6mm≤W2≤1.8mm; Wherein, 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, Viewed along the first direction, the first welded part is arranged around the first through hole; viewed along the second direction, the width of the first welded part is W1, 0.03mm≤W1≤0.3mm. Wherein, 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 receiving cavity and a second wall surface facing the receiving cavity; The connecting piece is disposed on the second wall surface, and the surface of the connecting piece opposite to the sealing element has a protrusion. The second through hole passes through the protrusion, and the protrusion is at least partially disposed in the first through hole. The protrusion 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 facing away from the receiving cavity and a second wall surface facing the receiving cavity, and the connecting piece is disposed 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 passivation layer is provided on the entire outer surface of the connecting piece.

10. The secondary battery according to claim 1, characterized in that, The sealant includes hot melt adhesive and / or pressure-sensitive adhesive.

11. The secondary battery according to claim 1, characterized in that, The sealing element includes a first insulating layer and a second insulating layer stacked together; The first insulating layer is bonded between the second insulating layer and the connecting piece. The melting point of the first insulating layer is T1, 100℃≤T1≤130℃, and the melting point of the second insulating layer is T2, 140℃≤T2≤190℃.

12. The secondary battery according to claim 11, characterized in that, The sealing element further includes a third insulating layer. Along the direction from the first wall portion to the connecting piece, the third insulating layer is bonded between the second insulating layer and the flange portion. The melting point of the third insulating layer is T3, and 100℃≤T3≤130℃.

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 seal is H, where 0.05mm≤H≤1mm.

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, where 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, where 0.1mm ≤ R ≤ 0.6mm.

19. An electronic device, characterized in that, Includes the secondary battery as described in any one of claims 1 to 18.

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