Secondary battery, battery pack, and electronic device

Abstract

The utility model provides a secondary battery, a battery pack and an electronic device, the secondary battery comprises a shell, a first corrosion-resistant layer and a second corrosion-resistant layer, the shell comprises an end wall and a side wall surrounding the end wall, and the side wall and the end wall are integrally stretched and formed; the first corrosion-resistant layers are arranged on the outer walls of the end walls and the side walls; the second corrosion-resistant layers are arranged on the inner walls of the end walls and the side walls; in the same thickness direction of the shell, the thickness of the first corrosion-resistant layer is larger than that of the second corrosion-resistant layer, and the technical problem that the safety and the corrosion resistance are reduced due to the fact that the corrosion-resistant layers fall off when the shell is stretched can be solved.

Description

Technical Field

[0001] The utility model relates to the technical field of batteries, and in particular to a secondary battery, a battery pack and an electronic device. Background Art

[0002] At present, cylindrical batteries are widely used in various industries due to their advantages such as mature production technology, high yield rate, low processing cost, good safety performance and heat dissipation performance.

[0003] In order to better protect the internal structure of the cylindrical battery electrode assembly and make the shell have a certain structural rigidity, steel shell packaging is usually used. In order to enhance the corrosion resistance and safety of the shell, the process of pre-plating the corrosion-resistant layer is usually adopted, that is, the base steel is pre-plated with a corrosion-resistant layer before the shell is stamped to improve the coating adhesion and corrosion resistance. However, during the stamping and stretching process of the shell, the corrosion-resistant layer will fall off and peel off. After the corrosion-resistant layer on the inner wall of the shell falls off, excessive deposits will appear, posing a safety hazard of puncturing the diaphragm. The outer wall of the shell will have pitting problems due to the shedding of the corrosion-resistant layer. Utility Model Content

[0004] In view of the above shortcomings of the prior art, the present invention provides a secondary battery, a battery pack and an electronic device to improve the technical problem of reduced safety and corrosion resistance caused by the peeling of the corrosion-resistant layer due to the stretching of the shell.

[0005] To achieve the above-mentioned purpose and other related purposes, the present invention provides a secondary battery, a battery pack and an electronic device, wherein the secondary battery includes a shell, a first corrosion-resistant layer and a second corrosion-resistant layer, the shell includes an end wall and a side wall surrounding the end wall, and the side wall and the end wall are integrally stretched and formed; the first corrosion-resistant layer is arranged on the outer wall of the end wall and the side wall; the second corrosion-resistant layer is arranged on the inner wall of the end wall and the side wall; along the same thickness direction of the shell, the thickness of the first corrosion-resistant layer is greater than the thickness of the second corrosion-resistant layer.

[0006] In the above technical solution, the thinner thickness of the second corrosion-resistant layer can reduce the amount of deposited material formed by the shedding of the coating when the side wall is stretched, alleviate the problem of the deposited material piercing the diaphragm, and reduce the risk of thermal runaway of the battery. This setting can improve the safety performance of the battery while achieving the corrosion resistance of the inner side of the shell. The thicker thickness of the first corrosion-resistant layer can reduce the risk of rupture of the outer wall of the shell due to shedding of the coating, thereby improving the corrosion resistance and rust prevention of the outer wall of the shell. At the same time, the thicker second corrosion-resistant layer can improve the wear resistance of the outer side of the shell, so that the shell can adapt to complex external working conditions.

[0007] In an example of the secondary battery of the present invention, the secondary battery further includes an electrode assembly, the electrode assembly is disposed in the shell, and the second corrosion-resistant layer includes a copper plating layer facing the electrode assembly.

[0008] In the above technical solution, since copper has better oxidation resistance and good conductivity, the copper plating layer is set at a position facing the electrode assembly, that is, the copper plating layer is used to isolate the shell and the electrolyte, which can improve the corrosion resistance and conductivity of the shell.

[0009] In an example of the secondary battery of the present invention, the first corrosion-resistant layer includes a first nickel-plated layer, and the second corrosion-resistant layer includes a second nickel-plated layer.

[0010] In the above technical solution, the first corrosion-resistant layer and the second corrosion-resistant layer are made of the same material, and only one process is required to complete the electroplating, which can improve the efficiency of electroplating. In addition, nickel has good corrosion resistance and welding performance, and has better comprehensive performance. Therefore, this technical solution can not only make the shell have better corrosion resistance, wear resistance and rust prevention effects, but also improve production efficiency and reduce production costs.

[0011] In an example of the secondary battery of the present invention, the second corrosion-resistant layer further includes a copper plating layer located on a side of the second nickel plating layer away from the shell.

[0012] In the above technical solution, a copper plating layer is provided on the outer layer of the second nickel plating layer, so that the copper plating layer is located on the innermost side of the shell. On the one hand, this setting can improve the corrosion resistance and conductivity of the inner side of the shell because copper has better oxidation resistance and good conductivity. On the other hand, the inner wall of the shell is doubly protected, which can further alleviate the problem of pitting corrosion on the inner wall of the shell caused by the stretching of the shell, and improve the corrosion resistance of the inside of the shell.

[0013] In an example of the secondary battery of the present invention, the thickness of the first nickel plating layer located on the outer side of the end wall is greater than or equal to 4 μm.

[0014] In the above technical solution, the first nickel plating layer has a fluxing effect. The setting of the nickel plating layer with a thickness greater than or equal to 4μm is conducive to the formation of a weld pool on the end wall during welding. The weld mark contains nickel, which can improve the corrosion resistance of the weld mark.

[0015] In an example of the secondary battery of the present invention, the thickness of the first corrosion-resistant layer ranges from 2 μm to 5 μm.

[0016] In the above technical solution, the thickness of the first corrosion-resistant layer is greater than or equal to 2 μm, which can effectively prevent the corrosion of the outer wall of the shell by water vapor in the air, that is, improve the anti-rust effect of the outer wall of the shell, and at the same time make the shell have better wear resistance and corrosion resistance; the setting of the thickness of the first corrosion-resistant layer is less than or equal to 5 μm, so that the shell has higher wear resistance, corrosion resistance and rust prevention effects while having lower cost.

[0017] In an example of the secondary battery of the present invention, the thickness of the second corrosion-resistant layer ranges from 1 μm to 2 μm.

[0018] In the above technical solution, the second corrosion-resistant layer with a thickness greater than or equal to 1 μm can reduce the problem of breakage during the stretching process of the shell, and thus reduce the risk of corrosion caused by local loss of protection of the shell. The thickness of the second corrosion-resistant layer is limited to within 2 μm, which can achieve high corrosion resistance of the second corrosion-resistant layer while reducing the amount of deposited materials generated by the stretching of the shell, thereby improving the safety performance of the battery.

[0019] In an example of the secondary battery of the present invention, the thickness of the first corrosion-resistant layer located on the end wall is a, the thickness of the first corrosion-resistant layer located on the side wall is b, and 1<a / b<3.

[0020] In the above technical solution, by limiting the ratio of the first corrosion-resistant layer located on the end wall to the first corrosion-resistant layer located on the side wall to within the range of 1 < a / b < 3, the stretching ratio of the first corrosion-resistant layer located on the side wall can be limited to not be too high. This reduces the possibility of the first corrosion-resistant layer being broken, thereby improving the corrosion resistance and wear resistance of the first corrosion-resistant layer.

[0021] The utility model also provides a battery pack, which includes any one of the above-mentioned secondary batteries.

[0022] The utility model also provides an electronic device, which includes the above-mentioned battery pack.

[0023] In this secondary battery, the thinner second corrosion-resistant layer can reduce the amount of deposited material formed by plating shedding during sidewall stretching, alleviate the problem of deposited material piercing the diaphragm, and reduce the risk of thermal runaway. This configuration improves the battery's safety while also providing corrosion resistance on the inside of the housing. The thicker first corrosion-resistant layer can reduce the risk of cracking the outer wall of the housing due to plating shedding, thereby improving the corrosion resistance and rust prevention of the outer wall of the housing. Furthermore, the thicker second corrosion-resistant layer can improve the wear resistance of the outer side of the housing, enabling the housing to adapt to complex external operating environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other embodiments can be obtained based on these drawings without paying any creative work.

[0025] Figure 1 This is a schematic structural diagram of an embodiment of a secondary battery of the present utility model;

[0026] Figure 2 This is a cross-sectional view of an electrode assembly in one embodiment of a secondary battery of the present invention;

[0027] Figure 3 This is a schematic structural diagram of a housing of an embodiment of a secondary battery of the present invention;

[0028] Figure 4 for Figure 3 A partial enlarged view of point A of an embodiment of a secondary battery of the present invention;

[0029] Figure 5 for Figure 3 A partial enlarged view of point A of another embodiment of the secondary battery of the present invention;

[0030] Figure 6 for Figure 3 A partial enlarged view of point A of another embodiment of the secondary battery of the present invention;

[0031] Figure 7 This is a schematic diagram of an embodiment of a battery pack of the present invention;

[0032] Figure 8 FIG. 1 is a schematic diagram of an electronic device according to an embodiment of the present invention.

[0033] Component number description

[0034] 1. Electronic device; 10. Battery pack; 11. Working part; 101. Box; 102. Box cover; 100. Secondary battery; 110. Shell; 111. End wall; 112. Side wall; 113. Opening; 120. First corrosion-resistant layer; 121. First nickel-plated layer; 130. Second corrosion-resistant layer; 131. Copper-plated layer; 132. Second nickel-plated layer; 140. Electrode assembly; 141. First pole piece; 1411. Positive electrode current collector; 1412. First coated area; 1413. First uncoated area; 142. Diaphragm; 143. Second pole piece; 1431. Negative electrode current collector; 1432. Second coated area; 1433. Second uncoated area; 144. First pole tab; 145. Second pole tab; 150. Post; 160. End cover. DETAILED DESCRIPTION

[0035] The following describes the implementation of the present invention through specific examples. Those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific implementation methods. The details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the following examples and the features in the examples can be combined with each other unless there is a conflict. It should also be understood that the terms used in the examples of the present invention are for the purpose of describing specific implementation methods, not for the purpose of limiting the scope of protection of the present invention. The test methods for which specific conditions are not specified in the following examples are generally carried out under conventional conditions or under the conditions recommended by the manufacturers.

[0036] When numerical ranges are given in the examples, it should be understood that unless otherwise specified herein, both endpoints of each numerical range and any value between the endpoints may be used. Unless otherwise defined, all technical and scientific terms used in this utility model are consistent with the prior art as understood by those skilled in the art and the description of this utility model. Any prior art methods, equipment, and materials similar or equivalent to those in the examples of this utility model may also be used to implement this utility model.

[0037] It should be noted that the terms such as "upper", "lower", "left", "right", "middle" and "one" cited in this specification are only for the convenience of description and are not used to limit the scope of implementation of the present invention. Changes or adjustments to their relative relationships should be regarded as the scope of implementation of the present invention without substantially changing the technical content.

[0038] A secondary battery includes an electrode assembly, which is a component where electrochemical reactions occur in the secondary battery and may include one or more electrode assemblies.

[0039] The secondary battery also includes a shell, an end cover and a pole. The shell includes an end wall and a side wall surrounding the end wall. The end wall and the side wall are stretched and formed as one piece. One end of the side wall has an opening. The electrode assembly can be assembled into the shell through the opening of the shell. The end cover is used to cover the opening of the shell to achieve sealing. The pole passes through the end wall and is electrically connected to the electrode assembly to conduct the electrical energy generated by the electrode assembly.

[0040] In order to better protect the internal structure of the cylindrical battery electrode assembly and make the shell have a certain structural rigidity, steel shell packaging is usually used. In order to enhance the corrosion resistance and safety of the shell, a pre-corrosion-resistant coating process is usually adopted, that is, the base steel is pre-plated with a corrosion-resistant layer before the shell is stamped to improve the coating adhesion and corrosion resistance.

[0041] However, the inventors discovered that during the stamping and stretching process of the shell, the corrosion-resistant layer can peel off. This can lead to excessive sedimentation inside the shell, potentially piercing the diaphragm and causing a short circuit between the positive and negative electrodes. Furthermore, the area where the corrosion-resistant layer has peeled off is susceptible to pitting corrosion. In environments with high humidity or high temperatures, the peeling of the corrosion-resistant layer on the outer shell wall can also cause pitting corrosion on the outer surface of the shell. Furthermore, since the shell inevitably rubs during transportation, the outer shell wall also requires high wear resistance.

[0042] In view of this, the utility model provides a technical solution, which makes the thickness of the second corrosion-resistant layer located on the inner side of the shell thinner than the thickness of the first corrosion-resistant layer located on the outer side of the shell, so as to reduce the peeling of the coating when the side wall is stretched, and improve the corrosion resistance and rust prevention of the outer wall of the shell. At the same time, the thicker second corrosion-resistant layer can improve the wear resistance of the outer side of the shell, so that the shell can adapt to complex external working conditions.

[0043] See also Figures 1 to 8 The present invention provides a secondary battery 100 , which includes a shell 110 , an electrode assembly 140 , a first corrosion-resistant layer 120 , a second corrosion-resistant layer 130 , a pole 150 and an end cover 160 .

[0044] See also Figure 1 and Figure 3 The shell 110 includes an end wall 111 and a side wall 112 surrounding the end wall 111. The side wall 112 and the end wall 111 are stretched and formed as a whole. The stretching process is a stamping processing method that uses a stretching die to press a sheet blank into a hollow part with various openings 113. Specifically, in this embodiment, a suitable die is first selected according to the target shape of the shell 110. For example, the shape of the shell 110 can be a square shell, a cylindrical shell or a polygonal prismatic shell, etc., and then the blank is stamped. The first step is to stamp out the prototype of the end wall 111, the side wall 112 and the cavity. In order to ensure the reliability of the stretching and avoid stretching fracture, it is necessary to replace the die of different sizes multiple times and stamp multiple times until the preset size is stretched.

[0045] In this embodiment, please refer to Figure 3The outer edge of the end wall 111 is circular, and the side wall 112 is cylindrical and surrounds the outer edge of the end wall 111, and a circular opening 113 is formed at the end of the side wall 112 away from the end wall 111. A accommodating cavity is formed in the shell 110 surrounded by the end wall 111 and the side wall 112, which is used to accommodate the electrode assembly 140, electrolyte and other necessary battery components. Specifically, the diameter of the shell 110 can be determined according to the specific size of the electrode assembly 140, such as 18mm, 21mm, 46mm, etc. The material of the shell 110 can be various, for example, copper, iron, aluminum, steel, aluminum alloy, etc. In order to prevent the shell 110 from rusting during long-term use, a layer of rust-proof material such as metal nickel can be plated on the surface of the shell 110.

[0046] See also Figures 3 to 6 In order to enhance the corrosion resistance and safety of the housing 110, a pre-plating process for a corrosion-resistant layer is generally employed. That is, the base steel is pre-plated with a corrosion-resistant layer before the housing 110 is stamped to improve the coating's adhesion and corrosion resistance. Specifically, the secondary battery 100 further comprises a first corrosion-resistant layer 120, which is disposed on the outer walls of the end wall 111 and the side wall 112, the outer wall being the wall facing away from the electrode assembly 140. The material of the first corrosion-resistant layer 120 is not limited, and may be, for example, nickel, chromium, zinc, tin, copper, or a combination of two or more of the above materials. The secondary battery 100 further comprises a second corrosion-resistant layer 130, which is disposed on the inner walls of the end wall 111 and the side wall 112, the inner wall being the wall facing the electrode assembly 140. The material of the first corrosion-resistant layer 120 is not limited, and may be, for example, nickel, chromium, zinc, tin, copper, or a combination of two or more of the above materials.

[0047] Further, see Figures 3 to 6, along the same thickness direction of the shell 110, the thickness of the first corrosion-resistant layer 120 is greater than the thickness of the second corrosion-resistant layer 130. The thinner thickness of the second corrosion-resistant layer 130 can reduce the amount of deposited material formed by the shedding of the coating when the side wall 112 is stretched, alleviate the problem of the deposited material piercing the diaphragm 142, and reduce the risk of thermal runaway of the battery. This setting can improve the safety performance of the battery while playing the role of corrosion resistance on the inside of the shell 110. The thicker thickness of the first corrosion-resistant layer 120 located on the outside of the shell 110 can reduce the risk of rupture of the outer wall of the shell 110 due to shedding of the coating, thereby improving the corrosion resistance and rust prevention effect of the outer wall of the shell 110. At the same time, the thicker second corrosion-resistant layer 130 can improve the wear resistance of the outer side of the shell 110, so that the shell 110 can adapt to complex external working conditions. It should be noted that the thickness of the first corrosion-resistant layer 120 and the thickness of the second corrosion-resistant layer 130 can be measured by a coating thickness gauge. In this embodiment, the thickness of the first corrosion-resistant layer 120 and the thickness of the second corrosion-resistant layer 130 for comparison are obtained by measuring two corresponding positions along the same thickness direction of the shell 110 .

[0048] See also Figures 1 to 2 The electrode assembly 140 is housed in the housing 110. The electrode assembly 140 is a component where electrochemical reactions occur in the secondary battery 100. The housing 110 may contain one or more electrode assemblies 140. The electrode assembly 140 includes a first electrode sheet 141, a second electrode sheet 143, and a separator 142 stacked and wound to form a wound structure. The first electrode sheet 141 and the second electrode sheet 143 have opposite polarities. In some embodiments, the first electrode sheet 141 is a positive electrode sheet and the second electrode sheet 143 is a negative electrode sheet. In other embodiments, the first electrode sheet 141 is a negative electrode sheet and the second electrode sheet 143 is a positive electrode sheet.

[0049] See also Figures 1 to 2 In this embodiment, the first electrode sheet 141 is a positive electrode sheet. Specifically, the first electrode sheet 141 includes a positive electrode current collector 1411 and a positive electrode active material. The positive electrode active material is coated on the surface of the positive electrode current collector 1411; the positive electrode current collector 1411 includes a first coated area 1412 coated with the active material and a first uncoated area 1413 not coated with the active material. The first uncoated area 1413 is located at the end of the first electrode sheet 141. The other end of the first uncoated area 1413 along the winding axis direction of the electrode assembly 140 extends out of the diaphragm 142 and is bent toward the winding axis to form a first electrode tab 144. The first electrode tab 144 is the corresponding positive electrode tab.

[0050] See also Figures 1 to 2In this embodiment, the second electrode sheet 143 is a negative electrode sheet, and the second electrode sheet 143 includes a negative electrode current collector 1431 and a negative electrode active material. The negative electrode active material is coated on the surface of the negative electrode current collector 1431; the negative electrode current collector 1431 includes a second coated area 1432 coated with the active material and a second uncoated area 1433 not coated with the active material. The second uncoated area 1433 is located at the end of the second electrode sheet 143. The second uncoated area 1433 extends out of the separator 142 along the winding axis direction of the electrode assembly 140 and is bent toward the winding axis to form a second electrode tab 145. The second electrode tab 145 is the corresponding negative electrode tab.

[0051] See also Figures 1 to 2 The separator 142 is disposed between the first electrode sheet 141 and the second electrode sheet 143 to separate the positive electrode active material layer from the negative electrode active material layer. Taking the lithium-ion secondary battery 100 as an example, the material of the positive electrode current collector 1411 can be aluminum, and the positive electrode active material layer includes a positive electrode active material, which can be lithium cobalt oxide, lithium iron phosphate, ternary lithium, or lithium manganese oxide. The material of the negative electrode current collector 1431 can be copper, and the negative electrode active material layer includes a negative electrode active material, which can be carbon or silicon. The base material of the separator 142 can be polypropylene (PP) or polyethylene (PE), etc. To provide protection and insulation for the electrode assembly 140, an insulating film can also be coated on the outside of the electrode assembly 140. The insulating film can be synthesized from PP, PE, polyethylene terephthalate (PET), polyvinyl chloride (PVC), or other polymer materials.

[0052] See also Figure 1 and Figure 2 Furthermore, in the present invention, the first tab 144 faces the end wall 111 or the opening 113, while the second tab 145 faces the other end of the housing 110. In this embodiment, the first tab 144 faces the end wall 111 and is electrically connected to the pole 150, causing the pole 150 to be positively charged. The second tab 145 faces the opening 113, and the housing 110 is electrically connected to the second tab 145, causing the housing 110 to be negatively charged. However, in other embodiments, the second tab 145 may be connected to the pole 150, while the first tab 144 is connected to the housing 110.

[0053] See also Figure 1In this embodiment, the secondary battery 100 further includes a pole 150. Specifically, the pole 150 passes through the end wall 111 and is insulated from the end wall 111. One end of the pole 150 facing the electrode assembly 140 passes through the end wall 111 to be directly electrically connected to the first pole tab 144 or electrically connected through an indirect transfer. The structure of the pole 150 can be any suitable form that can pass through the end wall 111 and be electrically connected to the first pole tab 144 of the electrode assembly 140. For example, the cross-section can be circular, square, prismatic, or a special-shaped profile that can achieve stable conductivity. The hole in the pole 150 corresponds to the shape of the pole 150. In this embodiment, the cross-section of the pole 150 is circular.

[0054] See also Figure 1 In this embodiment, the secondary battery 100 further includes an end cap 160, which is sealed against the opening 113. The outer edge of the end cap 160 corresponds to the shape of the opening 113 and is connected to the sidewall 112 to seal the opening 113. In a specific embodiment, a groove recessed toward the interior of the housing 110 is formed by rolling on the area near the outer end of the sidewall 112 of the housing 110. The groove is capable of limiting the axial displacement of the electrode assembly 140. One side of the groove forms an annular step around the housing 110, on which the end cap 160 is placed. A sealing ring is provided between the end cap 160 and the sidewall 112. The edge of the opening 113 is sealed so that the end cap 160 presses against the sealing ring, forming a secure connection.

[0055] Since copper has better oxidation resistance and good electrical conductivity, please refer to Figure 4 and Figure 6 The second corrosion-resistant layer 130 includes a copper plating layer 131 facing the electrode assembly 140. It should be noted that, in an example of the secondary battery 100 of the present invention, please refer to Figure 4 , the second corrosion-resistant layer 130 may only include the copper plating layer 131. In another example of the secondary battery 100 of the present invention, please refer to Figure 6 , and may also include a copper plating layer 131 and other plating layers. It is only necessary to set the copper plating layer 131 at a position facing the electrode assembly 140 and in direct contact with the electrolyte, that is, the copper plating layer 131 is used to isolate the shell 110 and the electrolyte. This setting can improve the corrosion resistance and conductivity of the shell 110.

[0056] Since nickel has good corrosion resistance and welding performance, its comprehensive performance is better. Figure 5In another example of the secondary battery 100 of the present invention, the first corrosion-resistant layer 120 includes a first nickel-plated layer 121, and the second corrosion-resistant layer 130 includes a second nickel-plated layer 132. The first corrosion-resistant layer 120 and the second corrosion-resistant layer 130 are made of the same material, and electroplating can be completed in a single process, which can improve electroplating efficiency. Therefore, this technical solution can not only provide the housing 110 with better corrosion resistance, wear resistance, and rust prevention, but also improve production efficiency and reduce production costs.

[0057] See also Figure 6 In another example of the secondary battery 100 of the present invention, the second corrosion-resistant layer 130 further includes a copper-plated layer 131 located on the side of the second nickel-plated layer 132 away from the housing 110. This arrangement positions the copper-plated layer 131 on the innermost side of the housing 110. This arrangement improves the corrosion resistance and conductivity of the inner side of the housing 110 due to copper's superior oxidation resistance and electrical conductivity. Furthermore, it provides dual protection for the inner wall of the housing 110, further alleviating pitting corrosion on the inner wall of the housing 110 caused by stretching of the housing 110 and improving the corrosion resistance of the interior of the housing 110.

[0058] See also Figures 3 to 6 In one example of the secondary battery 100 of the present invention, the thickness of the first nickel-plated layer 121 located on the outer side of the end wall 111 is greater than or equal to 4 μm. That is, the thickness of the first nickel-plated layer 121 located on the outer side of the end wall 111 is greater than or equal to 4 μm at any location. For example, the thickness can be 4.2 μm, 4.4 μm, 4.5 μm, 4.8 μm, or 5 μm. This technical solution utilizes the soldering effect of the first nickel-plated layer 121. The setting of the first nickel-plated layer 121 with a thickness of greater than or equal to 4 μm facilitates the formation of a weld pool during welding of the end wall 111. The presence of nickel in the weld pool improves the corrosion resistance of the weld pool. It should be noted that the thickness of the first nickel-plated layer 121 can be measured using a coating thickness gauge.

[0059] See also Figures 3 to 6In one example of the secondary battery 100 of the present invention, the thickness of the first corrosion-resistant layer 120 ranges from 2μm to 5μm. It is understood that the thickness of any position of the first corrosion-resistant layer 120 is within the range of 2μm to 5μm, and may be, for example, 2μm, 2.5μm, 3μm, 3.5μm, 4μm, 4.5μm, or 5μm. The thickness of the first corrosion-resistant layer 120 is greater than or equal to 2μm, which effectively prevents water vapor in the air from corroding the outer wall of the housing 110, thereby improving the rust resistance of the outer wall of the housing 110 and providing the housing 110 with better wear resistance and corrosion resistance. The thickness of the first corrosion-resistant layer 120 is less than or equal to 5μm, which enables the housing 110 to have high wear resistance, corrosion resistance, and rust resistance while maintaining low cost. It should be noted that the thickness of the second nickel plating layer 132 can be measured using a coating thickness gauge.

[0060] See also Figures 3 to 6 In an example of the secondary battery 100 of the present invention, the thickness of the second corrosion-resistant layer 130 ranges from 1 μm to 2 μm. It is understandable that the thickness of any position of the second corrosion-resistant layer 130 is within the range of 1 μm to 2 μm, for example, it can be 1 μm, 1.2 μm, 1.5 μm, 1.8 μm or 2 μm. A second corrosion-resistant layer 130 with a thickness greater than or equal to 1 μm can reduce the problem of fracture during the stretching process of the shell 110, thereby reducing the risk of corrosion caused by partial loss of protection of the shell 110. The thickness of the second corrosion-resistant layer 130 is limited to within 2 μm. While achieving high corrosion resistance of the second corrosion-resistant layer 130, it can reduce the amount of deposited material generated by the stretching of the shell 110, thereby improving the safety performance of the battery. It should be noted that the thickness of the second nickel plating layer 132 can be measured using a plating thickness gauge.

[0061] See also Figures 3 to 6In an example of the secondary battery 100 of the present invention, the wall thickness of the first corrosion-resistant layer 120 located on the end wall 111 is a, and the wall thickness of the first corrosion-resistant layer 120 located on the side wall 112 is b, and 1<a / b<3. For example, it can be 1.1, 1.5, 2, 2.5 or 2.9. It should be noted that since the end wall 111 is only stamped in the first step and no subsequent stretching is performed, the wall thickness of the end wall 111 is approximately equal to the thickness of the raw material, i.e., the blank. Similarly, the thickness of the first corrosion-resistant layer 120 located on the end wall 111 is approximately equal to the thickness before stretching, while the side wall 112 needs to be stamped multiple times until it is stretched to a preset size. Similarly, the wall thickness of the first corrosion-resistant layer 120 located on the side wall 112 will become thinner and longer as the side wall 112 is stretched. By limiting the ratio of the first corrosion-resistant layer 120 located on the end wall 111 to the first corrosion-resistant layer 120 located on the side wall 112 to within a range of 1 to 3, the tensile strength of the first corrosion-resistant layer 120 located on the side wall 112 can be limited to not be too high. This can reduce the possibility of the first corrosion-resistant layer 120 being broken, thereby improving the corrosion resistance and wear resistance of the first corrosion-resistant layer 120.

[0062] It should be noted that the first corrosion-resistant layer 120 and the second corrosion-resistant layer 130 are stretched, lengthened and thinned as the shell 110 is stretched, so the thickness of the first corrosion-resistant layer 120 and the second corrosion-resistant layer 130 are affected by the thickness of the shell 110. Since the sudden change in size of the shell 110 during stamping and stretching can easily lead to stress concentration, reduced elongation at break and reduced structural strength, the size of the shell 110 is usually variable in thickness, and the thickness of the first corrosion-resistant layer 120 and the second corrosion-resistant layer 130 is also variable in thickness. Therefore, in this embodiment, the method for measuring the wall thickness a of the first corrosion-resistant layer 120 located on the end wall 111 is as follows: first, measure the thickness of the first corrosion-resistant layer 120 at 5 points on the circumference of 1 / 2 diameter of the end wall 111, and then calculate the average value of the 5 values; the method for measuring the wall thickness b of the first corrosion-resistant layer 120 located on the side wall 112 is as follows: first, measure the thickness of the first corrosion-resistant layer 120 at 1 / 3 height, 1 / 2 height, and 2 / 3 height of the side wall 112, specifically, first measure the thickness of the first corrosion-resistant layer 120 at 5 points on the circumference of each height, calculate the average value to obtain the thickness at each height, and then calculate the average value of the thickness at these three heights. The measuring equipment can be a coating thickness gauge.

[0063] See also Figure 7The present invention further provides a battery pack 10, which includes any of the aforementioned secondary batteries 100. In one embodiment of the present invention's battery pack 10, the battery pack 10 includes a housing 101, a housing cover 102, and a plurality of secondary batteries 100. The plurality of secondary batteries 100 are placed in the housing 101 and are connected in series or in parallel, or in a combination of series and parallel. The housing cover 102 seals the housing 101 to protect the plurality of secondary batteries 100. It should be noted that, in addition to the present invention's secondary batteries 100, the battery pack 10 may also include a battery pack 10 thermal management system, a circuit board, and other components. The battery pack 10 may be a battery module, a battery pack, an energy storage cabinet, or the like; these will not be described in detail here.

[0064] See also Figure 8 The present invention also provides an electronic device 1, which includes the above-mentioned battery pack 10. The working part 11 is electrically connected to the battery pack 10 to obtain electrical energy support. As an example, the electronic device 1 is a vehicle, and the vehicle can be a fuel vehicle, a gas vehicle or a new energy vehicle. The new energy vehicle can be a pure electric vehicle, a hybrid vehicle or an extended-range vehicle, etc., but is not limited to this. The working part 11 is the vehicle body, and the battery pack 10 is arranged at the bottom of the vehicle body and provides electrical energy support for the driving of the vehicle or the operation of electrical components in the vehicle. However, in some other embodiments, the electronic device 1 can also be a mobile phone, a portable device, a laptop computer, a ship, a spacecraft, an electric toy and an electric tool, etc. Spacecraft include airplanes, rockets, space shuttles and spacecraft, etc.; the working part 11 can be a unit component that can obtain electrical energy from the battery pack 10 and perform corresponding work, such as a fan blade rotation unit, a vacuum cleaner suction unit, etc. Electric toys include fixed or mobile electric toys, such as game consoles, electric car toys, electric boat toys, and electric airplane toys; electric tools include metal cutting tools, grinding tools, assembly tools, and railway tools, such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators, and electric planers. The present embodiment does not impose any particular restrictions on the electronic device 1.

[0065] In the secondary battery of the present invention, the thinner second corrosion-resistant layer located on the inner side of the housing can reduce the amount of deposited material formed by plating shedding during sidewall stretching, alleviate the problem of deposited material piercing the diaphragm, and reduce the risk of thermal runaway. This configuration improves the battery's safety while also providing corrosion resistance on the inner side of the housing. The thicker first corrosion-resistant layer located on the outer side of the housing can reduce the risk of cracking of the outer wall of the housing due to plating shedding, thereby improving the corrosion resistance and rust prevention of the outer wall of the housing. Furthermore, the thicker second corrosion-resistant layer can improve the wear resistance of the outer side of the housing, enabling the housing to adapt to complex external operating conditions. Therefore, the present invention effectively overcomes some practical problems of the prior art and has high utility value and practical significance. The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without violating the spirit and scope of the present invention. Therefore, all equivalent modifications or changes made by those skilled in the art without departing from the spirit and technical ideas disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A secondary battery, characterized in that: include: The shell comprises an end wall and a side wall surrounding the end wall, wherein the side wall and the end wall are integrally formed by stretching; a first corrosion-resistant layer provided on the outer walls of the end wall and the side wall; a second corrosion-resistant layer provided on the inner walls of the end wall and the side wall; Wherein, along the same thickness direction of the shell, the thickness of the first corrosion-resistant layer is greater than the thickness of the second corrosion-resistant layer.

2. The secondary battery according to claim 1, wherein The secondary battery further includes an electrode assembly, which is disposed in the shell. The second corrosion-resistant layer includes a copper plating layer facing the electrode assembly.

3. The secondary battery according to claim 1, wherein The first corrosion-resistant layer includes a first nickel-plated layer, and the second corrosion-resistant layer includes a second nickel-plated layer.

4. The secondary battery according to claim 3, wherein The second corrosion-resistant layer further includes a copper plating layer located on a side of the second nickel plating layer away from the shell.

5. The secondary battery according to claim 3, wherein The thickness of the first nickel plating layer located on the outer side of the end wall is greater than or equal to 4 μm.

6. The secondary battery according to claim 1, wherein The thickness of the first corrosion-resistant layer is in the range of 2 μm to 5 μm.

7. The secondary battery according to claim 6, characterized in that The thickness of the second corrosion-resistant layer is in the range of 1 μm to 2 μm.

8. The secondary battery according to claim 1, wherein The wall thickness of the first corrosion-resistant layer located on the end wall is a, and the wall thickness of the first corrosion-resistant layer located on the side wall is b, wherein 1<a / b<3.

9. A battery pack, characterized in that: A secondary battery comprising the secondary battery according to any one of claims 1 to 8.

10. An electronic device, characterized in that: A battery pack comprising the battery pack according to claim 9.

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