Secondary battery and electric device

Abstract

The invention discloses a secondary battery and electric equipment. The secondary battery comprises a shell, an electrode assembly arranged in the shell and a sealing element for sealing the shell, the shell comprises a first shell body and a second shell body which are arranged in an insulating mode and jointly form a containing cavity, and the containing cavity is filled with electrolyte. The first shell and the second shell are oppositely arranged and have a gap. The first shell comprises a first metal layer and a second metal layer wrapping the surface, away from the containing cavity, of the first metal layer, and the hardness of the second shell and the hardness of the second metal layer are both larger than the hardness of the first metal layer. The anode of the electrode assembly is electrically connected with the first metal layer, and the cathode of the electrode assembly is electrically connected with the second shell. The first metal layer is made of a metal material similar to the positive electrode of the electrode assembly, so that the potential difference between the positive electrode and the first shell can be reduced, and the possibility of electrochemical corrosion of the first shell is reduced. And the hardness of the second metal layer is greater than that of the first metal layer, so that the risk of leakage of the secondary battery caused by breakage of the first shell is reduced.

Description

Technical Field

[0001] This application relates to the technical field of energy storage, and particularly to a secondary battery and an electrical device. Background Art

[0002] Current secondary batteries include steel shell batteries and soft-pack batteries. Generally, both steel shell batteries and soft-pack batteries include a housing and an electrode assembly disposed within the housing. Among them, the housing of the steel shell battery includes a first housing body and a second housing body, and the first housing body and the second housing body are hermetically connected by welding or by a seal. Summary of the Invention

[0003] For the secondary batteries in the prior art, if the first housing body is electrically connected to the positive electrode of the electrode assembly and the second housing body is electrically connected to the negative electrode of the electrode assembly, then the first housing body and the second housing body are not suitable for being hermetically connected by welding but are suitable for being hermetically connected by a seal. In view of this situation, the inventor found that since the positive electrode plate and the negative electrode plate of the electrode assembly are electrode plates made of different metal materials, in order to reduce the potential difference between the positive electrode and the first housing body and reduce the potential difference between the negative electrode and the second housing body, and reduce the possibility of electrochemical corrosion of the housing, generally the first housing body is made of a metal material similar to the positive electrode plate and the second housing body is made of a metal material similar to the negative electrode plate. Different metal materials have different strengths. Compared with the second housing body usually made of stainless steel, the first housing body electrically connected to the positive electrode is usually made of aluminum alloy. The strength of aluminum alloy is weaker than that of stainless steel under conventional thicknesses (the strength of aluminum alloy is similar to that of stainless steel only when the thickness of aluminum alloy exceeds 150 μm at least). When being impacted, the first housing body is easily worn or even broken, resulting in a risk of liquid leakage in the secondary battery.

[0004] In view of the above situation, it is necessary to provide a secondary battery that can reduce the potential difference between the positive electrode and the first housing body, reduce the possibility of electrochemical corrosion of the first housing body, and at the same time improve the strength of the first housing body and reduce the risk of liquid leakage in the secondary battery.

[0005] A first aspect of this application provides a secondary battery, including a housing, an electrode assembly, and a seal. The housing includes a first housing body and a second housing body that are insulated. The first housing body and the second housing body together form a receiving cavity, and the receiving cavity is filled with an electrolyte. The first housing body and the second housing body face each other and have a gap. The first housing body includes a first metal layer and a second metal layer, and the second metal layer covers the surface of the first metal layer away from the receiving cavity. The hardnesses of the second housing body and the second metal layer are both greater than the hardness of the first metal layer. The electrode assembly is disposed within the receiving cavity. The positive electrode of the electrode assembly is electrically connected to the first metal layer, and the negative electrode of the electrode assembly is electrically connected to the second housing body. The seal is disposed around the outer periphery of the first housing body and the second housing body and seals the gap.

[0006] The first metal layer is electrically connected to the positive electrode of the electrode assembly. By making the first metal layer adopt a metal material similar to that of the positive electrode of the electrode assembly, the potential difference between the positive electrode and the first housing can be reduced, which is beneficial to reducing the possibility of electrochemical corrosion of the first housing. The second metal layer covers the surface of the first metal layer away from the receiving cavity, and the hardness of the second metal layer is greater than that of the first metal layer, which can improve the overall hardness of the first housing. When the first housing is impacted, the second metal layer with greater hardness is impacted first, which is beneficial to reducing the risk of leakage of the secondary battery caused by the rupture of the first housing.

[0007] In one or more of the above embodiments, the material of the first metal layer includes at least one of aluminum, zinc, and magnesium, and the materials of the second housing and the second metal layer each include at least one of iron, nickel, chromium, and titanium. This is beneficial to reducing the potential difference between the positive electrode and the first metal layer and is beneficial to improving the hardness of the second housing and the second metal layer.

[0008] In one or more of the above embodiments, the electrode assembly includes a positive electrode tab. The positive electrode tab includes a positive electrode current collector and a positive electrode active material layer. The positive electrode active material layer is provided on two surfaces of the positive electrode current collector that are oppositely arranged along the thickness direction. The positive electrode current collector is provided with a positive electrode tab. The positive electrode current collector and the first metal layer are electrically connected to the positive electrode tab. The materials of the positive electrode tab and the positive electrode current collector are both aluminum foil, and the material of the first metal layer includes aluminum. This is beneficial to further reducing the potential difference between the first housing and the positive electrode of the electrode assembly and further reducing the possibility of electrochemical corrosion of the first housing.

[0009] In one or more of the above embodiments, along the wall thickness direction of the first housing, the thickness of the first metal layer is H 1 , and the thickness of the second metal layer is H 2 , 16μm ≤ H 1 + H 2 ≤ 150μm, H 1 ≥ 6μm, H 2 ≥ 10μm. By setting H 1 ≥ 6μm, the first metal layer can be prevented from being too thin. When the first metal layer is welded, it is beneficial to reducing the risk of the first metal layer being welded through. By setting H 2 ≥ 10μm, the second metal layer can be prevented from being too thin, which is beneficial to improving the impact resistance of the second metal layer. By setting H 1 + H 2 ≤ 150μm, the first housing can be prevented from being too thick, which is beneficial to reducing the loss of the energy density of the secondary battery.

[0010] In one or more of the above embodiments, 23μm ≤ H 1 + H 2 ≤ 120μm, H 1≥8μm, H 2 ≥15μm. By setting H 1 ≥8μm, it is beneficial to further reduce the risk of the first metal layer being welded through. By setting H 2 ≥15μm, it is beneficial to further improve the impact resistance of the second metal layer. By setting H 1 +H 2 ≤120μm, it is beneficial to further reduce the loss of the energy density of the secondary battery.

[0011] In one or more of the above embodiments, the first metal layer includes a first wall and a first sidewall connecting the periphery of the first wall, the second metal layer includes a second wall and a second sidewall connecting the periphery of the second wall, the second housing includes a third wall and a third sidewall connecting the periphery of the third wall, the first wall and the second wall are arranged facing the third wall, the first sidewall and the second sidewall are arranged facing the third sidewall in the thickness direction of the electrode assembly and have a gap, and the seal includes a filling portion filled in the gap. By filling the gap with the filling portion, the encapsulation interface between the seal and the first housing and the second housing can be increased, which is beneficial to improving the sealing performance of the secondary battery. Moreover, by filling the gap with the filling portion, it is also convenient to insulate the first housing and the second housing.

[0012] In one or more of the above embodiments, the filling portion at least covers the surface of the second sidewall facing the gap. When the second metal layer uses a metal material with a relatively high hardness and the first metal layer uses a metal material with a relatively low hardness, the metal materials of the second metal layer and the first metal layer are different. By covering the surface of the second sidewall facing the gap with the filling portion, it is beneficial to reduce the potential difference caused by the first metal layer and the second metal layer coming into contact with the electrolyte simultaneously, thereby reducing the possibility of electrochemical corrosion of the first housing.

[0013] In one or more of the above embodiments, a protective layer is provided on the surfaces of the first sidewall and the second sidewall facing the gap, and the filling portion is provided between the third sidewall and the protective layer. The material of the protective layer includes at least one of polytetrafluoroethylene, polyvinylidene fluoride, epoxy resin, alumina, zirconia, and silicone. By making the protective layer include the above materials and arranging it on the surfaces of the first sidewall and the second sidewall facing the gap, the possibility of the electrolyte eroding the encapsulation interface between the filling portion and the first metal layer and the second metal layer can be reduced, which is beneficial to further reducing the potential difference caused by the first metal layer and the second metal layer coming into contact with the electrolyte simultaneously, thereby reducing the possibility of electrochemical corrosion of the first housing.

[0014] In one or more of the above embodiments, the first metal layer includes an extension portion provided at an end of the first side wall facing the gap. The filling portion is provided between the third side wall and the extension portion, and the extension portion covers the surface of the second side wall facing the gap. By covering the surface of the second side wall facing the gap with the extension portion of the first metal layer, the encapsulation interface between the extension portion and the filling portion becomes the encapsulation interface between the first housing and the filling portion, which can facilitate making the encapsulation interface between the first housing and the filling portion smoother and less vulnerable to electrolyte erosion, and is beneficial to improving the sealing performance of the secondary battery. Moreover, the extension portion can effectively separate the surface of the second side wall facing the gap from the electrolyte, which is beneficial to reducing the potential difference caused by the first metal layer and the second metal layer coming into contact with the electrolyte simultaneously, thereby reducing the possibility of electrochemical corrosion of the first housing.

[0015] In one or more of the above embodiments, the Brinell hardness of the first metal layer is 10 HB to 60 HB, the Brinell hardness of the second housing is 110 HB to 320 HB, and the Brinell hardness of the second metal layer is 110 HB to 320 HB. When the hardness is not too small, it is convenient to prepare the first metal layer, the second metal layer, and the second housing with the required hardness using common metal materials.

[0016] In one or more of the above embodiments, the yield strength of the second metal layer is greater than or equal to 150 Mpa. The relatively large yield strength of the second metal layer is beneficial to improving the ability of the first housing to resist deformation under impact.

[0017] The second aspect of the present application provides an electrical device including the secondary battery of the first aspect of the present application. The electrolyte of the secondary battery is not easily leaked, which is beneficial to extending the service life of the electrical device. Description of the Drawings

[0018] Figure 1 It is a top view of the secondary battery provided by an embodiment of the present application.

[0019] Figure 2 It is a front view of the secondary battery provided by an embodiment of the present application.

[0020] Figure 3 It is an exploded view of the secondary battery provided by an embodiment of the present application.

[0021] Figure 4 It is for the first embodiment of the present application along Figure 1 The sectional view taken along the sectional line A-A.

[0022] Figure 5 It is for the second embodiment of the present application along Figure 1 The sectional view taken along the sectional line A-A.

[0023] Figure 6 It is for the third embodiment of the present application alongFigure 1 Cross-sectional view of the middle cross-section line A-A.

[0024] Figure 7 Overall schematic diagram of the electrical device provided by an embodiment of the present application.

[0025] Description of main component symbols 1000, electrical device; 100, secondary battery; 10, housing; 101, receiving cavity; 11, first housing; 111, first metal layer; 1111, first wall; 1112, first side wall; 1113, extension; 112, second metal layer; 1121, second wall; 1122, second side wall; 12, second housing; 121, third wall; 122, third side wall; 20, electrode assembly; 21, positive electrode tab; 22, negative electrode tab; 23, separator; 30, seal; 301, filling part; 31, first adhesive layer; 32, water-blocking layer; 33, second adhesive layer; 40, positive electrode ear; 50, negative electrode ear; 60, protective layer; 70, fixing member. Detailed implementation manners

[0026] Next, the technical solutions in the embodiments of the present application will be described in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments.

[0027] It should be noted that when an element is considered to be "connected" to another element, it can be directly connected to the other element or there may be an intermediate element. When an element is considered to be "disposed on" another element, it can be directly disposed on the other element or there may be an intermediate element.

[0028] Unless otherwise specified, the term "plurality" used herein refers to two or more.

[0029] The terms "first", "second", etc. are only used to distinguish different objects and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity, specific order or primary-secondary relationship of the indicated technical features.

[0030] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which this application belongs. The terms used in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0031] It should be understood that considering the factors of actual processing tolerances, in the technical solution of the present application, when two components are arranged in parallel / vertical, the included angle between the two components is allowed to have a tolerance within a range of 10% of the included angle corresponding to the parallel / vertical arrangement. In the technical solution of the present application, when two certain parameters are equal, a tolerance within a range of 10% is allowed between the two parameters.

[0032] An embodiment of the present application provides a secondary battery, including a housing, an electrode assembly, and a seal. The housing includes a first housing and a second housing that are insulated from each other. The first housing and the second housing together form a receiving cavity, and an electrolyte is filled in the receiving cavity. The first housing and the second housing face each other and have a gap. The first housing includes a first metal layer and a second metal layer, and the second metal layer covers the surface of the first metal layer away from the receiving cavity. The hardness of both the second housing and the second metal layer is greater than that of the first metal layer. The electrode assembly is disposed in the receiving cavity, the positive electrode of the electrode assembly is electrically connected to the first metal layer, and the negative electrode of the electrode assembly is electrically connected to the second housing. The seal is disposed around the outer periphery of the first housing and the second housing and seals the gap.

[0033] In the secondary battery of the present application, the first metal layer is electrically connected to the positive electrode of the electrode assembly. By making the first metal layer adopt a metal material similar to that of the positive electrode of the electrode assembly, the potential difference between the positive electrode and the first housing can be reduced, which is beneficial to reducing the possibility of electrochemical corrosion of the first housing. The second metal layer covers the surface of the first metal layer away from the receiving cavity and the hardness of the second metal layer is greater than that of the first metal layer, which can improve the overall hardness of the first housing. When the first housing is impacted, the harder second metal layer is impacted first, which is beneficial to reducing the risk of leakage of the secondary battery caused by the rupture of the first housing.

[0034] Some embodiments of the present application will be described below in conjunction with the accompanying drawings. Without conflict, the following embodiments and the features in the embodiments can be combined with each other.

[0035] Please refer to Figures 1 to 3 , an embodiment of the present application provides a secondary battery 100, including a housing 10, an electrode assembly 20, and a seal 30. The housing 10 includes a first housing 11 and a second housing 12 that are insulated from each other. The first housing 11 and the second housing 12 face each other and have a gap. The first housing 11 and the second housing 12 together form a receiving cavity 101 (refer to Figure 4 ), an electrolyte is filled in the receiving cavity 101, the electrode assembly 20 is disposed in the receiving cavity 101, and the seal 30 is disposed around the outer periphery of the first housing 11 and the second housing 12 and seals the gap.

[0036] The housing 10 is a metal housing, please refer to Figure 3, wherein the first housing 11 includes a first metal layer 111 and a second metal layer 112, and the second metal layer 112 covers the surface of the first metal layer 111 away from the receiving cavity 101. The positive electrode of the electrode assembly 20 is electrically connected to the first metal layer 111, and the negative electrode of the electrode assembly 20 is electrically connected to the second housing 12. It can be understood that since the second metal layer 112 covers the surface of the first metal layer 111 away from the receiving cavity 101, the positive electrode of the electrode assembly 20 is also electrically connected to the second metal layer 112. The first metal layer 111 can be made of a metal material similar to that of the positive electrode of the electrode assembly 20 to reduce the potential difference between the positive electrode and the first housing 11, which is beneficial to reducing the possibility of electrochemical corrosion of the first housing 11.

[0037] In some embodiments, the hardness of the second metal layer 112 is greater than that of the first metal layer 111, which can improve the overall hardness of the first housing 11. When the first housing 11 is impacted, the second metal layer 112 with a greater hardness covering the outer periphery of the first metal layer 111 is impacted first, which is beneficial to reducing the risk of leakage of the secondary battery 100 caused by the rupture of the first housing 11. In some embodiments, the hardness of the second housing 12 is greater than that of the first metal layer 111.

[0038] In some embodiments, the Brinell hardness of the first metal layer 111 is 10 HB to 60 HB. For example, the Brinell hardness of the first metal layer 111 is 10 HB, 20 HB, 30 HB, 40 HB, 50 HB, 60 HB, or any value between the listed end point values. The Brinell hardness of the second metal layer 112 is 110 HB to 320 HB. For example, the Brinell hardness of the second metal layer 112 is 110 HB, 150 HB, 200 HB, 250 HB, 320 HB, or any value between the listed end point values. The Brinell hardness of the second housing 12 is 110 HB to 320 HB. For example, the Brinell hardness of the second housing 12 is 110 HB, 150 HB, 200 HB, 250 HB, 320 HB, or any value between the listed end point values. When the hardness is not too small, it is convenient to prepare the first metal layer 111, the second metal layer 112, and the second housing 12 with the required hardness through common metal materials.

[0039] In some embodiments, the material of the first metal layer 111 includes at least one of aluminum, zinc, and magnesium, the material of the second metal layer 112 includes at least one of iron, nickel, chromium, and titanium, and the material of the second housing 12 includes at least one of iron, nickel, chromium, and titanium.

[0040] In some embodiments, the yield strength of the second metal layer 112 is greater than or equal to 150 Mpa. For example, the yield strength of the second metal layer 112 is 150 Mpa, 200 Mpa, 250 Mpa, 300 Mpa, or other achievable yield strength values. The relatively high yield strength of the second metal layer 112 is beneficial to improving the ability of the first housing 11 to resist deformation under impact.

[0041] In some embodiments, along the wall thickness direction of the first housing 11, the thickness of the first metal layer 111 is H 1 , and the thickness of the second metal layer 112 is H 2 , 16μm ≤ H 1 + H 2 ≤ 150μm, H 1 ≥ 6μm, H 2 ≥ 10μm. It is not difficult to obtain that H 1 ≤ 140μm and H 2 ≤ 144μm. For example, the value of H 1 + H 2 is 16μm, 23μm, 30μm, 50μm, 120μm, 150μm, or any value between the listed endpoint values, the value of H 1 is 6μm, 8μm, 30μm, 50μm, 105μm, 140μm, or any value between the listed endpoint values, and the value of H 2 is 10μm, 15μm, 30μm, 50μm, 112μm, 144μm, or any value between the listed endpoint values, where, limited by H 1 + H 2 ≤ 150μm, H 1 and H 2 do not simultaneously take the maximum value. By setting H 1 ≥ 6μm, it can be ensured that the first metal layer 111 is not too thin, which is beneficial to reducing the risk of the first metal layer 111 being welded through when the first metal layer 111 is welded. By setting H 2 ≥ 10μm, it can be ensured that the second metal layer 112 is not too thin, which is beneficial to improving the ability of the second metal layer 112 to resist impact. By setting H 1 + H 2 ≤ 150μm, it can be ensured that the first housing 11 is not too thick, which is beneficial to reducing the loss of the energy density of the secondary battery 100.

[0042] In some embodiments, 23μm ≤ H 1 + H 2 ≤ 120μm, H 1 ≥ 8μm, H 2 ≥ 15μm. Wherein, limited by H 1 + H2 ≤120μm, H 1 and H 2 Do not simultaneously take the maximum value. By setting H 1 ≥8μm, it is beneficial to further reduce the risk of the first metal layer 111 being welded through. By setting H 2 ≥15μm, it is beneficial to further improve the impact resistance of the second metal layer 112. By setting H 1 +H 2 ≤120μm, it is beneficial to further reduce the loss of the energy density of the secondary battery 100.

[0043] Please refer to Figures 4 to 6 , in some embodiments, the first metal layer 111 includes a first wall 1111 and a first side wall 1112 connecting the periphery of the first wall 1111. The positive electrode of the electrode assembly 20 can be electrically connected to the first wall 1111 or the first side wall 1112. The first side wall 1112 can be perpendicular or inclined to the first wall 1111, and the present application does not limit this. The second metal layer 112 includes a second wall 1121 and a second side wall 1122 connecting the periphery of the second wall 1121. The second wall 1121 covers the surface of the first wall 1111 away from the receiving cavity 101, and the second side wall 1122 covers the surface of the first side wall 1112 away from the receiving cavity 101. The second side wall 1122 can be perpendicular or inclined to the second wall 1121, and the present application does not limit this. The second housing 12 includes a third wall 121 and a third side wall 122 connecting the periphery of the third wall 121. The negative electrode of the electrode assembly 20 can be electrically connected to the third wall 121 or the third side wall 122. The third side wall 122 can be perpendicular or inclined to the third wall 121, and the present application does not limit this. Along the thickness direction of the electrode assembly 20, the first wall 1111 and the second wall 1121 are arranged facing the third wall 121, and the first side wall 1112 and the second side wall 1122 are arranged facing the third side wall 122 with a gap.

[0044] Please refer to Figures 4 to 6 , the electrode assembly 20 includes a positive electrode tab 21, a negative electrode tab 22, and a separator 23. The positive electrode tab 21 is electrically connected to the first metal layer 111, the negative electrode tab 22 is electrically connected to the second housing 12, the separator 23 separates the positive electrode tab 21 and the negative electrode tab 22, and the separator 23 is a film material such as a polyethylene film, a polypropylene film, a polyester film, or a polyimide film that can provide insulation.

[0045] Please refer to Figures 4 to 6In some embodiments, the electrode assembly 20 is a stacked structure, a plurality of positive electrode sheets 21 and a plurality of negative electrode sheets 22 are alternately stacked, and the separator 23 is disposed between any adjacent positive electrode sheets 21 and negative electrode sheets 22. In some embodiments, the electrode assembly 20 is a stacked structure, one of the positive electrode sheets 21 and the negative electrode sheets 22 is continuously folded in a "Z" shape, and the other is disposed between any two adjacent folded layers of the "Z" shape, and the separator 23 is disposed between any adjacent positive electrode sheets 21 and negative electrode sheets 22. In some embodiments, the electrode assembly 20 is a winding structure, a single positive electrode sheet 21 and a single negative electrode sheet 22 are stacked and wound, and the separator 23 is disposed between the positive electrode sheet 21 and the negative electrode sheet 22.

[0046] In some embodiments, the positive electrode sheet 21 includes a positive electrode current collector and a positive electrode active material layer, the positive electrode active material layer is arranged on two surfaces of the positive electrode current collector that are arranged opposite to each other in the thickness direction, and the first metal layer 111 is electrically connected to the positive electrode current collector. In some embodiments, the positive electrode current collector is provided with an empty foil area, and the first metal layer 111 is connected to the empty foil area of ​​the positive electrode current collector. For example, the first wall 1111 is directly connected to the empty foil area of ​​the positive electrode current collector. For another example, the first wall 1111 is indirectly connected to the empty foil area of ​​the positive electrode current collector through a first conductive member (not shown), and the first conductive member includes but is not limited to conductive protrusions, metal springs, and conductive adhesives. The conductive protrusions can be formed by laser roughening the first wall 1111. In some embodiments, the positive electrode current collector is provided with a positive electrode tab 40, and the positive electrode current collector and the first metal layer 111 are electrically connected to the positive electrode tab 40, for example, the positive electrode current collector and the first side wall 1112 are electrically connected to the positive electrode tab 40. When there are multiple positive electrode tabs 40 , the multiple positive electrode tabs 40 can be stacked and gathered to form a positive electrode tab bundle and then welded to the first metal layer 111 .

[0047] In some embodiments, the material of the positive electrode current collector includes at least one of aluminum, nickel, tantalum, and titanium. In some embodiments, the positive electrode tab 40 and the positive electrode current collector are both made of aluminum foil, and the material of the first metal layer 111 includes aluminum. This is beneficial to further reduce the potential difference between the first housing 11 and the positive electrode of the electrode assembly 20, and further reduce the possibility of electrochemical corrosion of the first housing 11.

[0048] In some embodiments, the negative electrode sheet 22 includes a negative electrode current collector and a negative electrode active material layer, the negative electrode active material layer is disposed on two surfaces of the negative electrode current collector that are disposed oppositely in the thickness direction, and the second shell 12 is electrically connected to the negative electrode current collector. In some embodiments, the negative electrode current collector is provided with an empty foil area, and the third wall 121 of the second shell 12 is connected to the empty foil area of ​​the negative electrode current collector. For example, the third wall 121 is directly connected to the empty foil area of ​​the negative electrode current collector. For another example, the third wall 121 is indirectly connected to the empty foil area of ​​the negative electrode current collector through a second conductive member (not shown), and the second conductive member includes but is not limited to conductive protrusions, metal springs, and conductive adhesive. In some embodiments, the negative electrode current collector is provided with a negative electrode tab 50, and the negative electrode current collector and the second shell 12 are electrically connected to the negative electrode tab 50. When the number of negative electrode tabs 50 is multiple, the multiple negative electrode tabs 50 can be stacked and gathered to form a negative electrode tab bundle and then welded to the second shell 12.

[0049] In some embodiments, the negative electrode current collector is made of at least one of copper, nickel, tantalum, and titanium, and the second housing 12 is made of stainless steel.

[0050] See also Figures 4 to 6 In some embodiments, the seal 30 includes a filling portion 301 filled in the gap between the first side wall 1112 and the second side wall 1122 and the third side wall 122, and the filling portion 301 is an insulator. The filling portion 301 fills the gap to increase the packaging interface between the seal 30 and the first shell 11 and the second shell 12, which is beneficial to improve the sealing of the secondary battery 100. In addition, the filling portion 301 fills the gap to facilitate the insulation setting of the first shell 11 and the second shell 12.

[0051] See also Figure 4 In some embodiments, the filling portion 301 at least covers the surface of the second side wall 1122 facing the gap. When the second metal layer 112 is made of a metal material with a relatively high hardness and the first metal layer 111 is made of a metal material with a relatively low hardness, the second metal layer 112 is made of a different metal material from the first metal layer 111. Covering the surface of the second side wall 1122 facing the gap by the filling portion 301 helps to reduce the possibility of the first metal layer 111 and the second metal layer 112 being in contact with the electrolyte at the same time and generating a potential difference, thereby causing electrochemical corrosion of the first shell 11. In some embodiments, the filling portion 301 also covers the surface of the first side wall 1112 facing the gap, so as to reduce the possibility of the first metal layer 111 and the second metal layer 112 being in contact with the electrolyte at the same time by exposing the surface of the second side wall 1122 facing the gap.

[0052] See also Figure 5, in some embodiments, a protective layer 60 is provided on the surfaces of the first sidewall 1112 and the second sidewall 1122 facing the gap, and the filling portion 301 is disposed between the third sidewall 122 and the protective layer 60. The protective layer 60 can be a polymer coating (such as a polytetrafluoroethylene coating, a polyvinylidene fluoride coating, an epoxy resin coating) or a ceramic coating (such as an alumina coating, a zirconia coating, a silicone coating), etc. The material of the protective layer 60 includes at least one of polytetrafluoroethylene, polyvinylidene fluoride, epoxy resin, alumina, zirconia, and silicone. By making the protective layer 60 include the above materials and disposing it on the surfaces of the first sidewall 1112 and the second sidewall 1122 facing the gap, the possibility of the electrolyte eroding the encapsulation interface between the filling portion 301 and the first metal layer 111 and the second metal layer 112 can be reduced, which is beneficial to further reducing the potential difference caused by the first metal layer 111 and the second metal layer 112 coming into contact with the electrolyte simultaneously, and reducing the possibility of the first housing 11 undergoing electrochemical corrosion.

[0053] In some embodiments, along the assembly direction of the first housing 11 and the second housing 12, the thickness of the protective layer 60 is 2 μm to 500 μm. Preferably, the thickness of the protective layer 60 is 5 μm to 200 μm. The thickness of the protective layer 60 is not too small, which is beneficial to improving the ability of the protective layer 60 to resist electrolyte erosion. The thickness of the protective layer 60 is not too large, which is beneficial to reducing the loss of the energy density of the secondary battery 100.

[0054] Please refer to Figure 6 , in some embodiments, the first metal layer 111 includes an extension portion 1113, and the extension portion 1113 is disposed at the end of the first sidewall 1112 facing the gap. The filling portion 301 is disposed between the third sidewall 122 and the extension portion 1113, and the extension portion 1113 covers the surface of the second sidewall 1122 facing the gap. Compared with the encapsulation interface between the first sidewall 1112 and the filling portion 301 and the encapsulation interface between the second sidewall 1122 and the filling portion 301 together being the encapsulation interface between the first housing 11 and the filling portion 301, along the assembly direction of the first housing 11 and the second housing 12, a step difference is likely to be formed between the first sidewall 1112 and the second sidewall 1122. At this time, the encapsulation interface between the first housing 11 and the filling portion 301 is likely to be uneven. By making the extension portion 1113 of the first metal layer 111 cover the surface of the second sidewall 1122 facing the gap, such that the encapsulation interface between the extension portion 1113 and the filling portion 301 is the encapsulation interface between the first housing 11 and the filling portion 301, it is possible to facilitate making the encapsulation interface between the first housing 11 and the filling portion 301 more flat and not easily eroded by the electrolyte, which is beneficial to improving the sealing performance of the secondary battery 100. Moreover, through the extension portion 1113, the surface of the second sidewall 1122 facing the gap can be effectively separated from the electrolyte, which is beneficial to reducing the potential difference caused by the first metal layer 111 and the second metal layer 112 coming into contact with the electrolyte simultaneously, and reducing the possibility of the first housing 11 undergoing electrochemical corrosion.

[0055] Please refer to Figures 4 to 6 Figures 4 to 6 , in some embodiments, the seal 30 includes a first adhesive layer 31, the first adhesive layer 31 is adhered to the outer peripheries of the second side wall 1122 and the third side wall 122, and the filling portion 301 is connected to the first adhesive layer 31. Adhering the first adhesive layer 31 to the second side wall 1122 and the third side wall 122 is beneficial to improving the bonding stability between the seal 30 and the housing 10.

[0056] In some embodiments, the filling portion 301 and the first adhesive layer 31 are integrally provided. The filling portion 301 can be directly formed after a part of the first adhesive layer 31 melts and enters the gap between the first side wall 1112, the second side wall 1122 and the third side wall 122 and then cools down. This can make the assembly process of the secondary battery 100 more convenient and is beneficial to simplifying the manufacturing process flow of the secondary battery 100. Moreover, the filling portion 301 and the first adhesive layer 31 being integrally provided can fully fit the gap between the first side wall 1112, the second side wall 1122 and the third side wall 122, which is beneficial to improving the sealing performance of the seal 30 for the first housing 11 and the second housing 12. In some other embodiments, the filling portion 301 and the first adhesive layer 31 are separately provided.

[0057] In some embodiments, the first adhesive layer 31 can be melted or lose adhesion by heat and constitutes a part of the pressure relief channel communicating with the accommodation cavity 101. When the secondary battery 100 undergoes thermal runaway, the melting or loss of adhesion of the first adhesive layer 31 can timely relieve the pressure of the accommodation cavity 101, which is beneficial to improving the safety of the secondary battery 100.

[0058] In some embodiments, the melting point of the first adhesive layer 31 is 95°C to 130°C. For example, the melting point of the first adhesive layer 31 is 95°C, 100°C, 110°C, 130°C or any value within the range between the listed endpoint values or any value between the listed endpoint values. By setting the melting point of the first adhesive layer 31 to be 95°C to 130°C, the possibility of the first adhesive layer 31 melting or losing adhesion in advance before the secondary battery 100 undergoes thermal runaway can be reduced, which is beneficial to maintaining the sealing effect of the seal 30 on the housing 10. And it can ensure that the first adhesive layer 31 melts or loses adhesion in time to relieve the pressure of the accommodation cavity 101 when the secondary battery 100 undergoes thermal runaway, which is beneficial to improving the safety of the secondary battery 100. It should be understood that when the filling portion 301 and the first adhesive layer 31 are integrally provided and the filling portion 301 is directly formed after a part of the first adhesive layer 31 melts and enters the gap between the first side wall 1112, the second side wall 1122 and the third side wall 122 and then cools down, the melting point of the filling portion 301 is basically the same as that of the first adhesive layer 31. When the secondary battery 100 undergoes thermal runaway, it is convenient to make the first adhesive layer 31 and the filling portion 301 melt or lose adhesion in time to relieve the pressure of the accommodation cavity 101, which is beneficial to reducing the risk of contact short circuit between the first housing 11 and the second housing 12.

[0059] In some embodiments, the material of the first adhesive layer 31 includes a polymer resistant to electrolyte, and the polymer of the first adhesive layer 31 includes at least one of polyolefin, fluororubber and polyurethane. Among them, polyolefin may include polypropylene and polyethylene, etc., so that the first adhesive layer 31 has a high resistance to electrolyte corrosion. In some embodiments, the first adhesive layer 31 includes a single layer or multiple layers of polymer.

[0060] See also Figures 4 to 6 In some embodiments, the seal 30 includes a water-blocking layer 32, and the water-blocking layer 32 is arranged on the side of the first adhesive layer 31 away from the housing 10. The material of the water-blocking layer 32 includes at least one of steel, aluminum, nickel, silver, copper, and alloys thereof. By making the material of the water-blocking layer 32 include the above materials, the water-blocking property of the water-blocking layer 32 can be better than the water-blocking property of the first adhesive layer 31, which is conducive to improving the sealing property of the seal 30 to the first shell 11 and the second shell 12. Among them, the water-blocking layer 32 is insulated from the second side wall 1122 and the third side wall 122 by the first adhesive layer 31. In some embodiments, the water-blocking layer 32 is a single-layer or multi-layer structure. For example, the multi-layer structure is a steel layer plus an aluminum layer or a nickel layer plus a copper layer.

[0061] See also Figures 4 to 6 In some embodiments, the seal 30 includes a second adhesive layer 33, which is disposed on a side of the water-blocking layer 32 away from the first adhesive layer 31. The second adhesive layer 33 can protect the water-blocking layer 32, which helps to reduce the risk of failure of the water-blocking layer 32 due to damage.

[0062] In some embodiments, the melting point of the second adhesive layer 33 is greater than the melting point of the first adhesive layer 31. In some embodiments, the difference in melting point between the second adhesive layer 33 and the first adhesive layer 31 is greater than 10°C.

[0063] In some embodiments, the melting point of the second glue layer 33 is 140° C. to 500° C. For example, the melting point of the second glue layer 33 is 140° C., 160° C., 200° C., 250° C., 300° C., 500° C., or any value between the listed endpoints.

[0064] In some embodiments, the material of the second adhesive layer 33 includes a polymer resistant to electrolyte, and the polymer of the second adhesive layer 33 includes at least one of polyolefin, fluoropolymer, polyetheretherketone, fluororubber and polyurethane. Among them, polyolefin may include polypropylene and polyethylene, etc., and fluoropolymer may be polytetrafluoroethylene, etc., so that the second adhesive layer 33 has a higher resistance to electrolyte corrosion. In some embodiments, the second adhesive layer 33 includes a single layer or multiple layers of polymer.

[0065] It should be understood that when the seal 30 includes the first glue layer 31, the water blocking layer 32 and the second glue layer 33 at the same time, along the thickness direction of the water blocking layer 32, the first glue layer 31 and the second glue layer 33 are respectively arranged on both sides of the water blocking layer 32. In some embodiments, the first glue layer 31 and the water blocking layer 32, and the second glue layer 33 and the water blocking layer 32 are fixed by gluing, so that the first glue layer 31, the water blocking layer 32 and the second glue layer 33 are compounded into a whole. In some embodiments, the first glue layer 31 and the water blocking layer 32, and the second glue layer 33 and the water blocking layer 32 are fixed by hot pressing, so that the first glue layer 31, the water blocking layer 32 and the second glue layer 33 are compounded into a whole. During the long-term use of the secondary battery 100, it is beneficial to maintain the sealing performance of the seal 30 to the first shell 11 and the second shell 12.

[0066] In some embodiments, along the thickness direction of the sealing member 30, the thickness of the first adhesive layer 31 is d 1 , the thickness of the water-blocking layer 32 is d 2 , the thickness of the second adhesive layer 33 is d 3 , 7μm≤d 1 ≤500μm, 7μm≤d 2 ≤250μm, 6μm≤d 3 ≤500μm. For example, d 1 7μm, 10μm, 20μm, 50μm, 100μm, 200μm, 500μm or any value between the listed endpoints, d 2 7μm, 10μm, 20μm, 50μm, 100μm, 150μm, 250μm or any value between the listed endpoints, d 3 6μm, 8μm, 20μm, 50μm, 100μm, 200μm, 500μm or any value between the listed endpoints. By setting 7μm≤d 1 、7μm≤d 2 and 6μm≤d 3 , the first adhesive layer 31, the water-blocking layer 32 and the second adhesive layer 33 are not too thin, which is beneficial to reduce the risk of the first adhesive layer 31 being corroded and failing by the electrolyte, and is beneficial to reduce the risk of the second adhesive layer 33 being damaged after the secondary battery 100 falls, resulting in the water-blocking layer 32 being damaged and failing or the water-blocking layer 32 being corroded and failing. By setting d 1 ≤500μm, d 2 ≤250μm and d 3 ≤500 μm, the first adhesive layer 31 , the water-blocking layer 32 and the second adhesive layer 33 are not too thick, which is beneficial to improving the energy density of the secondary battery 100 .

[0067] In some embodiments, 10 μm ≤ d 1 ≤200μm, 10μm≤d2 ≤150μm, 8μm≤d 3 ≤200μm. By setting 10μm≤d 1 、10μm≤d 2 and 8μm≤d 3 , which can make the first glue layer 31, the water-blocking layer 32 and the second glue layer 33 thicker, which is beneficial to further reduce the risk of the first glue layer 31 being corroded by the electrolyte and failing, and is beneficial to further reduce the risk of the second glue layer 33 being damaged after the secondary battery 100 falls, resulting in the water-blocking layer 32 being damaged or the water-blocking layer 32 being corroded and failing. 1 ≤200μm, d 2 ≤150μm and d 3 ≤200μm, the energy density of the secondary battery 100 can be further improved while the thickness of the first glue layer 31 basically meets the requirement of not being corroded by the electrolyte, the thickness of the second glue layer 33 meets the requirement of most falling conditions, and the thickness of the water-blocking layer 32 basically meets the requirement of not being damaged or corroded.

[0068] In some embodiments, the thickness of the first adhesive layer 31 may be uniform or non-uniform. In some embodiments, the thickness of the water-blocking layer 32 may be uniform or non-uniform. In some embodiments, the thickness of the second adhesive layer 33 may be uniform or non-uniform. In some embodiments, the thickness of the seal 30 may be uniform or non-uniform, and the thickness of the seal 30 is equal to the sum of the thicknesses of the first adhesive layer 31, the water-blocking layer 32, and the second adhesive layer 33.

[0069] See also Figures 4 to 6 In some embodiments, the secondary battery 100 further includes a fixing member 70, which bonds the outer shell 10 and the electrode assembly 20, thereby reducing the risk of the electrode assembly 20 moving in the receiving cavity 101, resulting in the first shell 11 and / or the second shell 12 being peeled off from the sealing member 30. In some embodiments, along the thickness direction of the electrode assembly 20, the fixing member 70 is disposed between the outer shell 10 and the electrode assembly 20, for example, the fixing member 70 is disposed between the first metal layer 111 and the electrode assembly 20. In some embodiments, the fixing member 70 is a hot melt adhesive.

[0070] See also Figure 7 One embodiment of the present application provides an electric device 1000, comprising the secondary battery 100 as described above. The electrolyte of the secondary battery 100 is not easy to leak, which is conducive to extending the service life of the electric device 1000. The electric device 1000 includes but is not limited to electronic devices such as e-book players, mobile phones, fax machines, copiers, printers, headphones, video recorders, LCD TVs, recorders, radios, cameras, tablet computers, and laptop computers.

[0071] In addition, those of ordinary skill in the art should recognize that the above embodiments are only used to illustrate the present application and are not intended to limit the present application. As long as appropriate changes and variations are made to the above embodiments within the substantial scope of the present application, they fall within the scope disclosed by the present application.

Claims

1. A secondary battery, characterized in that: include: The housing comprises a first shell and a second shell which are insulated, the first shell and the second shell together forming a receiving cavity, the receiving cavity being filled with electrolyte; the first shell and the second shell are arranged facing each other with a gap; the first shell comprises a first metal layer and a second metal layer, the second metal layer is coated on a surface of the first metal layer away from the receiving cavity, and the hardness of the second shell and the second metal layer is greater than the hardness of the first metal layer; an electrode assembly, disposed in the receiving cavity; a positive electrode of the electrode assembly is electrically connected to the first metal layer, and a negative electrode of the electrode assembly is electrically connected to the second shell; The sealing member is disposed around the outer periphery of the first shell and the second shell and seals the gap.

2. The secondary battery according to claim 1, characterized in that: The material of the first metal layer includes at least one of aluminum, zinc and magnesium, and the material of the second shell and the second metal layer includes at least one of iron, nickel, chromium and titanium.

3. The secondary battery according to claim 2, characterized in that: The electrode assembly includes a positive electrode plate, which includes a positive electrode collector and a positive electrode active material layer, wherein the positive electrode active material layer is arranged on two surfaces of the positive electrode collector that are arranged opposite to each other along the thickness direction; the positive electrode collector is provided with a positive electrode tab, the positive electrode collector and the first metal layer are electrically connected to the positive electrode tab, the positive electrode tab and the positive electrode collector are both made of aluminum foil, and the first metal layer is made of aluminum.

4. The secondary battery according to claim 2, characterized in that: Along the wall thickness direction of the first shell, the thickness of the first metal layer is H1, the thickness of the second metal layer is H2, 16 μm≤H1+H2≤150 μm, H1≥6 μm, H2≥10 μm.

5. The secondary battery according to claim 4, characterized in that: 23μm≤H1+H2≤120μm, H1≥8μm, H2≥15μm.

6. The secondary battery according to claim 1, characterized in that: The first metal layer includes a first wall and a first side wall connected to the periphery of the first wall, the second metal layer includes a second wall and a second side wall connected to the periphery of the second wall, the second shell includes a third wall and a third side wall connected to the periphery of the third wall, the first wall and the second wall are arranged opposite to the third wall, the first side wall and the second side wall are arranged opposite to the third side wall along the thickness direction of the electrode assembly and have the gap; the sealing member includes a filling portion filled in the gap.

7. The secondary battery according to claim 6, characterized in that: The filling portion at least covers a surface of the second side wall facing the gap.

8. The secondary battery according to claim 7, characterized in that: A protective layer is provided on the surfaces of the first side wall and the second side wall facing the gap, and the filling part is provided between the third side wall and the protective layer; the material of the protective layer includes at least one of polytetrafluoroethylene, polyvinylidene fluoride, epoxy resin, aluminum oxide, zirconium oxide and silicone.

9. The secondary battery according to claim 6, characterized in that: The first metal layer includes an extension portion, which is disposed at an end portion of the first side wall facing the gap; the filling portion is disposed between the third side wall and the extension portion, and the extension portion covers a surface of the second side wall facing the gap.

10. The secondary battery according to any one of claims 1 to 9, characterized in that: The Brinell hardness of the first metal layer is 10HB to 60HB, the Brinell hardness of the second shell is 110HB to 320HB, and the Brinell hardness of the second metal layer is 110HB to 320HB.

11. The secondary battery according to any one of claims 1 to 9, characterized in that: The yield strength of the second metal layer is greater than or equal to 150 MPa.

12. An electrical equipment, characterized in that: The invention comprises the secondary battery according to any one of claims 1 to 11.

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