Secondary battery and electronic device

Abstract

The invention relates to a secondary battery and electronic equipment, the secondary battery comprises an electrode assembly and a shell, the electrode assembly is accommodated in the shell, and the electrode assembly comprises a positive pole piece, a diaphragm and a negative pole piece. The shell comprises a first wall and a second wall which are oppositely arranged in the thickness direction of the electrode assembly, and a bonding piece is bonded to the surface, facing the first wall, of the electrode assembly in the thickness direction of the electrode assembly. The shell comprises a first polymer layer, a first bonding layer and a metal layer which are stacked in sequence, and the first polymer layer is located between the first bonding layer and the electrode assembly. The first polymer layer of the first wall is provided with an opening, the projection of the electrode assembly covers the projection of the opening in the thickness direction of the electrode assembly, and the projection of the opening covers the projection of the bonding piece. Part of the bonding piece is located in the opening. According to the invention, the energy density of the secondary battery can be improved.

Description

Technical Field

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

[0002] Secondary batteries, as power sources for electronic devices, are crucial for ensuring their proper function. Due to space constraints within electronic devices, secondary batteries are limited in size and capacity, leading to bottlenecks in their performance. However, end users continue to demand higher power levels from secondary batteries, which translates to higher energy density. Summary of the Invention

[0003] The inventors of this application have discovered that an adhesive is typically provided between the electrode assembly and the housing, allowing the electrode assembly to be restrained to the housing and reducing the possibility of the electrode assembly moving within the housing during a drop of the secondary battery. The housing typically includes a metal layer and a polymer layer disposed on opposite surfaces of the metal layer. By providing an opening in the polymer layer of the housing facing the electrode assembly, with the adhesive portion positioned within the opening, the possibility of the adhesive occupying additional space in the thickness direction of the electrode assembly can be reduced. Given a given thickness of the secondary battery, the thickness of the electrode assembly can be increased, thereby improving the energy density of the secondary battery.

[0004] The purpose of this application is to provide a secondary battery and an electronic device, aiming to improve the energy density of the secondary battery.

[0005] According to a first aspect of the present application, a secondary battery is provided, comprising an electrode assembly and a shell, wherein the electrode assembly is housed in the shell, and the electrode assembly comprises a positive electrode sheet, a separator and a negative electrode sheet. The shell comprises a first wall and a second wall arranged opposite to each other along the thickness direction of the electrode assembly, and an adhesive is adhered to the surface of the electrode assembly facing the first wall along the thickness direction of the electrode assembly. The shell comprises a first polymer layer, a first adhesive layer and a metal layer stacked in sequence, and the first polymer layer is located between the first adhesive layer and the electrode assembly. The first polymer layer of the first wall is provided with an opening, and along the thickness direction of the electrode assembly, the projection of the electrode assembly covers the projection of the opening, and the projection of the opening covers the projection of the adhesive. Part of the adhesive is located within the opening.

[0006] In the above technical solution, the electrode assembly is housed within a housing, which includes a first wall and a second wall disposed oppositely along the thickness direction of the electrode assembly. An adhesive is disposed between the first wall and the electrode assembly, allowing the electrode assembly to be restrained within the housing. This reduces the possibility of the electrode assembly moving within the housing during a drop of the secondary battery, thereby improving the safety performance of the secondary battery. The housing includes a first polymer layer, a first adhesive layer, and a metal layer stacked in sequence. The first polymer layer is located between the first adhesive layer and the electrode assembly. The first polymer layer of the first wall is provided with an opening. By providing a projection of the electrode assembly covering the projection of the opening, the risk of a portion of the electrode assembly being located within the opening and short-circuiting with the metal layer can be reduced. By providing a projection of the opening covering the projection of the adhesive, with a portion of the adhesive located within the opening, the possibility of the adhesive occupying additional space in the thickness direction of the electrode assembly can be reduced, thereby reducing the thickness of the secondary battery. Given a given thickness, the thickness of the electrode assembly can be increased, thereby improving the energy density of the secondary battery.

[0007] In some preferred embodiments, along the thickness direction of the electrode assembly, the projection of the negative electrode sheet covers the projection of the opening, which can reduce the risk of short circuit between the electrode assembly and the metal layer.

[0008] In some preferred embodiments, along the thickness direction of the electrode assembly, the projection of the positive electrode sheet covers the projection of the opening, which can reduce the risk of short circuit between the electrode assembly and the metal layer.

[0009] In some preferred embodiments, along the thickness direction of the electrode assembly, the two opposite surfaces of the adhesive are respectively bonded to the electrode assembly and the first adhesive layer. Since the first adhesive layer has adhesive properties, the adhesive has a good bonding effect with the first adhesive layer, which can enhance the restraining effect of the adhesive on the electrode assembly and reduce the possibility of the electrode assembly moving in the shell. Compared with the case where the two opposite surfaces of the adhesive are respectively bonded to the electrode assembly and the first polymer layer, the case where the two opposite surfaces of the adhesive are respectively bonded to the electrode assembly and the first adhesive layer has a better restraining effect on the electrode assembly.

[0010] In some preferred embodiments, along a first direction, the distance between the electrode assembly and the housing is T1, and the distance between the adhesive and the wall of the opening is T2, where T2 ≤ T1. When the electrode assembly moves within the housing, the wall of the opening can block the adhesive, thereby reducing the possibility of movement of the electrode assembly. The first direction is perpendicular to the thickness of the electrode assembly.

[0011] In some preferred embodiments, the thickness of the first polymer layer is H1, the thickness of the adhesive is H2, and H1≤H2. When H1≤H2, the opening in the thickness direction of the electrode assembly can be completely filled by the adhesive, that is, the space of the opening in the thickness direction of the electrode assembly can be completely utilized, the thickness of the secondary battery can be reduced, and thus the volume energy density improvement rate of the secondary battery can be increased. In addition, the surface of the adhesive facing away from the electrode assembly can be bonded to the first adhesive layer, which can enhance the binding effect of the adhesive on the electrode assembly. When H1 is further increased so that H1>H2, the opening in the thickness direction of the electrode assembly cannot be completely filled by the adhesive, that is, the space of the opening in the thickness direction of the electrode assembly cannot be completely utilized. In this case, the increased thickness of H1 increases the thickness of the secondary battery, thereby reducing the volume energy density improvement rate of the secondary battery. In addition, the surface of the adhesive facing away from the electrode assembly is difficult to bond to the first adhesive layer, thereby reducing the binding effect of the adhesive on the electrode assembly.

[0012] In some preferred embodiments, the thickness of the first polymer layer is H1, which is characterized in that 10μm≤H1≤50μm. When H1 is less than 10μm, in the non-opening area, the first polymer layer has a poor insulation effect on the electrode assembly and the metal layer, and the electrode assembly and the metal layer are prone to short circuit, so the side voltage of the secondary battery will increase and the metal layer will be easily corroded. By setting H1≥10μm, the insulation effect of the first polymer layer on the electrode assembly and the metal layer can be improved, thereby reducing the side voltage of the secondary battery. When H1>50μm, the first polymer layer is prone to loss of more energy density of the secondary battery. By setting H2≤50μm, the energy density of the secondary battery can be improved.

[0013] In some preferred embodiments, the thickness of the adhesive is H2, characterized in that 20μm≤H2≤48μm. When H2 is less than 20μm, the strength of the adhesive is low, and the adhesive is prone to breakage and failure during the drop of the secondary battery. By setting H2≥20μm, the strength of the adhesive can be improved, and the problem of adhesive breakage and failure can be improved. When H2>48μm, the adhesive is prone to loss of more energy density of the secondary battery. By setting H2≤48μm, the energy density of the secondary battery can be improved.

[0014] In some preferred embodiments, the thickness of the first adhesive layer is H3, 3μm≤H3≤12μm. When H3 is less than 3μm, in the opening area, the first adhesive layer has a poor insulation effect on the electrode assembly and the metal layer, and the electrode assembly and the metal layer are prone to short circuit, so the side voltage of the secondary battery will increase and the metal layer will be easily corroded. By setting H3≥3μm, the insulation effect of the first adhesive layer on the electrode assembly and the metal layer can be improved, thereby reducing the side voltage of the secondary battery. When H3>12μm, continuing to increase H3, the insulation effect of the first adhesive layer on the electrode assembly and the metal layer is not significantly improved, and the energy density of the secondary battery is easily lost. By setting H3≤12μm, the energy density of the secondary battery can be improved.

[0015] In some preferred embodiments, 10 μm ≤ H3 ≤ 12 μm. By setting H3 ≥ 10 μm, the insulation effect of the first adhesive layer on the electrode assembly and the metal layer can be further improved. By setting H3 ≤ 12 μm, the energy density of the secondary battery can be increased.

[0016] In some preferred embodiments, the diaphragm includes a first diaphragm, and along the thickness direction of the electrode assembly, the surface of the outermost electrode sheet of the electrode assembly facing the shell is provided with the first diaphragm, and the thickness of the first diaphragm is H4, 7μm≤H4≤13μm. When H4 is less than 7μm, in the opening area, the first diaphragm has a poor insulation effect on the electrode assembly and the metal layer, and the electrode assembly is likely to pass through the diaphragm and short-circuit with the metal layer, so the edge voltage of the secondary battery will increase. By setting H4 ≥ 7μm, the insulation effect of the first diaphragm on the electrode assembly and the metal layer can be improved, thereby reducing the edge voltage of the secondary battery. When H4 is greater than 13μm, if H4 is further increased, the insulation effect of the first diaphragm on the electrode assembly and the metal layer is not significantly improved, and the energy density of the secondary battery is easily lost. By setting H4 ≤ 13μm, the energy density of the secondary battery can be improved.

[0017] In some preferred embodiments, the first polymer layer comprises polypropylene to facilitate packaging of the housing.

[0018] In some preferred embodiments, the first adhesive layer includes at least one of modified polypropylene and polyolefin, which can improve the bonding effect of the first adhesive layer.

[0019] In some preferred embodiments, the metal layer includes at least one of aluminum, iron, and stainless steel to enhance the plasticity of the housing.

[0020] In some preferred embodiments, the housing further comprises a second adhesive layer and a second polymer layer, which are sequentially laminated on a surface of the metal layer facing away from the electrode assembly, with the second adhesive layer disposed between the second polymer layer and the metal layer. The second adhesive layer comprises polyurethane to enhance the bonding effect of the second adhesive layer. The second polymer layer comprises polyamide to enhance the strength of the housing.

[0021] In some preferred embodiments, the second polymer layer of the first wall is provided with a plurality of holes, and along the thickness direction of the electrode assembly, the projections of the plurality of holes fall within the projection of the opening. The heat in the shell can be transferred to the outside of the shell through the openings and holes in turn, thereby improving the heat dissipation effect of the shell.

[0022] In some preferred embodiments, along the thickness direction of the electrode assembly, the projected area of ​​the opening is S1, the sum of the projected areas of all the holes is S2, and the ratio of S2 to S1 is 40% to 80%. When the ratio of S2 to S1 is less than 40%, the heat dissipation effect of the secondary battery is poor, and the maximum temperature of the secondary battery during charging and discharging is high. By setting the ratio of S2 to S1 to ≥40%, the heat dissipation effect of the secondary battery can be improved. Therefore, the maximum temperature of the secondary battery during charging and discharging can be reduced. When the ratio of S2 to S1 is greater than 80%, in several hole areas, the second polymer layer has a poor protection effect on the metal layer, and the metal layer is easily exposed to the outside world and corroded, thereby affecting safety. By setting the ratio of S2 to S1 to ≤80%, the protection effect of the second polymer layer on the metal layer can be improved, and the possibility of the metal layer being exposed to the outside world and corroded, thereby affecting safety, can be reduced.

[0023] In some preferred embodiments, the first polymer layer of the second wall is provided with openings along the thickness direction of the electrode assembly, which can further reduce the thickness of the secondary battery and further improve the energy density of the secondary battery.

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

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

[0026] One or more embodiments are exemplarily described by corresponding drawings, which do not constitute limitations on the embodiments. Elements with the same reference numerals in the drawings are represented as similar elements, and unless otherwise stated, the dimensions in the drawings do not constitute proportional limitations.

[0027] Figure 1 This is a schematic structural diagram of a secondary battery in some embodiments of the present application;

[0028] Figure 2 This is a schematic structural diagram of a secondary battery in some embodiments of the present application;

[0029] Figure 3 Schematic diagram of the structure of the first wall, adhesive member and electrode assembly in some embodiments of the present application;

[0030] Figure 4 Schematic diagram of the structure of the first wall, adhesive member and electrode assembly in some embodiments of the present application;

[0031] Figure 5 Schematic diagram of the structure of the first wall, adhesive member and electrode assembly in some embodiments of the present application;

[0032] Figure 6 Schematic diagram of the structure of the second wall, adhesive and electrode assembly in some embodiments of the present application.

[0033] Description of reference numerals:

[0034] 100. Secondary battery; 10. Shell; 11. First polymer layer; 111. Opening; 12. First adhesive layer; 13. Metal layer; 14. Second adhesive layer; 15. Second polymer layer; 151. Hole; 16. First wall; 17. Second wall; 20. Electrode assembly; 21. Positive electrode sheet; 22. Negative electrode sheet; 23. Diaphragm; 231. First diaphragm; 30. Adhesive; X, first direction; Y, thickness direction of electrode assembly. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly described below in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments.

[0036] References to "embodiments" in this application mean that a particular feature, structure, or characteristic described in connection with the embodiment may be included in at least one embodiment of the application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments.

[0037] In the description of the embodiments of this application, the technical terms "first" and "second" are used only to distinguish different objects and should not be understood to indicate or imply relative importance or implicitly specify the quantity, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, the meaning of "plurality" is more than two, unless otherwise clearly and specifically defined.

[0038] In the description of the embodiments of this application, the term "and / or" is simply a description of the association relationship between associated objects, indicating that three relationships can exist. For example, A and / or B can represent the following three situations: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " in this document generally indicates that the associated objects are in an "or" relationship.

[0039] The term "perpendicular" is used to describe the ideal state between two components. In actual production or use, there may be a state that is approximately perpendicular between the two components. For example, combined with numerical descriptions, perpendicular can refer to the angle between two straight lines being between 90±10°, perpendicular can also refer to the dihedral angle between two planes being between 90±10°, and perpendicular can also refer to the angle between a straight line and a plane being between 90±10°. The two components described as "perpendicular" may not be absolutely straight lines or planes, but may be roughly straight lines or planes. From a macroscopic perspective, a component can be considered a "straight line" or a "plane" if the overall extension direction is a straight line or a plane.

[0040] The technical features involved in the different embodiments of the present application described below can be combined with each other as long as they do not conflict with each other.

[0041] In the first aspect, the embodiment of the present application proposes a secondary battery 100, please refer to Figure 1 and Figure 2 The secondary battery 100 includes a housing 10 and an electrode assembly 20 . The housing 10 can accommodate the electrode assembly 20 and an electrolyte (not shown). The electrolyte infiltrates the electrode assembly 20 in the housing 10 .

[0042] For the electrode assembly 20, please refer to Figure 3 , Figure 3 The lamination structure of the electrode assembly 20 is shown. The electrode assembly 20 includes a negative electrode sheet 22, a positive electrode sheet 21, and a separator 23. In the thickness direction Y of the electrode assembly 20, the positive electrode sheets 21 and the negative electrode sheets 22 are alternately stacked. A separator 23 is provided between adjacent positive electrode sheets 21 and negative electrode sheets 22. The separator 23 is used to insulate and separate the positive electrode sheets 21 and the negative electrode sheets 22. In the embodiments of the present application, the electrode assembly 20 is described as a lamination structure. In other embodiments, the electrode assembly 20 may also be a wound structure or other structures. For example, the positive electrode sheet 21, the separator 23, and the negative electrode sheet 22 are stacked in sequence and then wound to form a wound electrode assembly 20.

[0043] In some embodiments, the housing 10 includes a first wall 16 and a second wall 17 disposed opposite each other along the thickness direction Y of the electrode assembly 20. An adhesive 30 is adhered to the surface of the electrode assembly 20 facing the first wall 16 along the thickness direction Y of the electrode assembly 20, thereby constraining the electrode assembly 20 to the housing 10. This reduces the possibility of the electrode assembly 20 moving within the housing 10 during a drop of the secondary battery 100, thereby improving the safety of the secondary battery 100. Due to space limitations in electronic devices, the volume of the secondary battery 100 is limited, resulting in a capacity bottleneck. However, end users have a continuous demand for increased power levels in the secondary battery 100, which in turn means a continuous increase in the energy density of the secondary battery 100.

[0044] To improve the above problems, in the embodiments of this application, please refer to Figure 2 and 3 The housing 10 includes a first polymer layer 11, a first adhesive layer 12, and a metal layer 13 stacked in sequence. The first polymer layer 11 is located between the first adhesive layer 12 and the electrode assembly 20. The first polymer layer 11 of the first wall 16 is provided with an opening 111. Along the thickness direction Y of the electrode assembly 20, the projection of the electrode assembly 20 overlaps the projection of the opening 111, and the projection of the opening 111 overlaps the projection of the adhesive 30. A portion of the adhesive 30 is located within the opening 111, which can reduce the possibility of the adhesive 30 occupying additional space in the thickness direction Y of the electrode assembly 20. This can reduce the thickness of the secondary battery 100. When the thickness of the secondary battery 100 remains constant, the thickness of the electrode assembly 20 can be increased, thereby improving the energy density of the secondary battery 100.

[0045] In some embodiments, along the thickness direction Y of the electrode assembly 20 , the projection of the negative electrode tab 22 covers the projection of the opening 111 , which can reduce the risk of short circuit between the electrode assembly 20 and the metal layer 13 .

[0046] In some embodiments, along the thickness direction Y of the electrode assembly 20 , the projection of the positive electrode tab 21 covers the projection of the opening 111 , which can reduce the risk of short circuit between the electrode assembly 20 and the metal layer 13 .

[0047] In some embodiments, along the thickness direction Y of the electrode assembly 20, the two opposite surfaces of the adhesive 30 are respectively bonded to the electrode assembly 20 and the first adhesive layer 12. Since the first adhesive layer 12 has adhesive properties, the adhesive 30 has a good bonding effect with the first adhesive layer 12, which can enhance the restraining effect of the adhesive 30 on the electrode assembly 20 and reduce the possibility of the electrode assembly 20 moving in the shell 10. Compared with the two opposite surfaces of the adhesive 30 being respectively bonded to the electrode assembly 20 and the first polymer layer 11, the two opposite surfaces of the adhesive 30 are respectively bonded to the electrode assembly 20 and the first adhesive layer 12, which has a better restraining effect on the electrode assembly 20.

[0048] In some embodiments, along the first direction X, the distance between the electrode assembly 20 and the housing 10 is T1, and the distance between the adhesive 30 and the wall of the opening 111 is T2, where T2 ≤ T1. When the electrode assembly 20 moves within the housing 10, the wall of the opening 111 can block the adhesive 30, thereby reducing the possibility of movement of the electrode assembly 20. The first direction X is perpendicular to the thickness direction Y of the electrode assembly 20, and the first direction X can be any direction perpendicular to the thickness direction of the electrode assembly 20.

[0049] In some embodiments, the thickness of the first polymer layer 11 is H1, and the thickness of the adhesive 30 is H2, where H1 ≤ H2. When H1 ≤ H2, the opening 111 can be completely filled with the adhesive 30 in the thickness direction Y of the electrode assembly 20. That is, the space of the opening 111 in the thickness direction Y of the electrode assembly 20 can be fully utilized, and the thickness of the secondary battery 100 can be reduced, thereby increasing the volume energy density improvement rate of the secondary battery 100. In addition, the surface of the adhesive 30 facing away from the electrode assembly 20 can be bonded to the first adhesive layer 12, which can enhance the binding effect of the adhesive 30 on the electrode assembly 20. When H1 is continued to be increased so that H1>H2, the opening 111 in the thickness direction Y of the electrode assembly 20 cannot be fully filled by the adhesive 30, that is, the space of the opening 111 in the thickness direction Y of the electrode assembly 20 cannot be fully utilized. At this time, the increased thickness of H1 will increase the thickness of the secondary battery 100, so the volume energy density improvement rate of the secondary battery 100 will be reduced. In addition, the surface of the adhesive 30 facing away from the electrode assembly 20 is difficult to adhere to the first adhesive layer 12, so the restraining effect of the adhesive 30 on the electrode assembly 20 will be reduced.

[0050] In some embodiments, the thickness of the first polymer layer 11 is H1, characterized in that 10μm≤H1≤50μm. When H1 is less than 10μm, in the non-opening 111 area, the first polymer layer 11 has a poor insulation effect on the electrode assembly 20 and the metal layer 13, and the electrode assembly 20 and the metal layer 13 are easily short-circuited, so the side voltage of the secondary battery 100 will increase and the metal layer 13 will be easily corroded. By setting H1≥10μm, the insulation effect of the first polymer layer 11 on the electrode assembly 20 and the metal layer 13 can be improved, thereby reducing the side voltage of the secondary battery 100. When H1>50μm, the first polymer layer 11 is prone to lose more energy density of the secondary battery 100. By setting H2≤50μm, the energy density of the secondary battery 100 can be improved.

[0051] In some embodiments, H1 may be 5 μm, 10 μm, 25 μm, 50 μm, or 55 μm. H1 may also be a range consisting of any of the aforementioned values ​​or any value in the range consisting of any of the aforementioned values.

[0052] In some embodiments, the thickness of the adhesive 30 is H2, characterized in that 20μm≤H2≤48μm. When H2 is less than 20μm, the strength of the adhesive 30 is low, and the adhesive 30 is prone to breakage and failure during the drop of the secondary battery 100. By setting H2 ≥ 20μm, the strength of the adhesive 30 can be improved, and the problem of breakage and failure of the adhesive 30 can be improved. When H2 is greater than 48μm, the adhesive 30 is prone to loss of energy density of the secondary battery 100. By setting H2 ≤ 48μm, the energy density of the secondary battery 100 can be improved.

[0053] In some embodiments, H2 may be 15 μm, 20 μm, 25 μm, 48 μm, or 50 μm. H2 may also be a range consisting of any of the aforementioned values ​​or any value in the range consisting of any of the aforementioned values.

[0054] In some embodiments, the thickness of the first adhesive layer 12 is H3, 3μm≤H3≤12μm. When H3 is less than 3μm, the first adhesive layer 12 has a poor insulation effect on the electrode assembly 20 and the metal layer 13 in the opening 111 area, and the electrode assembly 20 and the metal layer 13 are easily short-circuited, so the side voltage of the secondary battery 100 increases and the metal layer 13 is easily corroded. By setting H3 ≥ 3μm, the insulation effect of the first adhesive layer 12 on the electrode assembly 20 and the metal layer 13 can be improved, thereby reducing the side voltage of the secondary battery 100. When H3 is greater than 12μm, if H3 is further increased, the insulation effect of the first adhesive layer 12 on the electrode assembly 20 and the metal layer 13 is not significantly improved, and the energy density of the secondary battery 100 is easily lost. By setting H3 ≤ 12μm, the energy density of the secondary battery 100 can be improved.

[0055] In some embodiments, 10 μm ≤ H3 ≤ 12 μm. By setting H3 ≥ 10 μm, the insulation effect of the first adhesive layer 12 on the electrode assembly 20 and the metal layer 13 can be further improved. By setting H3 ≤ 12 μm, the energy density of the secondary battery 100 can be improved.

[0056] In some embodiments, H3 may be 1 μm, 3 μm, 10 μm, 11 μm, 12 μm, or 15 μm. H3 may also be a range consisting of any of the aforementioned values ​​or any value in the range consisting of any of the aforementioned values.

[0057] In some embodiments, please refer to Figure 4The diaphragm 23 includes a first diaphragm 231. The first diaphragm 231 is disposed along the thickness direction Y of the electrode assembly 20, on the surface of the outermost electrode sheet of the electrode assembly 20 facing the housing 10. The thickness of the first diaphragm 231 is H4, with a value of 7μm≤H4≤13μm. When H4 is less than 7μm, the first diaphragm 231 has a poor insulation effect between the electrode assembly 20 and the metal layer 13 in the opening 111 region. The electrode assembly 20 can easily pass through the diaphragm 23 and short-circuit with the metal layer 13, thereby increasing the side voltage of the secondary battery 100. By setting H4 ≥ 7μm, the insulation effect of the first diaphragm 231 between the electrode assembly 20 and the metal layer 13 can be improved, thereby reducing the side voltage of the secondary battery 100. When H4>13μm, if H4 is continued to increase, the insulation effect of the first diaphragm 231 between the electrode assembly 20 and the metal layer 13 is not significantly improved, and the energy density of the secondary battery 100 is easily lost. By setting H4≤13μm, the energy density of the secondary battery 100 can be improved.

[0058] In some embodiments, H4 may be 5 μm, 7 μm, 10 μm, 13 μm, or 15 μm. H4 may also be a range consisting of any of the aforementioned values ​​or any value in the range consisting of any of the aforementioned values.

[0059] In some embodiments, the first polymer layer 11 includes polypropylene to facilitate packaging of the housing 10 .

[0060] In some embodiments, the first adhesive layer 12 includes at least one of modified polypropylene and polyolefin, which can improve the bonding effect of the first adhesive layer 12 .

[0061] In some embodiments, the metal layer 13 includes at least one of aluminum, iron, and stainless steel to enhance the plasticity of the housing 10 .

[0062] In some embodiments, the housing 10 further includes a second adhesive layer 14 and a second polymer layer 15. The second polymer layer 15 and the second adhesive layer 14 are sequentially laminated on the surface of the metal layer 13 facing away from the electrode assembly 20. The second adhesive layer 14 is disposed between the second polymer layer 15 and the metal layer 13. The second adhesive layer 14 includes polyurethane to enhance the bonding effect of the second adhesive layer 14. The second polymer layer 15 includes polyamide to enhance the strength of the housing 10.

[0063] In some embodiments, please refer to Figure 5 The second polymer layer 15 of the first wall 16 is provided with a plurality of holes 151. Along the thickness direction Y of the electrode assembly 20, the projections of the plurality of holes 151 fall within the projection of the opening 111. The heat in the shell 10 can be transferred to the outside of the shell 10 through the opening 111 and the holes 151 in turn, thereby improving the heat dissipation effect of the shell 10.

[0064] In some embodiments, along the thickness direction of the electrode assembly, the projected area of ​​the opening 111 is S1, the sum of the projected areas of all the plurality of holes 151 is S2, and the ratio of S2 to S1 is 40% to 80%. When the ratio of S2 to S1 is less than 40%, the heat dissipation effect of the secondary battery 100 is poor, and the maximum temperature of the secondary battery 100 during the charging and discharging process is high. By setting the ratio of S2 to S1 to ≥ 40%, the heat dissipation effect of the secondary battery 100 can be improved. Therefore, the maximum temperature of the secondary battery 100 during the charging and discharging process can be reduced. When the ratio of S2 to S1 is greater than 80%, the second polymer layer 15 has a poor protection effect on the metal layer 13 in the region of the plurality of holes 151, and the metal layer 13 is easily exposed to the outside and corroded, thereby affecting safety. By setting the ratio of S2 to S1 to ≤ 80%, the protection effect of the second polymer layer 15 on the metal layer 13 can be improved, and the possibility of the metal layer 13 being exposed to the outside and corroded, thereby affecting safety, can be reduced.

[0065] In some embodiments, please refer to Figure 6 Along the thickness direction Y of the electrode assembly 20 , the first polymer layer 11 of the second wall 17 is provided with an opening 111 , which can further reduce the thickness of the secondary battery 100 and further improve the energy density of the secondary battery 100 .

[0066] In some embodiments, an adhesive member 30 is disposed between the second wall 17 and the electrode assembly 20 to further constrain the electrode assembly 20. A portion of the adhesive member 30 between the second wall 17 and the electrode assembly 20 is located within the opening 111 of the first polymer layer 11 of the second wall 17. This reduces the likelihood of the adhesive member 30 between the second wall 17 and the electrode assembly 20 occupying additional space in the thickness direction Y of the electrode assembly 20, thereby further improving the energy density of the secondary battery 100.

[0067] In a second aspect of the present application, an electronic device is further provided, comprising a secondary battery 100 according to any embodiment of the first aspect. The electronic device of the embodiment of the present application is not particularly limited, and it can be any electronic device known in the prior art. For example, the electronic device includes but is not limited to Bluetooth headsets, mobile phones, tablets, laptops, electric toys, power tools, battery cars, electric cars, ships, spacecraft, etc. Among them, electric toys can include fixed or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc., and spacecraft can include airplanes, rockets, space shuttles, and spacecraft, etc.

[0068] Test part:

[0069] 1. Calculation of the volume energy density improvement rate of secondary batteries:

[0070] Assuming the thickness of the secondary battery without openings in the first polymer layer is H, and the thickness of the first polymer layer is H1, if openings are provided only in the first polymer layer of the first wall, the volumetric energy density improvement rate = H1 / H × 100%. If openings are provided in the first polymer layer of both the first wall and the first polymer layer of the second wall, the volumetric energy density improvement rate = 2 × H1 / H × 100%.

[0071] 2. Insulation test between electrode assembly and shell:

[0072] Use a multimeter to test the voltage (edge ​​voltage) between the positive electrode tab of the electrode assembly and the metal layer of the shell. No corrosion occurs when the edge voltage is less than 0.75V. The smaller the edge voltage, the better the insulation effect.

[0073] 3. Heat dissipation test of secondary batteries:

[0074] A temperature sensor is attached to the surface of the secondary battery to monitor the temperature of the secondary battery, and then the secondary battery is charged and discharged. Assuming that the full charge voltage of the secondary battery is 4.5V, the charge and discharge process is as follows:

[0075] 1) The test environment temperature is 23°C;

[0076] 2) Rest 10 minutes;

[0077] 3)0.5C CC to 4.5V, CV to 0.05C;

[0078] 4) Rest 10 minutes;

[0079] 5) 0.5C DC to 3.0V;

[0080] 6) Rest 10 minutes;

[0081] 7) 9C CC to 4.1V;

[0082] 8)7C CC to 4.2V;

[0083] 9)5C CC to 4.3V;

[0084] 10)3C CC to 4.5V,CV to 0.05C;

[0085] 11)Rest 10min.

[0086] The highest temperature of the secondary battery during the entire charge and discharge process is recorded. The lower the highest temperature, the better the heat dissipation effect of the secondary battery.

[0087] Example 1

[0088] <Preparation of positive electrode sheet>:

[0089] Aluminum foil is used as the positive electrode current collector, and a layer of lithium cobalt oxide slurry is evenly coated on the surface of the aluminum foil. The slurry composition is a combination of 97.5wt% lithium cobalt oxide (LiCoO2), 1.0wt% carbon black (Super P) and 1.5wt% polyvinylidene fluoride (PVDF). It is dried at 85°C and then cold pressed, cut and slit to prepare the positive electrode sheet.

[0090] <Preparation of negative electrode sheet>:

[0091] Copper foil is used as the negative electrode current collector, and a layer of graphite slurry is evenly coated on the surface of the copper foil. The slurry composition is a combination of 97.7wt% artificial graphite, 1.3wt% sodium carboxymethyl cellulose (CMC) and 1.0wt% styrene-butadiene rubber (SBR). It is dried at 85°C and then cold pressed, cut and slit to prepare the negative electrode sheet.

[0092] <Electrolyte Preparation>:

[0093] A solution prepared by mixing lithium salt LiPF6 with a non-aqueous organic solvent (ethylene carbonate (EC): diethyl carbonate (DEC): propylene carbonate (PC): propyl propionate (PP): vinylene carbonate (VC) = 20:30:20:28:2, mass ratio) in a mass ratio of 8:92 was used as the electrolyte for the secondary battery.

[0094] <Preparation of Secondary Battery>:

[0095] The positive electrode sheet and the negative electrode sheet are welded to the electrode tabs, and then the positive electrode sheet and the negative electrode sheet are stacked. The positive electrode sheet and the negative electrode sheet are separated by a polyethylene diaphragm to prepare an electrode assembly.

[0096] An aluminum-plastic film is used as the shell, which is wrapped around the outer surface of the electrode assembly. After top and side sealing, coding, vacuum drying, electrolyte injection, and high-temperature standing, formation and capacity measurement are performed to obtain a preliminary secondary battery.

[0097] The housing comprises a first wall and a second wall disposed opposite each other along the thickness of the electrode assembly. An adhesive is provided on the surface of the electrode assembly facing the first wall along the thickness of the electrode assembly. The housing comprises a first polymer layer, a first adhesive layer, a metal layer, a second adhesive layer, and a second polymer layer stacked in sequence, with the first polymer layer positioned between the first adhesive layer and the electrode assembly. The first polymer layer of the first wall has an opening. Along the thickness of the electrode assembly, the projection of the electrode assembly overlaps the projection of the opening, which in turn overlaps the projection of the adhesive. A portion of the adhesive is positioned within the opening. The thickness H2 of the adhesive is 25 μm. The thickness H1 of the first polymer layer (made of polypropylene) is 25 μm. The thickness H3 of the first adhesive layer (made of modified polypropylene and / or polyolefin) is 3 μm. The thickness of the metal layer (made of aluminum) is 40 μm. The thickness of the second adhesive layer (made of polyurethane) is 3 μm. The thickness of the second polymer layer (made of polyamide) is 25 μm. The housing has a thickness of 96 μm. When the first polymer layer had no opening, the thickness of the secondary battery was 5.4 mm, the length of the secondary battery was 83 mm, and the width of the secondary battery was 63 mm.

[0098] The relevant parameters in Comparative Example 1 and Examples 1 to 19 are shown in Table 1 below.

[0099] Among them, the first polymer layer of Comparative Example 1 is not provided with an opening, and Examples 1 to 19 are only provided with an opening in the first polymer layer of the first wall. The thickness H1 of the first polymer layer of Examples 1 to 5 is different. The thickness H2 of the adhesive of Example 1 and Examples 6 to 9 is different. The thickness H3 of the first adhesive layer of Example 1 and Examples 10 to 14 is different. In Examples 15 to 19, along the thickness direction of the electrode assembly, the surface of the outermost electrode of the electrode assembly facing the shell is provided with a first diaphragm, and the thickness H4 of the first diaphragm of Examples 15 to 19 is different.

[0100] Table 1

[0101]

[0102]

[0103] Note: “\” in Table 1 indicates that the parameter is not included.

[0104] According to Table 1 above, combined with Comparative Example 1 and Examples 1 to 19, it can be seen that the shell includes a first wall and a second wall arranged opposite to each other along the thickness direction of the electrode assembly. Along the thickness direction of the electrode assembly, the surface of the electrode assembly facing the first wall is adhered with an adhesive. The adhesive can restrain the electrode assembly, thereby reducing the possibility of the electrode assembly moving within the shell and affecting safety during a drop. The shell includes a first polymer layer, a first adhesive layer, and a metal layer stacked in sequence. The first polymer layer is located between the first adhesive layer and the electrode assembly. By providing an opening in the first polymer layer of the first wall, along the thickness direction of the electrode assembly, the projection of the electrode assembly covers the projection of the opening, and the projection of the opening covers the projection of the adhesive. Part of the adhesive is located within the opening, which can reduce the thickness of the secondary battery and thus increase the volume energy density improvement rate of the secondary battery. Among them, it can be understood that since the thickness H1 of the first polymer layer of Examples 4 and 5 is much greater than the thickness H1 of the first polymer layer of Comparative Example 1, the thickness H2 of the adhesive of Example 9 is much greater than the thickness H2 of the adhesive of Comparative Example 1, therefore, compared with Comparative Example 1, Examples 4, 5 and Example 9 have almost no volume energy density improvement rate, but the first polymer layer of Examples 4 and 5 has a better insulation effect, so the edge voltage of the secondary batteries of Examples 4 and 5 is lower than the edge voltage of the secondary battery of Comparative Example 1.

[0105] In conjunction with Examples 1 to 5, it can be seen that the thickness of the first polymer layer is H1 and the thickness of the adhesive is H2. When H1 ≤ H2, the opening in the thickness direction of the electrode assembly can be completely filled by the adhesive, that is, the space of the opening in the thickness direction of the electrode assembly can be fully utilized, the thickness of the secondary battery can be reduced, and thus the volume energy density improvement rate of the secondary battery can be increased. In addition, the surface of the adhesive facing away from the electrode assembly can be bonded to the first adhesive layer, which can enhance the adhesive's binding effect on the electrode assembly. When H1 is further increased to H1>H2, the opening in the thickness direction of the electrode assembly is not completely filled by the adhesive, that is, the space of the opening in the thickness direction of the electrode assembly is not fully utilized. In this case, the increased thickness of H1 increases the thickness of the secondary battery, thereby reducing the volume energy density improvement rate of the secondary battery. In addition, the surface of the adhesive facing away from the electrode assembly is difficult to bond to the first adhesive layer, thereby reducing the adhesive's binding effect on the electrode assembly. In addition, when H1 is less than 10μm, the first polymer layer has a poor insulation effect on the electrode assembly and the metal layer in the non-opening area, and the electrode assembly and the metal layer are prone to short circuit. Therefore, the edge voltage of the secondary battery will increase and the metal layer will be easily corroded. By setting H1 ≥ 10μm, the insulation effect of the first polymer layer on the electrode assembly and the metal layer can be improved, thereby reducing the edge voltage of the secondary battery. When H1 is greater than 50μm, the first polymer layer is prone to loss of energy density of the secondary battery. By setting H2 ≤ 50μm, the energy density of the secondary battery can be improved.

[0106] In combination with Example 1 and Examples 6 to 9, it can be seen that the thickness of the first polymer layer is H1, and the thickness of the adhesive is H2. When H2 is less than H1, the opening in the thickness direction of the electrode assembly cannot be fully filled with the adhesive, and the surface of the adhesive facing away from the electrode assembly is difficult to adhere to the first adhesive layer. The adhesive has a poor restraining effect on the electrode assembly, and the electrode assembly is prone to move around in the shell during a drop, affecting safety. By setting H2 ≥ H1, the opening in the thickness direction of the electrode assembly can be fully filled with the adhesive, and the surface of the adhesive facing away from the electrode assembly can be adhered to the first adhesive layer, which can enhance the restraining effect on the electrode assembly and reduce the possibility of the electrode assembly moving around in the shell and affecting safety. In addition, when H2 is less than 20 μm, the strength of the adhesive is low, and the adhesive is prone to breakage and failure during a drop of the secondary battery. By setting H2 ≥ 20 μm, the strength of the adhesive can be enhanced, and the problem of adhesive breakage and failure can be improved. When H2>48μm, the adhesive is likely to lose a lot of energy density of the secondary battery. By setting H2≤48μm, the energy density of the secondary battery can be improved.

[0107] In combination with Example 1 and Examples 10 to 14, it can be seen that the thickness of the first adhesive layer is H3. When H3 is less than 3μm, in the opening area, the first adhesive layer has a poor insulation effect on the electrode assembly and the metal layer, and the electrode assembly and the metal layer are prone to short circuit. Therefore, the side voltage of the secondary battery will increase and the metal layer will be easily corroded. By setting H3 ≥ 3μm, the insulation effect of the first adhesive layer on the electrode assembly and the metal layer can be improved, thereby reducing the side voltage of the secondary battery. By setting H3 ≥ 10μm, the insulation effect of the first adhesive layer on the electrode assembly and the metal layer can be further improved. When H3 is greater than 12μm, if H3 is continued to be increased, the insulation effect of the first adhesive layer on the electrode assembly and the metal layer is not significantly improved, and the energy density of the secondary battery is easily lost. By setting H3 ≤ 12μm, the energy density of the secondary battery can be improved.

[0108] In combination with Example 1 and Examples 15 to 19, it can be seen that a first diaphragm is provided on the surface of the outermost electrode sheet of the electrode assembly facing the shell along the thickness direction of the electrode assembly, which can improve the insulation effect between the electrode assembly and the metal layer. The thickness of the first diaphragm is H4. When H4 is less than 7μm, in the opening area, the insulation effect of the first diaphragm on the electrode assembly and the metal layer is poor, and the electrode assembly is likely to short-circuit with the metal layer after passing through the diaphragm, so the side voltage of the secondary battery will increase. By setting H4 ≥ 7μm, the insulation effect of the first diaphragm on the electrode assembly and the metal layer can be improved, thereby reducing the side voltage of the secondary battery. When H4 is greater than 13μm, if H4 is continued to increase, the insulation effect of the first diaphragm on the electrode assembly and the metal layer is not significantly improved, and the energy density of the secondary battery is easily lost. By setting H4 ≤ 13μm, the energy density of the secondary battery can be improved.

[0109] The relevant parameters in Example 1 and Examples 20 to 24 are shown in Table 1 below.

[0110] The second polymer layer of Example 1 has no holes, while the second polymer layer of the first wall of Examples 20 to 24 has several holes. Along the thickness direction of the electrode assembly, the projected area of ​​the openings in the first polymer layer of the first wall is S1, and the sum of the projected areas of all the holes is S2. The ratios of S2 to S1 vary in Examples 20 to 24.

[0111] Table 2

[0112] <![CDATA[Ratio of S2 to S1]]> Maximum temperature during the charge and discharge process of secondary batteries (°C) Example 1 0％ 49 Example 20 40％ 42 Example 21 20％ 46 Example 22 60％ 39 Example 23 80％ 36 Example 24 85％ 35

[0113] According to Table 2, in conjunction with Examples 1 and 20 to 24, the second polymer layer of the first wall is provided with a plurality of holes, and the projections of the plurality of holes along the thickness of the electrode assembly fall within the projections of the openings. This can improve the heat dissipation of the secondary battery, thereby reducing the maximum temperature of the secondary battery during charging and discharging. The projected area of ​​the openings in the first polymer layer of the first wall is S1, and the sum of the projected areas of all holes is S2. When the ratio of S2 to S1 is less than 40%, the heat dissipation of the secondary battery is poor, and the maximum temperature of the secondary battery during charging and discharging is high. By setting the ratio of S2 to S1 to ≥ 40%, the heat dissipation of the secondary battery can be improved. Therefore, the maximum temperature of the secondary battery during charging and discharging can be reduced. When the ratio of S2 to S1 is greater than 80%, the second polymer layer's protection of the metal layer in the region of the plurality of holes is poor, making the metal layer susceptible to corrosion and thus affecting safety. By setting the ratio of S2 to S1 to ≤ 80%, the second polymer layer's protection of the metal layer can be improved, reducing the possibility of corrosion and thus affecting safety.

[0114] The above description is merely an embodiment of the present application and does not limit the patent scope of the present application. Any equivalent structure or equivalent process transformation made using the contents of the present application specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A secondary battery comprising an electrode assembly and a housing, wherein the electrode assembly is housed in the housing, and the electrode assembly comprises a positive electrode sheet, a separator, and a negative electrode sheet; It is characterized by: The housing includes a first wall and a second wall disposed opposite to each other along a thickness direction of the electrode assembly, with an adhesive being adhered to a surface of the electrode assembly facing the first wall along the thickness direction of the electrode assembly; the housing includes a first polymer layer, a first adhesive layer, and a metal layer stacked in sequence, with the first polymer layer located between the first adhesive layer and the electrode assembly; the first polymer layer of the first wall is provided with an opening, and along the thickness direction of the electrode assembly, a projection of the electrode assembly overlaps a projection of the opening, and a projection of the opening overlaps a projection of the adhesive; A portion of the adhesive member is located in the opening.

2. The secondary battery according to claim 1, wherein Along the thickness direction of the electrode assembly, the projection of the negative electrode sheet covers the projection of the opening.

3. The secondary battery according to claim 2, wherein Along the thickness direction of the electrode assembly, the projection of the positive electrode sheet covers the projection of the opening.

4. The secondary battery according to claim 1, wherein Along the thickness direction of the electrode assembly, two opposite surfaces of the adhesive member are respectively adhered to the electrode assembly and the first adhesive layer.

5. The secondary battery according to claim 1, wherein Along a first direction, the distance between the electrode assembly and the shell is T1, and the distance between the adhesive and the wall of the opening is T2, T2≤T1; wherein the first direction is perpendicular to the thickness direction of the electrode assembly.

6. The secondary battery according to claim 1, wherein The thickness of the first polymer layer is H1, the thickness of the adhesive is H2, and H1≤H2.

7. The secondary battery according to claim 1, wherein the thickness of the first polymer layer is H1, 10μm≤H1≤50μm.

8. The secondary battery according to claim 1, wherein the thickness of the adhesive member is H2, 20μm≤H2≤48μm.

9. The secondary battery according to claim 1, wherein The thickness of the first adhesive layer is H3, 3 μm≤H3≤12 μm.

10. The secondary battery according to claim 9, wherein 10μm≤H3≤12μm.

11. The secondary battery according to claim 1, wherein The diaphragm includes a first diaphragm. Along the thickness direction of the electrode assembly, the surface of the outermost electrode of the electrode assembly facing the shell is provided with the first diaphragm. The thickness of the first diaphragm is H4, 7μm≤H4≤13μm.

12. The secondary battery according to claim 1, wherein The first polymer layer includes polypropylene; and / or the first adhesive layer includes at least one of modified polypropylene and polyolefin; and / or the metal layer includes at least one of aluminum, iron and stainless steel.

13. The secondary battery according to claim 1, wherein The shell also includes a second adhesive layer and a second polymer layer, which are sequentially stacked on the surface of the metal layer facing away from the electrode assembly, and the second adhesive layer is arranged between the second polymer layer and the metal layer. The second adhesive layer includes polyurethane, and the second polymer layer includes polyamide.

14. The secondary battery according to claim 13, wherein: The second polymer layer of the first wall is provided with a plurality of holes, and along the thickness direction of the electrode assembly, the projections of the plurality of holes fall within the projection of the opening.

15. The secondary battery according to claim 14, characterized in that Along the thickness direction of the electrode assembly, the projected area of ​​the opening is S1, the sum of the projected areas of all the holes is S2, and the ratio of S2 to S1 is 40% to 80%.

16. The secondary battery according to any one of claims 1 to 15, characterized in that The first polymer layer of the second wall is provided with the opening along the thickness direction of the electrode assembly.

17. An electronic device, characterized in that: The secondary battery according to any one of claims 1 to 16 is included.

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