Secondary battery and electric device

Abstract

The invention discloses a secondary battery and electric equipment, the secondary battery comprises a shell and an electrode assembly, and the electrode assembly is accommodated in the shell. The shell is a metal shell, the orthographic projection of the shell along a first direction is provided with a notch, and the first direction is the thickness direction of the secondary battery. The shell comprises a first wall located on one side of the secondary battery in the thickness direction, the first wall comprises a first part, and the orthographic projection of the first part in the first direction is defined by a first arc section, a second arc section, a first linear section and a second linear section. A groove is formed in the side, away from the electrode assembly, of the first wall and at least comprises a first groove section and a second groove section which are connected, and at least part of the first groove section is arranged on the first part. The orthographic projection of the first groove section in the first direction is an arc section. When observed in the first direction, the connecting line of the circle center and the base point of the first groove section does not intersect with the first groove section, and the second groove section extends in the direction away from the notch. And the pressure relief rate can be improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of energy storage, in particular to a secondary battery and an electric device. BACKGROUND

[0002] In the prior art, the steel shell battery cell is often provided with a pressure relief groove, so as to ensure that the battery cell can be timely burst open to release pressure when the pressure in the shell exceeds the safe pressure. The steel shell battery cell can include a square steel shell battery cell and a special-shaped steel shell battery cell according to the shape, wherein part of the special-shaped steel shell battery cell is formed by opening a notch in the square steel shell battery cell, for example, a notch is opened at the corner position. At present, the pressure relief groove of this part of the special-shaped steel shell battery cell is slow in the pressure relief rate after burst opening, which causes the battery cell to be prone to fire. SUMMARY

[0003] For the secondary battery in the prior art, the inventors find that the pressure relief groove of this part of the special-shaped steel shell battery cell is not arranged in the stress concentration area of the shell when the pressure in the shell exceeds the safe pressure, and the arrangement of the pressure relief groove towards the notch is not conducive to expanding the burst opening crack after burst opening, so that the pressure relief opening formed by the burst opening crack is small, which causes the pressure relief rate of the burst opening of the pressure relief groove to be slow.

[0004] In view of the above situation, it is necessary to provide a secondary battery which is conducive to improving the pressure relief rate.

[0005] The first aspect of the present application provides a secondary battery, comprising a shell and an electrode assembly, the electrode assembly being accommodated in the shell. The shell is a metal shell, and a projection of the shell along a first direction has a notch, the first direction being a thickness direction of the secondary battery. The projection of the shell along the first direction comprises at least a first side, a second side, a third side and a fourth side connected in sequence, and a boundary of the notch comprises the second side and the third side. A first included angle between the second side and the third side is α, a second included angle between the second side and the third side is β, the first included angle and the second included angle are complementary angles, 0°<α<180°, and 180°<β<360°. The shell comprises a first wall located on one side of the thickness direction of the secondary battery, and the first wall comprises a first part, and a projection of the first part along the first direction is enclosed by a first circular arc segment, a second circular arc segment, a first straight line segment and a second straight line segment. A point of intersection of an extension line of the second side and an extension line of the third side is defined as a base point, and an angle bisector of an included angle between the extension line of the second side and the extension line of the third side is defined as a reference line, the reference line comprises a first segment extending from the base point within the first included angle, a distance between the base point and the first side along an extension direction of the second side is L1, a distance between the base point and the fourth side along an extension direction of the third side is L2, and L2≥L1. A center of the first circular arc segment is located on the first segment, a radius of the first circular arc segment is L2, and a distance between the center of the first circular arc segment and the base point is L2. A center of the second circular arc segment is located on the first segment, a radius of the second circular arc segment is L2, and a distance between the center of the second circular arc segment and the base point is L2-L1. The first straight line segment connects end points of the first circular arc segment and the second circular arc segment on one side of the reference line, and the second straight line segment connects end points of the first circular arc segment and the second circular arc segment on the other side of the reference line. An extension line of the first straight line segment passes through a midpoint of the second side and is parallel to the reference line, and an extension line of the second straight line segment passes through a midpoint of the third side and is parallel to the reference line. A side of the first wall away from the electrode assembly is provided with a groove, and the groove comprises at least a first groove segment and a second groove segment connected in sequence, and at least part of the first groove segment is located in the first part. Along the first direction, a projection of the first groove segment is a circular arc segment, the second groove segment comprises a first end and a second end, the first end is connected to the first groove segment, and the second end is an end of the groove. As viewed along the first direction, a line connecting a center of the first groove segment and the base point does not intersect the first groove segment, and the second groove segment extends from the first end in a direction away from the notch.

[0006] For the secondary battery with the projection of the shell along the first direction having the notch, when the gas pressure in the shell exceeds the safe gas pressure, the stress is mainly concentrated in the first part of the first wall. By locating at least part of the first groove segment in the first part, the groove can be arranged in the stress concentration area of the shell when the gas pressure in the shell exceeds the safe gas pressure. Moreover, the line connecting the center of the first groove segment and the base point does not intersect the first groove segment, and the second groove segment extends from the first end in a direction away from the notch, which is conducive to expanding the burst crack, so as to make the pressure relief port formed by the burst crack larger. Thus, the pressure relief rate is improved.

[0007] In one or more of the above embodiments, the second groove segment has a straight-line projection in the first direction. In this case, the rate of propagation of the propagation crack can be improved after the groove is broken, which is conducive to further improving the pressure relief rate.

[0008] In one or more of the above embodiments, the length of the second groove segment is S1, the length of the projection of the second groove segment on the reference line is S2, and 1≤S1 / S2≤1.5. When the gas pressure in the shell exceeds the safe pressure, the first wall is bulged by the pressure and deformed in the thickness direction. The reference line basically passes through the area with the largest thickness difference at a relatively short distance. By setting 1≤S1 / S2≤1.5, the second groove segment deviates from the reference line and is kept within a suitable range, which can facilitate the rapid formation of the propagation crack of the second groove segment and is conducive to further improving the pressure relief rate.

[0009] In one or more of the above embodiments, 1≤S1 / S2≤1.2. By setting 1≤S1 / S2≤1.2, the second groove segment deviates from the reference line and is kept within a smaller range, which can facilitate the more rapid formation of the propagation crack of the second groove segment and is conducive to further improving the pressure relief rate.

[0010] In one or more of the above embodiments, 0.5mm≤S2≤0.5L1. By setting 0.5mm≤S2, the second groove segment is not too short, which can facilitate the formation of a larger pressure relief opening by the propagation crack and is conducive to further improving the pressure relief rate. By setting S2≤0.5L1, the second groove segment is not too long while ensuring a certain pressure relief rate, which is conducive to improving the processing efficiency of the groove and improving the structural strength of the first wall.

[0011] In one or more of the above embodiments, the distance between the midpoint of the first groove segment and the base point is D, and 0mm≤D≤5mm. When the gas pressure in the shell exceeds the safe pressure, the stress is more concentrated at a position closer to the base point in the first part of the first wall. By setting 0mm≤D≤5mm, the first groove segment is closer to the base point, which can make the propagation crack form a larger pressure relief opening after the first groove segment is broken, and is conducive to further improving the pressure relief rate.

[0012] In one or more of the above embodiments, the entire first groove segment is arranged in the first part. This is conducive to further improving the pressure relief rate.

[0013] In one or more of the above embodiments, the first end is connected to the end point of the first groove segment. In this case, when the gas pressure in the shell exceeds the safe pressure, the propagation crack can be easily extended from the first groove segment to the second groove segment, which is conducive to further improving the pressure relief rate.

[0014] In one or more of the above embodiments, the two endpoints of the first groove section are respectively located on different sides of a straight line where the line connects the center of the first groove section and the base point. In this case, when the gas pressure inside the shell exceeds the safe gas pressure, the first groove section can be easily broken at both ends to form burst cracks, which is conducive to further improving the pressure relief rate.

[0015] In one or more of the above embodiments, the number of the second groove sections is two. By providing two second groove sections, the burst cracks of the second groove sections can form a larger pressure relief port, which is conducive to further improving the pressure relief rate.

[0016] The second aspect of the present application provides a power consuming device including the secondary battery of the first aspect of the present application. The secondary battery of the first aspect of the present application can improve the pressure relief rate of the groove burst, which is conducive to improving the safety of the power consuming device. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 A front view of the secondary battery provided by an embodiment of the present application.

[0018] Figure 2 A top view of the secondary battery provided by an embodiment of the present application.

[0019] Figure 3 A partial enlarged view of the notch position in Figure 2

[0020] Figure 4 A schematic diagram for determining the first part provided by an embodiment of the present application.

[0021] Figure 5 A schematic diagram of the groove provided by another embodiment of the present application.

[0022] Figure 6 A schematic diagram of the groove provided by yet another embodiment of the present application.

[0023] Figure 7 A schematic diagram of the power consuming device provided by an embodiment of the present application.

[0024] MAIN ELEMENT SYMBOL EXPLANATION ​100, secondary battery; 10, shell; 101, first side; 102, second side; 103, third side; 104, fourth side; 105, reference line; 1051, first segment; 11, shell cover; 12, shell body; 121, bottom wall; 122, side wall; 13, notch; 14, first wall; 141, first part; 1411, first circular arc segment; 1412, second circular arc segment; 1413, first straight line segment; 1414, second straight line segment; 142, groove; 1421, first slot segment; 1422, second slot segment; 1422a, first end; 1422b, second end; 15, pole; 1000, electrical equipment; X, first direction. DETAILED DESCRIPTION

[0025] The technical solutions in the embodiments of the present application will be described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, not all the embodiments.

[0026] 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 a middle element can be present at the same time. When an element is considered to be "provided on" another element, it can be directly provided on the other element or a middle element can be present at the same time.

[0027] Unless otherwise specified, the term "plurality" used herein refers to two or more.

[0028] The terms "first", "second", and the like are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implying the number, specific order or primary and secondary relationship of the indicated technical features.

[0029] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present application belongs. The terms used in the specification of the present application are only for the purpose of describing specific embodiments and are not intended to limit the present application. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0030] It should be understood that "orthogonal projection" used in the present application is the orthogonal projection of a component or two components in a certain direction.

[0031] An embodiment of the present application provides a secondary battery, comprising a housing and an electrode assembly, wherein the electrode assembly is housed within the housing. The housing is a metal shell, and the orthographic projection of the housing along a first direction has a notch, wherein the first direction is the thickness direction of the secondary battery. The orthographic projection of the housing along the first direction comprises at least a first side, a second side, a third side, and a fourth side connected in sequence, and the boundary of the notch comprises the second side and the third side, wherein the first angle between the second side and the third side is α, and the second angle between the second side and the third side is β, wherein the first angle and the second angle are mutually angled, and 0°<α<180°, and 180°<β<360°. The housing comprises a first wall located on one side in the thickness direction of the secondary battery, wherein the first wall comprises a first portion, wherein the orthographic projection of the first portion along the first direction is formed by enclosing a first arc segment, a second arc segment, a first straight line segment, and a second straight line segment. Define the intersection of the extended lines of the second and third sides as the base point, and define the angle bisector of the angle between the extended lines of the second and third sides as the reference line. The reference line includes a first segment extending from the base point within the first angle. The distance between the base point and the first side along the extension direction of the second side is L1, and the distance between the base point and the fourth side along the extension direction of the third side is L2, where L2 ≥ L1. The center of the first arc segment is located on the first segment, the radius of the first arc segment is L2, and the distance between the center of the first arc segment and the base point is L2. The center of the second arc segment is located on the first segment, the radius of the second arc segment is L2, and the distance between the center of the second arc segment and the base point is L2-L1. The first straight line segment connects the endpoints of the first arc segment and the second arc segment on one side of the reference line, the second straight line segment connects the endpoints of the first arc segment and the second arc segment on the other side of the reference line, the extension line of the first straight line segment passes through the midpoint of the second side and is parallel to the reference line, and the extension line of the second straight line segment passes through the midpoint of the third side and is parallel to the reference line. A groove is provided on the side of the first wall facing away from the electrode assembly, and the groove includes at least a first groove section and a second groove section connected to each other, and at least part of the first groove section is provided in the first part. Along the first direction, the orthographic projection of the first groove section is an arc section, and the second groove section includes a first end and a second end, the first end connecting the first groove section, and the second end is the end of the groove. Observed along the first direction, the line connecting the center of the first groove section and the base point does not intersect with the first groove section, and the second groove section extends from the first end in a direction away from the notch.

[0032] The present application relates to a secondary battery having a notch in the orthographic projection of the shell along the first direction. When the pressure inside the shell exceeds the safety pressure and the shell expands and deforms, the stress is mainly concentrated in the first portion of the first wall. By providing at least part of the first groove section in the first portion, the groove can be provided in the stress concentration area of ​​the shell when the pressure inside the shell exceeds the safety pressure. In addition, the line connecting the center of the circle and the base point of the first groove section does not intersect with the first groove section, and the second groove section extends from the first end in a direction away from the notch. The second groove section is conducive to expanding the explosive crack, thereby making the pressure relief port formed by the explosive crack larger. This is conducive to increasing the pressure relief rate.

[0033] Some embodiments of the present application will be described below with reference to the accompanying drawings. The following embodiments and features of the embodiments can be combined with each other without conflict.

[0034] Referring to Figure 1 Embodiments of the present application provide a secondary battery 100, which includes a housing 10 and an electrode assembly (not shown in the figure), and the electrode assembly is accommodated in the housing 10. The housing 10 is provided with a receiving cavity for accommodating the electrode assembly in the housing 10. The receiving cavity is filled with an electrolyte, and the electrolyte includes an electrolyte salt. The electrolyte salt includes at least one of an organic lithium salt or an inorganic lithium salt. In some embodiments, the electrolyte salt includes, but is not limited to, at least one of lithium hexafluorophosphate (LiPF6), lithium bis-trifluoromethanesulfonimide LiN(CF3SO2)2 (LiTFSI), lithium bis(fluorosulfonyl)imide Li(N(SO2F)2) (LiFSI), lithium hexafluorocerate (LiCsF6), lithium perchlorate (LiClO4), or lithium trifluoromethanesulfonate (LiCF3SO3).

[0035] The housing 10 is a metal shell, which includes, but is not limited to, a steel shell, a copper shell, and a nickel shell. Referring to Figure 1 In some embodiments, the housing 10 includes a shell cover 11 and a shell body 12, and the shell cover 11 and the shell body 12 are fixedly connected along a first direction X, which is the thickness direction of the secondary battery 100. In this case, the metal materials of the shell cover 11 and the shell body 12 can be the same or different, and the fixed connection mode of the shell cover 11 and the shell body 12 includes, but is not limited to, welding, bonding, and riveting, which are not limited by the present application.

[0036] The shell cover 11 and the shell body 12 jointly constitute the receiving cavity. In some embodiments, the shell cover 11 and the shell body 12 are both in a pit structure. The pit structure includes a bottom wall 121 and a side wall 122, and the side wall 122 is connected to the periphery of the bottom wall 121, and the side wall 122 and the bottom wall 121 jointly form a pit. Referring to Figure 1 In some embodiments, the shell cover 11 is in a plate structure, the shell body 12 is in a pit structure, and the shell cover 11 covers the pit along the first direction X.

[0037] Referring to Figure 2The projection of the shell 10 along the first direction X has a notch 13, the projection of the shell 10 along the first direction X at least includes a first side 101, a second side 102, a third side 103 and a fourth side 104 connected in sequence, the boundary of the notch 13 includes the second side 102 and the third side 103, the first included angle of the second side 102 and the third side 103 is α, the second included angle of the second side 102 and the third side 103 is β, the first included angle and the second included angle are complementary angles, 0° < α < 180°, 180° < β < 360°. For example, α is 5°, 10°, 20°, 50°, 70°, 90°, 120°, 150°, 175° or any value between the listed endpoint values, and β is 355°, 350°, 340°, 310°, 290°, 270°, 240°, 210°, 185° or any value between the listed endpoint values. Along the extension direction of the second side 102, the first side 101 and the third side 103 are respectively located on different sides of the extension line of the second side 102, and along the extension direction of the third side 103, the second side 102 and the fourth side 104 are respectively located on different sides of the extension line of the third side 103. It should be understood that when the second side 102 and the third side 103 are directly connected, the first included angle is the included angle of the second side 102 and the third side 103; when the second side 102 and the third side 103 are connected with a round corner transition, the first included angle is the included angle between the extension line of the second side 102 and the extension line of the third side 103.

[0038] In the present application, the number of notches 13 can be multiple, and accordingly, the projection of the shell 10 along the first direction X can include multiple sets of structures in which the first side 101, the second side 102, the third side 103 and the fourth side 104 are connected in sequence.

[0039] The shell 10 includes a first wall 14 located on one side in the thickness direction of the secondary battery 100. The first wall 14 can be a shell cover 11 in a plate structure, or a bottom wall 121 in a concave structure, which is not limited in the present application. The thickness of the first wall 14 can be 75 μm to 200 μm. For example, the thickness of the first wall 14 is 75 μm, 80 μm, 90 μm, 100 μm, 120 μm, 150 μm, 200 μm or any value between the listed endpoint values.

[0040] Please refer to Figure 2 and Figure 3 The first wall 14 includes a first part 141, and the projection of the first part 141 along the first direction X is formed by a first circular arc segment 1411, a second circular arc segment 1412, a first straight line segment 1413 and a second straight line segment 1414. As Figure 3As shown, the intersection of the extension line of the second edge 102 and the extension line of the third edge 103 is defined as the base point O0, and the reference line 105 is defined as the angle bisector of the angle between the extension line of the second edge 102 and the extension line of the third edge 103, the reference line 105 includes a first segment 1051 extending from the base point O0 within the first angle, the distance between the base point O0 and the first edge 101 along the extension direction of the second edge 102 is L1, the distance between the base point O0 and the fourth edge 104 along the extension direction of the third edge 103 is L2, and L2≥L1. The positions of the first arc segment 1411, the second arc segment 1412, the first straight line segment 1413, and the second straight line segment 1414 are determined as follows: The center O1 of the first arc segment 1411 is located on the first segment 1051, the radius of the first arc segment 1411 is L2, and the distance between the center O1 of the first arc segment 1411 and the base point O0 is L2. The center O2 of the second arc segment 1412 is located on the first segment 1051, the radius of the second arc segment 1412 is L2, and the distance between the center O2 of the second arc segment 1412 and the base point O0 is L2-L1. It can be understood that when L2=L1, the center O2 of the second arc segment 1412 is located on the base point O0. The first straight line segment 1413 connects the end points of the first arc segment 1411 and the second arc segment 1412 on one side of the reference line 105, the second straight line segment 1414 connects the end points of the first arc segment 1411 and the second arc segment 1412 on the other side of the reference line 105, the extension line of the first straight line segment 1413 passes through the midpoint of the second edge 102 and is parallel to the reference line 105, and the extension line of the second straight line segment 1414 passes through the midpoint of the third edge 103 and is parallel to the reference line 105.

[0041] Please refer to Figure 4In some embodiments, the first arc segment 1411, the second arc segment 1412, the first straight line segment 1413, and the second straight line segment 1414 can be determined as follows: a first circle is drawn with a point on the reference line 105 within the angle between the second side 102 and the third side 103 and a distance L2 from the base point O0 as the center and L2 as the radius; a second circle is drawn with a point on the reference line 105 within the angle between the second side 102 and the third side 103 and a distance L2-L1 from the base point O0 as the center and L2 as the radius; a first straight line is drawn parallel to the reference line 105 through the midpoint of the second side 102; and a second straight line is drawn parallel to the reference line 105 through the midpoint of the third side 103. The first circle, the second circle, the first straight line, and the second straight line collectively form a closed region in the first wall 14, wherein the first arc segment 1411 is a portion of the first circle that forms the closed region, the second arc segment 1412 is a portion of the second circle that forms the closed region, the first straight line segment 1413 is a portion of the first straight line that forms the closed region, and the second straight line segment 1414 is a portion of the second straight line that forms the closed region. It should be understood that the present application does not limit the manner in which the first arc segment 1411, the second arc segment 1412, the first straight line segment 1413, and the second straight line segment 1414 are determined, nor the order and manner in which the first circle, the second circle, the first straight line, and the second straight line are drawn. The above is merely an example.

[0042] In some embodiments, 5 mm < L1 < 50 mm, and L1 < L2 < 100 mm. For example, L1 can be 5 mm, 10 mm, 15 mm, 20 mm, 25 mm, 30 mm, 40 mm, 50 mm, or any value between the listed endpoint values. As an example, when L1 is 50 mm, 50 mm < L2 < 100 mm, for example, L2 can be 50 mm, 60 mm, 70 mm, 80 mm, 90 mm, 100 mm, or any value between the listed endpoint values.

[0043] See Figure 3 and Figure 4The side of the first wall 14 away from the electrode assembly is provided with a groove 142, wherein the groove depth of the groove 142 can be 30 μm to 120 μm, for example, the groove depth of the groove 142 is 30 μm, 40 μm, 50 μm, 70 μm, 90 μm, 120 μm or any value between the listed endpoint values. The groove width of the groove 142 can be 0.05 mm to 0.2 mm, for example, the groove width of the groove 142 is 0.05 mm, 0.06 mm, 0.08 mm, 0.1 mm, 0.12 mm, 0.15 mm, 0.2 mm or any value between the listed endpoint values. The groove 142 at least includes a first groove segment 1421 and a second groove segment 1422 connected together, and at least part of the first groove segment 1421 is provided in the first portion 141. For the secondary battery 100 with the notch 13 in the orthographic projection of the shell 10 along the first direction X, when the shell internal gas pressure exceeds the safe gas pressure, the stress is mainly concentrated in the first portion 141 of the first wall 14, and by providing at least part of the first groove segment 1421 in the first portion 141, the groove 142 can be arranged in the stress concentration area of the shell 10 when the shell internal gas pressure exceeds the safe gas pressure, facilitating the timely explosion of the groove 142 to release pressure.

[0044] In the first direction X, the orthographic projection of the first groove segment 1421 is a circular arc segment, and it should be understood that, due to the groove width of the groove 142, the orthographic projection of the first groove segment 1421 along the first direction X is a circular arc segment, which means that the side of the first groove segment 1421 in the groove width direction close to the notch 13 along the first direction X is a circular arc segment. Wherein, the central angle of the first groove segment 1421 can be 30° to 120°, for example, the central angle of the first groove segment 1421 is 30°, 40°, 50°, 60°, 70°, 80°, 90°, 100°, 110°, 120° or any value between the listed endpoint values. The radius of the first groove segment 1421 can be 3 mm to 20 mm, for example, the radius of the first groove segment 1421 is 3 mm, 4 mm, 6 mm, 8 mm, 10 mm, 12 mm, 15 mm, 20 mm or any value between the listed endpoint values.

[0045] In the first direction X, the orthographic projection of the second groove segment 1422 can be a straight line segment or a curved line segment. The second groove segment 1422 includes a first end 1422a and a second end 1422b, the first end 1422a is connected to the first groove segment 1421, and the second end 1422b is the end of the groove 142. The line connecting the center of the first groove segment 1421 and the base point O0 does not intersect the first groove segment 1421 when viewed along the first direction X, and the second groove segment 1422 extends from the first end 1422a in a direction away from the notch 13. In this case, the second groove segment 1422 is beneficial to expand the explosion crack, so as to enable the pressure release port formed by the explosion crack to be larger. Thus, it is beneficial to improve the pressure relief rate. As an exemplary, Figure 3As shown in FIG. 14B, the second slot segment 1422 is a straight line segment in the front view of the first direction X. In this case, when the groove 142 is opened, the rate of expanding the opening crack can be improved, which is conducive to further improving the pressure relief rate.

[0046] It should be understood that the center of the first slot segment 1421 can be determined as follows: a straight line segment is connected between the two end points of the arc segment of the first slot segment 1421, a perpendicular line of the straight line segment is drawn through the midpoint of the straight line segment, and a point is determined on the perpendicular line, which satisfies that the distance between the end points of the arc segment of the first slot segment 1421 is equal to the distance between the midpoints of the arc segment of the first slot segment 1421. Then, the point is the center of the first slot segment 1421.

[0047] It should be understood that the second slot segment 1422 extends from the first end 1422a in a direction away from the notch 13 means that a prolongation line of the second edge 102 is drawn in a direction away from the first edge 101, a prolongation line of the third edge 103 is drawn in a direction away from the fourth edge 104, and the second slot segment 1422 extends from the first end 1422a between the prolongation line of the second edge 102 and the prolongation line of the third edge 103.

[0048] In some embodiments, the midpoint O3 of the first slot segment 1421 is located in the first portion 141. It should be understood that the midpoint of the first slot segment 1421 refers to the midpoint of the side of the first slot segment 1421 close to the notch 13 in the slot width direction.

[0049] In some embodiments, the two end points of the first slot segment 1421 are located on different sides of the straight line where the line connecting the center of the first slot segment 1421 and the base point O0 is located. In this case, when the gas pressure in the shell exceeds the safe gas pressure, the opening cracks can be quickly formed at both ends of the first slot segment 1421, which is conducive to further improving the pressure relief rate.

[0050] Please refer to Figure 5 In some embodiments, the distance between the midpoint O3 of the first slot segment 1421 and the base point O0 is D, and 0mm≤D≤5mm. For example, D is 0mm, 1mm, 2mm, 3mm, 4mm, 5mm or any value between the listed endpoint values. When the gas pressure in the shell exceeds the safe gas pressure, the stress is more concentrated at the position of the first portion 141 of the first wall 14 closer to the base point O0. By setting 0mm≤D≤5mm, the first slot segment 1421 is closer to the base point O0, which can make the opening crack formed by the opening of the first slot segment 1421 form a larger pressure relief port, which is conducive to further improving the pressure relief rate.

[0051] In some embodiments, the shortest distance between the midpoint O3 of the first groove segment 1421 and the reference line 105 is 0 mm to 0.5 L1. As an example, when L1 = 50 mm, the shortest distance between the midpoint O3 of the first groove segment 1421 and the reference line 105 is 0 mm to 25 mm, such as 0 mm, 5 mm, 10 mm, 15 mm, 20 mm, 25 mm, or any value between the listed endpoint values. It should be understood that a line segment is drawn through the midpoint O3 of the first groove segment 1421 perpendicular to the reference line 105, and the length of the line segment is the shortest distance referred to herein.

[0052] In some embodiments, the entire first groove segment 1421 is disposed in the first portion 141. For example, when the groove 142 is composed of the first groove segment 1421 and the second groove segment 1422, at least the entire first groove segment 1421 is disposed in the first portion 141, and the second groove segment 1422 can or can not be disposed in the first portion 141. This is advantageous for further increasing the pressure relief rate.

[0053] Referring to Figure 5 In some embodiments, the first end 1422a of the second groove segment 1422 is connected to the endpoint of the first groove segment 1421. In this case, when the gas pressure inside the shell exceeds the safe gas pressure, it is convenient for the burst crack to extend from the first groove segment 1421 to the second groove segment 1422, which is advantageous for further increasing the pressure relief rate.

[0054] Referring to Figure 5 In some embodiments, the projection of the second groove segment 1422 along the first direction X is a straight line segment, the length of the second groove segment 1422 is S1, the projection length of the second groove segment 1422 on the reference line 105 is S2, and 1≤S1 / S2≤1.5. For example, the value of S1 / S2 is 1, 1.1, 1.2, 1.3, 1.4, 1.5, or any value between the listed endpoint values. When the gas pressure inside the shell exceeds the safe gas pressure, the first wall 14 is pressed to bulge and deform in the thickness direction, and the reference line 105 substantially penetrates the region with the largest thickness difference at a relatively short distance. By setting 1≤S1 / S2≤1.5, the second groove segment 1422 deviates from the reference line 105 and is kept within a suitable range, which is convenient for the second groove segment 1422 to quickly form a burst crack, and is advantageous for further increasing the pressure relief rate.

[0055] In some embodiments, 1≤S1 / S2≤1.2. By setting 1≤S1 / S2≤1.2, the second groove segment 1422 deviates from the reference line 105 and is kept within a smaller range, which is convenient for the second groove segment 1422 to more quickly form a burst crack, and is advantageous for further increasing the pressure relief rate.

[0056] In some embodiments, 0.5mm≤S2≤0.5L1. As an example, when L1=50mm, 0.5mm≤S2≤25mm, for example, S2 is 0.5mm, 1mm, 2mm, 5mm, 10mm, 15mm, 20mm, 25mm or any value between the listed endpoint values. By setting 0.5mm≤S2, the second groove segment 1422 is not too short, which can facilitate the burst crack to form a larger pressure relief opening, which is conducive to further improving the pressure relief rate. By setting S2≤0.5L1, while ensuring a certain pressure relief rate, the second groove segment 1422 is not too long, which is conducive to improving the processing efficiency of the groove 142 and improving the structural strength of the first wall 14.

[0057] Please refer to Figure 6 In some embodiments, the number of second groove segments 1422 is two. By setting two second groove segments 1423, the burst crack of the second groove segment 1422 can form a larger pressure relief opening, which is conducive to further improving the pressure relief rate. It should be understood that the structural configuration parameters of the two second groove segments 1422 can be the same or different.

[0058] In some embodiments, the two second groove segments 1422 are respectively located on different sides of the symmetry axis of the circular arc segment of the first groove segment 1421. In some embodiments, the two second groove segments 1422 are symmetrically arranged on the first groove segment 1421. For example, please refer to Figure 6 If the first end 1422a of one second groove segment 1422 is connected to the endpoint of the first groove segment 1421, the first end 1422a of the other second groove segment 1422 is also connected to the endpoint of the first groove segment 1421.

[0059] In some embodiments, the entire groove 142 is arranged in the first part 141. For example, when the groove 142 is composed of the first groove segment 1421 and the two second groove segments 1422, the first groove segment 1421 and the two second groove segments 1422 are arranged in the first part 141.

[0060] In some embodiments, the electrode assembly includes a positive electrode sheet, a negative electrode sheet, and a separator separating the positive electrode sheet and the negative electrode sheet. The positive electrode sheet, the negative electrode sheet, and the separator can be arranged in a stack to form a stack structure or arranged in a roll to form a roll structure, which is not limited by the present application. The positive electrode sheet can be provided with a positive electrode tab, and the negative electrode sheet can be provided with a negative electrode tab, so as to lead out the positive polarity of the electrode assembly through the positive electrode tab and the negative polarity of the electrode assembly through the negative electrode tab. When the shell cover 11 and the shell 12 are conductively arranged, one of the positive electrode tab and the negative electrode tab is connected to any one of the shell cover 11 and the shell 12, and the other of the positive electrode tab and the negative electrode tab is connected to the pole 15 which is insulatively arranged on the shell cover 11 or the shell 12 (see Figure 1 and Figure 2). When the shell cover 11 is insulated from the shell 12, one of the positive and negative tabs is connected to the shell cover 11, and the other of the positive and negative tabs is connected to the shell 12. It should be understood that the positive tab can not be provided with a positive tab and / or the negative tab can not be provided with a negative tab, and the positive tab and / or the negative tab can be led out of the polarity of the electrode assembly by providing an empty foil area.

[0061] Referring to Figure 7 Embodiments of the present application also provide a power consuming device 1000, which comprises the secondary battery 100 according to any one of the foregoing embodiments. The secondary battery 100 of the present application can improve the timeliness of the pressure relief of the groove 142, which is conducive to improving the safety of the power consuming device 1000. The power consuming device 1000 includes but is not limited to electronic book players, mobile phones, fax machines, copiers, printers, headsets, video recorders, liquid crystal televisions, tape recorders, radios, cameras, tablet computers, notebook computers and other electronic devices.

[0062] To verify the influence of the provided scheme of the present application on the secondary battery 100, the inventors of the present application conducted the following experiment.

[0063] The preparation process of the secondary battery 100 in Embodiment 1 includes the following steps: Preparation of the positive tab: The positive active material lithium cobaltate, the conductive agent conductive carbon black, and the binder polyvinylidene fluoride (PVDF) are dissolved in an N-methyl pyrrolidone (NMP) solution in a mass ratio of 97.5:1:1.5 to form a positive slurry. An aluminum foil is used as the positive current collector, and the positive slurry is coated on the positive current collector. After drying, cold pressing, and slitting, the positive tab is obtained.

[0064] Preparation of the negative tab: The negative active material artificial graphite, the thickening agent carboxymethyl cellulose sodium (CMC), and the binder styrene-butadiene rubber (SBR) are mixed in a mass ratio of 96:1.5:2.5, and deionized water is added. The mixture is stirred uniformly in a vacuum stirrer to obtain a negative slurry. The negative slurry is uniformly coated on a negative current collector copper foil. After drying, cold pressing, tabbing, and slitting, the negative tab is obtained.

[0065] Preparation of the separator: The base material layer of the separator is polyethylene (PE). An aluminum oxide ceramic layer is coated on both sides of the base material layer of the separator. Finally, a binder polyvinylidene fluoride (PVDF) is coated on both sides of the coated ceramic layer and dried.

[0066] Preparation of the electrolyte: In a dry argon glove box, ethylene carbonate (EC), methyl ethyl carbonate (EMC), and diethyl carbonate (DEC) are mixed in a mass ratio of 3:5:2. Lithium salt LiPF6 is added, and the mixture is stirred uniformly to obtain an electrolyte, wherein the mass percentage concentration of LiPF6 is 12.5%.

[0067] The etching process of the groove 142: the shell cover 11 with the notch 13 is fixed in a special fixture; the laser etching path is set according to the required notch shape and the notch position; the laser energy is adjusted according to the required notch depth and the thickness of the shell cover 11, and the surface of the shell cover 11 is etched using a high-precision laser device. Prepare the shell cover 11, ensure that the inside of the shell 12 is clean and dust-free, weld the positive electrode lug to the upper end of the shell 12, and weld the negative electrode lug to the pole 15 which is insulated and arranged in the shell 12, to ensure good electrical connection; place the completed electrode assembly into the shell 12 to ensure good fit between the electrode assembly and the shell 12; assemble the shell cover 11 with the shell 12 and seal by laser welding to ensure the air tightness of the secondary battery 100. The length of the secondary battery 100 is 70 mm, the width is 55 mm, the height is 4.5 mm, the second edge 102 and the third edge 103 are connected with a radius of 2.5 mm, and a is 90°, L1 is 14 mm, and L2 is 26 mm; the thickness of the shell cover 11 is 100 μm, the notch depth (i.e. the groove depth of the groove 142) is 66 μm, the groove 142 includes a first groove segment 1421 and a second groove segment 1422, the midpoint O3 of the first groove segment 1421 is located on the reference line 105, and the distance D between the midpoint O3 of the first groove segment 1421 and the base point O0 is 0 mm, the radius of the first groove segment 1421 is 5 mm, the central angle of the first groove segment 1421 is 90°, and the second groove segment 1422 connects the end point of the first groove segment 1421. The second groove segment 1422 is a straight line segment parallel to the reference line 105 and the length S1 is 5 mm.

[0068] The preparation process of the secondary battery 100 in Comparative Example 1 is basically the same as that in Example 1, and the difference is that the groove 142 of the secondary battery 100 in Comparative Example 1 only includes the first groove segment 1421, and the first groove segment 1421 is arranged outside the first part 141, and accordingly there is no data of S1, S2 and D.

[0069] The preparation process of the secondary battery 100 in Comparative Example 2 is basically the same as that in Example 1, and the difference is that the groove 142 of the secondary battery 100 in Comparative Example 2 only includes the first groove segment 1421, and accordingly there is no data of S1 and S2.

[0070] The preparation process of the secondary battery 100 in Comparative Example 3 is basically the same as that in Example 1, and the difference is that the second groove segment 1422 of the secondary battery 100 in Comparative Example 3 is not extended from the first end 1422a in the direction away from the notch 13, and the first end 1422a is arranged outside the first part 141, and accordingly there is no data of S1 and S2.

[0071] The preparation process of the secondary battery 100 in Comparative Example 4 is basically the same as that in Example 1, except that the second groove segment 1422 of the secondary battery 100 in Comparative Example 4 does not extend from the first end 1422a in a direction away from the notch 13, and accordingly, there is no data of S1 and S2.

[0072] The preparation process of the secondary battery 100 in Comparative Example 5 is basically the same as that in Example 1, except that the first end 1422a of the secondary battery 100 in Comparative Example 5 is arranged at the first part 141.

[0073] The preparation process of the secondary battery 100 in Examples 2 to 4 is basically the same as that in Example 1, except that the length of the second groove segment 1422 in Examples 2 to 4 is different from that in Example 1.

[0074] The preparation process of the secondary battery 100 in Examples 5 to 7 is basically the same as that in Example 1, except that the degree of deviation of the second groove segment 1422 from the reference line 105 in Examples 5 to 7 is different from that in Example 1.

[0075] The preparation process of the secondary battery 100 in Examples 8 to 9 is basically the same as that in Example 1, except that the value of D in Examples 8 to 9 is different from that in Example 1.

[0076] After the preparation of the secondary battery 100 in the comparative examples and examples is completed, the heat box test is performed on all the secondary batteries 100 in each group to observe the explosion of the groove 142. After the test is completed, the experimental results are recorded in Table 1. The specific process of the heat box test is as follows: 1) The secondary battery 100 to be tested is pretreated under the following conditions: after being placed at a test temperature of 20℃ (±5℃) for 60 min, it is discharged at a current of 0.7C to 3.0V, and then placed for 10 min; then it is charged at a current of 0.5C rate to 4.25V, and then charged at a voltage of 4.25V to 0.05C.

[0077] 2) After the pretreatment is completed, the secondary battery 100 is placed vertically in the heat box for testing, wherein the heat box is heated to 130±2℃ at a rate of 5±2℃ / min and maintained for 60 min. During the test, if the pressure relief rate of the secondary battery 100 is greater than the gas generation rate, the secondary battery 100 does not burn or explode, indicating that the heat box test is passed, otherwise the heat box test is failed.

[0078] 3) 100 secondary batteries 100 are tested, and the number of secondary batteries 100 that pass the test is N, then the heat box test pass rate of the experimental secondary batteries 100 in this group is N / 100.

[0079] Table 1 Note: “ / ” in Table 1 indicates that such data are not available.

[0080] According to Example 1 and Comparative Examples 1 to 5, the hot box test pass rates of the secondary batteries 100 in Comparative Examples 1 to 4 were all less than 80 / 100, and the hot box test pass rate of the secondary battery 100 in Example 1 was greater than the hot box test pass rates of the secondary batteries 100 in Comparative Examples 1 to 4. In other words, the present application facilitates improving the pressure relief rate by disposing at least a portion of the first groove section 1421 in the first portion 141, disposing the first end 1422a in the first portion 141, and extending the second groove section 1422 from the first end 1422a away from the notch 13.

[0081] According to Examples 1 to 4, the hot box test pass rate of the secondary batteries 100 in Examples 1 to 4 was greater than 80 / 100. Therefore, it can be seen that the present application further improves the pressure relief rate by setting 0.5mm≤S2. Setting S2≤0.5L1 improves the processing efficiency of the groove 142 and the structural strength of the first wall 14 while maintaining a certain pressure relief rate.

[0082] According to Example 1 and Examples 5 to 7, the hot box test pass rates of the secondary batteries 100 in Examples 1 and Examples 5 to 7 are all greater than 80 / 100. Therefore, it can be seen that the present application is beneficial to further improve the pressure release rate by setting 1≤S1 / S2≤1.5.

[0083] According to Example 1 and Example 8 to Example 9, the hot box test pass rate of the secondary battery 100 in Example 1 and Example 8 to Example 9 is greater than 80 / 100. Therefore, it can be seen that the present application is beneficial to further improve the pressure release rate by setting 0≤D≤0.5L1.

[0084] In addition, those skilled in the art should recognize that the above embodiments are merely intended to illustrate the present application and are not intended to limit the present application. As long as they are within the substantive scope of the present application, appropriate changes and modifications to the above embodiments are within the scope disclosed in the present application.

Claims

1. A secondary battery comprising a housing and an electrode assembly, wherein the electrode assembly is housed in the housing, wherein: The outer shell is a metal shell, and the orthographic projection of the outer shell along a first direction has a notch, where the first direction is the thickness direction of the secondary battery; the orthographic projection of the outer shell along the first direction includes at least a first side, a second side, a third side, and a fourth side connected in sequence, and the boundary of the notch includes the second side and the third side, a first angle between the second side and the third side is α, a second angle between the second side and the third side is β, the first angle and the second angle are mutually combined angles, 0°<α<180°, 180°<β<360°; The housing includes a first wall located on one side in the thickness direction of the secondary battery, the first wall includes a first portion, and the orthographic projection of the first portion along the first direction is formed by a first arc segment, a second arc segment, a first straight line segment, and a second straight line segment; an intersection of an extension line of the second side and an extension line of the third side is defined as a base point, and an angle bisector of an angle between the extension line of the second side and the extension line of the third side is defined as a reference line, the reference line includes a first segment extending from the base point within the first angle, a distance between the base point and the first side along the extension direction of the second side is L1, a distance between the base point and the fourth side along the extension direction of the third side is L2, and L2 ≥ L1; the first The center of the arc segment is set on the first segment, the radius of the first arc segment is L2, and the distance between the center of the first arc segment and the base point is L2; ​​the center of the second arc segment is set on the first segment, the radius of the second arc segment is L2, and the distance between the center of the second arc segment and the base point is L2-L1; the first straight line segment connects the endpoints of the first arc segment and the second arc segment on one side of the reference line, and the second straight line segment connects the endpoints of the first arc segment and the second arc segment on the other side of the reference line, the extension line of the first straight line segment passes through the midpoint of the second side and is parallel to the reference line, and the extension line of the second straight line segment passes through the midpoint of the third side and is parallel to the reference line; A groove is provided on the side of the first wall facing away from the electrode assembly, and the groove includes at least a first groove section and a second groove section connected to each other, and the first groove section is provided in the first part; along the first direction, the positive projection of the first groove section is a circular arc section, and the second groove section includes a first end and a second end, the first end is connected to the first groove section, the first end is located in the first part, and the second end is the end of the groove; in the first direction, the line connecting the center of the first groove section and the base point does not intersect with the first groove section, and the second groove section extends from the first end in a direction away from the notch.

2. The secondary battery according to claim 1, wherein Along the first direction, the orthographic projection of the second slot segment is a straight line segment.

3. The secondary battery according to claim 2, wherein The length of the second slot segment is S1, the length of the orthographic projection of the second slot segment on the reference line is S2, and 1≤S1 / S2≤1.

5.

4. The secondary battery according to claim 3, wherein 1≤S1 / S2≤1.

2.

5. The secondary battery according to claim 3, wherein 0.5mm≤S2≤0.5L1.

6. The secondary battery according to claim 1, wherein The distance between the midpoint of the first groove segment and the base point is D, 0mm≤D≤5mm.

7. The secondary battery according to claim 1, wherein The entire first slot section is provided in the first portion.

8. The secondary battery according to claim 1, wherein The first end is connected to an end point of the first slot segment.

9. The secondary battery according to claim 1, wherein The two endpoints of the first slot segment are respectively located on different sides of a straight line where a line connecting the center of the first slot segment and the base point lies.

10. The secondary battery according to claim 1, wherein The number of the second slot sections is two.

11. An electrical device, characterized in that: The secondary battery according to any one of claims 1 to 10 is included.

Images