Secondary battery and electronic device

Abstract

The invention relates to the technical field of energy storage, and particularly discloses a secondary battery and an electronic device. The secondary battery includes an electrode assembly and a case. The electrode assembly comprises a first sub-pole piece, and the first sub-pole piece comprises a first current collector and a first active material layer; the shell comprises a shell body and a protruding part, the shell body is provided with a containing cavity, and the protruding part extends into the containing cavity; the shell body is provided with a first inner wall, the first inner wall faces the first face, and the protruding part faces the first face and is arranged on the first inner wall in a protruding mode; in the thickness direction of the electrode assembly, the protruding part comprises a first contact end and a second contact end, and the protruding part makes contact with the first sub-pole piece at the first contact end and the second contact end. The first contact end and the second contact end are oppositely arranged from the center of the pole piece to the edge of the pole piece. The distance between the first contact end and the edge of the pole piece is L 1, the distance between the second contact end and the edge of the pole piece is L2, and L2 is greater than or equal to 10mm and L 1 is greater than or equal to 0.2 mm. The warping degree of the outermost layer of the electrode assembly can be improved, and the safe and reliable performance of the electrode assembly can be improved.

Description

Technical Field

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

[0002] As consumers demand ever-faster mobile phone charging speeds, traditional soft-pack wound batteries are no longer able to meet these demands. This has led to the need for steel-cased laminated cells to meet these demands. In steel-cased laminated cells, the outermost layer is a single-sided anode, which is prone to curling at the edges. This can lead to interface issues at the outermost layer, ultimately causing lithium deposition and other issues, impacting the safety and reliability of the cell. Summary of the Invention

[0003] In view of this, it is necessary to provide a secondary battery that can improve the warping degree of the outermost electrode sheet of the electrode assembly and enhance the safety and reliability of the electrode assembly.

[0004] The embodiment of the present application provides a secondary battery, including an electrode assembly and a shell. The electrode assembly includes a first sub-electrode sheet, which is located at the outermost side in the thickness direction of the electrode assembly; the first sub-electrode sheet includes a first current collector and a first active material layer, and along the thickness direction of the first current collector, the first current collector has a first surface and a second surface opposite to each other, the first surface is a hollow foil surface, and the first active material layer is arranged on the second surface; the first sub-electrode sheet includes an edge of the electrode sheet; the shell includes a shell body and a protrusion, the shell body has a receiving cavity, and the protrusion extends into the receiving cavity; the shell body has a first inner wall, and the first inner wall is the cavity wall of the receiving cavity, and the first inner wall is the cavity wall of the receiving cavity. The wall faces the first surface, the protrusion faces the first surface and is protruded from the first inner wall; the protrusion includes a first contact end and a second contact end, and the protrusion contacts the first sub-pole at the first contact end and the second contact end; the first contact end and the second contact end are arranged opposite to each other along the center of the pole piece toward the edge of the pole piece; the distance between the first contact end and the edge of the pole piece is the first contact distance, and the first contact distance is L1; the distance between the second contact end and the edge of the pole piece is the second contact distance, and the second contact distance is L2, satisfying 10mm≥L2, 0.2mm≥L1.

[0005] The protrusion forms a restriction on the first sub-pole sheet in the thickness direction of the electrode assembly by contacting the first sub-pole sheet, inhibiting the first sub-pole sheet from warping toward the first inner wall under the action of the active material layer on the second surface, reducing the degree of warping of the first sub-pole sheet, and thereby reducing problems such as lithium deposition on the surface of the outermost first sub-pole sheet, thereby improving the safety of the secondary battery. The first contact distance and the second contact distance meet the requirements of 10mm ≥ L2 and 0.2mm ≥ L1. On the one hand, 0.2mm ≥ L1 means that the protrusion has at least 0.2mm of contact with the first sub-pole sheet, which is beneficial to improving the degree of warping of the first sub-pole sheet. On the other hand, 10mm ≥ L2 reduces the situation where the protrusion has excessive single-sided contact with the first sub-pole sheet, causing excessive extrusion and affecting the improvement effect.

[0006] In at least one embodiment, the edge of the pole piece includes a first edge, a second edge, a third edge and a fourth edge, the first sub-pole ear extends from the first edge, the second edge is away from the first sub-pole ear and is arranged opposite to the first edge, the third edge and the fourth edge are both connected to the first edge and the second edge, and the third edge is arranged opposite to the fourth edge; the protrusion includes a first part, a second part, a third part and a fourth part.

[0007] The distance between the first contact end of the first part and the first edge is the first distance, which is L11; the distance between the second contact end of the first part and the first edge is the first sub-distance, which is L12; the distance between the first contact end of the second part and the second edge is the second distance, which is L21; the distance between the second contact end of the second part and the second edge is the second sub-distance, which is L22; the distance between the first contact end of the third part and the third edge is the third distance, which is L31; the distance between the second contact end of the third part and the third edge is the third sub-distance, which is L32; the distance between the first contact end of the fourth part and the fourth edge is the fourth distance, which is L41; the distance between the second contact end of the fourth part and the fourth edge is the fourth sub-distance, which is L42; in the length direction of the electrode assembly, the first part and the second part can limit the first sub-pole sheet so that the first sub-pole sheet is not easily warped; in the width direction of the electrode assembly, the third part and the fourth part can limit the first sub-pole sheet so that the first sub-pole sheet is not easily warped.

[0008] In at least one embodiment, the first distance, the first sub-distance, the second distance, the second sub-distance, the third distance, the third sub-distance, the fourth distance, and the fourth sub-distance satisfy: 6mm≥L12, 2mm≥L11, 9mm≥L22, 3mm≥L21, 1.5mm≥L32, 0.5mm≥L31, 1.5mm≥L42, and 0.5mm≥L41.

[0009] On the one hand, compared with the first edge, the third edge and the fourth edge, the warping degree on one side of the second edge is greater. By setting a larger second distance and second sub-distance, the warping at the second edge can be effectively reduced, and the overall lithium deposition area of the electrode can be reduced; on the other hand, each distance and sub-distance is not easy to be too large, which makes it easier for the contact position between the protrusion and the first sub-electrode sheet to be close to the edge of the first sub-electrode sheet, thereby improving the effect of suppressing warping.

[0010] In at least one embodiment, along the thickness direction of the electrode assembly, the thickness of the first portion is D1, and the thickness of the second portion is D2, satisfying D2>D1.

[0011] When D2>D1, compared with the first part, the second part protrudes from the first inner wall by a greater distance, and the second part is easier to contact with the first sub-electrode; in other words, the degree of restriction of the second edge by the second part is greater than the degree of restriction on the first edge, thereby improving the lithium plating problem at the second edge.

[0012] In at least one embodiment, 0≤D2-D1≤50 μm, so that the difference between D2 and D1 is not too large, and the situation where the first portion cannot contact the first sub-pole sheet due to the excessive thickness of the second portion is reduced.

[0013] In at least one embodiment, along the thickness direction of the electrode assembly, the thickness of the third portion is D3, and the thickness of the fourth portion is D4, satisfying D2>D3>D1, and D2>D4>D1.

[0014] In the absence of a protrusion, the warping degree of the second edge, the third edge, the fourth edge, and the first edge gradually decreases, that is, the second edge is most susceptible to warping and has the most lithium deposition. The third and fourth edges have basically the same degree of lithium deposition, and the first edge has the least lithium deposition. When D2>D3>D1, D2>D4>D1 are satisfied, the thickness of the second part, the thickness of the third and fourth parts, and the thickness of the first part decrease in sequence, so that the second part protrudes most from the first inner wall. Compared with the third edge, the fourth edge, and the first edge, the second edge is subjected to greater pressure, thereby improving the warping problem of the second edge and reducing the lithium deposition area of the first sub-electrode.

[0015] In at least one embodiment, 40 ≤ D1 ≤ 50 μm, 50 ≤ D3 ≤ 70 μm, and 50 ≤ D4 ≤ 70 μm. Compared to the third and fourth portions, the first portion has a smaller thickness. This minimizes the thickness of the protrusion corresponding to one side of the first sub-tab. This allows the protrusion to prevent the first edge from warping while also preventing the opposite side of the tab from being severely warped due to excessive force on one side of the tab.

[0016] In at least one embodiment, along the length direction of the electrode assembly, the width of the first portion is W1, and the width of the second portion is W2, satisfying: W2>W1.

[0017] When the first sub-electrode sheet is not restricted by the protrusion, the side of the first sub-electrode sheet opposite the first sub-electrode tab is most susceptible to warping and has the largest lithium deposition area. This is followed by the sides along the width of the first sub-electrode sheet. The side with the first sub-electrode tab has relatively less warping and a smaller lithium deposition area. When W2>W1, increasing the contact area between the second portion and the second edge of the electrode sheet is more effective in suppressing electrode warping than increasing the contact area between the first portion and the first edge of the electrode sheet, thereby alleviating the more severe lithium deposition problem on the second edge.

[0018] In at least one embodiment, along the width direction of the electrode assembly, the width of the third portion is W3, and the width of the fourth portion is W4, satisfying: W2>W3>W1, W2>W4>W1.

[0019] In the absence of a protrusion, the warping degree of the second edge, the third edge, the fourth edge, and the first edge gradually decreases, that is, the second edge is most susceptible to warping and has the most lithium deposition. The degree of lithium deposition at the third and fourth edges is basically the same, and the first edge has the least lithium deposition. Accordingly, when W2>W3>W1, W2>W4>W1 are satisfied, the width of the contact between the pole piece on the second edge side and the second part is also larger, and the width of the contact between the pole piece on the first edge side and the first part is smaller. The width of each part of the protrusion is set according to the degree of lithium deposition at each edge, so as to effectively reduce the warping of the first sub-pole piece and reduce the lithium deposition area.

[0020] In at least one embodiment, the electrode assembly has a width K, 0.005K≤W1≤0.01K. Compared with the first edge, the third and fourth edges have a greater degree of lithium deposition. Therefore, W3 and W4 are set to be relatively large so that the third part and the fourth part can contact the third and fourth edges respectively, thereby improving the restriction on the third and fourth edges and improving the overall lithium deposition of the first sub-electrode sheet.

[0021] In at least one embodiment, the width W2 of the second portion satisfies: 0.1K≤W2≤0.2K.

[0022] W2 ≥ 0.1K prevents the width of the second portion from being too small, ensuring sufficient contact surface between the second portion and the pole piece on the second edge, thereby limiting warping of the second edge. W2 ≤ 0.2K reduces the material usage of the housing and reduces the production cost of the housing.

[0023] In at least one embodiment, the first portion, the third portion, the second portion, and the fourth portion are sequentially connected end to end. The end-to-end connection of the protrusions facilitates forming a continuous limit for the edge along the circumferential direction of the edge, thereby making it less likely for the edge to warp at any position along the circumferential direction.

[0024] In at least one embodiment, the shell body and the protrusion are integrally formed. This integral arrangement facilitates the shell body and the protrusion being made of the same material, thereby reducing assembly steps and simplifying the manufacturing process of the shell.

[0025] In at least one embodiment, the shell body and the protrusion are separately provided. By providing the shell body and the protrusion separately, it is advantageous to manufacture the shell body and the protrusion with different materials according to needs and then assemble them.

[0026] In at least one embodiment, the protrusion is made of polyethylene or hot-melt adhesive. Polyethylene or hot-melt adhesive has excellent electrical insulation and water resistance, which helps improve the safety of secondary batteries. Furthermore, hot-melt adhesive has adhesive properties that can adhere to the electrode assembly, thereby limiting relative movement between the electrode assembly and the housing.

[0027] In at least one embodiment, the electrode assembly is square. The edge of the first sub-electrode piece in the square electrode assembly is easy to identify, and it is easy to set a corresponding protrusion according to the position of the edge of the electrode piece, and it is also easier to produce the shell.

[0028] In at least one embodiment, the thickness of the protrusion is D5, which satisfies 40 μm≤D5≤100 μm.

[0029] D5 ≥ 40 μm ensures that the protrusion has sufficient thickness to contact the first sub-electrode and apply pressure to the edge of the electrode to prevent warping. D5 ≤ 100 μm prevents the protrusion from being too thick, reducing overpressure. If the pressure of the protrusion is too high, it will cause overpressure and deteriorate the improvement effect.

[0030] In at least one embodiment, along the length direction of the electrode assembly, the side of the first part away from the second part is the first side, the shell body has a second inner wall, the second inner wall is arranged opposite to the first side, and the part of the first inner wall located between the first side and the second inner wall is the welding area; no protrusion is set in the welding area, and the welding area is electrically connected to the first sub-pole ear.

[0031] No protrusion is provided between the first side and the second inner wall, thereby forming a welding zone. The welding zone provides a welding space for the first sub-electrode tab to be connected to the first inner wall of the shell body, and also facilitates the partial accommodation of the first sub-electrode tab in the welding zone, reducing the risk of short circuit in the electrode assembly.

[0032] In at least one embodiment, along the length direction of the electrode assembly, the length of the welding area is L, which satisfies: 1 mm ≤ L ≤ 3 mm.

[0033] The length of the welding zone satisfies the requirement of L ≥ 1 mm, preventing the welding zone from being too small. This allows the first sub-electrode tab to be electrically conductively transferred through the transfer weld at the welding zone, reducing the risk of short circuits in the electrode assembly. If the welding zone is too large, the distance between the first portion and the edge of the second inner wall increases, hindering contact between the first portion and the first edge. Therefore, L ≤ 3 mm prevents the welding zone from being too large, facilitating contact between the first portion and the first edge, and limiting warping of the first edge.

[0034] An embodiment of the present application further provides an electronic device, comprising the secondary battery in any of the above embodiments.

[0035] By contacting the edge of the electrode piece with the protrusion, the first sub-electrode piece is restricted in the thickness direction of the electrode assembly, thereby suppressing the warping of the edge of the electrode piece toward the first inner wall, reducing the degree of warping of the edge of the first sub-electrode piece, and thereby reducing problems such as lithium plating on the surface of the outermost first sub-electrode piece, thereby improving the safety of secondary battery use and the safety of electronic devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 is a schematic diagram of a secondary battery in one embodiment of the present application.

[0037] Figure 2 1 is an exploded view of a secondary battery according to an embodiment of the present application.

[0038] Figure 3 Schematic diagram of an electrode assembly according to an embodiment of the present application.

[0039] Figure 4 This is a cross-sectional view of the first sub-pole piece and the protrusion in an embodiment of the present application.

[0040] Figure 5 This is a schematic diagram of the cooperation between the first sub-pole piece and the protrusion in an embodiment of the present application.

[0041] Figure 6 Schematic diagram of the first shell of an embodiment of the present application.

[0042] Figure 7 An embodiment of the present application is a cross-sectional view showing the first part and the second part.

[0043] Figure 8 This is a cross-sectional view showing the third part and the fourth part according to an embodiment of the present application.

[0044] Figure 9 This is a schematic diagram of an embodiment of the present application showing the matching relationship between the protrusion and the edge of the pole piece.

[0045] Figure 10 FIG. 1 is a schematic diagram showing the thickness of a protrusion according to an embodiment of the present application.

[0046] Figure 11 This is a partial cross-sectional view showing a welding area according to an embodiment of the present application.

[0047] Figure 12 This is a cross-sectional view of an embodiment of the present application showing the matching relationship between the electrode assembly and the protrusion.

[0048] Figure 13 is a schematic diagram of an electronic device according to an embodiment of the present application.

[0049] Description of main component symbols

[0050] Secondary battery 100

[0051] Electrode assembly 10

[0052] The first pole piece 11

[0053] The first sub-electrode piece 11a

[0054] The second sub-electrode piece 11b

[0055] First current collector 111

[0056] First side 1111

[0057] Second side 1112

[0058] First contact end 1113a

[0059] Second contact end 1113b

[0060] First contact distance L1

[0061] Second contact distance L2

[0062] First distance L11

[0063] The first sub-distance L12

[0064] Second distance L21

[0065] The second sub-distance L22

[0066] The third distance L31

[0067] The third sub-distance L32

[0068] Fourth distance L41

[0069] Fourth sub-distance L42

[0070] First active material layer 112

[0071] First Tab 113

[0072] The second pole piece 12

[0073] Second current collector 121

[0074] Second active material layer 122

[0075] Second sub-tab 123

[0076] Diaphragm 13

[0077] First edge 131

[0078] Second edge 132

[0079] Third edge 133

[0080] Fourth Edge 134

[0081] Housing 20

[0082] protrusion 21

[0083] Part 1 211

[0084] First side 2111

[0085] Part 2212

[0086] Part III 213

[0087] Part 4 214

[0088] Shell body 22

[0089] First shell portion 22a

[0090] Second shell portion 22b

[0091] Accommodating chamber 221

[0092] First inner wall 222

[0093] Second inner wall 223

[0094] Welding area 224

[0095] Electronic device 200

[0096] Device body 201

[0097] First direction Z

[0098] Second direction X

[0099] The third direction Y

[0100] The following specific implementation methods will further illustrate the present application in conjunction with the above-mentioned drawings. DETAILED DESCRIPTION

[0101] The technical solutions in the embodiments of the present application will be described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments.

[0102] In the description of the embodiments of this application, the technical terms "first," "second," etc. are used only to distinguish different objects and should not be understood to indicate or imply relative importance or to implicitly indicate 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 specifically defined.

[0103] As consumers demand faster and faster charging speeds for their mobile phones, traditional soft-pack wound batteries are no longer able to meet these requirements. This has led to the need for steel-shell laminated battery cells to meet consumer demand. In steel-shell laminated batteries, the outermost layer of the battery cell is a single-sided anode electrode. The edges of the single-sided anode electrode are prone to curling, which leads to interface problems at the outermost layer, ultimately causing lithium plating and other problems in the outermost layer of the battery cell, affecting the safety and reliability of the battery cell.

[0104] An embodiment of the present application provides a secondary battery, including an electrode assembly and a housing. The electrode assembly includes a first sub-pole sheet, which is located at the outermost side in the thickness direction of the electrode assembly; the first sub-pole sheet includes a first current collector and a first active material layer, and along the thickness direction of the first current collector, the first current collector has a first surface and a second surface relative to each other, the first surface is a hollow foil surface, and the first active material layer is arranged on the second surface; the first sub-pole sheet includes a pole piece edge, the shell includes a shell body and a protrusion, the shell body has a accommodating cavity, and the protrusion extends into the accommodating cavity; the shell body has a first inner wall, and the first inner wall is the cavity wall of the accommodating cavity, the first inner wall faces the first surface, and the protrusion faces the first surface and is protruded from the first inner wall; the protrusion includes a first contact end and a second contact end, and the protrusion contacts the first sub-pole sheet at the first contact end and the second contact end; the first contact end and the second contact end are arranged opposite to each other along the center of the pole piece toward the edge of the pole piece; the distance between the first contact end and the edge of the pole piece is a first contact distance L1, and the distance between the second contact end and the edge of the pole piece is a second contact distance L2, satisfying 10mm≥L2, 0.2mm≥L1.

[0105] The protrusion forms a restriction on the first sub-pole sheet in the thickness direction of the electrode assembly by contacting the first sub-pole sheet, inhibiting the first sub-pole sheet from warping toward the first inner wall under the action of the active material layer on the second surface, reducing the degree of warping of the first sub-pole sheet, and further reducing problems such as lithium deposition on the surface of the outermost first sub-pole sheet, thereby improving the safety of secondary batteries. The first contact distance and the second contact distance meet the requirements of 10mm ≥ L2 and 0.2mm ≥ L1. On the one hand, 0.2mm ≥ L1 means that the protrusion has at least 0.2mm of contact with the first sub-pole sheet, which is beneficial to improving the degree of warping of the first sub-pole sheet. On the other hand, 10mm ≥ L2 reduces the situation where the protrusion has excessive single-sided contact with the first sub-pole sheet, causing excessive extrusion and affecting the improvement effect.

[0106] The embodiments of the present application are further described below with reference to the accompanying drawings.

[0107] like Figures 1 to 3 As shown, the first embodiment of the present application provides a secondary battery 100, which includes an electrode assembly 10 and a housing 20. The electrode assembly 10 is accommodated in the housing 20. The electrode assembly 10 includes a first electrode sheet 11, a second electrode sheet 12, and a diaphragm 13. The diaphragm 13 is disposed between the first electrode sheet 11 and the second electrode sheet 12, and is used to separate the first electrode sheet 11 and the second electrode sheet 12.

[0108] See also Figure 3 It can be understood that in some embodiments, a plurality of first pole pieces 11, diaphragms 13 and second pole pieces 12 are respectively provided, and the first pole pieces 11, diaphragms 13 and second pole pieces 12 are stacked in sequence to form a stacked structure, and a diaphragm 13 is provided between each first pole piece 11 and each second pole piece 12.

[0109] In some embodiments, the housing 20 is a hard shell, such as a plastic shell, or a metal shell including at least one of a steel alloy, an aluminum alloy, and a copper alloy.

[0110] In some embodiments, an electrolyte (not shown) is injected into the housing 20 , and the electrolyte components include a solvent, an electrolyte salt, and an additive.

[0111] In some embodiments, the electrolyte salt includes at least one of an organic lithium salt or an inorganic lithium salt.

[0112] In some embodiments, the electrolyte salt includes but is not limited to at least one of lithium hexafluorophosphate (LiPF6), lithium bis(trifluoromethanesulfonyl)imide LiN(CF3SO2)2 (LiTFSI), lithium bis(fluorosulfonyl)imide Li(N(SO2F)2) (LiFSI), lithium hexafluorocesium oxide (LiCsF6), lithium perchlorate (LiClO4) or lithium trifluoromethanesulfonate (LiCF3SO3).

[0113] In some embodiments, the first electrode 11 and the second electrode 12 have different polarities. For example, the first electrode 11 is an anode electrode and the second electrode 12 is a cathode electrode. For another example, the first electrode 11 is a cathode electrode and the second electrode 12 is an anode electrode.

[0114] See also Figure 3 In some embodiments, the first electrode sheet 11 includes a first current collector 111 and a first active material layer 112. The first active material layer 112 is disposed on at least one surface of the first current collector 111 along the thickness direction of the first current collector 111. The separator 13 is disposed between the first active material layer 112 and the second electrode sheet 12. The thickness direction of the first current collector 111 is the first direction Z.

[0115] See also Figure 3 In some embodiments, the second electrode sheet 12 includes a second current collector 121 and a second active material layer 122. Along the thickness direction of the second electrode sheet 12, the second current collector 121 has two opposing surfaces, and the thickness direction of the second electrode sheet 12 coincides with the thickness direction of the second current collector 121. At least one of the second current collectors 121 is provided with the second active material layer 122.

[0116] See also Figure 2 The first pole piece 11 further includes a first sub-pole tab 113 , which is welded to the first current collector 111 ; the second pole piece 12 further includes a second sub-pole tab 123 , which is welded to the second current collector 121 .

[0117] In some embodiments, the first sub-tab 113 and the second sub-tab 123 are disposed on the same side or different sides of the electrode assembly 10 .

[0118] Taking the first electrode piece 11 as an anode electrode piece and the second electrode piece 12 as a cathode electrode piece as an example, the first current collector 111 and the second current collector 121 can be metal layers. The first current collector 111 can be a metal layer including at least one of copper, nickel, tantalum, titanium, etc., such as copper foil. The second current collector 121 can be a metal layer including at least one of aluminum, nickel, tantalum, titanium, etc., such as aluminum foil.

[0119] Taking the first electrode 11 as an anode electrode and the second electrode 12 as a cathode electrode as an example, the polarity of the first active material layer 112 is anodic, and the first active material layer 112 includes an anode active material. The anode active material may include at least one of graphite, hard carbon, soft carbon, silicon, silicon-oxygen material, silicon-carbon material, etc. The polarity of the second active material layer 122 is cathodic, and the second active material layer 122 includes a cathode active material. The cathode active material may include at least one of lithium cobalt oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium iron phosphate, lithium manganese iron phosphate, or lithium manganese oxide, etc.

[0120] In the related art, during the manufacturing process of the stacked electrode assembly 10, it is usually required that the outermost electrode of the electrode assembly 10 remain straight to prevent curling of the outermost electrode. However, because the outermost electrode is only provided with active material on one side, the forces on both sides of the current collector are uneven, and the electrode is prone to curling toward the side where the active material is not provided. Moreover, the closer the electrode is to the edge, the greater the degree of warping, which leads to various interface problems, which further affects the safety and reliability of the battery cell. Interface problems refer to problems such as black spots and lithium deposition on the surface of the electrode. After the electrode is warped, the electrode is separated from the diaphragm 13 and the adjacent electrode, and there is a lack of electrolyte between the electrode pieces, which blocks the lithium ion transmission path and causes interface problems.

[0121] See also Figure 3 In some embodiments, the first electrode sheet 11 includes a first sub-electrode sheet 11a, which is located at the outermost side of the electrode assembly 10 in the thickness direction. Along the thickness direction of the first current collector 111, the first sub-electrode sheet 11a has a first surface 1111 and a second surface 1112 that are opposite to each other. The first surface 1111 is a hollow foil surface, and the first active material layer 112 is disposed on the second surface 1112. The hollow foil surface is not provided with the first active material.

[0122] See also Figure 3 In some embodiments, the first electrode piece 11 includes a second sub-electrode piece 11 b , the second sub-electrode piece 11 b is located between two diaphragms 13 , and the first active material layer 112 is provided on both sides of the second sub-electrode piece 11 b .

[0123] Please refer to Figure 4 The protrusion 21 includes a first contact end 1113a and a second contact end 1113b. The protrusion 21 contacts the first sub-pole sheet 11a at the first contact end 1113a and the second contact end 1113b.

[0124] See also Figure 2 、 Figure 4 、 Figure 5 and Figure 6The shell 20 includes a shell body 22 and a protrusion 21. The shell body 22 has a receiving cavity 221, and the protrusion 21 extends into the receiving cavity 221. The shell body 22 has a first inner wall 222, and the first inner wall 222 serves as the cavity wall of the receiving cavity 221. The first inner wall 222 faces the first surface 1111, and the protrusion 21 faces the first surface 1111 and protrudes from the first inner wall 222. The first sub-electrode sheet 11a includes an edge of the electrode sheet. Along the thickness direction of the electrode assembly 10, the first contact end 1113a and the second contact end 1113b are arranged opposite each other along the center of the electrode sheet toward the edge of the electrode sheet; the distance between the first contact end 1113a and the edge of the electrode sheet is a first contact distance L1, and the distance between the second contact end 1113b and the edge of the electrode sheet is a second contact distance L2. The thickness direction of the electrode assembly 10 and the thickness direction of the secondary battery 100 are both the first direction Z.

[0125] The protrusion 21 restricts the first sub-pole sheet 11a in the thickness direction of the electrode assembly 10 by contacting the first sub-pole sheet 11a, thereby suppressing the first sub-pole sheet 11a from warping toward the first inner wall 222 under the action of the active material layer on the second surface 1112, reducing the degree of warping of the first sub-pole sheet 11a, and thereby reducing problems such as lithium plating on the surface of the outermost first sub-pole sheet 11a, thereby improving the safety of the secondary battery 100.

[0126] In some embodiments, the distance between the first contact end 1113a and the edge of the pole piece is a first contact distance L1, and the distance between the second contact end 1113b and the edge of the pole piece is a second contact distance L2, satisfying 10mm≥L2, 0.2mm≥L1.

[0127] The first contact distance L1 and the second contact distance L2 satisfy 10mm≥L2, 0.2mm≥L1. On the one hand, 0.2mm≥L1, the protrusion 21 has at least 0.2mm of contact with the first sub-pole piece 11a, which is beneficial to improving the warping degree of the first sub-pole piece 11a; on the other hand, 10mm≥L2, reduces the excessive single-sided contact between the protrusion 21 and the first sub-pole piece 11a, causing excessive extrusion and affecting the improvement effect.

[0128] See also Figure 5In some embodiments, the distance between the first contact end 1113a of the first portion 211 and the first edge 131 is a first distance L11, the distance between the second contact end 1113b of the first portion 211 and the first edge 131 is a first sub-distance L12, the distance between the first contact end 1113a of the second portion 212 and the second edge 132 is a second distance L21, the distance between the second contact end 1113b of the second portion 212 and the second edge 132 is a second sub-distance L22, the distance between the first contact end 1113a of the third portion 213 and the third edge 133 is a third distance L31, and the distance between the second contact end 1113b of the third portion 213 and the third edge 133 is a third distance L32. The distance between the first contact end 1113a of the fourth part 214 and the fourth edge 134 is a fourth distance L41, and the distance between the second contact end 1113b of the fourth part 214 and the fourth edge 134 is a fourth sub-distance L42. In the length direction of the electrode assembly 10, the first part 211 and the second part 212 can limit the first sub-pole piece 11a, so that the first sub-pole piece 11a is not easy to warp; in the width direction of the electrode assembly 10, the third part 213 and the fourth part 214 can limit the first sub-pole piece 11a, so that the first sub-pole piece 11a is not easy to warp.

[0129] Please refer to Figure 6 and Figure 7 The protruding portion 21 includes a first portion 211 , a second portion 212 , a third portion 213 and a fourth portion 214 , and the second portion 212 contacts the second edge 132 .

[0130] In related art, the tab at the head of the pole piece is connected to the adapter. When the adapter is subjected to pressure, a lever effect is formed, which tilts the tail of the pole piece upward, making the tail of the tab more prone to warping. When the housing 20 does not have the protrusion 21 and the first sub-pole piece 11a is not restricted by the protrusion 21, the side of the first sub-pole piece 11a opposite the first sub-pole tab 113 is most likely to warp, followed by both sides of the first sub-pole piece 11a in the width direction. The side with the first sub-pole tab 113 is relatively less prone to warping.

[0131] The second edge 132 corresponds to the opposite side of the first sub-pole ear 113. By contacting the second part 212 with the pole piece on one side of the second edge 132, when the second edge 132 has a tendency to warp toward the first inner wall 222, the second part 212 can apply a force to the second edge 132, and the direction of the force is opposite to the direction of warping, thereby limiting the warping of the second edge 132 and reducing the lithium deposition area of the first sub-pole piece 11a.

[0132] See also Figure 6 and Figure 7In some embodiments, the first portion 211 contacts the electrode on one side of the first edge 131. The first portion 211 can limit the first edge 131 from warping toward the first inner wall 222, thereby suppressing lithium deposition at the first edge 131 and reducing the lithium deposition area of the first sub-electrode 11a.

[0133] See also Figure 8 and Figure 9 In some embodiments, the third portion 213 contacts the electrode on one side of the third edge 133. The third portion 213 can prevent the third edge 133 from warping toward the first inner wall 222, thereby suppressing lithium deposition at the third edge 133 and reducing the lithium deposition area of the first sub-electrode 11a. Figure 8 The solid line portion in FIG. 2 is used to illustrate the housing 20 , and the dotted line portion is used to illustrate the first sub-pole piece 11 a .

[0134] See also Figure 8 and Figure 9 In some embodiments, the fourth portion 214 contacts the fourth edge 134. The fourth portion 214 can limit the fourth edge 134 from warping toward the first inner wall 222, thereby suppressing lithium deposition at the fourth edge 134 and reducing the lithium deposition area of the first sub-electrode sheet 11a.

[0135] In at least one embodiment, the first distance L11, the first sub-distance L12, the second distance L21, the second sub-distance L22, the third distance L31, the third sub-distance L32, the fourth distance L41, and the fourth sub-distance L42 satisfy: 6mm≥L12, 2mm≥L11, 9mm≥L22, 3mm≥L21, 1.5mm≥L32, 0.5mm≥L31, 1.5mm≥L42, and 0.5mm≥L41.

[0136] On the one hand, compared with the first edge 131, the third edge 133 and the fourth edge 134, the warping degree on the second edge 132 side is greater. By setting a larger second distance L21 and a second sub-distance L22, the warping at the second edge 132 can be effectively reduced, and the overall lithium deposition area of the electrode can be reduced; on the other hand, each distance and sub-distance is not easy to be too large, which makes it easier for the contact position of the protrusion 21 and the first sub-electrode sheet 11a to be close to the edge of the first sub-electrode sheet 11a, thereby improving the effect of suppressing warping.

[0137] See also Figure 7 In some embodiments, along the thickness direction of the electrode assembly 10 , the thickness of the first portion 211 is D1 , and the thickness of the second portion 212 is D2 , satisfying D2 > D1 .

[0138] When D2>D1, compared with the first part 211, the second part 212 protrudes from the first inner wall 222 by a greater distance, and the second part 212 is easier to contact with the first sub-pole piece 11a; in other words, the degree of restriction of the second part 212 on the second edge 132 is greater than the degree of restriction of the first part 211 on the first edge 131, thereby improving the lithium plating problem of the first sub-pole piece 11a.

[0139] In some embodiments, 0≤D2-D1≤50 μm, so that the difference between D2 and D1 is not too large, thereby reducing the situation where the first portion 211 cannot contact the first edge 131 due to the excessive thickness of the second portion 212.

[0140] See also Figure 10 In some embodiments, along the thickness direction of the electrode assembly 10 , the thickness of the third portion 213 is D3 , and the thickness of the fourth portion 214 is D4 , satisfying D2 > D3 > D1 , and D2 > D4 > D1 .

[0141] In the absence of the protrusion 21, the warping degree of the second edge 132, the third edge 133, the fourth edge 134, and the first edge 131 gradually decreases, that is, the second edge 132 is most susceptible to warping and has the most lithium deposition. The third edge 133 and the fourth edge 134 have basically the same degree of lithium deposition, and the first edge 131 has the least lithium deposition. When D2>D3>D1 and D2>D4>D1 are satisfied, the thickness of the second portion 212, the thickness of the third portion 213 and the fourth portion 214, and the thickness of the first portion 211 decrease in sequence, so that the second portion 212 protrudes most from the first inner wall 222. Compared with the third edge 133, the fourth edge 134, and the first edge 131, the second edge 132 is subjected to greater pressure, thereby improving the warping problem of the second edge 132 and reducing the lithium deposition area of the first sub-electrode 11a.

[0142] In some embodiments, the thickness D5 of the protrusion 21 satisfies 40 μm ≤ D5 ≤ 100 μm. For example, the thickness of the protrusion 21 can be, but is not limited to, any one of 40 μm, 45 μm, 50 μm, 55 μm, 60 μm, 65 μm, 70 μm, 75 μm, 80 μm, 95 μm, 90 μm, 95 μm, and 100 μm.

[0143] D5 ≥ 40 μm ensures that the protrusion 21 has sufficient thickness to facilitate contact between the protrusion 21 and the first sub-electrode sheet 11a and apply pressure to the edge of the electrode sheet to prevent warping of the first sub-electrode sheet 11a. D5 ≤ 100 μm prevents the protrusion 21 from being too thick, thus reducing overpressure. If the pressure of the protrusion 21 is too high, it will cause overpressure problems, resulting in a deterioration of the improvement effect.

[0144] In some embodiments, 40≤D1≤50μm, 50≤D3≤70μm, and 50≤D4≤70μm. The first portion 211 has a smaller thickness than the third portion 213 and the fourth portion 214. This minimizes the thickness of the protrusion 21 on the corresponding portion of the tab side. This allows the protrusion 21 to prevent the first edge 131 from warping while also preventing the tab side from warping due to excessive force on one side.

[0145] See also Figure 6 In some embodiments, along the length of the electrode assembly 10, the width of the first portion 211 is W1, and the width of the second portion 212 is W2, satisfying the following: W2>W1. The width of the first portion 211 coincides with the width of the second portion 212, both being in the length direction of the electrode assembly 10. The width of the third portion 213 coincides with the width of the fourth portion 214, both being in the width direction of the electrode assembly 10.

[0146] When the first sub-electrode sheet 11a is not restricted by the protrusion 21, the side of the first sub-electrode sheet 11a opposite the first sub-electrode tab 11a is most susceptible to warping and has the largest lithium deposition area. The sides along the width of the first sub-electrode sheet 11a are next most susceptible to warping. The side with the first sub-electrode tab 11a is relatively less warped and has a smaller lithium deposition area. When W2>W1, increasing the contact area between the second portion 212 and the electrode sheet on the second edge 132 is more effective in suppressing electrode warping than increasing the contact area between the first portion 211 and the electrode sheet on the first edge 131 side, thereby alleviating the more severe lithium deposition problem on the second edge 132 side.

[0147] See also Figure 6 In some embodiments, along the width direction of the electrode assembly 10 , the width of the third portion 213 is W3 , and the width of the fourth portion 214 is W4 , satisfying: W2 > W3 > W1 , W2 > W4 > W1 .

[0148] When W2>W3>W1 and W2>W4>W1 are satisfied, the contact width between the electrode on the second edge 132 side and the second portion 212 is larger, and the contact width between the electrode on the first edge 131 side and the first portion 211 is smaller. The width of each part of the protrusion 21 is set accordingly according to the lithium deposition width of the electrode on each edge of the first sub-electrode sheet 11a, thereby effectively reducing the warping of the first sub-electrode sheet 11a and reducing the lithium deposition area.

[0149] In some embodiments, the width of the electrode assembly 10 is K. 0.005K≤W1≤0.01K. Compared with the first edge 131, the third edge 133 and the fourth edge 134 have a greater degree of lithium deposition. Therefore, W3 and W4 are set to be relatively large so that the third portion 213 and the fourth portion 214 can contact the third edge 133 and the fourth edge 134 respectively, thereby increasing the degree of restriction on the third edge 133 and the fourth edge 134 and improving the overall lithium deposition of the first sub-electrode sheet 11a.

[0150] See also Figure 2 In some embodiments, the width W2 of the second portion 212 satisfies the following: 0.1K ≤ W2 ≤ 0.2K. W2 ≥ 0.1K prevents the width of the second portion 212 from being too small, ensuring sufficient contact surface between the second portion 212 and the pole piece on the second edge 132, thereby limiting warping of the second edge 132. W2 ≤ 0.2K also helps reduce material usage and production costs of the housing 20.

[0151] See also Figure 6 In some embodiments, the first portion 211, the third portion 213, the second portion 212, and the fourth portion 214 are sequentially connected end to end. The end-to-end connection of the protrusions 21 facilitates continuous positioning of the first sub-pole piece 11a along the direction of the perimeter of the pole piece, thereby preventing warping at any position along the perimeter of the first sub-pole piece 11a.

[0152] It is understandable that in other embodiments, there may be gaps between the beginning and the end of the first portion 211 , the third portion 213 , the second portion 212 , and the fourth portion 214 .

[0153] See also Figure 6 In some embodiments, the housing body 22 and the protrusion 21 are integrally formed. This integral configuration facilitates the housing body 22 and the protrusion 21 being made of the same material, reducing assembly steps and simplifying the manufacturing process of the housing 20. For example, the housing body 22 and the protrusion 21 are integrally formed using an injection molding process.

[0154] In some embodiments, the shell body 22 and the protrusion 21 are provided separately. This separate arrangement facilitates the shell body 22 and the protrusion 21 to be manufactured from different materials as needed and then assembled. The shell body 22 and the protrusion 21 can be assembled by welding, bonding, etc.

[0155] In some embodiments, the material of the protrusion 21 is polyethylene or hot-melt adhesive. Polyethylene or hot-melt adhesive has good electrical insulation and water resistance, which helps improve the safety of the secondary battery 100. In addition, the hot-melt adhesive has adhesive properties and can adhere to the electrode assembly 10, thereby limiting the relative movement between the electrode assembly 10 and the housing 20.

[0156] See also Figure 2 In some embodiments, the electrode assembly 10 is square. The edge of the first sub-electrode piece 11a in the square electrode assembly 10 is easy to identify, and it is easy to set the corresponding protrusion 21 according to the position of the electrode piece edge, which also makes the production of the housing 20 easier.

[0157] See also Figure 2 and Figure 6 In some embodiments, the shell body 22 includes a first shell portion 22a and a second shell portion 22b, the first shell portion 22a and the second shell portion 22b are covered to form a receiving cavity 221, and the protrusion 21 is provided on the first shell portion 22a or the second shell portion 22b.

[0158] See also Figure 7 and Figure 11 In some embodiments, along the length of the electrode assembly 10, the side of the first portion 211 away from the second portion 212 is the first side 2111. The shell body 22 has a second inner wall 223, which is disposed opposite the first side 2111. The portion of the first inner wall 222 between the first side 2111 and the second inner wall 223 is the welding region 224. The welding region 224 is not provided with the protrusion 21, and the welding region 224 is electrically connected to the first sub-electrode tab 11a. Specifically, the first inner wall 222 of the welding region 224 is electrically connected to the first sub-electrode tab 11a via an adapter (not shown), thereby conducting electrical conduction of the electrode assembly 10.

[0159] No protrusion 21 is provided between the first side 2111 and the second inner wall 223, thereby forming a welding region 224. The welding region 224 provides a welding space for the first sub-electrode tab 11a to be connected to the first inner wall 222 of the shell body 22. This also facilitates the partial accommodation of the first sub-electrode tab 11a within the welding region 224, thereby reducing the risk of short circuiting of the electrode assembly 10.

[0160] In some embodiments, the plurality of first sub-tabs 113 are folded and stacked between the electrode assembly 10 and the second inner wall 223 , and the folded plurality of first sub-tabs 113 are electrically connected to the welding area 224 via the adapter.

[0161] See also Figure 11 In some embodiments, the length L of the welding region 224 along the length direction of the electrode assembly 10 satisfies the following conditions: 1 mm ≤ L ≤ 3 mm. For example, the length L of the welding region 224 can be, but is not limited to, any one of 1 mm, 1.5 mm, 2 mm, 2.5 mm, and 3 mm.

[0162] The length of the welding area 224 satisfies L ≥ 1 mm, preventing the welding area 224 from being too small. This allows the first sub-electrode tab 11a to be electrically conductively transferred through the transfer weld at the welding area 224, thereby reducing the risk of short circuiting in the electrode assembly 10. If the welding area 224 is too large, the distance between the first edge 131 and the edge of the second inner wall 223 increases, hindering contact between the first portion 211 and the first edge 131. Therefore, L ≤ 3 mm prevents the welding area 224 from being too large, facilitating contact between the first portion 211 and the first edge 131, and preventing warping of the first edge 131.

[0163] See also Figure 3 and Figure 12 In some embodiments, the electrode assembly 10 has two outermost portions in the thickness direction, and both outermost portions are the first sub-electrode sheet 11a. Accordingly, the housing 20 has two first inner walls 222 in the thickness direction, each of which is provided with a protrusion 21 to prevent warping of the edge of the corresponding first sub-electrode sheet 11a.

[0164] See also Figure 13 The present application also provides an electronic device 200, which includes the secondary battery 100 of any of the above embodiments. The protrusion 21 contacts the first sub-electrode sheet 11a, thereby restricting the first sub-electrode sheet 11a in the thickness direction of the electrode assembly 10. This prevents the edge of the electrode sheet from warping toward the first inner wall 222, reduces the degree of warping of the first sub-electrode sheet 11a, and further reduces problems such as lithium deposition on the surface of the outermost first sub-electrode sheet 11a. This improves the safety of the secondary battery 100 and the safety of the electronic device 200.

[0165] In some embodiments, the electronic device 200 includes a device body 201, and the secondary battery 100 is disposed in the device body 201. The device body 201 can be a mobile phone, a laptop computer, a tablet computer, a drone, a power tool, an electric toy, a game console, a video recorder, a portable recorder, a radio or a smart watch, etc., which are not listed one by one here.

[0166] To verify the effect of the protrusion 21 on the performance of the secondary battery 100, the inventors conducted the following experiments:

[0167] The experiment includes two groups of comparative examples and 18 groups of embodiments. The configuration of the protrusions 21 in each comparative example and embodiment is shown in Table 1 below.

[0168] The specific implementation of the secondary battery 100 in the examples and comparative examples will be described below.

[0169] The assembly process of the secondary battery 100 in the comparative example and the embodiment is as follows:

[0170] (1) Preparation of cathode electrode: The active materials lithium cobalt oxide (LiCoO2), conductive carbon black (Super P), CNT (carbon nanotube), and polyvinylidene fluoride (PVDF) are mixed in a weight ratio of 97.5:0.5:0.5:1.5, and N-methylpyrrolidone (NMP) is added as a solvent to prepare a cathode active material with a solid content of 75wt%, and stirred evenly for use. Aluminum foil with a thickness of 10um is used as the cathode current collector. The above active material is evenly coated on one side of the cathode current collector using a slit coater, and then dried at 90°C to obtain a cathode electrode with a single-sided coating of cathode active material. At this time, the thickness of the cathode active material layer along the thickness direction of the cathode current collector is 90um. The above coating steps are then repeated on the other side of the cathode current collector. The coated cathode electrode is then cold pressed. After cold pressing, the thickness of the cathode active material layer on one side is 80um. The cathode tab is then die-cut from the portion of the cathode current collector that is not covered by the cathode active material layer. The cathode electrode is the second electrode 12 .

[0171] (2) Preparation of anode electrode: Active materials artificial graphite, conductive carbon black (Super P), styrene-butadiene rubber (SBR), and CMC (sodium carboxymethyl cellulose) are mixed in a weight ratio of 97:0.5:1.3:1.2, deionized water is added as a solvent, and the mixture is prepared into an anode active material material with a weight percentage of 50 wt%, and stirred evenly for use. A copper foil with a thickness of 10 μm is used as the anode current collector. The above-mentioned anode active material material is evenly coated on one side of the anode current collector using a slit coater, and then dried at 110°C to obtain an anode electrode sheet coated with an anode active material layer on one side, and then the above steps are repeated on the other side of the anode current collector to obtain an anode electrode sheet coated with an anode active material layer on both sides. At this time, the thickness of the anode active material layer on both sides along the thickness direction of the anode current collector is 90 μm. The coated anode electrode sheet is then cold-pressed, and the thickness of the anode active material layer on one side after cold pressing is 80 μm. Thereafter, the anode tab is die-cut out from the portion of the anode current collector that is not covered by the anode active material layer. It should be noted that there are multiple anode plates prepared in this step, of which two anode plates are coated with an anode active material layer only on one side of the anode current collector to serve as the two outermost first sub-plates 11a of the electrode assembly 10;

[0172] (3) Preparation of electrolyte: In a dry argon atmosphere, ethylene carbonate (EC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC) were first mixed in a mass ratio of EC:EMC:DEC = 30:50:20 to form a basic organic solvent. Then, lithium salt lithium hexafluorophosphate (LiPF6) was added to the basic organic solvent to dissolve and mix evenly to obtain an electrolyte with a lithium salt concentration of 1.15 mol / L.

[0173] (4) Preparation of diaphragm: A 7 μm thick polyethylene porous polymer film was used as the diaphragm.

[0174] (5) Preparation of electrode assembly 10: The cathode electrode sheet, the separator and the anode electrode sheet are stacked along the thickness direction of the anode electrode sheet to obtain the electrode assembly 10. The electrode sheet coated with the anode active material layer on one side is located at the outermost side in the thickness direction of the electrode sheet.

[0175] (6) Assembly of the secondary battery 100: The electrode assembly 10 is placed in the second shell 22b, and the first shell 22a and the second shell 22b are welded. The secondary battery 100 is then manufactured through the following steps: electrolyte injection, packaging, static storage, and hot pressing.

[0176] The manufacturing process of the secondary battery 100 in Comparative Examples 1-2 is substantially the same as that in Example 3, except that the protrusion 21 in Comparative Example 1 is in full contact with the first surface 1111 of the first sub-electrode sheet 11a. The manufacturing process of the secondary battery 100 in Comparative Example 2 is substantially the same as that in Example 3, except that the protrusion 21 is not provided in Comparative Example 2. The secondary batteries 100 in different groups of examples differ only in the parameters listed above; all other aspects are the same.

[0177] After the secondary batteries 100 in Comparative Examples 1-2 and Examples 1-18 were prepared, the following tests were performed on the secondary batteries 100 in the group.

[0178] 1. Lithium deposition area ratio test:

[0179] Remove the first sub-electrode sheet 11a from the secondary battery 100;

[0180] Clean the residual electrolyte on the surface of the first sub-electrode sheet 11a;

[0181] Lay the first sub-electrode piece 11a flat on the stage to avoid wrinkles or warping that may affect imaging;

[0182] A high-resolution CCD camera is used to capture the surface image of the first sub-pole piece 11a;

[0183] The lithium deposition area is identified through image processing algorithm and the lithium deposition area is calculated.

[0184] To calculate the lithium deposition area, first take a photo of the entire first sub-electrode sheet 11a, identify the lithium deposition area by color difference, then divide the entire first sub-electrode sheet 11a into multiple squares of equal area. The lithium deposition area is calculated by multiplying the number of squares occupied by the lithium deposition area by the area of each square. The lithium deposition area is displayed in black, and the area without lithium deposition is displayed in yellow.

[0185] After the lithium deposition area of the first sub-electrode piece 11 a is calculated, the lithium deposition area is divided by the area of the first sub-electrode piece 11 a to obtain the ratio of the lithium deposition area.

[0186] The experimental results are shown in Table 1 below:

[0187] Table 1

[0188]

[0189]

[0190] Note: 1. In Table 1, “ / ” indicates that the data is not available;

[0191] 2. In addition to the parameters shown in Table 1, in each embodiment and comparative example, the length of the electrode assembly 10 was set to 60 mm and the width was set to 55 mm. The thickness of the electrode assembly 10 was 7.4 mm, and a gap was formed between the first sub-electrode sheet 11a and the inner wall of the housing 20. The gap was 0.5% of the thickness of the electrode assembly 10, that is, the gap was 37 μm.

[0192] It can be seen from Comparative Examples 1-2 and Examples 1 to 5 that when the protrusion 21 of the shell 20 is in full contact with the first surface 1111, the first sub-electrode 11a will be over-pressurized, which will make the edge of the electrode more prone to warping. Compared with the case where no protrusion 21 is set in Comparative Example 2, when the area of the protrusion 21 is too large in Comparative Example 1, the proportion of lithium deposition area of the electrode is larger.

[0193] By comparing Comparative Example 2 with Examples 1 to 5, it can be seen that the first sub-electrode sheet 11a can be effectively reduced in proportion to the lithium deposition area of the first sub-electrode sheet 11a after being limited by the protrusion 21. Specifically, when the width of the protrusion 21 is between 0.2 mm and 10 mm, the protrusion 21 fully contacts the edge of the first sub-electrode sheet 11a, thereby suppressing warping of the first sub-electrode sheet 11a.

[0194] As can be seen from Examples 6 to 12, when the thickness D5 of the protrusion 21 is ≥ 40 μm, the protrusion 21 has sufficient thickness to facilitate contact between the protrusion 21 and the first sub-electrode sheet 11a, thereby limiting warping of the first sub-electrode sheet 11a; when D5 is ≤ 100 μm, the thickness of the protrusion 21 is not too large, thereby reducing the situation where warping and lithium deposition caused by overpressure are reduced. As can be seen from Examples 6 and 12, when D5 is less than 40 μm, the protrusion 21 is insufficient to suppress warping of the first sub-electrode sheet 11a, and when D5 is greater than 100 μm, excessive pressure is applied. Both situations reduce the effect of suppressing lithium deposition.

[0195] As can be seen from Examples 13 to 17, compared to the first portion 211, the third portion 213, and the fourth portion 214, the improvement effect on lithium deposition is best when the thickness of the second portion 212 is the largest, and as the thickness of the second portion 212 increases, the proportion of the electrode area where lithium deposition occurs gradually decreases. When D2>D3>D1 and D2>D4>D1 are satisfied, the position where the protrusion 21 has the largest thickness can contact the position where the first sub-electrode sheet 11a is most susceptible to warping, and the position where the thickness is the smallest can contact the position where the first sub-electrode sheet 11a is least warped, thereby achieving a better effect in suppressing lithium deposition.

[0196] As can be seen from Examples 18 to 23, compared to the first portion 211, the third portion 213, and the fourth portion 214, when the width of the second portion 212 is the largest, that is, when W2>W3>W1 and W2>W4>W1 are satisfied, the improvement effect on lithium deposition is better. When W2>W3>W1 and W2>W4>W1 are satisfied, the second portion 212 corresponding to the second edge 132 that is most prone to warping can be set wider, which is more conducive to reducing lithium deposition.

[0197] 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 spirit of the present application, appropriate changes and modifications to the above embodiments are within the scope of disclosure of the present application.

Claims

1. A secondary battery, characterized in that: include: An electrode assembly, the electrode assembly comprising a first sub-electrode sheet, the first sub-electrode sheet being located at the outermost side in the thickness direction of the electrode assembly; the first sub-electrode sheet comprising a first current collector and a first active material layer, wherein along the thickness direction of the first current collector, the first current collector has a first surface and a second surface opposite to each other, the first surface being a hollow foil surface, the first active material layer being disposed on the second surface, and the first sub-electrode sheet comprising an electrode sheet edge; A shell, the shell comprising a shell body and a protrusion, the shell body having an accommodating cavity, the protrusion extending into the accommodating cavity; the shell body having a first inner wall, and the first inner wall being the cavity wall of the accommodating cavity, the first inner wall facing the first surface, the protrusion facing the first surface and protruding from the first inner wall; the protrusion comprising a first contact end and a second contact end, the protrusion contacting the first sub-pole piece at the first contact end and the second contact end, the first contact end and the second contact end being arranged opposite to each other along the center of the pole piece toward the edge of the pole piece; The distance between the first contact end and the edge of the pole piece is a first contact distance, which is L1; the distance between the second contact end and the edge of the pole piece is a second contact distance, which is L2, satisfying 10mm≥L2, 0.2mm≥L1.

2. The secondary battery according to claim 1, wherein The first sub-electrode piece includes a first sub-electrode tab, and the electrode piece edges include a first edge, a second edge, a third edge, and a fourth edge. The first sub-electrode tab extends from the first edge, the second edge is away from the first sub-electrode tab and is arranged opposite to the first edge, the third edge and the fourth edge are both connected to the first edge and the second edge, and the third edge is arranged opposite to the fourth edge. The protrusion includes a first portion, a second portion, a third portion and a fourth portion; The distance between the first contact end of the first part and the first edge is a first distance, which is L11. The distance between the second contact end of the first part and the first edge is a first sub-distance, which is L12. The distance between the first contact end of the second part and the second edge is a second distance, which is L21. The distance between the second contact end of the second part and the second edge is a second sub-distance, which is L22. The distance between the first contact end of the third part and the third edge is a third distance, which is L31. The distance between the second contact end of the third part and the third edge is a third sub-distance, which is L32. The distance between the first contact end of the fourth part and the fourth edge is a fourth distance, which is L41. The distance between the second contact end of the fourth part and the fourth edge is a fourth sub-distance, which is L42.

3. The secondary battery according to claim 2, wherein The first distance, the first sub-distance, the second distance, the second sub-distance, the third distance, the third sub-distance, the fourth distance, and the fourth sub-distance satisfy: 6mm≥L12, 2mm≥L11, 9mm≥L22, 3mm≥L21, 1.5mm≥L32, 0.5mm≥L31, 1.5mm≥L42, and 0.5mm≥L41.

4. The secondary battery according to claim 2, wherein Along the thickness direction of the electrode assembly, the thickness of the first portion is D1, and the thickness of the second portion is D2, satisfying D2>D1.

5. The secondary battery according to claim 4, wherein 0≤D2-D1≤50μm.

6. The secondary battery according to claim 2, wherein Along the thickness direction of the electrode assembly, the thickness of the third portion is D3, and the thickness of the fourth portion is D4, satisfying D2>D3>D1, and D2>D4>D1.

7. The secondary battery according to claim 6, wherein 40≤D1≤50μm, 50≤D3≤70μm, 50≤D4≤70μm.

8. The secondary battery according to claim 2, wherein Along the length direction of the electrode assembly, the width of the first portion is W1, and the width of the second portion is W2, satisfying: W2>W1.

9. The secondary battery according to claim 8, wherein The width of the electrode assembly is K, 0≤W2-W1≤0.1K.

10. The secondary battery according to claim 8, wherein Along the width direction of the electrode assembly, the width of the third portion is W3, and the width of the fourth portion is W4, satisfying: W2>W3>W1, W2>W4>W1.

11. The secondary battery according to claim 10, wherein The width of the electrode assembly is K, 0.005K≤W1≤0.01K.

12. The secondary battery according to any one of claims 8 to 11, wherein The width of the electrode assembly is K, which satisfies: 0.1K≤W2≤0.2K.

13. The secondary battery according to claim 2, wherein The first part, the third part, the second part and the fourth part are connected end to end in sequence.

14. The secondary battery according to claim 1, wherein The shell body and the protruding portion are an integrally formed structure.

15. The secondary battery according to claim 14, wherein The protrusion is a hollow structure.

16. The secondary battery according to claim 1, wherein The shell body and the protruding portion are separately arranged.

17. The secondary battery according to claim 16, wherein The material of the protrusion is polyethylene or hot melt adhesive.

18. The secondary battery according to claim 1, wherein The electrode assembly is square.

19. The secondary battery according to any one of claims 1 to 11 and 13 to 18, wherein The thickness of the protruding portion is D5, which satisfies 40 μm≤D5≤100 μm.

20. The secondary battery according to claim 2, wherein The first sub-electrode piece is an anode piece.

21. The secondary battery according to claim 2, wherein Along the length direction of the electrode assembly, the side of the first part away from the second part is the first side, the shell body has a second inner wall, the second inner wall is arranged opposite to the first side, and the part of the first inner wall located between the first side and the second inner wall is the welding area; the protrusion is not provided in the welding area, and the welding area is electrically connected to the first sub-pole ear.

22. The secondary battery according to claim 21, wherein Along the length direction of the electrode assembly, the length of the welding area is L, which satisfies: 1mm≤L≤3mm.

23. An electronic device, characterized in that: The secondary battery according to any one of claims 1 to 21 is included.

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