Secondary battery and electronic device

Abstract

The invention discloses a secondary battery and an electronic device. The secondary battery comprises a packaging bag, an electrode assembly and a bonding piece, a cavity is formed in the packaging bag, and a groove is formed in the inner wall, facing the cavity, of the packaging bag. The electrode assembly is disposed in the chamber. One side of the bonding piece is bonded with the electrode assembly, the other side of the bonding piece is bonded with the groove, and at least part of the bonding piece is arranged in the groove. The groove is formed in the packaging bag, at least part of the bonding piece is contained in the groove, and the projection of the bonding piece is located in the groove in the thickness direction of the electrode assembly. In this way, the electrode assembly and the packaging bag can be fixed through the bonding piece, the electrode assembly is not prone to shaking in a cavity of the packaging bag in the falling test, and the falling test passing rate of the secondary battery can be improved. And compared with the scheme that the bonding piece is directly bonded on the inner wall of the packaging bag or the bonding piece is thickened, the scheme has the advantages that the overall thickness of the electrode assembly is not easily increased, and the volume energy density loss of the secondary battery is favorably reduced.

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] At present, due to the need of customers to drop, the existing battery cell structure needs to stick adhesive tape between the bare battery cell and the packaging bag, but sticking adhesive tape will increase the thickness of the battery cell, thereby reducing the energy density of the secondary battery. In the related art, the impact on the thickness of the battery cell is reduced by thinning the adhesive tape, but because the adhesive tape is thin, it is more likely to wrinkle during automatic sticking, which will cause the battery cell to partially thicken, which will still reduce the energy density of the secondary battery. Summary of the invention

[0003] In view of this, it is necessary to provide a secondary battery and an electronic device that can reduce the loss of volume energy density of the secondary battery while improving the pass rate of the drop test of the secondary battery.

[0004] The embodiment of the first aspect of the present application provides a secondary battery, comprising: a packaging bag, an electrode assembly, and an adhesive. The packaging bag is formed with a chamber, and a groove is provided on the inner wall of the packaging bag facing the chamber. The electrode assembly is arranged in the chamber. One side of the adhesive is bonded to the electrode assembly, and the other side is bonded to the groove, at least part of the adhesive is arranged in the groove, and along the thickness direction of the electrode assembly, the projection of the adhesive is located in the groove.

[0005] In the above-mentioned secondary battery, a groove is provided on the packaging bag and at least a part of the adhesive is accommodated in the groove, so that the adhesive can fix the electrode assembly to the packaging bag, making it difficult for the electrode assembly to shake in the cavity of the packaging bag during the drop test, which is beneficial to improving the pass rate of the drop test of the secondary battery; and compared with the solution of directly sticking the adhesive to the inner wall of the packaging bag or thickening the adhesive, the above-mentioned solution is not easy to increase the overall thickness of the electrode assembly, which is beneficial to reducing the volume energy density loss of the secondary battery.

[0006] In at least one of the above embodiments, along the thickness direction of the electrode assembly, the adhesive members are all disposed in the grooves.

[0007] In the above embodiment, by setting the adhesive entirely in the groove, the setting of the adhesive does not increase the thickness of the electrode assembly; compared with the situation where no groove is set and the adhesive is directly adhered to the inner wall of the packaging bag, the thickness of the electrode assembly is reduced and the energy density of the secondary battery is improved.

[0008] In at least one of the above embodiments, the packaging bag includes a first layer, a second layer, and a third layer stacked in sequence, the first layer is located at the outermost layer of the packaging bag, and the second layer is a metal layer; along the thickness direction of the packaging bag, the thickness of the third layer is H, and the depth of the groove is H1, satisfying: 0.5H≤H1≤0.75H.

[0009] In the above embodiment, when H1≥0.5H is satisfied, it is beneficial for the groove to accommodate part of the adhesive; when H1≤0.75H is satisfied, the thickness of the third layer at the groove is not too thin, reducing the risk of damaging the metal layer when thinning the third layer, and also reducing the risk of short circuit caused by exposure of the metal layer.

[0010] In at least one of the above embodiments, 0.7H≤H1≤0.75H.

[0011] In the above embodiment, H1≥0.7H, which is beneficial for accommodating as many adhesives as possible in the groove in the thickness direction of the electrode assembly, minimizing the increase in the thickness of the electrode assembly, and further beneficial for reducing the volume energy density loss of the secondary battery.

[0012] In at least one of the above embodiments, the first layer is a nylon layer, and / or the third layer is a polypropylene layer.

[0013] In at least one of the above embodiments, the electrode assembly includes a pole ear, which is arranged on one side of the length direction of the electrode assembly; the edges of the packaging bag are surrounded by a packaging area, and the groove has a first edge and a second edge that are relatively arranged along the length direction of the electrode assembly, and a third edge and a fourth edge that are relatively arranged along the width direction of the electrode assembly, and the first edge and the pole ear are located on the same side of the electrode assembly; along the length direction of the electrode assembly, the minimum distance between the first edge and the packaging area is P1, satisfying: 10mm≤P1≤15mm, and the minimum distance between the second edge and the packaging area is P2, satisfying: 10mm≤P2≤15mm; and / or, along the width direction of the electrode assembly, the minimum distance between the third edge and the packaging area is P3, satisfying: 5mm≤P3≤13mm, and the minimum distance between the fourth edge and the packaging area is P4, satisfying: 5mm≤P4≤13mm.

[0014] In the above-mentioned embodiments, if the edge of the groove is too close to the packaging area, when the adhesive is pasted in the groove, the adhesive is easy to enter the packaging area, thereby affecting the sealing of the packaging. If the edge of the groove is too far away from the packaging area, the occupied area of ​​the groove will be reduced, which is not conducive to the setting of the adhesive. When P1≥10mm, P2≥10mm, P3≥5mm, and P4≥5mm are satisfied, the first edge and the second edge of the groove are not easy to be too close to the packaging area, which is conducive to reducing the risk of the adhesive entering the packaging area and affecting the sealing of the packaging bag. When P1≤15mm, P2≤15mm, P3≤13mm, and P4≤13mm are satisfied, the area of ​​the groove is not easy to be too small, which is conducive to setting a larger adhesive.

[0015] In at least one of the above embodiments, the packaging bag includes a first part and a second part, the first part and the second part are enclosed to form a cavity; the depth of the first part is greater than the depth of the second part, and the groove is arranged in the first part.

[0016] In the above-mentioned embodiment, relative to the second part, the first part can cover more parts of the electrode assembly, thereby improving the installation stability of the electrode assembly on the first part, and making it difficult for the electrode assembly to shake relative to the first part; the groove is arranged in the first part, and the adhesive is located in the first part, so that the adhesive is not easy to move relative to the packaging bag.

[0017] In at least one of the above embodiments, the electrode assembly is a wound structure, the electrode assembly includes a main body and a tail portion, the adhesive adheres the tail portion and the main body, and the adhesive is adhered between the tail portion and the packaging bag.

[0018] In the above embodiment, the adhesive of the tail portion can not only fix the tail portion so that the tail portion is fixed to the main body and is not prone to wrinkles, but also fix the electrode assembly to the packaging bag so that the electrode assembly is not prone to shaking relative to the packaging bag.

[0019] In at least one of the above embodiments, the adhesive comprises a first adhesive layer, a substrate layer and a second adhesive layer stacked in sequence, the first adhesive layer is bonded to the packaging bag, the second adhesive layer is bonded to the electrode assembly, the first adhesive layer is a hot melt adhesive layer, and the second adhesive layer is a pressure-sensitive adhesive layer.

[0020] In the above-mentioned embodiment, the viscosity of the hot melt adhesive layer is activated after being subjected to high temperature and high pressure. This arrangement enables, when assembling a secondary battery, the adhesive member can be first bonded to the electrode assembly through the pressure-sensitive adhesive layer, and then the electrode assembly bonded with the adhesive member is placed in a packaging bag, and finally the viscosity of the hot melt adhesive layer is activated by high temperature and high pressure, so that the hot melt adhesive layer is bonded to the packaging bag. During the process of placing the electrode assembly into the packaging bag, the viscosity of the hot melt adhesive layer is not activated, so that it is not easy for the adhesive member to bond to the packaging bag during the process of placing the electrode assembly into the packaging bag, which facilitates the placement of the electrode assembly into the packaging bag.

[0021] In at least one of the above embodiments, along the thickness direction of the electrode assembly, the projected area of ​​the adhesive is less than or equal to the area of ​​the groove.

[0022] In the above embodiment, when the projected area of ​​the adhesive is smaller than the area of ​​the groove, the groove can provide installation margin for the adhesive in the length and width directions of the electrode assembly, reducing the situation where the adhesive cannot be accommodated in the groove due to inaccurate positioning of the adhesive and the groove. When the projected area of ​​the adhesive is equal to the area of ​​the groove, the groove can accommodate the adhesive in the length and width directions of the electrode assembly, reducing the situation where the adhesive is attached outside the groove and increases the overall thickness of the electrode assembly.

[0023] In at least one of the above embodiments, along the depth direction of the groove, the thickness of the adhesive is H2, which satisfies: 10um≤H2≤25um.

[0024] In the above embodiment, when H2≤25um, the thickness of the adhesive is not easy to be too large, which reduces the situation of local bulges in the packaging bag and reduces the influence of the thickness of the adhesive on the volume energy density of the secondary battery. When H2≥10um, the adhesive is not easy to be too thin. If the adhesive is too thin, it is easy to cause wrinkles during pasting. H2≥10um is conducive to reducing the risk of local adhesive failure caused by wrinkling of the adhesive and reducing the risk of falling failure while improving the volume energy density of the secondary battery.

[0025] In at least one of the above embodiments, the groove includes a side wall and a bottom wall, and a side of the adhesive member facing away from the electrode assembly is bonded to the bottom wall.

[0026] The above-mentioned embodiment is helpful to increase the contact area between the adhesive and the packaging bag, and improve the firmness of the bonding between the adhesive and the packaging bag.

[0027] An embodiment of the second aspect of the present application further provides an electronic device, comprising the secondary battery in any of the above embodiments.

[0028] In the above-mentioned electronic device, a groove is provided on the packaging bag and at least a portion of the adhesive is accommodated in the groove, so that the adhesive can fix the electrode assembly to the packaging bag, making it difficult for the electrode assembly to shake in the cavity of the packaging bag during a drop test, which is beneficial to improving the pass rate of the drop test of the secondary battery and increasing the service life of the electronic device. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 is a three-dimensional diagram of a secondary battery in one embodiment of the present application.

[0030] Figure 2 It is a three-dimensional diagram of a packaging bag in an embodiment of the present application in an unfolded state.

[0031] Figure 3 It is a three-dimensional diagram of an electrode assembly and an adhesive in one embodiment of the present application.

[0032] Figure 4 is a cross-sectional view of a secondary battery in one embodiment of the present application.

[0033] Figure 5 yes Figure 4 Enlarged view of part V.

[0034] Figure 6 It is a partial cross-sectional view of a packaging bag in one embodiment of the present application.

[0035] Figure 7 It is a partial cross-sectional view showing a packaging bag and an adhesive member in one embodiment of the present application.

[0036] Figure 8 is a top view of a secondary battery in one embodiment of the present application.

[0037] Fig. 9 yes Figure 2 Enlarged view of part IX.

[0038] Fig.10 is a cross-sectional view of a secondary battery in one embodiment of the present application.

[0039] Fig.11 It is a partial cross-sectional view of an adhesive member in one embodiment of the present application.

[0040] Fig.12 is a schematic diagram of an electronic device in one embodiment of the present application.

[0041] Main component symbols 1000, electronic device; 100, secondary battery; 10, electrode assembly; 10a, main body; 10b, tail; 11, first pole piece; 12, second pole piece; 13, diaphragm; 14, pole ear; 141, first pole ear; 142, second pole ear; 20, packaging bag; 20a, first part; 20b, second part; 21, chamber; 22, groove; 221, first edge; 222, second edge; 223, third edge; 224, fourth edge; 225, side wall; 226, bottom wall; 23, first layer; 24, second layer; 25, third layer; 26, packaging area; 261, first area; 262, second area; 263, third area; 264, fourth area; 30, adhesive; 31, first adhesive layer; 32, substrate layer; 33, second adhesive layer; 200, device body; X, first direction; Y, second direction; Z, third direction.

[0042] The following specific implementation methods will further illustrate the present application in conjunction with the above-mentioned drawings. DETAILED DESCRIPTION

[0043] 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 of the embodiments.

[0044] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0045] In the description of the embodiments of the present application, technical terms such as "first" and "second" are only used to distinguish different objects and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features.

[0046] At present, due to the need of customers to drop, the existing battery cell structure needs to stick adhesive tape between the bare battery cell and the packaging bag, but sticking adhesive tape will increase the thickness of the battery cell, thereby reducing the energy density of the secondary battery. In the related art, the impact on the thickness of the battery cell is reduced by thinning the adhesive tape, but because the adhesive tape is thin, it is more likely to wrinkle during automatic sticking, which will cause the battery cell to partially thicken, which will still reduce the energy density of the secondary battery.

[0047] An embodiment of the present application provides a secondary battery, comprising: a packaging bag, an electrode assembly, and an adhesive. The packaging bag is formed with a chamber, and a groove is provided on the inner wall of the packaging bag facing the chamber. The electrode assembly is arranged in the chamber. One side of the adhesive is bonded to the electrode assembly, and the other side is bonded to the groove, and at least a portion of the adhesive is arranged in the groove.

[0048] In the above-mentioned secondary battery, a groove is provided on the packaging bag and at least a part of the adhesive is accommodated in the groove, so that the adhesive can fix the electrode assembly to the packaging bag, so that the electrode assembly is not easy to shake in the cavity of the packaging bag during the drop test, which is beneficial to improving the pass rate of the drop test of the secondary battery; and compared with the solution of directly sticking the adhesive to the inner wall of the packaging bag or thickening the adhesive, along the thickness direction of the electrode assembly, the projection of the adhesive is located in the groove, which is not easy to increase the overall thickness of the electrode assembly, which is beneficial to reduce the volume energy density loss of the secondary battery.

[0049] The following is combined with Figures 1 to 12 , the embodiments of the present application are further described.

[0050] like Figures 1 to 3As shown, an embodiment of the present application provides a secondary battery 100 , which includes an electrode assembly 10 and a packaging bag 20 . The packaging bag 20 is formed with a chamber 21 , and the electrode assembly 10 is accommodated in the chamber 21 .

[0051] See also Figure 3 and Figure 4 The electrode assembly 10 includes a first electrode piece 11 , a second electrode piece 12 and a diaphragm 13 . The diaphragm 13 is disposed between the first electrode piece 11 and the second electrode piece 12 . The diaphragm 13 is used to isolate the first electrode piece 11 from the second electrode piece 12 .

[0052] In some embodiments, the packaging bag 20 is a flexible packaging bag 20, such as an aluminum-plastic film. In other embodiments, the packaging bag 20 is a hard shell, such as a plastic shell, or a metal shell including at least one of steel alloy, aluminum alloy, and copper alloy.

[0053] In some embodiments, the packaging bag 20 is injected with an electrolyte (not shown), and the electrolyte components include a solvent, an electrolyte salt, and an additive.

[0054] In some embodiments, the electrolyte salt includes at least one of an organic lithium salt or an inorganic lithium salt.

[0055] 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).

[0056] In some embodiments, the polarities of the first electrode 11 and the second electrode 12 are different. For example, the first electrode 11 is a negative electrode, and the second electrode 12 is a positive electrode. For another example, the first electrode 11 is a positive electrode, and the second electrode 12 is a negative electrode.

[0057] In some embodiments, the first pole piece 11 includes a first current collector and a first active material layer, the first active material layer is disposed on at least one surface of the first current collector along the thickness direction of the first current collector, and the separator 13 is disposed between the first active material layer and the second pole piece 12. For example, the first active material layer is disposed on both surfaces of the first current collector along the thickness direction of the first current collector.

[0058] In some embodiments, the second pole piece 12 includes a second current collector and a second active material layer, and the second active material layer is disposed on at least one surface of the second current collector along the thickness direction of the second current collector. For example, the second active material layer is disposed on both surfaces of the second current collector along the thickness direction of the second current collector.

[0059] See also Figure 1 and Figure 3 In some embodiments, the electrode assembly 10 includes a pole tab 14 , and the pole tab 14 includes a first pole tab 141 and a second pole tab 142 . The first pole tab 141 is welded to the first current collector, and the second pole tab 142 is welded to the second current collector.

[0060] Taking the first electrode sheet 11 as a negative electrode sheet and the second electrode sheet 12 as a positive electrode sheet as an example, the first current collector and the second current collector may be metal layers. The first current collector may be a metal layer including at least one of copper, nickel, tantalum, titanium, etc., such as copper foil. The second current collector may be a metal layer including at least one of aluminum, nickel, tantalum, titanium, etc., such as aluminum foil.

[0061] Taking the first electrode sheet 11 as a negative electrode sheet and the second electrode sheet 12 as a positive electrode sheet as an example, the polarity of the first active material layer is negative electrode, the first active material layer includes negative electrode active materials, and the negative electrode active materials 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 is positive electrode, the second active material layer includes positive electrode active materials, and the positive electrode active materials 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.

[0062] See also Figure 4 In some embodiments, the first pole piece 11, the diaphragm 13 and the second pole piece 12 are stacked in sequence to form a stacked structure.

[0063] See also Figure 4 and Figure 5 In some embodiments, the secondary battery 100 includes an adhesive 30. The inner wall of the packaging bag 20 facing the chamber 21 is provided with a groove 22. The electrode assembly 10 is disposed in the chamber 21. One side of the adhesive 30 is bonded to the electrode assembly 10, and the other side is bonded to the groove 22, and at least a portion of the adhesive 30 is disposed in the groove 22.

[0064] By setting a groove 22 on the packaging bag 20 and accommodating at least a portion of the adhesive 30 in the groove 22, the adhesive 30 can fix the electrode assembly 10 to the packaging bag 20, so that the electrode assembly 10 is not easy to shake in the cavity 21 of the packaging bag 20 during the drop test, which is beneficial to improving the drop test pass rate of the secondary battery 100.

[0065] In the related art, in order to improve the drop performance of the secondary battery 100, a glue wrap is set on the electrode assembly 10, but the glue wrap will increase the thickness of the electrode assembly 10, resulting in a decrease in the volume energy density of the secondary battery 100. In order to reduce the influence of the glue wrap thickness on the thickness of the electrode assembly 10, the problem is improved by thinning the adhesive tape. However, the thinned adhesive tape is prone to wrinkling when pasting, and there are two problems after wrinkling: one is that the electrode assembly 10 is locally thickened and the packaging bag 20 is bulging; the other is that the glue sticking rate of the electrode assembly 10 is reduced, the cost is increased, and the wrinkled adhesive tape leads to local bonding failure, which is easy to cause the risk of drop failure.

[0066] Compared with the solution of directly sticking the adhesive 30 to the inner wall of the packaging bag 20, thickening the adhesive 30 and setting a wrapping adhesive, the solution of the embodiment of the present application can reduce the volume energy density loss of the secondary battery 100 while reducing the increase in the overall thickness of the electrode assembly 10.

[0067] See also Figure 6 In some embodiments, along the thickness direction of the electrode assembly 10, the adhesive member 30 is entirely disposed in the groove 22. The thickness direction of the electrode assembly 10 is the first direction X shown in the figure.

[0068] By setting the adhesive 30 entirely in the groove 22, the setting of the adhesive 30 does not increase the thickness of the electrode assembly 10; compared with the situation where the groove 22 is not set and the adhesive 30 is directly adhered to the inner wall of the packaging bag 20, the thickness of the electrode assembly 10 is reduced and the energy density of the secondary battery 100 is improved.

[0069] See also Figure 7 In some embodiments, along the depth direction of the groove 22, the thickness of the adhesive 30 is H2, satisfying: 10um≤H2≤25um. When H2≤25um, the thickness of the adhesive 30 is not easy to be too large, which reduces the situation of local bulges of the packaging bag 20 and reduces the influence of the thickness of the adhesive 30 on the volume energy density of the secondary battery 100. When H2≥10um, the adhesive 30 is not easy to be too thin. If the adhesive 30 is too thin, it is easy to cause wrinkles during pasting. H2≥10um is beneficial to reduce the risk of local bonding failure caused by wrinkling of the adhesive 30 and reduce the risk of failure of the secondary battery 100 due to falling, while improving the volume energy density of the secondary battery 100.

[0070] In some embodiments, the thickness H2 of the adhesive 30 may be set to, but not limited to, 10um, 12um, 14um, 15um, 17um, 19um, 20um, 22um, 24um or 25um.

[0071] See also Figure 7In some embodiments, the packaging bag 20 includes a first layer 23, a second layer 24, and a third layer 25 stacked in sequence, the first layer 23 is located at the outermost layer of the packaging bag 20, and the second layer 24 is a metal layer. Along the thickness direction of the packaging bag 20, the thickness of the third layer 25 is H, and the depth of the groove 22 is H1, which satisfies: 0.5H≤H1≤0.75H.

[0072] When H1≥0.5H is satisfied, the groove 22 can accommodate part of the adhesive 30; when H1≤0.75H is satisfied, the thickness of the third layer 25 at the groove 22 is not too thin, reducing the risk of damaging the metal layer when thinning the third layer 25, and also reducing the risk of short circuit caused by exposure of the metal layer.

[0073] In some embodiments, 0.7H≤H1≤0.75H. H1≥0.7H is conducive to accommodating as many adhesives 30 as possible in the thickness direction of the electrode assembly 10 in the groove 22, minimizing the increase in thickness of the electrode assembly 10, and further conducive to reducing the volume energy density loss of the secondary battery 100.

[0074] In some embodiments, first layer 23 is a nylon layer.

[0075] In some embodiments, the metal layer of the second layer 24 is an aluminum material.

[0076] In some embodiments, the third layer 25 is a PP (Polypropylene) layer.

[0077] See also Figure 8 In some embodiments, the tab 14 is disposed on one side of the length direction of the electrode assembly 10. The length direction of the electrode assembly 10 is the second direction Y shown in the figure. The packaging bag 20 has a packaging area 26 on the edges around it, and the groove 22 has a first edge 221 and a second edge 222 that are oppositely disposed along the length direction of the electrode assembly 10, and a third edge 223 and a fourth edge 224 that are oppositely disposed along the width direction of the electrode assembly 10. The first edge 221 and the tab 14 are located on the same side of the electrode assembly 10. The width direction of the electrode assembly 10 is the third direction Z shown in the figure.

[0078] Along the second direction Y, the minimum distance between the first edge 221 and the packaging area 26 is P1, satisfying: 10 mm≤P1≤15 mm, and the minimum distance between the second edge 222 and the packaging area 26 is P2, satisfying: 10 mm≤P2≤15 mm.

[0079] If the edge of the groove 22 is too close to the packaging area 26, when the adhesive 30 is pasted in the groove 22, the adhesive 30 is easy to enter the packaging area 26, thereby affecting the sealing of the packaging. If the edge of the groove 22 is too far from the packaging area 26, the occupied area of ​​the groove 22 will be reduced, which is not conducive to the setting of the adhesive 30. When P1≥10mm and P2≥10mm are satisfied, the first edge 221 and the second edge 222 of the groove 22 are not too close to the packaging area 26, which is conducive to reducing the risk of the adhesive 30 entering the packaging area 26 and affecting the sealing of the packaging bag 20; and when P1≥10mm is satisfied, it is conducive to making the adhesive 30 avoid the position of the tab 14, reducing the risk of the adhesive 30 and the tab 14 overlapping in the thickness direction of the electrode assembly 10, which is conducive to reducing the overall thickness of the electrode assembly 10. When P1≤15mm and P2≤15mm are satisfied, the area of ​​the groove 22 is not too small, which is conducive to setting a larger adhesive 30.

[0080] In some embodiments, along the third direction Z, the minimum distance between the third edge 223 and the packaging area 26 is P3, satisfying: 5mm≤P3≤13mm, and the minimum distance between the fourth edge 224 and the packaging area 26 is P4, satisfying: 5mm≤P4≤13mm.

[0081] When P3≥5mm and P4≥5mm are satisfied, the third edge 223 and the fourth edge 224 of the groove 22 are not too close to the packaging area 26, which is conducive to reducing the risk of the adhesive 30 entering the packaging area 26 and affecting the sealing of the packaging bag 20. When P3≤13mm and P4≤13mm are satisfied, the area of ​​the groove 22 is not too small, which is conducive to setting a larger adhesive 30.

[0082] In some embodiments, the secondary battery 100 includes a wrapping adhesive (not shown), which is wrapped around both ends of the electrode assembly 10 in the length direction. The wrapping adhesive can reduce the damage to the electrode assembly 10 when it is subjected to external impact or compression, and improve the safety performance of the secondary battery 100.

[0083] When P1 ≥ 10 mm and P2 ≥ 10 mm are satisfied, it is beneficial for the adhesive 30 to avoid the winding adhesive, thereby reducing the risk of the adhesive 30 and the winding adhesive overlapping in the thickness direction of the electrode assembly 10 , and is beneficial for reducing the thickness of the electrode assembly 10 .

[0084] See also Figure 2 and Figure 8 In some embodiments, the packaging area 26 includes a first area 261, a second area 262, a third area 263 and a fourth area 264. The first area 261 and the second area 262 are arranged opposite to each other along the second direction Y, and the third area 263 and the fourth area 264 are arranged opposite to each other along the third direction Z. Figure 8As shown, when viewed along the first direction X, the first area 261 , the third area 263 , the second area 262 and the fourth area 264 are sequentially connected and arranged around the outer periphery of the groove 22 .

[0085] Along the second direction, the minimum distance P1 between the first edge 221 and the packaging area 26 refers to the minimum distance between the first edge 221 and the first area 261, and the minimum distance P2 between the second edge 222 and the packaging area 26 refers to the minimum distance between the second edge 222 and the second area 262. Along the third direction, the minimum distance P3 between the third edge 223 and the packaging area 26 refers to the minimum distance between the third edge 223 and the third area 263, and the minimum distance P4 between the fourth edge 224 and the packaging area 26 is the minimum distance between the fourth edge 224 and the fourth area 264.

[0086] In some embodiments, along the thickness direction of the electrode assembly 10 , the projection area of ​​the adhesive 30 is less than or equal to the area of ​​the groove 22 , and the projection of the adhesive 30 is located within the groove 22 .

[0087] When the projection area of ​​the adhesive 30 is smaller than the area of ​​the groove 22, the groove 22 can provide installation margin for the adhesive 30 in the length and width directions of the electrode assembly 10, thereby reducing the situation where the adhesive 30 cannot be accommodated in the groove 22 due to inaccurate positioning of the adhesive 30 and the groove 22. When the projection area of ​​the adhesive 30 is equal to the area of ​​the groove 22, the groove 22 can accommodate the adhesive 30 in the length and width directions of the electrode assembly 10, thereby reducing the situation where the adhesive 30 is attached outside the groove 22 and increases the overall thickness of the electrode assembly 10.

[0088] See also Figure 5 and Fig. 9 In some embodiments, the groove 22 includes a side wall 225 and a bottom wall 226 , and the adhesive 30 is bonded to the bottom wall 226 on the side facing away from the electrode assembly 10 , which is beneficial to increase the contact area between the adhesive 30 and the packaging bag 20 and improve the firmness of the bonding between the adhesive 30 and the packaging bag 20 .

[0089] See also Figure 2 In some embodiments, the packaging bag 20 includes a first portion 20a and a second portion 20b, and the first portion 20a and the second portion 20b are enclosed to form a chamber 21. The depth of the first portion 20a is greater than the depth of the second portion 20b, and the groove 22 is disposed in the first portion 20a.

[0090] Compared with the second portion 20b, the first portion 20a can cover more portions of the electrode assembly 10 in the thickness direction, thereby improving the installation stability of the electrode assembly 10 in the first portion 20a, so that the electrode assembly 10 is not easy to shake relative to the first portion 20a. The groove 22 is provided in the first portion 20a, and the adhesive 30 is located in the first portion 20a, so that the adhesive 30 is not easy to move relative to the packaging bag 20.

[0091] See also Fig.10 In some embodiments, the first pole piece 11, the diaphragm 13 and the second pole piece 12 are stacked and wound to form a wound structure.

[0092] See also Fig.10 In some embodiments, the electrode assembly 10 is a wound structure, the electrode assembly 10 includes a main body 10a and a tail portion 10b, the adhesive 30 adheres the tail portion 10b and the main body 10a, and the adhesive 30 is adhered between the tail portion 10b and the packaging bag 20.

[0093] The adhesive 30 of the tail portion 10b can not only fix the tail portion 10b so that the tail portion 10b is fixed to the main body 10a and is not prone to wrinkles; it can also fix the electrode assembly 10 to the packaging bag 20 so that the electrode assembly 10 is not prone to shaking relative to the packaging bag 20.

[0094] See also Fig.11 In some embodiments, the adhesive member 30 includes a first adhesive layer 31, a base material layer 32 and a second adhesive layer 33 which are stacked in sequence. The first adhesive layer 31 is bonded to the packaging bag 20, and the second adhesive layer 33 is bonded to the electrode assembly 10. The first adhesive layer 31 is a hot melt adhesive layer, and the second adhesive layer 33 is a pressure-sensitive adhesive layer.

[0095] The viscosity of the hot melt adhesive layer is activated after being subjected to high temperature and high pressure. This arrangement enables, when assembling the secondary battery 100, the adhesive 30 can be first bonded to the electrode assembly 10 through the pressure-sensitive adhesive layer, and then the electrode assembly 10 bonded with the adhesive 30 can be placed in the packaging bag 20, and finally the viscosity of the hot melt adhesive layer is activated by high temperature and high pressure, so that the hot melt adhesive layer is bonded to the packaging bag 20. In the process of placing the electrode assembly 10 into the packaging bag 20, the viscosity of the hot melt adhesive layer is not activated, so that the adhesive 30 and the packaging bag 20 are not easily bonded in the process of placing the electrode assembly 10 into the packaging bag 20, which facilitates the placement of the electrode assembly 10 into the packaging bag 20.

[0096] An embodiment of the present application further provides an electronic device 1000 , which includes the secondary battery 100 in any of the above embodiments.

[0097] The electronic device 1000 is provided with a groove 22 on the packaging bag 20 of the secondary battery 100, and at least a portion of the adhesive 30 is accommodated in the groove 22, so that the adhesive 30 can fix the electrode assembly 10 and the packaging bag 20, so that the electrode assembly 10 is not easy to shake in the cavity 21 of the packaging bag 20 during the drop test, which is beneficial to improving the pass rate of the drop test of the secondary battery 100 and increasing the service life of the electronic device 1000.

[0098] In some embodiments, the electronic device 1000 may 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.

[0099] In some embodiments, the electronic device 1000 further includes a device body 200, and the secondary battery 100 is installed in the device body 200. Since the electronic device 1000 adopts the technical solution of the secondary battery 100 in any of the above embodiments, it has at least the beneficial effects brought by the technical solution of any of the above embodiments of the secondary battery 100, which will not be described one by one here.

[0100] In order to verify the influence of the groove 22 and the adhesive member 30 on the performance of the secondary battery 100, the following experiment was conducted: 1. Drop test: Pre-treat the secondary battery 100 at 25°C, let it stand for 60 minutes at room temperature, and then test the voltage of the lithium-ion battery before the drop test; load the secondary battery 100 into a fixture, and use a drop device to drop freely from a position 1.5m above the ground (using a metal drop floor) in the following order: six faces of the secondary battery 100 and the right corner of the head, the right corner of the tail, the left corner of the head, and the left corner of the tail (angle: 45±15°), and repeat 6 rounds. After the drop, let it stand for 24 hours at room temperature, measure and record the voltage of the secondary battery 100, and check the appearance of the lithium-ion battery before and after the test and take pictures. The drop test pass judgment criteria: no smoke, no leakage, and voltage drop <50mV. 50 secondary batteries 100 were tested in each group of embodiments and comparative examples, and the number of batteries that passed the test was Y, and the test pass rate was Y / 50.

[0101] 2. Secondary battery thickness test method: The thickness of the secondary battery 100 was measured using a flat plate thickness gauge (PPG) under a force of 600 g. The thickness of 50 secondary batteries 100 was tested for each group of embodiments and comparative examples, and the average thickness of the secondary batteries 100 was taken as the thickness of the secondary battery 100 in each group of embodiments or comparative examples. The thickness gain in Table 1 refers to the thickness reduction of the secondary battery 100 in each embodiment compared with the secondary battery in comparative example 1.

[0102] The specific settings in each embodiment and comparative example in the experiment are described in detail below.

[0103] Embodiment and comparative example: (1) Preparation of positive electrode sheet: Active materials lithium cobalt oxide (LiCoO2), conductive carbon black (Super P), CNT (carbon nanotube), polyvinylidene fluoride (PVDF) are mixed in a weight ratio of 97.5:0.5:0.5:1.5, N-methylpyrrolidone (NMP) is added as a solvent, and a positive electrode active material with a solid content of 75wt% is prepared, and stirred evenly for use. Aluminum foil with a thickness of 10μm is used as a positive electrode collector. The above positive electrode active material is evenly coated on one side of the positive electrode collector using a slit coater, and then dried at 90°C to obtain a positive electrode sheet coated with a positive electrode active material on one side. Then the above coating steps are repeated on the other side of the positive electrode collector. Then the coated positive electrode sheet is cold pressed. Then the positive electrode ear 14 is welded to the part of the positive electrode collector that is not covered by the positive electrode active material layer.

[0104] (2) Preparation of negative electrode sheet: Active materials artificial graphite, conductive carbon black (Super P), styrene-butadiene rubber (SBR), 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 a weight percentage of 50wt% of negative electrode active material is prepared, and the mixture is stirred evenly for use. A copper foil with a thickness of 10μm is used as a negative electrode current collector. The above negative electrode active material is evenly coated on one side of the negative electrode current collector using a slit coater, and then dried at 110°C to obtain a negative electrode sheet coated with a negative electrode active material layer on one side. Then the above steps are repeated on the other side of the negative electrode current collector to obtain a negative electrode sheet coated with a negative electrode active material layer on both sides. Then the coated negative electrode sheet is cold pressed. Thereafter, the negative electrode ear 14 is welded to the portion of the negative electrode current collector that is not covered by the negative electrode active material layer.

[0105] (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 well to obtain an electrolyte with a lithium salt concentration of 1.15 mol / L.

[0106] (4) Preparation of the separator 13: A 7 μm thick polyethylene porous polymer film was used as the separator 13.

[0107] (5) Preparation of the electrode assembly 10: The positive electrode sheet, the separator, and the negative electrode sheet are stacked and wound along the thickness direction of the negative electrode sheet to obtain the electrode assembly 10.

[0108] (6) Preparation of adhesive member 30: The first adhesive layer 31 is a hot melt adhesive layer, the second adhesive layer 33 is a pressure sensitive adhesive layer, the hot melt adhesive layer, the base material layer 32 and the pressure sensitive adhesive layer are stacked to form the adhesive member 30, and the thickness of the adhesive member 30 is 25 μm.

[0109] In Comparative Example 1 and Examples 1 to 17, in the second direction Y, the adhesive member 30 has a length of 77 mm and a width of 25 mm.

[0110] (7) Preparation of packaging bag 20: A single piece of packaging bag 20 material is punched and formed to form a first portion 20a and a second portion 20b. The packaging bag 20 material includes a nylon layer, an aluminum metal layer and a PP layer. The total thickness H of the single piece of packaging bag 20 material is 总 The thickness H of the PP layer is 91 um, and 35 um is selected. The groove 22 is formed on the PP layer by laser cleaning, and the depth of the groove 22 is measured after cleaning to reach the target depth.

[0111] (8) Assembly of secondary battery 100: The adhesive 30 is bonded to the electrode assembly 10, and the punched packaging bag 20 is placed in the assembly fixture, with the first part 20a facing upward, and the electrode assembly 10 is placed in the first part 20a, with the adhesive 30 facing the groove 22, and external force is applied to press it. Then, the second part 20b is covered on the electrode assembly 10 with the pit surface facing downward, and the three edges of the first part 20a and the second part 20b are heat-sealed by hot pressing to form the second region 262, the third region 263 and the fourth region 264. The unsealed edge is the side where the negative electrode ear 14 and the positive electrode ear 14 extend out of the packaging bag 20. Then, the electrolyte is injected through the unsealed edge, and the first region 261 is formed by vacuum packaging. After standing, hot pressing, shaping and other processes, the secondary battery 100 is manufactured.

[0112] The secondary battery 100 in Comparative Example 1 is different from the secondary battery 100 in the embodiment in that the packaging bag 20 of the secondary battery 100 in Comparative Example 1 is not provided with the groove 22 .

[0113] The parameters and experimental results of various embodiments and comparative examples are shown in Table 1.

[0114] Table 1 Note: “ / ” means no value.

[0115] The above experiments show that, compared with Comparative Example 1, Embodiments 1 to 7 are advantageous in improving the thickness gain by providing a groove 22 on the packaging bag 20 and disposing the adhesive 30 in the groove 22 , thereby facilitating improving the volume energy density of the secondary battery 100 .

[0116] It can be seen from Examples 1 to 7 that the greater the depth H1 of the groove 22, the more obvious the thickness gain, and the more conducive to improving the volume energy density of the secondary battery 100. However, when H1>0.75H, the voltage drop will increase significantly, and the pass rate of the drop test of the secondary battery 100 will decrease. Therefore, when 0.5H≤H1≤0.75H is satisfied, the volume energy density of the secondary battery 100 can be improved without reducing the pass rate of the drop test of the secondary battery 100.

[0117] It can be seen from Example 5, and Example 8 to Example 11 that when P1>15mm, P2>15mm, the distance between the first edge 221 and the second edge 222 and the packaging area 26 is too large, and the area occupied by the groove 22 is small. When the adhesive 30 is pasted, it is easy for the adhesive 30 to affect the sealing effect of the packaging area 26, which can easily lead to failure of the drop test; when P1<10mm, P2<10mm, it is easy to affect the packaging effect and the drop pass rate will also be reduced.

[0118] When 10mm≤P1≤15mm and 10mm≤P2≤15mm are satisfied, it is not only helpful to reduce the risk of the adhesive 30 entering the packaging area 26 and affecting the sealing of the packaging bag 20, but also to allow more space on the packaging bag 20 for setting the groove 22, which is conducive to setting a larger adhesive 30 and improving the drop pass rate of the secondary battery 100.

[0119] From Example 5, and Examples 12 to 16, it can be seen that when P3>13mm, P4>13mm, the distance between the third edge 223 and the fourth edge 224 and the packaging area 26 is too large, and the area occupied by the groove 22 is small. When the adhesive 30 is pasted, it is easy for the adhesive 30 to enter the packaging area 26, affecting the sealing effect of the packaging area 26, which is easy to cause the drop test to fail. When P3<5mm, P4<5mm, it is easy to affect the packaging effect, thereby reducing the drop pass rate.

[0120] When 5mm≤P3≤13mm and 5mm≤P4≤13mm are satisfied, it is not only helpful to reduce the risk of the adhesive 30 entering the packaging area 26 and affecting the sealing of the packaging bag 20, but also the area of ​​the groove 22 is not easy to be too small, which is conducive to setting a larger adhesive 30 and improving the drop pass rate of the secondary battery 100.

[0121] From Examples 1-7 and 17, when 0.7H≤H1≤0.75H, the groove thickness is further limited, so that the energy density is higher while ensuring the drop pass rate.

[0122] Those skilled in the art should recognize that the above embodiments are only used to illustrate the present application and are not intended to be limiting of the present application. As long as they are within the spirit and scope of the present application, appropriate changes and modifications to the above embodiments are within the scope of the present application.

Claims

1. A secondary battery, characterized in that: include: A packaging bag, wherein the packaging bag is formed with a cavity, and an inner wall of the packaging bag facing the cavity is provided with a groove; an electrode assembly, wherein the electrode assembly is disposed in the chamber; An adhesive member, one side of the adhesive member is bonded to the electrode assembly, and the other side is bonded to the groove. At least a portion of the adhesive member is disposed in the groove, and along the thickness direction of the electrode assembly, the projection of the adhesive member is located in the groove.

2. The secondary battery according to claim 1, wherein: Along the thickness direction of the electrode assembly, the adhesive components are all disposed in the grooves.

3. The secondary battery according to claim 1, wherein: The packaging bag includes a first layer, a second layer and a third layer stacked in sequence, the first layer is located at the outermost layer of the packaging bag, and the second layer is a metal layer; along the thickness direction of the packaging bag, the thickness of the third layer is H, and the depth of the groove is H1, satisfying: 0.5H≤H1≤0.75H.

4. The secondary battery according to claim 3, characterized in that: 0.7H≤H1≤0.75H.

5. The secondary battery according to claim 3, characterized in that: The first layer is a nylon layer, and the third layer is a polypropylene layer.

6. The secondary battery according to claim 1, wherein: The electrode assembly includes a tab, which is arranged on one side of the length direction of the electrode assembly; the packaging bag has a packaging area around its edges, the groove has a first edge and a second edge that are arranged opposite to each other along the length direction of the electrode assembly, and a third edge and a fourth edge that are arranged opposite to each other along the width direction of the electrode assembly, and the first edge and the tab are located on the same side of the electrode assembly; Along the length direction of the electrode assembly, the minimum distance between the first edge and the packaging area is P1, satisfying: 10mm≤P1≤15mm, the minimum distance between the second edge and the packaging area is P2, satisfying: 10mm≤P2≤15mm; and / or, along the width direction of the electrode assembly, the minimum distance between the third edge and the packaging area is P3, satisfying: 5mm≤P3≤13mm, the minimum distance between the fourth edge and the packaging area is P4, satisfying: 5mm≤P4≤13mm.

7. The secondary battery according to claim 1, wherein: Along the thickness direction of the electrode assembly, the packaging bag includes a first part and a second part, the first part and the second part enclose the chamber; the depth of the first part is greater than the depth of the second part, and the groove is arranged in the first part.

8. The secondary battery according to claim 1, wherein: The electrode assembly is a wound structure, and includes a main body and a tail portion. The adhesive is bonded to the tail portion and the main body, and the adhesive is bonded between the tail portion and the packaging bag.

9. The secondary battery according to any one of claims 1 to 8, characterized in that: The adhesive component includes a first adhesive layer, a base material layer and a second adhesive layer which are stacked in sequence, the first adhesive layer is bonded to the packaging bag, the second adhesive layer is bonded to the electrode assembly, the first adhesive layer is a hot melt adhesive layer, and the second adhesive layer is a pressure sensitive adhesive layer.

10. The secondary battery according to any one of claims 1 to 8, characterized in that: Along the thickness direction of the electrode assembly, a projection area of ​​the adhesive is smaller than or equal to an area of ​​the groove.

11. The secondary battery according to any one of claims 1 to 8, characterized in that: Along the depth direction of the groove, the thickness of the adhesive is H2, satisfying: 10um≤H2≤25um.

12. The secondary battery according to claim 1, wherein: The groove includes a side wall and a bottom wall, and a side of the adhesive member facing away from the electrode assembly is bonded to the bottom wall.

13. An electronic device, characterized in that: The invention comprises the secondary battery according to any one of claims 1 to 12.

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