Secondary battery, method for manufacturing secondary battery, and

Abstract

The invention relates to the technical field of energy storage, and particularly discloses a secondary battery, a manufacturing method of the secondary battery and a power utilization device. The secondary battery comprises an electrode assembly, the electrode assembly comprises a first pole piece, a second pole piece, a diaphragm and a filling piece, the first pole piece comprises a first current collector and a first active material layer, the second pole piece comprises a second current collector and a second active material layer, and the diaphragm is arranged between the first active material layer and the second active material layer. The first active material layer is provided with a groove, the groove comprises a groove opening and a groove wall, and the other side, facing the groove opening, of the diaphragm corresponds to the second active material layer; the filling piece comprises a filling part, the filling part is located in the groove, and the filling part covers at least part of the groove wall. The filling piece can separate the lithium dendrites separated out of the groove from the diaphragm, so that the lithium dendrites in the groove are limited to grow towards the direction of the diaphragm, and the lithium dendrites are not prone to piercing the diaphragm.

Description

Technical Field

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

[0002] In the design of secondary batteries, the energy density can be improved by increasing the coating weight of the active material layer on the pole piece. However, after the weight of the active material layer coated on the pole piece increases, the electrolyte is not easy to infiltrate the pole piece, so it is necessary to drill holes in the active material layer to improve the infiltration effect of the electrolyte on the pole piece. Summary of the invention

[0003] In the grooves formed by punching the active material layer, the lithium ion transmission path is long and the local current density is large, which makes it easy to produce lithium dendrites. Moreover, the lithium dendrites in the grooves are not hindered by the diaphragm. The lithium dendrites grow freely and can easily pierce the diaphragm, causing safety hazards.

[0004] In view of this, it is necessary to provide a secondary battery, a method for manufacturing a secondary battery and an electrical device, which are conducive to reducing the risk of the diaphragm being pierced by lithium dendrites.

[0005] The embodiment of the first aspect of the present application provides a secondary battery, including an electrode assembly, the electrode assembly including a first pole piece, a second pole piece and a diaphragm, the first pole piece including a first current collector and a first active material layer, the first active material layer is arranged on at least one surface of the first current collector along the thickness direction of the first current collector; the second pole piece includes a second current collector and a second active material layer, the second active material layer is arranged on at least one surface of the second current collector along the thickness direction of the second current collector; the diaphragm is arranged between the first active material layer and the second active material layer. The first active material layer is provided with a groove, the groove includes a groove opening and a groove wall, along the thickness direction of the first pole piece, the groove faces the diaphragm, and the other side of the diaphragm facing the groove position corresponds to the second active material layer. The first pole piece also includes a filling piece, the filling piece includes a filling portion, the filling portion is located in the groove, and the filling portion covers at least part of the groove wall.

[0006] In the above embodiment, when lithium dendrites are precipitated in the groove, the filling member located in the groove can separate the lithium dendrites precipitated in the groove from the diaphragm, and restrict the lithium dendrites in the groove from growing toward the diaphragm, so that the lithium dendrites are not easy to pierce the diaphragm. When the lithium dendrites precipitated on the first active material layer come into contact with the filling member, the filling member can also apply pressure to the lithium dendrites, so that the lithium dendrites are not easy to produce sharp free growth ends, thereby reducing the risk of lithium dendrites piercing the diaphragm and improving the safety of secondary battery applications.

[0007] In one or more of the above embodiments, the material of the filling member includes at least one of a ceramic material and a resin material.

[0008] In the above embodiment, on the one hand, the ceramic material and the resin material have a supporting function and can inhibit the growth of lithium dendrites; on the other hand, the ceramic material and the resin material have large pores, and lithium ions can pass through the pores, reducing the impact on lithium ion transmission. The ceramic material and the resin material also have insulation properties, which can take into account both the electrolyte infiltration effect and the safety performance of the secondary battery.

[0009] In one or more of the above embodiments, the ceramic material is selected from at least one of aluminum oxide, boehmite, titanium oxide, magnesium oxide, calcium oxide, and zirconium oxide.

[0010] In one or more of the above embodiments, the resin material is selected from at least one of polyimide, polytetrafluoroethylene and polyvinyl butyral.

[0011] In one or more of the above embodiments, the material of the filling piece further includes a binder.

[0012] In the above embodiment, the binder can improve the viscosity between the filling member and the active material layer, which is beneficial for the filling member to solidify in the groove, and further beneficial for suppressing the growth of lithium dendrites in the groove.

[0013] In one or more of the above embodiments, the internal space volume of the groove is V1, the volume of the filling portion is V2, the thickness of the first active material layer where the groove is not set is h, and 0.6V1≤V2≤V1 is satisfied.

[0014] In the above embodiment, V2≥0.6V1 makes the filling part in the groove have a certain volume, so that the filling part has a certain inhibitory effect on the growth of lithium dendrites. V2≤V1 makes it difficult for the filling part to protrude from the groove, increase the thickness of the secondary battery, and thus reduce the energy density of the secondary battery; when V2=V1, the filling part can fill the groove and improve the flatness of the surface of the first active material layer; at the same time, the entire groove is filled with the filling part, and the filling part covers the entire groove wall, so that each position of the groove wall can be supported by the filling part, which has a better inhibitory effect on lithium dendrites than the groove that is not filled with the filling part.

[0015] In one or more of the above embodiments, 0.9V1≤V2≤V1.

[0016] In the above embodiment, V2≥0.9V1, so that the filling portion has a larger volume, so that the groove wall area covered by the filling portion is larger, and the inhibitory effect on the growth of lithium dendrites in the groove is more obvious.

[0017] In one or more of the above embodiments, all of the filling pieces are disposed in the groove.

[0018] In the above embodiment, no filler is provided at the position where the groove is not provided in the first active material layer, so that the thickness of the electrode sheet is not easily increased while suppressing the growth of lithium dendrites, thereby not easily reducing the energy density of the secondary battery.

[0019] In one or more of the above embodiments, the filling member further includes a coating portion, and the coating portion is disposed in a region of the first active material layer on a side facing the diaphragm where no groove is disposed.

[0020] In the above embodiment, the coating portion can protect the electrode, improve the mechanical strength of the first electrode, and is conducive to storing more electrolyte, which is more conducive to the transmission of lithium ions; and can play a certain inhibitory effect on the growth of lithium dendrites in the area of ​​the first active material layer facing the side of the diaphragm where no groove is set.

[0021] In one or more of the above embodiments, the coating part and the filling part are integrally provided.

[0022] In the above embodiment, the integrally arranged coating portion and filling portion can reduce the separation between the coating portion and the filling portion, thereby reducing the lithium precipitation in the gap between the coating portion and the filling portion, and further improving the effect of inhibiting the growth of lithium dendrites.

[0023] In one or more of the above embodiments, along the thickness direction of the first pole piece, the thickness of the coating portion is h1, satisfying 0.5um≤h1≤2um.

[0024] In the above embodiment, when h1≥0.5um, it can meet the requirements of improving the mechanical strength of the first electrode, enhancing the electrolyte storage of the first electrode and inhibiting the growth of lithium dendrites; when h1≤2um, it is not easy to make the battery cell too thick and reduce the energy density.

[0025] In one or more of the above embodiments, along the thickness direction of the first pole piece, the thickness of the first active material layer at the position where no groove is set is H1, and the depth of the groove is H2, satisfying: H1 / 4≤H2≤H1 / 2.

[0026] In the above embodiment, when H2≥H1 / 4, the groove has a certain depth, which is convenient for the electrolyte to infiltrate the first active material layer through the groove, thereby providing transmission power for lithium ions, which is beneficial for lithium ions to be embedded in the first active material layer and reduce lithium precipitation; H2≤H1 / 2, so that the first active material layer at the groove is not easy to be too small, thereby providing sufficient lithium embedding space for lithium ions and reducing lithium precipitation.

[0027] The second aspect of the present application also provides a method for manufacturing a secondary battery, which is used to manufacture the secondary battery in any of the above embodiments, comprising the following steps:

[0028] Filling: Setting a filling piece in the groove;

[0029] Stacking: stacking the diaphragm and the second electrode piece on the first electrode piece in sequence along the thickness direction of the first electrode piece, with the diaphragm being located between the first active material layer and the second electrode piece.

[0030] In the above embodiment, a filler is provided in the groove of the first active material layer so that the filler can block the extension growth of lithium dendrites in the groove, thereby inhibiting lithium precipitation in the groove, making the diaphragm less likely to be pierced by freely growing lithium dendrites, thereby improving the safety performance of the electrode assembly.

[0031] In one or more of the above embodiments, the filling step includes:

[0032] Coating: coating the filler slurry on the side of the first active material layer facing the diaphragm;

[0033] Leveling: The applied filler slurry flows into the groove.

[0034] In the above embodiment, the filling member slurry can flow into the multiple grooves of the first active material layer at the same time by coating first and then leveling, which is beneficial to improve the efficiency of arranging the filling members in the grooves.

[0035] In one or more of the above embodiments, the filling step further comprises:

[0036] Curing: Curing the filling slurry into a filling part.

[0037] The embodiment of the third aspect of the present application further provides an electrical device, comprising a secondary battery as in any of the above embodiments.

[0038] In the above embodiment, a filler is provided on the first active material layer of the secondary battery to inhibit the growth of lithium dendrites, reduce the risk of puncture of the diaphragm, and thereby increase the service life of the secondary battery and the service life of the electrical device. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 is a schematic diagram of a secondary battery in one embodiment of the present application.

[0040] Figure 2 yes Figure 1 An enlarged view of part II.

[0041] Figure 3 It is a partial cross-sectional view of the first pole piece in one embodiment of the present application.

[0042] Figure 4 It is a partial schematic diagram of the first active material layer of the first electrode in one embodiment of the present application.

[0043] Figure 5 It is a partial top view of the first pole piece in one embodiment of the present application.

[0044] Figure 6 It is a partial side view of the first pole piece in another embodiment of the present application.

[0045] Figure 7 It is a partial cross-sectional view of the first active material layer and the filling member in one embodiment of the present application.

[0046] Figure 8 It is a schematic diagram of an electrical device in one embodiment of the present application.

[0047] Main component symbols

[0048] Electrical equipment 1000

[0049] Secondary battery 100

[0050] Electrode assembly 10

[0051] The first pole piece 11

[0052] First current collector 111

[0053] First surface 111a

[0054] Second surface 111b

[0055] First active material layer 112

[0056] Groove 1121

[0057] Notch 1121a

[0058] Groove wall 1121b

[0059] Filler 113

[0060] Filling section 1131

[0061] Coating Department 1132

[0062] First tab 114

[0063] The second pole piece 12

[0064] Second current collector 121

[0065] The third surface 121a

[0066] Fourth side 121b

[0067] Second active material layer 122

[0068] Second pole ear 123

[0069] Diaphragm 13

[0070] First diaphragm 13a

[0071] Second diaphragm 13b

[0072] Housing 20

[0073] Device body 200

[0074] First direction X

[0075] Second direction Y

[0076] The following specific implementation methods will further illustrate the present application in conjunction with the above-mentioned drawings. DETAILED DESCRIPTION

[0077] 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.

[0078] 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.

[0079] In the description of the embodiments of the present application, the technical terms "first", "second", etc. are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features. In the description of the embodiments of the present application, the meaning of "multiple" is more than two, unless otherwise clearly and specifically defined.

[0080] In the design of secondary batteries, the energy density can be improved by increasing the coating weight of the active material layer on the pole piece. However, after the coating weight of the active material layer increases, the electrolyte is not easy to infiltrate the pole piece, so it is necessary to drill holes in the active material layer to improve the infiltration effect of the electrolyte on the pole piece.

[0081] In the grooves formed by punching the active material layer, the lithium ion transmission path is long and the local current density is large, which makes it easy to produce lithium dendrites. Moreover, the lithium dendrites in the grooves are not hindered by the diaphragm. The lithium dendrites grow freely and can easily pierce the diaphragm, causing safety hazards.

[0082] An embodiment of the present application provides a secondary battery, including an electrode assembly, the electrode assembly including a first pole piece, a second pole piece and a diaphragm, the first pole piece including a first current collector and a first active material layer, the first active material layer is arranged on at least one surface of the first current collector along the thickness direction of the first current collector; the second pole piece includes a second current collector and a second active material layer, the second active material layer is arranged on at least one surface of the second current collector along the thickness direction of the second current collector; the diaphragm is arranged between the first active material layer and the second active material layer. The first active material layer is provided with a groove, the groove includes a groove opening and a groove wall, along the thickness direction of the first pole piece, the groove faces the diaphragm, and the other side of the diaphragm facing the groove position corresponds to the second active material layer. The first pole piece also includes a filling piece, the filling piece includes a filling portion, the filling portion is located in the groove, and the filling portion covers at least part of the groove wall.

[0083] In the above embodiment, when lithium dendrites are precipitated in the groove, the filling member located in the groove can separate the lithium dendrites precipitated in the groove from the diaphragm, and restrict the lithium dendrites in the groove from growing toward the diaphragm, so that the lithium dendrites are not easy to pierce the diaphragm. When the lithium dendrites precipitated on the first active material layer come into contact with the filling member, the filling member can also apply pressure to the lithium dendrites, so that the lithium dendrites are not easy to produce sharp free growth ends, thereby reducing the risk of lithium dendrites piercing the diaphragm and improving the safety of secondary battery applications.

[0084] The following is a further description of the embodiments of the present application in conjunction with the accompanying drawings. In the absence of conflict, the following embodiments and features in the embodiments may be combined with each other.

[0085] like Figure 1 As shown, the first embodiment of the present application provides a secondary battery 100, including an electrode assembly 10 and a shell 20, wherein the electrode assembly 10 is accommodated in the shell 20. The electrode assembly 10 includes a first pole piece 11, a second pole piece 12 and a diaphragm 13, wherein the diaphragm 13 is disposed between the first pole piece 11 and the second pole piece 12, and the diaphragm 13 is used to isolate the first pole piece 11 and the second pole piece 12.

[0086] In some embodiments, the housing 20 is a flexible packaging bag, such as an aluminum-plastic film. In other 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.

[0087] 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.

[0088] In some embodiments, the electrolyte salt includes at least one of an organic lithium salt or an inorganic lithium salt.

[0089] 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).

[0090] In some embodiments, the polarities of the first pole piece 11 and the second pole piece 12 are different. For example, the first pole piece 11 is an anode pole piece, and the second pole piece 12 is a cathode pole piece.

[0091] See also Figure 1 In some embodiments, the first pole piece 11, the diaphragm 13 and the second pole piece 12 are stacked and wound to form a winding structure.

[0092] In some embodiments, the secondary battery 100 includes a plurality of first electrode sheets 11 , a plurality of separators 13 , and a plurality of second electrode sheets 12 , and any adjacent first electrode sheet 11 and any adjacent second electrode sheet 12 are separated by the separator 13 .

[0093] See also Figure 1 and Figure 2 In some embodiments, the first pole piece 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, and the second pole piece 12 includes a second current collector 121 and a second active material layer 122, the second active material layer 122 is disposed on at least one surface of the second current collector 121 along the thickness direction of the second current collector 121. The diaphragm 13 is disposed between the first active material layer 112 and the second active material layer 122. The thickness direction of the first current collector 111 and the thickness direction of the second current collector 121 are the first direction X.

[0094] See also Figure 2 and Figure 3 In some embodiments, along the thickness direction of the first pole piece 11, the first current collector 111 has a first surface 111a and a second surface 111b that are oppositely disposed. The thickness direction of the first pole piece 11 is consistent with the thickness direction of the first current collector 111, and the thickness direction of the first pole piece 11 is the first direction X. At least one of the first surface 111a and the second surface 111b is provided with a first active material layer 112, for example, both the first surface 111a and the second surface 111b are provided with a first active material layer 112.

[0095] See also Figure 2In some embodiments, along the thickness direction of the second pole piece 12, the second current collector 121 has a third surface 121a and a fourth surface 121b that are arranged opposite to each other, and the thickness direction of the second pole piece 12 is consistent with the thickness direction of the second current collector 121. At least one of the third surface 121a and the fourth surface 121b is provided with the second active material layer 122, for example, the third surface 121a and the fourth surface 121b are both provided with the second active material layer 122.

[0096] See also Figure 1 In some embodiments, for the electrode assembly 10 of the wound structure, the first pole sheet 11 further includes a first pole ear 114 , which is welded to the first current collector 111 ; the second pole sheet 12 further includes a second pole ear 123 , which is welded to the second current collector 121 .

[0097] In some embodiments, for the stacked electrode assembly 10 , the first pole sheet 11 further includes a first pole tab 114 , which is integrally arranged with the first current collector 111 ; the second pole sheet 12 further includes a second pole tab 123 , which is integrally arranged with the second current collector 121 .

[0098] In some embodiments, the first electrode tab 114 and the second electrode tab 123 are disposed on the same side or different sides of the electrode assembly 10 .

[0099] Taking the first pole piece 11 as an anode pole piece and the second pole piece 12 as a cathode pole piece as an example, the first current collector 111 and the second current collector 121 may be metal layers. The first current collector 111 may be a metal layer including at least one of copper, nickel, tantalum, titanium, etc., such as copper foil. The second current collector 121 may be a metal layer including at least one of aluminum, nickel, tantalum, titanium, etc., such as aluminum foil.

[0100] Taking the first pole piece 11 as an anode pole piece and the second pole piece 12 as a cathode pole piece as an example, the polarity of the first active material layer 112 is anode, and the first active material layer 112 includes an anode active material, and 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 cathode, and the second active material layer 122 includes a cathode active material, and 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.

[0101] See also Figures 2 to 4In some embodiments, the first active material layer 112 is provided with a groove 1121, and the groove 1121 includes a groove 1121a and a groove wall 1121b. Along the thickness direction of the first pole piece 11, the groove 1121a faces the diaphragm 13, and the other side of the diaphragm 13 facing the groove 1121a corresponds to the second active material layer 122. The first pole piece 11 also includes a filling member 113, and the filling member 113 includes a filling portion 1131. The filling portion 1131 is located in the groove 1121, and the filling portion 1131 covers at least part of the groove wall 1121b. It can be understood that the groove wall 1121b is a wall surface that encloses the internal space of the groove 1121, and the groove wall 1121b includes a side wall and a groove bottom, and the filling portion 1131 covers at least part of the side wall and the groove bottom.

[0102] In the design of related secondary batteries, the energy density can be improved by increasing the coating weight of the active material layer on the pole piece. However, after the weight of the coated active material layer increases, the thickness of the corresponding active material layer increases, the overall dynamic performance of the electrode assembly 10 decreases, and the electrolyte is not easy to infiltrate the pole piece, so it is necessary to use laser drilling technology to set grooves 1121 on the active material layer to improve the electrolyte infiltration effect in the thickness direction of the pole piece. After the groove 1121 is set on the active material layer, the coating weight of the pole piece can be increased, which improves the energy density compared to the original coating weight. However, after the groove 1121 is set, the coating weight of the active material at the position where the groove 1121 is set on the pole piece may be insufficient, resulting in a long lithium ion transmission path in the groove 1121, a large local current density, and easier deposition of dendritic lithium. The lithium dendrites grow in a free state and are easy to pierce the diaphragm 13.

[0103] The pores of the filling member 113 allow the electrolyte to pass through, so that the electrolyte can infiltrate the first active material layer 112 in the groove 1121. When lithium dendrites are precipitated in the groove 1121, the filling member 113 located in the groove 1121 can separate the lithium dendrites precipitated in the groove 1121 from the diaphragm 13, and restrict the lithium dendrites in the groove 1121 from growing toward the diaphragm 13, so that the lithium dendrites are not easy to pierce the diaphragm 13.

[0104] When the lithium dendrites precipitated on the first active material layer 112 come into contact with the filler 113 , the filler 113 can also exert pressure on the lithium dendrites to prevent them from generating free growth ends, thereby reducing the risk of lithium dendrites piercing the diaphragm 13 and improving the safety of the secondary battery 100 .

[0105] See also Figure 3 and Figure 5 In some embodiments, a plurality of grooves 1121 are disposed on the first active material layer 112, and the plurality of grooves 1121 are distributed in an array. For example, the plurality of grooves 1121 are distributed in a rectangular array.

[0106] See also Figure 3 and Figure 5 In some embodiments, the groove 1121 extends along the width direction of the first electrode sheet 11, and the width direction of the first electrode sheet 11 is the second direction Y shown in the figure. From the side view of the first active material layer 112, the groove 1121 is generally semicircular in outline; from the top view of the first active material layer 112, the groove 1121 is rectangular in outline, and multiple grooves 1121 are arranged in sequence along the length direction of the first active material layer 112.

[0107] Along the thickness direction of the first pole piece 11 , the thickness of the first active material layer 112 at a position where the groove 1121 is not provided is H1 , and the depth of the groove 1121 is H2 , satisfying: H1 / 4≤H2≤H1 / 2.

[0108] When H2≥H1 / 4 is satisfied, the groove 1121 has a certain depth, which is convenient for the electrolyte to infiltrate the first active material layer 112 through the groove 1121, thereby providing transmission power for lithium ions, which is beneficial for lithium ions to be embedded in the first active material layer 112 and reduce lithium precipitation; when H2≤H1 / 2 is satisfied, the first active material layer 112 at the groove 1121 is not easy to be too small, thereby providing sufficient lithium embedding space for lithium ions and reducing lithium precipitation.

[0109] See also Figure 5 In some embodiments, the distance between adjacent grooves 1121 is L, satisfying 0.8 mm ≤ L ≤ 2.0 mm. As an example, L may be, but is not limited to, 0.8 mm, 0.9 mm, 1.0 mm, 1.1 mm, 1.2 mm, 1.3 mm, 1.4 mm, 1.5 mm, 1.6 mm, 1.7 mm, 1.8 mm, 1.9 mm, or 2.0 mm, or other values ​​included in the above range.

[0110] See also Figure 3 , Figure 4 and Figure 6 In some embodiments, the internal volume of the groove 1121 is V1, and the volume of the filling portion 1131 is V2, which satisfies: 0.6V1≤V2≤V1. As an illustrative example, V2 can be, but is not limited to, 0.6V1, 0.65V1, 0.7V1, 0.75V1, 0.8V1, 0.85V1, 0.9V1, 0.95V1 or V1, or other values ​​within the range of V2.

[0111] V2≥0.6V1, so that the filling portion 1131 in the groove 1121 has a certain volume, so that the filling portion 1131 has a certain inhibitory effect on the growth of lithium dendrites. V2≤V1, so that the filling portion 1131 is not easy to protrude out of the groove 1121, and it is not easy to increase the thickness of the secondary battery 100, so it is not easy to reduce the energy density of the secondary battery 100.

[0112] In some embodiments, 0.9V1≤V2≤V1. V2≥0.9V1, so that the filling portion 1131 has a larger volume, so that the area of ​​the groove wall 1121b covered by the filling portion 1131 is larger, and the filling portion 1131 has a more obvious inhibitory effect on the growth of lithium dendrites.

[0113] See also Figure 3 In some embodiments, V2=V1, and the filling part 1131 covers the entire groove wall 1121b, so that the filling part 1131 at the position of the groove 1121 can fill the groove 1121 and improve the flatness of the surface of the first active material layer 112. The entire groove 1121 is filled with the filling member 113, and the filling part 1131 covers the entire groove wall 1121b, so that each position of the groove wall 1121b can be supported by the filling part 1131, and compared with the groove 1121 that is not filled with the filling part 1131, the inhibition effect on lithium dendrites is better.

[0114] It should be noted that, during the manufacturing process, when the filler 113 is applied to the groove 1121 in the form of a filler slurry, the groove 1121 is gradually filled by the fluidity of the slurry. For a single groove 1121, when the volume of the applied slurry is smaller than the volume of the groove 1121, the slurry first gradually flows along the side wall of the groove 1121, and when it flows to the bottom of the groove 1121, it gradually fills the entire groove 1121. Figure 3 As shown, the filling portion 1131 fills the entire groove 1121; Figure 6 As shown, the filling portion 1131 does not fill the entire groove 1121. It can be understood that, relative to the state where the filling portion 1131 does not fill the entire groove 1121, when the filling portion 1131 fills the entire groove 1121, the possibility of forming a gap between the filling portion 1131 and the groove wall 1121b of the groove 1121 is smaller, which has a better effect of inhibiting lithium precipitation.

[0115] See also Figure 3 In some embodiments, the filler 113 is entirely disposed in the groove 1121. The filler 113 is not disposed at the position of the first active material layer 112 where the groove 1121 is not disposed, so that the thickness of the first pole piece 11 is not easily increased while suppressing the growth of lithium dendrites, thereby not easily reducing the energy density of the secondary battery 100.

[0116] See also Figure 7 In some embodiments, the filling member 113 further includes a coating portion 1132 , and the coating portion 1132 is disposed in a region of the first active material layer 112 facing the diaphragm 13 where the groove 1121 is not disposed.

[0117] The coating portion 1132 can protect the first electrode plate 11, improve the mechanical strength of the first electrode plate 11, and be conducive to storing more electrolyte, which is more conducive to the transmission of lithium ions; and can play a certain inhibitory effect on the growth of lithium dendrites in the area of ​​the first active material layer 112 facing the side of the diaphragm 13 where the groove 1121 is not set.

[0118] In some embodiments, the coating portion 1132 is integrally provided with the filling portion 1131. The coating portion 1132 and the filling portion 1131 that are integrally provided can reduce the separation between the coating portion 1132 and the filling portion 1131, thereby reducing the lithium precipitation in the gap between the coating portion 1132 and the filling portion 1131, and further improving the effect of inhibiting the growth of lithium dendrites.

[0119] See also Figure 7 In some embodiments, along the thickness direction of the first pole piece 11, the thickness of the coating portion 1132 is h1, which satisfies 0.5um≤h1≤2um. When h1≥0.5um, it can meet the requirements of improving the mechanical strength of the first pole piece 11, improving the electrolyte storage of the first pole piece 11, and inhibiting the growth of lithium dendrites; when h1≤2um, it is not easy to make the battery cell too thick and reduce the energy density.

[0120] As an illustrative example, h1 can be, but is not limited to, 0.5um, 0.6um, 0.7um, 0.8um, 0.9um, 1.0um, 1.1um, 1.2um, 1.3um, 1.4um, 1.5um, 1.6um, 1.7um, 1.8um, 1.9um or 2.0um, or other values ​​other than the above examples and satisfying the range of h1.

[0121] In some embodiments, the material of the filler 113 includes at least one of a ceramic material and a resin material.

[0122] On the one hand, ceramic materials and resin materials have a rigid support function. When lithium dendrites grow and extend to contact with ceramic materials or resin materials, the ceramic materials or resin materials block the growth of lithium dendrites, thereby inhibiting the continued growth of lithium dendrites. On the other hand, ceramic materials and resin materials have large pores, and lithium ions can pass through the pores, reducing the impact on lithium ion transmission. Ceramic materials and resin materials also have insulation properties, which can take into account both the electrolyte infiltration effect and the safety performance of secondary batteries.

[0123] In some embodiments, the ceramic material is selected from at least one of alumina, boehmite, titanium oxide, magnesium oxide, calcium oxide, and zirconium oxide.

[0124] In some embodiments, the resin material is selected from at least one of polyimide (PI), polytetrafluoroethylene (PTFE), and polyvinyl butyral (PVB).

[0125] In some embodiments, the material of the filler 113 includes a ceramic material, a binder, a solvent, and an additive. The ceramic material includes ceramic particles, which have a rigid support function and have excellent thermal stability and dimensional integrity, which is conducive to maintaining the support function in a high temperature environment while ensuring the lithium ion transmission function of the electrolyte. The binder can increase the viscosity between the filler 113 and the first active material layer 112, which is conducive to the solidification of the filling part 1131 in the groove 1121, and the filling part 1131 is not easy to fall off from the groove 1121, which is more conducive to suppressing the growth of lithium dendrites in the groove 1121.

[0126] As an illustrative example, the binder is selected from at least one of polyvinyl alcohol (PVA), carboxymethyl cellulose (CMC) (aqueous) and polyvinylidene fluoride (PVDF), wherein polyvinylidene fluoride can increase the adhesion between the coating portion 1132 on the surface of the first pole piece 11 and the diaphragm 13, thereby improving the conductivity; the solvent can be an aqueous solvent or an oily solvent, the aqueous solvent includes water, ethanol, glycerol and other polar organic solvents, and the oily solvent includes acetone, N-methylpyrrolidone (NMP) and other non-polar solvents.

[0127] See also Figure 1 and Figure 2 In some embodiments, two diaphragms 13 are provided, and the two diaphragms 13 are respectively a first diaphragm 13a and a second diaphragm 13b. The first diaphragm 13a, the first pole piece 11, the second diaphragm 13b and the second pole piece 12 are sequentially stacked to form a winding structure.

[0128] In some embodiments, the diaphragm 13 includes a base film, which is an insulating film material such as a polyethylene film, a polypropylene film, a polyester film, or a polyimide film.

[0129] The embodiment of the present application also provides a method for manufacturing a secondary battery 100, comprising the following steps:

[0130] Filling: a filling member 113 is arranged in the groove 1121;

[0131] Stacking: The diaphragm 13 and the second electrode sheet 12 are sequentially stacked on the first electrode sheet 11 along the thickness direction of the first electrode sheet 11 , and the diaphragm 13 is located between the first active material layer 112 and the second electrode sheet 12 .

[0132] By setting a filler 113 in the groove 1121 of the first active material layer 112, the filler 113 can block the extension growth of lithium dendrites in the groove 1121, thereby inhibiting lithium precipitation in the groove 1121, making it difficult for the diaphragm 13 to be pierced by freely growing lithium dendrites, thereby improving the safety performance of the electrode assembly 10.

[0133] In some embodiments, the filling step includes:

[0134] Coating: coating the filler slurry on the side of the first active material layer 112 facing the diaphragm 13;

[0135] Leveling: The applied filling slurry flows into the groove 1121 .

[0136] By coating first and then leveling, the filling slurry can flow into the multiple grooves 1121 of the first active material layer 112 at the same time, which is beneficial to improving the efficiency of arranging the filling members 113 in the grooves 1121 .

[0137] In some embodiments, the method of coating the filler slurry can be a narrow slit extrusion coating method, a spray coating method, or a gravure coating method. The narrow slit extrusion coating method is a process in which the filler slurry is extruded from an extrusion nozzle and coated onto the first active material layer 112 under a certain pressure, and the coating thickness is controlled by the extrusion nozzle slit width and the metering pump. Compared with the spray coating method and the gravure coating method, the narrow slit extrusion coating method has uniform coating, is easy to control the coating amount, is not easy to coat too thickly, and has a high coating speed.

[0138] In some embodiments, the first pole piece 11 is vibrated to make the filler slurry flow into the groove 1121 to accelerate the flow speed of the filler slurry, improve the molding efficiency of the filler 113 , and improve the flatness of the filler slurry in the groove 1121 .

[0139] In some embodiments, the applied filling slurry all flows into the groove 1121 to form a filling portion 1131 .

[0140] In other embodiments, a portion of the applied filler slurry flows into the groove 1121 to form a filling portion 1131, and another portion is located in an area of ​​the first active material layer 112 where the groove 1121 is not provided to form a coating portion 1132. The thickness of the coating portion 1132 is adjusted by setting the weight of the filler slurry applied per unit area.

[0141] In some embodiments, the filler slurry is a slurry of a ceramic material or a slurry of a resin material.

[0142] In some embodiments, the filling step further comprises:

[0143] Curing: Curing the filling piece slurry into the filling piece 113 .

[0144] As an illustrative example, the curing method may be thermal curing, for example, the first pole piece 11 filled with the filling member slurry is placed in a vacuum oven for drying to improve the curing and molding efficiency of the filling member 113 .

[0145] In some embodiments, the stacking step includes: stacking a plurality of second pole pieces 12 , a plurality of diaphragms 13 and a plurality of first pole pieces 11 along the thickness direction of the first pole piece 11 , and disposing a diaphragm 13 between each first pole piece 11 and the second pole piece 12 .

[0146] See also Figure 8 The embodiments of the present application further provide an electric device 1000, which includes the secondary battery 100 in any of the above embodiments.

[0147] By disposing the filler 113 on the first active material layer 112 of the secondary battery 100 , the generation of lithium dendrites is suppressed, thereby increasing the service life of the secondary battery 100 and the service life of the electric device 1000 .

[0148] In some embodiments, the electrical device 1000 may be a mobile phone, a laptop computer, a tablet computer, a drone, an electric 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.

[0149] See also Figure 8 In some embodiments, the power-consuming device 1000 further includes a device body 200, and the secondary battery 100 is installed in the device body 200. Since the power-consuming 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.

[0150] In order to verify the influence of the filler 113 on the performance of the secondary battery 100, the inventors conducted the following experiments:

[0151] The experiment includes a group of comparative examples and 16 groups of exemplary embodiments. The anode electrode plate of the secondary battery 100 used in the comparative examples is not provided with a filling portion 1131, and the anode electrode plate of the secondary battery 100 used in the exemplary embodiments is provided with a filling portion 1131. The settings of the coating portion 1132 in each exemplary embodiment are shown in Table 1 below. The secondary batteries 100 in different groups of exemplary embodiments differ only in the parameters listed in Table 1 below, and are the same in other aspects.

[0152] The specific implementation of the secondary battery 100 in the embodiment and the comparative example is described below.

[0153] The assembly process of the secondary battery 100 in the comparative example is as follows:

[0154] 1. Preparation of cathode electrode:

[0155] The cathode active material is lithium cobalt oxide, the cathode conductive agent is acetylene black, and the cathode binder is polyvinylidene fluoride (PVDF, with a weight average molecular weight of 5×105 ) are mixed in a mass ratio of 94:3:3, N-methylpyrrolidone (NMP) is added as a solvent, and the cathode slurry is stirred under the action of a vacuum mixer until the solid content is 75wt% and the system is uniform. An aluminum foil with a thickness of 8μm is selected as the cathode current collector, and a foam glue is pasted at a preset position on one surface of the cathode current collector aluminum foil along its thickness direction. The cathode slurry is evenly coated on one surface of the cathode current collector aluminum foil along its thickness direction, and dried at 110°C to obtain a cathode pole piece with a single-sided cathode active material layer (thickness 80μm). Afterwards, the above steps are repeated on the other surface of the aluminum foil along its thickness direction to obtain a cathode pole piece with a double-sided cathode active material layer. Then the previously pasted foam glue is torn off to produce an empty aluminum foil area for welding the cathode pole ear.

[0156] 2. Preparation of anode electrode

[0157] The anode active material graphite powder, silicon powder, conductive carbon black (Super P), and binder styrene-butadiene rubber (SBR) are mixed in a weight ratio of 67.5:30:1:1.5, and then deionized water is added as a solvent to prepare an anode slurry with a solid content of 50wt%, and stirred evenly. A copper foil with a thickness of 5μm is selected as the anode current collector. The anode slurry is evenly coated on one surface of the anode current collector copper foil along its thickness direction, and dried at 90°C to obtain a single-sided anode pole piece. After the above steps are completed, the single-sided coating of the anode pole piece has been completed. After that, the above steps are repeated on the other surface of the anode pole piece along its thickness direction to obtain an anode pole piece with a double-sided coating of the anode active material layer. After that, a groove 1121 with a width of 85um and a depth of 10um is etched on the double-sided anode active material layer by laser, and the distance between adjacent grooves 1121 is L of 1.3mm; then a laser is used to etch an empty copper foil area for welding the anode pole ear at a preset position of the anode pole piece.

[0158] 3. Preparation of Diaphragm 13

[0159] A polyethylene (PE) film with a thickness of 8 μm was used as the separator 13 .

[0160] 4. Preparation of Electrolyte

[0161] In a dry argon atmosphere, ethylene carbonate, ethyl methyl carbonate and diethyl carbonate were mixed in a mass ratio of 30:50:20 to obtain an organic solution, and then lithium hexafluorophosphate was added to the organic solvent to dissolve and mix evenly to obtain an electrolyte with a lithium salt concentration of 1.15 mol / L.

[0162] 5. Preparation of Secondary Battery 100

[0163] Ultrasonic welding is used to weld the Al pole ear on the empty aluminum foil area preset for welding the cathode pole ear to obtain a cathode pole piece welded with the cathode pole ear; ultrasonic welding is used to weld the Ni pole ear on the empty copper foil area preset for welding the anode pole ear to obtain an anode pole piece welded with the anode pole ear. The above-prepared diaphragm 13, the cathode pole piece welded with the cathode pole ear, the diaphragm 13, and the anode pole piece welded with the anode pole ear are stacked in sequence and wound to obtain the electrode assembly 10. The electrode assembly 10 is placed in the aluminum-plastic film of the packaging bag, and the above-mentioned cathode pole ear and anode pole ear are both extended from the top seal edge of the packaging bag. After dehydration at 80°C, the electrolyte is injected and packaged.

[0164] The secondary battery 100 used in Comparative Example 1 and Examples 1 to 16 has a length of 78.35 mm, a width of 68.62 mm, and a thickness of 5.15 mm. The width of the anode electrode sheet used is 73.95 mm, and the length direction of the secondary battery 100 is consistent with the width direction of the anode electrode sheet and the cathode electrode sheet. The length of the groove 1121 etched on the anode electrode sheet is 73.95 mm, and the length direction of the groove 1121 is consistent with the width direction of the anode electrode sheet. The size of the packaging bag in the length direction of the secondary battery 100 is 4.4 mm.

[0165] The anode electrode sheets used in Examples 1 to 16, in addition to the above steps, also include the filling step in the manufacturing method of the above-mentioned secondary battery 100, and the filling slurry is an aluminum oxide material, wherein Examples 1 to 3 and Examples 12 to 16 only form the filling portion 1131 through the filling step, and Examples 4 to 11 form the filling portion 1131 and the coating portion 1132 through the filling step. For details, please refer to the previous text and will not be repeated here.

[0166] After the secondary batteries 100 in Comparative Example 1 and Examples 1-16 were prepared, the following tests were performed on the secondary batteries 100 in the group.

[0167] The test method is:

[0168] (1) The secondary battery 100 is subjected to a cycle test according to the following process: the secondary battery 100 is charged to a limit voltage of 4.26V at a maximum constant current (CC) of 2.8C, the secondary battery 100 is charged to a limit voltage of 4.3V at a maximum constant current (CC) of 2.5C, the secondary battery 100 is charged to a limit voltage of 4.45V at a maximum constant current (CC) of 2.0C, and then charged at a constant voltage condition (CV) of 4.45V until the current decreases to 1.2C, the secondary battery 100 is charged to a limit voltage of 4.5V at a maximum constant current (CC) of 1.2C, and then charged at a constant voltage condition (CV) of 4.5V until the current decreases to 1.0C, the secondary battery 100 is charged to a limit voltage of 4.515V at a maximum constant current (CC) of 1.0C, and then charged at a constant voltage condition (CV) of 4.515V until the current decreases to 0.025C.

[0169] The secondary battery 100 is step-charged, left for 5 minutes, and then discharged at 0.7C to 3.0V and left for 5 minutes. This is one cycle. At 25°C, after 700 cycles, the secondary battery 100 is discharged at 0.7C to 3.0V, and the secondary battery 100 is disassembled. A rectangular anode electrode with a laser-engraved groove 1121 with a width of 85um and a length of 1cm is taken as the sample 1 to be tested. The signal peak of the metallic lithium on the sample 1 to be tested with a fully charged anode electrode, that is, the DSC peak intensity in the groove, is detected by DSC (differential scanning calorimetry), and the amount of lithium precipitation can be calculated by the signal peak intensity. Under full discharge conditions, the metallic lithium in the anode electrode is irreversible lithium.

[0170] (2) Testing method of lithium deposition area of ​​coating part: discharge the secondary battery 100 to 3V at 0.2C, disassemble the secondary battery 100, take a rectangular electrode with the same lithium deposition position of 1.3mm width and 1cm length as the test sample 2, use DSC (differential scanning calorimetry) to detect the signal peak of metal lithium on the test sample 2 with full anode electrode, that is, the DSC peak intensity of the coating part, and calculate the amount of lithium deposition by the signal peak intensity. Under the full discharge condition, the metal lithium in the anode electrode is irreversible lithium.

[0171] (3) Volume energy density test method: Place the secondary battery 100 in a 25°C thermostat for 30 minutes to allow the secondary battery 100 to reach a constant temperature. Charge the secondary battery 100 that has reached a constant temperature at a constant current of 0.2C until the voltage reaches the full charge voltage, then charge at the full charge voltage at a constant voltage until the current reaches 0.025C, and discharge at 0.2C until the voltage reaches 3.0V, and record the discharge energy.

[0172] Volume energy density=discharge capacity×platform voltage / (length of secondary battery 100×width of secondary battery 100×thickness of secondary battery 100). The capacity is 6500mAh and the platform voltage is 3.82V.

[0173] The locations of the samples to be tested in Comparative Example 1 and Examples 1 to 16 are the same locations of different secondary batteries 100 .

[0174] (4) Method for measuring the volume V1 of a single groove 1121: Use an optical profilometer to measure the volume of the sample 1 to be tested.

[0175] Sample preparation: First, make sure the sample surface is clean and free of dust, grease and other impurities.

[0176] Instrument calibration: Before measurement, the optical profiler needs to be calibrated to ensure the accuracy and repeatability of the measurement. Calibration usually includes zero point calibration, system calibration and standard sample calibration.

[0177] Set parameters: Set measurement parameters.

[0178] Sample positioning: Place the sample on the measuring table of the instrument and use a microscope or camera to position it to ensure the measurement area is accurate.

[0179] Data collection: Start the measurement program, and the instrument will automatically scan the sample surface and collect surface morphology data. In white light interferometry, the instrument will record the interference fringes when light of different wavelengths is reflected on the sample surface; in confocal microscopy, the instrument will obtain depth information of the sample surface by scanning point by point using the confocal principle.

[0180] Data processing: After the measurement is completed, the collected data is processed using the matching software to generate a three-dimensional image or a two-dimensional contour map of the sample surface. The volume V1 of the groove 1121 is calculated by multiplying the depth integral in the width direction by the length of the groove 1121 through software analysis.

[0181] (5) Sampling method of samples to be tested:

[0182] Sample preparation: First, the sample is mounted on a microscope slide. The sample is fixed with liquid nitrogen to keep its structure stable.

[0183] Positioning: Place the slide under the microscope of the laser micro-cutting system, observe the sample through a high-power microscope, and determine the area to be cut. The system is equipped with a high-resolution camera for precise positioning.

[0184] Set parameters: According to the sample cutting requirements, set the laser power, frequency, scanning speed and other parameters. These parameters need to be adjusted according to the sample thickness, hardness and required cutting accuracy.

[0185] Cutting: Start the laser micro-cutting system, and the laser beam will accurately cut the sample along the preset path. Laser cutting can achieve micron-level accuracy.

[0186] Collecting samples: After cutting, the sample fragments fall into a collection container pre-placed below the cutting area. The collection container is usually a microplate or a special collection membrane to ensure that the cut sample is not lost.

[0187] The sampling method of the sample to be tested is applicable to the sampling of the sample 1 to be tested in (1), the sample 2 to be tested in (2), and the sampling when measuring the volume V1 of a single groove 1121 in (4).

[0188] After the experiment, the experimental data were sorted out to obtain the following Table 1:

[0189] Table 1

[0190]

[0191]

[0192] Note: “ / ” means there is no experimental data for this item.

[0193] The measurement method of the volume of a single groove in Table 1 is as described in (4) above. The relationship between the volume of a single groove and the volume of the groove of the sample 1 to be tested is: the volume of a single groove V1 = the volume of the groove of the sample 1 to be tested × the length of the single groove / 1 cm.

[0194] The "volume energy density" in Examples 4 to 11 is the volume energy density calculated when 10 layers of coating portions 1132 are added compared to Example 3. Each circle of the wound anode electrode sheet includes two folds, and one layer of coating portion 1132 refers to the coating portion 1132 on one layer of anode active material layer on one of the folded anode electrode sheets.

[0195] By comparing the comparative example with any group of Examples 1 to 16, it can be seen that the degree of lithium deposition in the groove 1121 without the filling portion 1131 is higher than the degree of lithium deposition in the groove 1121 with the filling portion 1131.

[0196] V2 in Examples 2 to 15 satisfies: 0.6V1≤V2≤V1. It can be seen from Examples 2 to 15 that under this condition, as V2 increases, that is, as the filling portion 1131 in the groove 1121 increases, the DSC peak intensity in the groove gradually decreases, and the lithium precipitation situation gradually improves. Compared with Example 1, it can be seen that when V2 is too small, the lithium precipitation is not well suppressed and is not enough to meet the required lithium precipitation effect; compared with Example 16, it can be seen that when V2>V1, that is, when the filling portion 1131 protrudes from the groove 1121, although the degree of lithium precipitation can be improved, it will cause the thickness of the battery cell to increase, thereby reducing the energy density of the secondary battery 100.

[0197] h1 in Examples 5 to 10 satisfies: 0.5um≤h1≤2um. It can be seen from Examples 5 to 10 that under this condition, as the thickness h1 of the coating portion 1132 increases, the degree of lithium plating in the area where the groove 1121 is not provided on the anode active material layer improves, but the volume energy density of the secondary battery 100 increases. Compared with the case where the coating portion 1132 is not provided in Example 4, the provision of the coating portion 1132 is more conducive to reducing lithium plating; compared with Example 11, it can be seen that when h1 is greater than 2um, the volume energy density of the secondary battery 100 is lower, which has a greater impact on the storage capacity of the secondary battery 100. It can be seen that when 1.5um≤h1≤2um is satisfied, it is possible to reduce lithium plating without causing a significant impact on the volume energy density of the secondary battery 100.

[0198] 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, comprising an electrode assembly, characterized in that: The electrode assembly includes a first pole piece, a second pole piece and a diaphragm, the first pole piece includes a first current collector and a first active material layer, the first active material layer is arranged on at least one surface of the first current collector along the thickness direction of the first current collector; the second pole piece includes a second current collector and a second active material layer, the second active material layer is arranged on at least one surface of the second current collector along the thickness direction of the second current collector; the diaphragm is arranged between the first active material layer and the second active material layer; the first active material layer is provided with a groove, the groove includes a groove opening and a groove wall, along the thickness direction of the first pole piece, the groove faces the diaphragm, and the other side of the diaphragm facing the groove position corresponds to the second active material layer; the first pole piece also includes a filling piece, the filling piece includes a filling portion, the filling portion is located in the groove, and the filling portion covers at least part of the groove wall.

2. The secondary battery according to claim 1, wherein: The material of the filler includes at least one of a ceramic material and a resin material.

3. The secondary battery according to claim 2, characterized in that: The ceramic material is selected from at least one of aluminum oxide, boehmite, titanium oxide, magnesium oxide, calcium oxide and zirconium oxide.

4. The secondary battery according to claim 2, characterized in that: The resin material is selected from at least one of polyimide, polytetrafluoroethylene and polyvinyl butyral.

5. The secondary battery according to claim 2, characterized in that: The material of the filling piece also includes a binder.

6. The secondary battery according to claim 1, wherein: The internal space volume of the groove is V1, and the volume of the filling portion is V2, satisfying: 0.6V1≤V2≤V1.

7. The secondary battery according to claim 6, characterized in that: 0.9V1≤V2≤V1.

8. The secondary battery according to any one of claims 1 to 7, characterized in that: The filling pieces are all arranged in the grooves.

9. The secondary battery according to any one of claims 1 to 7, characterized in that: The filling member further includes a coating portion, and the coating portion is disposed in a region of the first active material layer on a side facing the separator where the groove is not disposed.

10. The secondary battery according to claim 9, characterized in that The coating part is integrally provided with the filling part.

11. The secondary battery according to claim 9, wherein Along the thickness direction of the first pole piece, the thickness of the coating portion is h1, satisfying 0.5um≤h1≤2um.

12. The secondary battery according to claim 1, wherein: Along the thickness direction of the first pole piece, the thickness of the first active material layer at the position where the groove is not provided is H1, and the depth of the groove is H2, satisfying: H1 / 4≤H2≤H1 / 2.

13. The secondary battery according to claim 1, wherein: The first pole piece is an anode pole piece.

14. A method for manufacturing a secondary battery, for manufacturing the secondary battery according to any one of claims 1 to 13, characterized in that: The following steps are involved: Filling: arranging the filling member in the groove; Stacking: stacking the diaphragm and the second pole piece on the first pole piece in sequence along the thickness direction of the first pole piece, with the diaphragm being located between the first active material layer and the second pole piece.

15. The method for manufacturing a secondary battery according to claim 14, wherein: The filling step comprises: Coating: coating the filler slurry on the side of the first active material layer facing the diaphragm; Leveling: The filler slurry after coating flows into the groove.

16. The method for manufacturing a secondary battery according to claim 15, wherein: The filling step further comprises: Curing: Curing the filler slurry into the filler.

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

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