Multi-pole tab, electrode assembly, secondary battery, and electric device

Abstract

A compound pole piece (04), an electrode assembly (52), a secondary battery (5) and a power utilization device. The compound pole piece (04) comprises two single pole pieces, each single pole piece comprising a current collector (10) having a main body (11) and a protruding portion (12) protruding relative to the main body (11) in the extension direction of the current collector (10), and the protruding portions (12) of the two current collectors (10) are fixedly connected; an active material layer (20) is arranged on one surface of the main body (11), and the active material layers (20) of the two single pole pieces are arranged opposite to each other. By fixedly connecting the protruding portions (12) of the two current collectors (10), the relative sliding of the pole pieces during assembly is effectively alleviated; the main body (11) and the protruding portion (12) are independent of each other, and the fixation of the protruding portion (12) does not affect the arrangement of the active material layer (20) on the surface of the main body (11), thereby avoiding the problem that the safety size reserved for the negative electrode is insufficient due to the relative sliding of the pole pieces, and improving the safety of the battery.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of batteries, in particular to a compound tab, an electrode assembly, a secondary battery and an electric device. BACKGROUND

[0002] Lithium ion batteries have become the main power source for consumer electronics and electric vehicles due to their many advantages. With the increasing demand of people, lithium ion batteries gradually develop towards fast charging, long life, high energy density, and high safety.

[0003] Currently, lithium ion battery cells mainly have two structures of winding and stacking. The winding type cell is to make the positive and negative electrode sheets into continuous long sheet type, and the middle is separated by a diaphragm. The battery cell is made by winding method. The battery made by this method will cause stress concentration at the bending place of the electrode sheet, which will cause the deformation of the electrode sheet and affect the performance of the battery. The stacked type cell is to cut the prepared positive and negative electrode rolls into the required size of electrode sheets, and then stack the cut positive electrode sheets, diaphragm and negative electrode sheets in a certain order to form a cell. The stacked type battery has a tab lead-out in each layer, small internal resistance, fast electron transmission rate and good heat dissipation performance, which is suitable for preparing large capacity lithium ion batteries. However, during the stacking process, there is no extrusion force between the positive electrode sheet and the diaphragm, and between the negative electrode sheet and the diaphragm. Under the action of gravity or vibration, the electrode sheet is easy to slide, the electrode sheet and the diaphragm are misaligned, the positive electrode sheet and the negative electrode sheet are misaligned, the negative electrode sheet cannot cover the positive electrode sheet, and thus the capacity of part of the electrode sheet cannot be fully utilized, or the positive electrode sheet and the negative electrode sheet are in contact to cause short circuit and thus safety problems. In order to ensure that the electrode sheet and the diaphragm are misaligned, a relatively complex tooling is usually used to control the position and movement of the electrode sheet and the diaphragm, and even manual operation is added to improve the alignment accuracy of the cell. This greatly reduces the production efficiency of the battery, and it is difficult to achieve high alignment accuracy. In the prepared lithium ion battery, the electrode sheet misalignment phenomenon still exists, which causes the capacity of the battery to decrease, and even causes safety accidents. SUMMARY

[0004] The present application provides a compound tab, an electrode assembly, a secondary battery and an electric device to alleviate the relative sliding during the electrode sheet assembly process.

[0005] The first aspect of the present application provides a compound tab, the compound tab comprising two single tabs, each single tab comprising: a current collector, the current collector having a main body and a protruding portion, the protruding portion being protrudingly arranged relative to the main body in the extension direction of the current collector, the protruding portions of the two current collectors being fixedly connected; an active material layer arranged on one surface of the main body, the active material layers of the two single tabs being oppositely arranged.

[0006] The current collector of the compound electrode in this application has a main body and a protrusion. The main body is used to support the active material layer, and the protrusion is set out relative to the main body. The main bodies of the two current collectors are arranged facing each other. Therefore, the current collectors can be fixedly connected by the protrusions of the two current collectors, which effectively alleviates the relative slippage of the electrodes during the assembly process. At the same time, the main body and the protrusion are independent of each other. Therefore, fixing the protrusion does not affect the setting of the active material layer on the surface of the main body, thereby avoiding the problem of insufficient safety size reserved for the negative electrode due to relative slippage of the electrodes and improving the safety of the battery. Moreover, the compound electrode of this application can be realized without complex tooling and does not increase the labor operation cost, resulting in high production efficiency.

[0007] In any embodiment of the first aspect, the protrusions of the two current collectors are fixedly connected by an adhesive layer; optionally, the adhesive layer is a thermoplastic polymer adhesive layer; optionally, the thermoplastic polymer adhesive layer is selected from any one of thermoplastic polypropylene adhesive layer, thermoplastic aliphatic polyether polyurethane adhesive layer, thermoplastic polyimide adhesive layer, and thermoplastic vinyl bis-stearamide adhesive layer. Fixing the protrusions with an adhesive layer is a simple process with good insulation.

[0008] In any embodiment of the first aspect, the adhesive layer fills between the protrusions and / or covers the protrusions. The position of the adhesive layer can be achieved by adjusting the process operation.

[0009] In any embodiment of the first aspect, the protrusions of the two current collectors are welded together, and the current collectors are fixedly connected by welding, resulting in a better and more durable fixing effect.

[0010] In any embodiment of the first aspect, the aforementioned compound electrode further includes an insulating layer that covers the welding area of ​​the protrusion; the insulating layer covers the welding area to avoid unnecessary short circuits caused by the protrusion in the electrode assembly.

[0011] In any embodiment of the first aspect, the insulating layer comprises an inorganic filler and a binder; optionally, the inorganic filler is selected from boehmite, ceramic materials, or any one or more of these; optionally, by weight percentage, the insulating layer comprises 80% to 95% inorganic insulating filler and 5% to 20% binder. The inorganic insulating filler used in the above insulating layer is low in cost and has good insulation effect, and when combined with the binder, it forms good coverage and insulation in the welding area.

[0012] In any embodiment of the first aspect, there are multiple protrusions spaced apart from each other; optionally, the protrusions are disposed on at least one side of the main body; optionally, the fixed connection area of ​​each protrusion is 8 mm². 2 ~50mm 2Optionally, the protrusions are quadrilateral in shape, and further optionally rectangular in shape. The more protrusions are provided, the larger the fixed connection area is, and the better the fixing effect is, but the cost is also higher.

[0013] In any embodiment of the first aspect, the protrusions are annular protrusions arranged continuously along the circumference of the body, and the annular protrusions of the two current collectors are fixedly connected continuously in the circumference. The annular protrusions are fixedly connected continuously in the circumference, and the fixing effect is more firm, thereby avoiding the entry of the electrolyte to cause poor contact between the two current collectors. Moreover, when a lithium layer is arranged between the two current collectors, the entry of the electrolyte into the interlayer between the two current collectors is effectively avoided to cause corrosion of the lithium layer.

[0014] In any embodiment of the first aspect, the width of the annular protrusion is 2-5 mm. The sufficient arrangement position is provided for the glue layer or welding, and the increase in the volume of the electrode assembly caused by the protrusion being too large is avoided.

[0015] In any embodiment of the first aspect, the complex tab further comprises a lithium layer, the current collector is a porous current collector, the lithium layer is arranged between the bodies of the two current collectors, and the two single tabs are negative tabs. When the lithium layer is arranged, the protrusions are preferably annular protrusions, and the annular protrusions are fixedly connected continuously in the circumference to effectively avoid the entry of the electrolyte into the interlayer between the two current collectors to cause corrosion of the lithium layer.

[0016] In any embodiment of the first aspect, the current collector further has a tab, the tab is arranged on the body or at an end of the protrusion away from the body; and optionally, the body, the protrusion and the tab are integrally arranged. This facilitates the packaging of the electrode assembly.

[0017] In any embodiment of the first aspect, one single tab is a positive tab, and the other single tab is a negative tab; and optionally, the current collector of the positive tab is an aluminum foil, and the current collector of the negative tab is a copper foil. The complex tab formed by this embodiment is a series tab, and when the battery cell is arranged, only the tabs of the outermost positive tab and negative tab need to be connected with the external circuit, and the tabs of the complex tabs in the middle do not need to be connected with the external circuit. In addition, when applied to a secondary battery, the use of gel electrolyte or solid-state electrolyte as the electrolyte can insulate the ions between the positive and negative tabs of the complex tab, thereby avoiding internal short circuit.

[0018] In the second aspect of the application, an electrode assembly is provided, comprising a tab and a separator, wherein the tab comprises any of the complex tabs described above. Since the complex tab of the application effectively avoids the problem that the relative sliding of the tabs during the assembly of the tabs causes the safety size of the negative tab to be insufficient, the safety of the electrode assembly is improved.

[0019] In any embodiment of the second aspect, the complex tab is a complex negative tab, the complex tab further comprises a lithium layer, the current collector is a porous current collector, the lithium layer is disposed between the two bodies of the current collector, and the electrode assembly comprises the complex negative tab and the double-sided positive tab stacked in sequence and the separator disposed between the complex negative tab and the double-sided positive tab.

[0020] In any embodiment of the second aspect, one single tab of the complex tab is a positive tab, and the other single tab is a negative tab, and the electrode assembly comprises the complex tab stacked in sequence and the separator disposed between the complex tab.

[0021] In any embodiment of the second aspect, the electrode assembly described above is a battery cell, and the battery cell is a jelly-roll battery cell, and the protruding part of the complex tab in the jelly-roll battery cell is disposed at both ends of the jelly-roll battery cell.

[0022] In any embodiment of the second aspect, the electrode assembly described above is a battery cell, and the battery cell is a jelly-roll battery cell, and the protruding part of the complex tab in the jelly-roll battery cell is disposed at both ends of the jelly-roll battery cell.

[0023] In a third aspect of the present application, a secondary battery is provided, wherein the secondary battery comprises any one of the complex tabs described above or any one of the electrode assemblies described above.

[0024] In a fourth aspect of the present application, a power device is provided, wherein the power device comprises a secondary battery, and the secondary battery is selected from the secondary batteries described above.

[0025] Since the complex tab of the present application effectively alleviates the problem of insufficient safety size of the negative electrode reserved due to the relative sliding of the tabs during the tab assembly process, and improves the safety of the battery, the power device with the complex tab also has higher safety. BRIEF DESCRIPTION OF DRAWINGS

[0026] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed in the embodiments of the present application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor on the basis of the drawings.

[0027] Figure 1 A cross-sectional structure schematic diagram of the complex tab provided for an embodiment.

[0028] Figure 2 A cross-sectional structure schematic diagram of the complex tab shown at A-A'. Figure 1 A cross-sectional structure schematic diagram of the complex tab shown at A-A'.

[0029] Figure 3 A cross-sectional structure schematic diagram of the complex tab shown at A-A'. Figure 1Another cross-sectional structure schematic view of the compound pole piece is shown at A-A'.

[0030] Figure 4 A cross-sectional structure schematic view of the compound pole piece is shown at A-A'. Figure 1 Another cross-sectional structure schematic view of the compound pole piece is shown at A-A'.

[0031] Figure 5 A cross-sectional structure schematic view of the compound pole piece is shown at A-A'.

[0032] Figure 6 A cross-sectional structure schematic view of the compound pole piece is shown at A-A'.

[0033] Figure 7 A cross-sectional structure schematic view of the compound pole piece is shown at A-A'.

[0034] Figure 8 A cross-sectional structure schematic view of the electrode assembly is shown at A-A'.

[0035] Figure 9 A cross-sectional structure schematic view of the electrode assembly is shown at A-A'.

[0036] Figure 10 A schematic view of a secondary battery is shown at A-A'.

[0037] Figure 11 A schematic view of a secondary battery is shown at A-A'. Figure 10 An exploded view of the secondary battery is shown at A-A'.

[0038] Figure 12 A schematic view of a battery module is shown at A-A'.

[0039] Figure 13 A schematic view of a battery pack is shown at A-A'.

[0040] Figure 14 A schematic view of a battery pack is shown at A-A'. Figure 13 An exploded view of the battery pack is shown at A-A'.

[0041] Figure 15 A schematic view of an electric device using the secondary battery as a power source is shown at A-A'.

[0042] In the drawings, the drawings are not drawn according to the actual scale.

[0043] Explanation of Reference Numerals:

[0044] 10 collector; 11 main body; 12 protrusion; 20 active material layer; 31 adhesive layer; 32 insulation layer; 40 lithium layer; 01 complex negative electrode sheet; 02 double-sided positive electrode sheet; 03 separator; 04 complex electrode sheet; 1 battery pack; 2 upper case; 3 lower case; 4 battery module; 5 secondary battery; 51 case; 52 electrode assembly; 53 top cover assembly. DETAILED DESCRIPTION

[0045] The embodiments of the present application will be described in further detail below with reference to the accompanying drawings and examples. The detailed description of the following examples and the accompanying drawings are intended to illustrate the principles of the present application by way of example only and are not intended to limit the scope of the present application, that is, the present application is not limited to the described examples.

[0046] Hereinafter, the embodiments of the complex electrode sheet, the electrode assembly, the secondary battery, the battery module, the battery pack, and the electric device of the present application are specifically disclosed in detail with appropriate reference to the accompanying drawings. However, there are cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of matters well known in the art, repeated descriptions of substantially identical structures are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand the present application, and are not intended to limit the subject matter recited in the claims.

[0047] The "ranges" disclosed in the present application are defined in the form of lower and upper limits, and a given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of a particular range. The ranges defined in this way can include or exclude the end values, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a range. For example, if the ranges of 60-120 and 80-110 are listed for a particular parameter, it is understood that the ranges of 60-110 and 80-120 are also contemplated. In addition, if the minimum range values of 1 and 2 are listed, and if the maximum range values of 3, 4, and 5 are listed, the following ranges are all contemplated: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In the present application, unless otherwise stated, the numerical range "a-b" represents a shorthand notation for any real combination of numbers between a and b, where a and b are both real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" have been listed herein, and "0-5" is just a shorthand notation for these numerical combinations. In addition, when it is stated that a parameter is an integer ≥ 2, it is equivalent to disclose that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0048] All embodiments of the present application and optional embodiments can be combined with each other to form new technical solutions, if not specifically stated.

[0049] All the technical features and optional technical features of the present application can be combined with each other to form new technical solutions, if not specifically stated.

[0050] All the steps of the present application can be performed in sequence or randomly, if not specifically stated. For example, the method comprises steps (a) and (b) means that the method can comprise steps (a) and (b) performed in sequence, or steps (b) and (a) performed in sequence. For example, the method can further comprise step (c) means that step (c) can be added to the method in any sequence, for example, the method can comprise steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), etc.

[0051] The terms “comprise” and “contain” mentioned in the present application mean open or closed, if not specifically stated. For example, the terms “comprise” and “contain” can mean that other components not listed can also be included or contained, or only the listed components can be included or contained.

[0052] The term “or” in the present application is inclusive, if not specifically stated. For example, the phrase “A or B” means “A, B, or both A and B”. More specifically, any one of the following conditions satisfies the condition “A or B”: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0053] [Secondary battery]

[0054] A secondary battery, also known as a rechargeable battery or a storage battery, refers to a battery that can continue to be used by activating active materials through charging after the battery is discharged.

[0055] Generally, a secondary battery comprises a positive electrode sheet, a negative electrode sheet, a separator, and an electrolyte. During the charging and discharging process of the battery, active ions (such as lithium ions or sodium ions) are inserted and extracted between the positive electrode sheet and the negative electrode sheet. The separator is arranged between the positive electrode sheet and the negative electrode sheet, mainly to prevent short circuit between the positive electrode and the negative electrode, and at the same time to allow the active ions to pass through. The electrolyte is between the positive electrode sheet and the negative electrode sheet, mainly to conduct the active ions.

[0056] In the present application, the positive electrode sheet and / or the negative electrode sheet of the secondary battery can be in the form of a complex sheet as described below.

[0057] [Complex electrode sheet]

[0058] One embodiment of the present application provides a complex electrode sheet, such as Figures 1 to 7As shown, the compound pole piece includes two single pole pieces, each single pole piece includes: a current collector 10 and an active material layer 20, the current collector 10 has a main body 11 and a protruding portion 12, the protruding portion 12 is arranged protruding relative to the main body 11 in the extension direction of the current collector 10, and the protruding portions 12 of the two current collectors 10 are fixedly connected; the active material layer 20 is arranged on one surface of the main body 11, and the active material layers 12 of the two single pole pieces are arranged opposite to each other.

[0059] The current collector 10 of the compound pole piece of the present application has a main body 11 and a protruding portion 12, as Figures 2 to 4 As shown, the main body 11 is used to carry the active material layer 20, and the protruding portion 12 is arranged protruding relative to the main body 11, so that the current collector 10 can be fixed relative to the fixed connection of the protruding portions 12 of the two current collectors 10, effectively alleviating the relative sliding of the pole piece during the pole piece assembly process. At the same time, the main body 11 and the protruding portion 12 are independent of each other, so that the fixing of the protruding portion 12 does not affect the arrangement of the active material layer 20 on the surface of the main body 11, thereby avoiding the problem of insufficient safety size of the negative electrode reserved due to the relative sliding of the pole piece, and improving the safety of the battery. Moreover, the compound electrode of the present application can be realized without complex tooling, and without increasing the labor operation cost, and has high production efficiency.

[0060] The fixed connection of the protruding portion 12 can be realized in various ways, such as cementing or welding, etc.

[0061] In some embodiments, as Figure 1 As shown, the protruding portions 12 of the above two current collectors 10 are fixedly connected by a glue layer 31. Optionally, the glue layer 31 can be an insulating glue layer or a conductive glue layer. The protruding portions 12 are fixed by the glue layer 31, which is simple in process and good in insulation.

[0062] After bonding by the glue layer 31, in order to avoid the limitation of the ductility of the current collector 10 caused by bonding, optionally, the glue layer 31 is a thermoplastic polymer glue layer, which has high elasticity, so as to comply with the ductility of the current collector 10 and meet the requirements of the compound pole piece for preparing an electrode assembly. Optionally, the thermoplastic polymer glue layer 31 is selected from any one of a thermoplastic polypropylene glue layer, a thermoplastic aliphatic polyether polyurethane glue layer, a thermoplastic polyimide glue layer and a thermoplastic vinyl bis-stearamide glue layer. Each type of thermoplastic polymer glue layer is formed of a known thermoplastic polymer material, and each thermoplastic polymer glue layer has chemical resistance, heat resistance, electrical insulation, high strength mechanical properties and good high wear resistance processing performance.

[0063] When the protruding portions 12 are fixedly connected by the glue layer 31, there are various setting modes of the glue layer 31 on the protruding portions 12, such as the glue layer 31 being filled between the protruding portions 12 and / or the glue layer 31 wrapping the protruding portions 12. The position of the glue layer 31 can be realized by adjusting the process operation.

[0064] When the adhesive layer 31 is filled between the protrusions 12, after the setting of one electrode is completed, a thermoplastic polymer adhesive is applied to the protrusion 12, and then the protrusion 12 of the other electrode is hot-pressed and bonded to it and cooled. At this time, the adhesive layer 31 can be an insulating adhesive layer 31 or a conductive adhesive layer 31.

[0065] When the adhesive layer 31 covers the protrusion 12, or is both disposed between and covers the protrusion 12, the two monopolar plates can be aligned, and then adhesive can be applied, coated, or impregnated onto the protrusion 12, followed by hot pressing and cooling. The adhesive layer 31 can be either an insulating or conductive layer, but is preferably an insulating layer.

[0066] By using a thermoplastic polymer adhesive layer 31 to bond the protrusion 12, the separation of the two current collectors 10 can be completed by heating the thermoplastic polymer adhesive layer when recycling the electrode.

[0067] In some implementations, such as Figure 5 As shown, the protrusions 12 of the two current collectors 10 are welded. Welding is used to fix the current collectors 10 together, resulting in a better and more durable fixation. The protrusions 12 can be welded using continuous ultrasonic welding. The specific welding process can be referenced from existing continuous ultrasonic welding technology, and will not be elaborated further.

[0068] When welding the protrusions 12 of the two current collectors 10, as follows: Figure 5 As shown, the aforementioned composite electrode also includes an insulating layer 32, which covers the welding area of ​​the protrusion 12. Covering the welding area with the insulating layer 32 prevents unnecessary short circuits caused by the protrusion 12 in the electrode assembly.

[0069] The insulating layer 32 can be made of the insulating layer commonly used in lithium batteries, for example, inorganic insulating material is used for insulation, and in some embodiments, the insulating layer 32 comprises inorganic filler and binder dispersant. As the name implies, since the inorganic filler and the binder are both used in the insulating layer, both are insulating materials. Optionally, the inorganic filler is selected from any one or more of boehmite, ceramic materials, including but not limited to alumina, magnesium oxide, zinc oxide, silicon oxide, titanium oxide, zirconium oxide, aluminum nitride, silicon nitride, calcium fluoride and barium fluoride. The inorganic filler used in the insulating layer 32 has low cost and good insulation effect, and by combining with the binder, a good coating and insulation is formed on the welding area. Optionally, the insulating layer 32 comprises 80% to 95% inorganic filler and 5% to 20% binder by weight. The binder can be selected from commonly used binders in lithium batteries, such as at least one of polyvinylidene fluoride, polyvinylidene fluoride, vinylidene-hexafluoropropylene copolymer, styrene-butadiene rubber, polyacrylic acid, polyethylene oxide, polyvinyl alcohol. In addition, the insulating layer can also contain 0% to 2% dispersant by mass content to facilitate uniform dispersion of the inorganic filler in the binder, which can also be selected from commonly used dispersants in lithium batteries, such as at least one of sodium carboxymethyl cellulose, polyvinyl pyrrolidone, styrene acrylate, etc. In the preparation of the insulating layer, the inorganic filler, binder and optional dispersant are dispersed in a solvent to form a slurry, and then the slurry is coated on the surface of the welding area of the protrusion, and after drying, the insulating layer is obtained. The solvent can be N-methyl pyrrolidone (NMP) or deionized water.

[0070] When the protrusion 12 is used to fix the current collector 10, the larger the area of the fixed region, the more secure the fixing effect, but the higher the cost.

[0071] In some embodiments, as shown in Figure 2 or Figure 3 , the protrusion 12 has multiple and is spaced apart, and the multiple protrusions 12 are spaced apart, for example, equidistantly arranged. Optionally, the protrusion 12 is arranged on any one or more side edges of the main body 11, for example, the protrusions 12 on the same edge are equidistantly arranged, and the distribution of the bonding force on the entire current collector 10 is more uniform, thereby better avoiding the sliding of the pole piece. In order to improve the fixing effect of each protrusion 12, the fixed connection area of each protrusion 12 is 8mm 2 ~ 50mm 2 . Of course, if the fixed connection area of each protrusion 12 is less than 8mm 2 , the number and arrangement density of the fixed connection area can be appropriately increased. Optionally, the shape of the protrusion 12 is quadrilateral, and further optionally rectangular.

[0072] In some implementations, such as Figure 4 As shown, the protrusions 12 are continuously arranged in annular form along the circumference of the main body 11, and the annular protrusions 12 of the two current collectors 10 are continuously and fixedly connected in the circumferential direction. The continuous and fixed connection of the annular protrusions 12 in the circumferential direction provides a more secure fixation and also prevents poor contact between the two current collectors 10 due to electrolyte ingress. In addition, when a lithium layer 40 is provided between the two current collectors 10, it effectively prevents electrolyte from entering the interlayer between the two current collectors 10 and causing erosion of the lithium layer 40.

[0073] In some embodiments, the width of the annular protrusion 12 is 2–5 mm. This provides sufficient space for the adhesive layer 31 or welding, and avoids an increase in the size of the electrode assembly due to an excessively large protrusion 12. Of course, if the width of the annular protrusion 12 is less than 2 mm, the requirement for sealing and forming a sandwich layer can also be met.

[0074] The compound electrode sheet of this application can also be structurally designed according to different functional requirements. For example, when it is a compound electrode sheet for a lithium-ion secondary battery, in some embodiments, such as... Figure 1 and Figure 5 As shown, the composite electrode also includes a lithium layer 40, and the current collector 10 is a porous current collector. The lithium layer 40 is disposed between the main bodies 11 of the two current collectors 10, and both single electrodes are negative electrodes. When the lithium layer 40 is provided, a lithium-supplemented composite electrode is formed. In order to meet the current rule that the positive electrode area is smaller than the negative electrode area in the assembly of conventional electrode components, both of the above single electrodes are preferably negative electrodes.

[0075] When a lithium layer 40 is provided, in order to further improve the lithium replenishment effect of the lithium layer 40, it is preferable that the protrusion 12 is an annular protrusion 12, and the annular protrusion 12 is continuously and fixedly connected in the circumferential direction to effectively prevent the electrolyte from entering the interlayer between the two current collectors 10 and causing erosion of the lithium layer 40.

[0076] Corresponding to the aforementioned lithium-filled composite electrode, the current collector 10 may optionally also have a tab, which is disposed on the main body or at the end of the protrusion 12 away from the main body 11. Optionally, the main body 11, the protrusion 12, and the tab are integrally disposed to facilitate the encapsulation of the electrode assembly.

[0077] In some implementations, such as Figure 6 and Figure 7As shown, one of the monopolar sheets is a positive sheet, and the other is a negative sheet; alternatively, the current collector 10 of the positive sheet is an aluminum foil, and the current collector 10 of the negative sheet is a copper foil. The formed complex sheet is a series sheet, and when the battery cell is arranged, only the outermost positive sheet and negative sheet need to be connected with the external circuit through the tab, and the middle complex sheet does not need to be connected with the external circuit through the tab. In addition, when applied to a secondary battery, the use of gel electrolyte or solid-state electrolyte as the electrolyte can insulate the positive and negative electrodes of the complex sheet, thereby avoiding internal short circuit.

[0078] Of course, if the above complex sheet is used as a series sheet, a lithium supplement layer can also be arranged between the two monopolar sheets, and the current collector of the negative sheet is a porous current collector to supplement lithium to the negative electrode.

[0079] The manufacturing process of the complex sheet shown in Figure 6 and Figure 7 The manufacturing process of the complex sheet shown in

[0080] Figure 6 The manufacturing process of the complex sheet shown in

[0081] The thermoplastic polymer glue is dissolved in the corresponding solvent to form a glue solution; the edge of the current collector of the monopolar sheet is coated with a single-sided or double-sided glue solution of the thermoplastic polymer glue, and then the monopolar sheets to be bonded are aligned, the position coated with the glue solution is heated to melt the thermoplastic polymer glue, the multi-layer monopolar sheets are bonded into a complex sheet, and the excess empty foil area is removed by die cutting. If a tab is needed, a tab is left during cutting, or a separate tab is cut out.

[0082] Figure 7 The manufacturing process of the complex sheet shown in

[0083] The current collectors of the multi-layer monopolar sheets are aligned, the edge empty foil area of the current collector is fused and encapsulated by continuous ultrasonic welding, and then an optional insulating layer (not required) can be coated on the welded area to cover the welded area. If a tab is needed, a tab is left during cutting.

[0084] [Electrode assembly]

[0085] The electrode assembly includes a sheet and a separator, wherein the sheet includes any of the complex sheets described above. Since the complex sheet of the present application effectively avoids the problem of insufficient safety size of the negative electrode reserved due to the relative sliding of the sheet during the assembly of the sheet, the safety of the electrode assembly is improved.

[0086] When the functions of the complex tab are different, the assembly mode of the tab is adjusted according to the electrode assembly assembly rule, in some embodiments, the complex tab is a complex negative tab 01, the complex tab further includes a lithium layer, and the current collector is a porous current collector, and the lithium layer is arranged between the bodies of the two current collectors, as shown in Figure 8 The electrode assembly includes the complex negative tab 01 and the double-sided positive tab 02 arranged in sequence, and the separator 03 arranged between the complex negative tab 01 and the double-sided positive tab 02.

[0087] In some embodiments, one single tab in the complex tab 04 is a positive tab, and the other single tab is a negative tab, as shown in Figure 9 The electrode assembly includes the complex tab 04 arranged in sequence, and the separator 03 arranged between the complex tabs.

[0088] The above-mentioned "stacked arrangement" refers to the relative position relationship of the complex tab and the separator, which can be obtained by winding or stacking.

[0089] For example, when the electrode assembly is a battery cell and the battery cell is a winding type battery cell, the protruding part of the complex tab in the winding type battery cell is arranged at both ends of the winding type battery cell. When there are multiple protruding parts, the spacing of the protruding parts in the complex tab belt can be controlled to regularly distribute the protruding parts at both ends of the winding type battery cell, such as alignment in the alignment mode of the tab, and the tab is arranged at the end of the protruding part away from the body.

[0090] When the electrode assembly is a battery cell and the battery cell is a stacking type battery cell, the protruding part of the complex tab in the stacking type battery cell is arranged on any one or more side walls of the stacking type battery cell. When there are multiple protruding parts, the spacing of the protruding parts in each complex tab of the stack can be controlled to regularly distribute the protruding parts on the side wall of the stacking type battery cell, such as alignment in the alignment mode of the tab, and the tab is arranged at the end of the protruding part away from the body.

[0091] The positive tab and / or the negative tab as the single tab in the above-mentioned complex tab are both conventional tab structures of lithium batteries.

[0092] [Positive tab]

[0093] The positive tab generally includes a positive current collector and a positive film layer arranged on at least one surface of the positive current collector, and the positive film layer includes a positive active material.

[0094] As an example, the positive current collector has two opposite surfaces in the thickness direction of itself, and the positive film layer is arranged on any one or both of the two opposite surfaces of the positive current collector.

[0095] In some embodiments, the positive electrode current collector can employ a metal foil or a composite current collector. For example, as a metal foil, an aluminum foil can be employed. The composite current collector can include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector can be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, silver alloy, etc.) on a polymer material base material (e.g., a base material of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0096] In some embodiments, the positive electrode active material can employ a positive electrode active material for a battery known in the art. As an example, the positive electrode active material can include at least one of a lithium-containing phosphate of an olivine structure, a lithium transition metal oxide, and a modified compound of each thereof. However, the present application is not limited to these materials, and other conventional materials that can be used as a positive electrode active material for a battery can also be used. These positive electrode active materials can be used alone only one or in combination of two or more. Among them, examples of the lithium transition metal oxide can include, but are not limited to, lithium cobalt oxide (e.g., LiCoO2), lithium nickel oxide (e.g., LiNiO2), lithium manganese oxide (e.g., LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (e.g., LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2(also can be simply referred to as NCM 333 ), LiNi 0.5 Co 0.2 Mn 0.3 O2(also can be simply referred to as NCM 523 ), LiNi 0.5 Co 0.25 Mn 0.25 O2(also can be simply referred to as NCM 211 ), LiNi 0.6 Co 0.2 Mn 0.2 O2(also can be simply referred to as NCM 622 ), LiNi 0.8 Co 0.1 Mn 0.1 O2(also can be simply referred to as NCM 811 ), lithium nickel cobalt aluminum oxide (e.g., LiNi 0.85 Co 0.15 Al 0.05O2) and modified compounds thereof, etc. Examples of the lithium-containing phosphate of olivine structure can include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO4 (which can also be referred to simply as LFP)), a composite of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO4), a composite of lithium manganese phosphate and carbon, lithium manganese iron phosphate, and a composite of lithium manganese iron phosphate and carbon.

[0097] In some embodiments, the positive electrode film layer further optionally includes a binder. As an example, the binder can include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylate resin.

[0098] In some embodiments, the positive electrode film layer further optionally includes a conductive agent. As an example, the conductive agent can include at least one of super P, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0099] In some embodiments, the positive electrode tab can be prepared by dispersing the above-mentioned components for preparing the positive electrode tab, such as the positive electrode active material, the conductive agent, the binder, and any other components, in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry on a positive electrode current collector; and subjecting the same to processes such as drying, cold pressing, etc. to obtain the positive electrode tab.

[0100] [Negative electrode tab]

[0101] The negative electrode tab includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector, the negative electrode film layer including a negative electrode active material.

[0102] As an example, the negative electrode current collector has two surfaces opposite in the thickness direction thereof, and the negative electrode film layer is disposed on either one or both of the two opposite surfaces of the negative electrode current collector.

[0103] In some embodiments, the negative electrode current collector can employ a metal foil or a composite current collector. As a metal foil, for example, a copper foil can be employed. The composite current collector can include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector can be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, silver alloy, etc.) on a polymer material base layer (such as a base layer of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0104] In some embodiments, the negative active material can employ a negative active material for a battery known in the art. As an example, the negative active material can include at least one of artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based material, tin-based material, and lithium titanate, etc. The silicon-based material can be selected from at least one of elemental silicon, silicon oxide compound, silicon-carbon composite, silicon-nitrogen composite, and silicon alloy. The tin-based material can be selected from at least one of elemental tin, tin oxide compound, and tin alloy. However, the present application is not limited to these materials, and other conventional materials that can be used as a negative active material for a battery can also be used. These negative active materials can be used alone or in combination of two or more.

[0105] In some embodiments, the negative film layer can further optionally include a binder. As an example, the binder can be selected from at least one of styrene butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0106] In some embodiments, the negative film layer can further optionally include a conductive agent. As an example, the conductive agent can be selected from at least one of super conductive carbon, acetylene black, carbon black, ketjen black, carbon dot, carbon nanotube, graphene, and carbon nanofiber.

[0107] In some embodiments, the negative film layer can further optionally include other auxiliary agents, such as thickening agents (e.g., sodium carboxymethyl cellulose (CMC-Na)) and the like.

[0108] In some embodiments, the negative electrode sheet can be prepared by dispersing the above-mentioned components for preparing the negative electrode sheet, such as the negative active material, the conductive agent, the binder, and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry on a negative current collector, and after processes such as drying, cold pressing, etc., the negative electrode sheet can be obtained.

[0109] [Electrolyte]

[0110] The electrolyte plays a role of conducting ions between the positive electrode sheet and the negative electrode sheet. The present application does not have a specific limitation on the type of electrolyte, which can be selected as needed. For example, the electrolyte can be liquid, gel, or all-solid.

[0111] In some embodiments, the electrolyte is liquid and includes an electrolyte salt and a solvent.

[0112] In some embodiments, the electrolyte salt can be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bisfluorosulfonylimide, lithium bis-trifluoromethanesulfonylimide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluoro oxalato borate, lithium di oxalato borate, lithium difluoro di oxalato phosphate, and lithium tetrafluoro oxalato phosphate.

[0113] In some embodiments, the solvent can be selected from at least one of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, butyrosulfone, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0114] In some embodiments, the electrolyte solution can further optionally include an additive. As an example, the additive can include a negative electrode film-forming additive, a positive electrode film-forming additive, and can further include an additive capable of improving certain performance of the battery, such as an additive for improving overcharge performance of the battery, an additive for improving high-temperature or low-temperature performance of the battery, etc.

[0115] [Separator]

[0116] In some embodiments, the secondary battery further includes a separator. The type of the separator is not particularly limited in the present application, and any known porous structure separator having good chemical stability and mechanical stability can be used.

[0117] In some embodiments, the material of the separator can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single layer film or a multi-layer composite film, and is not particularly limited. When the separator is a multi-layer composite film, the materials of the respective layers can be the same or different, and are not particularly limited.

[0118] In some embodiments, the electrode assembly can be manufactured by a winding process or a stacking process.

[0119] In some embodiments, the secondary battery can include an outer package. The outer package can be used to package the above-described electrode assembly and electrolyte.

[0120] In some embodiments, the outer package of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer package of the secondary battery can also be a soft package, such as a pouch-type soft package. The material of the soft package can be plastic, and as the plastic, polypropylene, polybutylene terephthalate, polybutylene succinate, etc. can be listed.

[0121] The shape of the secondary battery is not particularly limited, and can be cylindrical, square, or any other shape. For example, Figure 10 is a square structure as an example of a secondary battery 5.

[0122] In some embodiments, referring to Figure 11 , the outer package can include a housing 51 and a cover plate 53. The housing 51 can include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover plate 53 can be provided on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet, and the separator can form an electrode assembly 52 through a winding process or a stacking process. The electrode assembly 52 is packaged in the receiving cavity. The electrolyte is impregnated in the electrode assembly 52. The number of electrode assemblies 52 contained in the secondary battery 5 can be one or more, and the skilled person can select according to the specific actual needs.

[0123] In some embodiments, the secondary battery can be assembled into a battery module, and the number of secondary batteries contained in the battery module can be one or more, and the specific number can be selected by the skilled person according to the application and capacity of the battery module.

[0124] Figure 12 is a battery module 4 as an example. Referring to Figure 12 , in the battery module 4, a plurality of secondary batteries 5 can be arranged in sequence along the length direction of the battery module 4. Of course, it can also be arranged in any other way. Further, the plurality of secondary batteries 5 can be fixed by fasteners.

[0125] Optionally, the battery module 4 can also include a housing having a receiving space, and the plurality of secondary batteries 5 are received in the receiving space.

[0126] In some embodiments, the above-mentioned battery module can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, and the specific number can be selected by the skilled person according to the application and capacity of the battery pack.

[0127] Figure 13 and Figure 14 is a battery pack 1 as an example. Referring to Figure 13 and Figure 14 , the battery pack 1 can include a battery box and a plurality of battery modules 4 arranged in the battery box. The battery box includes an upper box body 2 and a lower box body 3, and the upper box body 2 can be provided on the lower box body 3 to form a closed space for receiving the battery modules 4. The plurality of battery modules 4 can be arranged in the battery box in any way.

[0128] In addition, the application also provides a power utilization device comprising at least one of the secondary battery, the battery module, or the battery pack provided by the application. The secondary battery, the battery module, or the battery pack can be used as a power supply of the power utilization device, and can also be used as an energy storage unit of the power utilization device. The power utilization device can include a mobile device (such as a mobile phone, a notebook computer, etc.), an electric vehicle (such as a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a ship and a satellite, an energy storage system, etc., but is not limited thereto.

[0129] As the power utilization device, the secondary battery, the battery module, or the battery pack can be selected according to the use requirement thereof.

[0130] Figure 15 The power utilization device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. In order to meet the requirement of the power utilization device for high power and high energy density of the secondary battery, the battery pack or the battery module can be used.

[0131] [Embodiment]

[0132] Hereinafter, the embodiments of the application will be described. The embodiments described below are exemplary and are only used to explain the application, and cannot be understood as a limitation of the application. If the specific technology or condition is not indicated in the embodiments, the technology or condition described in the literature in the art or according to the product instruction is used. If the reagent or instrument used is not indicated by the manufacturer, it is a conventional product that can be obtained by market purchase.

[0133] Embodiment 1

[0134] The electrode assembly of the laminated battery is stacked in the order of "separator / double negative electrode sheet / separator / positive electrode sheet / separator" as shown in Figure 8 LiNi 0.8 Co 0.1 Mn 0.1O2(NCM811), conductive agent acetylene black, binder polyvinylidene fluoride (PVDF) were mixed in a mass ratio of 96:2:2, and mixed well in a solvent NMP to form a uniform positive electrode slurry. The positive electrode slurry was coated on the surface of the positive electrode current collector aluminum foil, and after drying, cold pressing, and cutting, the positive electrode sheet was obtained. The composite negative electrode sheet was composed of two single-sided negative electrode sheets and a lithium metal layer in the middle. The negative electrode current collector had a ring-shaped protrusion. The single-sided negative electrode sheet was made of graphite, silicon monoxide (the mass percentage of silicon element in the negative electrode active material layer was about 30%), binder styrene butadiene rubber (SBR), thickening agent sodium carboxymethyl cellulose (CMC), and conductive agent carbon nanotube in a mass ratio of 65:30:3:1:1, which were mixed well in deionized water to form a uniform negative electrode slurry. The negative electrode slurry was coated on the surface of the negative electrode porous current collector copper foil, and after drying, cold pressing, and cutting, the negative electrode sheet was obtained. The pure lithium metal layer between the two single-sided negative electrode sheets was attached to the surface of the negative electrode current collector by lithium strip calendering, with a thickness of 5 μm. The edge ring-shaped protrusion of the porous negative electrode current collector was bonded with a 5 mm wide polypropylene thermoplastic synthetic resin with a thickness of about 20 μm. After the two single-sided negative electrode sheets and the lithium metal layer were stacked, the edge ring-shaped protrusion was bonded and packaged by heating and pressing the polypropylene, and after cooling, the excess part was cut off, leaving a ring-shaped protrusion with a width of about 2 mm. The electrolyte was 1.0 M LiPF6 lithium salt and EC:DMC:EMC=1:1:1 solvent. The separator was a 12 μm thick polyethylene separator coated with a 3 μm thick aluminum oxide ceramic layer on both sides.

[0135] Example 2

[0136] The laminated battery had an electrode assembly structure as shown in Figure 8 , wherein the positive and negative electrode sheets, lithium layer, electrolyte, and stacking method were the same as in Example 1, except that the edge of the composite negative electrode sheet did not have a polypropylene thermoplastic synthetic resin. After the two single-sided negative electrode sheets and the lithium metal layer were stacked, the edge ring-shaped protrusion was welded and fused by ultrasonic welding with a power of 100 W and a welding energy of 600 J, with a welding width of 5 mm. The welding area was then coated with an inorganic insulating layer composed of 90% boehmite and 10% polyvinylidene fluoride adhesive, with a thickness of about 2 μm. Finally, the excess part was cut off, leaving a ring-shaped protrusion with a width of about 2 mm.

[0137] Example 3

[0138] The laminated battery had an electrode assembly structure as shown in Figure 9As shown, the positive and negative electrode sheets, lithium layer, and edge protrusion packaging methods are the same as in Example 1, except that both the positive and negative electrodes are single-sided electrodes, and the composite electrode sheets are "single-sided positive electrode sheet / single-sided negative electrode sheet". The upper coating area is wider for the single-sided negative electrode sheet and the negative electrode current collector is copper foil, while the lower coating area is narrower for the single-sided positive electrode sheet and the positive electrode current collector is aluminum foil. The battery cell is stacked in the order of "separator / composite electrode sheet / separator / composite electrode sheet / separator". The tabs are led out from the top negative electrode sheet and the bottom positive electrode sheet to connect to the external circuit. No tabs are led out between the intermediate composite electrode sheets. The electrolyte is a solid electrolyte, which consists of 75% lithium zirconium oxide (LLZO), 20% polyethylene oxide (PEO), and 5% LiClO4 to ensure ionic insulation between the positive and negative electrodes of the composite electrode sheets and prevent internal short circuits.

[0139] Example 4

[0140] Stacked cells, electrode assembly structure as follows Figure 9 As shown, the stacking method of the compound electrode, solid electrolyte and cell is the same as in Example 3. The edge encapsulation protrusion of the compound electrode adopts the same method as in Example 2, that is, the compound electrode is encapsulated by the same ultrasonic welding encapsulation + coating insulation layer method.

[0141] Comparative Example 1

[0142] The electrode assembly is directly stacked in the order of "single-sided positive electrode / separator / single-sided negative electrode / lithium layer / single-sided negative electrode / separator / single-sided positive electrode". The composition of each positive electrode, negative electrode, lithium layer, separator and electrolyte is the same as in Example 1.

[0143] Comparative Example 2

[0144] The electrode assembly is directly stacked in the order of "separator / single-sided positive electrode / lithium layer / single-sided negative electrode / separator", wherein the composition of each positive electrode, negative electrode, separator and solid electrolyte are the same as in Example 3.

[0145] The initial coulombic efficiency of each stacked cell was tested as follows:

[0146] The stacked battery was charged to 4.25V with a constant current of 1 / 3C, then charged to 0.05C with a constant voltage, and then discharged to 2.8V with a constant current of 1 / 3C. The charging capacity and discharging capacity of the stacked battery were recorded. Based on this, the initial coulombic efficiency of the battery was calculated as: initial discharge capacity / initial charging capacity.

[0147] The test results are recorded in Table 1.

[0148] Table 1

[0149] First coulombic efficiency (%) Example 1 89 Example 2 87 Example 3 80 Example 4 79 Comparative Example 1 83 Comparative Example 2 79

[0150] According to the comparison of the embodiments 1, 2 and the comparative example 1, it can be found that the use of the encapsulated complex tab can better protect the interlayer lithium layer from corrosion and loss of the electrolyte around, and maintain good electrical contact, thereby better playing the effect of lithium supplement, and the first coulomb efficiency of the tab battery is obviously improved. Moreover, according to the comparison of the embodiments 3, 4 and the comparative example 2, it can be seen that when the complex tab formed by the complex tab is used as the basic component structure of the battery cell, not only the relative sliding of the tab is effectively avoided, but also the first coulomb efficiency of the battery can be maintained.

[0151] Although the present application has been described with reference to the preferred embodiments, various modifications can be made to it without departing from the scope of the application, and equivalent parts can be substituted for the parts thereof. In particular, the technical features mentioned in each embodiment can be combined in any manner as long as there is no structural conflict. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A secondary battery comprising an electrode assembly and an electrolyte, the electrode assembly comprising a tab and a separator, the tab comprising a complex tab, the complex tab comprising two single tabs, each of the single tabs comprising: a current collector having a main body and a protrusion, the protrusion being provided protruding with respect to the main body in an extension direction of the current collector, the protrusions of the two current collectors being fixedly connected; an active material layer provided on one surface of the main body, wherein the active material layers of the two single tabs are provided opposite to each other, the electrode assembly comprising the complex tab and a double-faced positive tab provided in sequence and the separator provided between the complex tab and the double-faced positive tab, the complex tab further comprising a lithium layer, the current collector being a porous current collector, the lithium layer being provided between the main bodies of the two current collectors, both of the single tabs being negative tabs, the current collector of the single tab being a copper foil; or the electrode assembly comprising the complex tab provided in sequence and the separator provided between the complex tabs, one of the single tabs of the complex tab being a positive tab and the other of the single tabs being a negative tab, a lithium supplement layer being provided between the two single tabs, the current collector of the negative tab being a porous current collector, the electrolyte being a gel electrolyte or a solid electrolyte, the complex tab being a series tab. The protrusions of the two current collectors are fixedly connected by a glue layer. The glue layer is a thermoplastic polymer glue layer. The thermoplastic polymer glue layer is selected from any one of a thermoplastic polypropylene glue layer, a thermoplastic aliphatic polyether polyurethane glue layer, a thermoplastic polyimide glue layer and a thermoplastic vinyl bis-stearamide glue layer. The glue layer is filled between the protrusions and / or the glue layer wraps the protrusions. The protrusions of the two current collectors are welded. The complex tab further comprises an insulating layer, the insulating layer wrapping the welding area of the protrusions.

2. The secondary battery according to claim 1, wherein The insulating layer comprises an inorganic filler and a binder.

3. The secondary battery according to claim 2, wherein The inorganic filler is selected from any one or more of boehmite and a ceramic material.

4. The secondary battery according to claim 3, wherein The insulating layer comprises 80% to 95% of the inorganic filler and 5% to 20% of the binder by weight percentage.

5. The secondary battery according to any one of claims 2 to 4, wherein There are multiple protrusions and they are provided spaced apart from each other.

6. The secondary battery according to claim 1, wherein There are multiple protrusions and they are provided spaced apart from each other.

7. The secondary battery according to claim 6, wherein The protrusions are provided on at least one or more side edges of the main body.

8. The secondary battery according to claim 7, wherein The protrusions are provided on at least one or more side edges of the main body.

9. The secondary battery according to claim 8, wherein The shape of the protrusions is quadrilateral.

10. The secondary battery according to claim 8 or 9, wherein The shape of the protrusions is quadrilateral.

11. The secondary battery according to any one of claims 1 to 4, 6 to 9, wherein The shape of the protrusions is quadrilateral.

12. The secondary battery according to claim 5, wherein The shape of the protrusions is quadrilateral.

13. The secondary battery according to claim 11, wherein The shape of the protrusions is rectangular.

14. The secondary battery according to claim 12, wherein The protrusions are provided continuously along the circumference of the main body to form annular protrusions, and the annular protrusions of the two current collectors are fixedly connected continuously in the circumferential direction.

15. The secondary battery according to claim 11, wherein The fixed connection area of each of the protrusions is 8 mm 2 ~ 50 mm 2 .

16. The secondary battery according to claim 12, wherein The fixed connection area of each of the protrusions is 8 mm 2 ~ 50 mm 2 .

17. The secondary battery according to claim 13, wherein The fixed connection area of each of the protrusions is 8 mm 2 ~ 50 mm 2 .

18. The secondary battery of claim 14, wherein, The fixed connection area of each of the protrusions is 8 mm 2 ~ 50 mm 2 .

19. The secondary battery of claim 11, wherein, The protrusions are provided continuously along the circumference of the main body to form annular protrusions, and the annular protrusions of the two current collectors are fixedly connected continuously in the circumferential direction.

20. The secondary battery of claim 12, wherein, The width of the annular protrusions is 2 to 5 mm.

21. The secondary battery according to claim 13, wherein The width of the annular protrusions is 2 to 5 mm.

22. The secondary battery of claim 14, wherein, ​ 23. The secondary battery of claim 19, wherein, ​ 24. The secondary battery according to any one of claims 1 to 4, 6 to 9, wherein ​ 25. The secondary battery according to claim 5, wherein ​ 26. The secondary battery of claim 24, wherein, ​ 27. The secondary battery of claim 25, wherein, ​ 28. The secondary battery of claim 1, wherein, The current collector further has a tab, which is arranged on the main body or at an end of the partial protrusion away from the main body.

29. The secondary battery of claim 28, wherein, The main body, the protrusion and the tab are integrally arranged.

30. The secondary battery according to any one of claims 1 to 4, 6 to 9, wherein When one of the single pole pieces is a positive pole piece and the other is a negative pole piece, the current collector of the positive pole piece is an aluminum foil and the current collector of the negative pole piece is a copper foil.

31. The secondary battery according to claim 5, wherein When one of the single pole pieces is a positive pole piece and the other is a negative pole piece, the current collector of the positive pole piece is an aluminum foil and the current collector of the negative pole piece is a copper foil.

32. The secondary battery according to any one of claims 1 to 4, 6 to 9, wherein The electrode assembly is an electric core, The electric core is a jelly-roll type electric core, and the protrusion of the complex pole piece is arranged at two ends of the jelly-roll type electric core; or The electric core is a jelly-roll type electric core, and the protrusion of the complex pole piece is arranged at two ends of the jelly-roll type electric core; or 33. The secondary battery of claim 5, wherein, The electrode assembly is an electric core, The electric core is a jelly-roll type electric core, and the protrusion of the complex pole piece is arranged at two ends of the jelly-roll type electric core; or The electric core is a jelly-roll type electric core, and the protrusion of the complex pole piece is arranged at two ends of the jelly-roll type electric core; or 34. An electrically powered device comprising a secondary battery, wherein, The secondary battery is selected from the secondary battery of any one of claims 1 to 33.

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