Secondary battery, electric device, and method for manufacturing secondary battery

Abstract

The application relates to the technical field of energy storage, in particular to a secondary battery, a power utilization device and a preparation method of the secondary battery. The secondary battery comprises an electrode assembly, the electrode assembly comprises a first pole piece, a second pole piece and a diaphragm, the diaphragm is arranged between the first pole piece and the second pole piece, the first pole piece, the second pole piece and the diaphragm are laminated and wound to form a winding structure, the first pole piece comprises a first lug, a first current collector and a first active material layer, along the width direction of the first pole piece, the first current collector comprises a first coating section and a first empty foil section located at least one end of the first coating section, along the thickness direction of the first pole piece, the first active material layer is arranged on the first surface of the first coating section and / or the second surface of the first coating section. The first empty foil section comprises a first part and a second part connected with the first coating section, the first part is connected with the second part and laminated with the second part along the thickness direction of the first pole piece.

Description

TECHNICAL FIELD

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

[0002] With the continuous pursuit of high energy density, electrodes tend to have higher active material coating amount, higher compaction density and thinner current collector thickness design, which causes the active material to expand and shrink more during the pressure or charging and discharging process of the battery cell, the electrode deformation amount increases, and the local stress borne by the electrode current collector increases, thereby the problem of current collector fracture is prone to occur. SUMMARY

[0003] The inventor found through a large number of experiments that the fracture of the current collector often starts from the edge of the current collector, and as the use time of the battery increases, the damaged area gradually increases, until it spreads to the entire current collector, and finally leads to the fracture of the current collector. In view of this, the present application provides a secondary battery, a power utilization device and a preparation method of the secondary battery, which can improve the problem of current collector fracture.

[0004] In a first aspect, embodiments of the present application provide a secondary battery, comprising an electrode assembly, the electrode assembly comprising a first electrode sheet, a second electrode sheet and a separator, the separator being arranged between the first electrode sheet and the second electrode sheet, the first electrode sheet, the second electrode sheet and the separator being stacked and wound to form a wound structure, the first electrode sheet comprising a first tab, a first current collector and a first active material layer, along the width direction of the first electrode sheet, the first current collector comprising a first coating section and a first empty foil section located at at least one end of the first coating section, along the thickness direction of the first electrode sheet, the first active material layer being arranged on the first surface of the first coating section and / or the second surface of the first coating section. The first empty foil section refers to a part of the current collector at at least one end of the first coating section which is not provided with the first active material layer. The first empty foil section comprises a first part and a second part connected to the first coating section, and the first part is connected to the second part and stacked with the second part along the thickness direction of the first electrode sheet. By arranging the first empty foil section at the edge of the first electrode sheet and stacking the first part and the second part of the first empty foil section, the thickness of the edge of the first current collector is increased, thereby increasing the strength of the edge of the first current collector, which can effectively reduce the occurrence of the overall fracture of the current collector caused by the tearing of the edge of the current collector.

[0005] In the above embodiments, in the same winding layer, the first part is closer to the winding center of the electrode assembly than the second part. By arranging the first part to be closer to the winding center of the electrode assembly than the second part, after the winding of the electrode assembly is completed, the first part is wound into the inside of the electrode assembly, which is conducive to reducing the occurrence of the first part being raised after being bent.

[0006] In one or more of the embodiments above, along the width direction of the first pole piece, the width of the first part is L1, the width of the second part is L2, and 0≤L2-L1≤0.4 mm. L2-L1≤0.4 mm means that the difference between the widths of the first part and the second part is less than or equal to 0.4 mm, that is, the overlapping area of the first part and the second part is large, at this time, the breaking strength of the edge of the first current collector is larger, at the same time, the first empty foil section occupies less space in the width direction of the first pole piece, which is beneficial to improve the energy density of the secondary battery, and the first part has a certain bending length, which improves the bending convenience of the first part; when L2-L1<0, that is, the width of the first part is greater than the width of the second part, at this time, the first part will cover part of the first active material layer on the first coating section, L2-L1≥0 can reduce the occupation of the first empty foil section to the first active material layer in the first coating section, and further reduce the influence of the first empty foil section on the energy density of the secondary battery.

[0007] In one or more of the embodiments above, the first pole piece further comprises an adhesive, the adhesive is arranged on the first surface of the first empty foil section, and the adhesive is connected between the first part and the second part. The adhesive is arranged to fix the relative position of the first part and the second part, and to reduce the occurrence of the first part rebounding after bending.

[0008] In one or more of the embodiments above, the adhesive is single-sided tape, double-sided tape or hot melt adhesive.

[0009] In one or more of the embodiments above, the adhesive is hot melt adhesive, which is convenient for hot pressing after the first part and the second part are stacked to bond the adhesive between the first part and the second part.

[0010] In one or more of the embodiments above, the material of the adhesive comprises at least one of polyamide, reactive polyurethane or polyether sulfone. The above-mentioned materials are all thermoplastic polymer materials with heat resistance, acid resistance and insulation performance, and can form strong adhesion with metal, and can provide adhesion between the first part and the second part.

[0011] In one or more of the embodiments above, the melting temperature of the hot melt adhesive is T, and 45℃≤T≤65℃. The hot melt adhesive has good thermoplasticity in this temperature range. If the temperature is too low, the hot melt adhesive has poor adhesion. If the temperature is too high, the hot melt adhesive has too low viscosity and strong flowability, which is easy to be squeezed out of the first empty foil section and overflow to the surface of the first active material layer, affecting the transmission path of the positive electrode, leading to limited capacity development and low capacity of the battery cell.

[0012] In one or more of the embodiments above, the thickness of the thickest part of the adhesive is H2, and 5um≤H2≤20um. The thickest part of the adhesive is controlled to be greater than 5um to make the adhesive have sufficient adhesion strength. The thickest part of the adhesive is controlled to be less than 20um to reduce the occupation of the adhesive in the thickness direction.

[0013] In one or more of the embodiments above, along the width direction of the first tab, the width of the bonding member is equal to the width of the overlap of the first part and the second part, and after the first part and the second part overlap, the bonding member is located between the first part and the second part along the thickness direction of the first tab, which can better bond the first part and the second part and reduce the space occupied by the bonding member in the width direction of the first tab, thereby facilitating the improvement of the energy density of the secondary battery.

[0014] In one or more of the embodiments above, the first tab further comprises an insulating member, and the insulating member is arranged on the second surface of the first hollow foil segment, thereby isolating the second tab from contacting the first hollow foil segment and playing a role of insulation protection.

[0015] In one or more of the embodiments above, the material of the insulating member comprises a ceramic material. In one or more of the embodiments above, the ceramic material comprises at least one of aluminum oxide, magnesium oxide, silicon nitride, silicon carbide, and boehmite.

[0016] In one or more of the embodiments above, along the width direction of the first tab, the projection of the insulating member is located within the projection of the first active material layer. Along the thickness direction of the first tab, the thickness of the first hollow foil segment provided with the insulating member does not exceed the first active material layer, and the first hollow foil segment and the insulating member do not additionally occupy the space in the thickness direction of the electrode assembly, thereby facilitating the improvement of the energy density of the secondary battery.

[0017] In one or more of the embodiments above, along the thickness direction of the first tab, the projection of the insulating member is located within the projection of the second tab. The first hollow foil segment and the insulating member do not additionally occupy the space in the length direction of the electrode assembly, thereby facilitating the improvement of the energy density of the secondary battery.

[0018] In one or more of the embodiments above, along the width direction of the first tab, the single-side width of the second tab beyond the first active material layer is Δd, and 0.2mm≤Δd≤1.4mm. The single-side width Δd of the second tab beyond the first active material layer is controlled to be between 0.2mm and 1.4mm, thereby facilitating the provision of sufficient space for the first hollow foil segment.

[0019] In one or more of the embodiments above, along the width direction of the first tab, the width of the orthographic projection of the first hollow foil segment in the thickness direction of the first tab is W1, and 0.2mm≤W1≤1.4mm. The width W1 of the first hollow foil segment is controlled to be between 0.2mm and 1.4mm, which is the same range as the single-side width Δd of the second tab beyond the first active material layer, and along the width direction of the first tab, the width of the first hollow foil segment does not exceed the second tab, and the first hollow foil segment does not additionally occupy the space in the length direction of the electrode assembly, thereby facilitating the improvement of the energy density of the secondary battery.

[0020] In one or more of the embodiments above, the maximum distance between the insulating member on the first part and the insulating member on the second part along the thickness direction of the first tab is H1, and 31um≤H1≤100um.

[0021] In one or more of the embodiments above, the thickness of the insulating member is H3, and 5um≤H3≤20um.

[0022] In one or more of the embodiments above, the first current collector further comprises a connecting part, and the first tab is welded to the connecting part. The first tab is directly welded to the connecting part of the first current collector, thereby improving the connection stability of the first tab.

[0023] In one or more of the embodiments above, a plurality of first tabs are provided, each of which is connected to and integrally arranged with the first part, and each of which comprises a bending part connected to the first part and an extension part extending along the width direction of the first tab. The bending part of the first tab is folded together with the first part, which is conducive to improving the root strength of the first tab and thereby improving the problem of root fracture of the first tab caused by expansion and stress concentration of the root of the first tab.

[0024] In one or more of the embodiments above, the outermost tab of the electrode assembly is the first tab. In the electrode assembly of the winding structure, to reduce the waste of the active material layer, the outermost tab is generally a single-sided active material layer, which results in that the outermost tab has lower strength and is more prone to current collector fracture compared with the tab with a double-sided active material layer. The application of the technical solution to the outermost tab of the winding electrode assembly can reduce the occurrence of fracture of the outermost tab.

[0025] In one or more of the embodiments above, the first tab is a positive electrode.

[0026] In a second aspect, the embodiments of the present application provide a use electric device, comprising the secondary battery in one or more of the embodiments above.

[0027] In a third aspect, the embodiments of the present application provide a preparation method of a secondary battery, for preparing the secondary battery in one or more of the embodiments above, comprising the following steps:

[0028] providing a first current collector, dividing the first current collector into a first coating section and a first unfolded empty foil section located at at least one end of the first coating section along the width direction of the first current collector, and arranging a first active material layer on the first surface of the first coating section and / or the second surface of the first coating section;

[0029] folding, the first unfolded empty foil section comprises a first part and a second part connected to the first coating section, the first part is folded towards the second part, so that the first part and the second part are stacked along the thickness direction of the first tab, and a first empty foil section is obtained.

[0030] In one or more of the embodiments above, the bending direction of the first portion is a direction towards the winding center of the electrode assembly.

[0031] In one or more of the embodiments above, along the width direction of the first current collector, the width of the first portion and the second portion are equal; the width of the first unfolded empty foil segment is W2, 0.4mm≤W2≤2.8mm.

[0032] In one or more of the embodiments above, the bending step further comprises:

[0033] The adhesive is arranged on the first surface of the first portion and / or the first surface of the second portion; after the bending, the first surface of the first portion faces the first surface of the second portion.

[0034] In one or more of the embodiments above, the method further comprises the following steps:

[0035] The insulating member is arranged on the second surface of the first portion and the second surface of the second portion.

[0036] The secondary battery of the present application, since at least one end of the first coated segment along the width direction of the first electrode tab is the first empty foil segment, and after the first portion and the second portion at least partially overlap, the two side edges of the first electrode tab in the width direction are thickened. During the compression or charging and discharging process of the secondary battery, by increasing the thickness of the side edges of the first current collector in the width direction, the anti-fracture strength of the first electrode tab is increased, and the problem of fracture of the first current collector due to the expansion force during the cycle process is improved. BRIEF DESCRIPTION OF DRAWINGS

[0037] Figure 1 is a schematic diagram of the overall structure of the secondary battery in an embodiment of the present application.

[0038] Figure 2 is a schematic diagram of the overall structure of the secondary battery in an embodiment of the present application. Figure 1 is a schematic diagram of the overall structure of the secondary battery in an embodiment of the present application.

[0039] Figure 3 is a schematic diagram of the cross-sectional structure of the electrode assembly in an embodiment of the present application.

[0040] Figure 4 is a schematic diagram of the cross-sectional structure of the electrode assembly in an embodiment of the present application.

[0041] Figure 5 is a schematic diagram of the cross-sectional structure of the electrode assembly in another embodiment of the present application.

[0042] Figure 6 is a schematic diagram of the structure of the electrical equipment in an embodiment of the present application.

[0043] Figure 7This is a schematic diagram of the unfolded structure of the first electrode sheet in one embodiment of this application.

[0044] Figure 8 This is a schematic diagram of the structure after the first and second parts are stacked in one embodiment of this application.

[0045] Explanation of main component symbols

[0046] 001 Secondary Battery

[0047] 100 housing

[0048] 110 cavity

[0049] 200 electrode assembly

[0050] 210 First Polar Film

[0051] 211 First Current Collector

[0052] 2111 First Surface

[0053] 2112 Second Surface

[0054] 2113 First Coating Section

[0055] 2114 First Empty Foil Segment

[0056] 2114a Part 1

[0057] 2114b Part Two

[0058] 2115 Connecting part

[0059] 212 First active substance layer

[0060] 213 Adhesive components

[0061] 214 Insulating components

[0062] 220 Second Electrode

[0063] 221 Second Current Collector

[0064] 222 Second active substance layer

[0065] 230 diaphragm

[0066] 300 First Pole Ear

[0067] 310 Bending section

[0068] 320 Introduction

[0069] 400 Second Pole Ear

[0070] 002 Electrical Equipment Detailed Implementation

[0071] The technical solutions in the embodiments of the present application will be described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, not all the embodiments of the present application.

[0072] It should be noted that when one element is considered to be "connected" to another element, it can be directly connected to the other element or can exist simultaneously with a centrally arranged element. When one element is considered to be "arranged on" another element, it can be directly arranged on the other element or can exist simultaneously with a centrally arranged element. In the present application, unless otherwise specified and limited, the terms "mounting", "connection", "connection", "fixing" and the like should be understood in a broad sense, for example, it can be fixedly connected, or it can be detachably connected, or it can be integrally connected; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium, and it can be the communication between two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0073] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present application belongs. The terms used in the specification of the present application are only for the purpose of describing the specific embodiments and are not intended to limit the present application. The terms "include" and "have" and their any variations in the specification and claims of the present application and the above description of drawings are intended to cover the non-exclusive inclusion.

[0074] In the description of the embodiments of the present application, the technical terms "first", "second" and the like 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 explicitly specified.

[0075] In this paper, the reference to "embodiments" means that the specific features, structures or properties described in conjunction with the embodiments can be included in at least one embodiment of the present application. The phrase appears in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment to other embodiments. In the case of no conflict, the various embodiments in the present application can be combined with each other. In the method steps, S1, S2, etc. only represent the name of the step, and do not limit the order of the steps.

[0076] It should be noted that the thickness, length, width and other dimensions of various components in the embodiments of the present application and the overall thickness, length, width and other dimensions of the integrated device shown in the drawings are only exemplary and should not constitute any limitation on the present application.

[0077] The embodiments of the present application provide a secondary battery, comprising an electrode assembly, the electrode assembly comprising a first electrode sheet, a second electrode sheet and a separator, the separator being arranged between the first electrode sheet and the second electrode sheet, the first electrode sheet, the second electrode sheet and the separator being stacked and wound to form a wound structure, the first electrode sheet comprising a first tab, a first current collector and a first active material layer, along a width direction of the first electrode sheet, the first current collector comprising a first coating section and a first empty foil section at at least one end of the first coating section, the first active material layer being arranged on a first surface of the first coating section and / or a second surface of the first coating section. The first empty foil section refers to a part of the current collector at at least one end of the width direction of the first coating section without the first active material layer. The first empty foil section comprises a first part and a second part connected to the first coating section, the first part being folded towards the second part and stacked with the second part along a thickness direction of the first electrode sheet.

[0078] In the secondary battery described above, since the first coating section is the first empty foil section at at least one end along the width direction of the first electrode sheet, the first part overlaps with the second part, so that the two side edges of the first electrode sheet in the width direction are thickened. In the process of compression or charging and discharging, by increasing the thickness of the side edges of the first current collector in the width direction, the breaking strength of the first electrode sheet is increased, and the problem of breaking of the first current collector due to expansion force in the cycle process is improved.

[0079] Some embodiments of the present application will be described in detail below with reference to the accompanying drawings. The features in the following embodiments and examples can be combined with each other without conflict.

[0080] Please refer to Figure 1 and Figure 2 The embodiments of the present application provide a secondary battery 001, the secondary battery 001 comprising an electrode assembly 200 and a first tab 300, the first tab 300 being connected to the electrode assembly 200. The secondary battery 001 further comprises a second tab 400, the second tab 400 being connected to the electrode assembly 200, the polarities of the first tab 300 and the second tab 400 being different.

[0081] In an embodiment, the secondary battery 001 further comprises a housing 100, the housing 100 having a cavity 110, the electrode assembly 200 being arranged in the cavity 110 in the housing 100. Part of the first tab 300 extends out of the housing 100 and is used for electrical connection with an external structure. Part of the second tab 400 extends out of the housing 100 and is used for electrical connection with an external structure.

[0082] In another embodiment, a first tab 300 is connected to a conductive first adapter (not shown), the first adapter extending out of the housing 100 and used for electrical connection with an external structure. A second tab 400 is connected to a conductive second adapter (not shown), the second adapter extending out of the housing 100 and used for electrical connection with an external structure.

[0083] In one embodiment, the housing 100 includes at least one of a steel housing, a resin housing, or an aluminum-plastic film. For example, when the secondary battery 001 is a square hard-shell battery, the housing 100 includes a steel housing or a resin housing, and when the secondary battery 001 is a soft-pack battery, the housing 100 includes an aluminum-plastic film.

[0084] Please see Figure 3 and Figure 4 In one embodiment, the electrode assembly 200 includes a first electrode 210, a second electrode 220, and a diaphragm 230. The diaphragm 230 is disposed between the first electrode 210 and the second electrode 220. The first electrode 210, the second electrode 220, and the diaphragm 230 are stacked and wound to form a wound structure.

[0085] In one embodiment, the outermost electrode of the electrode assembly 200 is a first electrode 210.

[0086] In another embodiment, the outermost electrode of the electrode assembly 200 is a second electrode 220.

[0087] In one embodiment, the first electrode 210 is the positive electrode.

[0088] In another embodiment, the first electrode 210 is the negative electrode.

[0089] In one embodiment, the first electrode 210 includes a first current collector 211 and a first active material layer 212. Along the thickness direction of the first current collector 211, the first current collector 211 has two opposing surfaces, namely a first surface 2111 and a second surface 2112. The first active material layer 212 is disposed on the first surface 2111 and / or the second surface 2112.

[0090] Specifically, along the width direction of the first electrode 210, the first current collector 211 includes a first coated section 2113 and a first empty foil section 2114 located at both ends of the first coated section 2113, and a first active material layer 212 is disposed on the first surface 2111 of the first coated section 2113.

[0091] In another embodiment, a first active material layer 212 is disposed on the second surface 2112 of the first coating section 2113.

[0092] In another embodiment, the first active material layer 212 is disposed on both the first surface 2111 and the second surface 2112 of the first coating section 2113.

[0093] In an embodiment, the first empty foil segment 2114 includes a first part 2114a and a second part 2114b connected with the first coating segment 2113, the first part 2114a is folded towards the second part 2114b and laminated with the second part 2114b along the thickness direction of the first tab 210. Please refer to Figure 3 or Figure 5 The first part 2114a and the second part 2114b are divided by the folding position, i.e. the dashed line in the figure. Since the first coating segment 2113 is provided with the first empty foil segment 2114 along at least one end of the width direction of the first tab 210, the first part 2114a overlaps with the second part 2114b, so that the thickness of at least one side of the first tab 210 in the width direction is increased. During the compression or charging and discharging process of the secondary battery 001, by increasing the thickness of the side of the first current collector 211 in the width direction, the fracture resistance of the first tab 210 is improved, and the problem of fracture of the first current collector 211 caused by the expansion force during the cycle process is improved.

[0094] In an embodiment, please refer to Figure 3 Both ends of the first tab 210 in the width direction are provided with the first empty foil segment 2114, so that the thickness of both sides of the first tab 210 in the width direction is increased. The fracture resistance of the first tab 210 is further improved.

[0095] Since the first coating segment 2113 is provided with the first empty foil segment 2114 along both ends of the first tab 210 in the width direction, for the convenience of description, the following describes the first empty foil segment 2114 of one end of the first coating segment 2113. It is worth noting that the size, folding direction and folding distance of the first empty foil segment 2114 of both ends of the first coating segment 2113 along the width direction of the first tab 210 can be the same or different, and other various corresponding changes and deformations can be made according to the technical concept of the present application, and all these changes and deformations should belong to the protection scope of the claims of the present application.

[0096] In an embodiment, the first tab 210, the second tab 220 and the separator 230 are laminated to form a winding layer, and the winding layer is wound to form a winding structure. In the same winding layer, the first part 2114a is closer to the winding center of the electrode assembly 200 than the second part 2114b. That is, the first active material layer 212 on the first surface 2111 of the first coating segment 2113 faces the winding center of the electrode assembly 200, and the first part 2114a is folded towards the first active material layer 212 on the first surface 2111 of the first coating segment 2113, so that after the winding layer is wound, the first part 2114a is located on the inner side of the winding structure compared with the second part 2114b, which improves the problem of rebound after the first part 2114a is folded, and is conducive to improving the stability of the lamination of the first part 2114a and the second part 2114b.

[0097] In another embodiment, the first part 2114a is farther from the winding center of the electrode assembly 200 than the second part 2114b in the same winding layer. That is, the first active material layer 212 on the second surface 2112 of the first coating section 2113 is farther from the winding center of the electrode assembly 200, and the first part 2114a is bent toward the first active material layer 212 on the second surface 2112 of the first coating section 2113.

[0098] In an embodiment, along the width direction of the first tab 210, the width of the first part 2114a is L1, the width of the second part 2114b is L2, and 0≤L2-L1≤0.4mm, so that after the first part 2114a and the second part 2114b are laminated, the space occupied in the width direction of the first tab 210 is minimized, which is conducive to improving the energy density of the secondary battery 001, and the overlapping area of the first part 2114a and the second part 2114b is relatively large, which can further enhance the anti-fracture strength of the edge of the first tab 210. At the same time, the widths of the first part 2114a and the second part 2114b are equal, and the first part 2114a has sufficient bending length, which improves the bending convenience of the first part 2114a. Compared with the case where the width of the first part 2114a is greater than the width of the second part 2114b, the occupation of the first active material layer 212 in the first coating section 2113 by the first empty foil section 2114 can be reduced, and thus the influence of the first empty foil section 2114 on the energy density of the secondary battery 001 can be reduced.

[0099] In an embodiment, the first tab 210 further comprises an adhesive 213, the adhesive 213 is arranged on the first surface 2111 of the first empty foil section 2114, and the adhesive 213 is arranged between the first part 2114a and the second part 2114b and bonds the first part 2114a and the second part 2114b to fix the relative positions of the first part 2114a and the second part 2114b, which is conducive to improving the stability of the lamination of the first part 2114a and the second part 2114b and improving the problem of the first part 2114a rebounding after bending.

[0100] In an embodiment, the adhesive 213 is arranged on the first surface 2111 of the first part 2114a, and both surfaces of the adhesive 213 have adhesion, and after the first part 2114a and the second part 2114b overlap, the adhesive 213 bonds the first part 2114a and the second part 2114b to fix the relative positions of the first part 2114a and the second part 2114b.

[0101] In another embodiment, the adhesive 213 is disposed on the first surface 2111 of the second part 2114b, and both surfaces of the adhesive 213 are adhesive. After the first part 2114a and the second part 2114b are overlapped, the adhesive 213 bonds the first part 2114a and the second part 2114b to fix the relative position of the first part 2114a and the second part 2114b.

[0102] In yet another embodiment, the adhesive 213 is disposed on the first surface 2111 of the first part 2114a and the first surface 2111 of the second part 2114b. After the first part 2114a and the second part 2114b are overlapped, the adhesive 213 on the first surface 2111 of the first part 2114a and the adhesive 213 on the first surface 2111 of the second part 2114b are bonded, thereby improving the bonding strength.

[0103] In an embodiment, the adhesive 213 is single-sided adhesive tape.

[0104] In an embodiment, the adhesive 213 is double-sided adhesive tape.

[0105] In an embodiment, the adhesive 213 is hot melt adhesive.

[0106] In an embodiment, the melting temperature of the hot melt adhesive is T, and 45℃≤T≤65℃.

[0107] In an embodiment, the material of the adhesive 213 includes at least one of polyamide, reactive polyurethane, or polyether sulfone.

[0108] In an embodiment, the first tab 210 further includes an insulating member 214 disposed on the second surface 2112 of the first empty foil segment 2114. The insulating member 214 attached to the second surface 2112 of the first empty foil segment 2114 serves as a protective isolation.

[0109] In an embodiment, along the width direction of the first tab 210, the projection of the insulating member 214 is within the projection range of the first active material layer 212, i.e., along the thickness direction of the first tab 210, the insulating member 214 does not exceed the first active material layer 212, thereby not affecting the thickness of the entire electrode assembly 200, and being conducive to maintaining the energy density of the electrode assembly 200.

[0110] Please refer to Figure 3 and Figure 4 In an embodiment, the second tab 220 includes a second current collector 221 and a second active material layer 222, and the second active material layer 222 is disposed on at least one surface of the second current collector 221. Along the width direction of the first tab 210, the single-side width of the second tab 222 beyond the first active material layer 212 is Δd, and 0.2mm≤Δd≤1.4mm.

[0111] In an embodiment, along the width direction of the first pole piece 210, the width of the first empty foil segment 2114 is W1, 0.2mm≤W1≤1.4mm, and W1<Δd. That is, the width of the first empty foil segment 2114 after the first part 2114a and the second part 2114b are laminated is between 0.2mm and 1.4mm, and the width of the first empty foil segment 2114 in the width direction of the first pole piece 210 does not exceed the second pole piece 220, so as not to affect the size of the entire electrode assembly 200 in the width direction of the first pole piece 210, and to facilitate maintaining the energy density of the electrode assembly 200.

[0112] In an embodiment, along the thickness direction of the first pole piece 210, the maximum distance between the insulating member 214 on the first part 2114a and the insulating member 214 on the second part 2114b is H1, 31um≤H1≤100um. Wherein, the insulating member 214 on the first part 2114a and the insulating member 214 on the second part 2114b at least contain one layer of adhesive member 213 and the first part 2114a and the second part 2114b.

[0113] In an embodiment, along the thickness direction of the first pole piece 210, the thickness of the thickest part of the adhesive member 213 is H2, 5um≤H2≤20um.

[0114] In an embodiment, along the width direction of the first pole piece 210, the width of the adhesive member 213 is equal to the overlapping width of the first part 2114a and the second part 2114b. It should be noted that due to the influence of manufacturing errors, the difference between the width of the adhesive member 213 and the overlapping width of the first part 2114a and the second part 2114b is greater than or equal to -5% and less than or equal to 5% of the overlapping width of the first part 2114a and the second part 2114b. The case is considered as the width of the adhesive member 213 is equal to the overlapping width of the first part 2114a and the second part 2114b.

[0115] In an embodiment, along the bending direction of the first empty foil segment 2114, the thickness of one layer of insulating member 214 is H3, 5um≤H3≤20um.

[0116] In an embodiment, the material of the insulating member includes a ceramic material.

[0117] In an embodiment, the ceramic material includes at least one of aluminum oxide, magnesium oxide, silicon nitride, silicon carbide, and boehmite.

[0118] In an embodiment, the secondary battery 001 further comprises a first tab 300, and the first current collector 211 further comprises a connecting portion 2115, and the first tab 300 is welded to the connecting portion 2115. The connecting portion 2115 facilitates welding of the first tab 300, and the connecting portion 2115 is free of an active material layer, and the connecting portion 2115 can be located at a head portion of the first tab 210 or at a middle portion of the first tab 210.

[0119] Referring to Figure 5 In other embodiments, the secondary battery 001 further comprises a plurality of first tabs 300, each of the first tabs 300 is connected to the first portion 2114a and is integrally arranged with the first portion 2114a, and the first tab 300 comprises a bending portion 310 connected to the first portion 2114a and a lead-out portion 320 extending along a width direction of the first tab 210. After the bending portion 310 is bent together with the first portion 2114a, the root strength of the plurality of first tabs 300 is strengthened, and at the same time, the stress concentration at the root of the first tab 300 is eliminated by folding the insulating member 214, thereby improving the problem of root fracture of the first tab caused by expansion and stress concentration at the root of the first tab of the multi-tab battery cell.

[0120] Referring to Figure 6 An embodiment of the present application further provides a power consumption device 002 comprising the secondary battery 001 in one or more of the above embodiments.

[0121] An embodiment of the present application further provides a preparation method of a secondary battery 001 for preparing the secondary battery 001 in one or more of the above embodiments, comprising the following steps:

[0122] S1. providing a first current collector 211: Referring to Figure 7 dividing the first current collector 211 into a first coating section 2113 and a first unfolded empty foil section located at at least one end of the first coating section 2113 along a width direction of the first current collector 211, and arranging a first active material layer 212 on a first surface 2111 of the first coating section 2113 and / or a second surface 2112 of the first coating section 2113. The first active material layer 212 can be prepared by narrow slot coating, spraying, spin coating, gravure printing, etc., or a film of the first active material layer 212 can be prepared by dry method, and then the first active material layer 212 is assembled with the first current collector 211.

[0123] In an embodiment, the first unfolded empty foil section has a width W2, and 0.4mm≤W2≤2.8mm.

[0124] S2. Setting the adhesive 213: The adhesive 213 is set on the first surface 2111 of the first part 2114a and / or the first surface 2111 of the second part 2114b. After the folding, the first surface 2111 of the first part 2114a faces the first surface 2111 of the second part 2114b. In the width direction of the first current collector 211, the width of the adhesive 213 is equal to the width of the overlap of the first part 2114a and the second part 2114b.

[0125] S3. Folding: Please refer to Figure 7 and Figure 8 The first unfolded empty foil segment includes the first part 2114a and the second part 2114b connected with the first coated segment 2113. The first part 2114a is folded towards the second part 2114b, so that the first part 2114a and the second part 2114b are stacked in the thickness direction of the first pole piece 210, to obtain the first empty foil segment 2114.

[0126] In an embodiment, the adhesive 213 can be set on the first surface 2111 of the first part 2114a and / or the first surface 2111 of the second part 2114b, and the first unfolded empty foil segment can be folded before the first active material layer 212 is set on the first surface 2111 of the first coated segment 2113 and / or the second surface 2112 of the first coated segment 2113. In an embodiment, in the width direction of the first current collector 211, the width of the first part 2114a is L1, and the width of the second part 2114b is L2, L1=L2. In another embodiment, L1>L2. In yet another embodiment, L1

[0127] In an embodiment, after the first part 2114a and the second part 2114b are stacked in the thickness direction of the first pole piece 210 and the adhesive 213 is set, the folding area is hot-pressed. The hot-pressing temperature is 45-65°C, and the hot-pressing time is 3-6s.

[0128] S4. Setting the insulating member 214: The insulating member 214 is set on the second surface 2112 of the first part 2114a and the second surface 2112 of the second part 2114b.

[0129] Step S4 can be set before step S3 or after step S3. When step S4 can be set before step S3, it is beneficial to protect the second surface 2112 of the first current collector 211 by the insulating member 214.

[0130] In an embodiment, the folding direction of the first part 2114a is towards the center of the winding of the electrode assembly 200.

[0131] To verify the improvement effect of the laminated arrangement of the first part 2114a and the second part 2114b on the damage of the first tab 210, the following test was performed:

[0132] (1) Battery cycle test: 10 secondary batteries 001 were taken for each of the comparative example and the groups of examples, and each secondary battery 001 was placed in a 55°C environment for 30 minutes, and then subjected to charge and discharge in the following steps. Constant current charging to 4.2V at 2.5C, and then constant voltage charging to 0.5C; then constant current charging to 4.45V at 0.5C, and then constant voltage charging to 0.02C; standing for 5 minutes, discharging to 3V at 1C, standing for 5 minutes, which was one cycle. According to the above cycle steps, 1000 cycles were cycled and the cycle number when the cycle capacity retention rate of the comparative example and the examples suddenly dropped during the cycle test was recorded. After the cycle test, the secondary battery 001 was disassembled, and whether the first tab 210 was damaged was observed with the naked eye, the number of first tab 210 with tears or breaks was recorded, and the cycle test tab damage rate = (damaged tab number / 10) x 100%.

[0133] The specific implementation of the secondary battery 001 in the examples and the comparative example is described below.

[0134] Example 1:

[0135] A secondary battery 001 was assembled as follows:

[0136] (1) Preparation of anode tab: artificial graphite, conductive carbon black (Super P), and butadiene rubber (SBR) were mixed in a weight ratio of 96:1.5:2.5, deionized water was added as a solvent, and a slurry with a weight percentage of 70wt% was prepared and stirred uniformly. The slurry was uniformly coated on both surfaces of the anode current collector copper foil with a thickness of 8μm in the thickness direction. Drying at 110°C, an anode tab with a coating thickness of 150μm was obtained. The anode tab was prepared according to the above preparation method of the secondary battery 001, and the lug was welded in the middle of the anode tab.

[0137] (2) Preparation of the cathode electrode sheet: the cathode active material lithium cobaltate (LiCoO2), conductive carbon black (Super P), and polyvinylidene fluoride (PVDF) are mixed in a weight ratio of 97.5:1.0:1.5, N-methyl pyrrolidone (NMP) is added as a solvent, a slurry with a solid content of 75wt% is prepared, and the slurry is stirred uniformly. The slurry is uniformly coated on the two surfaces of the cathode current collector aluminum foil with a thickness of 12μm in the thickness direction to form a first coating section 2113, and the aluminum foil is reserved as an empty foil section at both ends in the width direction of the aluminum foil, and both ends of the first coating section 2113 are first uncoated empty foil sections in the width direction of the aluminum foil. The first uncoated empty foil section includes a first part 2114a and a second part 2114b connected to the first coating section 2113, and the width of the first part 2114a is L1 and the width of the second part 2114b is L2 in the width direction of the first current collector 211, L1=1.4mm, and L2=0.6mm.

[0138] Then, drying at 90℃, a cathode electrode sheet with a cathode active material layer thickness of 100μm is obtained. The first current collector 211 of the cathode electrode sheet further includes a connecting part 2115, which is located in the middle of the first current collector 211, and a cathode tab is welded on the connecting part 2115.

[0139] (3) Preparation of the electrolyte: in a dry argon atmosphere, first, ethylene carbonate (EC), methyl ethyl carbonate (EMC), and diethyl carbonate (DEC) are mixed in a mass ratio of EC:EMC:DEC=30:50:20 to form a base organic solvent, then lithium salt lithium hexafluorophosphate (LiPF6) is added to the base organic solvent to dissolve and mix uniformly to obtain an electrolyte with a lithium salt concentration of 1.15mol / L.

[0140] (4) Preparation of the separator film: a separator film with a three-layer structure is used, which includes a first adhesive layer, a first substrate layer, and a second adhesive layer stacked. The first substrate layer is made of polyethylene (PE), and the first adhesive layer and the second adhesive layer each contain a first adhesive and boehmite.

[0141] (5) Preparation of the electrode assembly 200: the cathode electrode sheet, the separator film, and the anode electrode sheet are stacked, and the structure obtained after stacking is wound. The electrode sheet of the outermost circle of the wound structure is the cathode electrode sheet, and the cathode tab is connected to the first empty foil section 2114 of the cathode electrode sheet.

[0142] (6) Assembly of the electrode assembly 200: the punched aluminum plastic film is placed in the assembly jig with the pit surface facing up, the electrode assembly 200 is placed in the pit, and an external force is applied to compress it. Then, another punched aluminum plastic film with the pit surface facing down is placed on the electrode assembly 200, and the four sides of the two aluminum plastic films are heat-sealed in a hot-pressing manner to obtain the assembled electrode assembly 200.

[0143] (7) Liquid injection packaging: electrolyte is injected into the assembled electrode assembly 200, and the secondary battery 001 is obtained through the processes of vacuum packaging, standing, heat pressing formation, shaping, etc.

[0144] Example 2: The difference from Example 1 is that, along the width direction of the first current collector 211, the width of the first part 2114a is L1, and the width of the second part 2114b is L2, L1 = 1.2 mm, and L2 = 0.8 mm.

[0145] Example 3: The difference from Example 1 is that, along the width direction of the first current collector 211, the width of the first part 2114a is L1, and the width of the second part 2114b is L2, L1 = 1.0 mm, and L2 = 1.0 mm.

[0146] Example 4: An empty foil area is reserved at one end of the aluminum foil in the width direction of the aluminum foil. Along the width direction of the aluminum foil, one end of the first coating section 2113 is a first expanded empty foil section. The first expanded empty foil section includes a first part 2114a and a second part 2114b connected to the first coating section 2113. Along the width direction of the first current collector 211, the width of the first part 2114a is L1, and the width of the second part 2114b is L2, L1 = 1.4 mm, and L2 = 0.6 mm.

[0147] Comparative Example 1: The difference from Example 1 is that, in Comparative Example 1, along the width direction of the first tab 210, the first current collector 211 only includes the first coating section 2113. A connecting groove is opened in the first coating section 2113 to expose a part of the first current collector 211 below the connecting groove. The first lug 300 is welded to the part of the first current collector 211 exposed by the connecting groove. The position of the connecting groove is the same as that of the connecting part 2115 in Example 1. The remaining steps are the same as those in Example 1.

[0148] The main parameter control and test results of each example and comparative example are shown in Table 1:

[0149] Table 1

[0150]

[0151] Note: " / " represents that the secondary battery 001 does not have a sudden drop in cycle capacity within 1000 cycles.

[0152] According to the above Table 1 and in combination with Figure 3It can be seen that in Comparative Example 1, the cycle capacity retention of the first tab 210 sharply decreases after a certain number of charge cycles (398 cycles). In Examples 1 to 3, the first part 2114a overlaps with the second part 2114b, so that the first tab 210 is thickened on both sides in the width direction of the first tab 210. During the battery cycle test, by increasing the thickness of the side edges of the first current collector 211 in the width direction, the average cycle number before cycle sharp drop of the secondary battery 001 is significantly improved, and the edge fracture of the first tab 210 is significantly reduced, achieving the effect of increasing the fracture resistance of the first tab 210, which is beneficial to the problem of fracture of the first current collector 211 during the cycle process.

[0153] According to Table 1 above, compared with Example 3, in Example 1, the width of the first part 2114a is 0.8 mm greater than the width of the second part 2114b along the width direction of the first tab 210. Although the secondary battery 001 can pass the battery cycle test, the first part 2114a has a slight impact on the fracture resistance of the first tab 210 due to the partial overlap between the first part 2114a and the first active material layer 212 after folding.

[0154] According to Table 1 above, compared with Example 3, in Example 2, the width of the first part 2114a is 0.4 mm greater than the width of the second part 2114b along the width direction of the first tab 210. Although the secondary battery 001 can pass the battery cycle test, the first part 2114a has a slight impact on the fracture resistance of the first tab 210 due to the partial overlap between the first part 2114a and the first active material layer 212 after folding.

[0155] Compared with Example 1, in Example 2, the width difference between the first part 2114a and the second part 2114b along the width direction of the first tab 210 is reduced, the average cycle number before cycle sharp drop of the secondary battery 001 is slightly improved, and the tab damage rate of the secondary battery 001 during the cycle test is slightly reduced. Therefore, under the condition that the average overlap width of the first part 2114a and the second part 2114b is the same, the smaller the difference in overlap width between the first part 2114a and the second part 2114b, the larger the overlap area, and the higher the fracture resistance of the first tab 210.

[0156] Compared with Comparative Example 1, Example 4 sets the first empty foil section 2114 on one side of the first tab 210, which improves the cycle life of the secondary battery 001 and reduces the tab damage rate. However, compared with Example 1 in which the first empty foil section 2114 is arranged on both sides of the first tab 210, the cycle life of the secondary battery 001 in Example 4 is lower, and the tab damage rate is higher. This indicates that arranging the first empty foil section 2114 on one side of the first tab 210 can achieve a certain effect of reducing tab fracture, but arranging the first empty foil section 2114 on both sides of the first tab 210 will achieve a better effect.

[0157] In addition, for those skilled in the art, other various corresponding changes and modifications can be made according to the technical concept of the present application, and all these changes and modifications shall belong to the protection scope of the claims of the present application.

Claims

1. A secondary battery, comprising an electrode assembly, the electrode assembly including a first electrode, a second electrode, and a separator, the separator being disposed between the first electrode and the second electrode, the first electrode, the second electrode, and the separator being stacked and wound to form a wound structure, characterized in that, The first electrode includes: First pole ear; A first current collector, along the width direction of the first electrode, includes a first coated section and a first empty foil section located at at least one end of the first coated section; and A first active material layer is disposed on the first surface of the first coating section and / or the second surface of the first coating section along the thickness direction of the first electrode sheet. The first empty foil segment includes a first part and a second part connected to the first coated segment. The first part is connected to the second part and is stacked with the second part along the thickness direction of the first electrode sheet.

2. The secondary battery as described in claim 1, characterized in that, Within the same winding layer, the first portion is closer to the winding center of the electrode assembly than the second portion.

3. The secondary battery as described in claim 1, characterized in that, Along the width direction of the first electrode, the width of the first part is L1, the width of the second part is L2, and 0≤L2-L1≤0.4mm.

4. The secondary battery as described in claim 1, characterized in that, The first electrode also includes an adhesive member disposed on the first surface of the first empty foil segment, and in the thickness direction of the first electrode, the adhesive member is bonded between the first part and the second part.

5. The secondary battery as described in claim 4, characterized in that, The adhesive is a single-sided adhesive, double-sided adhesive, or hot melt adhesive.

6. The secondary battery as described in claim 5, characterized in that, The adhesive is a hot melt adhesive, and the material of the adhesive includes at least one of polyamide, reactive polyurethane, or polyethersulfone.

7. The secondary battery as described in claim 5, characterized in that, The melting temperature of the hot melt adhesive is T, where 45℃≤T≤65℃.

8. The secondary battery as described in claim 4, characterized in that, The thickness of the thickest part of the adhesive component is H2, 5um ≤ H2 ≤ 20um; and / or Along the width direction of the first electrode, the width of the adhesive is equal to the overlap width of the first part and the second part.

9. The secondary battery as described in claim 1, characterized in that, The first electrode also includes an insulating element disposed on the second surface of the first empty foil segment.

10. The secondary battery as described in claim 9, characterized in that, The insulating component is made of ceramic material.

11. The secondary battery as described in claim 10, characterized in that, The ceramic material includes at least one of alumina, magnesium oxide, silicon nitride, silicon carbide, and boehmite.

12. The secondary battery as described in claim 9, characterized in that, Along the width direction of the first electrode, the projection of the insulating element lies within the projection of the first active material layer.

13. The secondary battery as described in claim 9, characterized in that, Along the thickness direction of the first electrode, the projection of the insulating element lies within the projection of the second electrode.

14. The secondary battery as described in claim 13, characterized in that, Along the width direction of the first electrode, the width of the second electrode extending beyond the first active material layer on one side is Δd, where 0.2mm≤Δd≤1.4mm.

15. The secondary battery as described in claim 14, characterized in that, Along the width direction of the first electrode, the width of the orthographic projection of the first empty foil segment onto the thickness direction of the first electrode is W1, 0.2mm≤W1≤1.4mm.

16. The secondary battery as described in claim 12, characterized in that, Along the thickness direction of the first electrode, the maximum distance between the insulating element on the first part and the insulating element on the second part is H1, 31um≤H1≤100um.

17. The secondary battery as described in claim 12, characterized in that, The thickness of the insulating layer is H3, where 5um ≤ H3 ≤ 20um.

18. The secondary battery as described in claim 1, characterized in that, The first current collector also includes a connecting part, and the first electrode tab is welded to the connecting part.

19. The secondary battery as described in claim 1, characterized in that, Multiple first electrode tabs are provided, each of which is connected to and integrally formed with the first part. Each first electrode tab includes a bent portion connected to the first part and a lead-out portion extending along the width direction of the first electrode sheet.

20. The secondary battery according to any one of claims 1 to 19, characterized in that, The outermost electrode of the electrode assembly is the first electrode.

21. The secondary battery according to any one of claims 1 to 19, characterized in that, The first electrode is the positive electrode.

22. An electrical appliance, characterized in that, Includes the secondary battery as described in any one of claims 1 to 21.

23. A method for preparing a secondary battery, used to prepare the secondary battery as described in claim 1, characterized in that, Includes the following steps: A first current collector is provided, and along the width direction of the first current collector, the first current collector is divided into a first coating section and a first unfolded empty foil section located at at least one end of the first coating section. A first active material layer is provided on the first surface of the first coating section and / or the second surface of the first coating section. The first unfolded empty foil segment includes a first part and a second part connected to the first coated segment. The first part is bent toward the second part, so that the first part and the second part are stacked along the thickness direction of the first electrode to obtain the first empty foil segment.

24. The method for preparing a secondary battery as described in claim 23, characterized in that, The bending direction of the first part is toward the winding center of the electrode assembly.

25. The method for preparing a secondary battery as described in claim 23, characterized in that, Along the width direction of the first current collector, the widths of the first part and the second part are equal; the width of the first unfolded empty foil segment is W2, 0.4mm≤W2≤2.8mm.

26. The method for preparing a secondary battery as described in claim 23, characterized in that, The bending process also includes: An adhesive is provided on the first surface of the first part and / or the first surface of the second part; after bending, the first surface of the first part faces the first surface of the second part.

27. The method for preparing a secondary battery as described in claim 23, characterized in that, It also includes the following steps: Insulating elements are provided on the second surface of the first part and the second surface of the second part.

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