Secondary battery and electric device

Abstract

The invention provides a secondary battery and a power utilization device, the secondary battery comprises a laminated structure formed by laminating a negative pole piece, an isolating membrane and a positive pole piece, the negative pole piece and / or the positive pole piece comprises an active material region and bonding regions, and the bonding regions are located at two sides of the active material region along a first direction; in the second direction, the bonding area extends out relative to the active material area, and the isolating membrane extends out relative to the active material area; on one side in the second direction, the length of the extending part of the bonding region relative to the active material region is L, the extending length of the isolating membrane relative to the active material region is T, and L is greater than T; the first direction is perpendicular to the second direction; and the active material region of the negative pole piece comprises metal lithium. The secondary battery of the present application has excellent safety.

Description

Technical Field

[0001] The present application relates to the technical field of secondary batteries, and in particular to a secondary battery and an electrical device. Background Art

[0002] In recent years, secondary batteries have been widely used in energy storage systems such as hydropower, thermal, wind, and solar power plants, as well as in power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace, and other fields. With the application and promotion of secondary batteries, people have increasingly higher requirements for their energy density, cycle performance, and high-rate charging performance.

[0003] When secondary batteries use lithium metal negative electrodes, they have the advantage of high energy density. However, as charging and discharging proceed, dead lithium will gradually form on the lithium metal negative electrode, and gradually become powdered and migrate, which can easily lead to safety problems such as micro-short circuits and overcharging. Summary of the Invention

[0004] The present application has been made in view of the above-mentioned problems, and an object thereof is to provide a secondary battery having excellent safety performance and an electric device using the secondary battery.

[0005] In order to achieve the above-mentioned purpose, the first aspect of the present application provides a secondary battery, including a stacked structure formed by stacking a negative electrode sheet, a separator and a positive electrode sheet, the negative electrode sheet and / or the positive electrode sheet including an active material area and a bonding area, the bonding area being located on both sides of the active material area along a first direction; in a second direction, the bonding area extends relative to the active material area, and the separator extends relative to the active material area; on one side in the second direction, the length of the extending portion of the bonding area relative to the active material area is L, and the extending length of the separator relative to the active material area is T, wherein L is greater than T; the first direction is perpendicular to the second direction; the active material area of ​​the negative electrode sheet includes metallic lithium.

[0006] In the present application, since the positive electrode sheet and / or negative electrode sheet of the secondary battery includes bonding areas located on both sides of the active material area along the first direction, the positive electrode sheet and / or negative electrode sheet can be fixed to the isolation membrane through the bonding areas, that is, a closed state is achieved between the positive electrode sheet and / or negative electrode sheet and the isolation membrane; on this basis, by setting the length L of the protruding portion of the bonding area relative to the active material area to be greater than the protruding length T of the isolation membrane relative to the active material area, the gap between the positive electrode sheet and / or negative electrode sheet and the isolation membrane can be effectively filled through the protruding portion, thereby avoiding the contact between the powdered metal lithium and the positive electrode sheet to the greatest extent, improving micro-short circuit and overcharging phenomena, and improving the safety performance of the secondary battery.

[0007] In some embodiments, on one side in the second direction, the extension portion includes a first extension portion and a second extension portion that are continuous along the second direction, the second extension portion being bent relative to the first extension portion and bonded to the surface of the first extension portion; the length of the first extension portion is L1, the length of the second extension portion is L2, then T=L1; L2<5mm-T, and L=L1+L2. In the present application, by making L1=T, the first extension portion can fill the gap between the positive electrode sheet and / or the negative electrode sheet and the separator. In addition, the present application provides a second extension portion, and the second extension portion is bent along with the separator during the lamination process, so that the extension portion can fully fill the entire gap between the positive electrode sheet and / or the negative electrode sheet and the separator, thereby improving the sealing effect between the positive electrode sheet and / or the negative electrode sheet and the separator, thereby improving the safety of the secondary battery.

[0008] In some embodiments, the electrode sheet has a tab on one side in the first direction, and the tab is located on a side of the bonding region away from the active material region.

[0009] In some embodiments, the negative electrode sheet includes the bonding area, and on one side in the second direction, the extension length of the separator relative to the active material area of ​​the negative electrode sheet is T 负 The length of the extension portion of the negative electrode is L 负 , the length of the first extension is L1 负 , the length of the second extension is L2 负 , where T 负 , L 负 、L1 负 、L2 负 Satisfy the following relationship: 2mm≤T 负 <5mm,L1 负 =T 负 ;0<L2 负 <3mm, and L 负 =L1 负 +L2 负 In the present application, by setting the negative electrode plate to include a bonding area, the fixation between the negative electrode plate and the separator can be achieved. On this basis, by setting the extension length T of the separator relative to the active material area of ​​the negative electrode plate 负 , the length L1 of the first extension of the negative electrode sheet 负 , the length L2 of the second extension of the negative electrode sheet 负 Satisfying the above relationship can effectively fill all gaps between the negative electrode sheet and the separator through the first extension while preventing the second extension from bending to the active material area of ​​the negative electrode sheet, which is more conducive to improving the safety performance of the secondary battery.

[0010] In some embodiments, the dimension W of the bonding area in the negative electrode sheet along the first direction is 负 Meet: 4mm≤W 负 ≤[(W1-W2) / 2]; where W1 is the dimension of the separator along the first direction, and W2 is the dimension of the active material area of ​​the negative electrode plate along the first direction. In this application, the dimension of the bonding area of ​​the negative electrode plate falls within the above range to ensure both safety and capacity of the secondary battery.

[0011] In some embodiments, 4 mm ≤ W 负 ≤6mm. This is more conducive to balancing the safety performance and capacity of secondary batteries.

[0012] In some embodiments, the positive electrode sheet includes the bonding area, and on one side in the second direction, the protruding length of the separator relative to the active material area of ​​the positive electrode sheet is T 正 , the length L of the protruding portion of the positive electrode sheet 正 , the length of the first extension is L1 正 , the length of the second extension is L2 正 , where T 正 , L 正 、L1 正 、L2 正 Satisfy the following relationship: 3.5mm≤T 正 ≤5mm, T 正 =L1 正 ;0<L2 正 ≤1.5mm, and L 正 =L1 正 +L2 正 In this application, by setting the positive electrode sheet to include a bonding area, the fixation between the positive electrode sheet and the separator can be achieved. On this basis, by setting the extension length T of the separator relative to the active material area of ​​the positive electrode sheet 正 , the length of the protruding part of the positive electrode sheet L 正 The length L1 of the first extension of the positive electrode 正 , the length L2 of the second extension of the positive electrode sheet 正 Satisfying the above relationship can effectively fill the gap between the positive electrode sheet and the separator while preventing the second extension from bending to the active material area of ​​the positive electrode sheet, which is more conducive to improving the safety performance of the secondary battery.

[0013] In some embodiments, 3.5 mm ≤ L1 正 ≤5mm, L2 正 ≤1.5mm. This helps to improve the safety performance of secondary batteries.

[0014] In some embodiments, an insulating region is provided between the bonding region and the active material region in the positive electrode sheet. The insulating region effectively prevents short circuits between the positive and negative electrode sheets, thereby avoiding short circuits and overheating within the battery, reducing the risk of battery combustion or explosion, and improving battery safety.

[0015] In some embodiments, the dimension W of the bonding area in the positive electrode sheet along the first direction is 正 Meet: 3mm≤W 正 ≤[(W1-W3-W4) / 2]; where W2 is the dimension of the separator along the first direction, W3 is the dimension of the active material region of the positive electrode sheet along the first direction, and W4 is the dimension of the insulating region along the first direction. In this application, the dimension of the bonding region of the positive electrode sheet along the first direction falls within the above range to ensure both safety and capacity of the secondary battery.

[0016] In some embodiments, 3 mm ≤ W 正 ≤5mm. This helps to improve the safety performance of secondary batteries.

[0017] A second aspect of the present application provides an electrical device comprising the secondary battery of the first aspect of the present application.

[0018] The electric device of the present application includes the secondary battery provided by the present application, and thus has at least the same advantages as the secondary battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a schematic structural diagram of the negative electrode sheet provided in one embodiment of the present application.

[0020] Figure 2 This is a schematic structural diagram of the positive electrode sheet provided in one embodiment of the present application.

[0021] Figure 3 Schematic diagram of a battery cell according to one embodiment of the present application.

[0022] Figure 4 yes Figure 3 FIG. 1 is an exploded view of a battery cell according to an embodiment of the present application.

[0023] Figure 5 Schematic diagram of a battery module according to one embodiment of the present application.

[0024] Figure 6 Schematic diagram of a battery pack according to one embodiment of the present application.

[0025] Figure 7 yes Figure 6 An exploded view of a battery pack according to an embodiment of the present application is shown.

[0026] Figure 8 FIG. 1 is a schematic diagram of an electrical device using a secondary battery according to an embodiment of the present application as a power source.

[0027] Description of reference numerals:

[0028] 1 battery pack; 2 upper box; 3 lower box; 4 battery module; 5 battery cell; 51 shell; 52 electrode assembly; 53 top cover assembly. DETAILED DESCRIPTION

[0029] Below, the embodiments of the secondary battery and the electrical device of the present application are described in detail with appropriate reference to the accompanying drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there may be cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structure 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 drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0030] " range " disclosed in the present application is limited in the form of lower limit and upper limit, and given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of special range. The scope limited in this way can be to include end value or not include end value, and can be arbitrarily combined, that is, any lower limit can form a range with any upper limit combination. For example, if the scope of 60-120 and 80-110 is listed for specific parameters, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range value 1 and 2 are listed, and if the maximum range value 3,4 and 5 are listed, then the following range can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In this application, unless otherwise specified, the numerical range " ab " represents the abbreviation of any real number combination between a and b, wherein a and b are all real numbers. For example, a numerical range of "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is simply an abbreviation for these numerical combinations. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0031] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0032] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0033] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), indicating that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0034] Unless otherwise specified, the terms used in this application have the common meanings generally understood by those skilled in the art.

[0035] Unless otherwise specified, the values ​​of the parameters mentioned in this application can be measured using various test methods commonly used in the art, for example, they can be measured according to the test methods given in this application.

[0036] The term "secondary battery" referred to herein refers to a battery cell, a battery module, or a battery pack.

[0037] Typically, a secondary battery cell includes a positive electrode sheet, a negative electrode sheet, an electrolyte, and a separator.

[0038] During the battery's charge and discharge processes, active ions are embedded in and extracted from the positive and negative electrodes. The electrolyte conducts ions between the positive and negative electrodes. A separator, located between the positive and negative electrodes, prevents short circuits while allowing ions to pass through.

[0039] In the development of battery technology, in addition to improving battery performance, safety issues are also a concern that cannot be ignored. In the field of laminated battery production technology, the preparation of laminated cells is mainly carried out by laminating using a laminating machine. The general process is as follows: the positive and negative electrode sheets are alternately fed to a reciprocating laminating table, the separator is unwound in a Z-shape to separate the positive and negative electrode sheets, the separator is cut, and the adhesive is applied to complete the preparation of the laminated bare cell. The positive and negative electrode sheets of the laminated battery are staggered. The conventional Z-shaped anode-cathode lamination design used in lithium metal secondary batteries will cause the following problems in the actual operation of lithium metal batteries due to the generation of pulverized dead lithium: the separator on both sides of the electrode tab is open. In the late stage of the lithium metal cycle, the pulverized lithium can overflow to the overhand between the separator and the negative electrode sheet, and even to the positive electrode sheet, which can easily lead to contact short circuits between the positive and negative electrode sheets, overcharging, and further causing battery fires or even explosions, posing a significant safety risk.

[0040] In view of this, the first aspect of the present application provides a secondary battery, comprising a stacked structure formed by stacking a negative electrode sheet, a separator and a positive electrode sheet, the negative electrode sheet and / or the positive electrode sheet comprising an active material area and a bonding area, the bonding area being located on both sides of the active material area along a first direction; in a second direction, the bonding area extends relative to the active material area, and the separator extends relative to the active material area; on one side in the second direction, the length of the extending portion of the bonding area relative to the active material area is L, and the extending length of the separator relative to the active material area is T, wherein L is greater than T; the first direction is perpendicular to the second direction; the active material area of ​​the negative electrode sheet comprises metallic lithium.

[0041] In response to the problems of short circuit, overcharging, etc. caused by the overflow of pulverized lithium in the late stage of the cycle of lithium metal secondary batteries, the present application provides the positive electrode sheet and / or negative electrode sheet of the secondary battery including bonding areas located on both sides of the active material area along the first direction, and the bonding areas have a binder. In this way, the positive electrode sheet and / or negative electrode sheet can be fixed to the isolation membrane through the bonding areas, that is, the positive electrode sheet and / or negative electrode sheet and the isolation membrane are set to a closed state; on this basis, by setting the length L of the extension of the bonding area relative to the active material area to be greater than the extension length T of the isolation membrane relative to the active material area, the gap between the positive electrode sheet and / or negative electrode sheet and the isolation membrane can be effectively filled through the extension, thereby avoiding the contact between the pulverized metal lithium and the positive electrode sheet to the greatest extent, improving the short circuit and overcharging phenomena of the secondary battery, and improving the safety performance of the secondary battery.

[0042] In some embodiments, the first direction may be the width (or length) direction of the negative electrode sheet, and the second direction may be the length (or width) direction of the negative electrode sheet.

[0043] In some embodiments, the active material region of the positive and / or negative electrode sheets is provided with an active material, and the bonding region of the positive and / or negative electrode sheets is provided with a binder. The binder needs to have excellent adhesion and electrolyte resistance and be stable in the secondary battery. For example, the binder may include polypropylene and a tackifying resin α-copolymer.

[0044] In some embodiments, there is an overhand gap between the edge of the active material area of ​​the negative electrode plate and the isolation membrane. If there is no overhand at the edge of the active material area of ​​the negative electrode plate, the lithium edges will be squeezed and accumulated together during the expansion of the secondary battery, which can easily puncture the isolation membrane and cause safety problems.

[0045] In some embodiments, the bonding area has two protruding portions extending from the active material area along the second direction, that is, the positive electrode sheet and / or the negative electrode sheet in the present application is in an "I-shape" (excluding the tabs).

[0046] In some embodiments, on one side in the second direction, the extension portion includes a first extension portion and a second extension portion continuous along the second direction, the second extension portion is bent relative to the first extension portion and bonded to the surface of the first extension portion; the length of the first extension portion is L1, the length of the second extension portion is L2, then T=L1; 0<L2<5mm-T, and L=L1+L2.

[0047] It should be noted that in the present application, the first extension portion of the positive electrode sheet and / or the negative electrode sheet is in the same plane as the electrode body, and the second extension portion is bent relative to the positive electrode sheet and / or the negative electrode sheet along with the isolation membrane during the lamination process, and covers the surface of the first extension portion, and is subsequently bonded and fixed to the first extension portion.

[0048] In the present application, the first extension is used to fill the gap between the positive electrode sheet and / or the negative electrode sheet and the separator. Therefore, the length L1 of the first extension is set to be equal to the extension length T of the separator relative to the active material area. In addition, during the lamination process, the electrode sheet sometimes moves so that the first extension fails to completely fill the above-mentioned gap. In the present application, a second extension is provided, and the second extension is bent along with the separator during the lamination. In this way, the extensions (the first extension and the second extension) can fully fill the entire gap between the positive electrode sheet and / or the negative electrode sheet and the separator, thereby improving the sealing effect between the positive electrode sheet and / or the negative electrode sheet and the separator, thereby improving the safety of the secondary battery.

[0049] In the present application, by setting the length L2 of the second extension portion to satisfy the above relationship, on the one hand, the first extension portion can completely fill the overhand gap between the isolation membrane and the active material area, and on the other hand, it can avoid the second extension portion from bending to the active material area of ​​the positive electrode sheet and / or the negative electrode sheet, which is more helpful to improve the safety performance of the secondary battery.

[0050] In some embodiments, the electrode sheet has a tab on one side in the first direction, and the tab is located on a side of the bonding region away from the active material region.

[0051] It should be noted that the tab of the positive electrode sheet and the tab of the negative electrode sheet are located on different sides of the electrode sheet in the first direction, or the tab of the positive electrode sheet and the tab of the negative electrode sheet are located on the same side of the electrode sheet in the first direction. When the tab of the positive electrode sheet and the tab of the negative electrode sheet are located on the same side of the electrode sheet in the first direction, after lamination, the tab of the positive electrode sheet and the tab of the negative electrode sheet are respectively located on different sides of the electrode sheet in the second direction.

[0052] Figure 1 A schematic diagram of the structure of a negative electrode sheet is shown in FIG. Figure 1 As shown, the negative electrode sheet 10 includes a bonding area 101 and an active material area 102. On one side in the second direction, the extension length of the separator 20 relative to the active material area 102 of the negative electrode sheet 10 is T 负 The length of the extended portion of the negative electrode sheet 10 is L 负 , the length of the first extension is L1 负 , the length of the second extension is L2 负 , where T 负 , L 负 、L1 负 、L2 负 Satisfy the following relationship: 2mm≤T 负 <5mm,L1 负 =T 负 ;0<L2 负 <3mm, and L 负 =L1 负 +L2 负 .

[0053] In the present application, by setting the negative electrode sheet to include a bonding area, the fixation between the negative electrode sheet and the separator can be achieved. On this basis, by setting the extension length T of the separator relative to the active material area of ​​the negative electrode sheet 负 , the length L1 of the first extension of the negative electrode sheet 负 , the length L2 of the second extension of the negative electrode sheet 负 Satisfying the above relationship can effectively fill the gap between the negative electrode sheet and the separator while preventing the second extension from bending to the active material area of ​​the negative electrode sheet, which is more conducive to improving the safety performance of the secondary battery.

[0054] In some embodiments, 2 mm ≤ L 负 ≤4mm.

[0055] In some embodiments, the dimension W of the bonding area in the negative electrode sheet along the first direction is 负 Meet: 4mm≤W 负 ≤[(W1-W2) / 2]; wherein W1 is the size of the isolation membrane along the first direction, and W2 is the size of the active material area of ​​the negative electrode sheet along the first direction.

[0056] In the present application, the design of the bonding area 101 needs to be as narrow as possible, not occupying too large an area of ​​the negative electrode plate, and not affecting the overall structure, that is, not affecting the capacity and not causing the negative electrode plate to exceed the isolation membrane. At the same time, it is also necessary to meet the integrity and mechanical tensile properties of the bonding area 101 during the expansion of the secondary battery, so as to limit the pulverization of dead lithium without affecting the secondary battery structure and its own effectiveness.

[0057] In the present application, the size of the bonding area in the negative electrode sheet along the first direction meets the above range, which can take into account both the safety performance and the capacity of the secondary battery.

[0058] In some embodiments, 4 mm ≤ W 负 ≤6mm. This is more conducive to balancing the safety performance and capacity of secondary batteries.

[0059] At present, since there are overhands on both the left and right sides of the isolation membrane and the negative electrode sheet, the negative electrode sheet in the laminated battery cell is prone to sliding and dislocation, which requires the laminated battery cell to be fixed with glue, and the glue will squeeze the overhand. This will also cause local overvoltage in the battery performance test, causing local etching of the lithium negative electrode, thereby causing capacity decay. In this application, the negative electrode sheet can be fixed by providing a bonding area on the negative electrode sheet, and the positive electrode sheet can be bonded to the isolation membrane during the hot pressing process. In this way, the glue coating process can be eliminated, and the local etching of the lithium negative electrode can be improved, thereby reducing capacity decay. In addition, the laminated battery cell manufacturing process can be simplified to save costs.

[0060] In some embodiments, when the negative electrode plate includes a bonding area, the positive electrode plate may or may not include the bonding area.

[0061] In some embodiments, the negative electrode sheet can be obtained by: 1) forming an active material area on the current collector; 2) brushing glue on both sides of the active material area along the first direction to form a bonding area; 3) using a special die to punch out the above-mentioned "I-shaped" negative electrode sheet.

[0062] Figure 2 A schematic diagram of the structure of a positive electrode sheet is shown in FIG. Figure 2 As shown, the positive electrode sheet 30 includes a bonding area 301 and an active material area 302. On one side in the second direction, the protruding length of the separator 20 relative to the active material area 302 of the positive electrode sheet is T 正 , the length L of the protruding portion of the positive electrode sheet 30 正 , the length of the first extension is L1 正 , the length of the second extension is L2 正 , where T 正 , L 正 、L1 正 、L2 正 Satisfy the following relationship: 3.5mm≤T 正 ≤5mm, L1 正 =T 正 ,0<L2 正 ≤1.5mm, and L 正 =L1 正 +L2 正 .

[0063] In the present application, by setting the positive electrode sheet to include a bonding area, the fixation between the positive electrode sheet and the separator can be achieved. On this basis, by setting the extension length T of the separator relative to the active material area of ​​the positive electrode sheet 正 , the length L1 of the first extension of the positive electrode sheet 正 , the length L2 of the second extension of the positive electrode sheet 正 Satisfying the above relationship can effectively fill the gap between the positive electrode sheet and the separator while preventing the second extension from bending to the active material area of ​​the positive electrode sheet, which is more conducive to improving the safety performance of the secondary battery.

[0064] In some embodiments, 3.5 mm ≤ L 正 ≤5.5mm.

[0065] In some embodiments, please refer to Figure 2 In the positive electrode sheet 30 , an insulating region 303 is provided between the bonding region 301 and the active material region 302 .

[0066] In the present application, by setting up an insulating area, the short circuit between the positive electrode plate and the negative electrode plate can be effectively prevented, thereby avoiding short circuit and overheating inside the battery, reducing the risk of battery combustion or explosion, and improving the safety performance of the battery.

[0067] In some embodiments, the dimension W of the bonding area in the positive electrode sheet along the first direction is 正 Meet: 3mm≤W 正 ≤[(W1-W3-W4) / 2]; wherein W1 is the size of the isolation membrane along the first direction, W3 is the size of the active material area of ​​the positive electrode sheet along the first direction, and W4 is the size of the insulating area along the first direction.

[0068] In the present application, the size of the bonding area in the positive electrode sheet satisfies the above range, which can take into account both the safety performance and capacity of the secondary battery.

[0069] In some embodiments, 3 mm ≤ W 正 ≤5mm. This helps to improve the safety performance of secondary batteries.

[0070] In some embodiments, when the positive electrode sheet includes a bonding area, the negative electrode sheet may or may not include a bonding area. It should be noted that when the positive electrode sheet includes a bonding area and the negative electrode sheet does not, the negative electrode sheet and the separator are prone to slippage and misalignment, and the production of laminated cells still requires encapsulation and fixation.

[0071] In some embodiments, the positive electrode sheet can be obtained by: 1) forming an active material area on the current collector; 2) forming an insulating area on both sides of the active material area along a first direction; 3) brushing glue on both sides of the insulating area away from the active material area along the first direction to form a bonding area; 4) using a special die to punch out the above-mentioned "I-shaped" positive electrode sheet.

[0072] In some embodiments, the negative electrode sheet includes a negative electrode current collector and an active material region disposed on at least one surface of the negative electrode current collector.

[0073] As an example, the negative electrode current collector has two surfaces facing each other in its thickness direction, and the active material region is provided on either or both of the two facing surfaces of the negative electrode current collector.

[0074] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer base layer and a metal layer formed on at least one surface of the polymer base material. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer base material (such as a base material of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0075] In some embodiments, the active material region of the negative electrode sheet includes a negative electrode active material, which includes metallic lithium, or an alloy of metallic lithium and various other metal or metalloid elements, and an inert current collector. The metal elements include tin (Sn), zinc (Zn), aluminum (Al), magnesium (Mg), silver (Ag), gold (Au), gallium (Ga), indium (In), platinum (Pt), etc.; the metalloid elements include boron (B), carbon (C), silicon (Si), etc.; and the inert current collector includes a copper foil current collector or a modified copper foil current collector.

[0076] In some embodiments, the active material region of the negative electrode sheet may further include a binder. The binder may 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).

[0077] In some embodiments, the active material region of the negative electrode sheet may further include a conductive agent, which may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0078] In some embodiments, the active material region of the negative electrode sheet may optionally further include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0079] In some embodiments, the active material region of the negative electrode sheet can be prepared by the following method: the components for preparing the active material region of the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder and any other components, are dispersed in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode current collector, and after drying, cold pressing and other processes, the active material region of the negative electrode sheet can be obtained.

[0080] In some embodiments, the positive electrode sheet includes a positive electrode current collector and an active material region disposed on at least one surface of the positive electrode current collector.

[0081] As an example, the positive electrode current collector has two surfaces facing each other in its thickness direction, and the active material region is provided on either or both of the two facing surfaces of the positive electrode current collector.

[0082] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer material base and a metal layer formed on at least one surface of the polymer material base. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0083] In some embodiments, the active material area of ​​the positive electrode plate includes a positive electrode active material. When the battery cell is a lithium metal secondary battery, the positive electrode active material may be a positive electrode active material for lithium ion batteries known in the art. As an example, the positive electrode active material may include at least one of the following materials: lithium phosphates containing olivine structure, lithium transition metal oxides and their respective modified compounds. However, the present application is not limited to these materials, and other traditional materials that can be used as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides may include, but are not limited to, lithium cobalt oxide (such as LiCoO2), lithium nickel oxide (such as LiNiO2), lithium manganese oxide (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also referred to as NCM333 ), LiNi 0.5 Co 0.2 Mn 0.3 O2 (also referred to as NCM 523 ), LiNi 0.5 Co 0.25 Mn 0.25 O2 (also referred to as NCM 211 ), LiNi 0.6 Co 0.2 Mn 0.2 O2 (also referred to as NCM 622 ), LiNi 0.8 Co 0.1 Mn 0.1 O2 (also referred to as NCM 811 ), lithium nickel cobalt aluminum oxide (such as LiNi 0.85 Co 0.15 Al 0.05 O2) and its modified compounds. Examples of olivine-structured lithium-containing phosphates may include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO4), a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon.

[0084] The charge and discharge process of a battery is accompanied by the deintercalation and consumption of active ions (Li ions). The molar content of Li varies when the battery is discharged to different states. The molar content of Li in the list of positive electrode active materials in this application refers to the material's initial state, i.e., the state before the materials are added. When the positive electrode active material is used in a battery system, the molar content of Li will change after charge and discharge cycles.

[0085] In the list of positive electrode active materials in this application, the molar content of oxygen is only a theoretical value. Lattice oxygen release will cause the molar content of oxygen to change, and the actual molar content of oxygen will fluctuate.

[0086] In some embodiments, the active material region of the positive electrode sheet may further optionally include a binder. As an example, the binder may 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.

[0087] In some embodiments, the active material region of the positive electrode sheet may further include a conductive agent. For example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0088] In some embodiments, the active material region of the positive electrode sheet can be prepared by the following method: the components for preparing the active material region of the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder and any other components, are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode current collector, and after drying, cold pressing and other processes, the active material region of the positive electrode sheet can be obtained.

[0089] [Electrolytes]

[0090] The electrolyte conducts ions between the positive and negative electrodes. This application does not specify the type of electrolyte, and the electrolyte can be selected based on the needs. For example, the electrolyte can be liquid, gel, or solid.

[0091] In some embodiments, the electrolyte is an electrolyte solution, which may be a lithium ion electrolyte, an ester electrolyte, an ether electrolyte, or the like.

[0092] In some embodiments, the electrolyte includes an electrolyte salt and a solvent.

[0093] In some embodiments, the electrolyte salt may be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalatoborate, lithium dioxalatoborate, lithium difluorodioxalatophosphate, and lithium tetrafluorooxalatophosphate.

[0094] In some embodiments, the solvent can be selected from at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methylpropyl carbonate, ethylpropyl 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, cyclopentane, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.

[0095] In some embodiments, the electrolyte may further include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, and additives that improve battery high or low temperature performance.

[0096] [Isolation film]

[0097] The present application does not particularly limit the type of separator. Any known porous separator with good chemical and mechanical stability can be used. For example, the base film of the separator can be a polyethylene porous film, a polypropylene porous film, a polyimide porous film, or a porous film formed by a composite of multiple polymers.

[0098] 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, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0099] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator can be formed into an electrode assembly through a lamination process.

[0100] In some embodiments, the battery cell may include an outer packaging that can be used to encapsulate the electrode assembly and the electrolyte.

[0101] In some embodiments, the outer packaging of the battery cell may be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. Alternatively, the outer packaging of the battery cell may be a soft shell, such as a pouch-type soft shell. The soft shell may be made of plastic, such as polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0102] The present application has no particular restrictions on the shape of the battery cell, which can be square or any other shape. For example, Figure 3 The battery cell 5 is a square structure as an example.

[0103] In some embodiments, reference Figure 4 , the outer packaging may include a shell 51 and a top cover assembly 53. Among them, the shell 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a accommodating cavity. The shell 51 has an opening connected to the accommodating cavity, and the top cover assembly 53 can be covered on the opening to close the accommodating cavity. The positive electrode sheet, the negative electrode sheet and the isolation membrane are formed into an electrode assembly 52 through a lamination process. The electrode assembly 52 is encapsulated in the accommodating cavity. The electrolyte is infiltrated in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the battery cell 5 can be one or more, and those skilled in the art can select according to specific actual needs.

[0104] In some embodiments, battery cells may be assembled into a battery module. The battery module may contain one or more battery cells. The specific number may be selected by those skilled in the art based on the application and capacity of the battery module.

[0105] Figure 5 4 is an example of a battery module. Figure 5 In the battery module 4, the plurality of battery cells 5 may be arranged in sequence along the length direction of the battery module 4. Of course, they may also be arranged in any other manner. The plurality of battery cells 5 may further be fixed by fasteners.

[0106] Optionally, the battery module 4 may further include a housing having an accommodation space, and the plurality of battery cells 5 are accommodated in the accommodation space.

[0107] In some embodiments, the battery modules described above may also be assembled into a battery pack. The battery pack may contain one or more battery modules, and the specific number may be selected by those skilled in the art based on the application and capacity of the battery pack.

[0108] Figure 6 and Figure 7 The battery pack 1 is used as an example. Figure 6 and Figure 7 The battery pack 1 may include a battery box and multiple battery modules 4 disposed in the battery box. The battery box includes an upper box body 2 and a lower box body 3. The upper box body 2 can cover the lower box body 3 and form an enclosed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner in the battery box.

[0109] Electrical devices

[0110] A second aspect of the embodiment of the present application further provides an electrical device, and the electrical device of the present application will be described below with reference to the accompanying drawings as appropriate.

[0111] The electrical device mentioned in the embodiments of the present application includes the secondary battery provided in the present application. The secondary battery can be used as a power source for the electrical device, and can also be used as an energy storage unit for the electrical device. The electrical device may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but is not limited thereto.

[0112] As the electrical device, a battery cell, a battery module or a battery pack can be selected according to its usage requirements.

[0113] Figure 8 This is an example of an electric device. This device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of the secondary battery, a battery pack or battery module can be used.

[0114] Another example device may be a mobile phone, a tablet computer, a notebook computer, etc. Such a device is usually required to be lightweight and thin, and may use a battery cell as a power source.

[0115] Example

[0116] Below, the embodiment of the present application is described. The embodiment described below is exemplary and is only used to explain the present application, and is not to be construed as limiting the present application. Where specific techniques or conditions are not specified in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. Reagents or instruments used that do not specify the manufacturer are conventional products that can be obtained commercially.

[0117] Example 1

[0118] 1) Preparation of negative electrode sheet: Electroplating lithium on the negative electrode current collector copper foil as the active material area, brushing polypropylene glue on both sides of the metal lithium active material along the first direction to form a bonding area, and using a negative electrode die to punch out to form a negative electrode sheet including the active material area, bonding area and tab. The size W2 of the active material area of ​​the negative electrode sheet is 41mm, and the size W of the bonding area of ​​the negative electrode sheet is 41mm. 负 The length of the active material area of ​​the negative electrode sheet is 4 mm, the length of the active material area of ​​the negative electrode sheet is 51 mm, and the length of the extension of the bonding area relative to the active material area is L 负 3mm;

[0119] 2) Preparation of positive electrode sheet: The positive electrode active material lithium nickel cobalt manganese oxide (LiNi 0.8 Co 0.1 Mn 0.1 O2), conductive agent carbon black, and binder polyvinylidene fluoride (PVDF) are dissolved in an appropriate amount of N-methylpyrrolidone (NMP) in a weight ratio of 97:2:1, and mixed evenly to prepare a positive electrode slurry. The positive electrode slurry is then evenly coated on the positive electrode current collector aluminum foil as the active material area. Alumina material is coated on both sides of the active material area along the first direction to form an insulating area. A positive electrode die is used to punch out to form a positive electrode sheet including an active material area, an insulating area, and a tab. Among them, the length of the active material area of ​​the positive electrode sheet is 50mm, the size W3 of the active material area of ​​the positive electrode sheet is 36mm, and the size W4 of the insulating area is 2mm;

[0120] 3) Lamination: Use a lamination machine to alternately stack the negative electrode sheets and the positive electrode sheets, and place a separator (polyethylene film, the dimension W1 along the first direction is 47 mm) between the positive electrode sheets and the negative electrode sheets to form a laminated battery cell, wherein there are 11 negative electrode sheets and 10 positive electrode sheets. During the lamination process, the separator is kept at a length T extending relative to the active material area of ​​the negative electrode sheet. 负 2mm.

[0121] 4) Preparation of secondary batteries: The stacked cells are hot pressed, and then the tabs are welded, the top side of the cells are packaged, the electrolyte (1 mol / L lithium hexafluorophosphate) is injected, and vacuum packaging is performed to assemble the lithium metal secondary battery.

[0122] Example 2-3

[0123] A lithium metal secondary battery was prepared in the same manner as in Example 1, except that the length L of the extension of the negative electrode sheet's bonding area relative to the active material area was 负 Different, or, the extension length T of the separator relative to the active material area of ​​the negative electrode sheet 负 For details, please see Table 1 below.

[0124] Comparative Examples 1-3

[0125] A lithium metal secondary battery was prepared in the same manner as in Example 1, except that the length L of the extension of the negative electrode sheet's bonding area relative to the active material area was 负 For details, please see Table 1 below.

[0126] Lithium metal secondary battery performance test

[0127] The lithium metal secondary batteries prepared in Examples 1-3 and Comparative Examples 1-3 were subjected to a cycle test under a clamp force of 0.5 MPa. The specific steps were as follows:

[0128] 1) The lithium metal secondary battery was charged to 4.3 V at a constant current of 0.5 C, then charged to 0.05 C at a constant voltage, and allowed to stand for 10 min;

[0129] 2) Discharge at a constant current of 0.5C to 2.8V and let it stand for 10 minutes;

[0130] 3) Repeat steps 1) and 2) for 100 turns.

[0131] If, during the above-mentioned cycle process, the charging capacity in step 1) exceeds the rated capacity, or the discharge capacity in step 2) remains normal or decreases slightly, resulting in the lithium metal secondary battery being unable to complete 100 cycles, then the lithium metal secondary battery is considered to have a micro-short circuit and overcharge; if the above-mentioned lithium metal secondary battery can complete 100 cycles, then the lithium metal secondary battery is considered to have no micro-short circuit and overcharge.

[0132] In addition, after disassembling the lithium metal secondary battery after 100 cycles, visually inspect the negative electrode's bonding area with the separator to determine if they remain bonded. If the negative electrode's bonding area is bonded to the separator and there is no spillage or migration of pulverized lithium powder, the battery's structural performance is considered acceptable. If the negative electrode's bonding area is damaged and there is significant spillage or migration of pulverized lithium powder, the battery's structural performance is considered unacceptable.

[0133] The test results of the lithium metal secondary batteries prepared in Examples 1-3 and Comparative Examples 1-3 are shown in Table 1 below.

[0134] Table 1:

[0135]

[0136] As can be seen from Table 1 above, compared with Comparative Example 1 (the bonding area of ​​the negative electrode plate does not extend relative to the active material area), Comparative Example 2 (the bonding area of ​​the negative electrode plate extends relative to the active material area insufficiently to fill the overhand gap T between the negative electrode plate and the separator), 负 ), and Comparative Example 3 (the amount of the negative electrode sheet's bonding area relative to the active material area is just equal to the overhand gap T between the negative electrode sheet and the separator 负 ), in Examples 1-3, the bonding area extends relative to the active material area L 负 Greater than T 负 , so that the extension L 负 Exceed T 负 The second extension portion L2 负 ) can bend along with the isolation film during the lamination process, so that L 负 Not exceeding T 负 The first extension portion L1 负 ) can effectively fill the gap between the negative electrode plate and the isolation membrane, that is, there will be no gap between the first extension and the isolation membrane. In this way, the negative electrode powdered lithium can be effectively blocked from overflowing to the surface of the positive electrode plate, thereby significantly improving the contact between the powdered lithium and the positive electrode plate, thereby improving the micro-short circuit and overcharge phenomena of the battery cell after cycling, which is beneficial to improving the safety performance of the lithium metal secondary battery.

[0137] Example 4

[0138] 1) Preparation of the negative electrode sheet: Lithium is electroplated on the negative electrode current collector copper foil as the active material area, and then punched using a negative electrode die to form a negative electrode sheet containing the active material area and the tab. The length of the active material area of ​​the negative electrode sheet is 51 mm, and the dimension W2 of the active material area of ​​the negative electrode sheet is 44 mm.

[0139] 2) Preparation of positive electrode sheet: The positive electrode active material lithium nickel cobalt manganese oxide (LiNi 0.8 Co 0.1 Mn 0.1O2), conductive agent carbon black, and binder polyvinylidene fluoride (PVDF) are dissolved in an appropriate amount of N-methylpyrrolidone (NMP) in a weight ratio of 97:2:1, and mixed evenly to prepare a positive electrode slurry. The positive electrode slurry is then evenly coated on the positive electrode current collector aluminum foil as an active material area, and alumina material is coated on both sides of the active material area along the first direction to form an insulating area. Polypropylene glue is brushed on both sides of the insulating area along the first direction to form a bonding area. A positive electrode die is used for punching to form a positive electrode plate comprising an active material area, an insulating area, a bonding area, and a tab. Among them, the length of the active material area of ​​the positive electrode plate is 50mm, the size W3 of the active material area of ​​the positive electrode plate is 33mm, and the size W4 of the insulating area is 2mm; the size W of the bonding area of ​​the positive electrode plate is 正 The length L of the extension of the bonding area of ​​the positive electrode relative to the active material area is 3 mm. 正 4.5mm;

[0140] 3) Lamination: Use a lamination machine to alternately stack the negative electrode sheets and the positive electrode sheets, and place a separator (polyethylene film, the dimension W1 along the first direction is 47 mm) between the positive electrode sheets and the negative electrode sheets to form a laminated battery cell. There are 11 negative electrode sheets and 10 positive electrode sheets. During the lamination process, the separator is kept protruding from the active material area of ​​the negative electrode sheet by a length of T. 正 3.5mm;

[0141] A lithium metal secondary battery was assembled using the same method as in Example 1.

[0142] Examples 5-6

[0143] A lithium metal secondary battery was prepared in the same manner as in Example 4, except that the length L of the second extension of the bonding area of ​​the positive electrode sheet relative to the active material area was 正 Different, or, the extension length T of the separator relative to the active material area of ​​the positive electrode sheet 正 Please see Table 2 below for details.

[0144] Comparative Examples 4-6

[0145] A lithium metal secondary battery was prepared in the same manner as in Example 4, except that the length L of the extension of the bonding area of ​​the positive electrode sheet relative to the active material area was 正 Please see Table 2 below for details.

[0146] Lithium metal secondary battery performance test

[0147] The lithium metal secondary batteries prepared in Examples 4-6 and Comparative Examples 4-6 were subjected to a cycle test under a clamp force of 0.5 MPa. The specific steps are as follows:

[0148] 1) The lithium metal secondary battery was charged to 4.3 V at a constant current of 0.5 C, then charged to 0.05 C at a constant voltage, and allowed to stand for 10 min;

[0149] 2) Discharge at a constant current of 0.5C to 2.8V and let it stand for 10 minutes;

[0150] 3) Repeat steps 1) and 2) for 100 turns.

[0151] If, during the above-mentioned cycle process, the charging capacity in step 1) exceeds the rated capacity, or the discharge capacity in step 2) remains normal or decreases slightly, resulting in the lithium metal secondary battery being unable to complete 100 cycles, then the lithium metal secondary battery is considered to have a micro-short circuit and overcharge; if the above-mentioned lithium metal secondary battery can complete 100 cycles, then the lithium metal secondary battery is considered to have no micro-short circuit and overcharge.

[0152] In addition, after disassembling the lithium metal secondary battery after 100 cycles, visually inspect the bonding area between the positive electrode and the separator to determine if they remain bonded. If the bonding area of ​​the positive electrode and the separator remain bonded and no lithium powder is spilled from the surface of the positive electrode, the battery cell structural performance is considered acceptable. If the bonding area of ​​the positive electrode is damaged and lithium powder is spilled from the surface of the positive electrode, the battery cell structural performance is considered unacceptable.

[0153] The test results of the lithium metal secondary batteries prepared in Examples 4-6 and Comparative Examples 4-6 are shown in Table 2 below.

[0154] Table 2:

[0155]

[0156] As can be seen from Table 2 above, compared with Comparative Example 4 (the bonding area of ​​the positive electrode sheet does not extend relative to the active material area) and Comparative Example 5 (the bonding area of ​​the positive electrode sheet extends relative to the active material area insufficiently to fill the overhand gap T between the positive electrode sheet and the separator), 正 ), and Comparative Example 6 (the amount of the positive electrode sheet's bonding area relative to the active material area is just equal to the overhand gap T between the positive electrode sheet and the separator 正 ), in Examples 4-6, the bonding area extends relative to the active material area L 正 Greater than T 正 , so that the extension L 正 Exceed T 正 The second extension portion L2 正 ) can bend along with the isolation film during the lamination process, so that L 正 Not exceeding T 正 The first extension portion L1 正) can effectively fill the gap between the positive electrode plate and the separator, that is, there will be no gap between the first extension of the positive electrode plate and the separator, so that the negative electrode powdered lithium can be effectively blocked from overflowing to the surface of the positive electrode plate, thereby significantly improving the contact between the powdered lithium and the positive electrode plate, thereby improving the micro-short circuit and overcharge phenomena of the battery cell after cycling, and improving the safety performance of the lithium metal secondary battery.

[0157] Examples 7-8

[0158] A lithium metal secondary battery was prepared in the same manner as in Example 1, except that the dimension W of the negative electrode sheet bonding area along the first direction was 负 Please see Table 3 below for details.

[0159] Examples 9-10

[0160] A lithium metal secondary battery was prepared in the same manner as in Example 4, except that the dimension W of the positive electrode sheet bonding area along the first direction was 正 Please see Table 3 below for details.

[0161] The test results of the lithium metal secondary batteries prepared in Examples 7-10 are shown in Table 3 below.

[0162] Table 3:

[0163]

[0164] In Table 3, “ / ” indicates non-existence.

[0165] It can be seen from Table 3 above that when the dimension W of the bonding area of ​​the negative electrode sheet along the first direction is 负 The size W of the bonding area of ​​the positive electrode sheet along the first direction is set to be above 4 mm. 正 Setting it above 3 mm can effectively cope with the overall expansion of the lithium metal secondary battery, meet the integrity of the bonding between the bonding area and the isolation membrane and the safety performance requirements of the lithium metal secondary battery.

[0166] Example 11

[0167] A negative electrode sheet was prepared in the same manner as in Example 1, a positive electrode sheet was prepared in the same manner as in Example 4, and a lithium metal secondary battery was assembled.

[0168] Example 12

[0169] A negative electrode sheet was prepared in the same manner as in Example 3, a positive electrode sheet was prepared in the same manner as in Example 6, and a lithium metal secondary battery was assembled.

[0170] The test results of the lithium metal secondary batteries prepared in Examples 11 and 12 are shown in Table 4 below.

[0171] Table 4:

[0172]

[0173] It can be seen from Table 4 above that by setting the negative electrode sheet bonding area relative to the active material area extension L 负 Greater than T 负 , and the bonding area of ​​the positive electrode sheet is arranged relative to the extension portion L of the active material area 正 Greater than T 正 It can effectively prevent the negative electrode powdered lithium from overflowing to the surface of the positive electrode, thereby significantly improving the contact between the powdered lithium and the positive electrode, and then improving the micro-short circuit and overcharge phenomena of the battery cell after cycling, which is beneficial to improving the safety performance of lithium metal secondary batteries.

[0174] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and any embodiments having substantially the same structure and effect as the technical concept within the scope of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the present application, any other embodiments that can be conceived by those skilled in the art and that combine some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A secondary battery, characterized in that: It includes a stacked structure formed by stacking a negative electrode sheet, a separator and a positive electrode sheet. The negative electrode sheet and / or the positive electrode sheet comprises an active material region and a bonding region, wherein the bonding region is located on both sides of the active material region along a first direction; In the second direction, the bonding area extends relative to the active material area, and the isolation film extends relative to the active material area; On one side in the second direction, a length of the protrusion of the bonding area relative to the active material area is L, and a length of the protrusion of the isolation film relative to the active material area is T, wherein L is greater than T; The first direction is perpendicular to the second direction; The active material region of the negative electrode plate includes metallic lithium.

2. The secondary battery according to claim 1, wherein On one side in the second direction, the protruding portion includes a first protruding portion and a second protruding portion continuous along the second direction, the second protruding portion is bent relative to the first protruding portion and bonded to a surface of the first protruding portion; The length of the first extension portion is L1, the length of the second extension portion is L2, Then L1 = T; 0<L2<5mm-T, and L=L1+L2.

3. The secondary battery according to claim 1 or 2, characterized in that The pole piece has a pole tab on one side of the first direction, and the pole tab is located on a side of the bonding area away from the active material area.

4. The secondary battery according to claim 2, wherein The negative electrode sheet includes the bonding area, On one side in the second direction, the extension length of the separator relative to the active material area of ​​the negative electrode plate is T 负 The length of the extension portion of the negative electrode is L 负 , the length of the first extension portion is L1 负 , the length of the second extension is L2 负 , where T 负 、L 负 、L1 负 、L2 负 Satisfies the following relationship: 2mm≤T 负 <5mm, L1 负 =T 负 ;0<L2 负 <3mm, and L 负 =L1 负 +L2 负 .

5. The secondary battery according to claim 4, wherein The dimension W of the bonding area in the negative electrode sheet along the first direction 负 satisfy: 4mm≤W 负 ≤[(W1-W2) / 2]; Wherein, W1 is the size of the isolation membrane along the first direction, and W2 is the size of the active material area of ​​the negative electrode sheet along the first direction.

6. The secondary battery according to claim 5, characterized in that 4mm≤W 负 ≤6mm。 7. The secondary battery according to claim 2, characterized in that The positive electrode sheet includes the bonding area, On one side in the second direction, the extension length of the separator relative to the active material area of ​​the positive electrode sheet is T 正 , the length L of the protruding portion of the positive electrode sheet 正 , the length of the first extension portion is L1 正 , the length of the second extension is L2 正 , where T 正 、L 正 、L1 正 、L2 正 Satisfies the following relationship: 3.5mm≤T 正 ≤5mm, L1 正 = T 正 where 0 < L2 正 ≤ 1.5 mm, and L 正 = L1 正 + L2 正 .

8. The secondary battery according to claim 7, wherein In the positive electrode sheet, an insulating region is further provided between the bonding region and the active material region.

9. The secondary battery according to claim 8, characterized in that The dimension W of the bonding area in the positive electrode sheet along the first direction 正 satisfy: <h2 style=";text-align:left;direction:ltr">3mm≤W<h2 style=";text-align:left;direction:ltr"> 正 <h2 style=";text-align:left;direction:ltr"> ≤[(W1-W3-W4) / 2]; Wherein, W1 is the size of the isolation membrane along the first direction, W3 is the size of the active material area of ​​the positive electrode sheet along the first direction, and W4 is the size of the insulating area along the first direction.

10. The secondary battery according to claim 9, wherein 3mm≤W 正 ≤5mm。 11. An electrical device, characterized in that: A secondary battery comprising the secondary battery according to any one of claims 1 to 10.

Images