CN118266126A

CN118266126A - Electrochemical device and electronic device

Info

Publication number: CN118266126A
Application number: CN202280010456.9A
Authority: CN
Inventors: 刘道林; 林森; 何平
Original assignee: Ningde Amperex Technology Ltd
Current assignee: Ningde Amperex Technology Ltd
Priority date: 2022-03-29
Filing date: 2022-03-29
Publication date: 2024-06-28
Also published as: WO2023184142A1

Abstract

The application discloses an electrochemical device and an electronic device. The electrochemical device includes a first case, a second case, and a separator between the first case and the second case. The electrochemical device includes a first sealing part, the first case includes a first sealing region located at the first sealing part, the second case includes a second sealing region located at the first sealing part, and the separator includes a first region located between the first sealing region and the second sealing region. By making the adhesive strength F N/mm between the first seal region and the first region, the tensile strength F N/mm of the separator, and the tensile rate S of the separator satisfy F/(fXS). Ltoreq.15, the first seal portion can be made to have excellent structural reliability.

Description

Electrochemical device and electronic device

Technical Field

The present application relates to the field of electrochemistry, and in particular, to an electrochemical device and an electronic device.

Background

Currently, batteries are widely used in electronic products such as unmanned aerial vehicles, mobile phones, flat panels, notebook computers and the like. Since a single cell is not capable of achieving the desired output power in certain application scenarios; therefore, a plurality of battery cells are generally connected in series, parallel or series-parallel with each other so that the plurality of battery cells cooperate together to achieve the desired power output. However, although the output power can be improved by connecting a plurality of battery cells in series, parallel or series-parallel connection, the energy density of the whole battery pack is low. Therefore, the design of the same-pouch serial/parallel battery is proposed, the same-pouch serial/parallel battery comprises a housing and a plurality of electrode assemblies arranged in the same housing, the electrode assemblies connected in series are separated by a separator to avoid decomposition of electrolyte under high voltage, and the electrode assemblies connected in parallel are separated by the separator to avoid mutual interference.

Disclosure of Invention

The inventor of the present application has found through research that when the seal portion of the battery connected in series/parallel with the pouch is subjected to impact to be bent or when the seal portion is folded, the internal separator is inevitably pulled, so that the probability of failure of the seal portion is high.

In view of the above, the present application provides an electrochemical device and an electronic device, so as to improve the structural reliability of the seal portion of the battery connected in series/parallel with the pouch.

To solve the above technical problem, according to a first aspect of the present application, an electrochemical device is provided. The electrochemical device includes a first case, a second case, and a separator between the first case and the second case. The electrochemical device includes a first sealing part, the first case includes a first sealing region located at the first sealing part, the second case includes a second sealing region located at the first sealing part, and the separator includes a first region located between the first sealing region and the second sealing region. The adhesive strength between the first seal area and the first area is F N/mm, the tensile strength of the separator is F N/mm, and the tensile rate of the separator is S, so that F/(fXS) is less than or equal to 15.

Through F, f and S satisfying above-mentioned relation, when receiving the impact and taking place to buckle or carry out the hem to first seal portion, on the one hand, the isolator itself has sufficient tensile strength and ductility and buffers the stress and the meeting an emergency of buckling department, simultaneously, the bonding strength between isolator and the casing can bear the stress of buckling department to avoid the production of breaking the condition, make first seal portion have excellent structural reliability.

In some embodiments, 1.ltoreq.F/(fXS). Ltoreq.10. Through satisfying F/(F x S) and be less than or equal to 10, the tensile strength and the ductility of isolator self can cushion the stress and the meeting an emergency of buckling department better, simultaneously, through satisfying F/(F x S) and be more than or equal to 1, the bonding strength between isolator and the casing can bear the stress of buckling department better to further improve the structural reliability of first seal portion.

In some embodiments, F.gtoreq.1. At this time, the spacer and the housing have good bonding strength, so that the risk of separation of the spacer and the housing can be further suppressed, and the structural reliability of the first seal part is improved.

In some embodiments, f is ≡1. At this time, the spacer itself has better structural strength, can restrain the fracture of itself when receiving the buckling and pulling of first seal portion, and then improves the structural reliability of first seal portion.

In some embodiments, S is ≡9%. At this time, the ductility of isolator self is better, can cushion the strain when first seal portion buckles better to reduce the risk that isolator self and isolator and casing junction break, improve the structural reliability of first seal portion.

In some embodiments, the number of separators is n.gtoreq.1, and the electrochemical device satisfies f.gtoreq.1+0.1n. In some embodiments, the electrochemical device satisfies S.gtoreq.8+n%. The more the quantity of the isolating pieces is, the greater the bending and pulling stress strain of the isolating pieces is, and the above relation is satisfied through f and/or S, so that the bearing degree of the isolating pieces to bending and pulling can be further improved, and the structural reliability of the first sealing portion is further improved.

In some embodiments, the thickness of the separator is H mm, satisfying H.ltoreq.0.3.

In some embodiments, the first seal portion includes a first bend portion. Through setting up first kink, when first seal portion received the external impact, can play the cushioning effect, reduce its to the pulling of inside separator, and then improve the structural reliability of first seal portion.

In some embodiments, the length of the first seal portion is L, and the coefficient of variation CV of the thickness at both ends and the middle L/2 of the first seal portion is less than or equal to 5% along the length direction of the first seal portion. Through making the thickness coefficient of variation CV of middle position and both ends in the length direction of first seal portion be less than or equal to 5%, when its along length direction buckling, the stress of everywhere is more balanced, reduces the risk that local fracture is led to because local stress is too high to further improve the structural reliability of first seal portion.

In some embodiments, the first housing further comprises a first body portion, the first folded portion comprises a first folded portion and a second folded portion, the first folded portion is connected to the first body portion through the second folded portion, and the first folded portion is located between the first body portion and the second folded portion. Through setting up first folded edge portion and being located between first main part portion and the second folded edge portion for first seal portion when receiving external impact, first folded edge portion can provide the buffering supporting role, suppresses excessive buckling of second folded edge portion and first main part junction, reduces the pulling to inside isolator, improves the structural reliability of first seal portion.

In some embodiments, the electrochemical device further comprises a first electrode assembly and a second electrode assembly, a first cavity is arranged between the first shell and the separator, a second cavity is arranged between the second shell and the separator, the first electrode assembly is arranged in the first cavity, the second electrode assembly is arranged in the second cavity, and the first electrode assembly and the second electrode assembly are connected in series.

In some embodiments, the spacer includes a first encapsulation layer, an intermediate layer, and a second encapsulation layer, the intermediate layer is located between the first encapsulation layer and the second encapsulation layer, and materials of the first encapsulation layer and the second encapsulation layer include a first polymer material. The material of the intermediate layer comprises at least one of a metal material, a second polymer material or a carbon material.

In some embodiments, the first polymeric material comprises polypropylene, anhydride modified polypropylene, polyethylene, ethylene propylene copolymer, polyvinyl chloride, polystyrene, polyether nitrile, polyurethane, polyamide, polyester, amorphous alpha-olefin copolymer, or at least one of the derivatives thereof.

In some embodiments, the metallic material includes at least one of Ni, ti, cu, ag, au, pt, fe, co, cr, W, mo, al, mg, K, na, ca, sr, ba, si, ge, sb, pb, in, zn, stainless steel (SUS), and combinations or alloys thereof.

In some embodiments, the second polymeric material comprises polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polyetheretherketone, polyimide, polyamide, polyethylene glycol, polyamideimide, polycarbonate, cyclic polyolefin, polyphenylene sulfide, polyvinyl acetate, polytetrafluoroethylene, polymethylenenaphthalene, polyvinylidene fluoride, polypropylene carbonate, poly (vinylidene fluoride-hexafluoropropylene), poly (vinylidene fluoride-co-chlorotrifluoroethylene), silicone, vinylon, polypropylene, anhydride modified polypropylene, polyethylene, ethylene propylene copolymer, polyvinyl chloride, polystyrene, polyethernitrile, polyurethane, polyphenylene oxide, polyester, polysulfone, amorphous alpha-olefin copolymer, or at least one of the derivatives thereof.

In some embodiments, the carbon material comprises at least one of a carbon felt, a carbon film, a carbon black, acetylene black, fullerenes, a conductive graphite film, or a graphene film.

The second aspect of the present application also provides an electronic device comprising the electrochemical device of any one of the above.

According to the electrochemical device provided by the application, F/(F multiplied by S) is less than or equal to 15 through the bonding strength F N/mm between the first seal area and the first area, the tensile strength F N/mm of the separator and the tensile rate S of the separator, and when the first seal part is impacted to bend or the first seal part is folded, on one hand, the separator has enough tensile strength and ductility to buffer the stress and strain at the bending part, and meanwhile, the bonding strength between the separator and the shell can bear the stress at the bending part, so that the cracking condition is avoided, and the first seal part has excellent structural reliability.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are needed in the embodiments of the present application will be briefly described below, and it is obvious that the drawings described below are only some embodiments of the present application, and other drawings may be obtained according to the drawings for those of ordinary skill in the art.

FIG. 1 is a schematic side view of a battery according to one embodiment of the present application from a first perspective; wherein the first seal part is to be subjected to bending processing;

FIG. 2 is a schematic side view of a battery according to one embodiment of the present application from a second perspective; wherein the first seal part is to be subjected to bending processing;

Fig. 3 is an exploded view of a battery according to an embodiment of the present application at a first viewing angle; wherein the battery has a separator;

fig. 4 is an exploded view of a battery according to another embodiment of the present application at a first viewing angle; wherein the battery has two separators;

FIG. 5 is a schematic side view of a spacer according to one embodiment of the present application from a first perspective;

Fig. 6 is a schematic side view of a spacer according to a second aspect of an embodiment of the present application.

Detailed Description

In order that the application may be readily understood, a more particular description thereof will be rendered by reference to specific embodiments that are illustrated in the appended drawings. It will be understood that when an element is referred to as being "fixed" to another element, it can be directly on the other element or one or more intervening elements may be present therebetween. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or one or more intervening elements may be present therebetween. The terms "vertical," "horizontal," "left," "right," and the like are used herein for illustrative purposes only.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description of the application herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and/or" as used in this specification includes any and all combinations of one or more of the associated listed items.

The inventors of the present application have found through studies that the separator in the pouch-in-pouch series/parallel battery needs to be packaged together with the periphery of the upper and lower cases, because the packaging region introduces the separator, which poses challenges for packaging strength and sealability. Meanwhile, when the battery packaging area is impacted to bend or fold, the separator is pulled to a certain extent, on one hand, the separator needs to be guaranteed not to be pulled, and meanwhile, the sealing part of the separator and the shell needs to be restrained from losing efficacy such as cracks. Particularly when there are a plurality of separators in the battery, the thickness of the package region increases, so that the risk of fracture failure after bending of the package region increases.

In view of this, referring to fig. 1 to 6, the present embodiment provides an electrochemical device, and for convenience of description, the electrochemical device is exemplified as a battery 10 in the following embodiments. The battery 10 includes a first case 200, a second case 300, and a separator 100 between the first case 200 and the second case 300. The battery 10 may also include two or more electrode assemblies. Referring to fig. 3, when the number of the separators 100 is one, the separator 100 divides the space enclosed by the first case 200 and the second case 300 into two spaces independent of each other, the number of the electrode assemblies may be two, and the two electrode assemblies are disposed in the two spaces independent of each other in a one-to-one correspondence. Referring to fig. 4, when the number of the separators 100 is two, the separator 100 divides the space enclosed by the first case 200 and the second case 300 into three spaces independent of each other, the number of the electrode assemblies may be three, and the three electrode assemblies are disposed in the three spaces independent of each other in one-to-one correspondence. And so on. For convenience of description, the following description will be given by taking one in number of separators 100 and two in number of electrode assemblies as an example. When the number of the spacers 100 is one, one side of the spacers 100 is connected to the first case 200 and the other side is connected to the second case 300.

The battery 10 is connected to each other by the peripheral edges of the first case 200, the separator 100, and the second case 300, for example, by heat fusion or adhesive, etc., to achieve sealing of the battery 10 and prevent the electrolyte in the battery 10 from being exposed. The shape of the seal area depends on the shape of the battery 10, and in one embodiment, when the battery 10 is a square battery 10, referring to fig. 5, the seal area may have a rectangular shape and include four seal sides.

For convenience of description, one of the seal sides of the battery 10 is described below as an example, regardless of the shape of the seal area of the battery 10. For ease of distinction, the seal edge is named first seal portion 600. The tab 410 of the electrode assembly needs to protrude from the sealing edge of the battery 10, and the tab 410 may protrude from the first sealing part 600 or may protrude from other sealing edges.

The first case 200 includes a first sealing region 610 located at the first sealing part 600, the second case 300 includes a second sealing region 630 located at the first sealing part 600, and the spacer 100 includes a first region 620 located between the first sealing region 610 and the second sealing region 630, see fig. 5, wherein the first region 620 is located at a region between the outer edge of the solid line and the dotted line. When the number of the spacers 100 is one, one side of the first region 620 of the spacer 100 is connected to the first sealing region 610, and the other side is connected to the second sealing region 630. When the number of the spacers 100 is plural, the spacers 100 in the present embodiment are the spacers 100 contacting the first seal area 610, and at this time, the spacers 100 are indirectly connected to the second seal area 630 through the other spacers 800.

In this embodiment, the adhesive strength F N/mm between the first seal area 610 and the first area 620, the tensile strength F N/mm of the separator 100, and the tensile modulus S of the separator 100 satisfy F/(fXS). Ltoreq.15. F/(F X S) may be specifically 15, 13, 11, 9, 7, 5 or 3. Specific definitions of the adhesive strength F N/mm, the tensile strength f N/mm of the separator 100, and the tensile rate S of the separator 100 and the test method are described later. The inventor of the present application considers that, in order to ensure that the first seal portion 600 is not likely to fail after bending, it is necessary to comprehensively consider the bonding strength FN/mm between the separator 100 and the case, the tensile strength FN/mm of the separator 100, and the tensile rate S of the separator 100, and that, when the first seal portion 600 is bent or folded by impact through F, f and S, the separator 100 itself has sufficient tensile strength and ductility to buffer the stress and strain at the bending, and at the same time, the bonding strength between the separator 100 and the case can withstand the stress at the bending, thereby avoiding the occurrence of the breakage, so that the first seal portion 600 has excellent structural reliability.

In some embodiments, the cell 10 may satisfy 1.ltoreq.F/(fXS). Ltoreq.10. By satisfying F/(f×S). Ltoreq.10, the tensile strength and ductility of the separator 100 itself can better buffer the stress and strain at the bending portion, and at the same time, by satisfying F/(f×S). Gtoreq.1, the adhesive strength between the separator 100 and the case can better withstand the stress at the bending portion, thereby further improving the structural reliability of the first seal portion 600.

In some embodiments, F is 1N/mm or more. At this time, the spacer 100 and the case have a good adhesive strength, and the risk of separation of the spacer 100 and the case can be further suppressed, thereby improving the structural reliability of the first seal portion 600.

In some embodiments, f.gtoreq.1N/mm. At this time, the separator 100 itself has a good structural strength, and can suppress breakage of itself when being bent and pulled by the first seal portion 600, thereby improving the structural reliability of the first seal portion 600.

In some embodiments, S is ≡9%. At this time, the ductility of the separator 100 itself is good, and the strain when the first seal portion 600 is bent can be better buffered, so that the risk of breakage of the separator 100 itself and the joint between the separator 100 and the case is reduced, and the structural reliability of the first seal portion 600 is improved.

The inventors of the present application have also found that the number of spacers 100 has an influence on the structural reliability of the first seal portion 600, and in this regard, in one embodiment, the number of spacers 100 is n.gtoreq.1, satisfying f.gtoreq.1+0.1n.n/mm, for example, when n=1, f.gtoreq.1.1; when n=3, f is not less than 1.3. In one embodiment, S.gtoreq.8+n% is satisfied, e.g., S.gtoreq.9% when N=1; when n=3, S is not less than 11%. The inventors of the present application have found that, as the number of spacers is increased, when the first seal portion 600 is bent, the tensile stress and strain to which the spacer 100 is subjected will increase accordingly, and that the above-described relationship is satisfied by f and/or S, so that the degree of resistance to pulling of the spacer 100 can be further improved, and the structural reliability of the first seal portion 600 can be further improved.

In some embodiments, the thickness H of the spacer 100 satisfies H.ltoreq.0.3 mm.

In some embodiments, the first seal portion 600 includes a first bending portion 640, i.e., the first seal portion 600 completes at least one bending. By providing the first bending portion 640, when the first seal portion 600 receives an external impact, a buffering effect can be achieved, pulling of the inner spacer can be reduced, and structural reliability of the first seal portion 600 can be improved.

In some embodiments, the length of the first seal portion 600 is L, and the coefficient of variation CV of the thickness at both ends and the middle L/2 of the first seal portion 600 is less than or equal to 5% along the length direction of the first seal portion 600. In the measurement process, three data of the thickness of the two ends of the first seal part 600 and the thickness of the middle of the first seal part 600 are measured respectively, and then the standard deviation and the average value of the three data are calculated, wherein the ratio of the standard deviation to the average value is the variation coefficient CV, in the embodiment, the variation coefficient CV is controlled to be less than or equal to 5%, when the first seal part 600 is bent along the length direction, the stress of each part is more balanced, the risk of local fracture caused by local stress is reduced, and the structural reliability of the first seal part 600 is further improved

In some embodiments, the first case 200 further includes a first body part 11, the first body part 11 being a portion recessed in the first case 200 to form a cavity accommodating the electrode assembly, the first bent part 640 including a first flange part 641 and a second flange part 642, the first flange part 641 being connected to the first body part 11 by the second flange part 642, and the first flange part 641 being located between the first body part 11 and the second flange part 642. In the processing of the battery 10, after the first seal portion 600 is sealed, the first flange 641 is bent toward the first body 11 with respect to the second flange 642, specifically, the first flange 641 and the second flange 642 may be stacked, and the interface between the first flange 641 and the second flange 642 is a folded surface. In some embodiments, the first bending portion 640 may further perform a secondary bending, that is, after the first edge-folding portion 641 is bent relative to the second edge-folding portion 642, the second edge-folding portion 642 is further bent towards the first main body portion 11, and in particular, the first edge-folding portion 641 may be bent to be attached to a wall surface of the first main body portion 11 facing the first bending portion 640. At this time, when the first seal portion 600 receives an external impact, the first flange 641 can provide a cushioning support function, suppress excessive bending at the junction of the second flange 642 and the first body 11, reduce pulling of the inner spacer, and improve structural reliability of the first seal portion 600.

In some embodiments, referring to fig. 3, the electrochemical device further includes a first electrode assembly 400 and a second electrode assembly 500, the separator 100 is provided with a first cavity and a second cavity at both sides thereof, the first electrode assembly 400 is provided in the first cavity, the second electrode assembly 500 is provided in the second cavity, and the first electrode assembly 400 is connected in series with the second electrode assembly 500.

In some embodiments, referring to fig. 6, the spacer 100 includes a first encapsulation layer 120, an intermediate layer 110, and a second encapsulation layer 130, the intermediate layer 110 is located between the first encapsulation layer 120 and the second encapsulation layer 130, and materials of the first encapsulation layer 120 and the second encapsulation layer 130 include a first polymer material. The material of the intermediate layer 110 includes at least one of a metal material, a second polymer material, or a carbon material.

The separator 100 may have an electronic insulation property or an electronic conduction property, and both sides of the separator 100 form respective independent sealed chambers, each of which contains an electrode assembly and an electrolyte to form an electrochemical cell. Wherein both sides of the separator 100 are directly in contact with the separator of the adjacent electrode assembly and form electrical insulation. At this time, at least two tabs 410 are drawn out of each of the two electrode assemblies, and the two electrode assemblies are connected in series or in parallel through the tabs 410.

The metal material includes at least one of Ni, ti, cu, ag, au, pt, fe, co, cr, W, mo, al, mg, K, na, ca, sr, ba, si, ge, sb, pb, in, zn, stainless steel (SUS), and a composition or alloy thereof.

The second polymer material comprises polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polyether ether ketone, polyimide, polyamide, polyethylene glycol, polyamide imide, polycarbonate, cyclic polyolefin, polyphenylene sulfide, polyvinyl acetate, polytetrafluoroethylene, polymethylene naphthalene, polyvinylidene fluoride, polypropylene carbonate, poly (vinylidene fluoride-hexafluoropropylene), poly (vinylidene fluoride-co-chlorotrifluoroethylene), silicone, vinylon, polypropylene, anhydride modified polypropylene, polyethylene, ethylene propylene copolymer, polyvinyl chloride, polystyrene, polyether nitrile, polyurethane, polyphenylene oxide, polyester, polysulfone, amorphous alpha-olefin copolymer, or at least one of the derivatives thereof.

The carbon material includes at least one of a carbon felt, a carbon film, carbon black, acetylene black, fullerenes, conductive graphite film, or graphene film.

The second aspect of the present application also provides an electronic device comprising the electrochemical device of any one of the embodiments described above.

The electrode assembly of the present application is not particularly limited, and any electrode assembly of the related art may be used as long as the object of the present application can be achieved, for example, a laminate type electrode assembly or a roll type electrode assembly may be used. The electrode assembly generally includes a positive electrode tab, a negative electrode tab, and a separator.

The negative electrode sheet in the present application is not particularly limited as long as the object of the present application can be achieved. For example, the negative electrode tab typically includes a negative electrode current collector and a negative electrode active material layer. Among them, the negative electrode current collector is not particularly limited, and any negative electrode current collector known in the art, such as copper foil, aluminum alloy foil, and composite current collector, etc., may be used. The anode active material layer includes an anode active material, which is not particularly limited, and any anode active material known in the art may be used. For example, at least one of artificial graphite, natural graphite, mesophase carbon microspheres, soft carbon, hard carbon, silicon carbon, lithium titanate, and the like may be included.

The positive electrode sheet in the present application is not particularly limited as long as the object of the present application can be achieved. For example, the positive electrode sheet typically includes a positive electrode current collector and a positive electrode active material. The positive electrode current collector is not particularly limited, and may be any positive electrode current collector known in the art, such as an aluminum foil, an aluminum alloy foil, or a composite current collector. The positive electrode active material is not particularly limited, and may be any positive electrode active material of the prior art, and the active material includes at least one of NCM811, NCM622, NCM523, NCM111, NCA, lithium iron phosphate, lithium cobalt oxide, lithium manganate, lithium iron phosphate, or lithium titanate.

The electrolyte in the present application is not particularly limited, and any electrolyte known in the art may be used, and may be, for example, any of gel state, solid state, and liquid state, and for example, the liquid electrolyte may include a lithium salt and a nonaqueous solvent.

The lithium salt is not particularly limited, and any lithium salt known in the art may be used as long as the object of the present application can be achieved. For example, the lithium salt may include at least one of lithium hexafluorophosphate (LiPF ₆), lithium tetrafluoroborate (LiBF ₄), lithium difluorophosphate (LiPO ₂F ₂), lithium bis (trifluoromethanesulfonyl) imide LiN (CF ₃SO ₂) ₂ (LiTFSI), lithium bis (fluorosulfonyl) imide Li (N (SO ₂F) ₂) (LiFSI), lithium bis (oxalato) borate LiB (C ₂O ₄) ₂ (LiBOB), or lithium difluorooxalato borate LiBF ₂(C ₂O ₄) (lidaob).

The nonaqueous solvent is not particularly limited as long as the object of the present application can be achieved. For example, the nonaqueous solvent may include at least one of a carbonate compound, a carboxylate compound, an ether compound, a nitrile compound, or other organic solvent.

For example, the carbonate compound may include at least one of diethyl carbonate (DEC), dimethyl carbonate (DMC), ethylmethyl carbonate (EMC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), ethylene Carbonate (EC), propylene Carbonate (PC), butylene Carbonate (BC), vinyl Ethylene Carbonate (VEC), fluoroethylene carbonate (FEC), 1, 2-difluoroethylene carbonate, 1, 2-trifluoroethylene carbonate, 1, 2-tetrafluoroethylene carbonate, 1-fluoro-2-methylethylene carbonate, 1-fluoro-1-methylethylene carbonate, 1, 2-difluoro-1-methylethylene carbonate, 1, 2-trifluoro-2-methylethylene carbonate, or trifluoromethyl ethylene carbonate.

The separator in the present application is not particularly limited, and for example, the separator includes a polymer or an inorganic substance formed of a material stable to the electrolyte of the present application, and the like. The separator should generally be ion conductive and electronically insulating.

For example, the separator may include a substrate layer and a surface treatment layer. The substrate layer may be a nonwoven fabric, a film or a composite film having a porous structure, and the material of the substrate layer may be at least one selected from polyethylene, polypropylene, polyethylene terephthalate and polyimide. Optionally, a polypropylene porous membrane, a polyethylene porous membrane, a polypropylene nonwoven fabric, a polyethylene nonwoven fabric, or a polypropylene-polyethylene-polypropylene porous composite membrane may be used. Optionally, a surface treatment layer is disposed on at least one surface of the substrate layer, and the surface treatment layer may be a polymer layer or an inorganic layer, or may be a layer formed by mixing a polymer and an inorganic material.

For example, the inorganic layer includes inorganic particles and a binder, and the inorganic particles are not particularly limited, and may be selected from at least one of alumina, silica, magnesia, titania, hafnia, tin oxide, ceria, nickel oxide, zinc oxide, calcium oxide, zirconia, yttria, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, and barium sulfate, for example. The binder is not particularly limited and may be, for example, one or a combination of several selected from polyvinylidene fluoride, a copolymer of vinylidene fluoride-hexafluoropropylene, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene, and polyhexafluoropropylene. The polymer layer contains a polymer, and the material of the polymer comprises at least one of polyamide, polyacrylonitrile, acrylic polymer, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl ether, polyvinylidene fluoride or poly (vinylidene fluoride-hexafluoropropylene).

Hereinafter, embodiments of the present application will be described in more detail with reference to examples and comparative examples. The various tests and evaluations were carried out by the following methods, and unless otherwise specified, "parts" and "%" are weight basis.

Example 1

Preparation of negative electrode plate

Graphite, conductive carbon black and styrene-butadiene rubber serving as anode active materials are prepared according to the mass ratio of 96:1.5:2.5, mixing, adding deionized water, preparing into slurry with 70% of solid content, and uniformly stirring. The slurry was uniformly coated on one surface of a copper foil having a thickness of 10 μm, and dried at 110 deg.c to obtain a negative electrode tab coated with a negative electrode active material layer on one side having a coating thickness of 150 μm, and then the above coating steps were repeated on the other surface of the copper foil. After the coating is completed, the pole piece is cut into the specification of 41mm multiplied by 61mm and the pole lug 410 is welded for later use.

Preparation of positive electrode plate

Positive electrode active material LiCoO ₂, conductive carbon black and PVDF (polyvinylidene fluoride) are mixed according to the mass ratio of 97.5:1.0:1.5, adding NMP, preparing into slurry with 75% of solid content, and uniformly stirring. And uniformly coating the slurry on one surface of an aluminum foil with the thickness of 12 mu m, and drying at 90 ℃ to obtain the positive electrode plate with the coating thickness of 100 mu m and the single-sided coated positive electrode active material layer. The above steps are then repeated on the other surface of the aluminum foil. After the coating is completed, the pole piece is cut into 38mm x 58mm specifications and the tab 410 is welded for use.

Preparation of electrolyte

Organic solvents EC (ethylene carbonate), EMC (ethylmethyl carbonate) and DEC (diethyl carbonate) were first mixed in a dry argon atmosphere in mass ratio EC: EMC: dec=30: 50:20, and then adding LiPF ₆ (lithium hexafluorophosphate) into an organic solvent to dissolve and mix uniformly, thus obtaining an electrolyte with LiPF ₆ concentration of 1.15M.

Preparation of electrode assemblies

And (3) selecting a PE (polyethylene) film with the thickness of 15 mu m as an isolating film, respectively placing a positive electrode plate on two sides of a negative electrode plate, placing a layer of isolating film between the positive electrode plate and the negative electrode plate to form a laminated sheet, fixing four corners of the whole laminated sheet structure, and leading out a positive electrode tab 410 and a negative electrode tab 410 to obtain the electrode assembly.

Preparation of separator 100

(1) Uniformly dispersing a packaging substance PP in a packaging layer into a dispersing agent NMP (N-methylpyrrolidone) to obtain packaging layer suspension, wherein the concentration of the suspension is 45wt%;

(2) An encapsulation layer PP having a thickness of 40 μm was prepared on both surfaces of an interlayer PET (polyethylene terephthalate) film having a thickness of 20 μm using a laminator.

(3) And drying the dispersing agent NMP in the packaging layer suspension at 130 ℃ to finish the preparation of the separator 100.

Assembly of electrode assembly

The aluminum plastic film formed by punching the pit (i.e., the first case 200 in the foregoing embodiment) is 90 μm thick, placed in the assembly jig with the pit face upward, then one electrode assembly a is placed in the pit, then the separator 100 is placed on the electrode assembly a, and one side of the separator 100 is brought into contact with the separator of the electrode assembly a, and is pressed by applying an external force. The above-mentioned assembled semi-finished product is placed in another assembly jig, another electrode assembly B is placed on the separator 100, the other side of the separator 100 is contacted with the membrane of the electrode assembly B, then another aluminum plastic film (i.e., the second case 300 in the foregoing embodiment) with a thickness of 90 μm formed by punching pit is covered on the electrode assembly B with pit facing downward, and then the two aluminum plastic films and the separator 100 are heat-sealed together by adopting a hot-pressing mode, so that the electrode assembly a and the electrode assembly B are separated by the separator 100, and an assembled electrode assembly is obtained.

Liquid filling package

Electrolyte is respectively injected into the two cavities of the assembled electrode assemblies and then is packaged, the lugs 410 of the two electrode assemblies are led out of the outer package, the positive electrode lug 410 of the electrode assembly A and the negative electrode lug 410 of the electrode assembly B are welded together, and serial connection conduction between the two electrode assemblies is realized.

Example 2

The difference from example 1 is that in the production of the separator 100, the intermediate layer is selected from PET (polyethylene terephthalate) having a thickness of 30 μm, and the thickness of the encapsulation layer PP is 20 μm, otherwise the same as in example 1.

Example 3

The difference from example 1 is that in the production of the separator 100, the intermediate layer is selected from PET (polyethylene terephthalate) having a thickness of 40 μm, and the other is the same as in example 1.

Example 4

The difference from example 1 is that in the preparation of the separator 100, the intermediate layer is selected from an Al layer having a thickness of 25 μm, and the other is the same as example 1.

Example 5

The difference from example 1 is that in the production of the separator 100, the intermediate layer is selected from an Al layer having a thickness of 20 μm, and the thickness of the encapsulation layer PP is 24 μm, otherwise the same as in example 1.

Example 6

The difference from example 1 is that in the production of the separator 100, the intermediate layer is selected from an Al layer having a thickness of 22 μm, and the other is the same as in example 1.

Example 7

The difference from example 1 is that in the preparation of the separator 100, the intermediate layer is selected from an Al layer having a thickness of 24 μm, and the thickness of the encapsulation layer PP is 32 μm, otherwise the same as in example 1.

Example 8

The difference from example 1 is that in the preparation of the separator 100, the intermediate layer is selected from an Al layer having a thickness of 23 μm, and the thickness of the encapsulation layer PP is 35 μm, otherwise the same as in example 1.

Example 9

The difference from example 1 is that in the production of the separator 100, the intermediate layer is selected from an Al layer having a thickness of 26 μm, and the thickness of the encapsulation layer PP is 38 μm, otherwise the same as in example 1.

Example 10

The difference from example 1 is that in the preparation of the separator 100, the intermediate layer is selected from an Al layer having a thickness of 27 μm, and the thickness of the encapsulation layer PP is 34 μm, otherwise the same as in example 1.

Example 11

The difference from example 1 is that in the preparation of the separator 100, the intermediate layer is selected from an Al layer having a thickness of 28 μm, and the thickness of the encapsulation layer PP is 32 μm, otherwise the same as in example 1.

Example 12

The difference from example 1 is that in the preparation of the separator 100, the intermediate layer is selected from an Al layer having a thickness of 25 μm, and the thickness of the encapsulation layer PP is 25 μm, otherwise the same as in example 1.

Example 13

Example 14

The difference from example 1 is that in the preparation of the separator 100, the intermediate layer is selected from an Al layer having a thickness of 20 μm, and the other is the same as example 1.

Example 15

The difference from example 1 is that in the preparation of the separator 100, the intermediate layer is selected from an Al layer having a thickness of 25 μm, and the thickness of the encapsulation layer PP is 20 μm, otherwise the same as in example 1.

Example 16

The difference from example 1 is that in the preparation of the separator 100, the intermediate layer is selected from an Al layer having a thickness of 14 μm, and the thickness of the encapsulation layer PP is 22 μm, otherwise the same as in example 1.

Example 17

The difference from example 1 is that in the preparation of the separator 100, the intermediate layer is selected from an Al layer having a thickness of 20 μm, and the thickness of the encapsulation layer PP is 30 μm, otherwise the same as in example 1.

Comparative example 1

The difference from example 1 is that in the preparation of the separator 100, the intermediate layer is selected from an Al layer having a thickness of 12 μm, and the thickness of the encapsulation layer PP is 20 μm, otherwise the same as in example 1.

Comparative example 2

The difference from example 1 is that in the preparation of the separator 100, the intermediate layer is selected from an Al layer having a thickness of 10 μm, and the thickness of the encapsulation layer PP is 15 μm, otherwise the same as in example 1.

Test of adhesive Strength F

Taking a sample of the packaging area with the width W ₁ (for example, W ₁ can take 8 mm), adopting a multifunctional tensile tester, clamping materials on two sides of the packaging area by a clamp, taking the tensile speed to be 50mm/min, and testing to obtain the peeling tensile force P ₁, wherein the bonding strength F=P ₁/W ₁. For example, when the adhesive strength F between the first seal area 610 and the first area 620 is measured, the first seal portion 600 with the width W ₁ may be cut, the first case 200 and the separator 100 are respectively clamped by a multifunctional tensile tester, and the two are stretched at a speed of 50mm/min to obtain a tensile force P ₁ for stripping the two, so that the adhesive strength f=p ₁/W ₁ between the first seal area 610 and the first area 620.

Testing of tensile Strength f and elongation S

Taking a sample of the spacer 100 with the width W ₂ (for example, W ₂ can take 15 mm), clamping two ends of the sample by using a multifunctional tensile tester and a clamp, wherein the initial length of the spacer between the clamps is K, the stretching speed is 50mm/min, testing is carried out, when the spacer 100 is broken, a breaking tensile value P ₂ and a maximum stretching length L are obtained, and the tensile strength f=P ₂/W ₂; stretch ratio s= (L-K)/K.

Seal portion structural stability test

And respectively performing bending test on the seal parts at two sides, namely, bending the seal part towards the upper half part of the side wall of the shell body part by taking the boundary between the seal part and the shell body part as an axis until the seal part is attached to the upper half part of the side wall, and marking as one bending. And then reversely bending 180 degrees, and attaching the two parts to the lower half part of the side wall, namely, secondary bending. The above steps are repeated, the seal portion on one side is repeatedly bent 100 times, and the seal portion on the other side is repeatedly bent 200 times. Disassembling the battery, observing whether cracks appear at the joint of the isolating piece of the sealing parts at the two sides and the shell, and defining the following three states: ① If the crack length is more than 10% of the seal length, the seal is defined as a serious crack; ② If the ratio of the crack length to the seal length is greater than 0% and less than 10%, the crack is defined as a slight crack; and ③ are crack-free.

Table 1 shows parameters of the spacers and structural stability of the seal portions in each of the examples and comparative examples.

TABLE 1

As shown in table 1, in comparative examples 1 and 2, since F/(f×s) is greater than 15, the seal portion is inferior in structural stability, and serious cracks are generated. And in the examples 1-17 which satisfy F/(fXS) less than or equal to 15, severe cracks do not appear in the seal part of the corresponding battery, and the structural stability of the seal part is good. This is because, on the one hand, the separator itself has sufficient tensile strength and ductility to buffer stress and strain at the bending portion, and at the same time, the bonding strength between the separator and the case can withstand the stress at the bending portion, thereby avoiding the occurrence of a fracture condition, so that the first seal portion has excellent structural reliability. In addition, in the case where a plurality of spacers are present, as shown in examples 14 to 17, f.gtoreq.1+0.1n, and/or s.gtoreq.8+n% are satisfied, the structural reliability of the seal portion can be ensured.

Further, as is clear from the comparison of examples 1 to 10 and examples 11 to 13, the thickness variation coefficient CV of the seal portion is further satisfied to 5% or less, and the structural reliability of the seal portion of the corresponding battery is further improved. This is because, by making the thickness variation coefficient CV at both ends and the middle in the longitudinal direction of the seal portion 5% or less, when it is folded in the longitudinal direction, the stress at each place is more balanced, the risk of local cracking due to local overstress is reduced, and the structural reliability of the seal portion is further improved.

It should be noted that while the present application has been illustrated in the drawings and described in connection with the preferred embodiments thereof, it is to be understood that the application may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein, but are to be construed as providing a full breadth of the disclosure. The above-described features are further combined with each other to form various embodiments not listed above, and are considered to be the scope of the present application described in the specification; further, modifications and variations of the present application may be apparent to those skilled in the art in light of the foregoing teachings, and all such modifications and variations are intended to be included within the scope of this application as defined in the appended claims.

Claims

An electrochemical device comprising a first case, a second case, and a separator between the first case and the second case;

The electrochemical device includes a first sealing part, the first case includes a first sealing region located at the first sealing part, the second case includes a second sealing region located at the first sealing part, and the separator includes a first region located between the first sealing region and the second sealing region;

The bonding strength between the first seal area and the first area is F N/mm, the tensile strength of the separator is F N/mm, and the tensile rate of the separator is S, so that F/(F multiplied by S) is less than or equal to 15.
The electrochemical device according to claim 1, wherein at least one of the following conditions (1) to (4) is satisfied:

(1)1≤F/(f×S)≤10；

(2)F≥1；

(3)f≥1；

(4)S≥9％。
The electrochemical device according to claim 1, wherein the number of the separators is n, n is 1 or more, and the electrochemical device satisfies at least one of the following conditions (5) to (6):

(5)f≥(1+0.1n)；

(6)S≥(8+n)％。
the electrochemical device according to claim 1, wherein at least one of the following conditions (7) to (8) is satisfied:

(7) The thickness of the isolating piece is H mm, and H is less than or equal to 0.3;

(8) The first seal part comprises a first bending part.
The electrochemical device according to claim 1, wherein,

The length of the first sealing part is L, and the variation coefficient CV of the thicknesses of the two ends and the middle L/2 of the first sealing part is less than or equal to 5% along the length direction of the first sealing part.
The electrochemical device according to claim 4, wherein,

The first shell further comprises a first main body portion, the first bending portion comprises a first edge folding portion and a second edge folding portion, the first edge folding portion is connected with the first main body portion through the second edge folding portion, and the first edge folding portion is located between the first main body portion and the second edge folding portion.
The electrochemical device according to claim 1, wherein,

The electrochemical device further comprises a first electrode assembly and a second electrode assembly, a first cavity is arranged between the first shell and the separator, a second cavity is arranged between the second shell and the separator, the first electrode assembly is arranged in the first cavity, the second electrode assembly is arranged in the second cavity, and the first electrode assembly is connected with the second electrode assembly in series.
The electrochemical device according to claim 1, wherein,

The isolation piece comprises a first packaging layer, an intermediate layer and a second packaging layer, wherein the intermediate layer is positioned between the first packaging layer and the second packaging layer, and the materials of the first packaging layer and the second packaging layer comprise a first high polymer material; the material of the intermediate layer comprises at least one of a metal material, a second polymer material or a carbon material.
The electrochemical device according to claim 8, wherein,

The first high polymer material comprises polypropylene, anhydride modified polypropylene, polyethylene, ethylene propylene copolymer, polyvinyl chloride, polystyrene, polyether nitrile, polyurethane, polyamide, polyester, amorphous alpha-olefin copolymer or at least one of the derivatives thereof;

The metal material includes at least one of Ni, ti, cu, ag, au, pt, fe, co, cr, W, mo, al, mg, K, na, ca, sr, ba, si, ge, sb, pb, in, zn, stainless steel (SUS), and a composition or alloy thereof;

The second high polymer material comprises polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polyether ether ketone, polyimide, polyamide, polyethylene glycol, polyamide imide, polycarbonate, cyclic polyolefin, polyphenylene sulfide, polyvinyl acetate, polytetrafluoroethylene, polymethylene naphthalene, polyvinylidene fluoride, polypropylene carbonate, poly (vinylidene fluoride-hexafluoropropylene), poly (vinylidene fluoride-co-chlorotrifluoroethylene), organosilicon, vinylon, polypropylene, anhydride modified polypropylene, polyethylene, ethylene propylene copolymer, polyvinyl chloride, polystyrene, polyether nitrile, polyurethane, polyphenylene oxide, polyester, polysulfone, amorphous alpha-olefin copolymer or at least one of the derivatives thereof;

The carbon material includes at least one of a carbon felt, a carbon film, carbon black, acetylene black, fullerenes, conductive graphite film, or graphene film.
An electronic device comprising the electrochemical device of any one of claims 1-9.